Friday, December 30, 2011

Second Storm Will Blast Star Valley Early Saturday

The second of two storms will bring an end to the brief respite from the cold of December.  One system brought significant precipitation to the western Wyoming mountains and valleys early Thursday.  Due to the unseasonably warm air accompanying the system, Star Valley experienced more rain than snow with little accumulation on the valley floor.  While total precipitation, as measured by the weather stations in the valley, ranged upwards of half an inch, only a inch or two of wet snow was observed.  This was not the case in higher elevations above about 7000 feet with around a foot observed in parts of the Wyoming Range and from 1-2 feet in the Tetons.  The following chart was produced by Riverton WFO showing the observed snowfall from the first storm.

Very strong winds were observed across the high country, with Mt Coffin in the Wyoming range reporting gusts to 134 mph Thursday morning.

Warm air continued to cover the area through Friday with afternoon temperatures  into the mid 40s under quite a bit of late December sunshine. 

Storm number 2 now moving through the Pacific Northwest will bring an end to the brief respite from winter cold.  Rain and snow will spread across Star Valley, beginning later Friday evening, becoming all snow after midnight.  The cold front will arrive prior to sunrise accompanied by strong, gusty winds and 2-3 hours of moderate to heavy snow.  The snow should decrease to showers/flurries by later Saturday morning, however. cold air will drop temperatures to well below freezing during the afternoon.  Given the rapid movement of the storms, snow totals should generally range from 3-6 inches with the greatest potential in the northern portion of the valley. 

High pressure then builds into the area by New Years Day and will dominate into the middle of the first week of the New Year.  This returns Star Valley to weather experienced much of December, cold nights with sunshine most days.  Overnight temperatures will drop below zero in colder valley locations, then struggle to reach the teens during the afternoon, given the low sun angle this time or year.

The next chance of significant snow should not occur until after midweek.

Monday, December 26, 2011

Snows Coming

The advertised pattern change is underway as the storm track which has bypassed Star Valley much of December will be providing a snowy end to the year.  As can be seen on this evenings water vapor imagery a moist westerly jet is moving eastward across the eastern Pacific toward the Pacific Northwest.
Water Vapor Imagery Monday Evening 12/26/2011
The effects will be noticed beginning with increasing cloud cover  holding temperatures well above the zero readings experienced much of the nights this month in Star Valley. Precipitation in the form of snow will commence during the daylight hours Wednesday  It appears that intensities will pick up by Wednesday night and continue through Thursday and possibly Friday.    Temperatures will warm to near and possibly slightly above freezing in Star Valley by Thursday.  While precipitation will likely remain as snow, the warmer air mass should lead to a much wetter snow than that experienced so far this month.   The Riverton Weather Forecast Office has indicated over a foot can be expected in the nearby mountains and possibly 6-12 inches in Star Valley with the heaviest amounts from Thayne to Alpine.
Snowfall forecast 12/28-29 2011

 With the strong westerly winds, the snow will fall mainly over and west of the mountains of Western Wyoming. Downslope flow will result in little snow over much of central and eastern portions of the state, however winds will be strong and gusty.

The greatest amounts are likely over and west of the Tetons where by this weekend, new snowfall could be measured in feet, possibly up to 2-3.

The month long stretch of below freezing days could come to an end at Thayne E.S. during the next couple of days.

Friday, December 23, 2011

Cold, Clear Christmas Weekend, Followed by Moderation and Increasing Snow Potential

A couple more cold nights this Christmas weekend, then Star Valley will see a change in the weather pattern the last week of 2011.  As an illustration of how cold a month it has been thus far, Thayne Elementary has dropped below zero on 18 of the first 23 days of December, hitting a low of -15 on Friday morning. At the official observing site in Afton it dipped to -17 Friday morning with the temperature only rising to 3 above on a sunny afternoon.  The strong inversion which has been dominant much of the month was very pronounced again on Friday. As an example Star Valley Ranch reached a high of 20 above around 10am. However the cold air over the valley deepened dropping the temperature to under 10 above by noon where it remained the rest of the afternoon.

 Across the Salt Range at the Box Y Ranch after a morning low of 5 below the afternoon maximum was 27 above.  The inversion in the narrow Grays River Valley is typically weaker than over the Salt and the mid winter sun can still provide good warming.

High pressure will assure Star Valley if not still cold, a beautifully clear Christmas weekend.  With the fresh 2-3 inches of snow on Thursday, a White Christmas will prevail.

The expected major pattern change still looks on schedule for the final week of 2011.  The storm track along with a moist westerly flow off the Pacific Ocean will become an increasing factor through next week.  If nothing else the cold nights should come to an end by mid-week if not before as clouds provide a blanket over the valley. 

300 mb Forecast Thursday Evening 12/29 2011

 While the core of the strong polar jet should remain somewhat north of Star Valley, the moist westerly flow should provide periods of snow in the mountains and some snow or even rain in the valleys beginning mid week.

The model forecast of precipitation  for this next week through Thursday suggest potential for significant snowfall in the mountains of Northwestern Wyoming, possibly as far south as Star Valley.
Model forecasted Precipitation Through Thursday evening 12/29/11

Tuesday, December 20, 2011

Fast Moving Storm to Affect Star Valley Wednesday followed by a Cold but Snow-Free Christmas Weekend.

A fast moving upper level low pressure trough located over southern British Columbia Tuesday evening is expected to move quickly southeastward and provide a temporary return to winter weather over Star Valley on Wednesday.  The water vapor imagery below shows not only this trough but a weaker one over Northern Baja California

Water Vapor Imagery Tuesday evening 12/20/11

This system will strengthen as it moves across southeast Idaho and western Wyoming during the day on Wednesday.  Snow is expected to begin during the morning and as the system continues on  southeast to Utah and Colorado, the snow will end from the north by Wednesday evening. The Riverton Weather Forecast Office has created a graphic with the expected associated snowfall amounts by Wednesday Night.
The greatest totals are expected in the higher elevations with 1-3 inches in Star Valley. 

High pressure then provides a return to the conditions that have been experienced through much of December.  Cold nights, with temperatures generally below zero, will prevail into the Christmas weekend. Minimums could  possibly dip to 10-15 below by Thursday morning in coldest valley locations. It still appears that from Thursday until Christmas Day fair conditions will prevail with the potential for mostly sunny days.

However, the longer range models are now indicating that the high pressure that has been protecting Wyoming from storms much of December will be weakening next week.  The jetstream is now forecast to start tracking from the Pacific eastward across Wyoming.

300 mb(30,000 ft) Forecast Tuesday 12/27/11
This change in pattern, if it materializes, will result in a more active pattern across Star Valley.  Since it is almost a week away, the model predictability limitations preclude specifics at this time- although the snow potential could increase substantially in the last week of 2011.

Saturday, December 17, 2011

December to Remain Abnormally Dry

Persistent high pressure has been parked over the Star Valley area much of December.  Result has been minimal amounts of snow and rather cold temperatures. It appears now that high pressure will be around at least through Christmas Weekend.  The latest model forecast indicates that pressures will be  above normal over the eastern Pacific Ocean, which will in turn force the storm track far to the north into Western Canada. This graphic is centered on Christmas Day.

Christmas Day Height Anomaly 500 mb
Red indicates above normal heights, blue below
There will be a low pressure trough that will be passing off to the northeast of Star Valley on Wednesday, Some  snow is possible with this system, but again amounts should be generally light.

500 mb forecast Wednesday December 21 2011

The longer range forecast through the remainder of the month do not hold out much hope for a significant snow storm the rest of 2011. While travelers will favor this outcome, skiers will not be pleased.
8-14 Day Outlook Precipitation Valid Dec 25-31 2011
The strong temperature inversion across the valley much of December is likely to persist.  This will keep nights cold, near or below zero, and afternoon highs not likely reaching freezing.  At Thayne Elementary the high so far this month has only been 26.

Thursday, December 15, 2011

Cold But Little Snow First Half Of December

So far December 2011 has been cold with little in the way of significant snow across Star Valley.  Both Thayne and Etna Elementary School Weather Stations have now been providing reliable weather data since the fall of 2010. Following are data from the school stations.

Thayne                   Avg Max Avg Min 
Dec 1-15 2011            19               -3
Dec 2010                    31              14
Jan   2011                   26                6
Feb  2011                    27               5

Etna                        Avg Max   Avg Min
Dec 1-15 2011             20                  0
Dec 2010                     31                15
Jan 2011                      26                  7
Feb 2011                     28                  5

The first 15 days of December's averages, thus far, are much colder than December 2010 as well as the normal temperatures for the month at the Beford Climatological station with a maximum of 28 and minimum of 6. Additionally, both stations are well below those observed last January and February.

The coldest morning so far this month was the 6th when Thayne dipped to -14 and Etna -10.  Minimums at Thayne ES have been below zero 12 mornings so far this month.

While still cold, the Star Valley Ranch station has  recorded average maximum/minimums of 26 and 7 thus far in December. The only morning below zero was on the 6th when it dipped to -4.

A strong temperature inversion has been in place much of the month which typically keeps the valley floor much colder than higher elevations.  Thus the higher readings at Star Valley Ranch which is 300-400 feet above the adjacent valley floor.

While the early Fall started out with several significant snows, high pressure has dominated across Star Valley so far in December with the storms tracking both north and south of much of southeast Idaho and Wyoming.

Snowfall so far this month at Star Valley Ranch has totaled just 7 inches, while the station south of Smoot has had just 8 inches.   The average snow for the month of December at the Bedford Climate station is over 30 inches.  Storms are expected to continue bypassing Star Valley for the next several days, so any appreciable snow is unlikely.  With the early fall storms the snow totals since Oct 1st are 58 inches  at Star Valley Ranch and 61 inches at the station south of Smoot.

Sunday, December 11, 2011

Pattern Change Over The Western States

A significant change in the storm track is taking place over the Western States for the coming week.  Star  Valley has been protected from storms for much of December by high pressure.  While the skies have been generally clear the valley temperature inversions have been pronounced,. In Star Valley this has resulted in continued cold conditions overnight with lows below zero and afternoon high remaining in the teens.,  In the Cokeville area afternoon highs have not climbed out of the single digits over the weekend. Not the case above the valley floor, as the station at Star Valley Ranch warmed into the middle 20s and reminded well above zero at night. And just to the east at the Box Y Ranch along the Greys River maximums have been near freezing.

The high pressure which has been protecting much of the west has broken down and a new storm track is being established well to the south of Star Valley across the desert southwest.By Monday evening a large low pressure center will have developed over Southern California.

300 mb Forecast Monday Evening 12/12/2011
 While this system will bring considerable precipitation, rain in the valleys and snow in the higher elevations of the Southwest, it will have minimal effects on Star Valley for the next few days. In fact the increase in clouds with the southwesterly flow ahead of the low will tend to lessen the strong overnight cooling allowing temperatures to generally remain above zero for much of the week.  Additionally afternoon highs will approach freezing even on the valley floor as warmer air mixes down with an increase in the winds aloft.

With regards to snow, chances will remain low until mid week. Additional disturbances will be moving inland at that time, however model forecasts continue to take most of the effects to the south of southeastern Idaho and western Wyoming. Some light snow will be possible most days after Wednesday but any major snow event seems unlikely through next weekend.

Wednesday, December 7, 2011

Strong Temperature Inversions and High Pressure with Little Snow for the Next Week

High pressure has become well established over much of the Western U.S. and will dominate through the coming weekend. The storm track has shifted well to the north of Star Valley resulting in a rather stagnant weather pattern.  Strong inversions have developed in Star Valley under the generally clear and calm conditions and only limited daytime heating this time of year.   The results are that the coldest daytime temperatures are occurring on the valley floor with considerably warmer readings above the inversion in the higher elevations.  As an example while the afternoon temperature in Afton was only able to rise to 10 above  Thursday, after a morning low of -9, it warmed to near freezing at Salt River Summit  at an elevation some 1500 feet above the valley floor after a morning low of plus 7.

Visual evidence of this strong temperature inversion can be seen, particularly around Afton at the top of the haze/smoke layer.

Once these inversions become established this time of year, they will require a breakdown of the current high pressure to increase the atmospheric mixing to remove them. The earliest this seems likely to occur will be early next week when a weakening upper trough of low pressure is forecasted to cross the area.  Until then expect plentiful daytime sunshine, but continued cold conditions in the Valley.  Warmer conditions will continue to be observed in higher elevations  where in some cases the morning lows will be higher than the adjacent valley afternoon highs.

Snow flurries are likely this Wednesday night as a weak disturbance passes across the area, however no accumulation is expected. The next chance of any significant snow appears to be no sooner than the middle of next week.

Monday, December 5, 2011

How Cold Was It?

Overnight cloud cover thinned/dissipated toward sunrise allowing a rapid temperature drop.  In the Lower Salt River Valley clouds hung around longer and as a result minimums were only near zero.  However, from about Thayne southward it cleared and was much colder.  Following are the observed minimums in the valley this morning.

Auburn                -17
Afton                   -13
Thayne ES           -8
Osmond ES          -8
Smoot                   -5
Etna ES               -1
Star Valley Ranch  2
Alpine                   3

Nearby it was:

Pixley south of Cokeville   -21
Driggs ID                         -17

Cokeville                          -15
Jackson Airport                -13

In other areas clouds were not a factor and as a result it was much colder.

Old Faithful             -33
West Yellowstone    -35

and the coldest was a -41 at the Peter Sink Site which is located just south of Logan Summit Utah west of Bear Lake.  This high elevation sheltered site is typically one of the coldest around.

Saturday, December 3, 2011

Bitter Cold Monday Morning

The cold northerly flow continues across Star Valley.  Fast moving disturbances embedded in the flow will bring periods of clouds and light snow.  One such system brought 1-2 inches Saturday night and another one is scheduled to drop southward and bring no more than an inch or two on Sunday.

Of more importance, this next system is going to be followed by very cold air, originating over Northwest Canada.  Although this is still not a true Arctic air mass as temperatures this morning over the Yukon  are generally above zero, the ingredients are coming into place to drop temperatures over Star Valley Sunday night to well below zero.  Skies should clear in the wake of Sundays system and the combination of  light winds and the cold air aloft will lead to ideal conditions for a very cold night.

It now appears that 10-15 below zero will be common in the valley locations by sunrise Monday, with the coldest locations dropping to 20 below or lower. The only areas that may be spared the extreme cold would be the communities above the valley floor such as Star Valley Ranch where it could go no lower than about 5 below.

Gradual moderation in temperatures will occur into the middle of the coming week, however they are expected to remain well below normal for the first week in December. The pattern remains unfavorable for a significant snowstorm in Star Valley, probably through the coming week.

Thursday, December 1, 2011

Star Valley to Have an Extended Period of Below Normal Temperatures with Little Snow

A major adjustment is taking place in the storm track/jet stream over a large portion of the U.S. and northeastern Pacific Ocean.  The latest storm to move from the Pacific is affecting the southwestern states Wednesday night, bringing very strong and damaging winds to some sections of California.

Western Wyoming is now dominated by a cold northerly flow of drier air from Canada.  As high pressure builds north into the Gulf of Alaska, this will put Star Valley  under an extended period of possibly more than a week of reinforcing surges of cold air from Canada.  With the storms tracking across western Canada and then southeastward...most of the snow will occur east of the Continental Divide.

This first chart shows the forecasted abnormally high pressure centered over the Gulf Of Alaska.  The red contours in the chart are areas of higher than normally 500 mb heights, with blue contours indicating areas of below normal 500 mb heights.

500 mb Anomalies Sat 12/3/11
The models suggest that this pattern will persist as shown on the following chart displaying  the same fields as the one above except for Wednesday of next week.

500 mb Anomalies Wed 12/7/11

This pattern will be characterized by only brief periods of clouds and light snow as disturbances pass through Star Valley. Much of the time for the next week will see only limited amounts of cloud cover allowing for nighttime temperatures to drop below zero, and afternoons remaining well below freezing.

Fortunately there is not a pool of Arctic air yet available in Canada, so even though the jet stream pattern will be favorable, a bitter cold air mass from the north is not expected at least into early next week.  If the pattern persists, then the possibility of an arctic air mass invading Wyoming will increase.

Nevertheless conditions will be favorable for colder valley locations dipping to 10 below zero or lower Friday morning under clear skies.

Tuesday, November 29, 2011

December will Begin Cold in Star Valley

A storm which can be seen with the water vapor imagery this evening over Vancouver Island  will be the big weather maker  over the interior west the next several days.
Water Vapor Imagery Tuesday evening 11/29/11

By Thursday morning this low is forecast to drop southward to the west of Wyoming into the desert Southwest.  The computer models  have been  consistently forecasting this scenario for the past several days.

500 mb Forecast Thursday morning 12/1/11 
Much colder air will then flow southward from Canada into Wyoming by Thursday in the strong north/northeast flow as the upper low heads toward Arizona.

This type of pattern with much of the upper low energy tracking west of Star Valley should limit the snow potential.  At this time a couple inches are probably all that can be expected to fall over the valley by Wednesday night. While strong northerly winds will spread across Wyoming and down the upper Snake River Valley by Thursday morning, Star Valley will  be protected by the Salt Range limiting both the wind and wind chill effect in contrast to other areas of Wyoming.An exception could be in the Alpine area where the Snake River Canyon will likely channel the stronger east winds.

As cold air pours southward Thursday, afternoon temperatures will struggle to reach 20 and by evening rapidly fall to near/below zero.  With skies clearing by Thursday night  below zero will be common with coldest Star Valley locations such as Auburn and Thayne could drop to 10-15 below.

While any additional snow other than flurries is unlikely, cold high pressure will dominate into next week.

The Riverton WFO has provided an excellent presentation how the incoming storm will effect Wyoming.  This can be seen at:

Monday, November 28, 2011

Star Valley Ranch Weather Station Now Corrected

The temperature at the Star Valley Ranch weather station which had been running about 12 degrees too cold since 11/23 is now displaying the correct reading.

Sunday, November 27, 2011

Other Than Wednesday, a Quiet Weather Week is in the Offing

Clouds began returning to the skies of Star Valley late Sunday afternoon.  Overall it was a cool but very sunny weekend.  Clouds are the forerunners of a rather weak disturbance which will be crossing mainly north of Star Valley tonight and Monday morning.  While there is the possibility of a few snow flurries  toward morning, the main effect of the clouds will be to provide an insulating blanket and keep overnight temperatures well above zero.

High pressure takes over again by Monday night leading to a very pleasant and generally sunny Tuesday.  The next storm of interest is expected to be much stronger and approach the Pacific Northwest states Tuesday from the Gulf of Alaska.  The following sequence of forecasted 500 mb Charts show the expected evolution of this system during the week.

Tuesday Evening
Wednesday Evening

Thursday Evening

If this model scenario verifies, which seems likely as several models are in close  agreement, then Wednesday will be the stormy day of  the coming workweek.  Colder but generally fair weather returns as high pressure moves in and the developing upper low that effects Star Valley on Wednesday settles southward into the desert Southwest. It  is still too early to determine the snow potential for Wednesday.

Friday, November 25, 2011

Very Strong Winds Friday, However Quiet Weather Ahead

As expected a fast moving trough of low pressure intensified as it crossed Western Wyoming Friday afternoon, producing some very strong winds and briefly near blizzard conditions.  Here is a list of strongest reported gusts Friday:

Mt. Coffin                   108 mph  (10,800 ft)
Jackson Hole Summit    72 mph  (10,300 ft)
Alpine                           51 mph
Star Valley Ranch          50 mph
Thayne                          42 mph

This evenings 300 mb analysis(30,000 ft) clearing shows the strongest jet stream crossing the area from the northwest where winds were in excess of 130 mph at its core.

300 mb (30,000 ft) Friday Evening Nov. 25 2011

While actual new snow in the valley was generally less than 2 inches, the strong winds produced briefly near blizzard conditions.

Rapid clearing has occurred this evening as high pressure spreads across the area. As the winds diminish temperatures are falling.  As of 9pm Thayne ES had already dipped to 7 above and by sunrise the coldest  Star Valley locations likely will be at least a couple degrees below zero.

High pressure will dominate for the next several days with the next threat of any significant precipitation not expected until at least next Wednesday, if then.   Here is a model depiction of the precipitation that is forecasted through next Tuesday.

GFS Model Forecasted Precipitation from Saturday until Tuesday.

Today's storm in Wyoming will become a big precipitation producer in the eastern U.S.  Heavy storms will continue to hammer the Pacific Northwest coast northward into Canada.  High pressure will protect our part of the country from any storm activity.

Thursday, November 24, 2011

Fast Moving Storm Friday, Followed By Several Dry Days.

Under mostly clear skies a strong inversion developed overnight across Star Valley.  Dramatic differences in temperatures were observed this morning.  Etna ES dipped to 13 and Afton 12.  However, in places like the forested areas of Star Valley Ranch and Salt River Summit, above the inversion,  low temperatures this morning were as much as 20 degrees warmer, barely dipping below freezing.

Warmer air has spread across Star Valley above the inversion on Thanksgiving Day.  Surface temperatures have risen into the 40s above the valley floor such as at Star Valley Ranch, even as clouds thicken ahead of the next Pacific storm. However, as of early afternoon Etna ES, below the inversion, has yet to reach freezing.   The next system currently in the Pacific Northwest will move rapidly eastward bringing  at least some snow across southeastern Idaho and western Wyoming beginning after midnight.  There could be brief moderate snow as the cold front crosses the area late tonight and Friday morning. The speed of  the system is expected to limit accumulations to no more than a couple inches in the Valley and somewhat greater amounts in the mountains, particularly the Tetons.

Rapid improvement  will occur by Friday afternoon as high pressure takes over.  This will lead to a dry weekend continuing into the middle of the coming work week.  The storm track shifts well to the north  assuring a quiet end to what has been a stormy November.

Comparison of GFS and ECMWF 500 mb Tuesday afternoon 11/29/11
While there are considerable differences in the model solutions Tuesday, both keep the storm track to the north of the Valley.  However, by late Wednesday/Thursday the ECMWF(European Model) suggests a return to stormy conditions while the GFS(Globel Model) keep the Valley high and dry.

Comparison of GFS and ECMWF 500 mb Wednesday afternoon 11/30/11

Wednesday, November 23, 2011

Star Valley Ranch Weather Station

The Star Valley Weather Station is running about 10 degrees too cold.  This will be corrected as soon as possible, but may not be until Monday as the Console is located in the Public Works building.

Tuesday, November 22, 2011

Pattern Change Leading to Drier end of November

Star Valley/Western Wyoming for the first three weeks of  November has been colder and wetter than  normal.  Over 3 feet of snow has fallen at Star Valley Ranch with a similar amount near Smoot  at the upper end of the valley.  The Numerical forecast  models are in agreement that the storm track which has been through this part of the country will be shifting back to the north the rest of the month. With the exception of a fast moving low pressure system that will move through late Thanksgiving day and Friday, it now appears that high pressure will be in control for the remainder of November.

Wednesday and Thanksgiving day will finally see temperatures rise to near or above normal. Afternoon highs will be warming to  40  or higher with more sunshine than in the past few days.  Friday will see a temporary return to cloudy with precipitation, likely in the form of snow.  At this time it appears that several inches are likely in the nearby mountains, but valley totals should be no more than a couple inches.

500 mb Forecast Friday afternoon Nov. 25 2011

High pressure quickly takes control over the weekend with the likelihood of mostly sunny and dry days.  With the clearing skies overnight temperatures will drop to single digits in the coldest valley locations.  Valley temperatures will be slow to warm given the low sun angle this time of year, with warmer temperatures in the higher elevations such as nearby ski areas.

500 mb Forecast Saturday Evening Nov. 26, 2011

With the jet stream and storm track well to the north early next week, fair conditions should dominate.  This time of year the substantial snow cover, under high pressure, will result in favorable conditions for overnight fog formation.  This could temper the amount of warming in the valleys, particularly if the fog fails to burn off in the afternoon.

Saturday, November 19, 2011

Storm Exits Star Valley-Thanksgiving Outlook Looks Good

The latest storm has cleared Star Valley but a cold and unstable air mass remains. Mostly light  snow showers will continue until this evening.  New snow across the valley ranged from 6-8 inches with 8 inches at Star Valley Ranch. Here is a map of the Snowfall totals for the storm produced by Riverton WFO.

Total Snowfall Nov. 17-19 2011

The current 500 MB analysis  shows the strong polar jet stream heading on to the east into the plains with a new jet approaching California
500 MB Analysis Saturday Morning 11/19/11

The greatest snowfall with this storm occurred over the mountains with  between one and two feet falling in the Tetons and about a foot over the Salt Range.

As we move toward Thanksgiving Day the storm track is forecast to shift to the south  of Star Valley with the next system now approaching the California coast .

500 MB Forecast Tuesday Morning 11/22/11
This system is weaker than the previous system that just moved across the area.  Much of the precipitation will pass well south of Star Valley as this trough of low pressure moves east into the Central Plains by Tuesday.

While another trough of low pressure will be moving onshore along the west coast by Thanksgiving day, the primary area of precipitation should again remain south and west of the valley.  Southwesterly flow across southeast Idaho/western Wyoming is likely to be rather mild but result in quite a bit of cloud cover along with chance of either rain or snow showers.

500 MB Forecast Thursday Morning 11/24/11

It now appears that any precipitation will have minimal impact on Thanksgiving travel in Southeast Idaho/Western Wyoming.

The graphic below is the forecast  of total precipitation for the 4-day period Monday to Thursday this coming week. It should be a wet period for much of the west coast, but only scattered light amounts over the interior west.

Total Forecasted Precipitation 5AM Mon -5AM Thu

Thursday, November 17, 2011


The major storm system is still on track to move eastward across southern Idaho into Western Wyoming. Light snow is beginning this morning in parts of the valley and will continue and increase during the day. It now appears that the potential for heavy snow with accumulations of 6-8 inches or more could occur in the valley before diminishing Friday night when the colder air arrives. The nearby mountain ranges will likely receive well over a foot. Even greater amounts of snow, possibly upwards of 2 feet by Saturday morning will fall over the Teton Range and southwestern portions of Yellowstone National Park.

Given the nearly 2 day duration of snow the total depth is expected, as mentioned, to be substantial. Temperatures will remain near freezing in the valley until the strong cold front arrives later on Friday. With the front will come gusty winds and temperatures falling into the teens, with deteriorating driving conditions in the valley and all roads out of the area.

The weekend still appears to be cold, however significant snowfall should be over.

Tuesday, November 15, 2011


Wednesday will be another fairly quiet day weatherwise across Star Valley with still a chance of snow flurries similar to Tuesday.  Big changes will be underway by early Thursday. A disturbance will be moving across the Pacific Northwest Wednesday and spread increasing precipitation across Star Valley beginning by Thursday morning. The 300 MB forecasted  winds for Thursday morning show the strong jet stream heading toward Idaho and Western Wyoming.


Temperatures with this  system will remain near freezing in the valley, favorable for a rather wet snow. There could be several inches fall in the valley by Thursday night/Friday morning and higher amounts in the nearby mountains. 

On Friday a very cold upper level trough of low pressure moves eastward from the Pacific Northwest states, which not only will continue periods of snow, possibly heavy in the mountains, but spread the coldest air yet this Fall across Star Valley.  The coldest air will arrive Friday night and by Saturday temperatures will remain in the low to mid 20s in the valley throughout the day.

By Saturday evening the strong jet stream and upper system will have moved rapidly on to the east of western Wyoming, leaving Star Valley under a very cold air mass which will end any significant snow threat.  Dependent on the amount of clearing that occurs, below zero temperatures are possible Sunday morning, at least in the typically coldest valley locations nearer the Salt River such as Auburn, Thayne and Etna.

Looking ahead to the first of the coming work week, it looks like high pressure will dominate with still cold nighttime temperatures, possibly below zero, and a slow climb in afternoon readings.  However there is potential for fog forming in the valley which would limit the heating potential in the afternoon.

Monday, November 14, 2011


The Climate link on is to the data from the official climatological station located just southeast of Bedford WY.  The record for this site goes back to 1975 with very few missed observations. At this time just the current month data will be available from but plans are to eventually make the site more robust. The link to the official station data can be found at

Sunday, November 13, 2011


Snowfall Totals in inches Nov 12-13 2011
As shown on this graphic from WFO Riverton large amounts of snow fell across all of Star Valley from early Saturday morning until Sunday afternoon.  The greatest total observed was 19 inches at Star Valley Ranch followed by the 15 inches at the weather station just south of Smoot, 14 inches in Thayne and 12 inches in Alpine.

The snowfall resulted from two fast moving systems  across Western Wyoming.The first included considerable wind at higher elevations Saturday morning.  There was temporary afternoon clearing as seen from this photo in Star Valley Ranch.

At the same location on the Ranch this picture was taken Sunday morning  where an additional 10 inches had fallen overnight!

  The pattern that has resulted in this sudden change over the weekend is still in place as can be seen on this evenings water vapor imagery.

Water Vapor Image Sunday Evening  Nov 13 2011

A broad area of moisture extends from the  Gulf of Alaska southeastward across the Pacific Northwest and pointed toward western Wyoming.  What this implies is that while the snow has generally stopped across Star Valley Sunday evening, additional fast moving but somewhat weaker upper disturbances while continue the potential for periods of generally light snow into Tuesday.  Another 1 or 2 inches is possible but it appears that another bout of heavy snow seems unlikely.

By Wednesday high pressure will temporarily diminish or end any snowfall threat. It does appear that a major change in the large scale weather pattern will take place by the end of the work week increasing the potential for another significant storm affecting Star Valley/western Wyoming.

500 MB Forecast Saturday Nov. 19 2011
This is a model forecast depicting the development of a large scale upper level low pressure trough across much of the Western States.  Since it is still 5-6 days away, the reliability of these forecasts are somewhat limited but there is sufficient confidence to expect  the threat of winter weather conditions across much of the area from the Rockies westward including Star Valley.

Thursday, November 10, 2011

Big Changes this Weekend Continuing into Next Week

500 MB Noon Saturday 11/12/2011
After one more day on Friday of cool but pleasant weather, a fast moving storm will sweep across Star Valley Saturday morning.  This system is a spin off from the massive storm that slammed Western Alaska Wednesday.  It was one of most powerful storms in that part of Alaska in the past 40 years.  The system which will move from the Gulf of Alaska southeastward into the Pacific Northwest early Friday will bring a strong cold front across the southeastern Idaho/western Wyoming area Saturday morning.

Snow levels will quickly drop to the valley floor  Saturday morning with heavy snow for a couple hours with and just behind the front.  The strong westerly flow will lead to the greatest snowfall along the north-south mountain ranges including the Salt  and Tetons.  Snowfall amounts will be greatest north of the Snake River with 4-8 inches in the mountains.  It appears that 2-4 inches will be possible across Star Valley. Gusty winds will accompany the front and combined with the snow could lead to adverse traveling conditions, particularly across Teton Pass.

While the storm system will be moving quickly to east of the Valley by Saturday afternoon, a strong west to north flow will support an extended period of extensive cloud cover and periods of snow.  By the middle of  next week substantial amounts of snow could have accumulated in the mountains. and possibly in Star Valley as well.

Sunday, November 6, 2011

Storm Track Remains To The South

250 MB  39,000 feet Monday Oct 31 2011
250 MB  39,000 feet Sunday Nov 6 2011
A dramatic change in the jet stream and storm track took place this past week across much of the United States.  Storms which were moving from well north of Star Valley then southeastward into the Central U.S. are currently moving across the desert southwest with only limited effects this far north.

It has been a seasonably cold and winter like weekend across the Valley with snow amounts ranging generally from 3-5 inches with the greatest two day total of 6 inches at Star Valley Ranch.

The pattern for this coming week will favor dry and generally fair weather as high pressure develops eastward across the western states.  Again the jet stream will shift southward toward the weekend and bring the primary storminess to California and the desert southwest.

Forecasted 250 MB 39,000 feet Friday Nov 11 2011
 Cloudiness over the weekend should be diminishing Monday, leading to at least some sunshine by afternoon.  More sunshine is likely from Tuesday into Thursday as high pressure dominates the intermountain region.  However with little wind at least until toward the weekend, nighttime temperatures will be quite cold, particularly with the limited cloud cover.  Some of the colder valley locations will likely drop to the high single digits, possibly as early as Tuesday morning. The low sun angle and snow cover will limit the amount of daytime heating with afternoons remaining near freezing at least through Wednesday.  As a result it could be even colder Wednesday morning with near zero possible in coldest spots.

Later in the week warmer air will begin to spread across the area leading to afternoon highs possibly into the 40s.  Snow chances appear limited until the weekend when the storm off California begins to move eastward into the desert southwest. Again as occurred this weekend, it appears that the greater impact should remain well south of Star Valley.

ABOUT is the combined creation of three Johns.  While the idea began with me,  John (Jack) Hales a retired Severe Storms Forecaster who now resides in Star Valley Ranch,  the actual development of the web page was the work of John Hart(current Severe Storms Forecaster in Norman OK at the Storm Prediction Center and John Hales the son of Jack who does web development for a living and resides in the Phoenix AZ area.

Questions or comments can be directed to Jack at

The primary goal of the web page is to provide the residents of Star Valley and its surroundings, along with any visitors or interested persons, one stop shopping for all the weather information they may need for a myriad of purposes.

Star Valley, due to its location with respect to several mountain ranges and in the path of many of the storms that cross the country along with its rather high elevation, poses a real challenge to anyone attempting to forecast its weather.

Knowing that I (Jack Hales) would be retiring to a home we built in Star Valley Ranch, and with a life long passion for the understanding of weather, I was able to aid in the establishment of three weather stations in Star Valley in 2010.  They are located at  Thayne and Etna Elementary schools as well as in the Town of Star Valley Ranch.  They have provided more or less a continuous weather record since the Fall of 2010. The stations are built by Davis Instruments and have been and continue to provide their data online.
A primary purpose of the weather stations at the schools is to stimulate student interest in not only weather, but science in general.  The school stations were funded by the Student Loan Fund of Idaho.  All Three stations observe temperature, humidity, winds, pressure and both frozen and liquid precipitation.  The Thayne Station has additional sensors that measure soil temperature and moisture at three depths:  just below the surface, 2 feet and 4 feet deep. The Thayne station also measures both solar insolation and UV levels.

There are several links on the Home Page pointing to areas of interest with regards to Star Valley Weather.  The Weather Cameras Link is unique and has been under development by my son, John Hales for the past three years.  There is a link on the many capabilities the site has with regards to viewing a large number of live web cams not only in the Star Valley, Western Wyoming area but many other regions as well.  You are referred to the link for directions on how to use the site.

There are links to weather information including not only forecasts issued from the Weather Forecast Office in Riverton, WY but other types of more numerically derived prognostic tools.  Also available are both radar and satellite data and surface observations.
One other area of interest is my weather blog.  The blog will evolve with time.  But the primary goal is to focus on weather forecasting and observing in and around Star Valley WY.  It will provide a means of enhancing the flow of weather info, particularly during periods of  hazardous conditions both winter and otherwise.

Monday, October 31, 2011

Changes in the Wind for Star Valley

This coming week will see a changing weather pattern as the storm track shifts southward over the Western U.S.  The first storm will be be sending a cold front across Star Valley today accompanied by some precipitation...particularly along and over the mountains.  Precipitation should initially be in the form of rain in the valley, but the snow level should drop to the valley floor by this evening.  Once the cold front moves onto the east, the accompanying upper trough of low pressure will be intensifying as it moves across western Wyoming overnight.  This will continue at least some light snow over the valley through the night with several inches likely falling in the higher elevations of the Salt and Wyoming Ranges.

Even though it will be intensifying, the upper trough should move east of the valley, by mid day Tuesday with a diminishing snow threat and some clearing by afternoon.  The colder air will keep temperatures in the valley in the 30s all day.  Tuesday night high pressure and clearing skies will allow temperatures to drop into the teens.

After a cool but generally fair Wednesday and much of Thursday, a much stronger storm will be developing into the western states by later Thursday.  This storm will spread a much larger area of precipitation in the form of snow across much of the northern Intermountain region including Star Valley.  Heavy snow is likely with this system but at this time the primary threat area is still uncertain.  It is possible it will move far enough to the south to place the area of heavy snow across northern Utah or even further south.  However it is quite likely that at least a few inches could occur in Star Valley beginning late Thursday into Friday.  This storm will be followed by even colder air that the one now approaching and Saturday morning could see single digits in the coldest valley locations if skies clear sufficiently.

Saturday, October 29, 2011

Winter Weather Is In Sight

Since the early season heavy snow 3 weeks ago, the pattern for Star Valley has been generally dominated by high pressure and little in the way of active weather. In the wake of the  storm system earlier this week that ushered in the coldest air of the fall, the pattern into the first of the week will be controlled by a storm track remaining north of Star Valley.

However the longer range forecast models are now indicating a major change to the jet stream location  by the middle of the coming week.  Initially a trough of low pressure  will move through the Great Basin by later Tuesday with most of the precipitation moving through Nevada into Utah to the south of  Star Valley.  Then by Thursday a fair but cool day will prevail.  The longer range forecast models are now indicating a much stronger and potentially significant Winter Like Storm will develop across southern Idaho/Nevada into Utah by early Friday.  This storm has the potential for spreading widespread snow to the valley floors...including the lower elevations of Idaho and Northern Utah during the day Friday, impacting travel conditions in most routes out of Star Valley

Wednesday, October 26, 2011

Cold Air Arrives on Schedule

A cold  front moved across Star Valley early Tuesday as expected with little in the way of precipitation.  The only measurable was .01 at Star Valley Ranch early Tuesday morning.  However there was some snow in the Salt Range as both Willow Creek and Cottonwood Creek Snotel sites recorded about .10 in the form of snow which was visible on the Osmond ES Cam Tuesday morning above about 7500 feet.

Under clear skies and calm winds temperatures this morning dropped to the coldest of the fall.  The lowest reported in the valley was at both Etna ES and Thayne ES with 14 and Star Valley Ranch was the warmest at 19.

While the cold front was generally dry in far Western Wyoming, significant snow has fallen in the east.  As of this morning there has been as much as 9 inches reported in the Cheyenne area.

A generally fair weather pattern will set in across Star Valley the next several days. While nights will continue seasonably cold, daytime temperatures will slowly moderate.  By Friday afternoon will be back into the 50s and likely change little into the coming week.  Little in the way of precipitation is now expected at least through the weekend.

Sunday, October 23, 2011

Indian Summer Comes to an End Tuesday In Star Valley

After another unseasonably warm late October Day on Monday across  Star Valley a cold front crossing the Valley Monday night will usher in a markedly cooler air mass on Tuesday.  Daytime temperatures on Monday in the 50s  will have a difficult time of rising above the low 40s  Tuesday and remain in the 30s much of  Wednesday. Most of the rain and snow with this system will likely remain to the north of Star Valley, however some light/snow could occur early Tuesday behind the cold front, most likely from the Narrows north as the cold front moves through.   Any accumulation would likely be confined to the higher Salt and Wyoming Ranges, and even then only amount to an inch or so.

The greatest effect will be the colder air, officially ending the growing season across all of the Valley. By Wednesday morning the coldest regions of the valley will drop into the teens and well below freezing even in the typically milder locations such as Star Valley Ranch.

Later in the week high pressure will provide generally dry but cool conditions with a slow daytime warming trend.

Saturday, October 15, 2011


The  FORECAST Section contains not only the latest Star Valley Zone Forecast produced by the Riverton WFO but the AFD(area forecast discussion) which is a meteorological reasoning that the forecast was based on.  The Zone forecast is updated by the Riverton WFO as needed.

There is much more to the FORECAST Section than the products issued by Riverton WFO. Below the  AFD is the latest 72 hour MOS(model output statistics) produced by the GFS(global forecast system) model. Jackson (JAC) is the closet site to Star Valley that the MOS forecast is produced. Additionally an extended GFSX MOS Forecast that extends out for 7 days is also included for JAC.

On the right side of the FORECAST page  from top to bottom are:

--Current Visible satellite loop centered over the Northern Intermountain region. The loop is 2 plus hours long.

--Composite radar imagery loop.  Left clicking on the loop will bring up the latest image overlaid with surface plots.

--Loop of PIH WSR-88D  reflectivity  image.  Loop is around 45 minutes in length.  Left clicking on the loop will bring up the complete radar menu among other options permitting the access of other radars.

--The most powerful diagnostic section available on the Star Valley Weather Page.  Left clicking accesses the Storm Prediction Center(SPC)  Hourly Mesoscale Analysis.  There is a myriad of choices in selecting diagnostic fields which can be used forecasting not only convection including severe thunderstorms, but winter and fire weather conditions..  There is extensive helps  built into the page. Also any questions I will be glad to try and provide an answer through the comment section.

While the area is centered over the Northwestern portion of the CONUS, it can be shifted to other  areas  along with a National area as well.

--This is the sounding section.  Left clicking on the map of available soundings will by default bring up the plot of Norman OK.  However any of the other soundings can be selected  by left clocking on the star over the location. The soundings closest to Star Valley are SLC, BOI, and RIW. Soundings for the previous 7 days can also be selected. Again there is an extensive help menu provided on the page describing all the computed parameters from the sounding.  Additionally any questions can be addressed on the comment section.

Friday, October 14, 2011

Where is the Sun?

The forecast for Star Valley the past couple of days has called for mostly sunny.  Anyone in the valley knows that there has been very little in the way of sunshine on Thursday and so far today.  As with most of the weather that effects Star Valley, the mountains play a big role.  In this case even though Idaho Falls and Pocatello have been enjoying lots of sunshine, the lift from the Caribou and Salt Ranges has continually developed cloudiness.  To see this process in action go to the Web Camera page and build a several hour loop off the first cam looking out over the valley.  The processes that are maintaining the cloud cover over the valley are quite evident.  This can also be seen on the Forecast page and the visible loop over the area.

Wednesday, October 12, 2011

Current Conditions

There are three options under Current Conditions Temperatures, Winds and Rainfall.  The plot is centered over Star Valley.  Sources of the data are varied and in some areas overlap making it difficult to see all the stations.  Rolling the mouse across the data will pop up a source id.  The listing below the graphic is of all the stations that are displayed.

The plot is updated every 15 minutes.  Rainfall totals are for the  24 hours ending at data plot time.

Monday, October 10, 2011

Weather Cameras

The Weather Camera is a link to the site that was developed by John Hales as a Christmas Gift to me(his father) in 2008.  While John provides any technical needs, I am the site manager and maintain quality control of the Cams on the site.

At any given time there could be as many as 130 web cams displayed.  The criteria used to determine the display of a camera are:

1. Quality of the image.(StarDot Cameras much preferred).

2. Frequency of updates. (ideally every minute)

3. Proximity to Star Valley WY

4. View of the sky.

5. Reliability

Current Features

Left click on the image will provide a  larger current image

The cursor at the top of each cam will open up the control menu for that particular cam.

Left click on the minutes option(30 60 120 180 300) will build a loop of that length in time.

Left click on the info (i) button and it will bring up a google map centered on the webcam location.  Additionally it will display the latest weather observation and identifying the location of the observation.

There is also a radar option which when turned on will display the current composite reflectivity product from the NWS 

Clicking on the + will open up a looping option.  At least 3 days are available in the archive for all cams.  Selecting the date/time and looping length in minutes will rebuild a loop.

There are two options when building a loop.  The Load Loop option will rebuild a requested  time period  and display it.  A much more powerful option is the Create Video.  This will build the requested time period and then display the Download mp4 Video which will then produce a url  that can be copied/sent or saved as a video file.

As an example using this command a video was made of the Star Valley Ranch snow gauge on March 2 2012 when the snow depth was at its deepest point during the past winter.  This video was created on November 3 2012 as the number of archived days for this particular cam extended back that far.

While all cams have at least the most recent 3 days archived, additional days can be added to a particular cam upon request.