Star Valley Downbursts, September 2 2012

Sunday evening September 2, 2012 a high based thunderstorm crossed Star Valley between 7:30  and 8pm.  It primarily affected the Thayne/Etna area eastward across Bedford andStar Valley Ranch.  I was  able to take a series of photos from Star Valley Ranch capturing a classic downburst signature.  While much of the rain evaporated as it fell through rather dry air before striking the ground, strong winds were recorded at each of the lower valley Davis Weather Stations.

The strongest gust was recorded at the Star Valley Ranch station where 48 mph was measured shortly after 8pm.

Following is a sequence of 5 photos taken at approximately one minute intervals looking west from Star Valley Ranch.

7:48 PM

7:49 PM

7:50 PM

7:51 PM

7:52 PM

It appears there were a series of downbursts with the storm with at least two captured in the photos.  The 7:48 and 7:49 images show one such downburst with the following 3 images catching a larger one.

The next figure is a schematic cross section of a downburst

And here is an excellent example of a downburst cloud with a similar bulbous cloud formation as in the Star Valley event.  This series of photos was taken in the Fall of 1991 in Oklahoma.

The radar Composite Reflectivity image showing the storm approaching from the west was not particularly strong

Pocatello Composite Reflectivity Image around 7:30 PM MDT

This is typical of downburst producing  storms as they appear rather weak on radar, in comparison to a more traditional severe thunderstorm.

The Star Valley Ranch weather station has a dramatic display of not only the 48 mph wind gust, but the very sharp pressure jump and temperature  drop as the storm passed.( about 40 minutes need to be added to this graphic as the internal weather station clock was found to be in error.)

Summer 2012 in Star Valley

In Star Valley, Labor Day typically brings an end to summer even though officially it becomes Fall on September 22st, the Autumnal Equinox. This is a good time to review the three summer months.  Warm and dry certainly were the descriptive terms for the Summer of 2012.

On an average June/July and August, around 4.5 inches of rain can be expected as recorded by the Bedford Climatological station.  This year the Bedford observer could only measure  .87 or about 20 percent of a normal amount.  Here are other July/July August Totals from around Star Valley.

Star Valley Ranch                  2.02
Alpine                                   1.81
2NE  Etna                             1.67
Thayne ES                            1.42
7S Smoot                             1.32
1.5SE Thayne                       1.31
Etna ES                                1.12

Regarding temperatures it has been warm days and cool nights with only a couple brief interruptions by a cooler air mass.  The warmest day of the summer was at all stations recorded the afternoon of August 8th.   The hot spot was the 98 observed at Alpine followed closely by 97 at Etna ES.  Even the usually coolest location of Star Valley Ranch reached a 94 on the 8th of August. Bedford came in with the coolest maximum of 90.

The first couple of weeks of June experienced the coolest weather, with all stations reporting their lowest  of the 3 summer months on the 7th of June. 27 degrees was the lowest reported at 3 location, Thayne and Etna ES along with 2 NE Etna.

Thayne ES had 11 days when the minimum dipped below freezing, 10 in June and 1 in August.  However there were 18 days when 90 or better was reached, 2 in June, 11 in July and 5 in August.

The following figure illustrates what makes for such a pleasant summer climate in Star Valley vs most other places in the U.S.  While most every day experienced warm afternoon, the mornings were pleasantly cool.

Thayne ES daily maximum and minimum temperatures Summer 2012

Chance of Precipitation in Star Valley Friday/Saturday

Riverton Forecast Office has provided a good summary of the expected weather in Star Valley and Western Wyoming for the next several days through their weekly on-line video. 


http://www.crh.noaa.gov/riw/?n=weatherbriefing

The next couple days will provide the best opportunity for precipitation since the middle of July.

Cold Smokey Morning in Star Valley

The  combination of the arrival of a somewhat cooler and very dry air mass combined with clear skies and light overnight winds resulted in some of the coldest readings in Western Wyoming since about the third week in June.

Here is a list of some of the observed minimums this Saturday morning.

Star Valley Area

3 NW Etna              28
Thayne ES              31
Auburn                    31
Etna ES                   32
2 NE Etna               33
Afton                       33
Smoot                      34
Alpine                      35
Star Valley Ranch    38

It was  cooler in some nearby areas

Bondurant WY            23
West Yellowstone MT 25
Warren Bridge WY      26
Bear Lake Airport ID   27

and not unexpected the coldest reported probably in the United States  this morning was at Peter Sinks UT west of Bear Lake where it dipped to 18 above.

The actual air mass is still warm above the strong morning inversions.  The Riverton balloon sounding at 6am Saturday morning indicated that the actual freezing level was about 14,000 feet MSL.

       The following is a plot of this mornings minimum temperatures in the Star Valley Region.

 The Peter Sink observation site is known to be a location of extraordinarily cold  temperatures as it is located in a high elevation basin which experiences ideal radiational cooling under these favorable conditions.  The local map of minimum temperatures below illustrates this clearly as nearby sitse at somewhat higher elevations were 30 degrees warmer

The smoke which has been a part of the scene in the Star Valley Region the past coupe weeks was very noticeable Saturday morning.  The winds on Friday afternoon resulted in a flare up of many of the ongoing fires across the Northwestern states.  Here is the map of current fires as of  Saturday morning.

While Star Valley is fortunate not to have active fires nearby, we are downwind of many large fires across Idaho.  The satellite photo clearing  illustrates the trajectory of the smoke from the fires spreading east across northern Lincoln County.

Visible satellite photo Saturday morning 8/25/12

 

 

Forecast of the winds turning more from the southwest and strong daytime mixing should result in a thinning of the smoke this afternoon, but until some significant precipitation can occur across the fire affected region, smoke will be a problem for sometime.

Riverton Weekly Weather Briefing

Star Valley has had a very uneventful August, weatherwise.  It has been dry and warm.  Through August 23rd all three CoCoRaHS www.cocorahs.org Observers in the valley, here at Star Valley Ranch, Thayne and just south of Smoot have reported .10 inches of rain.  The normal amount for the month of August is about 1.5 inches.  The current dry pattern does not support much of a chance of rain the remainder of the month.

Worthy subject matter for blogging has been hard to come by this summer.  However Riverton WFO  has provided an excellent on-line weather briefing video for the coming week, which includes an update of the ever expanding drought conditions.

Here is the link for the briefing

 http://www.crh.noaa.gov/riw/?n=weatherbriefing

Wyoming Drought Update-Star Valley Excluded thus far

The National Weather Service Forecast Office

in Riverton has issued a statement on the 

spreading drought conditions across much of

Wyoming. 

DROUGHT INFORMATION STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
753 PM MDT THU AUG 2 2012

...SEVERE AND EXTREME DROUGHT SPREAD INTO NORTHERN 

AND EASTERN WYOMING DURING JULY...

...PARTS OF THE SOUTHWEST IN EXTREME OR SEVERE 

DROUGHT RECEIVE ABOVE NORMAL RAINFALL IN JULY...

SYNOPSIS...

THE LATEST U.S. DROUGHT MONITOR FOR WYOMING RELEASED 

ON JULY 31ST SHOWED MODERATE DROUGHT /D1/ OR WORSE

ACROSS ALL BUT THE NORTHWEST PORTION OF THE STATE, 

OR ROUGHLY ALONG AND EAST OF AN AFTON TO DUBOIS TO 

CODY LINE. SEVERE DROUGHT /D2/ OR WORSE HAD EXPANDED
NORTH ACROSS MOST OF THE NORTH CENTRAL AND NORTHEAST. 

EXTREME DROUGHT /D3/ REMAINED ACROSS SWEETWATER COUNTY

INTO FAR SOUTHERN FREMONT COUNTY...AND FAR EASTERN

LINCOLN AND UINTA COUNTIES. EXTREME /D3/ DROUGHT HAD

ALSO EXPANDED FROM THE HIGH PLAINS INTO EASTERN

WYOMING.  ABNORMALLY DRY /D0/ CONDITIONS WERE

OBSERVED ACROSS MOST OF NORTHWEST WYOMING WITH THE

EXCEPTION OF NORTHERN YELLOWSTONE NATIONAL PARK. 

ONE YEAR AGO...WYOMING WAS 100 PERCENT FREE OF DROUGHT

OR ABNORMALLY DRY CONDITIONS. ABNORMALLY DRY /D0/

OR MODERATE /D1/ DROUGHT CONDITIONS DEVELOPED MORE

RAPIDLY THROUGH THE SPRING AFTER A BELOW NORMAL WINTER

SNOWPACK AND A VERY WARM AND DRY SPRING. 

ROCK SPRINGS HAD THE WARMEST AND DRIEST SPRING
MARCH-MAY) ON RECORD. JUNE 2012 WAS THE DRIEST ON RECORD IN
WYOMING SINCE 1895 WITH A STATE AVERAGE OF 0.45 INCHES OF
PRECIPITATION. JUNE 2012 WAS ALSO THE 6TH WARMEST OVER THE LAST
118 YEARS IN WYOMING. THE WATER YEAR TO DATE...OCTOBER 2011
THROUGH JUNE 2012...RANKED AS THE 12TH DRIEST FOR WYOMING SINCE
1895...AND THE DRIEST SINCE 2002. THE FIRST HALF OF 2012...JANUARY
THROUGH JUNE...RANKED AS THE SECOND DRIEST OVER THE LAST 118
YEARS. THE DRIEST FIRST SIX MONTHS OF THE YEAR WAS IN 1919.

SUMMARY OF IMPACTS...

RIVER AND STREAMFLOW CONDITIONS.

28-DAY AVERAGE STREAMFLOW CONDITIONS ON AUGUST 1ST SHOWED MUCH
BELOW NORMAL OR BELOW NORMAL STREAMFLOWS AT MOST STATIONS IN AREAS
CLASSIFIED AS MODERATE DROUGHT /D1/ OR HIGHER. THE EXCEPTION WAS
IN THE UPPER AND LOWER GREEN RIVER BASINS WHERE NORMAL STREAMFLOW
CONDITIONS WERE OBSERVED.  STREAMFLOWS WERE ALSO CLASSIFIED AS
NORMAL NORMAL IN THE NORTHWEST OR IN THE SNAKE RIVER BASIN...UPPER
YELLOWSTONE AND MADISON RIVER BASINS.

FIRE WEATHER IMPACTS...

FUELS WERE CLASSIFIED AS CRITICAL IN ALL AREAS ACROSS WEST AND
CENTRAL WYOMING. ON AUGUST 2ND...FIRE DANGER WAS CLASSIFIED AS
VERY HIGH TO EXTREME ACROSS MOST AREAS IN MODERATE DROUGHT /D1/ OR
HIGHER. FIRE DANGER WAS MODERATE TO HIGH ACROSS PORTIONS OF
NORTHWEST WYOMING WHICH WERE FREE OF DROUGHT OR ABNORMALLY DRY
/D0/.  THE SEASONAL SIGNIFICANT WILDLAND FIRE POTENTIAL OUTLOOK
FOR AUGUST THROUGH OCTOBER 2012 SHOWED ABOVE NORMAL SIGNIFICANT
FIRE POTENTIAL PERSISTING ACROSS WEST AND CENTRAL WYOMING.
CONTACT YOUR LOCAL COUNTY OFFICIALS FOR THE LATEST BURNING
RESTRICTIONS.

CLIMATE SUMMARY...

BELOW ARE THE CUMULATIVE PRECIPITATION AMOUNTS FROM SELECTED
LOCATIONS ACROSS WEST AND CENTRAL WYOMING FOR THE CURRENT WATER
YEAR...

LOCATION               WATER YEAR PRECIPITATION            % AVERAGE
                       TO DATE (OCT 2011-JULY 2012)        (1981-2010)
--------               ---------------------------        -----------

AIRPORTS

^ BIG PINEY                      2.34                           47
^ BUFFALO                        9.15                           81
* CASPER                         9.32                           81
* EVANSTON                       2.98                           31
* GREYBULL                       4.40                           71
^ LANDER                         8.51                           77
* RIVERTON                       4.74                           60
+ ROCK SPRINGS                   4.89                           70
^ SHERIDAN                      12.32                          103
* WORLAND                        3.93                           62

COOPERATIVE OBSERVER STATIONS

  BEDFORD 3 SE                  17.75                           96
+ BITTER CREEK 4 NE              3.91                           72
* FOSSIL BUTTE
  NATIONAL MONUMENT              7.21                           80
+ GREEN RIVER                    5.82                           86
  MOOSE                         15.65                           82
  OLD FAITHFUL                  24.35                          108
^ POWELL FIELD STATION           5.43                           96
^ RIVERTON (DOWNTOWN)            4.82                           72
* THERMOPOLIS                    6.13                           62 

At Star Valley Ranch for the same period the precipitation was 19.58 and at the 7 south of Smoot 

Observation site 18.19. 

 + LOCATION IN EXTREME DROUGHT /D3/
* LOCATION IN SEVERE DROUGHT /D2/
^ LOCATION IN MODERATE DROUGHT /D1/ 

 PRECIPITATION/TEMPERATURE OUTLOOKS...

THE OUTLOOK FOR AUGUST SHOWS A 50 PERCENT OR GREATER CHANCE OF
ABOVE NORMAL TEMPERATURES ACROSS MOST OF WYOMING. THE AUGUST
PRECIPITATION OUTLOOK SHOWS EQUAL CHANCES OF ABOVE...BELOW OR
NORM AL PRECIPITATION...OR NO SIGNIFICANT CLIMATE SIGNAL ACROSS
MOST OF THE STATE.

THE SEASONAL OUTLOOK FOR AUGUST...SEPTEMBER AND OCTOBER SHOWS A
GREATER THAN EQUAL CHANCE FOR ABOVE NORMAL TEMPERATURES ACROSS THE
SOUTHEAST THIRD OF THE STATE...OR ROUGHLY ALONG AND SOUTH OF A
ROCK SPRINGS TO CASPER LINE. EQUAL CHANCES OF ABOVE...BELOW OR
NORMAL TEMPERATURES COVER THE REST OF THE STATE. THE 90 DAY
PRECIPITATION OUTLOOK SHOWS EQUAL CHANCES OF ABOVE...BELOW OR
NORMAL PRECIPITATION...OR NO SIGNIFICANT CLIMATE SIGNAL ACROSS
WYOMING.

THE U.S. SEASONAL DROUGHT OUTLOOK ISSUED ON AUGUST 2ND SHOWED THAT
DROUGHT CONDITIONS WERE LIKELY TO PERSIST OR INTENSIFY THROUGH
OCTOBER ACROSS ALL AREAS IN WYOMING THAT ARE CURRENTLY IN
DROUGHT...WITH THE EXCEPTION OF THE FAR SOUTH WHERE SOME IMPROVEMENT
IS FORECAST. DROUGHT CONDITIONS ARE NOT CURRENTLY FORECAST TO
DEVELOP IN NORTHWEST WYOMING.

AN EL NINO WATCH HAS BEEN ISSUED BY THE CLIMATE PREDICTION CENTER.
CHANCES HAVE INCREASED FOR EL NINO BEGINNING IN AUGUST- SEPTEMBER
2012 AND CONTINUING THROUGH THE WINTER OF 2012-13. ENSO-NEUTRAL
CONDITIONS PREVAILED ACROSS THE EQUATORIAL PACIFIC FROM MAY
THROUGH JULY FOLLOWING THE DISSIPATION OF LA NINA IN APRIL.

HYDROLOGIC SUMMARY AND OUTLOOK...

THE FOLLOWING RESERVOIR DATA WAS OBTAINED ON AUGUST 1ST...

RESERVOIR                 PERCENT FULL

CENTRAL WYOMING
BOYSEN                      77.3
BUFFALO BILL                93.2
BULL LAKE                   97.1
PATHFINDER                  54.1

UPPER GREEN RIVER BASIN
BIG SANDY                   50.0
FONTENELLE                  95.0
FLAMING GORGE               82.0

UPPER SNAKE RIVER BASIN
GRASSY LAKE                100.0
JACKSON LAKE                91.0

NEXT ISSUANCE DATE...

THIS PRODUCT WILL BE UPDATED ON AUGUST 15 2012 OR SOONER IF
NECESSARY IN RESPONSE TO SIGNIFICANT CHANGES IN CONDITIONS.

&&

RELATED WEB SITES...

ADDITIONAL INFORMATION ON CURRENT DROUGHT CONDITIONS MAY BE FOUND AT
THE FOLLOWING WEB ADDRESSES /USE LOWER CASE LETTERS/...

TO REPORT EFFECTS OF THE DROUGHT IN YOUR AREA...PLEASE GO TO THE
DROUGHT IMPACT REPORTER AT...

HTTP://DROUGHTREPORTER.UNL.EDU/

...AND CLICK ON SUBMIT A REPORT.

INFORMATION FOR THE MEDIA MAY BE FOUND AT...
HTTP://DROUGHT.UNL.EDU/NEWSOUTREACH/INFORMATIONFORMEDIA.ASPX

NWS RIVERTON DROUGHT PAGE...
HTTP://WWW.CRH.NOAA.GOV/RIW/?N=DROUGHT

USGS WYOMING DROUGHT WATCH...
HTTP://WY.WATER.USGS.GOV/PROJECTS/DROUGHT/

U.S. DROUGHT MONITOR...HTTP://WWW.DROUGHT.GOV

NOAA DROUGHT PAGE...HTTP://WWW.DROUGHT.NOAA.GOV

CLIMATE PREDICTION CENTER /CPC/...HTTP://WWW.CPC.NCEP.NOAA.GOV

ADDITIONAL RIVER AND RESERVOIR INFORMATION...

NWS ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/...
HTTP://WWW.WATER.GOV/AHPS2/INDEX.PHP?WFO=RIW

USGS...HTTP://WATER.USGS.GOV/

USBR...HTTP://WWW.USBR.GOV/

ACKNOWLEDGMENTS...

THE DROUGHT MONITOR IS A MULTI-AGENCY EFFORT INVOLVING NOAA/S
NATIONAL WEATHER SERVICE AND NATIONAL CLIMATIC DATA CENTER...THE
USDA...STATE AND REGIONAL CENTER CLIMATOLOGISTS AND THE NATIONAL
DROUGHT MITIGATION CENTER. INFORMATION FOR THIS STATEMENT HAS BEEN
GATHERED FROM NWS AND FAA OBSERVATION SITES...STATE COOPERATIVE
EXTENSION SERVICES...THE USDA...USACE AND USGS.

QUESTIONS OR COMMENTS...

IF YOU HAVE ANY QUESTIONS OR COMMENTS ABOUT THIS DROUGHT INFORMATION
STATEMENT...PLEASE CONTACT...

ARTHUR MEUNIER
CLIMATE/DROUGHT FOCAL POINT
NATIONAL WEATHER SERVICE
12744 WEST US HIGHWAY 26
RIVERTON, WY  82501
TELEPHONE...307-857-3898
............800-211-1448
EMAIL...ARTHUR.MEUNIER@NOAA.GOV

Wyoming Precipitation Information

Here is some interesting information on the precipitation in Wyoming.

A map of normals for the state dramtically show the effect of the terrain.

Some of the major cities of  the state follow:

The Wyoming  precipitation records are:

 Greater amounts occur in the high mountains of Northwest Wyoming such as the Tetons, but official records are only included here.