Consequences of a Low Sun Angle

The first week of the New Year will see an absence of significant storm activity in the Star Valley region.  As a result the strong valley inversions that form with the long nights will remain through the afternoon as light winds and the low sun angle will  be insufficient to remove them.

Anyone who visits to the Salt Lake Valley with these inversions in place could experience trapped pollution and gloomy skies.  Jim Steenburgh has issued an interesting blog on the consequences of low sun angle and a stagnant weather pattern. 

Blessings and Curses of the Low Angle Sun

By Jim S

The sun just above Mt. Baldy shortly after noon today

Typically in Utah, the greatest threats to snow are wind and sun, so there's nothing better than a good early season snowpack combined with a low-angle sun like we have now.  Only on the warmest days can the sun do damage this time of year, so powder frequently lingers for days on most aspects in the backcountry provided it isn't trashed by the wind.  That doesn't happen in March, when the sun is almost always bad for south and west aspects and sometimes can be damaging to all but the steepest, north-facing slopes.

While the low-angle sun is a blessing for backcountry skiing, it is a curse for valley residents.  It doesn't provide enough energy to burn off cold pools (a.k.a., inversions) that form over the Salt Lake Valley and other low-elevation regions of Utah.  This is especially true when there is a fresh snow cover, which reflects a significant fraction of what little sun we get back to space.

We have just exited a fairly stormy pattern, so while there is a touch of smog over the valley, the pollution isn't too bad yet.

Salt Lake Valley from Alta

That will change in the coming days as we settle into a more stagnant pattern.  There are a couple of weak systems that brush by early next week, but it appears they will stir things up only a little, with Salt Lakers eventually seeing the worst air quality thus far this season as the week progresses.