Here We Go!

The obscured Wasatch Range from the University of Utah, 8:30 AM MST 7 Feb 2014

Our multi day snow event is now underway.  Overnight and early morning snow totals as of 8 am in the mountains based on automated sensors include 6 inches at Snowbasin-Middle Bowl, 7 inches at Park City-Jupiter, 7 inches at Solitude-Powderhorn, 9 inches at Solitude-Summit, and 5 inches at Alta-Collins.

Although the mountain snows today may be heavy at times, they will likely come in fits and starts with some breaks at times.  Things get more interesting overnight tonight and tomorrow as an atmospheric river, a narrow corridor of strong moisture transport, makes landfall in northern California and penetrates into northern Nevada and Utah.  

Atmospheric rivers feature strong values of integrated water vapor transport (IVT), a measure of the amount of water vapor flowing over a given location every second.  By 1800 UTC (1100 MST) tomorrow, very high values of IVT associated with the atmospheric river extend over northern California and across northern Nevada and Utah. For late January and early February, such high IVT values have a climatological frequency of occurrence of about once every 5-10 years over northern Utah. 

Source: NWS

The productivity of this storm depends on how much of that water vapor we can convert to precipitation.  The 12-km NAM remains fairly excited for the Wasatch, generating almost 3 inches of snow-water equivalent and 40 inches of snow at Alta by 5 PM Sunday (just a shade less than the 12-km NAM forecast from yesterday morning as discussed in the previous post) with some additional accumulations Sunday night.  

Source: weather.utah.edu

I still think the NAM is in the upper portion of possibilities for this storm at Alta and will stick with my forecast from yesterday which calls for a total by 5 PM Sunday afternoon of 2-3.5 inches of water and 25-40 inches of snow at Alta-Collins.  Some bigger water totals are possible in the northern Wasatch.