|Looking southeast toward the Wasatch Mountains @ 9:20 AM|
In fact, the models are going berserk later today and tonight in the Wasatch Mountains. The 1200 UTC NAM, for example, generates more than 0.5 in of SWE in portions of the Wasatch Mountains during the 3-h period ending at 5 PM.
|NAM forecast valid 5 PM MST 18 Jan 2012|
As we discussed yesterday, this will likely be Cascade Concrete with a high water content. The Alcott algorithm is presently calling for a water content of 14%. All this heavy snow will be falling on an incredibly weak snowpack. Not surprisingly, the Utah Avalanche Center has issued an Avalanche Warning beginning at 2 PM for the Wasatch backcountry.
Perhaps the most difficult aspect of this forecast is the snow level. Here's why. We have a ton of warm air streaming in aloft, but cold, dry air is entrenched at the surface. Yesterday it appeared that cold, dry low-level air would scour out enough for snow levels would rise, but it is stingier in the latest model runs. This leads to a deep stable layer in the latest NAM forecast that is below freezing and would enable snow to fall even in the lower elevations of the Wasatch Mountains.
|NAM forecast sounding for KSLC valid 8 PM MST 18 Jan 2012|