Pattern Change Coming

TL;DR: We have now been watching for a pattern change for several days, and it looks to arrive later this week and into the weekend.

Nowcast: An upper level ridge remains parked over the intermountain west, yielding weak flow and mild January temperatures. Skies remain clear and temperatures are inverted, which can clearly be seen in the 12z SLC sounding.

Source: NOAA/NWS Storm Prediction Center

Short-Term:

By 6 UTC on Thursday (midnight local time), a closed low will be centered over Utah, Nevada, and Arizona, per the current 6z GFS:

Source: University of Utah Department of Atmospheric Science

As this closed low progresses eastward over the four corners, the flow will in norhtern Utah will quickly shift from southerly to north-northwesterly, and we'll see precipitation in all of Utah's mountains, with the brunt of it in the southern and central mountains, closer to the center of the low-pressure system. Precipitation in the Wasatch will likely come in waves, and may amount to about 3-6" from Wednesday night through Thursday evening. 

Mid-Long Range: 

Things get more exciting this weekend, as a deep trough progresses southeastward from the Pacific Northwest, bringing widespread precipitation to the intermountain West. By 0 UTC on Monday (6 p.m. local time on Sunday) the trough axis will be located in Arizona with 500 mbar geopotential heights well below climatology, as indicated by the dark blue shading in the image below:

Source: Tropical Tidbits

A concern with this outlook is that the trough will track too far to our south and bring the most substantial precipitation to Arizona and New Mexico. That is reflected in the 6z GFS (not shown). We will, however, see precipitation associated with this system, and its cold nature will lead to fairly low-density snow in the Wasatch. As the event gets closer, we can zero in on amounts.

Snowfall Forecasts:

Mid-Week System: 3-6"

Weekend System: 1-2 Feet

Backcountry Comments:

If you will be traveling in the backcountry make sure you have the proper equipment and know before you go. For the whole avalanche forecast and all things avalanche head over to our friends at the Utah Avalanche Center.