Big November storm coming in hot!

TL;DR:

A large-scale trough will advect substantial amounts of moisture into Utah through Thursday. Expect 20-30 inches of medium to high-density snow in the mountains with the potential for some valley snow. The highest snowfall rates will be seen Wednesday morning/mid-afternoon. 

Nowcast:

Currently, we are starting to see the beginnings of this storm. The figure below shows highest radar reflectivities over the Central Wasatch. Some convection was popping up earlier this morning resulting in valley rain and some intermittent mountain snow. Alta is reporting 5" currently. 

College of DuPage 

I would expect this intermittent convective pattern to continue throughout the day. 

Short term:

Later tonight and into tomorrow morning is when things begin to get interesting. The High-Resolution Rapid Refresh (HRRR) model suggests that more intense snowfall rates will begin in the Salt Lake Valley and Central Wasatch early tomorrow morning (~3-4 AM MST). 

If we look at an output of this model called a time heights plot, we can better see the passage of the cold front and the increased precipitation rates. I've highlighted the frontal passage with a red oval in the plot below, . 

U of U Atmospheric Sciences

The real question from a precipitation standpoint is how long this front ends up stalling on the Wasatch. Below is a plot of total precipitation from the 48hr HRRR run. Total values are in inches of water. 

U of U Atmospheric Sciences

The GFS model suggests a 10:1 snow-to-liquid ratio before the frontal passage, followed by a 15:1 snow-to-liquid ratio after the passage of the cold front. This means in the mountains, we could expect 20-30 inches of snow. Down in the valley, I'm forecasting 1-3 inches. 

Long term:

From a long-term standpoint, things are looking pretty meager. There could be a small-scale trough making its way through Utah early next week, but I don't think any precipitation will be associated with it. However, I don't see any signs of a major ridge taking hold which is the best we can hope for at this point.

I'm just thankful we've got a relatively moist storm impacting us this week that will hopefully keep the snowpack relatively insulated. As always (and especially given our forecasted snowfall totals), make sure to check the UAC before venturing into the backcountry.