Southern Track Goldilocks Storm

Snowfall in the central Wasatch has been scant in recent days with a ridge in charge, but that will be changing tomorrow.  

Currently a monster cyclone lurks over the eastern Pacific with clouds along the accompanying cold front pushing into California.  Hooray!

This is, however, a splitting storm so the GFS forecasts the primary 500-mb trough and so called "synoptic forcing" associated with the system (also referred to as large-scale lift as indicated by the red upward vertical velocity contours in the upper left-hand panel below) to be over northern Mexico, SoCal, and Arizona at 1200 UTC 2 Feb (5 AM MST Friday).  

However enough of the frontal remnants and instability move through northern Utah that the GFS does give us periods of snow showers, including Friday night as the remnants of the front have moved downstream and we are in unstable northwesterly flow.  

A look at the GFS-derived guidance for Little Cottonwood shows mild conditions today, but transitioning to cooler by Saturday.  The GFS puts out almost 1.2" of water by Saturday 11 AM MST Saturday, which converts to about 18" of snow.  Given the decline in temperatures and wet-bulb zero levels, snow-to-liquid ratio is expected to increase over time resulting in a right-side-up snowfall.  

That said, it may take a bit to stack up as the 18" of snow the GFS produces in this case falls over a 36 hour period.  

A quick look at the downscaled SREF ensemble shows most members (23/26) producing 10" or more of snow for Alta-Collins through 0000 UTC 4 February (5 PM Saturday), with most of that falling by Saturday morning.  

Although the splitting nature of the storm gives me some heartburn, by and large I think this looks like a decent storm in which we are likely to get 12-20" of right-side up bliss in upper Little Cottonwood by Saturday.