Windy Storm on Tap

Batten down the hatches because we have storm that might have everything but the kitchen sink in it for the Wasatch Range.

Right now Thursday looks dry, but the leading edge of the storm looks to move in on Friday with some mountain snow, mainly in the northern Wasatch, but probably tickling the central Wasatch some too.

Then Friday night things really start to get rolling.  The GFS forecast valid 0300 UTC 6 Dec (8 PM MST Friday) call for very strong flow (red ovals) to move over a low-amplitude ridge that is centered west of SoCal.  This leads to the inland penetration of an atmospheric river, as indicated by the filament of high integrated water vapor transport (IVT) that extends from southern Oregon to northern Utah (red arrow).  

This general pattern persists until Sunday morning, although flow, IVT, and precipitation intensity weaken late Saturday (if forecasts hold).  

The Utah Snow Ensemble forecast below focuses on the 24-hour period ending 0000 UTC 7 December (5 PM MST Saturday).  That is probably the wettest part of the the storm.  The ensemble mean for that period is 1.0" at Snowbasin and 1.2" at Alta-Collins (upper right panel).  

The Alta-Collins plumes show a bit of precip on Friday, but things really picking up Friday night.  and persisting until Sunday morning or later in a few members.  

The GEFS ensemble is more bullish on precipitation than the European (ENS).  As I said in the previous post, it's important to be rooting for America and that continues to be the case in this forecast.  

The median water and snow forecast by the ensemble from 5 AM Friday to 5 AM Sunday is 1.5" and 16.2" respectively.  Perhaps a reasonable estimate for snowfall totals during that period is 10-20", although the distribution above skews to higher values so the odds of more is probably greater than the odds of less.  A lot will depend on details that are hard to reliably anticipate this far ahead.

I suspect we will also see wind and rime.  New lifties for riming-prone lifts may have a real initiation Saturday morning.  Good luck. 

I'll see if I have time for a closer look on Friday.