Batten Down the Hatches

The Snow Miser has some tricks up his sleeve for Christmas Week

After some periods of mountain snow Sunday and Monday, some serious winter weather will be blowing into the Wasatch late Monday and Tuesday.  As shown by the GFS forecast below, which is valid for 1800 UTC (1100 MST) Tuesday, the Pacific jet is expected to extend into the Intermountain West, yielding strong westerly and west-northwesterly flow at nearly all levels.  This is an extremely moist fetch as well, with strong orographic enhancement expected over the mountains.

This can also be seen in the GFS time-height section for Salt Lake City (time increases to the left).  That period around 1800 UTC Sunday features deep moisture and very strong flow, reaching 50 knots as low as 750 mb (~8500 ft).  

Our downscaled NAEFS forecast plumes show the light accumulations ahead of the storm, but then the big event on Tuesday (22 December) when most ensemble members are generating over 2 inches of snow-water equivalent from 0000 UTC 22 Dec to 0000 UTC 23 Dec, with some more tacked on thereafter.  These are some of the largest water totals I've seen produced by this product since we started producing it last year, although they might be overdone a bit.  There are a couple of ensemble members that are a bit less bullish, so perhaps a huge water event isn't in the bag yet, but a significant storm is likely.  

This should be a "batten down the hatches" with both heavy snowfall and strong winds.  Weak layers in the snowpack should be stressed severely.  A reminder of the monsters lurking in the basement was provided to us yesterday as we gazed into Mineral Basin from Sugarloaf Pass.