“It’s the hap-happiest season of all”

Posted Thursday, December 20th, 2018 by Tyler West

TLDR:  Entering a stormy pattern with trough #1 Fri morning & 1-3”, trough #2 early Sat morning & another 2-4”.  A Trough skirts us Sun evening into early Mon with some snow before there’s a good chance of a stronger storm overnight Christmas Eve through Christmas Day.

Short Term:  The hap-happiest news is we’re entering a progressive pattern starting tonight.  It could be better though, as high pressure currently over the Intermountain West means this first system is going to decay some by the time it gets to us and the associated shortwave trough will produce 1-3” by late Fri morning.  A second (colder) trough comes overnight Fri to early Sat with a quick 2-4” more.  See below NAEFS graphic for Alta & focus on 21-22 Dec.  Note on the  that the bulk of dark blue lines are below the mean (solid red) which is one reason I have slightly lower snowfall totals than the mean.

NAEFS Downscale Guidance Valid 20 Dec 1200 UTC for Alta, UT (CLN).
NAEFS Downscale Guidance Valid 20 Dec 1200 UTC for Alta, UT (CLN).


Mid Term:  We then have a short break until Sunday when a storm enters the region.  As of now there will be two parts to this storm with the first and stronger part staying just to our north.  The second part is expected to impact northern UT Mon morning but it doesn’t have a ton of moisture and should produce < 6” based on current projections.

Long Term:  The GFS forecast model is saying all the right things for a strong cold front and decent shot of snow for most of UT (especially northern) late Christmas Eve into Christmas morning with showers off/on through Christmas Day.  The ECMWF has the bulk of moisture hitting southern UT but still has a decent storm, so still too early to say exactly where the main part will hit.  I’m expecting some accumulations statewide though.  Notice on the above graphic for Alta for 25 Dec that the CMCE mean (red dashed) actually drops below the GEFS mean (red solid).  The CMCE members are often biased high but in this case are lower since the CMCE is more in-line with the ECMWF.  Another storm is forecast for next Thu.  Happy Holidays and enjoy the new snow.


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