Wasatch Weather Weenies

A few days ago, some of the "deterministic" global forecast models, namely the GFS and the ECMWF HRES, forecast a truly spectacular cold surge for the continental United States this coming week.  There were a few forecast runs that brought the cold surge directly into the mountain west.  Below is an example from the ECMWF HRES initialized on 0000 UTC 13 December, which produced a 240 hour forecast [valid 0000 UTC 23 December (5 PM MST Thursday) with a spectacularly low 700-mb (10,000 ft) temperature of -34˚C (-29˚F) over southern Wyoming and -30˚C over Salt Lake City.   How insane is cold air like that for Salt Lake City?  A 700-mb temperature of -30˚C has only been observed once in the upper-air sounding record for northern Utah, which began in 1950.   However, today we run ensembles of forecasts to get a handle on the uncertainty in the forecast, and other members of those ensembles had different ideas.  Some didn't bring the cold surge into no...

 There's a pretty good cold surge expected to push into northern Utah later this week.  By Friday afternoon, yesterday's high of 88˚F will be long forgotten.   Below is the GFS forecast for 2100 UTC (3 PM MDT) Friday showing a short-wave trough moving through northern Utah with 700-mb (10,000 ft) temperatures near -8˚C.   The GFS-derived Little Cottonwood forecast shows temperatures on Mt. Baldy dropping from 43˚F tomorrow afternoon to 13˚F Friday morning.  Your Friday morning dawn patrol will feature slide-for-life conditions in the Baldy Chutes.   Right now, the system looks fairly dry.  The GFS produces only 0.13" of water equivalent with it on Friday at Alta.  There are a few members of NAEFS (11 out of 52) that produce more than 5" of snow at Alta Collins, but most are under 2".   Unless a low-probability snowfall occurs, the best recreation options later this week and weekend are probably at lower elevations.

This is my first post since Saturday's tragic avalanche in Wilson Glade.  My heart goes out to the victims and their friends and family.  Let me also express my gratitude to all of the first responders, rescue and recovery personnel, and Utah Avalanche Center staff for all of their efforts.   I've decided to focus on temperature for this post rather than snow.  Often temperature is an "easier" forecast variable than precipitation or snowfall, but that's not the case for this weekend.   A look at the GFS forecast for 1800 UTC (1100 MST) Saturday shows northern Utah in an arctic airmass that has surged across the Continental divided, dropping 700-mb temperatures in the Salt Lake Valley and Wasatch Mountains to -20˚C or colder.   In fact, the GFS forecast 700-mb temperature for the Salt Lake City International Airport is -21.4˚C at that time.   Readers of this blog know that I get excited about 700-mb temperatures above 20˚C or below -...