Sound the Alarms!

Posted Wednesday, February 5th, 2020 by Taylor McCorkle

TLDR: A pacific trough and atmospheric river will bring ample moisture and persistent northwest flow to the intermountain west – this will allow for FEET of snow to fall in the Wasatch.

Currently, temperatures are in the low 20’s across the Wasatch front and approaching zero Fahrenheit at crest level. Winds are out of the north-northwest and will remain this orientation through the end of the work week. Below is the observed sounding from KSLC. Note the strong winds from the NNW and the temperature profile, which slightly decreases to 700 mb until it reaches the inversion

KSLC 12Z sounding for Wed. morning. spc.noaa.gov

Up at the resorts, conditions aren’t ideal, which is typical of a pre-storm day. Visibility is low and the winds are gusting to 35+ mph.
Here’s a view from a Snowbird webcam at 11:30am.

Snowbird web cam views – live at 11:30 am mst

Short-Term Forecast:
Today’s conditions are average at best, but the work week will end in spectacular fashion. As we approach the evening hours, the Pacific trough will begin digging into the Intermountain West and allowing precipitation to become more widespread. As this happens, winds aloft will also increase, bringing cold, moist air into the region. Below is the NAM 3km forecast showing the 500 mb trough and winds, valid this evening at 6pm mountain time.

NAM 3km forecast 500mb heights and winds. Plot via maps.weatherbell.com

Snow will begin this evening and persist through the morning hours tomorrow for the North/Central Wasatch and mountain valleys along the Wasatch front. The accumulations in the valleys wont be anything close to what we experienced on Monday, but it still has the potential to cause some problems for the Thursday morning commute. Also different from our Monday storm, the mountains will go back to getting more snow.. And I mean LOTS more this time. Below is a gif of forecast reflectivity, showing how once the precipitation starts, it will persist and be enhanced by the prolonged northwest flow regime we are entering

As the week ends, warm air will be advected into the region from the southwest, which will considerably warm surface temperatures. This will also likely change the valley precipitation from snow to rain. Now for what you all came here for… The snow totals!

Snow Forecast:
So I know this is what you all came here for.. But lets go over the knowns and unknowns for this storm.

Knowns
– Its going to snow ALOT
– This storm will be cold and long duration
– Ample moisture will be present
– Northwest flow will favor places like the Cottonwoods

Unknowns
– How much snow will fall in the post-frontal orographically enhanced regime. This is when the NW flow condenses any available liquid after the main portion of the storm has moved out.

Models are going nuts will numbers – Some are more realistic, while others are going crazy with 5+ feet (Looking at you, NAM 3km). If you saw my tweet earlier, you saw the SREF plumes, which I think give you a good idea of the uncertainty in the snow totals forecast for the grid point near Alta.

SREF snowfall guidance via weather.utah.edu

SO, after all that, here’s what I’m thinking through Friday morning –

Cottonwoods: 20-30″
Park City: 6-12″
Ogden area resorts: 12-18″
Sundance: 10-15″

Now I know we are all going to be STOKED to ski the next few days, but do me a favor and
1. Drive carefully
2. Carpool, carpool, carpool!
3. Keep this little powder secret between us 😉

The hype train is now leaving the station

-Taylor

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