TL;DR:
A prolonged period of precipitation is beginning today in the Northern Utah Mountains. There is low agreement between solutions on the specific snow totals, but regardless this will be a significant series of events with the potential for all-time turning conditions by the New Year.
Nowcast:
Current conditions in the Central Wasatch are variable at best. If the powder itch just can't wait to be scratched, today you'll find windy conditions with warm temperatures and rain at lower elevations. Winds are gusting 50-80mph on the highest ridgelines. Hidden Peak at Snowbird hit 103mph this morning although I suspect this is not 100 percent accurate as Mt. Baldy has only peaked at 80mph. Temperatures are warm before the cooler air arrives later today ranging from 38F at 7000ft at the base of Park City, to 30F at 9000ft at Alta to 25F at the top of Mt. Baldy.
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| Currently snowing at Alta Ski Area this morning, looking West down Little Cottonwood Canyon. Image courtesy of Alta Ski Area. |
Short-term Forecast:
A longwave trough and associated atmospheric river are making their way into Utah this morning, bringing lower-elevation rain and upper-elevation snow through Thursday morning. The trickiest part of this storm will be the snow levels. Atmospheric rivers are long-flowing regions of water vapor in the atmosphere originating generally in the subtropics. As they entrain sub-tropical moisture they also bring with them warmer air masses and higher snow levels. Today, the snow levels might be as high as 8000ft during the early part of the storm, bringing rain and mixed precipitation to the bases of Deer Valley, Park City Mountain Resort, and possibly Solitude as well. These levels will lower as the day progresses reaching below 6500ft by Wednesday morning.
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| NASA GOES-West Visible Satellite channel this morning showing the Atmospheric River stretching thousands of miles across the NE Pacific Ocean and penetrating inland. Image courtesy of the College of DuPage. |
Long-term Forecast:
Another, potentially bigger, atmospheric river (AR) looks to impact Utah around the New Year with storminess continuing into 2023. This AR will make landfall in southern California and move to the Northeast, missing the highest terrain of the Sierra Nevada and bringing more widespread precipitation to Northern Utah.
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| NCEP GFS Integrated Vapor Transport (IVT) and Mean Sea Level Pressure (MSLP) plot showing the inland penetrating atmospheric river, valid 11pm MST December 31. Image courtesy of the Center for Western Weather and Water Extremes at UC San Diego. |
Looking even further out, the NOAA Climate Prediction Center keeps Utah with chances skewed for above-average precipitation through both the 6-10 day and 8-14 day forecast periods. In that period, it looks as though a quasi-stationary longwave trough will set up off the US West Coast. If that pattern stays close enough to the coast, we may be talking about an extended run of storms for the Intermountain West. Alternatively, this pattern could remain too far to our West, shutting us off past the 10-day period.
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| GFS Composite Radar Reflectivity valid 5pm MST Thursday, December 29 through 11am MST Monday, January 2. Image courtesy of Tropical Tidbits. |
Snow Forecast through Thursday Afternoon:
Big Cottonwood (Solitude and Brighton) - 16 to 26 inches
Little Cottonwood (Alta and Snowbird) - 18 to 30 inches
Park City and Deer Valley - 6 to 14 inches for bases (~7000ft), 12 to 20 inches for upper elevations (~9000ft)
If you plan to travel in the backcountry ensure you are properly equipped and know before you go. For all things avalanche and the full avalanche forecast head over to our friends at the Utah Avalanche Center.
Unfortunately, I am out of the state visiting family so make some turns for me! I will definitely be living vicariously through everyone's stoke for what's setting up to be all-time late December conditions in the Wasatch. Enjoy!
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