2018 goes out with a frigid, windy bang

Posted Monday, December 31st, 2018 by Pete Saunders

THE COLD

It’s no secret…it’s COLD outside. As Marcel and Lucas have forecasted over the past couple of days, temperatures behind the low pressure system that brought us a decent amount of snow yesterday (10+ inches in the Cottonwoods, 5+ inches in the Park City resorts, and 4 inches at Snowbasin) are frigid in both the mountains and valleys. Below are the Salt Lake NWS forecast temperatures for several locations throughout Utah for today through afternoon tomorrow.

NWS forecast temperatures for the New Year. Courtesy: weather.gov
Salt Lake NWS forecast temperatures for the New Year. Courtesy: weather.gov

THE WIND

Not only that, but it’s gonna be windy too. The National Weather Service in Salt Lake City has issued a Wind Advisory for the Salt Lake and Tooele valleys valid from 1700 MST tonight through 0800 MST Tuesday morning for winds gusting up to 50 mph. Further north over the northern Wasatch Front, there is a High Wind Warning for the same times. Wind gusts of up to 55 mph, and localized wind gusts in Farmington and Centerville of up to 65 mph, are expected during that time.

THE COLD AND WIND (WIND CHILL)

While it won’t be as windy in the mountains compared to the northern Wasatch Front valley, it still will be pretty breezy. And with frigid air already in place, this is not a good combination. Wind chills overnight could reach down as low as-33 degrees Fahrenheit at the ski resorts.

So why is it going to be so windy and cold? A look at the 700 hPa wind chart can help answer that question. The low pressure system that passed through our area yesterday is now to our south, allowing easterly winds to run perpendicular to the northern Wasatch Front. Because of these easterly winds, cold, dense air is able to move or “advect”  toward the northern Wasatch Front, then descent rapidly into the valley regions. There’s also a very tight MSLP (mean sea level pressure) gradient forecast oriented from NW to SE from the Wasatch Front to SW Wyoming, pointing the direction of gradient wind toward the mountains from the northeast, where they can then descend quite rapidly toward the valley. So this is why we expect gusty winds, especially north of Salt Lake City, this evening through the early part of New Years Day.

HRRR 700 hPa wind forecast for this evening through tomorrow morning. Note the green "blobs" indicating strong winds, and with the wind barbs' orientation perpendicular to the mountains bringing in advection from a cold and dense airmass, and with a tight MSLP gradient and
HRRR 700 hPa wind forecast for this evening through tomorrow morning. Note the green “blobs”  in northern Utah just east of the Great Salt Lake indicating strong winds. With the wind barbs’ orientation perpendicular to the mountains and  advection from a cold and dense airmass taking place (along with a tight MSLP gradient and stable airmass), this sets the stage for moderately strong downslope winds over the northern Wasatch Front. Courtesy: weathernerds.org

WEDNESDAY AND BEYOND

Ridging will bring in boring (sunny and dry) and inverted (visibly polluted) conditions over Utah for the good portion of the week through at least Saturday evening. On Sunday, the GFS and ECMWF (Euro) models are picking up on a closed low from the Pacific moving into the continental U.S. from the southwest on Sunday that would bring our next chance of mountain snow.  As of right now, it looks like flow could be rather split as the trough makes land over Southern California. During that time (Sunday), a warm front looks like it could push through Utah and perhaps give the mountains a few snow showers. Then, as the trough moves through on Monday, more appreciable snow could fall. It could be pretty wet, heavy snow Monday morning, but turn more powdery in the afternoon and evening that day as the cold advection portion of the trough moves through our area. Hopefully the trough deepens as it moves across the western U.S. (or at least becomes less “splitty”) so we can maximize our snow accumulations!

Have a Happy New Year!! Be safe celebrating tonight in the cold and wind, and check back in for developments on the potential snow at the end of the upcoming weekend.

-Pete

 

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