Don’t Count your Chickens Before they Hatch

Posted Tuesday, February 27th, 2018 by Alex Lukinbeal

TLDR

Party cloudy skies with calm winds are expected Wednesday.  Southwesterly winds ramp up Thursday afternoon with snow showers beginning across mountain resorts.  Snow is likely Friday through the weekend with significant accumulations possible. 

Short Term Forecast

Skies will begin to clear out Wednesday afternoon with calm winds and mostly sunny skies expected.  Our next storm system is expected to arrive in Utah Thursday afternoon.  A deep closed low will dig off the coast of the Pacific Northwest Thursday evening into Friday morning.  Southwesterly winds will increase Thursday afternoon with a round of mountain snow showers expected.  Snow shower activity will continue through Friday morning before briefly tapering off ahead of the cold front Friday afternoon.

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ECMWF 500 mb ensemble height anomaly for Friday morning. A deep closed low is located just off the coast of the Pacific Northwest. Courtesy of www.tropicaltidbits.com

The main story ahead of the cold front will be strong prefrontal winds on the order of 60-80 mph along ridge lines.  Dust is likely to be kicked up across the deserts in western Utah and will be brought into the Wasatch Front and mountain resorts in the Cottonwoods and surrounding areas.  Along the cold front, there will be the potential for very heavy snowfall as the front lifts an abnormally moist air mass.  The air mass along the frontal boundary is expected to have column integrated water vapor values in the 90-95th percentile for this time of year.  As the front moves into northern Utah, models are suggesting the boundary will stall, allowing for a period of prolonged heavy snowfall.  The main forecast challenge is determining the exact area the boundary will set up.

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GFS total column integrated water vapor anomaly for Friday morning.

Currently, ensemble members are in surprisingly good agreement with the frontal boundary stalling out across northern Utah bringing a period of prolonged heavy snowfall to mountain resorts.  As you can see below, the ensemble members are fairly close to each other generating anywhere from 25″ to 45″ of snowfall.  However, there is still plenty of uncertainty with this system.  If the upper level low moves slightly further to the north or west, the boundary could set up to our west or north, leaving the Wasatch high and dry.

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NAEFS ensemble precipitation and snowfall in the Upper Cottonwoods. Courtesy of weather.utah.edu

For now keep monitoring the latest forecasts as there is the potential for one of the biggest snow storms of the year Thursday through Sunday morning.

Long Term Forecast

High pressure will return to the area late Sunday into early next week with mostly sunny skies and warmer temperatures expected.

-Alex

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