Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 220458

Area Forecast Discussion
National Weather Service Salt Lake City UT
1058 PM MDT Thu Sep 21 2017

.SYNOPSIS...A cold core upper low developing over Nevada will
drift slowly east across the Great Basin through the weekend.
Much colder temperatures are expected across the region, with
periodic valley rain and mountain snow concentrating on the
northern half of Utah and southwest Wyoming throughout the


.DISCUSSION...A longwave trough remains situated across the Great
Basin this evening, anchored around an upper low spinning along
the ID/NV border region. The downstream surface front extends from
southwest through east central Utah, while the trailing mid level
baroclinic zone remains a focus for rain and higher elevation
snow across northern Utah, with precipitation transitioning to
more convective across southwest Utah.

A shortwave trough lifting through northwest Utah is helping to
enhance precipitation along the northern and central Wasatch Front
this evening. This feature is forecast to lift northward into
southern ID after midnight, which will likely result in a downward
trend in precipitation along the mid level baroclinic zone after

Winds in the pre-frontal regime across southern and eastern Utah
have diminished a bit this evening, and allowed the going wind
advisory to expire earlier. Otherwise made cosmetic changes to the
going weather grids to shift the thunder threat into southwest
Utah for the remainder of the evening. Snow levels have fallen to
the upper benches along the Wasatch Front within heavier bands,
however anticipate this to be short lived given the idea the
upper wave is currently translating north and away from the
forecast area.


.AVIATION...MVFR ceilings will likely persist at KSLC through the
overnight hours, before slowly scattering out during the mid to
late morning hours Friday. Winds in the wake of the band of
rainfall will likely remain southeasterly through the overnight
hours, although there is a 30 percent winds switch back to the
northwest after 06Z.


UT...Winter Weather Advisory until noon MDT Friday for UTZ007>009.




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