Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 111121

Area Forecast Discussion
National Weather Service Salt Lake City UT
421 AM MST Thu Jan 11 2018

.SYNOPSIS...A moist west to northwest flow aloft will remain over
northern Utah through Friday. High pressure aloft strengthening
over the western states will bring dry conditions to the area
with increasing urban haze and valley fog expected this weekend
through early next week.


.SHORT TERM (Until 00z Monday)...The next mid-latitude shortwave
currently near 135W will crest the low amplitude upper ridge over
the west coast states and reach northern Utah by this evening.
Moist but relatively shallow warm advection out ahead of this
feature will generate clouds and some light precip across far
northern Utah/southwest Wyoming this afternoon. This precip will
likely expand a bit farther to the south as the shortwave races
east-southeast through eastern Idaho/northern Utah late tonight
through early Friday. Light amounts of accumulating snow are
expected over the northern Wasatch/western Uintas as the dynamic
and jet support for lift look sufficient to generate persist light
snow later tonight through at least Friday morning. Adjacent
valley locations will also see light snow, or even a rain/snow mix
during the same period. Can not rule some valley accumulations,
though amounts will likely be less than 2 inches.

Heights will build rapidly to the west of the area heading into
the weekend. The resultant high amplitude upper ridge over the
western CONUS will leave Utah dry with an increasingly stable air
mass over the area. Valley inversions will once again strengthen
with the resultant increase of urban haze and the development of
valley fog during the weekend.

.LONG TERM (After 00Z Monday)...A pronounced upper ridge will be in
late Sunday at the start of the long term portion of the forecast.
The ridge is expected to shift eastward Tuesday as a series of
shortwave troughs cross the Interior West for the remainder of the

There are sufficient discrepancies on the orientation of this storm
track between the global models and ensembles. A portion of the
guidance has been shifting further south, which would bring the
threat of precipitation further south into northern and central
Utah, whereas a portion of the guidance is further north and would
indicate more of period of several brush by systems.

For now, have leaned a bit more toward the wetter solutions and have
introduced low end pops late Tuesday through Thursday. Confidence is
on the low end given the model discrepancies...but there is the
possibility of at least an active period, especially across northern


.AVIATION...Southerly winds are expected to continue at the SLC
terminal through the day today. Expect ceilings at or near 7000 feet
through the morning, with a gradual improvement after 19-21Z.





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