Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 241137

Area Forecast Discussion
National Weather Service Salt Lake City UT
537 AM MDT Sun Sep 24 2017

.SYNOPSIS...An upper low over Utah will track northeast today,
keeping cool and wet weather in place. Another upper low will likely
impact mainly southern and eastern Utah during the second half of
the week.


.SHORT TERM (THROUGH 12Z WEDNESDAY)...The center of the upper low
over the area is noted just south of central Utah this morning and
is expected to slowly lift northeast through the day. Abundant
moisture associated with this storm continues to produce widespread
valley rain and mountain snow across the area. Precipitation remains
more convective along the baroclinic zone along the eastern edge of
the forecast area, and this is associated with some thunderstorms
which should shift east out of the area by mid-morning. Otherwise,
stratiform precipitation is noted in the wraparound across western
Utah where warm advection is occurring aloft.

A relative lull in precipitation is currently occurring along the
Wasatch Front, but with the flow aloft turning more northwesterly as
the upper low lifts into northeast Utah this afternoon,
precipitation should fill in once again. Otherwise, precipitation
will tend to taper off from south to north this afternoon and into
the overnight hours. The clouds and precipitation in place should
guarantee cool daytime highs across most of the area today.

Winter Weather Advisories remain in place across the Wasatch,
Uintas, and central Utah mountains. Snow levels have occasionally
reached the higher valleys, particularly those 6000ft or higher, and
Southwest Wyoming has been seeing mostly snow. Although
accumulations are likely occurring on the higher passes along I-80
in southwest Wyoming, most of the lower portions of the route appear
to have seen little accumulation thus far per WYDOT cams. As a
result, have opted not to add an advisory for this zone. Another
round of heavier snow is expected there later today, but snow may
continue to have difficulty accumulating as it will be during the
daylight hours.

Although precipitation will wind down tonight, there will be a
potential for stratus or perhaps some fog to linger across portions
of northern and portions of central Utah. Overnight mins will be
cooler in some areas, but the lingering cloud cover should prevent a
freeze for most lower valleys.

Although the low exits the area, a cyclonic flow aloft will remain
in place through midweek as an upper jet dives south through the
West Coast states. This jet will drop the next weather disturbance
into western Arizona where it will end up as a closed low Tuesday
night. This low will be too far south to affect the forecast area
initially, and will not prevent a general warming and drying trend
for Monday and Tuesday.

.LONG TERM (After 12Z Wednesday)...The closed low over Arizona
eventually tracks northeastward, perhaps impacting central and
southern Utah by Thursday into the first part of the weekend.
Forecast certainty is limited in this timeframe as evidenced by
ensembles showing a wide spread in the amplitude and track of the
low. That said, nearly all of the GEFS members show a closed low in
vicinity, so it appears likely that such a feature will develop, the
question is how strong and where.

For now, have the kept the forecast largely unchanged for the latter
part of next week, which means a chance of showers and perhaps
thunderstorms from around the central mountains of utah eastward and
from the Uintas southward. Northern Utah would be more of a longshot
to see showers out of this disturbance, but it`s not out of the
question. Otherwise, expect temperatures to warm to around normal
for northern Utah, with warming less certain over southern Utah due
to the possible closed low in vicinity and related precipitation

Peeking further ahead, the GFS and ECMWF models are in good
agreement that a Western US ridge is on the way for at least the 7-
10 day forecast period, meaning warmer temperatures and quiet
weather are probable for next weekend and into the following week.


.AVIATION...Intermittent MVFR conditions expected today at the SLC
terminal as a low pressure system will bring periods of rain and
lower cigs at times through the day. The best chance for multiple
hours of MVFR cigs and steady rain will be around 17z to 01Z.
Partial clearing is likely tonight, with a 30% chance of low stratus
and fog forming and associated MVFR to IFR cigs.


UT...Winter Weather Advisory until midnight MDT tonight for

     Winter Weather Advisory until 4 PM MDT this afternoon for UTZ517.



Cheng/Van Cleave

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