Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 182151
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
351 PM MDT Mon Sep 18 2017

.SYNOPSIS...A cold front will cross northern Utah tonight through
Tuesday. A stronger trough will move into Utah starting late
Wednesday night and will linger over the area through the upcoming
weekend.

&&

.SHORT TERM (Through 00z Thursday)...Conditions are breezy across
much of the forecast area today ahead of a storm system approaching
from the Pacific Northwest. The warming trend continues with maxes
running near or just above seasonal normals across Utah and
southwest Wyoming. Some cumulus has developed over the higher
terrain, and some high clouds are starting to make their way into
northwest Utah as the storm system approaches.

The trough is expected to graze northern portions of the forecast
area tonight into tomorrow, bringing a cold front as far south as
central Utah. Behind the front, maxes are expected to run up to 20F
below today`s observed values, up to around 15F below seasonal
normals. A bit of precipitation is expected over northern Utah and
southwest Wyoming in association with the system, primarily tonight
into tomorrow morning with best coverage over the higher terrain.
Moisture is not particularly impressive, but there is good jet
support with the trough. Overall, have raised POPs just a bit
tonight into tomorrow morning with increasing confidence. Ahead of
the front over southern Utah, temperatures will be similar to today
with continued breezy southwest flow.

Associated precip with the trough should taper off tomorrow evening
as the trough exits, with southerly flow increasing over the area
once again during the day Wednesday as the next storm in the series
approaches. The area will also see a quick rebound in temperatures,
with maxes climbing near seasonal normals again across Utah and
southwest Wyoming.

.LONG TERM (After 00z Thursday)...The latest GFS model run has
slowed down the cold front progression similar to the EC solution,
however it still remains lagging to the EC with the frontal
passage. Frontogenesis still looks good from 12z through 18z- 20z
Thursday into the Wasatch Front. The convergent zone is best
depicted from the northwest into the Wasatch Front by 06z Friday.
The baroclinic zone tightens as it treks southeast through Utah
Thursday and pushes south and east covering the entire state of
Utah by Saturday morning.

700mb temperatures drop significantly with the cold front
dropping into Utah Thursday. From +8C before frontal passage to
-2C Thursday morning to -4C by Friday. The cold air will remain in
 place through the weekend before the trough completely departs
 the region. Snow levels are forecast to drop down to near 6,500
 feet across northern and north central Utah. With a swath of
 precip associated with the frontal passage Thursday, most lower
 elevation areas will see rain showers across the state. Mountains
 will see rain to snow through the night Friday as temperatures
 continue to drop. And with the slow progression of the upper
 level trough and associated cold front, the precipitation is
 expected to end by Saturday afternoon across the far eastern
 portions of Utah.

With the upper level low becoming elongated and stretched late in
the weekend and somewhat of a split trough feature, a strong jet
dives southward through the Great Basin helping to eject this
trough farther to the east.

&&

.AVIATION...Winds at the SLC terminal could be inconsistent at times
through the evening and overnight hours due to a cold front and
showers moving through northern Utah. The most likely scenario is
southerly winds persisting until winds switch to the west-northwest
around 09-13Z, but there is a slight chance that brief west-
northwest winds could develop as early as 02Z.

&&

.FIRE WEATHER...The district is seeing dry and warm conditions with
gusty winds today ahead of an approaching storm system. This
system will graze northern Utah tonight into tomorrow, bringing a
cold front through northern and central Utah. Southern Utah will
stay breezy ahead of the front with temperatures near seasonal
normals. Winds will ramp up again across the entire district on
Wednesday as temperatures warm. A stronger storm system will
follow for Wednesday night into Thursday, bringing valley rain and
mountain snow to much of the district along with a reinforcing
shot of cold air. Cool and unsettled conditions are expected to
continue through at least the upcoming weekend.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

SHORT TERM...Traphagan
LONG TERM...Dewey
AVIATION...Schoening
FIRE WEATHER...Traphagan

For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity

For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php



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