649
FXUS65 KSLC 172141
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
341 PM MDT Tue Sep 17 2024

.SYNOPSIS...A fall-like airmass will settle into the region
Wednesday. High pressure will gradually shift into the area,
bringing warming temperatures. The next threat of precipitation
looks to be this weekend.

&&

.SHORT TERM (Through 12Z Thursday)...A cold upper level trough
continues to move across the region this afternoon, bringing
everything from severe thunderstorms to northern Utah, to
accumulating snow above 9000 feet across the northern mountains to
critical fire weather conditions across southeastern Utah.

In the wake of this system, temperatures will average around 10-15
degrees below normal across much of the region Wednesday. A few
locations still in growing seasons will see temperatures
approaching freezing including the Enterprise/Beryl Junction area,
normally cold spots of the Wasatch Back and the Loa and Bicknell
areas (which have already had several freezes). Patchy frost will
be possible across the Wasatch Back as well, so those with their
summer gardens still outdoors should be prepared to cover and/or
bring plants indoors.

An upper level low shifting south along the California Coast will
continue to slowly shift southward through Thursday. The end
result will be gradually amplifying upper level ridging into the
region, with warming temperatures (though still below normal
levels).

.LONG TERM (After 12Z Thursday), Issued 418 AM MDT...
Guidance has trended slightly drier and warmer for the long term
period as the trough that moves into the Great Basin on Thursday
begins to cut off and weaken as it moves further inland. Shortwave
ridging will amplify on Thursday ahead of the trough as it`s
positioned over central California. This will keep conditions
mostly dry with little cloud cover on Thursday as most of the
precipitation associated with the low remains over Nevada and
California. Additionally, high temperatures will rebound closer to
normal on Thursday with mid to upper 70s across most valleys and
mid 80s for far southern Utah.

As the trough shifts east on Friday the upper level low likely
becomes cutoff while filling in and weakening. With the center of
the low moving across northern Arizona, precipitation will be more
likely across central and southern Utah, but weak ascent will limit
the precipitation totals to generally less than 0.1". Temperatures
will cool a few degrees across the southern half of the CWA, but
remain largely unchanged across northern Utah/SW Wyoming given the
further proximity to the center of the low pressure system. This low
shifts further east on Saturday with a few diurnal showers possible
across eastern portions of the CWA.

After this low exits the region we will be left in a weak northwest
flow that will keep temperatures near normal for this time of year
making for optimal fall foliage peeping weather over the weekend.
Given the weak northwest flow regime we will be left in, guidance is
a bit indecisive on whether we introduce another trough (~23% of
members) or if we move into more of a ridging pattern (~77% of
members).

&&

.AVIATION...KSLC...Improving conditions are expected at the KSLC
terminal by 23z as the primary thunderstorm threat will shift east
of the area through that time. Additional shower activity moving
in from the west will remain possible through 02/03z, but will be
waning over time. West to northwest winds are expected to remain
in place through 03z, but brief east to northeast winds <10kts
will remain possible post thunderstorm passage during the
2230-2330 window.

.REST OF UTAH AND SOUTHWEST WYOMING...Shower and isolated storm
potential will remain in place over the northern TAF sites through
02/03z prior to waning overnight. VFR conditions are expected to
prevail for all areas, but brief reductions to MVFR conditions in
those isolated thunderstorms will remain possible through that
02/03z window in the north. Clear and dry conditions will remain
across southern Utah.

&&

.FIRE WEATHER...A fall-like pattern will build into the region
behind Tuesday`s storm system. Temperatures will average around 10
degrees below normal across much of the state Wednesday. A
gradual moderation as high pressure builds into the area will
bring temperatures closer to normal, but cooler than the last few
weeks. The next significant chance for precipitation looks to be
this weekend as an upper level low ejects across the region.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Red Flag Warning until 9 PM MDT this evening for UTZ489-494-498.

WY...None.
&&

$$

Kruse/Mahan/Merrill

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