525
FXUS65 KSLC 161018
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
418 AM MDT Mon Sep 16 2024

.SYNOPSIS...Southerly flow will strengthen across the region
today ahead of an approaching storm system. The cold front
associated with this system will cross the region tonight,
ushering much cooler air into the area for Tuesday. The main
storm system will move through the region Tuesday, with cool and
unsettled weather lingering through the remainder of the week.

&&

.SHORT TERM (Through 12Z Wednesday)...An upper low spinning over
northern California this morning is inducing a deep layer
southerly flow downstream across the forecast area. A shortwave
currently rounding the base of the upper low will lift across
eastern NV through the day today as it pivots around the upstream
low. Pressure falls ahead of this feature will strengthen the wind
field across the forecast area, particularly across west central
and southwest Utah where gusts will exceed 45 mph at times. Winds
across areas further east, including the Sevier Valley and
Panguitch/Bryce Canyon areas will also see enhanced southerly
winds, however max HREF gusts indicate these should remain a
little below the advisory threshold of 45 mph, and thus have held
off on any wind headlines for these areas.

The shortwave lifting through eastern Nevada will also increase
large scale ascent across the forecast area this afternoon and
evening. Moisture/instability will be most abundant across
northern and eastern Utah, where showers and thunderstorms will
develop by early afternoon. Deep layer shear will support
organized convection, and a few storms may approach severe limits
with gusty winds the main threat. Locally heavy rain will also be
possible although any threat for flash flooding will require
training as storm motions will be in excess of 40 mph.

As the approaching upper low spreads across NV this evening
through tonight, the associated cold front will lift northeast
across the forecast area, ushering much cooler air into the
region. Temperatures will trend 15-20 degrees cooler across
northern Utah Tuesday, keeping temperatures confined to the 60s
across northern valleys. The cooldown will be a bit more muted
across southern Utah, where temps will trend 6-10 degrees cooler.

As the upper trough axis lifts through the forecast area, fairly
widespread precipitation will develop across northern Utah Tuesday
morning through mid afternoon. Snow levels near 9000 feet will
likely result in some minor accumulations across the upper
elevations of the Wasatch/Uintas during the day Tuesday.

.LONG TERM (After 12Z Wednesday)...A cool and wet pattern will
remain in place for the ladder half of the week as a weakening upper
level low approaches the Great Basin, replacing the early week low
that will be exiting to the northeast. Temperatures will be running
~10 degrees below normal areawide for this time of year. Stratiform
rain will transition to more of a diurnally driven showery precip
regime (with less coverage) as this low shifts east. There still
remains some uncertainty regarding the pattern following the
departure of the aforementioned low. ~37% of guidance brings another
trough through the Great Basin that would reinforce the cool airmass
and lead to more precipitation. However, the remaining ensemble
members suggest that ridging will build back into the area that
would result in drier and warmer conditions.

By Wednesday morning an upper level low will be centered off the
coast of northern California. Across the Great Basin, a cold front
ahead of the trailing low pressure will move through the area with
increasing cloud cover that will inhibit temperatures from warming
much throughout the day. As the low slides down the west coast
northern Utah will be positioned on the left exit region of ~100kt
jet. This will help to increase ascent across northern Utah/SW
Wyoming resulting in some showery precipitation. By Thursday this
low starts to progress inland while filling in and weakening as it
does so. Even still, PVA will help to enhance lift across most of
the CWA on Thursday and Friday resulting in more widespread light
stratiform precipitation. As the cold core moves over the Great
Basin snow levels will generally be ~10kft with some light snow
accumulations across the highest elevations.

This low exits the area to the northeast by the weekend, however
steep lapse rates and lingering moisture left in the wake of the
low will help to spark some diurnal showers Saturday and
potentially Sunday across northern Utah and SW Wyoming. These will
likely be spotty showers that could contain some graupel and
gusty winds. As mentioned, the pattern following this exiting low
remains in question as a minority of ensemble members bring in
another trough, whereas most begin a drying and warming trend
thanks to a ridge building back into the area.

&&

.AVIATION...KSLC...VFR conditions will persist for the KSLC terminal
through the period. Southerly winds will increased as the day
progresses with gusts ~25kts during the afternoon ahead of an
approaching low. Showers and isolated convection develop later in
the afternoon with the potential for gusty erratic outflow winds.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will persist
for the airspace through the period. Southerly winds will be
increasing ahead of an approaching low. This will create gusty
southerly winds during the day along with showery convective
activity increasing across the north during the afternoon. These
showers could produce gusty outflow winds along with frequent
lightning.

&&

.FIRE WEATHER...Southerly flow will strengthen across the region
today ahead of an approaching storm system. These winds will gust
in excess of 30 mph this afternoon across much of central and
southern Utah, and in excess of 45 mph across zones 492 and 495.
These winds coupled with afternoon RH in the upper teens to low
20% range will result in near critical fire weather conditions
this afternoon and early evening over much of central and southern
Utah.

As the approaching storm system moves into the Great Basin today,
showers and thunderstorms will increase in coverage across
northern as well as eastern Utah. Some of these thunderstorms may
become strong, and be capable of locally heavy rain in addition to
strong outflow winds and lightning. The cold front associated
with this storm system will push through the region tonight,
ushering much cooler air into the region Tuesday. Temperatures
across northern Utah will trend 15 to 20 degrees cooler Tuesday,
while temperatures across central and southern Utah trend 6-10
degrees cooler. The passing storm system will bring fairly
widespread precipitation to northern Utah Monday night into
Tuesday, with some accumulating snow possible above 9000 feet.
Drier air will remain in place across central and southern Utah,
and combined with gusty winds will result in near critical fire
weather conditions across zones 489, 494 and 498 Tuesday
afternoon. This cooler air will remain in place through the
remainder of the week with another storm system passing through
the region during the latter half of the week.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory from noon today to 9 PM MDT this evening for
     UTZ115-122.

WY...None.
&&

$$

SHORT TERM...
LONG TERM...
AVIATION...
FIRE WEATHER...

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