093
FXUS65 KSLC 092155
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
355 PM MDT Tue Sep 9 2025
.SYNOPSIS...A slow moving upper level trough will help to bring
increasingly strong winds and largely dry conditions into the
region Wednesday afternoon, with critical fire weather conditions
across a portion of western Utah. Cooling temperatures and
increasing chances for precipitation arrive during the second half
of the week, with an active pattern continuing into next week.
&&
.SHORT TERM (Through 12Z/6AM Thursday)...A deep, upper-level
trough currently positioned over the U.S. West Coast will be the
main synoptic feature and driver of any impactful weather over the
next week. Tomorrow, this trough will slowly begin shifting inland
and bring an uptick in winds across Utah and southwest Wyoming.
Key Messages and Impacts:
- Strong south to southwest winds spread across Utah tomorrow,
with the strongest winds expected across Utah`s West Desert.
Winds are expected to gust upwards of 35 to 40 mph during the
afternoon hours.
- Strong winds will pair with dry conditions at the surface to
create elevated to critical fire weather conditions across Utah
between 11AM and 9PM on Wednesday.
Tuesday afternoon satellite analysis shows a shield of cloud cover
departing the northern and eastern portions of the CWA with
clearing in the wake, indicative of a weak ejecting shortwave
trough moving through the region. Have seen some isolated stronger
convection this afternoon, likely aided by this departing
shortwave. Anticipate ongoing strong isolated convection to
decrease over the next couple of hours, with lingering isolated
weak convection remaining possible across the northeast portion of
the CWA through the early overnight period.
Moving into Wednesday, the aforementioned trough will slowly shift
inland. Overhead, winds will begin to see a notable increase in
intensity which will help to drive a breezy day across much of
Utah and southwest Wyoming, particularly during the afternoon
hours. With little change expected in the lower level atmospheric
moisture, afternoon humidity will go largely unchanged as compared
to Tuesday... remaining fairly dry. These stronger winds will
combine with the dry conditions and bring elevated to critical
fire weather conditions across western Utah and the lower lying
valleys of southeast Utah. A Red Flag Warning has been issued for
a portion of Utah`s West Desert. See Fire Weather section of the
AFD for more information.
Aside from the fire weather concerns for Wednesday, temperatures
are expected to go relatively unchanged as no major warm or cold
advection is expected over the eastern Great Basin region. With
mid-level moisture remaining draped over the I-15 corridor
(roughly), would anticipate a chance for isolated high-based
showers and thunderstorms tomorrow afternoon, primarily over
significant terrain features and their adjacent valley areas. No
significant flood threat is expected for tomorrow, however, a
rouge strong thunderstorm could carry potential to cause issues in
a recent burn scar or slot canyon area.
.LONG TERM (After 12Z/6AM Thursday), Issued at 329AM MDT...As the
upper level low reaches the Interior West Thursday with the low
centered somewhere around the Idaho/Nevada/Oregon triple point,
the majority of the ensemble members shift a dry slot into
portions of western and southern Utah. Meanwhile, the majority of
members support at least light precipitation across portions of
northern and eastern Utah Friday afternoon and evening. It should
be noted however that the ensemble members have shifted over the
last few runs toward a more pronounced dry slot across
Utah...which may eventually eat away at any precipitation chances
even for portions of northern Utah.
By Saturday, the upper level low will finally be kicking out the
region as another upper level trough approaches the Pacific Coast.
Depending on how fast shortwave ridging crosses the state, lapse
rates look steep enough to allow for convection across portions of
northern and eastern Utah. And this progressive, fall-like pattern
looks to continue beyond the weekend.
&&
.AVIATION...KSLC...VFR conditions continue tonight/tomorrow with
gusty southerly winds at times and periods of scattered high clouds.
While gusts should decrease by 0Z this evening, steady south to
southeast winds over 10kts will persist through the night. Another
round of gusty southerly winds will develop by 15Z tomorrow morning.
.REST OF UTAH AND SOUTHWEST WYOMING...Isolated showers and
thunderstorms from roughly a KEVW to KPUC line eastward this
afternoon/evening will be capable of MVFR conditions and gusty
outflow winds. Otherwise, VFR conditions are expected for the region
tonight and tomorrow. Generally southerly winds are expected
throughout the period, becoming gusty tomorrow morning around 20-30
knots. The strongest winds will be west of I-15 over the West
Deserts.
&&
.FIRE WEATHER...A deep low pressure system currently centered over the U.S. West Coast
will slowly shift inland through the overnight hours. As a
result, an increase in south to southwesterly flow is expected
across Utah during the day on Wednesday. Coincident with the
uptick in southerly winds, dry air in the lower levels of the
atmosphere will be maintained and help to drive another day with
afternoon minimum relative humidity ranging from 10 to 25 percent
in the lower elevations across Utah. For the higher elevations,
minimum humidity on Wednesday is expected to range from 25 to 45
percent, with the higher end of the range anticipated for
elevations above 10,000ft. For the lower lying areas across
western Utah, southerly winds with gusts upwards of 35 to 40 mph
will pair with critically low relative humidity during the
afternoon hours. A Red Flag Warning has been issued where humidity
is lowest and winds are highest (UT478 and UT492). For
southwestern Utah and the lower elevations of eastern Utah,
elevated fire weather conditions will be in place as winds gust
upwards of 25-35 mph but afternoon humidity will range from 15 to
20 percent.
The aforementioned area of low pressure will gradually shift over
the eastern Great Basin region late in the week, bringing an
overall cooling and wetting trend across the northern half of
Utah. While a similar cooling trend is expected across southern
Utah, significant improvement to relative humidity is not
expected. In fact, continued breezy southwest winds will be
maintained across southern and eastern Utah through at least
Friday and will help to maintain elevated fire weather conditions.
Temporary drying is anticipated late in the weekend, however,
active weather may return by early next week.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Red Flag Warning from 11 AM to 9 PM MDT Wednesday for UTZ478-492.
WY...None.
&&
$$
SHORT TERM...Webber
LONG TERM...Wilson
AVIATION...Van Cleave
FIRE WEATHER...Webber
For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity
