Severe Thunderstorm Warning 29, NWS Salt Lake City, UT

Area Forecast Discussion
National Weather Service Salt Lake City UT
328 PM MDT Mon Jul 21 2025

.SYNOPSIS...Limited amounts of moisture maintain isolated to
scattered daytime convection chances, especially across southern
Utah and elsewhere along Utah's high terrain. From midweek onward,
a drying and warming trend is largely expected.

&&

.DISCUSSION...
Key Messages
* Critical Fire Weather conditions continue across northwest Utah
  this afternoon through this evening due to low humidity (10-15%)
  and gusty winds largely in the 30-40 mph wind range.
* Isolated Flash Flooding is Possible (risk level 2 of 4) through
  this evening, for southern and eastern Utah, mainly for slot
  canyons, dry washes and burn scars.
* Critical Fire Weather conditions return late in the week into
  the weekend as much drier air moves into the area this week and
  combines with increasing winds into the weekend.

For the critical fire weather conditions today, a trough over the
Pacific Northwest is helping to develop an area of surface low
pressure over the West Desert of Utah today with well-aligned
southwesterly flow aloft. The combination of a tight surface
pressure gradient and an extremely well mixed boundary layer to at
least 500 mb, is resulting in widespread wind gusts in the 30-40
mph range across northwest Utah. This is also ensuring low
humidity across the axis of winds with RH values largely falling
into the 10-15 percent range. Winds have been elevated across the
region even back to last night, which resulted in an overnight low
at KSLC of 80 degrees. Should that hold through midnight (which
it should), that would be a daily record for a warm low
temperature (previous record is 79 degrees). With winds staying
elevated again tonight as the surface low drifts eastward across
northern Utah, expect areas of poor overnight recoveries in RH and
warm overnight low temperatures again.

Also today, there remains an axis of moisture from southwest to
northeast across Utah, and into eastern Utah. PW values ahead of
the moisture gradient across northwest Utah, are largely in the
0.8 to 1 inch range. However, with morning cloud cover and showers
along this axis of moisture, CAPE values have been limited today,
which is helping to limit the threat of flash flooding. That
said, by later in the afternoon, pockets of enhanced CAPE could
support an isolated stronger storm or two would would be capable
of localized flash flooding. Thus the Flash Flood Potential
rating remains at Possible (risk level 2 of 4) through this
afternoon and evening for slot canyons, dry washes and burn scars
in southern and eastern Utah.

Looking at the week ahead, a drying trend will continue through
the week, which will act to limit the coverage of any showers and
thunderstorms. Min RH values will drop into the single digits and
low teens by Thursday into the weekend with poor overnight
recovery as well. Forecast confidence remains high that cut off
low along the California coast will induce increasing
southwesterly flow across the Great Basin by Friday and into the
weekend. Overall high temperatures will remain near-normal through
the forecast period, but with below normal precipitation and a
lack of any good signal for monsoon moisture through the end of
July and into early August.

&&

.AVIATION...KSLC...Gusty conditions are expected to persist across
the terminal this afternoon and throughout the evening hours. Gusts
to around 35kts out of the southeast will persist through 02z before
diminishing somewhat to around 20kts. There is a chance we remain
gustier than 20kts, though considerable uncertainty exists.
Additionally, a chance for gusty showers exists from 22-02z at the
terminal.

.REST OF UTAH AND SOUTHWEST WYOMING...Gusty conditions will persist
across all sites this afternoon and evening with a chance for gusty
showers and thunderstorms this evening across the majority of our
sites. Gusts will carry over into the evening, particularly across
our Wasatch Front sites. Gusts are expected to subside shortly
following sunrise tomorrow morning.

&&

.FIRE WEATHER...
A low pressure system moving through the Pacific Northwest this
afternoon is acting to increase southwesterly flow across
northwest Utah where drier air is in place. The combination of
wind and low humidity is resulting in fairly widespread Red Flag
conditions across zone 478 this afternoon, with even some
localized wind gusts as high as 50 mph this afternoon. Winds will
diminish but stay overall elevated across northern Utah tonight,
along with areas of poor overnight recovery. Elsewhere, areas of
near-critial fire weather conditions will continue, especially
across the Northern Utah Mountains, and west central Utah.
Additional moisture in place across southern Utah and eastern Utah
will make for isolated shower and thunderstorms which could
result in gusty and erratic outflow winds along with low chance of
isolated flash flooding for any stronger storms that develop.

Winds will trend lighter Tuesday and Wednesday, along with the
start of a drying trend. This will bring a downward trend in
shower and thunderstorm coverage, becoming much more limited and
then ending later in the week. However, by Thursday into the
weekend, the drying trend will start to push RH values into the
single digits along with poor overnight recoveries. By Friday
winds will start to increase ahead of the next weather system,
with the strongest winds expected Saturday into Sunday. This will
bring a return to critical fire weather conditions by the end of
the week into the weekend.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Red Flag Warning until 9 PM MDT this evening for UTZ478.

WY...Red Flag Warning until 8 PM MDT this evening for WYZ277.

&&

PUBLIC...Church
AVIATION...Worster
FIRE WEATHER...Church

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

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Special Weather Statement
National Weather Service Salt Lake City UT
747 PM MDT Mon Jul 21 2025

UTZ101-103-104-220215-
Eastern Box Elder County UT-Northern Wasatch Front UT-
Great Salt Lake Desert and Mountains UT-
747 PM MDT Mon Jul 21 2025

...A strong thunderstorm with gusty outflow winds will impact
portions of southwestern Weber, southeastern Box Elder, northwestern
Davis and northeastern Tooele Counties through 815 PM MDT
...

At 747 PM MDT, Doppler radar was tracking a strong thunderstorm with
gusty outflow winds 10 miles west of Hooper, or 17 miles west of
Hill Air Force Base, moving northeast at 35 mph.

HAZARD...Wind gusts of 50 to 55 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Roy, Clearfield, Syracuse, Clinton, Hooper, Great Salt Lake South of
the Causeway, West Haven, West Point, West Warren, and Antelope
Island State Park.

This storm will be capable of producing strong gusty winds on the
Great Salt Lake. This will lead to a sudden increase in waves and
very choppy waters which will result in hazardous boating conditions.
Boaters are urged to seek safe harbor if possible.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4095 11242 4116 11261 4147 11226 4108 11201
TIME...MOT...LOC 0147Z 225DEG 30KT 4117 11233

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...55 MPH

JAC