Severe Thunderstorm Warning 24, NWS Salt Lake City, UT

Area Forecast Discussion
National Weather Service Salt Lake City UT
307 PM MDT Fri Jul 4 2025

.SYNOPSIS...Afternoon convection is expected across northern Utah
today, with potential for isolated severe wind and hail. Across
portions of southern and western Utah, dry and modestly breezy
conditions yield areas of critical fire weather conditions. High
pressure returns from the weekend onward.

&&

.DISCUSSION...Forecast for the day largely seems to be evolving as
anticipated. The forecast region remains placed within a
southwesterly flow regime, with a trough advancing towards the
forecast area through the PacNW. Faster flow associated with this
trough is resulting in an enhancement to shear across northern
Utah, with SPC mesoanalysis analyzing widespread effective shear
values around 35 to 50 kts. Ongoing daytime heating is leading to
destabilization, and while dew points in the upper 40s to low 50s
in northern Utah is actually relatively moist for this time of
year, boundary layer remains well mixed enough for DCAPE values
around 900 to 1400 J/kg. As a result, the northern third of the
forecast area remains placed in a categorical Marginal Risk (level
1 of 5) for severe weather this afternoon and evening. In
addition to frequent lightning, the primary threats would be
potential for hail up to an inch or so and wind gusts up to or in
excess of 58 mph. Initial convection would likely tend to yield
more of a combined hail/wind threat, with subsequent propagation
of outflow dominated clusters increasing the wind threat.

Cumulus field this afternoon continues to become further
agitated, and area radars are picking up on strengthening
convection especially near the UT/NV border, with some slower
maturing isolated convection elsewhere across the northern
portions of the area. Models have handled this well so far, and
suggest we'll especially see the activity near the UT/NV border
mature in the favorable environment, with clusters and associated
outflows then propagating eastward in time. Currently, most likely
timing of stronger wind related impacts along the populated urban
corridor of the Wasatch Front is 5pm to 8pm time frame. Models
then support the outflow/storms quickly continuing
east/northeastward through the terrain and eventually into/through
Uinta County, Wyoming. While not everywhere will necessarily see
the strong winds, given the amount of ongoing outdoor events,
those hosting/attending should keep an eye on how things evolve
over the next few hours. Aside from where models show decent
consensus on the aforementioned organized convective potential,
elsewhere the more isolated to scattered convection that continues
to mature will also pose a threat of lightning, gusty outflow
winds, and small hail. Models show potential for a few lingering
thundershowers following the stronger push, but largely suggest
coverage/strength trends downward, especially after 10pm or so.

Across southern Utah, drier air is resulting in much more minimal
precipitation chances Friday. Conversely, moderately strong
southwesterly flow in combination with the dry conditions is
resulting in localized areas of critical fire weather conditions,
especially across portions of the West Desert, southwest Utah, and
southern Utah.

A retrograding low off the California coast will initially help
keep a ridge extending through the Desert Southwest and towards
the Four Corners region a bit shunted/flattened away. As such,
will only see a slight upward trend in temperatures through the
weekend, and with little moisture remaining, minimal precipitation
chances. From Monday on through the week the ridge strengthens
and continues to build into the area. Increasingly anomalous H7
temps associated with the ridge will then drive a more marked
warmup pushing afternoon highs to around 7-15F above
climatological normal. While it appears forecast temps nudged down
slightly in comparison to prior forecasts, it still is sufficient
for increasing HeatRisk, and any nudge back upwards depending on
how the forecast trends could yield headlines later on.

&&

.AVIATION...KSLC... Flow should generally remain out of the
northwest this afternoon with the exception of localized outflow
winds from thunderstorms. Thunderstorms are possible this
afternoon into the evening from around 21-01z. Strong to severe
storms are possible with gusts in excess of 58mph and marginally
severe hail. Around 03z, southeasterly flow should settle in
before becoming northwesterly again tomorrow around 15z.

.AVIATION...REST OF UTAH AND SOUTHWEST WYOMING... Thunderstorms are
possible across all of our northern UT TAF sites this afternoon
from around 21z through 01z. Strong to severe gusts and marginally
severe hail are possible with these storms. Additionally, IFR
conditions may be possible. Following 01-02z, VFR conditions will
prevail.

&&

.FIRE WEATHER...Moisture has continued to scour out across areas of
western and southern Utah today, with broad scale weather pattern
supporting modestly breezy southwesterly winds. As a result, some
localized areas of critical fire weather conditions are noted.
Winds will gradually decrease Friday evening into the overnight,
helping to abate these conditions.

Across the northern half to third of Utah, moisture remains in
sufficient quantities to help develop isolated to scattered
showers and thunderstorms. Conditions are favorable as well for a
few stronger storms capable of frequent lightning, gusty erratic
outflow winds, small hail, and brief moderate rain. These gusty
erratic outflow winds, potentially in excess of 50 mph, may
propagate further away from area thunderstorms as well.

High pressure becomes the dominant forecast feature this weekend
on into the upcoming week. This will result in a return of
widespread dry conditions and a warming trend. While widespread
gusty conditions aren't expected at this time, any locally windier
spots will see potential for elevated fire weather conditions
given the low daytime humidity and poor overnight recoveries.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Red Flag Warning until 9 PM MDT this evening for UTZ492-495-497-
     498.

WY...None.
&&

SHORT TERM...Warthen
LONG TERM...Warthen
AVIATION...Worster
FIRE WEATHER...Warthen

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
333 PM MDT Fri Jul 4 2025

UTZ108-110>112-042215-
Wasatch Back UT-Western Uinta Mountains UT-Wasatch Mountains I-
80 North UT-Wasatch Mountains South of I-80 UT-
333 PM MDT Fri Jul 4 2025

...A strong thunderstorm will impact portions of east central Salt
Lake, south central Morgan and west central Summit Counties through
415 PM MDT
...

At 332 PM MDT, Doppler radar was tracking a strong thunderstorm over
Summit Park, or 8 miles northwest of Park City, moving northeast at
30 mph.

HAZARD...Wind gusts up to 50 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Coalville, Summit Park, East Canyon State Park, Wanship, North
Snyderville Basin, Mill Creek Canyon, Big Cottonwood Canyon, South
Snyderville Basin, Hoytsville, Echo, Parleys Summit, Echo Reservoir,
Kimball Junction, and Rockport State Park.

This includes the following highways...
 Interstate 84 between mile markers 118 and 119.
 Interstate 80 in Utah between mile markers 134 and 146, and between
mile markers 149 and 168.
 US Route 40 near mile marker 0.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4064 11164 4070 11175 4100 11152 4095 11117
TIME...MOT...LOC 2132Z 221DEG 26KT 4075 11160

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

HM