Severe Thunderstorm Warning 25, 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
341 PM MDT Fri Jul 4 2025

UTZ101-042215-
Great Salt Lake Desert and Mountains UT-
341 PM MDT Fri Jul 4 2025

...Strong thunderstorms will impact portions of south central Box
Elder and northwestern Tooele Counties through 415 PM MDT
...

At 340 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 23 miles west of Great Salt Lake North of the
Causeway to 10 miles southeast of Utah Test and Training Range North
to 10 miles south of Utah Test and Training Range South. Movement was
east at 35 mph.

HAZARD...Wind gusts up to 50 mph and pea size 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...
Knolls, Clive, Utah Test and Training Range North, Utah Test and
Training Range South, Great Salt Lake North of the Causeway,
Lakeside, and Gunnison Island.

This includes Interstate 80 in Utah between mile markers 37 and 67.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4158 11285 4100 11271 4040 11297 4033 11366
      4095 11319 4144 11336
TIME...MOT...LOC 2140Z 253DEG 31KT 4137 11320 4095 11305 4036 11349

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH

HM

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