Severe Thunderstorm Warning 79, NWS Salt Lake City, UT

Area Forecast Discussion
National Weather Service Salt Lake City UT
1225 PM MDT Sun Aug 23 2026

.KEY MESSAGES, Issued 1151 AM MDT Sun Aug 23 2026...

- A Slight Risk (level 2/5) for severe thunderstorms is outlooked
  this afternoon and evening across much of northern Utah. There
  is a 10% chance of wind gusts in excess of 70 mph with these
  thunderstorms.

- There is a Marginal Risk (level 1/4) for excessive rainfall
  across most of the region through early next week.

- Thunderstorms will continue to impact the higher terrain and
  adjacent valleys through Wednesday. Another round of more
  widespread thunderstorms is increasing in likelihood for Friday
  into early next weekend.

&&

.DISCUSSION, Issued 1151 AM MDT Sun Aug 23 2026...
Strong to severe convection will develop this
afternoon and evening, with the highest probability of significant
impacts (10% chance of wind gusts in excess of 70 mph) across
northern Utah. A Slight Risk (level 2/5) for severe thunderstorms
has been issued for this area by the Storm Prediction Center.
Looking at the set-up, this morning's 12Z sounding at KSLC already
showed almost 1000 J/kg MUCAPE but with a fairly stout amount of
convective inhibition. Latest guidance suggests this effective cap
will erode by 20-21Z, allowing for robust convective development
across northern Utah. Mean HREF SBCAPE indicates a broad area of
values near to above around 1000-1500 J/kg across northern Utah
coincident with deep layer shear around 25-30 kts.

Weak surface convergence associated with a shortwave trough
passing to the north may help to organize convection into a
quasi-linear feature, though per typical in terrain, this is
difficult to discern in model fields. The latest few HRRR runs do
show a signature of an organized line of very strong outflow
shifting across the west desert and into the Wasatch Front
between 21Z and 01Z and then continuing to be quite strong into
the Uinta County, WY area by 02-03Z. Peak wind gusts in these runs
have increased to 55kts, but given the very steep lapse rates,
relatively high instability for the Great Basin, modest deep layer
shear and low LCLs, expect storms to be able to attain cold
pool/shear balance. Saturday's convective outflow peak was 80 mph
near Grassey on I-80...cant rule out a repeat somewhere along this
area of outflow winds this afternoon and evening.

For areas south of I-70, the heavy rain threat continues. While
HREF peak 1 hour rates have decreased over Saturday's values, net
available moisture has only decreased subtly. Expect any stronger
thunderstorms, especially those tied to terrain features and/or
training, to be capable of rainfall rates in excess of 0.50 inches
per hour. Will need to monitor for flash flood threat across much
of this area...especially for slot canyons, normally dry washes
and recent burn scars.

With the previously mentioned upper level trough passing to the
east Monday, the best chance for strong outflow winds will shift
to mainly the Utah/Idaho border region. Convection will become
increasingly tied to the higher terrain and adjacent valleys
through Wednesday...with only isolated convection expected
Thursday as high pressure brings a drying trend to most
locations.

However...with the tropical eastern Pacific remaining quite
active, at least a portion of ensemble members indicate the next
trough approaching the Pacific Northwest will assist in shifting
remnant tropical moisture into the Great Basin by Friday. This is
something to watch moving forward.

&&

.AVIATION, Issued 1151 AM MDT Sun Aug 23 2026...
KSLC, Issued 1151 AM MDT Sun Aug 23 2026...
A few thunderstorms will begin to develop over
the Salt Lake Valley after 20z or so, resulting in low confidence
in wind direction with any outflow winds. After 00z, a more
organized cluster of thunderstorms is looking more likely to
impact the terminal, bringing a chance for lightning, MVFR VIS due
to moderate- heavy rain, and gusty outflow winds. Winds could
even exceed 50kts out of the west (or become variable) as this
line moves through. There is still some uncertainty with the
timing of this cluster. Weaker showers will linger in the area
until 07z or so, with breezy easterly winds slowly becoming
lighter out of the southeast.

REST OF UTAH AND SOUTHWEST WYOMING...Scattered showers and
thunderstorms will continue to develop this afternoon across UT
and southwest WY, with lower chances at KCDC and KSGU. Any showers
will be capable of producing strong and erratic outflow winds,
with the strongest winds across northern UT/southwest WY. Here,
winds are more likely to briefly exceed 50kts or even 65kts near
the strongest storms. A more organized cluster of thunderstorms
will sweep through KTVY-KSLC-KOGD-KEVW between roughly 00-05z,
which may produce very strong winds, MVFR VIS due to moderate-
heavy rain, and lightning. There is still uncertainty with exact
timing of this cluster.

&&

.FIRE WEATHER...High pressure will remain across the Four-Corners
region through the next week. As an upper level low crosses
southern Canada into the northern Intermountain Region through
Monday, sufficient forcing for thunderstorms will continue. As a
result, strong to severe thunderstorms will impact much of
northern Utah this afternoon and evening. The most significant
threat will be strong outflow winds in excess of 60 mph, mainly
north of I-70. For locations south of I-70, strong outflow winds
up to 50 mph and very heavy rain will be the primary impacts from
thunderstorms.

Additional strong thunderstorms will develop Monday afternoon and
evening, but the threat of outflows in excess of 50 mph will
remain closer to the Utah/Idaho border. As high pressure builds
north and east in the wake of the upper level low Tuesday,
thunderstorms will become more confined to the higher terrain and
adjacent valleys through Thursday. A net drying trend will
continue, with most valleys see humidities fall to critical levels
by midweek. Another round of thunderstorms may impact more of the
state as early as Friday as another low pressure area impacts the
Pacific Northwest and pulls moisture from the tropical Pacific
northeastward into the Great Basin.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

PUBLIC...
AVIATION...
FIRE WEATHER...Kruse

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

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