Severe Thunderstorm Warning 89, NWS Salt Lake City, UT

Area Forecast Discussion
National Weather Service Salt Lake City UT
1250 PM MDT Fri Aug 28 2026

.KEY MESSAGES, Issued 1126 AM MDT Fri Aug 28 2026...

- Scattered showers and thunderstorms will once again impact Utah
  and southwest Wyoming today, with isolated strong to severe
  thunderstorms possible for much of the area this afternoon into
  the early evening. The main threat will be gusty winds to 60
  mph.

- The potential for strong to severe thunderstorms over northern
  portions of the area will increase tomorrow in association with
  a passing cold front, with strong, gusty winds continuing to be
  the main threat.

- With increasing moisture and instability, the threat of flash
  flooding for southern Utah will be elevated both today and
  Saturday. Heavy rain from strong storms over northern Utah will
  also bring isolated flash flooding tonight into tomorrow.

- An active pattern will continue through at least the first half
  of next week.

&&

.DISCUSSION, Issued 1126 AM MDT Fri Aug 28 2026...
Interesting situation setting up for the next few
days with a Pacific Northwest trough moving onshore this morning.
Our ever-present ridge is centered over the Four Corners and the
squeeze between these two features has brought in increase in
southwesterly flow. In this flow, an already moist airmass has
gained moisture, with satellite derived PWs sitting in the 0.8 to
1.0 inch range.

A frontal boundary associated with the Pacific Northwest trough
is stretched across Nevada and Idaho, approaching the northwest
corner of Utah. This has been the focus for showers and a few
embedded thunderstorms this morning, with some additional
generally weak activity having developed ahead of the boundary in
central Utah. The presence of the boundary and the upper jet with
the trough will only add to instability today, which has led the
SPC to put much of the area under a marginal risk for severe
thunderstorms, with gusty winds being the primary threat. With
more widespread coverage of showers and thunderstorms, southern
Utah will see an elevated risk of flash flooding this afternoon,
with prone areas like burn scars and slot canyons behind the main
impact areas.

As the ridge continues eastward out of the area, this will allow
the frontal boundary to move farther into northern Utah and
southwest Wyoming tonight into tomorrow morning, with guidance
continuing to indicate a banded feature along it, bringing good
coverage of showers across much of northern Utah and southwest
Wyoming overnight and into the morning. Embedded stronger showers
could be accompanied by heavy rainfall, so will need to monitor
areas of concern for northern Utah including burn scars and urban
areas with poor drainage.

As the front starts to outrun its upper level support, it is
expected to weaken and stall somewhat in the vicinity of a KELY-
KEVW line late Saturday morning/early Saturday afternoon. With
deep moisture and additional instability provided both from the
main trough and the stalled boundary will bring fairly widespread
coverage of showers and thunderstorms, and ample instability for
scattered coverage of strong to severe cells. Strong, gusty winds
will again be the primary threat but these cells will also be
capable of producing at least small hail along with very heavy
rainfall, bringing an enhanced threat of flooding for northern
Utah as well. The approach of the main trough later Saturday
afternoon into Saturday evening will only improve instability and
is expected to keep showers going, particularly along the frontal
boundary, Saturday night into Sunday morning. This long duration
period of showers only adds to the potential for flooding over
northern portions of the forecast area.

After Sunday morning the main trough, having just made its closest
approach to northern Utah, is forecast to track back northeast.
Overall, this will bring a gradual decrease in coverage of
convection during the day, but this will also get the frontal
boundary moving again, pushing it into southeast Utah during the
afternoon. Thus, there is a high chance that Sunday afternoon will
be the most active period in terms of convection for portions of
southeast Utah, and therefore it is looking increasingly likely
that the highest flash flood threat for that area could be during
this time, with at least some convection continuing along the
boundary during the evening and overnight hours.

Though the Pacific Northwest trough is expected to be well away
from the area by Monday morning, most guidance indicates
convection continuing, particularly for southern Utah, on Monday
as an influx of shortwave energy combines with the existing
boundary and deep moisture, so there is a chance that the
heightened flooding threat for southeast Utah will continue into
much of Monday. Thereafter, with the ridge out of the picture, the
storm track will open up, allowing a variety of troughs to impact
the west during the upcoming week. However, guidance is starting
to converge on solutions that keep many of these features north of
the area, which would bring in drier air and limit the potential
for additional precipitation. Still, the much cooler temperatures
from this weekend's system (highs 5-10F below seasonal normals)
are expected to stick around for much of the upcoming week.

&&

.AVIATION, Issued 1133 AM MDT Fri Aug 28 2026...

KSLC...Winds are favored to trend southwest by late morning, and
then west to northwest by early to mid afternoon, though low
confidence noted given ongoing showers and outflows. Confidence
remains low as thunderstorm activity will increase, increasing
potential for gusty erratic outflow winds. Thunderstorms will also
be capable of brief reductions to CIGS/VIS, with around a 20% chance
of brief MVFR VIS in stronger activity. Winds are expected to shift
south by later in the evening, but scattered thunderstorms and
showers will persist. Thunderstorms once again expected to redevelop
Saturday afternoon.

REST OF UTAH AND SOUTHWEST WYOMING...Ongoing scattered high based
showers will result in some periods of variability to terminal winds
this morning. While terminals will generally favor their diurnally
typical directions, scattered thunderstorm development late morning
through the afternoon will further enhance the potential for gusty
and erratic outflow winds. Activity will also bring potential for
brief reductions to CIGS/VIS, with around a 20% chance of MVFR VIS
noted with any stronger activity atop a terminal. Scattered shower
and thunderstorm chances will then persist later into the evening
and likely for a few hours after midnight as instability persists.

&&

.FIRE WEATHER...High pressure over the Four Corners has added
moisture to an already unusually moist airmass, and anticipated
coverage of showers and thunderstorms will be greater today than
yesterday, with isolated strong to severe thunderstorms capable of
producing wind gusts to around 60 mph. The influence of a Pacific
Northwest trough and its associated cold front will bring a long
period of showers to northern portions of the forecast area Friday
night through Sunday, bringing increasing potential of wetting
rainfall and improved relative humidity values. Strong to severe
thunderstorms, however, will be more scattered in nature during
the day Saturday, bringing an increasing threat of strong and
gusty thunderstorm winds. For Sunday, the focus of showers and
thunderstorms is expected to shift to southeast Utah, bringing the
highest potential of wetting rainfall to that location. The active
pattern and cooler temperatures will continue into at least early
next week, with guidance indicating an increasing potential for
drier conditions for the middle to latter part of the week.

&&

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

PUBLIC...Traphagan
AVIATION...Warthen
FIRE WEATHER...Traphagan

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

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