590
FXUS65 KSLC 221001
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
401 AM MDT Sat Aug 22 2026

.KEY MESSAGES, Issued 1019 PM MDT Fri Aug 21 2026...


- Monsoonal moisture will continue to spread across Utah and
  southwest Wyoming through Saturday, bringing an increased threat
  of thunderstorms that could produce heavy rainfall capable of
  flash flooding.

- Moisture will decrease somewhat Sunday into Monday, with the
  potential for more substantial drying for at least northern Utah
  and southwest Wyoming late in the upcoming week.

&&

.DISCUSSION, Issued 1019 PM MDT Fri Aug 21 2026...
An elongated ridge of high pressure is centered
roughly over the Four Corners region this evening. The resultant
southerly flow aloft has allowed for monsoon moisture to spread
northward across the southern three-quarters of the forecast area.
Satellite derived PWs indicate values of 1.0 inch or above for
that part of the area, with the moisture continuing to move
northward. Embedded shortwave energy in the flow is allowing an
area of showers and thunderstorms to continue tonight over central
Utah, with the showers continuing to track northward for the
remainder of this evening and into the early part of the overnight
hours before dissipating.

With ample moisture in place tomorrow, will see another round of
scattered showers develop during the afternoon. Absent a well
defined forcing mechanism, these will be primarily focused over
the higher terrain. This will tend to limit the potential for
valley convective activity, but would not be surprised to see a
few showers pop up away from the terrain. Forcing is expected to
be enhanced again during the evening and early overnight hours,
this time from a frontal boundary ejecting from a Pacific
Northwest storm system. Given the front will be very much
outrunning its associated forcing, think associated precipitation
will be scattered in nature, primarily focused over northwest
Utah.

The front is expected to bring a very slight dip in temperatures
Sunday or northern portions of the area, bringing highs within 5F
of seasonal normals. However, its passage combined with flattening
of the ridge as the Pacific Northwest system tracks over the top
of it will add a westerly component to the flow aloft, advecting
some drier air in through Monday. This does not look to be
substantial drying by any means, but there is a high chance of
some areas seeing PWs as low as the 0.6 to 0.8 inch range, which
could bring minimum relative humidity values back close to
critical values for portions of western Utah. This could also act
to decrease coverage of afternoon showers and thunderstorms, but
as we saw earlier this week, there`s a good chance that the
decrease would not be substantial.

Spread in the guidance increase quite a bit for the middle to
latter part of the week, putting confidence in the long term
forecast a bit lower than usual. For Wednesday into Thursday,
another Pacific Northwest trough is expected to move over the top
of the Four Corners ridge, and ensembles seem to be struggling
with how much the trough interacts with the ridge. Some guidance
(the GFS, for example) shows only minor flattening of the ridge,
which would keep at least some moisture over most of the area into
the upcoming weekend. However, in solutions where the interaction
brings more substantial flattening of the ridge (e.g. the latest
EC), the more zonal flow would bring more dramatic drying. Will
wait and see where things end up landing.


&&

.AVIATION, Issued 1019 PM MDT Fri Aug 21 2026...
KSLC, Issued 1019 PM MDT Fri Aug 21 2026...
The SLC terminal will see VFR conditions
through the night with cigs expected to stay above 6000 ft AGL. An
area of showers with a few thunderstorms is expected to move
across the terminal beginning between 05Z and 06Z and lasting
through the early part of the overnight hours. There is a 40-50
percent chance of gusty and erratic winds as this moves through
and a 10 percent chance of lightning impacting the terminal.
Southerly winds are expected to shift to the north tomorrow
between 19Z and 21Z with a 20 percent chance of additional
showers and thunderstorms impacting the terminal during the
afternoon and early evening.

REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions are expected
across the airspace through the overnight hours. An area of
showers with a few thunderstorms over central Utah will move
across northern portions of the airspace through the first part of
the early morning before dissipating. Additional showers and
thunderstorms are expected to develop Saturday afternoon and
evening, primarily focused over the higher terrain. Any of these
storms will be capable of bringing lightning, brief mountain
obscurations, and brief MVFR conditions in heavier rainfall.

&&

.FIRE WEATHER...Light rain continues to linger across northern Utah
that will dissipate by early morning. Moisture will remain
elevated across the region with more storms developing Saturday
afternoon. Most models have the southern 1/3rd of Utah remaining
relatively dry today with most of the activity across central and
northern Utah. These storms that develop today will likely weaken
and linger into the overnight hours across northern Utah, similar
to the activity that occurred tonight. These afternoon storms will
be capable of frequent lightning along with gusty and erratic
winds.

After today moisture will gradually start to decrease across the
region, particularly across southern Utah. Precipitation chances
will remain through midweek before flow aloft becomes more
westerly during the second half of the week. This will bring much
drier air into the area with minimum relative humidity decreasing
back into the teens with recoveries in the 30s and 40s. Winds will
also be increasing as conditions dry.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Heat Advisory until 7 AM MDT this morning for UTZ101>106.

WY...None.
&&

$$

PUBLIC...Traphagan
AVIATION...Traphagan
FIRE WEATHER...Mahan

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