989
FXUS65 KSLC 181528
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
928 AM MDT Tue Aug 18 2026

.KEY MESSAGES...

- Building high pressure will bring a steady warming trend in
  temperatures as conditions dry, bringing a threat of isolated
  critical fire weather conditions.

- Monsoon moisture will move back into Utah and southwest Wyoming
  late in the week, persisting through at least early next week.
  This will bring an increased threat of showers and thunderstorms
  capable of producing flash flooding.

&&

.DISCUSSION...High pressure is centered near the Utah/Nevada
border this morning with some shortwave energy rippling over the
top of it. Thus, seeing clear skies except for southwest Wyoming
and areas near the Utah/Idaho border. Satellite derived PWs
indicate values primarily in the 0.7 to 1.0 inch range, enough
moisture for some afternoon convective development. Coverage
should be generally isolated in nature, with the best coverage
over northeastern portions of the area, closer to the upper jet
associated with the passing shortwave energy.

Under the influence of the ridge, high temperatures today will be
similar to yesterday with maxes near seasonal normals. With the
ridge expected to amplify and move overhead Wednesday into
Thursday, temperatures will steadily warm, with maxes averaging up
to 10F above seasonal normals by Thursday, with the greatest
departure from normal over northern portions of the area. The
airmass will dry out during this time, with relative humidities
approaching critical values for portions of western Utah. Locally
breezy conditions could bring a few pockets of critical fire
weather conditions, but overall the threat is quite isolated.
HeatRisk values are forecast to move into the red (major) range
for some northern Utah valleys on Thursday, including the west
desert and parts of the Wasatch Front. Overall, though, the
increased threat of heat related illness will be mitigated due to
overall acclimation during the season.

By Friday, there is high confidence that the ridge will move its
axis to the monsoon favored position over the Four Corners,
drawing deep moisture back northward and increasing the potential
of showers and thunderstorms capable of producing flash flooding.
This will also remove the threat of critical fire weather
conditions and bring temperatures back to near normal for this
time of year. The monsoon moisture is expected to remain in place
through at least early next week.

&&

.AVIATION, Issued 557 AM MDT Tue Aug 18 2026...
KSLC, Issued 557 AM MDT Tue Aug 18 2026...
VFR conditions continue through the TAF period
with persistent mid to high level cloud coverage. Generally light
southeasterly winds persist this morning before transitioning
northwesterly around 19z, though there is potential for an earlier
switch around 18z.

REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions prevail for all
regional terminals through the period. Conditions remain mostly dry
across the airspace outside of isolated showers and thunderstorms
developing across the eastern half of Utah this afternoon and
evening. Winds remain generally light and diurnally driven today,
except for portions of southwest Wyoming and southern Utah as
enhanced southwesterly winds with gusts 20-25 kts develop this
afternoon.

&&

.FIRE WEATHER, Issued 435 AM MDT Tue Aug 18 2026...
Hot and dry conditions continue through the work
week as high pressure gradually strengthens across the region.
Conditions remain critically dry across lower elevations through
this period. A slight uptick in afternoon winds today will result
in elevated to locally critical fire weather conditions
developing mainly across lower elevations of central and southern
Utah. Otherwise, the main concern remains the threat for isolated
afternoon showers and thunderstorms capable of producing dry
lightning and gusty and erratic outflow winds. An influx of
monsoonal moisture is expected Friday onward across the region,
with storms trending wetter through the weekend as a result.

&&

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

$$

PUBLIC...Traphagan
AVIATION...Whitlam
FIRE WEATHER...Whitlam

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