176
FXUS65 KSLC 030946
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
346 AM MDT Wed Sep 3 2025

.SYNOPSIS...Monsoon moisture moves in from the south today
through the latter half of the week, bringing increasing chances
for showers and thunderstorms, especially by the weekend. Drier
conditions are expected to develop early next week.

&&

.SHORT TERM (Through 12Z/6AM Friday)...Current radar imagery depicts
nocturnal showers skirting far southwest Utah this morning.
Otherwise, conditions remain quite dry across Utah and southwest
Wyoming outside of some increasing high-level clouds this morning.
Monsoonal moisture is expected to increase across southwest Utah
through the remainder of today as the ridge axis initially
overhead shifts slightly eastward, allowing moist southerly flow
to develop aloft. This increased moisture transport will push PWAT
anomalies to around 150 percent of normal across southwest Utah,
resulting in increased chances for afternoon showers and
thunderstorms. This initial moisture surge will remain high-based
today, yielding mainly a dry microburst threat, with gusts to 40
mph possible in the vicinity of any storms that develop.

This monsoon moisture will continue to spread northeast on
Thursday as the ridge continues to break down across the region,
allowing afternoon shower and thunderstorm coverage to spread as
far north as the I-80 corridor. Storms will trend wetter across
southern Utah on Thursday as moisture deepens through the column,
when in conjunction with slow storm motions (only around 5-10 kts)
brings an increased flash flood threat across the area.

.LONG TERM (After 12Z/6AM Friday)...With the axis of an upper level
ridge shifting eastward, a deeper, moisture rich southerly flow will
spread across Utah and southwest Wyoming and bring a return of
active weather area-wide.

KEY MESSAGES:

- Atmospheric moisture reaches its peak on Friday/ Saturday,
 bringing greater coverage of showers and thunderstorms capable of
 producing heavy rainfall.

- Storms on Friday and Saturday will be relatively slow moving,
 increasing the likelihood flash flooding in higher risk areas
 such as slot canyons, slickrock areas, normally dry washes, and
 recent burn scars. Urban flooding will also be possible with
 these slow moving storms.

- Conditions are expected to dry out significantly heading into
 next week, with increasing chances for hot, dry, and windy
 conditions to return by Monday/ Tuesday.

DETAILS:

Deeper atmospheric moisture will spread into Utah and southwest
Wyoming on Friday, with total layer precipitable water (PWAT) values
rising to upwards of 150 to 175 percent of normal. For Friday, lower
to mid-level flow will remain less than 15 knots, indicating strong
potential for slow moving storms. As such, with moisture reaching
its peak and steering flow remaining light, developing storms are
expected to move slowly and bring modest potential for heavy
rainfall. Area of highest risk for experiencing flash flooding will
exist in the slot canyons/ dry washes, slickrock areas, and recent
burn scars across central and southern Utah. Risk for flash flooding
on recent burn scars across northern Utah will also exist, though
the greatest coverage of storms is expected across the
aforementioned region.

Models continue to indicate a shortwave trough being ejected from an
upstream longwave trough off the U.S. West Coast on Saturday which
will act a broad-scale lifting mechanism. Pairing with the anomalous
moisture already in place, chances for showers and isolated
thunderstorms will be maintained through the morning hours on
Saturday. Given modest forced ascent during the early morning hours,
there is potential that we end up with more light to moderate
rainfall with a lack of thunderstorms on Saturday afternoon as the
cloud cover acts to inhibit strong convection. If this occurs, the
threat of flash flooding across the area will be quite limited.
Additionally, if this wave passes through the area rather quickly
(supported by 20-30% of ensemble members), then much of the
western half of Utah will fall under a subsident wake, further
inhibiting afternoon convection.

Moisture begins to wane by Saturday evening and will continue to do
so through at least Tuesday. As the aforementioned upstream trough
creeps closer toward the eastern Great Basin region, an increase in
southwesterly winds is expected area-wide. Breezy afternoon
conditions will be a likely result on Tuesday and Wednesday.
Stronger winds paired with afternoon relative humidity values
ranging from 10 to 25 percent will create areas of elevated to near-
critical fire weather conditions.

&&

.AVIATION...KSLC...VFR conditions are expected to prevail
through the forecast period under high level cloud cover. Winds are
expected to follow diurnally driven trends, transitioning from a
southerly flow in the morning to a northerly flow between 18-19Z.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions are expected to
prevail across a majority of Utah and southwest Wyoming today, with
the exception of potential MVFR to IFR conditions in heavier rain
showers across southern Utah. Most airfields will experience terrain
driven flows, however, southern Utah showers and isolated
thunderstorms will bring potential for gusty and erratic outflows in
excess of 30 mph after about 19Z. Anticipate potential for shower
and thunderstorm activity between 18/19Z through 03Z.

&&

.FIRE WEATHER...Monsoonal moisture is expected to increase across
southern Utah today, gradually overspreading the state through the
latter half of the week. Chances for showers and thunderstorms
increase this afternoon and evening across southwestern Utah, though
dry lower levels still in place will limit wetting rains to far
southwestern Utah, yielding mainly a dry microburst threat for the
remainder of the region. Moisture continues to deepen and spread
northward Thursday through the weekend, allowing storms to trend
wetter and resulting in more widespread coverage through this
period. Expect gradual improvement in daytime RH values through
the end of the week, with overnight humidity recoveries becoming
good to excellent areawide overnight Friday. Gradual cooling is
also expected, with highs running a few degrees below seasonal
normals by the weekend. A drier airmass begins to nudge into the
region early next week due to increasing southwesterly flow,
limiting chances for continued afternoon shower and thunderstorm
activity.

&&

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

$$

Whitlam/Webber

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