648
FXUS65 KSLC 102059
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
259 PM MDT Fri Oct 10 2025

.SYNOPSIS...Showers and thunderstorms will continue as tropical
moisture continues to stream into Utah, producing a significant
flash flood threat, especially across southern and eastern Utah.
Heavy rainfall will remain a threat through at least Saturday, with
a heightened severe thunderstorm threat as a strong cold front
crosses the area late in the day.

&&

Key Messages:
* Tropical moisture will produce a continued significant flash
  flood threat through tomorrow, particularly across southern and
  eastern Utah. A Slight (Level 2 out of 4) to Moderate Risk
  (Level 3 out of 4) for excessive rainfall may result in flooding
  of slot canyons, normally dry washes, recent burn scars, and
  other flood-prone locations. Backcountry roads may become
  impassable.
* Strong to severe storms are possible tomorrow afternoon/evening
  as a potent cold front sweeps through the state, with a Marginal
  Risk (Level 1 out of 5) for severe thunderstorms. Strong storms
  are also possible in far southwest Utah later this afternoon and
  evening.
* Gusty southwesterly winds will develop ahead of this cold front
  tomorrow, especially west of I-15. The most likely gusts look to
  be 30-40 mph across western valleys, with a low (10-25%) chance
  of reaching 45 mph for most locations.
* Snow levels will plummet behind the cold front down to as low as
  6000 feet over northern Utah (7500 feet across central Utah),
  resulting in minor snow accumulations in the northern and
  central mountains.

Satellite analysis this afternoon shows a very large circulation
center just offshore of the the PacNW coast, while the remnants of
Post-Tropical Storm Priscilla are noted over the central Baja
Coast. Utah is under a southwesterly flow downstream of the PacNW
low, drawing tropical moisture from Priscilla into the area.
Latest PWAT analysis ranges from 1.3 inches across southern Utah,
with generally to around 0.9 inches across the north, around twice
the climatological norm. At the surface, dewpoints across
southern Utah have risen to the 50s and 60s, while across northern
Utah, they are slightly drier in the mid 40s to mid 50s.

Area radars show a relative lull in activity currently (outside
of the central spine of Utah mountains), though CAMs show
significant development later this afternoon and evening over
southern Utah, where the SPC mesoanalysis shows around 1,000 J/Kg
of MUCAPE and 20-30 kts of 0-6km shear. In fact, the SPC upgraded
far southwest Utah to a Marginal risk, so we will continue to
monitor for strong thunderstorms capable of gusty winds, hail, and
heavy rain. The threat continues into the night and generally
shifts east, with the highest potential for heavy rain along the
Utah/Arizona border during the overnight hours.

By tomorrow afternoon, the upstream low will approach Utah as an
open- wave trough, and stronger southwest flow will aid in
bringing increased shear to the area. The HREF ensemble mean shows
a sizable area of 500-1000+ J/kg of SBCAPE over Utah, along with
25-50+kt of SFC-500mb shear. With moisture remaining in place and
showers continuing, this will bring the potential for strong to
severe storms with a potential for strong winds and hail. This
will continue ahead of and along a strong cold front which will
cross northwest Utah late Saturday afternoon through Saturday
evening, and through the rest of the forecast area Saturday night
into Sunday morning. The Storm Prediction Center has a Marginal
Risk for severe weather for the vast majority of our forecast area
for Saturday. Additionally, northern Utah will likely see its
best window for significant precipitation on Saturday, especially
around the time of the frontal passage. The NBM has a 40-75%
chance of 1 inch or greater along the Wasatch Front between
Saturday morning and Sunday morning.

As the airmass gradually dries behind the cold front Saturday night
through Sunday, much cooler air will settle into the area. As snow
levels lower, expect some accumulating snow for the higher
elevations (generally 6000-6500ft or higher) of northern and central
Utah. Because the precipitation will be winding down as the cold air
moves in, snow accumulations are not expected to be significant(55%
chance of greater than 4 inches in the upper Cottonwoods but
generally less than 35% chance elsewhere).

A break in the weather is expected late Sunday through Monday, but
this break will be short-lived as the next storm system will amplify
along the West Coast on Monday before moving inland Tuesday into
Wednesday. This will bring increasing southerly flow along with some
moisture which, when aided by upper diffluence ahead of the storm,
will bring a period of unsettled weather back to the area.

&&

.AVIATION...KSLC...Low chances for thunderstorms exist through
roughly 01z; any storms that do develop will be capable of producing
lightning and heavy rain, with brief periods of MVFR conditions (10%
chance of brief IFR conditions) and squirrely winds. Chances for
more showers and isolated thunderstorms return overnight, though
uncertainty in exact timing is high since KSLC will be on the
northern fringe of these showers. Periods of moderate to heavy rain
will be possible with these showers. Stronger thunderstorms are
likely to develop Saturday afternoon ahead of a strong cold front.

.REST OF UTAH AND SOUTHWEST WYOMING...Showers and thunderstorms will
develop this afternoon and evening across much of Utah and southwest
Wyoming, with the main threats being heavy rain and MVFR-IFR
VIS/CIGs. After ~02z, most of this rainfall will become more
widespread but less intense, particularly over S-UT. Across N-UT/SW-
WY, forecast confidence is lower with when/if areas receive rainfall
overnight, with generally higher chance further south. Winds will
remain primarily southerly, though valleys may see light and
variable winds overnight. By Saturday afternoon, stronger
thunderstorms are expected to develop ahead of a strong cold front.

&&

.FIRE WEATHER...Tropical storm remnant moisture will bring elevated
humidity to the entire area and a very high chance of wetting
rains to the mountains of Utah from around Strawberry Reservoir
southward with widespread showers and thunderstorms. Areas east
of the Wasatch Plateau such as the San Rafael Swell will also see
a significant chance of heavy rain and near certain wetting rain
potential. The west deserts will have a much lower chance of
wetting rain, but even in those locations RHs will remain
elevated.

The main moisture push moves east of our area tomorrow, but
sufficient moisture will linger for an additional round of
showers/thunderstorms. In addition, a potent cold front will
slide through the area late in the day, bringing a high chance of
wetting rains for northern and central Utah. Additionally, gusty
southwest winds will develop in advance of the front west of I-15,
especially over southwest Utah. Higher elevations, generally
above 6500 feet, are expected to see accumulating snow Saturday
night through Sunday morning as a much cooler airmass settles into
the area behind the cold front.

A general warming and drying trend can be expected late Sunday
through Monday. However, another storm system will approach Utah
by the middle of next week, bringing another period of unsettled
weather to the area.&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Flood Watch through Saturday evening for UTZ113-114-117-120>131.

WY...None.
&&

$$

Van Cleave/Cunningham

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