135
FXUS65 KSLC 101006
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
406 AM 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 on Saturday afternoon as a
strong cold front crosses the area.

&&

.DISCUSSION...
Key Messages:
* Tropical moisture will produce a significant flash flood threat
  through Saturday, 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.
* On Saturday, strong to severe storms are possible in the afternoon
  as a potent cold front sweeps through the state, with a Marginal
  Risk (Level 1 out of 5) for severe thunderstorms.
* Gusty southwesterly winds will develop ahead of this cold front on
  Saturday; the most likely gusts are to 30-40 mph across western
  valleys, with a low (10-25%) chance of reaching 45 mph.
* Snow levels will plummet behind the cold front down to as low as
  6000ft across northern Utah (7500ft across southern Utah),
  resulting in minor snow accumulations in the northern mountains.

A closed low is in place early this morning off the PacNW coast
while what is now Tropical Storm Priscilla is 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 has over 1-1.2 inches across southern Utah,
with generally 0.7-0.9 inches across the north. This is expected to
continue to increase through the morning hours, peaking at around
1.25 inches across far southern and southeast Utah and around 1 inch
elsewhere early this afternoon. These values would be 250-350% of
normal for this time of year. Meanwhile, 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.

Widespread rain showers moved through southern and central Utah
overnight, associated with a weak disturbance that lifted through
southern Utah. As this feature continues northeast, precipitation
has started to decrease from the southwest, while increasing across
central and northern Utah. This area of precipitation will then
continue to shift into north-central through northeast Utah and
southwest Wyoming later this morning. Generally light to moderate
rain has been reported with this precipitation, but since this has
been occurring over a large area, brief rises were noted earlier on
a few river gages across southern Utah.

Another round of intensifying precipitation is expected later this
morning through this afternoon and into this evening, again focusing
on southern and eastern Utah, with more isolated to scattered
coverage of showers across the north and west. Rain will generally
remain light to moderate, but occasional bursts of heavier rain
(most likely from mid-afternoon through this evening) will lead to
an increased threat of flash flooding, especially near recent burn
scars, slot canyons, normally dry washes, and other prone areas.
Showers will continue tonight and into Saturday morning. The Weather
Prediction Center now has a Moderate Risk in its Excessive Rainfall
Outlook across southwest through south-central Utah within a larger
Slight Risk area for the period 12z today through 12z Saturday. All
that said, there is still a fair amount of spread in precipitation
amounts, as the NBM 25th percentile amounts over the next 24 hours
range from around 0.25 inches across the southeast to 0.45 inches
across the southwest, while the 75th percentile amounts range from
around 0.8 inches across the southeast to 1.5 inches across the
southwest.

By Saturday 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 the 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...An active TAF period is in store for KSLC with
mountain obscurations likely throughout the majority of the day,
occasional MVFR visibilities, and prevailing showers with occasional
thunderstorms near the terminal. Through the period, winds will
remain out of the south at around 10kts. Thunderstorm chances near
the terminal appear most likely from 10-14z and 21-01z with erratic
winds and gusts to around 30kts.

.REST OF UTAH AND SOUTHWEST WYOMING...An active day of weather is
expected across all of our sites with an extended period of mountain
obscurations, prevailing rainfall occasionally resulting in MVFR
CIGs, and afternoon thunderstorms. Winds will generally remain out
of the south around 10kts with erratic gusts in thunderstorms to
around 30kts.

&&

.FIRE WEATHER...Abundant moisture from a tropical system continues
to spread into Utah today, resulting in increased humidities and
widespread showers with isolated to scattered thunderstorms across a
large portion of the area. Wetting rain will be likely especially
across southern and eastern Utah today. Far northwest Utah will see
more isolated showers and thunderstorms today with much lower
potential for wetting rain. Showers will continue overnight and into
Saturday. As southwest flow strengthens for Saturday afternoon ahead
of an approaching cold front, some thunderstorms may be strong and
produce gusty winds and hail. The cold front is expected to cross
northwest Utah late Saturday afternoon through Saturday evening, and
the rest of the area Saturday night into Sunday morning. Fairly
widespread showers will continue along the cold front before
gradually winding down Saturday night and Sunday morning. Northern
Utah will likely see wetting rain near the cold front Saturday
evening. 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.
Thereafter, a general warming and drying trend can be expected late
Sunday through Monday. By the middle of next week, another storm
system will approach Utah, bringing another period of unsettled
weather to the area.

&&

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

WY...None.
&&

$$

Cheng/Worster

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