898
FXUS65 KSLC 082105
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
305 PM MDT Wed Oct 8 2025

.SYNOPSIS...Tropical moisture will rapidly increase across Utah on
Thursday and pose a flash flood risk, especially across southern
and eastern Utah through Saturday. Isolated flash flooding and
strong thunderstorms are also possible across northern Utah late
Saturday along and ahead of a cold front passage. Cooler and drier
conditions return by the second half of the holiday weekend Sunday
into Monday behind the cold front passage.

&&

.DISCUSSION...
Key Messages:
* Flash flood threat will increase late Thursday through Saturday,
  especially across southern and eastern Utah, due to tropical
  moisture associated with Tropical Storm Priscilla. Those looking
  to access the southern Utah backcountry and slot canyons going
  into this holiday weekend may strongly consider alternate plans.
* An isolated flash flood threat and isolate strong thunderstorm
  threat then increases across northern Utah on Saturday along
  and ahead of a cold front moving by Saturday evening.
* Cooler and drier weather will return across the state by the
  second half of the holiday weekend, Sunday into Monday, although
  lingering isolated thunderstorms cannot be ruled out across far
  eastern Utah.

This is not a typical Utah monsoon surge. On Thursday,
subtropical moisture will build in across southern Utah from the
southeast, associated with, but well ahead of Tropical Storm
Priscilla which will remain off the Baja California. Quality, deep
moisture will rapidly onset, as surface dew points currently in
the teens to near 30 across southern Utah will sharply rise over
the next 24 hours, with widespread 50s to near 60 degree dewpoints
in place by this time tomorrow. As this moisture surges in, it
will start to interact with mid-lattitude forcing across northern
Arizona and Southern Utah, with synoptic forcing increasing
Thursday evening into early Friday morning. This forcing is
associated with an upstream trough off the Pacific coast which
will help develop a jet streak over Nevada and into Northwest
Utah, placing southern Utah and northern Arizona under the left
jet entrance region and associated upper-level divergence. This
setup has similarities to predecessor rainfall events (PREs)
often associated with tropical systems, but which can produce
heavy rainfall events well in advance of the approaching tropical
system. Thus the Thursday evening through early Friday morning
contains the first period of elevated concern for more widespread
moderate to heavy rainfall much of southern Utah.

Into the day on Friday the jet streak and upper level divergence
start to weaken before some strengthening again late Friday,
while also shifting slightly farther east. Thus it is possible we
see a bit of a lull in the widespread heavy rain activity until
later Friday night into Saturday again as the upstream trough
starts to impinge on northern Utah. Where enough CAPE develops
ahead of the approaching cold front on Saturday, across northern
Utah, but also across southern and eastern Utah, there is a
conditional strong to severe thunderstorm threat given the very
ample shear in place associated with the approaching trough and
strong jet stream in place aloft. With this potential in place
northern Utah may see a semi-organized line of showers and
thunderstorms moving through by late Saturday into Saturday
evening along and head of the surface cold front. Meanwhile, more
discrete storm tracks may be able to develop across southern and
eastern Utah in still a very moisture rich environment. While
storm motions will be quick, these should be efficient rainfall
producers in this environment and would still be capable of
creating flash flooding where storms intersect more vulnerable
basins.

The cold front will sweep across Utah Saturday night through early
Sunday ushering a much cooler and drier airmass in its wake,
dropping dew points back into the 30s, and leaving temperatures 10
degrees or so below normal by Sunday. Temperatures will quickly
start to rebound by Monday to near-normal values with continued
drier air in place. Thus the second half of the holiday weekend is
shaping up to feel a bit more like fall with more pleasant weather
in place.

&&

.AVIATION...
The SLC terminal will see VFR conditions throughout the day with
mostly clear skies. Expect typical diurnal wind switches through
the TAF period. The chance (30%) for rain showers and isolated
thunderstorms will increase Thursday afternoon, with erratic wind
gusts and brief MVFR restrictions the main potential hazards.

.REST OF UTAH AND SOUTHWEST WYOMING...The entirety of the airspace
will see VFR conditions and mostly clear skies throughout the day.
Moisture will increase across southern Utah on Thursday with
scattered showers and thunderstorms developing. Gusty and erratic
winds near thunderstorms, along with localized MVFR to IFR
restrictions are the main hazards associated with any
thunderstorms.

&&

.FIRE WEATHER...
Locally critical fire weather conditions will continue this
evening with gusty southerly winds across portions of western and
southern Utah. Widespread wetting rains will shift northward into
southern and eastern Utah Thursday morning and continue into at
least Saturday.

&&

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

WY...None.
&&

$$

PUBLIC...Church
AVIATION...Church
FIRE WEATHER...Kruse

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