Elmo, Utah Weather Forecast Discussion

164
FXUS65 KSLC 040937
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
337 AM MDT Sat Oct 4 2025
.SYNOPSIS...A strong, cold Pacific system will continue to impact
the region through Saturday. Colder temperatures will continue
through the weekend, with a warming trend in store for much of the
next week. The threat of deep tropical moisture and resulting
heavy rainfall is increasing for southern Utah late in the week.
&&
.DISCUSSION...Thunderstorms with moderate to heavy rain continue
to impact portions of the Wasatch Front and Back early this
morning. Early morning upper air and satellite analysis indicates
a strong upper level trough is crossing the Great Basin. The
associated upper level low is currently near Cedar City.
Widespread showers and thunderstorms continue even at this late
hour across much of northern and western Utah. Tropical Storm
Octave continues a circuitous route across the eastern Pacific,
while an area of disturbed weather is likely to transition to a
Tropical Depression today to the east of Octave near the west
coast of Mexico. This soon to be named TD may have significant
implications in the extended portion of the forecast period.
The upper level low will continue to shift east across Utah
through the morning. Showers and thunderstorms will continue to
develop and shift northeast in association with this low. The
associated cold front will finally cross northern Utah later this
morning, with westerly flow developing in it`s wake. This will
keep widespread valley rain and high elevation snow through at
least this evening across northern Utah. Final rain totals will
generally average 0.50 to 1.00 inches, with some locations seeing
heavier totals, especially near heavier thunderstorms and/or in
areas that do well in westerly flow.
Some of the coldest temperatures of the season are expected
tonight into Sunday morning across much of the Beehive State.
Frost is the most likely outcome especially in the Sanpete, Sevier
and Rush VAlleys, southern Utah County near Santaquin and Spanish
Fork, outlying areas of Castle County, near Fillmore, and
southwestern Utah including Cedar City and Enterprise. The threat
of freezing temperatures in these locations continues to decrease,
though the highest percentage (about 40%) is across higher
portions of the Sanpete Valley, the Rush Valley and outlying
southwest Utah near Enterprise. Given lower confidence, will not
be issuing any freeze headlines on this shift.
A warming and drying trend will follow across the region for much
of the week. Attention then turns to the potential for the as of
yet unnamed disturbance across the tropical eastern Pacific to
shift tropical moisture into Utah Thursday into the weekend. Two
main tracks of this system have emerged from the models, largely
influenced by the synoptic scale pattern evolution. Around 70% of
ensemble members support deep tropical moisture (PWs approaching
the 99th percentile across southern Utah) either by Friday or the
weekend (timing is split between Friday and Saturday/Sunday as
the arrival day). There are a few patterns that can bring
substantial flooding to southern Utah in October and a decaying
tropical system across the Desert Southwest is one of them.
Looking at the distribution for precipitation totals across
southern Utah, there is a wide distribution in the 70% of ensemble
members that support deep tropical moisture across southern Utah.
Anywhere from 0.10" in 24 hours to over 3.00" in 24 hours is
resolved by different ensemble members for lower Washington
County. Needless to say, this event has potential bring
significant rainfall to southern Utah and anyone with interests
across southern Utah later next week should monitor the forecast
and consider postponing outdoor activities in normally flood prone
locations like slot canyons, slick rock areas and normally dry
washes if confidence continues to increase.
&&
.AVIATION...KSLC...Light to moderate rain will last much of the
day. Broken or overcast conditions will last through the day. VFR
conditions are likely, but stronger showers or thunderstorms will
be capable of lowering visibility into MVFR or IFR range. Light
northwest winds will last through the day with relatively light
speeds, but precipitation will be capable of varying wind
directions. Rain will transition to rain showers around 21Z, then
taper off around 03Z.
.REST OF UTAH AND SOUTHWEST WYOMING...Light to moderate rain will
last through 21Z for southwest Wyoming and northern Utah. Rain
showers are likely from around 21-03Z when precipitation tapers
off. Broken to overcast conditions with intermittent MVFR or IFR
visibility are likely with stronger showers or thunderstorms.
Conditions will trend drier further south. Relatively light
northwest winds will be in place for most locations, although
there will be varying wind directions for locations with
precipitation.
&&
.FIRE WEATHER...A cold, fall storm system continues to cross the
region today. Widespread wetting rain is expected across the
north, with a general 0.50 to 1.00 inch for most locations. Light
snow accumulations are expected across the northern mountains
above 9000 feet. Any precipitation is expected to end this
evening.
A warming and drying trend will be the main story for early to
midweek next week. By late in the week, there remains a 70% chance
tropical moisture will move into southern Utah bringing the
threat of moderate to heavy rain and potential flooding.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&
$$
Kruse/Wilson
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NWS SLC Office Area Forecast Discussion