090
FXUS65 KSLC 151013
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
313 AM MST Sat Nov 15 2025

.SYNOPSIS...An active pattern will bring heavy rainfall to
southwestern Utah later today into Sunday, with moderate to heavy
mountain snow for the higher elevations of southern Utah.
Additional storms lurk next week in this active pattern, with the
highest chance for impactful snow accumulations across southern
Utah.

&&

.DISCUSSION...A series of upper level lows will bring the threat
of precipitation to the region through the next 7 days. By next
Friday, the southern mountains could see as much as 2 to 3 feet of
snow and 2 to 4 inches of snow water equivalent. Lower elevations
such as St. George could see as much as 1.50 inches of rain by
the end of the forecast period.

Early morning upper air and satellite analysis indicates broad
upper level ridging continues to shift eastward toward the
southern Plains and into the lower Mississippi Valley. A
persistent and slow moving upper level low is nearing the southern
California Coast with a landfalling atmospheric river impinging
on the southern California Coast. A series of shortwave troughs
continue to cross the northern Pacific. Morning mesoanalysis
indicates precipitable water values have risen from near 0.60"
across western Utah early Friday morning to 0.70-0.90" early this
morning.

As an upstream trough begins to accelerate the eastward
progression of the previously mentioned upper level low, the
decaying atmospheric river will bring PWs at or above 99.5th
percentile (or even the max value for all climatology this time
of year) into the region. The EFI (EC based Extreme Forecast
Index) continues to show a markedly anomalous area of
precipitation across southwestern Utah between 00Z Sunday and 00Z
Monday. Perhaps most notable is the continued shift of tails,
showing that some members of the EC are showing a substantially
higher precipitation signal.

Looking at the 00Z HREF, there is a very strong signal among
several members indicating the threat of very heavy rainfall for
areas of southern Utah including the Forsyth Burn Scar over to
the portions of Zion National Park and southern Iron County. The
NAM Nest in particular the last few runs has shown precipitation
totals by Monday morning as high as 5 inches across the
Forsyth/Pine Valley area.

Why would this area see such heavy rainfall? As the upper level
low continues to shift eastward Sunday morning, the left exit
region of a jet streak rotating around the base of the trough will
set up across southwestern Utah. Coincident with this rich
atmospheric moisture will be 45-50kt southerly 700 mb flow. This
is a perfect set up for heavy precipitation across the Pine
Valley Mountains, as well as Pine Valley and New Harmony over to
the Zion National Park area. Looking at the various ensemble
systems, convective allowing models and other sources of
information, the period of heaviest precipitation coincident with
the best dynamics is expected between 7 PM Saturday and 5 PM
Sunday. Hourly rainfall rates around 0.10 to 0.25 inches per hour
are most probable, with a 20% chance rainfall rates will exceed
0.33 inches per hour, especially across the Forsyth burn scar and
toward Zion National Park. Storm total precipitation (25th to 75th
percentile) by Monday morning across lower elevation areas below
around 7500 feet are expected to range from 0.25-0.60" for the St.
George area (with a 10% of exceeding 0.75"), 1.50-3.00" for the
Forsyth Burn Scar/Pine Valley area (with a 10% chance of
exceeding 3.50"), and 0.50-1.25" for the Zion National park area
(with a 10% chance of exceeding 1.50"). Rain will gradually come
to an end Monday morning.

The Weather Prediction Center has outlooked portions of
southwestern Utah in a slight risk for excessive rainfall (meaning
at least a 15% chance of flash flood guidance being exceeded within
25 miles of a point) Saturday into Sunday morning. A marginal risk
for excessive rainfall continues Sunday morning to Sunday
evening.

For those impacted by the moderate to heavy rainfall across
southwestern Utah, ensure that all storm drains are cleared of
leaves and other debris this morning to reduce the threat of
localized flooding. With these rainfall amounts, all area streams,
rivers, normally dry washes and slot canyons will be running. If
your plans involved these areas, consider alternatives. For those
near the Forsyth Burn Scar, continue to monitor future forecasts.

For those elevations above about 7500-8000 feet, moderate to
heavy mountain snow is likely across the southern mountains.
Initially snow levels will be near 9500 to 10000 feet Saturday
evening, falling to near 7500 to 8000 feet By Sunday afternoon as
colder air moves into the region. Periods of heavy snow could
bring snow levels as low as 7000 feet at times, particularly
Sunday afternoon into Monday morning. Expect periodic winter
driving conditions on roads above 7500-8000 feet with the most
probable snow totals (25th to 75th percentile) around 6 to 12
inches for elevations above 9000 feet, 2 to 5 inches from around
7500 to 9000 feet. A winter weather advisory remains in effect.

The northern portion of the splitting upper level low will cross
northern and central Utah Sunday, bringing light mountain snow
(generally 1 to 6 inches). Most valleys will see around 0.10-0.33
inches of rainfall across northern and central Utah. Given these
amounts, no additional winter weather headlines are anticipated
for the northern and central mountains.

The next upper level low will move across the region Tuesday into
Wednesday. There has been a shift in the guidance, with around 50%
of ensemble members supporting a system that would bring another
round of moderate snow to the southern mountains as the trough
crosses the region. Bad news for the snow hopeful for
northern/central Utah as few if any ensemble members support
significant accumulations for northern and central mountains.
Right now, the 25th/75th storm total snow range for this system
for the southern mountains is 6 to 12 inches above 8000 feet, 2 to
5 inches from 7000 to 8000 feet. If the 50% of ensemble members
that favor a more southerly track are trending in the right
direction, the 25th percentile would be more representative of
potential snow accumulations.

Yet another potential upper level low lurks in Thursday to Friday
period, but given the substantial amount of impactful weather
between now and then, this is a low confidence portion of the
forecast. The best chance for substantial mountain snow
accumulations is once again across southern Utah, with the
majority of the ensemble members showing paltry amounts for the
northern and central mountains.

&&

.AVIATION...KSLC...Upper level moisture continues to increase
keeping skies cloudy through the day while maintaining VFR status.
Winds have seen an occasional northerly shift at the terminal
this morning, though should remain southerly through 19z today
when the diurnal northwesterly wind shift arrives. Chances for
light showers develop near the end of the TAF period though timing
uncertainty precludes any mention in the TAF at this time.

.REST OF UTAH AND SOUTHWEST WYOMING...Upper level moisture
continues to increase keeping skies cloudy through the day while
maintaining VFR status across all terminals through 00z. Following
00z, PoPs increase at KSGU and KCDC through the remainder of the
TAF period. Initially, mountain obscurations appear likely with at
least MVFR CIGs developing around 06z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory from 11 PM this evening to 5 AM MST
     Monday for UTZ125.

WY...None.
&&

$$

Kruse/Worster

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