747
FXUS65 KSLC 041031
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
331 AM MST Thu Dec 4 2025

.SYNOPSIS...A significant winter storm will impact northern and
central Utah late Thursday into Sunday morning. The potential for
unsettled weather continues through the middle of next week.

&&

.SHORT TERM (Through 12Z/5AM Sunday)...Utah and southwest Wyoming
find themselves under a west to northwest flow this morning on the
front side of a broad ridge centered off the Pacific coast.
Lingering moisture from the previous storm system is producing
some areas of low clouds and patchy fog across portions of
northern Utah with mostly clear skies elsewhere. Highs will stay
on the cool side today, up to 5F below seasonal normals.

A potent upper level jet is expected to move over the ridge into
the Pacific Northwest by Friday morning as atmospheric river
moisture gets drawn southwest, reaching northern Utah this evening
and overnight. This will bring a prolonged period of mountain snow
in warm advection. Snow levels will start below 4,000 feet across
northern Utah tonight, resulting in valley snow. However, in the
warm advection snow levels will steadily rise, most likely in the
4,500 to 5,500 foot range by Friday afternoon and in the 6,000 to
7,000 foot range by Saturday morning. Thus, valley precipitation
will be predominately rain.

A relatively ill-defined shortwave is then expected during the day
Saturday, with the associated front change the precipitation to a
cold advection regime, though snow levels should remain above most
valley floors. With the shortwave energy, the upper jet is then
expected to migrate southeast out of the area, bringing an end to
the precipitation Saturday night/Sunday morning. Given the
moisture rich atmosphere expected combined with good instability,
there is a high chance of significant totals for the mountains and
mountain valleys of northern Utah, particularly those areas that
do well in northwest flow such as the Cottonwoods and Bear River
mountains. Going Winter Storm Watch covers the current thinking
with regard to the storm well.

.LONG TERM (After 12Z/5AM Sunday)...By Sunday morning, a broad ridge
over the Pacific will be nudging into the western US, with overall
northwesterly flow persisting across the Great Basin. Residual low-
to mid-level moisture across northern Utah will result in some light
showers through Sunday and into Monday, particularly towards the
early morning hours as a shortwave trough quickly passes through the
region. However, any QPF will be minimal, likely <0.10" even across
the northern mountains.

Uncertainty in the longwave pattern increases beyond Monday; model
guidance disagrees with the amplitude of this ridge to our west,
which will ultimately steer the trajectory of a landfalling
atmospheric river. For example, the GFS suggests more zonal flow
which would allow this moisture to stream into northern
Utah/southwest Wyoming. However, the majority of model guidance (85%
by Wednesday, and still 65% by Thursday) favors a more amplified
ridge, which would orient this moisture well to our north. Still,
this lower-chance scenario is producing a fairly high tail in the
QPF distribution (i.e. a 90th percentile QPF of 1.00" in the
northern mountains), so will be something to watch. Regarding
temperatures and snow levels, although we could see a cold front sag
southwards later in the week, most model guidance suggests a gradual
warming trend through the week, with temperatures potentially
reaching 10-15 degrees above normal by late next week. Southern Utah
will remain dry alongside these warming temperatures through the
week.

&&

.AVIATION...Low clouds have mostly dissipated early this
morning, with clearing skies expected through the day before CIGs
drop once again after ~01-03z with the next storm system, resulting
in mountain obscuration and MVFR CIGs, particularly after 06z. Winds
will be light and variable through roughly 15-16z when southerly
winds around 5-10kts will pick up. These southerlies could persist
through the day (25% chance), though northwesterly winds will likely
return anytime between 20-23z.

REST OF UTAH AND SOUTHWEST WYOMING...Expect light and variable winds
through the morning, with westerly winds with gusts up to 25kts
expected to persist after ~18z. SCT-BKN low clouds over and adjacent
to higher terrain will begin to dissipate after roughly 15z, and may
produce periods of MVFR CIGs until then. CIGs will dip again across
northern/central UT and southwest WY later this evening.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Storm Watch from late tonight through late Saturday night
     for UTZ108-110>112.

WY...None.
&&

$$

SHORT TERM...Traphagan
LONG TERM/AVIATION...Cunningham

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http://weather.gov/saltlakecity