646
FXUS65 KSLC 150958
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
258 AM MST Wed Jan 15 2025

.SYNOPSIS...High pressure will result in a gradual warming trend
through the end of the work week, in addition to dry and stable
conditions. A strong cold front will move through Friday night, with
some of the coldest air of the season expected to follow it. These
cold temperatures will likely linger into early next week.

&&

.SHORT TERM (Through 12Z/5AM Friday)...Analysis products early
Wednesday morning indicated the continued presence of a Rex Block
across the Eastern Pacific, with an east-west oriented ridge axis
now extending eastward across much of the PacNW. Meanwhile, a
closed low was located between 120W and 130W to the south of the
high pressure ridge. Over the next 24 hours, model consensus
suggests the ridge will continue to build across the Great Basin
through Wednesday night while the closed low begins to approach
the SoCal coast. Closer to home, expect strengthening valley
inversions through Wednesday night, with inversions remaining in
place through Friday as the ridge weakens slowly. Model forecast
soundings suggest inversions will reach their peak strength on
Thursday before beginning to gradually weaken Friday, only to be
mixed out completely with the arrival of a strong cold front. More
on that in the long term portion of the forecast below. The
above-mentioned closed low is forecast to traverse eastward, and
open up into a progressive wave across the Mexican border region,
staying far enough south to keep any weather associated with it
well to the south of southern Utah.

As of early Wednesday morning, a band of high-based stratus has
moved southward from eastern Idaho, and continues to advect
southward across northeast Utah early this morning. Where clouds
have moved in, radiative processes have ceased, and temperatures
have leveled off. For areas that have clouded over, fog potential
has diminished as well. Given that this cloud deck is poorly
modeled, confidence is low regarding how far south these clouds
will reach into Wednesday morning, as well as how long they will
remain in place. Nighttime satellite products are beginning to
suggest some erosion of the western edge of the cloud shield
across eastern Idaho, so have forecast a gradual erosion of the
cloud deck through the late morning/early afternoon hours based
on satellite trend interpolation. Extensive cloud cover is less
likely tonight into Thursday morning, so cannot rule out patchy
fog in valleys, especially those near bodies of water. We will
continue to monitor for any additional stratus development as
well. As far as temperatures are concerned, should the cloud
forecast behave, expect a gradual warming trend into Thursday and
Friday, when temperatures are forecast to reach 5F to 10F above
normal.

.LONG TERM (After 12Z/5AM Friday)...Models and ensembles are in
better agreement on a trough Friday into Saturday. The trough is set
to bring a relatively strong cold front, snow, and strong winds for
some locations. The ensemble range from the GEFS, EPS, and Canadian
were originally quite different on the track, with the lowest
confidence on how cold conditions would get. Those ensembles are in
better agreement, with a most likely scenario similar to the track
that most GEFS members have indicated, with a longwave trough where
the coldest conditions are east of the Rockies. Although it is a
warmer track, conditions will be cold, the coldest of the season for
most of southwest Wyoming and Utah for several nights starting
Saturday night.

The coldest conditions will build in behind a baroclinic zone, which
will bring snow, primarily to southwest Wyoming and northern Utah.
The storm system will be rather dry with limited snowfall largely
associated with the boundary. That front will track into northern
Utah Friday into Saturday, with most snow through Saturday. Enhanced
northwest winds will follow the front for downslope portions of
Castle Country and other locations with downslope winds from the
northwest.

Valley temperatures will be into the single digits and teens for
most Utah valleys Saturday night, with similar, but likely slightly
colder conditions Sunday night. Highs through the weekend will
largely be in the 20s and 30s for valleys.

Colder than normal, dry conditions will continue into the week. As
the trough becomes positively tilted to the east, roughly 40% of
ensemble members break off an area of colder conditions to the
northeast into southwest Wyoming and Utah.


&&

.AVIATION...Stratus in VFR range will clear through the morning,
with mostly clear or clear conditions for the afternoon. Light
southeast winds will transition to northwest around 19Z.

.REST OF UTAH AND SOUTHWEST WYOMING...Stratus may lower into MVFR
range in southwest Wyoming, otherwise stratus in VFR range for
portions of northern Utah will clear through the morning. Mostly
clear or clear conditions will last through the afternoon with
relatively light winds.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

ADeSmet/Wilson

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