934
FXUS65 KSLC 052302
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
402 PM MST Wed Feb 5 2025

.SYNOPSIS...Cooler temperatures will spread into the area tonight
behind a cold front along with dry conditions. Another cold front
will cross the area Friday into Saturday.

&&

.SHORT TERM (THROUGH 12Z FRIDAY)...A shortwave trough that grazed
northern Utah earlier today is already ejecting into Wyoming. The
associated surface boundary is currently analyzed over Utah County,
and is accompanied by a band of showery precipitation with valley
rain and mountain snow. Briefly moderate precipitation had been
noted with some of the heavier showers, supported by modest
instability (HREF ensemble mean SBCAPE values of up to 150 J/kg).
With the parent trough departing farther away, the front is not
likely to make it too much farther south before weakening. As a
result, expect just a few lingering weak showers this evening across
central Utah before drier and more stable air settles into the area.

With a cooler airmass spreading into the area (H7 temperatures
ranging from -3C at PVU to -10C along the Idaho border late
tonight), overnight minimum temperatures will be much cooler
compared to the last few night. This will be aided by good radiative
cooling as skies clear out this evening. However, current forecast
min temperatures, while reaching near to below freezing across
northern Utah, are still generally 5-10 degrees above climatological
normals.

A return to southerly flow and warm advection will maintain above
normal temperatures for tomorrow, but again, not as warm as previous
days. Southwesterly flow aloft will remain enhanced, with widespread
H7 winds to 30 kt (and 40-45kt across southwest Utah). However,
expect winds to be weaker compared to today and generally remaining
below advisory criteria, owing in part to a much weaker surface
pressure gradient. A fairly appreciable moisture plume will also
start to spread into the area by the afternoon/evening, with IVT
from both the NAEFS and EPS exceeding the 99th percentile of
climatology. This will start to bring precipitation to northern Utah
during the afternoon and increasing in the evening. Given the mild
airmass, however, snow levels will generally remain high, although
some period of snow or a rain/snow mix may be possible in some
valleys initially (and closer to the Idaho border).


.LONG TERM...(After 12Z/5AM Friday)...A broad longwave trough moving
through the region will just graze northern Utah as it lifts out,
and the though will still deliver a bit of a punch by way of a
pronounced surface frontal boundary expected to accompany the
system. The majority of the uncertainty with this feature is its
timing rather than its strength, but that timing will have
significant impacts on the wind impacts across the West Desert as
well as on how cold air will line up with the heaviest precipitation
periods, shifting the balance of precipitation between rain or snow.
For northern Utah, impacts are expected to be limited to high
mountain roadways including Sardine and Parleys Summit, but given
the increased soil temperatures and roadway temps, will be a
challenge to get much in the way of accumulating snow on roadways.
Populated areas of central and southern Utah will be limited to rain
in all but the highest elevation areas and largely shielded from
impacts.

Mountain areas could see significant precipitation above 7500-8500
ft initial snow levels early on Friday, with relatively tight spread
in the NBM probabilities. Snow Ratio/Density transitions quickly
from 5-8:1 to 12:1 as the upper level front progresses through the
terrain, with areas to the north (especially the Bear River range)
more likely to come out at the upper end of the spread.
Precipitation is expected to quickly come to an end as the majority
of ensemble output drive much drier air into the region no later
than 12Z Saturday. A few orographically forced snow showers may
linger in the northern Wasatch under W/NW flow as the last of the
mid-level moisture clears out.

The remainder of the weekend and much of next week is under the
influence of a broad longwave trough bringing a colder, continental
airmass into the region that will help drive a return to seasonally
appropriate temperatures. This trough appears moisture starved in
all but the wettest ensemble solutions, suggesting that while there
may be some increased cloud cover and winds in the region with this
trough, it will bring little in the way of additional precipitation.
At the very end of the forecast period (Thursday the 13th) ensembles
diverge significantly, with about half the membership suggesting a
potent storm poised to bring colder air and ample moisture into the
region, but hard to say much in the way of details just yet.

&&

AVIATION...KSLC...Northwesterly winds are expected to gradually
taper through this evening behind the front, eventually becoming
light and southeasterly roughly 10-12z Thursday. Dry conditions with
clearing skies persist overnight into Thursday morning, before
another weather system brings increasing cloud cover and decreasing
CIGS by Thursday afternoon.

.REST OF UTAH AND SOUTHWEST WYOMING...Showers are wrapping up
across the southern Wasatch this afternoon, yielding widespread dry
conditions for the remainder of the TAF period. Gusty west-northwest
winds across northern Utah will taper off behind the front this
evening, becoming light and terrain driven overnight. For southern
Utah, southwesterly winds to persist into the late afternoon,
becoming light this evening.

&&

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

&&

$$

Cheng/Wessler/Whitlam

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