Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 242121
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
321 PM MDT Sun Mar 24 2024

.SYNOPSIS...An active pattern will continue through Tuesday. Brief
high pressure will cross the area Wednesday, with an unsettled,
active pattern redeveloping Thursday into Friday.

&&

.SHORT TERM (Through 12Z/6AM Wednesday)...A longwave trough
encompasses the western CONUS this afternoon, with the mean trough
axis situated across the forecast area. Colder air aloft on the
upstream side of this axis is resulting in numerous showers and
isolated thunderstorms across the western half of the CWA
including the I-15 corridor, while more stable air further east is
limiting convective activity. Graupel has been common with the
stronger cores this afternoon, and this will persist into the
early evening hours before trending downward. Model guidance
suggests convective potential persists overnight downwind of the
GSL across Tooele valley and western SL county, and potentially
downwind of Utah Lake as well. As such have maintained a 40-50%
chance of showers across these areas. Otherwise, the Winter
Weather Advisory continues across the higher terrain through this
evening, and have continued this given potential for slick road
conditions owing to graupel this evening.

The mean trough axis will gradually move east, leaving the
forecast area within a cool and relatively unstable northwest flow
through the short term period. As such will continue to see
diurnally driven showers both Monday and Tuesday, with better
coverage Tuesday due to a more organized shortwave trough passing
through the region as the mean larger scale trough begins to exit.
Overall, given the showery nature of the precipitation winter
headlines do not appear warranted at this time.

With the cool upper trough in place through the short term,
temperatures will run roughly 10F below climo both Monday and
Tuesday across the forecast area.

.LONG TERM (After 12Z/6AM Wednesday)...A bit of a reprieve from the
active pattern sets in Wednesday as guidance remains in fair
agreement that ridging begins to build into the Great Basin and
Intermountain West. H7 temps increase yielding afternoon highs
nearer to climatological normal, and stability associated with the
ridge helps to largely preclude precipitation potential.

By Thursday, another broad Pacific trough begins to dig southward
through the PacNW. At a minimum, this looks likely to help increase
H7 winds, corresponding to some modestly gustier (generally ~25-40
mph) conditions across western Utah valleys and Utah`s West Desert
Thursday afternoon. Compared to yesterday though, guidance seems to
have backed off on potential advisory level winds, with only around
a 10% chance now noted across portions of the West Desert.
Unfortunately, aside from the aforementioned wind potential,
guidance starts to diverge into two similarly weighted camps,
yielding a couple different scenarios Thursday onward.

In scenario one, the Pacific trough digs closer to the California
coast with a more muted inland penetration, allowing greater
influence of the ridge to hang on locally. This scenario would
result in more favorable conditions for a bit milder and drier
weather to continue at least through Thursday. On Friday, closer to
~33% of ensemble members show a similar setup, decreasing to ~25% by
Saturday. In general, would likely see at least some increasing
moisture and energy advection through southwesterly flow as the
trough digs, so the pattern would become a bit more unsettled.

In scenario two, the Pacific trough penetrates a bit further into
the Great Basin as it digs southward from the PacNW. In this
scenario, increased moisture and synoptic support yields a quicker
transition to a wetter and more unsettled pattern through Thursday,
remaining unsettled on into the weekend. As mentioned from scenario
one, this pattern looks to become a bit more favored progressing
into the weekend. Even within this scenario, a bit more uncertainty
is noted in some of the specific details, with potential for a
baroclinic zone to advance into and become stalled somewhere across
the state. Where this boundary stalls would likely serve as a focus
for better precipitation potential. Current suite of guidance
slightly favors western to northern Utah for this. Short of a very
strong frontal push (which seems unlikely based on current
guidance), the wetter pattern would likely be a valley rain and
mountain snow type of event.

Uncertainty in where the Pacific trough progresses and how the
overall pattern evolves remains high late Saturday into early next
week. At a broad glance, ensemble members start to favor southern
Utah for unsettled weather with a signal for the trough to continue
digging southward. To that end, around 20% of ensemble members then
cut this low off somewhere in the region from southern California
into the Desert Southwest. Depending on exactly where this occurs
(if at all), this would be at least one necessary ingredient to
monitor for potential enhanced downslope/canyon winds in northern
Utah. This far out and with this much uncertainty surrounding the
pattern evolution through the week though, this remains just
something to keep an eye on depending on how the forecast ultimately
trends.

&&

.AVIATION...KSLC...Scattered afternoon/early evening convective
showers producing graupel, snow, and rain with embedded thunder
will create periods of brief MVFR conditions. Otherwise, VFR
conditions will be maintained with mountain obscuration owing to
low CIGs. Showers will decrease in coverage after sunset with <25%
chance of lake enhanced rain/snow showers impacting the terminal
overnight. Winds will stay out of the north with gusts possible as
convective showers pass by the terminal.

.REST OF UTAH AND SOUTHWEST WYOMING...Scattered afternoon/early
evening convective showers producing graupel, snow, and rain will
impact the entire airspace through ~03Z creating brief MVFR/IFR
conditions. Additionally, mountain obscuration will continue through
sunset due to low CIGs. Brief gusts 20-30 mph are possible with
convection near terminals. VFR conditions will likely prevail after
03Z as diurnal convection dissipates. Winds will remain out of the
north for most terminals.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory until midnight MDT tonight for
     UTZ110>113-117-125.

WY...None.
&&

$$

Seaman/Warthen/Mahan

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


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