091
FXUS65 KSLC 161039
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
439 AM MDT Thu May 16 2024

.SYNOPSIS...Warm and dry conditions today will be followed by a
mainly dry cold front crossing the region Friday, which will be
accompanied by gusty post-frontal winds across northern Utah.
Unsettled weather is expected this weekend into early next week.

&&

.SHORT TERM (THROUGH 12Z SUNDAY)...The large-scale pattern this
morning shows Utah under a northerly flow aloft while the trough
that impacted the area yesterday has now dropped into Arizona.
Upstream, high pressure is building off the West Coast. Drier,
warmer, and more stable conditions can be expected across Utah today
as a result.

A shortwave trough will graze northern Utah tomorrow. This will push
a relatively shallow cold front into northern through at least
central Utah tomorrow afternoon and evening. This cold front will be
accompanied by gusty winds, strongest along the Idaho border and
across northwest Utah and southwest Wyoming. Additionally, some CAMS
are hinting at some isolated, weak high-based convection near the
boundary mainly across central Utah, with greatest threat being
gusty microburst winds.

With the trough exiting the area and the next upstream trough moving
down the BritCol coast on Saturday, the boundary will gradually lift
back northward as a warm front. Models are increasingly latching on
to the idea that isolated to locally scattered showers and
thunderstorms will develop along the boundary. This activity could
continue through the night on Saturday.


.LONG TERM (After 12Z/6AM Sunday)...Big picture up front, the most
likely scenario supported by model guidance will feature a mean
trough developing over the West from Sunday forward. With the
development of a trough being the most likely scenario, Utah and
southwest Wyoming will see a decreasing temperature trend as well as
potential for precipitation. At this point in time there is still a
considerable amount of uncertainty in the phase and amplitude of
this trough, which will also affect how much cooling we see and
exactly where precipitation will fall. At this current time, the
best chances for temperatures falling below normal alongside a round
of precipitation is confined to the northern half of the forecast
area. Ensemble guidance from the EPS and GEFS both show another
trough diving in from the PacNW region during the second half of the
week, which would keep cooler, unsettled weather in the forecast.

Diving into a few of the details now of the more likely (~55%
probability) scenario...

By Sunday afternoon, the aforementioned trough is anticipated to
begin pushing into northern Utah. It is likely that winds will
remain elevated ahead of the associated cold frontal boundary during
the afternoon hours. Moisture lingering over the area will also be
forced along the surface front, however, the lack of deep layer
moisture will make it difficult to see any impactful rainfall. At
this point in time, there is a low (15-20%) chance for isolated
showers and thunderstorms across the northern half of Utah and
southwest Wyoming on Sunday afternoon. It is unclear how quickly
this front will progress into the region and how far south it will
progress, as models still indicate 8-10 degrees of temperature
spread in the most likely temperatures on the Wasatch Front and
Cache Valley areas.

By Monday evening, there is a nearly 50/50 split on how much this
trough will actually deepen over the West. On one hand, about 50% of
members support below average mid-level heights over Utah
(indicating a deeper trough) which would also support a farther
southward progression of the associated cold front... meaning likely
cooler temperatures in the north and at least some cooling to below
average in the south (still ~7 degrees in spread for MaxT at CDC).
Another 25% of ensemble support a shallow trough that ejects into
the Northern Plains, which would effectively allow warmer return
flow to spread over Utah Monday into Tuesday. The remaining 25% of
ensembles favor somewhere in between, where southern Utah does not
see much cooling, but northern Utah/ southwest Wyoming sees
continued below average temperatures. From a precipitation
perspective, there is a 75% chance that southern Utah will not see
much in the way of precipitation while the northern half of the area
sees at least scattered showers and thunderstorms.

Uncertainty continues through the middle of the week as models
indicate yet another trough digging into the region. Biggest point
moving forward is that there is fairly high confidence in an active
weather pattern remaining in place over the West through the
upcoming week, but just how far south this active jet stream
progresses is what we have to keep an eye on moving forward.


&&

.AVIATION...KSLC...Minimal operational concerns are forecast for the
KSLC terminal through the valid TAF period. Light southerly winds
will prevail through the mid-to-late morning, transitioning to a
northerly flow between 17-18Z.

Rest of Utah and Southwest Wyoming...VFR conditions are expected
across the area today under largely clear skies. Afternoon cumulus
buildups are anticipated across the high terrain of central and
eastern Utah, however, bases will remain at, or above, 9kft AGL.
Otherwise, light terrain driven flows are expected across a majority
of terminals.

&&

.FIRE WEATHER...High pressure will usher in warm and dry conditions
today. A trough will then graze northern Utah tomorrow. This will
push a cold front through at least northern and central Utah, and
will be accompanied by gusty winds. This front will be mostly dry,
but isolated high-based showers will be possible near the boundary,
especially across central Utah. This boundary will gradually lift
back to the north through the day on Saturday, accompanied by
isolated to widely scattered showers and thunderstorms. Unsettled
weather will then continue into early next week as the next trough
carves into the area.

&&

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

$$

Cheng/Webber

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