Marriott, Utah Weather Forecast Discussion

388
FXUS65 KSLC 282200
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
400 PM MDT Sun Sep 28 2025
.SYNOPSIS...Unsettled conditions are expected to continue through
Tuesday. A broader system deepening into the Pacific coast then
looks favored to shift inland through midweek, and eventually push a
cold front through the area Friday into the weekend.
&&
.DISCUSSION...The upper low currently over northwest Arizona
continues to fill as it lifts northeast towards the Four Corners
area. Moisture has already spread into Utah ahead of it, with PWAT
analysis showing around 0.8 inches across the vast majority of the
area (with a small area of around 1 inch across far southwest Utah).
This moisture, combined with daytime heating aiding SBCAPE of up to
1 kJ/kg, along with some forcing owing to the ejecting low, has
brought scattered to numerous showers and thunderstorms to the area
this afternoon. Many of these showers have been focused over the
mountains and eastern Utah valleys, and are expected to continue
into the evening hours before diminishing. Locally heavy rain and
perhaps isolated flash flooding will be the main impacts.
The storm system will exit into Colorado tomorrow, while the next
upstream trough will approach the West Coast. Between these two
features, a drier southwesterly flow will develop into Utah tomorrow
afternoon. That said, lingering low level moisture could aid in the
development of a few generally weak showers and thunderstorms during
peak daytime heating tomorrow afternoon. These will likely be
confined to over or near the northern Utah mountains where the
greatest instability will exist.
The upstream trough will shift inland tomorrow night before
weakening and lifting across northern Utah on Tuesday. Northern Utah
has a good chance of seeing precipitation on Tuesday as the trough
moves across the area. However, only slight cooling is expected
behind the weakening cold front. Models are still in fairly good
agreement with this solution, with cluster analysis showing only
very subtle differences between the various clusters. That said,
there is some model spread with respect to precipitation amounts,
with the wetter two clusters making up 70% of the members versus 30%
for the drier solutions. However, even these wetter clusters are
showing cluster mean 24h precipitation totals of only up to around
0.25 inches, and even the 90th percentile amounts generally remain
under 0.5 inches.
After this trough exits the area, a drier and warmer southwest flow
is expected to develop into the area once again on Wednesday as yet
another storm system deepens over the PacNW coast. Breezy conditions
could be in store for the area on Thursday as this storm approaches
Utah. However, quite a bit of uncertainty remains with the strength
and timing of this system, with around 60% of ensemble members going
for a faster/weaker evolution compared to 40% for a slower/deeper
one. However, the latter solution would have the potential to bring
noticeably cooler temperatures and widespread precipitation to the
area.
&&
.AVIATION...KSLC...Scattered showers will taper off from 00-03Z.
Clouds will decrease, with mostly clear conditions by 03Z. Southeast
winds will last through 15Z, with speeds to around 15 knots. Mostly
clear conditions will continue through the day. Winds will
transition to south around 15Z, with gusts around 20 knots.
.REST OF UTAH AND SOUTHWEST WYOMING...Scattered showers and isolated
thunderstorms will taper off from 00-03Z. Clouds will decrease as
precipitation tapers off, with mostly clear conditions throughout
southwest Wyoming and Utah by 06Z. Winds will generally range from
south to southwest. Wind gusts will be around 20 knots for many
locations after 18Z.
&&
.FIRE WEATHER...A storm system will continue to gradually weaken as
it ejects across the Four Corners region tonight. Moisture that has
spread north through Utah is helping to produce scattered to
numerous showers and thunderstorms which will continue across Utah
into the evening hours. Wetting rain will continue to be likely
under the stronger storms. As the next storm system approaches the
area from the west tomorrow, expect a slight drying trend as
southwesterly flow develops ahead of it. However, lingering low
level moisture could lead to a few generally weak showers and
thunderstorms mainly over the northern Utah mountains tomorrow
afternoon. This storm system will then lift across northern Utah on
Tuesday. Since it will be weakening, would not expect a strong cold
front, with temperatures only cooling slightly behind it. However,
showers and thunderstorms do look like a good possibility, at least
across northern Utah, on Tuesday. Once that storm system moves east
out of Utah Tuesday night, a drier and warmer southwest flow looks
to settle into the area again for Wednesday and Thursday as yet
another storm system starts to strengthen to the west. Details
relating to the timing and strength of this next storm still needs
to be worked out, but currently, it looks like there is a potential
for a stronger cold front late week which could bring cooler
temperatures and another round of precipitation.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&
$$
Cheng/Wilson
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NWS SLC Office Area Forecast Discussion