Starr, Utah Weather Forecast Discussion

031
FXUS65 KSLC 291002
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
402 AM MDT Mon Sep 29 2025
.SYNOPSIS...Low associated with unsettled weather over the weekend
will continue to lift out of the region Monday. A system will then
deepen along the Pacific coast, pushing an embedded impulse through
the area Tuesday. The broader system will start to move inland by
late in the week, likely bringing a cold front through Friday into
the weekend.
&&
.SHORT TERM (Through 12Z/6AM Wednesday)...Much quieter conditions
across the area this morning. Water vapor loop shows the once cutoff
low which brought a period of unsettled weather through the weekend
is continuing to open into a wave and eject northward away from the
region. The water vapor loop also shows a low in the Gulf of Alaska
associated with a deepening longwave trough across much of the
Pacific coast. For now though, area radars picking up on little to
no returns locally, with overnight temps generally running around 5
to 10 degrees above normal.
As the weekend system continues to depart through the day Monday,
mid level heights will trend upward and slightly drier air will push
into the region within the deeper southwesterly flow. Still, CAM
guidance suggests just enough support in combination with lingering
moisture to trigger some isolated afternoon showers and a storm or
two off the high terrain, particularly in the high Uintas. Overall
though, a much less active day appears in store along with
seasonably mild temperatures.
Monday night into Tuesday will see a lobe of the aforementioned
Pacific longwave deepen and start to push inland from the Pacific
coast. This feature will carry ample moisture (PWAT anomalies
generally at or above 150%), synoptic support, and at least some
semblance of a loose baroclinic zone as it moves in. As such,
precipitation chances will creep up as sunrise approaches, becoming
maximized late Tuesday morning into Tuesday evening as the impulse
transits the area more in earnest. While the speed of the system and
associated cloud cover will be something to watch, latest mean HREF
SBCAPE shows destabilization in the afternoon on the order of 250 to
500 J/kg, especially across the northern half of the area (roughly I-
70 corridor northward). Given some increased shear due to the
stronger mid/upper level jet support, wouldn`t be surprised to see a
stronger storm or two develop if activity remains more isolated
rather than broader/stratiform/stabler in nature. The impulse will
start to lift out of the region late in the evening hours, and with
cessation of diurnal destabilization, anticipate coverage and
strength of any remaining activity will wane pushing towards/into
the overnight hours.
.LONG TERM (After 12Z/6AM Wednesday)...An active weather pattern
will remain in place through the second half of the week and we`ll
get a taste of some fall like weather as a cold trough begins to set
its track on the eastern Great Basin region. For Wednesday and
Thursday, relatively inactive weather is anticipated to prevail as
we find Utah and southwest Wyoming under relatively dry and stable
southwesterly flow. As the aforementioned shortwave trough (short
term period) departs the region, overhead temperatures will warm as
atmospheric heights increase. As a result, temperatures at the
surface, particularly across northern Utah/ southwest Wyoming, are
expected to increase by about 5 degrees as compared to Tuesday. For
southern/ central Utah, very minimal warming is anticipated (1-2
degrees) as these areas will have not experienced the same magnitude
of cooling as the northern area. Very little change is expected
going into Thursday.
The pattern begins to shift as we head into Friday as an upstream
trough looks to begin progressing inland. Overall trends expected
with this trough moving into the region include; a significant drop
in temperature, precipitation potential across much of Utah and
southwest Wyoming, and an uptick in winds. All that said, there
continues to be a considerable amount of uncertainty to work
through, particularly with the timing and depth of the feature. We
know a trough will work its way through Utah and southwest Wyoming,
but honing in on the uncertainties will determine how widespread
precipitation becomes, how much we`ll get for valleys and mountains,
how much snow the highest elevations will get (yes... snow), and how
cold we get. Just in the past 12-hours, the EPS ensemble mean has
shown a significant slowing trend with the arrival of the trough,
with the similar run of the GEFS ensemble depicting a trough much
farther into Utah.
To give an idea of the ranges for aspects of the forecast... the
most likely (25th to 75th percentile) 24-hour precipitation forecast
from the NBM for the northern UT mountains ranges from 0 to ~0.3-0.5
inches, with the southern mountains showing upwards of a 60% chance
of no precipitation... but a 25-40% chance of measurable precip
(deeper trough solution). Even the 75th percentile snow
accumulations for the high Uintas pushes to around 1 inch.. not
much, but could bring potential road impacts for high elevation
routes. Temperature-wise, there is currently about a 7 degree spread
in Salt Lake City that ranges from 65 to 72 degrees for the 25th to
75th percentile. This spread increases to around 10-11 degrees the
farther south you go. In the Cache Valley, a similar spread is
observed for daytime temperatures, however, overnight lows also
range from 4 degrees ABOVE freezing to 4 degrees BELOW freezing on
both Saturday and Sunday morning.
Bottom line, expect things to cool off as we head into the weekend
even if we don`t get any precipitation. Anticipate at least some
light rainfall in the northern Utah mountains, with light snow
accumulation potential above about 10,000ft. Temperatures near to
slightly below average are likely (75% chance) to persist into early
next week.
&&
.AVIATION...KSLC...VFR conditions prevail through the valid TAF
period under increasing low to mid-level cloud cover during the
afternoon hours. South winds will be dominant through the first half
of day, with gusts to around 17-22kts between 15-18Z. After about 21-
22Z, winds will attempt to switch to a WNW flow. There is about a
45% chance that south winds prevail through the day.
.Rest of Utah and Southwest Wyoming...VFR conditions are expected
across a vast majority of Utah and southwest Wyoming today as
conditions dry. Isolated showers are expected to develop over the
high terrain features, potentially obscuring the highest elevations
in the central Wasatch and Uinta Mountains. Otherwise, southerly
winds will be dominant across much of the area with speeds around 5-
10kts. For areas not experiencing south winds, anticipate light
terrain driven flows... mainly across the eastern area.
&&
.FIRE WEATHER...The cutoff low which served as the primary influence
to the weekend`s weather will continue to lift out of the region
through the day Monday. Drier air will start to move in, and
overall support will be more meager, but some isolated showers and
thunderstorms will develop off the high terrain, especially
around the Uintas. Deep southwesterly flow will then begin to
increase in advance of a deepening Pacific system. This system
will send an associated impulse through the area Tuesday, with
sufficient moisture to bring about more widespread precipitation
potential. Support and potential for wetting rains will be highest
generally along/north of the I-80 corridor or so. Drier air will
return through midweek with maintained southwesterly flow as the
broad Pacific system continues to deepen and slowly penetrate
inland. Less certainty is noted in the speed/strength of the
inland penetration, but general model consensus suggests potential
for this to bring a more robust cold front through the area
Friday into the weekend, accompanied by precipitation, as well as
a marked cooldown in its wake.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&
$$
SHORT TERM...Warthen
LONG TERM...Webber
AVIATION...Webber
FIRE WEATHER...Warthen
For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity

NWS SLC Office Area Forecast Discussion