Daniels, Utah Weather Forecast Discussion

532
FXUS65 KSLC 050956
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
356 AM MDT Fri Sep 5 2025
.SYNOPSIS...Moist and unstable pattern to continue to support more
widespread shower and thunderstorm coverage through the weekend,
and an associated localized flash flood threat. Somewhat drier
conditions are expected to return by early next week.
&&
.SHORT TERM (Through 12Z/6AM Sunday)...Enhanced shortwave energy
associated with a slowly propagating shear axis in combination
with ample moisture (PWAT values over 1.00" in SW UT) has resulted
in a more active night. Area radars have tracked a convective
complex (now departing further into AZ/NV) moving through SW UT,
taking advantage of this environment and at times producing rain
rates in excess of 1" an hour. So far it seems the fast forward
motion of this complex has limited the overall flash flood threat,
but will need to continue to monitor area rivers/streams/washes
for any response more significant response than has already been
observed. All the same, those in the area should be aware that
some water could be flowing in some of those typically dry washes,
and given it`s the overnight period, may want to exercise extra
caution if passing through any low water crossing type of route.
In general, CAM guidance favors decreasing activity moving towards
sunrise.
Friday`s weather evolution does not appear likely to be too
dissimilar to that of Thursday given more or less the same
dominant synoptic features. The aforementioned axis will continue
to very slowly lurch through the moistened forecast region
characterized by PWAT anomalies roughly in the 140-180% of normal
range. HREF shows fairly widespread diurnal destabilization with
widespread MUCAPE values in the 250-500 J/kg range late morning to
early afternoon, with further increases into the 750-1250 J/kg
range noted across SW UT. As such, CAM guidance shows convective
development by early afternoon. Once again anticipate the primary
threat to be in the form of a localized flash flood potential,
especially for rain sensitive basins. WPC in turn once again has
maintained a Marginal Risk (categorical 1 of 4) for excessive
rainfall from southern to central Utah accordingly. Locally, have
maintained a broader assortment of "Probable" ratings in the Flash
Flood Potential Index for southern Utah recreation areas, with
"Possible" ratings elsewhere. Those planning potential recreation
at such rain sensitive areas should consider alternatives, or at a
minimum remain very weather aware. While coverage and intensity
of activity will wane after sunset, CAMs maintain some nocturnal
showers/thunderstorms lifting back northeastward through UT as
deep flow aloft begins to shift more southwesterly and another mid
level shortwave impulse noses in.
While the synoptic pattern does begin to shift somewhat Saturday,
it appears favorable to be another active day in this stretch of
many. One of the biggest changes appears to be the deep flow
remaining more southwest to westerly with a bit more flow in
general. Ensemble PWATs dip slightly, but moisture remains plenty
sufficient for some wetter type thunderstorm develop in the face
of diurnal destabilization and some continued support from
shortwave energy. In regards to destabilization, HREF mean MUCAPE
actually increases slightly in comparison to Friday across most of
the area. One caveat though may be how the overnight nocturnal
precipitation has evolved (or cleared) through the morning, as it
could provide a stabilizing effect wherever it and associated
cloud cover may be lingering. All the same, what thunderstorms do
develop through the day will have a continued threat of locally
excessive rainfall, and an areawide Marginal Risk of excessive
rainfall is noted per WPC.
.LONG TERM (After 12Z/6AM Sunday)...Ensembles continue to support a
longwave trough phasing into a closed low off the coast of
northern California on Sunday, introducing drier southwesterly
flow aloft. This pattern will allow monsoonal moisture to
gradually wane from west to east, resulting in less convective
activity on Sunday afternoon. Best coverage for afternoon showers
and thunderstorms will favor northeast Utah and southwest Wyoming
where monsoonal moisture will linger just a bit longer. Otherwise,
more isolated coverage is expected across the remainder of the
forecast area. With PWAT anomalies still in the 125 to 150 percent
of normal range, locally heavy rainfall will remain a threat for
any stronger cells that develop. Drier conditions throughout the
column may also support gusty and erratic outflow winds to 40 mph.
The aforementioned low begins to nudge inland into northern
California on Monday into Tuesday, resulting in limited convective
activity and breezy winds developing on Monday afternoon. The low
will continue to slowly meander eastward through Thursday, with
an associated upper-jet strengthening across the region through
this period. Gusty southwesterly winds are expected to develop
areawide each afternoon as a result, with strongest winds favored
on Tuesday and Wednesday across southern Utah, where gusts to
30-35 mph are possible. Winds remain elevated Thursday, before the
low ejects eastward out of our region Friday.
&&
.AVIATION...KSLC...VFR conditions prevail at the terminal through
the period. Winds remain generally light and diurnally driven,
with southeasterly winds this morning transitioning northwesterly
after 19z. Some nocturnal showers are possible overnight tonight
into early Saturday morning, though chances of impacting the
terminal remain less than 30%.
.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions expected
through the period for all regional terminals. Nocturnal showers
ongoing across far southwestern Utah this morning are expected to
taper off by 12z, with conditions briefly clearing out before
widely scattered showers and thunderstorms develop across the
airspace once again this afternoon. Storms that develop will be
capable of producing locally heavy rain and erratic winds, with
potential to push CIGS into MVFR/IFR levels under heavier cores
through this evening. Some nocturnal showers developing over the
West Desert of Utah may bring showers into early Saturday morning
for southern Wasatch Front terminals.
&&
.FIRE WEATHER...Monsoonal moisture is expected to peak across the
region today into Saturday, resulting in widely scattered showers
and thunderstorms across the state each afternoon and evening.
Given anomalously high moisture, storms that develop during this
period will be wet in nature, and in conjunction with slow storm
motions produce an increased risk for flash flooding in rain
sensitive areas such as recent burn scars. Daytime RH values
continue to climb through Saturday in response to this monsoon
surge, with good to excellent overnight recoveries through Sunday
morning.
Drier conditions develop on Sunday as a system approaching the
west coast brings dry southwesterly flow aloft. Convective
activity looks more isolated on Sunday afternoon as a result, with
greatest activity over northern Utah where sufficient moisture
still lingers. This drying trend continues through at least the
end of the work week as this system becomes stalled over northern
California on Tuesday. The placement of this system Tuesday
through Thursday will be favorable for gusty southwesterly winds
across the state, most notably across southern Utah where
afternoon gusts may exceed 30 mph. Considering the drying trend
through this timeframe, these gusty winds may lead to periods of
elevated fire weather conditions.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&
$$
SHORT TERM...Warthen
LONG TERM...Whitlam
AVIATION...Whitlam
FIRE WEATHER...Whitlam
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http://weather.gov/saltlakecity

NWS SLC Office Area Forecast Discussion