Holladay, Utah Weather Forecast Discussion

403
FXUS65 KSLC 192206
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
406 PM MDT Fri Sep 19 2025
.SYNOPSIS...Moisture continues to stream north into UT with
showers and thunderstorms ongoing across southern UT. Convection
will begin to taper off around sunset with chances for storms
increasing across northern UT and southwest WY tomorrow afternoon.
A drying period is expected to develop on Monday.
&&
.SHORT TERM (Through 12Z/6AM Sunday)...Shortwave upper trough is
currently over CA/NV progressing NE with time, slightly eroding the
eastern edge of an upper ridge over the Southwest. Satellite imagery
through the morning has shown quite significant clearing across
southern UT which has resulted in notable mixing across southern UT
which dropped observed PWATs across the state to less than an inch
up until the past hour. Some recovery is expected with the majority
of hi-res guidance indicating that PWATs in excess of 1" will
overspread most of southern UT within the next few hours with
locally higher PWATs across Washington county. However, lower
residence time with the moisture across southern UT has resulted in
shallower moisture with ample dry air aloft evident on soundings.
This will generally inhibit how robust storms that form today can
get and likely result in more short lived storms than anything. The
highest confidence with respect to storm coverage resides across the
higher terrain of southern and central UT where storms may become
anchored to / form off the terrain and sustain themselves for
longer. However, some surface convergence along the eastern edge of
the nose of moisture pushing in across SW UT appears possible which
may compensate for lack of overall ascent today. Hi-res guidance has
hinted that there could be some locally heavier rates just north of
the AZ border from Zion NP toward Buckskin Gulch in the early
evening. Confidence in this solution remains low but bears watching.
Following sunset, convection is expected to weaken with a lull in
activity until tomorrow afternoon. Eyes shift toward northern UT and
southwest WY where shallow midlevel moisture will advect overnight
tonight. Weaker forcing remains in place as the shortwave continues
to slide northeast resulting in PoPs around 30-50% across northern
UT and southwest WY with the higher PoPs generally occurring where
orographic forcing is favored. With the bulk of moisture remaining
in the midlevels, gusty showers and dry thunderstorms are the
favored convective mode tomorrow with gusts to around 40mph
appearing increasingly likely. Some wetter storms are possible over
the higher terrain across northern UT given PWATs in excess of 1",
particularly across the Uintas, though for most lower lying areas,
dry thunderstorms appear to be the most likely outcome for tomorrow.
Once again, storms should begin to diminish around sunset with
another calm night on tap. Some lingering showers appear possible
overnight across far northern UT where moisture may hang around for
a while, though these showers are not expected to be substantial.
.LONG TERM (After 12Z/6AM Sunday), Issued 933 AM MDT...
By Sunday, a drying trend will
already be in place across the forecast area under subtle ridging.
Scattered showers and thunderstorms will develop mainly across
higher terrain, particularly across northern Utah/southwest Wyoming
where moisture will hang on for a bit longer.
Models have trended slightly cooler and wetter on Monday, with an
overall shift in guidance from a grazing trough to one that moves
through northern Utah/southwest Wyoming on Monday. Compared to
yesterday, ensemble membership for this solution has increased from
19% to 52%, with deterministic solutions now on board. Still, about
half of members favor that grazing trough, which would result in
drier conditions. In either scenario, a much drier air mass will
move in behind the trough, with high pressure building overhead.
The next area of uncertainty is the development of a closed low over
SoCal early in the week. Model guidance has been bouncing back and
forth with its eventual trajectory. If the closed low does move
inland and over Utah, this could bring another round of cooler and
wet weather late in the work week...though forecast confidence is
very low at this point.
&&
.AVIATION...KSLC...VFR conditions will continue with SCT-BKN mid-
level clouds. Northerly winds should become dominant until 03-04z,
with a 10% chance of high-based showers until about 01z, which would
be accompanied by gusty and erratic winds. A greater chance of
showery activity could impact winds at the terminal between 06-12z.
.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will
persist through the TAF period. Current storm activity near the
southern terminals is expected to die down by sunset, with diurnal
winds in place through the evening. Northern terminals except LGU
and possibly OGD can expect a chance of showery activity causing
gusty and erratic winds at terminals between 06-12z.
&&
.FIRE WEATHER...High pressure continues to slowly push east as a
storm system pushes in from our west. Southwesterly winds persist
through the duration of the weekend pumping in moisture to the state
raising humidities and chances for showers and thunderstorms. This
afternoon, storms will generally remain confined to southern and
central UT. Tomorrow and Sunday, moisture pushes north increasing
the chances for showers and dry thunderstorms across northern UT.
Dry thunderstorms appear most likely on Saturday and perhaps Sunday,
though more moistening Sunday could result in better chances for
rain to reach the ground. On Monday, we begin to see a drying trend
take hold as winds begin to clock to northwesterly, though some
isolated showers and thunderstorms remain possible across northeast
UT and the higher terrain of east-central UT.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&
$$
SHORT TERM...Worster
LONG TERM...Cunningham
AVIATION...Verzella
FIRE WEATHER...Worster
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NWS SLC Office Area Forecast Discussion