997
FXUS65 KSLC 251028
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
428 AM MDT Tue Jun 25 2024

.SYNOPSIS...Hot and dry conditions will continue across northern
Utah while showers and thunderstorms continue to be a threat
across southern Utah. By Wednesday, the threat of showers and
thunderstorms will spread across the state. Another round of
strong thunderstorms is expected Thursday afternoon and evening.

&&

.SHORT TERM (Through 12Z Thursday)...While late June is
climatologically one of the driest part of the years for Utah,
the last few days have been anything but typical. Morning upper
air and satellite analysis indicates a broad upper level ridge
remains in place across the southern Plains/southern Rockies. An
atypically strong upper level trough is approaching the Pacific
Northwest. PWs remain quite elevated, averaging around 1-1.25"
across the lower valleys of southern Utah, around 0.50-0.75 across
the remainder of southern Utah.

Much of southern and eastern Utah will see SBCAPE values
approaching 500-750 J/kg by this afternoon. With deep layer shear
less than 20 kts and relatively slow storm motions, the most
significant threat will again be flash flooding with any
thunderstorms that form across southern and eastern Utah this
afternoon and evening.

Guidance suggests an MCV related to convection currently in
northern Mexico/farther southern Arizona will rotate north around
the upper level ridge and may bring the threat of nocturnal
convection to Utah by tonight. Per usual, models are having a
difficult time resolving this feature.

By Wednesday, the upper level trough will be crossing the Pacific
Northwest. This will help to substantially increase deep layer
shear across much of the Utah and also help to push a relatively
moist airmass northward. Expect widespread showers and
thunderstorms to develop by Wednesday afternoon and evening, with
the continued threat of heavy rain...and potentially small hail
and gusty winds.

Hot temperature are again expected across northern Utah this
afternoon and evening. Overnight lows have trended cooler than
previously expected...but kept going heat products given
temperatures will once again approach the century mark across the
Wasatch Front.

.LONG TERM (After 12Z Thursday)...A progressive pattern will
develop for the long term period as the ridge of high pressure
responsible for the recent heat will shift east into the southern
CONUS. Ample moisture will only be in place on Thursday as the
first trough pushes through to our north. A dry airmass will be
ushered in behind the aforementioned trough. This airmass will
help to cool temperatures briefly, but the dry conditions will
persist through the remainder of the period. This dry airmass will
pair with windy conditions as another trough moves into the
region this weekend resulting in favorable fire weather
conditions.

The approaching trough on Thursday will pair with PWATs (~1.2"
for KSLC) approaching climatological maxes for this time of year.
Forecasted CAPE values near 1000 J/kg and bulk shear >50kts will
create an atmosphere conducive for strong to severe thunderstorms
across the CWA. The limiting factor, however, will be how much
precipitation and cloud cover will be lingering across the region
from the previous days convective activity. A lot of the hi-res
guidance does keep precipitation ongoing Wednesday night into the
morning on Thursday. If these showers are able to dissipate early
enough then the atmosphere could become primed for strong
thunderstorm development as the axis of the trough passes through
Utah and SW Wyoming. In addition to the threat of severe weather,
flash flooding will also be a concern across flood prone regions
such as dry washes, slot canyons and burn scars.

This precipitation will quickly shift east and out of the CWA
late on Thursday as drier and cooler air advects in behind the
frontal passage. Friday`s high temperatures will be the coolest of
the long term period with near normal temperatures. Shortwave
ridging will temporarily build back into the area on Saturday
leading to high temperatures returning to ~5 degrees above normal.
Similar temperatures on Sunday along with increasing
southwesterly flow ahead of our next trough will lead to gusty
winds developing across most of the CWA. The dry airmass will be
characterized by minimum relative humidity values <15% for the
afternoon on Sunday. The trough axis will push east of us on
Monday with temperatures the remainder of the period returning to
near normal and winds weakening slightly, but staying elevated.

&&

.AVIATION...KSLC...VFR conditions will persist for the KSLC
terminal. Skies will be mostly clear with light diurnally driven
winds.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will persist
for the airspace throughout the period. Expect dry conditions
with light and variable winds across the northern two thirds of
the airspace with scattered afternoon convection developing for
the southern third. These storms will be capable of producing
gusty and erratic winds.

&&

.FIRE WEATHER...Another day of anomalously high moisture across
the south, with dry and hot conditions across the north. By
Wednesday, an upper level trough will be crossing into the Pacific
Northwest. This increase in flow combined with several subtle
disturbances rotating through Utah will support more widespread
convection and increasing humidities through the state. By
Thursday, a dry slot will start nosing into western Utah while
widespread convection continues across the remainder of the state.
This may bring at least localized critical fire weather
conditions to portions of western Utah. A cold front will cross
the state late Thursday into Friday. A much drier airmass will
build into the state Friday, with the threat of critical fire
weather conditions in locations where fuels are conducive. This
threat may extend through the weekend.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Excessive Heat Warning until 11 PM MDT this evening for UTZ101-
     104>106-116.

     Heat Advisory until 11 PM MDT this evening for UTZ102-103-107-
     118-119.

WY...None.
&&

$$

Kruse/Mahan

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