Text Products for AFD Issued by SLC

Area Forecast Discussion
Issued by NWS Salt Lake City, UT
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FXUS65 KSLC 230954
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
354 AM MDT Tue Apr 23 2024

.SYNOPSIS...Above average temperatures remain in place through
mid-week as high pressure dominates. A closed low system will
progress inland through the second half of the week, bringing
cooler and wetter weather into the weekend.

&&

.SHORT TERM (Through 12Z/6AM Thursday)...A weak boundary continues
to lift out of the region today, allowing for slowly warming
temperatures across the northern third of the forecast area. A
mid-level moisture axis will remain draped across the northern
third of the area as well, bringing increased cloud cover and a
few light mountain showers. It is unlikely that precipitation will
reach the ground given how dry the near surface environment is,
however, if anything does reach the surface it should be quite
negligible (i.e. trace amounts). With a touch of mid-level
instability and afternoon solar insolation, can`t rule out an
isolated, short-lived thunderstorm.

Pushing into Wednesday the pattern begins to change as a mid-level
ridge axis begins shifting downstream of the area, opening the
door to a closed low system. As this ridge axis shifts downstream,
increasing moisture will be introduced to the region which will
allow for increased chance of seeing measurable precipitation,
mainly across the northern reaches of the forecast area. Further
warming of the airmass is expected across the northern half of
Utah and southwest Wyoming, however, a slight cooling trend will
be noted across the southern half of Utah as the influence of the
closed low begins to spread into the Southwest.

.LONG TERM (After 12Z/6AM Thursday)...The long term portion of the
forecast period begins on Thursday with the closed low over SoCal
opening up and ejecting across northern AZ/southern UT.
Deterministic models and associated ensemble members are now in
fairly good agreement regarding this evolution. Some shower activity
looks possible in the warm sector ahead of the trough axis, firing
up along the spine of the central mountains through the western
Uintas. Behind the associated cold front, additional showers are
progged to spread in from the northwest through the day. While
temperatures cool, the airmass will remain mild enough to maintain
relatively high snow levels through the day, around 8.5-9kft.

Additional trailing features will quickly follow the initial trough,
leading to the development of a mean longwave trough over the
Western CONUS which will continue to bring unsettled weather into
the weekend. Within this wave train, the next trough, a more subtle
shortwave disturbance, is expected to cross the area Friday
morning/afternoon, followed by a deeper trough Friday evening/
Saturday morning. Cluster analysis of ensemble members show mainly
small differences in timing and amplitude of the trough pattern. As
such, confidence is high in the overall pattern and evolution, with
some uncertainty with the details. Friday looks to be the wettest
day of this stretch of wet weather. PWAT anomalies in the 97th
percentile of climatology are noted across portions of Utah on
Friday, and ECMWF-based Extreme Forecast Index shows a signal for
abnormally high QPF as well. Current forecast is carrying a 2.5-day
total (Thurs morning through Saturday afternoon) of over 1.5 inches
of QPF over the ridgelines, and around 1 inch or more in the
adjacent valleys.

Colder temperatures will be associated with the Friday and Saturday
systems. Widespread below normal afternoon max temperatures are
expected both days, and snow levels are expected to fall to between
7-8kft. As such, expect mountain snow accumulations, potentially
significant above 8kft. Still questionable at this time whether this
will result in any signficiant impacts owing to sun angles and road
temperatures.

There remains some uncertainty as to how quickly the storm
systems exit the area. Deterministics have precipitation largely
winding down by Saturday evening, although cluster analysis
indicates a bit more spread. However, by Sunday afternoon, all
clusters show the trough already east of Utah. Uncertainty increases
again after that, but expect a general warming and drying trend
through the early part of next week.


&&

.AVIATION...KSLC...VFR conditions will be maintained over the KSLC
terminal through the valid TAF period. Mid-level cloud cover will
remain in place through much of the day, only dissipating for a
brief period mid-morning. Light and variable flow early this
morning will return to a northerly flow around 16-17Z.

.Rest of Utah and Southwest Wyoming...VFR conditions will remain
in place through the valid TAF period across Utah and southwest
Wyoming. Mid-level cloud cover, with elevated showers, will
prevail across the northern half of the area. Winds across the
northern third of the area will remain out of the north. For the
southern two-thirds, expect predominantly southwesterly winds with
afternoon gusts to around 25-30 mph.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

SHORT TERM...Webber
LONG TERM...Cheng
AVIATION...Webber

For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity
National Weather Service Weather Forecast Office
