191
FXUS65 KSLC 190958
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
358 AM MDT Thu Sep 19 2024

.SYNOPSIS...Stable conditions remain in place across the region
with temperatures returning to near, or slightly below, normal on
Thursday. Dry conditions prevail until Friday/ Saturday as an
upper low moves across southern Utah and brings showers and
thunderstorms to southern Utah. Dry, seasonable conditions are
then expected for next week.

&&

.SHORT TERM (Through 12Z/6AM Sunday)...Early Thursday morning, a
closed low was located off of the Southern California coast, with
a modest northwest/southeast oriented ridge axis in place across
Utah and southwest Wyoming. Deterministic and ensemble solutions
are in good agreement regarding the large-scale pattern evolution
through the first half of the weekend, bringing the low eastward
through Southern California on Friday, across northern Arizona
Friday night, and finally through southern Utah Saturday into
Saturday night. Initial instances of precipitation are expected
to develop across southwest Utah on Friday evening, before showery
conditions overspread much of southern and central Utah on
Saturday. Mid-level cyclonic flow around the low will tend to add
a southeasterly orographic enhancement component to the
precipitation field on Saturday, tending to favor those eastern
slopes of the central and southern mountains and up into Castle
Country. The low is expected to undergo strengthening with a
noticeable TROWAL developing across Colorado by Saturday night,
with an increasingly organized trend in the QPF fields across
Colorado during this time. Most likely, healthy precipitation
associated with this phase of the low will occur east of the
forecast area, although ensemble max QPF does approach 3/4" of an
inch across eastern portions of the Uinta Basin, suggesting a
low- end chance that some of the healthier moisture could wrap
back into this area. Otherwise, highest precipitation appears that
it will be confined largely to the terrain of central/eastern
Utah, particularly those areas that perform will in moist,
easterly/southeasterly flow. Either way, for those planning to
recreate across southern/central Utah on Saturday, be prepared for
cool, damp and less than ideal conditions.

With the low tracking across southern Utah, a period of easterly
mid-level winds will develop Friday night through Saturday morning
across northern Utah and southwest Wyoming, leading to the
potential for enhanced canyon winds. An examination of the 700mb
winds, thermal gradient and pressure gradient reveals that these
parameters all fall short of typical values that would be
associated with a downslope wind event. Currently, ensemble max
wind gusts during this period max out in the 25-35 mph range,
with less than a 10% chance for gusts to reach 58 mph. Thus, this
event can be best described as an enhanced canyon wind event as
currently presented by the model solution space.


.LONG TERM (After 12Z/6AM Sunday)...Beautiful weather is in store
for the long-term period, with near-normal temperatures and mostly
clear skies.

In the wake of a closed low, shortwave ridging will build across the
area on Sunday, producing drier conditions and temperatures hovering
around normal. Monday will largely be the same, though a passing
shortwave trough sliding across northeastern UT/southwestern WY will
result in partly to mostly cloudy skies, with a few isolated showers
over the Uinta Mountains. There are still a handful of ensemble
members that favor a stronger shortwave, which could bring light
showers to more of the area, though this chance is fairly low (15%
chance).

Heading into midweek, a ridge will likely build across the area,
raising temperatures to just above normal. Model guidance hints at
another developing trough possibly late in the week, but there is
still a wide range of potential solutions.

&&

.AVIATION...KSLC...Winds will remain southeasterly through the
morning, becoming light and variable at times. Winds will then
transition to northwesterly around 17-18z. VFR conditions will
prevail with mostly clear skies.

.REST OF UTAH AND SOUTHWEST WYOMING...Largely light, diurnally-
driven winds will prevail, with VFR conditions persisting.

&&

.FIRE WEATHER...Cool, stable conditions will remain in place Friday
across the area, with good overnight recovery, with the exception
of the southeast portion of Utah. An area of low pressure is then
expected to track into northern Arizona Friday, and across
southeast Utah on Saturday. This will bring showers and a few
thunderstorms to southwest Utah late Friday, with this activity
expected to spread across much of southern, southeast and central
Utah on Saturday. The low is then expected to exit the area on
Sunday, with cool temperatures in its wake. Overnight recovery
will improve for central, southern and southeastern areas this
weekend thanks to the presence of the low. As we head into next
week, dry conditions are expected, along with near normal
temperatures for late September. At this time, no days with
critical fire weather conditions are expected, although RH is
expected to steadily dry out, especially southern areas. Overnight
recovery is expected to be largely good for northern areas
through the week, and modest for southern areas.

&&

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

&&

$$

ADeSmet/Cunningham

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