728
FXUS65 KSLC 242138
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
338 PM MDT Fri May 24 2024

.SYNOPSIS...Increasing moisture will bring a chance for rain this
evening and overnight from southwest Utah to southwest Wyoming. A
frontal boundary will bring widespread rain with embedded
thunderstorms across much of the state tomorrow. A cool, stable
airmass will shift into the area for Sunday, followed by a
substantial warming trend early next week.

&&

.SHORT TERM (Through 12Z/6AM Sunday)...Mid and high based cloud
cover are sandwiched between fairly clear skies in northern and
southern Utah this afternoon. Headed into the evening and
overnight, increasing moisture will further enhance cloud cover
and increase chances for rain production across much of central
Utah while a frontal boundary continues to meander across the
state. There actually looks to be a fairly large swatch of rain
activity from the southwest corner of Utah (north of the Pine
Valley Mountains) to southwest Wyoming. This line is expected to
extend as far north as Utah/Wasatch Counties but stay south of
Salt Lake City. But that said, there is around a 20% chance for
rain in SLC this evening. This will also be when snow showers
begin in the higher elevations of the western Uintas, where snow
is expected to continue to fall through tomorrow. Accumulations
above 9000 ft are forecast in the 8 to 10 inch range.

Early tomorrow morning, a shortwave trough will be making its way
toward the region with a frontal passage forecast during the day.
Generally speaking, Saturday is expected to be a cool and soggy
one. The front is expected to cross the Wasatch Front during the
late morning/early afternoon hours, bringing cooler temperatures,
widespread rain and embedded thunderstorms. There is little to no
threats for any severe weather with this line moving through and
marginal, at best, threats for small hail. The main concerns
tomorrow will be with gusty winds associated with these
thunderstorms. As the frontal boundary passes through eastern
Utah, there`s a greater than 50% risk for wind gusts to exceed 40
mph especially after 3 pm.

South of the boundary, expect breezy westerly winds throughout
much of the day tomorrow. Gusts of 30 to 40 mph are expected
especially across Bryce Canyon and the Grand Staircase, but we
are shy of wind advisory criteria and will not be issuing at this
time.

High temperatures Saturday across many valleys will be in the
modest 60`s. Even the greater St. George area will feel a slight
cooling; climbing just over the 80 degree mark tomorrow.

Flow will remain northwest to west Saturday night into Sunday and
allow for a general drying trend. A 20% or less chance for
additional rain showers will exist during this period as a
result.

.LONG TERM (After 12Z/6AM Sunday), Issued 309 AM MDT...
Beginning on Sunday, a return to summer-like weather will begin
to make an appearance across Utah and SW Wyoming in the wake of
our departing storm system with temperatures beginning to rise. A
more substantial increase in temperatures will begin on Monday,
when temperatures will rise ~10F across the north and ~5F across
the south. Deterministic and ensemble guidance is in good
agreement in building a high pressure ridge across the region
through early next week, and this feature will be responsible for
the warming/drying trend. The warmest day of the period (and the
year to date) is now most likely on Tuesday. This is when high
temperatures will soar into the upper 90s across Lower Washington
County to the upper 80s across the Wasatch Front. Latest NBM shows
a 27% chance of reaching 90F at SLC on Tuesday. With enough
southerly downslope influence and enough sunshine, this
probability could be a bit conservative.

Forecast certainty does begin to wane slightly by midweek, as
differences emerge regarding the evolution of the mid-level ridge as
well as potential interactions with an incoming PacNW trough, with
notable strength and timing differences apparent across the solution
space. By Wednesday, 80% of the solution space shifts the ridge axis
off to the east, suggesting a slight cooling trend will emerge. As
we head into the Thursday-Friday timeframe, around 1/4 to 1/3 of the
solution space drops a trough across the Northern Rockies, with a
similar sliver of the remaining solution space representing either
zonal flow or the ridge simply staying put. Through this analysis,
we see 3 possible forecast outcomes in the Thursday to Friday
timeframe. We`ll call scenario 1 the outcome that keeps the ridge in
place; and this would imply maintenance of warm/dry conditions.
Scenario 2 with its transition to the zonal flow regime would suggest
temperatures cooling back down near seasonal normals across the
north along with little change in temperatures across the south.
Additionally, a low chance for a few showers/storms across northern
Utah/SW Wyoming may accompany said pattern shift. Finally, scenario
3 with the stronger Northern Rockies trough would suggest
temperatures cooling to slightly below normal across northern
Utah/SW Wyoming with only modest cooling across southern Utah, along
with higher chances for showers across the north. At present, all 3
scenarios are essentially equally possible forecast outcomes, and
the official blended/calibrated forecast falls more in line with
scenario #2 and its zonal flow regime. As we get closer to this
period of greatest uncertainty, we`ll continue to monitor trends to
observe which one of these outcomes becomes the most dominant
outcome.

&&

.AVIATION...KSLC...VFR conditions will persist for the KSLC
terminal through the period. Winds will be variable this afternoon
as a northerly lake breeze is countered by southerly outflow from
showers south of the terminal. A predominant southerly flow
establishes this evening/overnight, but VCSH could create more
brief variability in the winds. Expect CIGs to develop near
ridgetop creating some mountain obscuration overnight.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will persist
for most terminals this evening and overnight. High based showers
across central Utah will create some gusty outflow leading to
variable winds with a mean southerly flow, otherwise. CIGs lower
overnight with showers becoming more numerous across central Utah
with intermittent mountain obscuration. Winds predominantly remain
southerly with mostly dry conditions across southern Utah.

&&

.FIRE WEATHER...Increasing statewide moisture tonight is forecast
to lead to further cloud cover and increasing risk for rain showers.
Wetting rains are expected to be highest across central Utah this
evening which will inch northward overnight. There is risk for
isolated gusty outflow winds or microburst winds in any
thunderstorms that may develop. Headed into tomorrow, widespread
rain and thunderstorms are forecast along and north of I-70. The
highest risk for gusty winds looks to be in eastern Utah as the
frontal boundary passes, where there`s a greater than 50 percent
likelihood for wind gusts to exceed 40 knots. These winds are
expected to be strongest between approx 1500 hrs and 1900 hrs.
South of the boundary, look for breezy westerly winds. By Sunday,
conditions are forecast to dry out across the region with a west
to northwest flow expected.

&&

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

$$

NDeSmet/ADeSmet/Mahan

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