872
FXUS65 KSLC 182131
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
331 PM MDT Tue Jun 18 2024

.SYNOPSIS...Temperatures will trend warmer across the area through
Thursday before anomalous moisture spreads into eastern Utah late
Thursday through Friday, bringing showers and thunderstorms. Drier
conditions are expected over the weekend with hot temperatures.

&&

.SHORT TERM (THROUGH 12Z THURSDAY)...A west-southwesterly flow
aloft is in place this afternoon over Utah as a mean longwave
trough remains over the western CONUS. Several embedded
disturbances continue to ripple through the mean trough, but very
little in the way of moisture is available (0.2 inches of PWAT)
to generate any showers. Temperatures will continue to remain on
the cool side tonight, though generally warmer compared to last
night. Temperatures will be much noticeably warmer tomorrow,
given H7 warm advection as the mean trough axis retrogrades to the
West Coast. However, afternoon maxes are still expected to remain
slightly below normal.


.LONG TERM (After 12z/6AM Thursday), Issued 423 AM MDT...
Ensemble guidance remains in great agreement on a trough remaining
upstream of the forecast area through at least early Friday with
a ridge building into the area Friday through the weekend. Past
Sunday, models diverge a bit as there is some uncertainty on the
depth of a trough progged to move through southern Canada. The
depth of this trough will ultimately influence the temperature
trends (mainly in the northern area) through next week.

A trough upstream of the area during the latter portion of the week
will continue to promote warm and dry southwesterly flow over the
forecast area, allowing temperatures to warm back to above normal
levels. To the east of the area over the southern Plains, an wave
propagating to the west will interact with the upstream trough and
bring an increase in lower level flow as well as initiating a
moisture flux into the eastern Great Basin region. Increased flow in
the lower levels will bring increasing surface winds during the
afternoon on Thursday. The increase in flow will bring concerns of
elevated fire weather conditions in eastern Utah before the near
surface moisture arrives. At this time, no fire weather headlines
have been issued as fuels are not currently over their critical
thresholds in the zones of concern.

Moisture continues to work into the area through the evening hours
on Thursday, while the aforementioned trough begins shifting over
the region. Isolated showers and thunderstorms over eastern Utah
will be possible, and will carry the threat of dry lightning as the
lower level moisture lags. Should expect to see an increase in
shower activity through the overnight hours as upper level support
for lift increases. Going into Friday, upper support and increasing
moisture in the lower levels will act to destabilize the environment
and bring an increasing threat of strong thunderstorms and flash
flooding (model PWAT anomalies continue to push 200-250% of normal
over eastern Utah). Will need to continue to assess the threat of
flash flooding on Friday afternoon as models maintain abnormally
moist conditions over eastern Utah. The one concern with this is
whether or not the added dynamics from the trough will bring too
much cloud cover to destabilize the environment to the potential
that the models are suggesting. In general, if you`re planning a
slot canyon trip, you might want to hold off until late in the
weekend.

A stout ridge builds back over the region late in the weekend, which
will help to reinforce hot conditions areawide as well as provide a
drier environment. Confidence is increasing that the Wasatch Front
will be pushing temperatures to near 100 degrees and into the mid-
to upper-100s for lower elevations in southern Utah by Sunday. Will
need to continue to assess the need for heat related headlines by
Sunday as overnight lows will provide minimal recovery from the
heat. Thankfully for the northern portions of Utah and southwest
Wyoming, the heat looks to be fairly short lived as an active storm
track resumes to the north of the area, which should tamper down the
strength of the high. There is still uncertainty on how much the
high will be repressed by the northern stream, but in general we
should expect a gradual cooling trend into the middle portion of the
week across the northern half of the area. For the southern area,
heat looks to be maintained unless we can develop a deeper trough
into the CONUS (supported by ~30% of ensemble members).

&&

.AVIATION...KSLC...Northwest winds are forecast to shift southeast
around 04z this evening at light speeds. VFR conditions are forecast
throughout the forecast period.

.REST OF UTAH AND SOUTHWEST WYOMING...Calmer conditions are forecast
today with lighter winds across the region. These conditions will
persist into tomorrow morning. VFR conditions are expected for all
sites with only some lingering high based clouds in southern Utah.

&&

.FIRE WEATHER...Relatively benign weather is expected through
Wednesday with dry conditions remaining in place while
temperatures trend warmer. Southwest winds increase on Thursday
while midlevel moisture starts to spread into southeast Utah.
As the lower levels remain relatively dry on Thursday, the
increasing winds will bring isolated or marginally critical fire
weather conditions to portions of southern Utah where fuels have
cured (latest guidance only indicates localized areas with
greater than a 50% chance of reaching critical fire weather
conditions). Additionally, there will be a threat of isolated dry
lightning on Thursday. As the airmass continues to moisten across
eastern Utah into Friday, humidities will increase. Precipitation
chances will also increase across eastern Utah with a 40-60%
chance of wetting rain. Thereafter, the airmass begins to quickly
dry, although lingering low-level moisture may continue to bring a
threat of showers and thunderstorms to portions of
southern/eastern Utah on Saturday. Hot temperatures will settle
into the area for the weekend into early next week.

&&

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

$$

Cheng/Webber/NDeSmet

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