835
FXUS65 KSLC 110939
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
339 AM MDT Tue Jun 11 2024

.SYNOPSIS...Very hot temperatures will build into the region
Wednesday into Thursday, with the potential for the Wasatch Front
to breach the century mark. An upper level low may bring cooler
temperatures and precipitation by Friday.

&&

.SHORT TERM (THROUGH 00Z FRIDAY)...Current large-scale pattern
depicts a broad but generally low-amplitude ridge building into the
Great Basin while a cutoff low continues to meander along the Baja
Coast. Utah remains mostly cloud-free this morning with the
exception of far southeast Utah as a drier airmass continues to work
into the area. A few high-based showers remain possible this
afternoon from what is left of the moisture, with most CAMs
indicating weak activity over portions of the southern mountains
through the east-central valleys.

Temperatures will be the main issue for the short-term forecast
period. Underneath the building ridge, the airmass will trend
warmer. Global deterministic models indicate a dome of H7
temperatures of 17-18C by Wednesday and around 16-17C for Thursday.
Each of these two days will see temperatures well above
climatological normals for this time of year. Even though H7
temperatures are slightly cooler on Thursday compared to Wednesday,
increasing southerly flow will aid in mixing. On the other hand,
there is also the potential for increased sky cover on Thursday.
Nevertheless, HeatRisk (though slightly less excited compared to
previous forecasts) continue to show enough of a threat of excessive
heat to warrant an upgrade from an Excessive Heat Watch to a Warning
for the Glen Canyon zone. Have contemplated heat highlights for
other zones as well. However, the St. George zone ended up being
more marginal. Some northern valleys may eventually need highlights
as well, but this looks more like Advisory level with the best
chance on Thursday, so have opted to punt to future shifts. It
should be noted, however, that the latest NBM has a 38% chance of
SLC reaching 100F on Wednesday and a 48% chance on Thursday.


.LONG TERM (After 00Z Friday/6PM Thursday)...Friday marks the
transition to more unsettled weather across northern UT and
southwest WY, at least to start the long-term period. A closed low
over SoCal will weaken as it moves inland, tracking across
southeastern UT on Friday and bringing a decent mid-level moisture
surge with it...PWATs across southeastern UT jump from an ensemble
mean of 0.35" up to 0.75". Thus, scattered showers will develop in
eastern UT beginning late Thursday night, with thunderstorms and
high-based convection developing Friday afternoon. Temperatures will
also decrease across the area on Friday, with eastern UT seeing the
largest decrease by about 10-15 degrees as compared to Thursday
afternoon highs.

Moving into the weekend, our sensible weather starts to be
peripherally influenced by a low pressure system settling over the
PacNW, though the air mass remains quite dry. Currently, the biggest
impact looks to be a cooling trend beginning Saturday, mainly across
northern areas. Model guidance really starts to diverge in the upper-
level pattern on Sunday, which will ultimately determine the extent
of this cooling trend across the area. Ensemble members are split
roughly 70-30, with 70% of members favoring a stronger cooldown on
Sunday into Monday, associated with a more amplified trough. The
other 30% favor not much of a cooldown at all. To further illustrate
the high uncertainty, highs at KSLC on Monday range from 70F to 85F
(25th to 75th percentiles). In St. George, this range isn`t quite as
big, but still ranges from 92F to 100F.

&&

.AVIATION...KSLC...Light, southeasterly winds will continue until a
transition to northwesterly around 17-18z. Winds may become light
and variable at times during the morning.

.REST OF UTAH AND SOUTHWEST WYOMING...Light, diurnally-driven winds
will prevail, aside from some gusts to 20kts out of the west across
Uinta Co., WY and the western Uinta Basin after 18z. VFR conditions
will prevail.

&&

.FIRE WEATHER...High pressure will build back into the area through
Thursday, bringing hot, dry, and increasingly breezy conditions.
The hottest days are expected to be Wednesday and Thursday. Isolated
high-based showers remain possible over the southern mountains and
south-central valleys this afternoon from what moisture is left from
the drying airmass. These are unlikely to produce much in the way of
measurable rain, much less wetting rain. Southwest winds will
gradually increase Wednesday into Thursday ahead of the next
approaching storm system, strongest across southern Utah. Combined
with the dry airmass, these winds will result in marginally critical
fire weather conditions Wednesday and localized, low-end critical
fire weather conditions on Thursday. The next storm system will then
eject across southern and eastern Utah Friday. This will bring with
it increasing moisture and cooler temperatures heading into the
weekend.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Excessive Heat Warning from 11 AM Wednesday to 10 PM MDT
     Thursday for UTZ131.

WY...None.
&&

$$

Cheng/Cunningham

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