321
FXUS65 KSLC 132209
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
409 PM MDT Thu Jun 13 2024

.SYNOPSIS...Anomalous heat persists today, with triple digit
readings along portions of the Wasatch Front for the first time
this year. A mid to upper level low will move through late today
through Friday, bringing a slight cooldown and some low end
precipitation chances. A stronger storm system looks to affect the
area early next week, bringing gusty winds and much cooler
temperatures.

&&

.SHORT TERM (Through 12z/6AM Saturday)...
The main talking point in the short term is the heat across Utah
that peaks today. Readings at the Salt Lake Airport have just
touched the century mark this afternoon, making it the first of
the year, and roughly about 3 weeks ahead of the average first
100. Heat advisories remain in place across the Wasatch Front and
over into Wendover. An excessive heat warning remains in place
for the Glen Canyon NRA / Lake Powell area where high temperatures
continue into low to mid 100s again today, resulting accumulated
heat stress over the last couple days.

The ridge responsible for the heat wave will continue to weaken
and shift eastward away from the forecast area tonight into Friday
while a filling low pressure system over southern California this
afternoon continues to weaken as it tracks toward the Four Corners
through Friday afternoon. Ahead of this low, mid-level moisture is
already increasing into southern Utah, and this trend will
continue from south to north across mainly the eastern half of the
state tonight, while overall cloud cover will expand across much
of Utah overnight. Simultaneously, winds will continue to
increase from south to north as the pressure gradient tightens
ahead of the low pressure system. This will result in an
anomalously warm night night tonight as the combination of
elevated winds maintain a mixed boundary layer and clouds limit
radiational cooling. Thus warm overnight lows will continue to
contribute some of the heat stress, particularly across northern
Utah, limiting cooling relief tonight for those without
air conditioning .

By Friday, temperatures will be moderated by the low pressure
system moving in and mid/high level cloud cover overspreading a
good portion of the state, especially across eastern Utah.
Isolated showers are possible on Friday, mainly across eastern
Utah, but little to no appreciable rain is expected.

.LONG TERM (After 12z/6AM Saturday), Issued 441 AM MDT...
Model guidance continues to trend cooler with the potent cold
front arriving on Monday. Expect a stark transition to spring-like
temperatures, contrasting the near- record heat we have seen this
week.

At the start of the long-term, a strong closed low will likely be
positioned over WA and southern BC. As it inches closer over the
weekend, expect a gradual cooling trend on Saturday and Sunday with
highs returning to around normal by Sunday. With a strengthening
pressure gradient as the trough begins to push southward, gusty
southwesterly winds are expected to develop Sunday afternoon. The
highest winds will occur mainly south of I-70, with current ensemble
mean gusts reaching 30-40 mph. Winds are likely to peak Monday
afternoon ahead of the cold front, with ensemble means exceeding 50
mph in portions of southern UT.

As the upper-level trough swings across the northern Great Basin and
into the Intermountain West, its cold front will push through our
area on Monday. The air mass will likely be too dry for much
precipitation, aside from a few isolated showers near the UT-ID
border just behind the frontal passage.

Uncertainties in the upper-level pattern still remain, with
disagreement of the timing of the cold front and extent of cooler
temperatures. Models have overall trended a bit later with the cold
front, now looking more likely for late Monday into Tuesday.
Eighteen percent of ensemble members suggest a much milder cooldown,
with 700-mb temperatures dipping down to +6C. On the other end of
the spectrum, another 21% of members favor a more aggressive
cooldown with 700-mb temperatures reaching -5C. The remainder are
somewhere in the middle, with a mean around -2C, which is still
below the climatological 10th percentile for mid-June. At the
surface, this translates to highs around 70F across the Wasatch
Front and near 90F in far southern UT...though keep in mind that
there is still a 10 degree spread in the NBM 25th-75th percentiles.

&&

.AVIATION...KSLC...Weak low pressure lifting through the region this
evening will continue to drive strong southerly winds aloft... with
that, expecting continued impulses of southerly winds and an early
decay (~02Z) of the northerlies driven by today`s lake breeze. High
and thin clouds move in overnight, with another morning of enhanced
southerly flow for Friday. This has the potential to again delay the
shift to northerly flow Friday afternoon with a chaotic transition
period.

.REST OF UTAH AND SOUTHWEST WYOMING...Southern Utah will continue to
see gusty winds in the vicinity of high-based showers or virga.
Southerly winds will die down some overnight, with cloud cover
spreading over the region, generally above 15kft, clearing again
through the morning hours Friday. Winds will be subdued some midday
as the center of low pressure moves in overhead, but any shower
activity in the afternoon could again produce localized gusty winds -
 particularly along the UT/NV border.

&&

.FIRE WEATHER...
High pressure continues to decay east of Utah as a weakening low
pressure system fills moving from southern California this
afternoon toward the Four Corners Friday afternoon. Hot, dry
conditions continue across the state today with increasing winds
across southern Utah as the low pressure system approaches. This
is resulting in critical fire weather conditions across southern
Utah this afternoon where Telegraph Flat is already at 6% RH with
wind gusts to 37 mph.

Moisture will quickly increase from south to north, mainly across
eastern Utah into Friday as the low pressure system continues to
approach. This will increase RH values slightly into Friday
afternoon, increase cloud cover overnight, with some partial
clearing later Friday afternoon, and result in some isolated rain
showers, with very low (<10%) chance of wetting rain, mainly over
eastern Utah.

This weekend into early next week an anomalously deep trough for
this time of year will develop over the Pacific Northwest. There
is high confidence that this will develop critical fire weather
conditions given the very dry and breezy southwesterly flow ahead
of this trough, mainly across southern Utah. With zones 497 and
498 fuels recently turned critical, we`ve issued a Fire Weather
Watch. Winds by Sunday, but especially Monday there is about a 50%
chance of seeing gusts exceeding 45 mph, along with high
confidence in widespread sub 10% RH values across these zones (as
low as 5%). Meanwhile northern Utah will see some
cooling/moistening early next week as strong cold front will
eventually push through, likely by Monday afternoon or evening.


&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Heat Advisory until 6 AM MDT Friday for UTZ101-102-104>106.

     Red Flag Warning until 9 PM MDT this evening for UTZ498.

     Fire Weather Watch from Saturday morning through Monday evening
     for UTZ498.

     Excessive Heat Warning until 10 PM MDT this evening for UTZ131.

     Fire Weather Watch from Sunday morning through Monday evening
     for UTZ497.

WY...None.
&&

$$

SHORT TERM...Church
LONG TERM...Cunningham
AVIATION...Wessler
FIRE WEATHER...Church

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