869
FXUS65 KSLC 061041
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
441 AM MDT Sat Jul 6 2024

.SYNOPSIS...High pressure will gradually shift eastward over the
next seven days, bringing increasingly warm temperatures first to
southern Utah this weekend, and then northern and central Utah
Wednesday.

&&

.SHORT TERM (Through 12Z/6AM Monday)...A mid level ridge centered
across California this morning is inducing a deep layer
northwesterly flow downstream across the forecast area. A
shortwave trough currently digging through the northern Rockies
will brush by the forecast area as it digs into the central
Rockies later today through Sunday. Enhanced northwesterly winds
will be the primary impact on the forecast area, which combined
with a very dry airmass will result in critical fire weather
conditions across areas east of I-15 where fuels are critically
dry. Otherwise with a re-enforcing shot of "cool" air temperatures
will remain near climo across northern and central Utah. The same
cannot be said for lower elevations of southern Utah, where max
temps will approach 110F near St George this afternoon and Zion
Canyon this afternoon, then trend 2-3 degrees warmer Sunday when
an Excessive Heat Warning goes into effect.

.LONG TERM (After 12Z/6AM Monday)...Long term portion of the
forecast will continue to be punctuated by potentially dangerous,
excessive and prolonged heat. Global deterministic and ensemble
systems remain in very good agreement regarding the strength,
positioning and progression of the ridge through the period, the
feature responsible for the excessive heat. On Monday, model
consensus places the center of the ridge near Death Valley, CA
migrating to over southern Nevada on Tuesday before finally
propagating to near/over Utah by Wednesday. The ridge is then
expected to weaken slightly while remaining overhead through Friday,
with a subset of the ensemble solution space keeping the ridge in
place through the weekend. Given the anomalous nature of the ridge
relative to climatology and its slow progression, surface
temperatures will challenge record values for several days, adding
to the cumulative effects of the hazards associated with this
heatwave. Overnight cooling will be limited as well. The bottom line
is that the cumulative effects of this excessive heat will place
significant stress on people and pets, particularly those without
adequate cooling and those that spend significant time outdoors,
adding to the vulnerability. Avoid strenuous outdoor activities
during the hottest time of the day, drink plenty of water and limit
exposure to the sun.

Temperatures are likely to reach or exceed 110F in St. George from
Sunday through Friday, when probabilities for reaching or exceeding
110F are above the 75th percentile. Low temperatures during this
period will range from the upper 70s to the mid 80s. For SLC,
temperatures are likely to reach or exceed 100F from Tuesday-Sunday,
when probabilities for reaching this threshold are at least 75%.
Even typically cool high elevation valleys such as the Bear River
and Evanston will experience several days with highs in the low 90s.
Low temperatures during the peak of the heatwave will range from the
mid-70s to near 80F in SLC. Thus, this heatwave will rival past
heatwaves both in terms of duration and intensity. EFI values remain
elevated and standardized anomaly 700mb temperatures reach or exceed
those in the model climate, especially over SW Utah early in the
week.

We continue to monitor for the potential for some increase in
moisture and relief from the heat. Ensemble consensus is coming into
better agreement regarding these prospects, with the first signs of
an increase in total column moisture reaching SW Utah by Saturday
before overspreading the remainder of Utah and SW Wyoming by Monday.
A cross-section of the atmosphere reveals that much of the increase
in moisture will be relegated to the mid-levels, although at least
some modest increase in low-level moisture is forecast, especially
over SW Utah by next weekend. First signs of the moisture increase
will be manifest in the form of mid/high level clouds, with the
first appearances of isolated terrain-based thunderstorms arriving
by Saturday across southern Utah. Initially, main threat with this
activity will be dry lightning, and this is concerning following an
extended hot, dry stretch as the lightning will add to the potential
for new wildfire starts.

&&

.AVIATION....AVIATION...KSLC...Stagnant conditions continue with
little day to day change. Transition to northwest winds expected
between 16-18Z, with afternoon gustiness once again after 20Z. Winds
then transition back to southeast between 04Z and 06Z this evening,
with occasional periods of variable winds around transition periods
and overnight.

.REST OF UTAH AND SOUTHWEST WYOMING...Broad northwest flow will
once again be in place today as the region resides downstream of a
strong ridge. This will once again create afternoon gustiness in
wind-prone locations with winds subsiding around sunset. VFR
conditions will continue aside from areas downwind of fires, which
may see VIS reductions due to smoke.

&&

.FIRE WEATHER...A very dry airmass in place across the region
will remain in place through the weekend, resulting in very low RH
and poor overnight recoveries. High pressure centered over
California will maintain northwest flow aloft across the state,
and a weak weather system brushing by the area will enhance these
winds across portions of central and eastern Utah today, and again
Sunday spreading into south central Utah. This will result in
critical fire weather conditions mainly east of I-15 anywhere
fuels are sufficiently dry.

The high pressure over California will shift east early next
week, becoming centered across Utah for much of the week. This
will bring hot and dry conditions across the region, with
temperatures challenging daily records through at least midweek,
while RH remains very low and overnight recovery generally poor.
With the high in place, winds will become light and generally
terrain driven for much of next week. There is a slight chance
high based moisture begins to spread into the region late in the
week, which could result in a threat for dry thunderstorms toward
the end of the week.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Red Flag Warning from noon today to 9 PM MDT Sunday for UTZ482-
     489-493-496.

     Excessive Heat Warning from 9 AM Sunday to 9 PM MDT Wednesday
     for UTZ123-124-131.

     Red Flag Warning from noon to 9 PM MDT Sunday for UTZ494-498.

WY...None.
&&

$$

Seaman/ADeSmet

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