812
FXUS65 KSLC 062000
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
200 PM 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)...Utah will continue to sit
on the eastern periphery of a ridge of high pressure the remainder
of the weekend. Warm and dry conditions are forecast to continue
with northwest flow persisting. Afternoon breezes are forecast to
increase once more across eastern Utah under this regime with
winds in the 10 to 20 mph range and gusts exceeding 30 mph.
Temperatures are forecast to be pretty similar tomorrow when
compared to today statewide. Excessive Heat Warnings will go into
effect starting tomorrow for lower Washington County, Zion NP and
Glen Canyon Recreation Areas.

.LONG TERM (After 12Z/6AM Monday), Issued 441 AM MDT...
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...KSLC...The SLC terminal will see VFR conditions through
the evening with mostly clear skies. Northwest winds are expected to
shift to the southeast between 03Z and 05Z.

.REST OF UTAH AND SOUTHWEST WYOMING...Except for areas downwind of
fires, the airspace will see VFR conditions through the evening with
mostly clear skies. With strong northwest flow aloft, some areas
will see breezy conditions continuing through the early evening,
with generally light winds otherwise.

&&

.FIRE WEATHER...An extremely dry airmass will remain in place
over Utah through the next 7-10 days, bringing afternoon relative
humidity values down into the low-to-mid teens to single digits
across a large majority of the area. A shortwave trough is
expected to scrape through the area through the next 24-36 hours,
bringing increasingly strong winds out of a northwesterly
direction. Through the rest of today, the strongest winds will be
confined to the northern half of Utah, combining with critically
dry humidity and fuels to warrant Red Flag Warnings. Overnight
humidity recoveries are expected to be poor across most areas
outside of the northern third of Utah tonight, with values only
recovering to around 15 to 25 percent.

Tomorrow, winds increase in speed and areal coverage across the
southern half of Utah with many more areas reaching critical fire
weather thresholds. As such additional Red Flag Warnings will go
into effect for Fire Weather Zones 497 and 498 starting tomorrow
at 1200. Overnight recoveries will begin to increase by about 10
percent across the northern half of the area, however, the southern
half of Utah will continue to see recoveries around 15-30 percent.

Heading into next week, temperatures will become increasingly hot
as a long duration heatwave begins spreading over Utah. Temperatures
will rise to around 10 to 15 degrees above average for this time of
year for much of the area, with humidity values continuing to bottom out
in the teens to single digits. There is currently a low to medium chance
of moisture building into the region late in the week, which may bring
an initial threat of dry lightning to the southern Utah mountains.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Red Flag Warning until 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 UTZ494-497-498.

WY...None.
&&

$$

NDeSmet/Webber/ADeSmet/Traphagan

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