497
FXUS65 KSLC 230930
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
330 AM MDT Sun Jun 23 2024

.SYNOPSIS...Dry and hot conditions will continue across northern
Utah through Monday...with the threat of showers and
thunderstorms across central and southern Utah. By Wednesday,
showers and thunderstorms can be expected statewide.

&&

.SHORT TERM (Through 12Z Tuesday)...With the upper level ridge
centered over the southern Plains/southern Rockies over the next
several days and the continued active northern stream, it`ll be a
bit of rinse and repeat each day. Looking at surface dewpoints
across southern Utah, lower terrain areas continue to see elevated
dewpoints in the 40s to 50s. No surprise that precipitable water
plots show values between 0.75-1.25" across southern Utah.

Sufficient instability will exist across southern and eastern Utah
today for more widespread convection than Saturday. With slower
storm motions, expect the threat of flash flooding will be
elevated today, especially from Zion to the Buckskin/Paria Narrows
area and the Capitol Reef area. With less deep layer shear, the
threat of severe convection is lower than the last few days.

Meanwhile, across northern Utah, an increasing dry and hot airmass
will be in place. Expect temperatures in the upper 90s to low 100s
across the Wasatch Front and Cache Valley. Added a heat advisory
for the Cache Valley with this package and kept the remainder of
the heat headlines in place.

For Monday, PWs remain elevated across much of southern and
eastern Utah with continued slow storm motions. Expect another
round of convection with the main threat continuing to be flash
flooding. Convective coverage may be a bit less than Sunday.
Temperatures will be a bit cooler across northern Utah Monday
afternoon and evening...and thus...currently do not have any heat
products out.

Main messages for the short term forecast is be mindful of the
very hot temperatures and avoid activities during peak heating
across northern Utah. For southern Utah, consider avoiding slot
canyons, dry washes and other flood prone areas, especially for
locations near the Utah/Arizona border.

.LONG TERM (After 12Z Tuesday)...Tuesday looks to be the hottest
day of the long term period as strong ridging across the south
central to southwest CONUS continues to exert influence upon the
local forecast region. Afternoon highs along the Wasatch Front
once again generally range from the low 90s to a little over 100,
and for Lower Washington County a bit above 105 of so. Areawide,
these temperatures are around 5 to 15 degrees above climatological
normal for late June. Compounded with very mild overnight lows,
HeatRisk once again highlights Tuesday as a potential candidate
for heat related headlines (primarily across northern Utah).
However, given it looks somewhat borderline as forecast, and
there`s a non-zero chance clouds could increase a bit ahead of
schedule and keep temps a little better in check, will hold off on
any issuance with this forecast package. In any case, as has been
mentioned in several previous discussions, it will be hot out
there regardless. Heat related safety should still be kept in
mind, especially for those working or recreating outdoors. Stay
hydrated and take frequent breaks if at all possible, and ideally
wear light and loose fitting clothing. Aside from the heat, will
still see sufficient lingering moisture in combination with
afternoon heating to trigger isolated to scattered afternoon
convection. Largely expect activity to fire off terrain and drift
into adjacent valley locations, with highest coverage across
southern Utah. While not anticipated to be overly widespread,
those planning any recreation in rain sensitive areas should
remain weather aware.

Wednesday will see the first semblance of a shift in the ongoing
pattern, as a trough deepening into the PacNW will help flatten
and shift the ridge a bit eastward. Combination of the flattened
and slightly displaced ridge along with increasing mid level
moisture and associated cloud cover will help afternoon high
temperatures begin to trend downward. Additionally, will see some
increasing (but still fairly weak) PVA in the enhanced
southwesterly flow between the deepening trough and ridge, so will
see an expansion of isolated to scattered precipitation chances
across the majority of the forecast region.

The aforementioned Pacific trough continues to deepen a bit as it
shifts inland Thursday and Friday. While guidance continues to
carry some differences in just how deep and how quickly the trough
advances eastward, there remains fairly good consensus that it
will push a cold frontal boundary southward towards and likely
into the forecast region. So far, most likely timing of this
feature is later Thursday on into early Friday, with elevated
precipitation chances maintained until after frontal passage and
subsequent advection of some drier post-frontal air. This will
result in a continued downward trend in temperatures, with Friday
currently looking like the coolest day of the forecast period,
with afternoon high temps generally near to even a bit below
climatological normal. That said, overall deepness of the trough
will impact how far south the front progresses and just how cool
things get, and there`s still a decent amount of spread in
guidance. For example, at KSLC for Friday the NBM 25th percentile
high temperature (stronger trough scenario) is 84 degrees, and the
NBM 75th percentile high temperature (weaker trough scenario) is
95 degrees. In any case, it looks like the trough will at least
give the area a reprieve from some of the more excessive heat from
earlier in the week.

Moving into the weekend, guidance currently leans in favor of a
gradual restrengthening of ridging, and thus yields a warming
trend back to above normal. Most guidance also currently seems to
suggest limited moisture availability, so with the subsident
effect of the building ridge, precipitation chances remain limited
with this forecast package.

&&

.AVIATION...KSLC...Enhanced southerly winds expected to see a
somewhat delayed diurnal shift, with guidance suggesting a switch
to northwest between ~19Z-22Z Sunday. There is a low chance (less
than 20%) that convection further south of the area could push
gusty outflow winds towards the terminal late afternoon into the
evening. Convection is not currently anticipated directly near the
terminal, however. Winds then favored to switch back southerly
~03Z-05Z. Only limited mid level cloud cover anticipated through
the period.

.REST OF UTAH AND SOUTHWEST WYOMING...Generally dry weather is
anticipated at northern Utah terminals Sunday, with fairly limited
mid level cloud cover. Depending on how far north convection
develops across Utah, there will be a low chance (less than 20%)
gusty outflow winds could push northward towards some of the
northern terminals. At southern terminals, a bit more moisture in
combination with daytime heating will yield isolated to scattered
convection. These terminals will see better odds of gusty outflow
winds in addition to lightning and briefly reduced conditions with
anything that drifts over a terminal. Convection wanes moving
later into the evening, with winds following a more typical
diurnal pattern overnight.

&&

.FIRE WEATHER...With a lack of cold front to scour out the
modified tropical moisture in place over the last few days across
portions of southern Utah, the threat of showers and thunderstorms
will continue Sunday into Monday. This will ease minimum
humidities a bit higher averaging around 20-30% for lower terrain
areas of southern Utah, 25-35% for higher terrain areas. Meanwhile
across northern Utah, humidities will continue to be quite low,
with west central and northwest Utah seeing minimum humidities as
low as the single digits. The threat of convection will lower
Tuesday.

By Wednesday, an upper level system crossing into the Pacific
Northwest will bring a nearly statewide threat of convection, with
an improvement in humidities. A dry slot across western Utah may
bring gusty winds and low humidities Thursday, potentially
bringing critical fire weather conditions to locations with
receptive fuels across western Utah. As a cold front crosses the
state Friday, more widespread critical fire weather conditions are
possible across much of southern Utah.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Excessive Heat Warning from 9 AM this morning to 9 PM MDT this
     evening for UTZ101>105.

     Heat Advisory from 9 AM this morning to 9 PM MDT this evening
     for UTZ106-107-116-118-119.

WY...None.
&&

$$

Kruse/Warthen

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http://weather.gov/saltlakecity