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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