570
FXUS65 KSLC 301025
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
425 AM MDT Mon Jun 30 2025

.SYNOPSIS...Hot temperatures will continue through Tuesday.
As mid-level moisture increases Tuesday into Wednesday, slightly
cooler temperatures and increasing coverage of thunderstorms is
expected. Expect a break in the threat of thunderstorms by Friday.

&&

.DISCUSSION...Early morning satellite and upper air analysis
indicates a broad ridge centered near the 4-Corners region with an
upper level low off the California coast. A trough is currently
located near the Gulf of Alaska. The ITCZ remains quite active
with Tropical Storm Flossie off the southwestern Mexican coast and
the remnants of Barry over northeastern Mexico. Precipitable water
values remain near about 0.40-0.60" across the region.

The previously mentioned upper level low will continue to slowly
shift eastward today. HREF 25th to 75th percentile SBCAPE values
look to average between 150-400 J/kg across portions of northern
and eastern Utah. Deep layer shear will average around 15-20kts.
With the primary forcing mechanism related to the higher terrain,
expect isolated convection across the Wasatch spine and east into
eastern Utah this afternoon and evening. Given inverted-v type
profiles, localized microbursts are possible near any high-based
convection.

Very hot temperatures are expected this afternoon, with highs
nearing the mid to upper 90s across the northern valleys, just shy
of 110 across the St. George area.

By Tuesday afternoon, the upper level low will have made little
progress further east. However, this will help to induce southerly
flow to begin to shift monsoonal moisture further north.
Precipitable water values will increase to around 0.70-0.90" (HREF
mean). This will help to increase instability sufficiently for
more widespread convection, with two main genesis locations...the
higher terrain and the typical eastern Nevada convection area.
Given the moisture increase is mostly in the mid- levels, expect
the main threat to again be strong, gusty microburst winds.

Tuesday afternoon will be the hottest day of this stretch, with
portions of the Wasatch Front exceeding 100F and St. George
approaching 110F. HeatRisk starts to reach into the major
category for portions of the Wasatch Front and Cache Valley
Tuesday. Day shift may need to consider hoisting heat advisories
for the Wasatch Front and Cache Valley for Tuesday, but will hold
off issuing with this package as it is on the marginal side of
criteria.

By Wednesday, moisture advection will continue, with PWs reaching
to near 1" (around 90-97.5th percentile), especially across
southern Utah. The stubbornly slow upper level low will now be
near the southern Sierras. With more forcing for convection,
expect convection to increase in coverage over Tuesday. Storm
motions will be on the slower side and may support a transition to
a flash flood threat by Wednesday afternoon. Don`t expect
widespread flash flooding, however, but those with plans in slot
canyons, normally dry washes, slickrock areas, etc should continue
to monitor the forecast as isolated flash flooding especially for
those areas is increasing in likelihood.

By Thursday, the previously mentioned Gulf of Alaska trough will
combine with the upper level low and finally push this system out
of the region. Another day of relatively widespread convection is
expected...with the threat of isolated flash flooding continuing
across the south. Deep layer shear may be sufficient across the
north for more organized convection.

&&

.AVIATION...KSLC...Light and variable winds are expected to
remain in place this morning prior to becoming a prevailing
northwest wind above 7kts between 18-19z. Expecting more cumulus
buildups over adjacent terrain during peak heating today vs. the
last several days, but not expecting any direct impacts to the
terminal.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will prevail
across the airspace outside of areas downstream of large
wildfires in the south. For those isolated areas (e.g. BCE) early
morning stability will again allow for smoke to drive localized
IFR conditions through ~15z. A slight increase of moisture will
promote high based showers and isolated storms over most terrain
areas during the peak heating hours this afternoon/eve. Isolated
gusty outflow winds up to 40mph remain the primary threat
associated with any more organized development.

&&

.FIRE WEATHER...With the 4-corners high in place today, expect
hot and dry conditions with isolated thunderstorms along the
higher terrain. Very low humidities are expected this afternoon
and evening, with poor recoveries overnight tonight. As moisture
begins to increase Tuesday into Wednesday, more widespread
convection is expected. Given this will be the first lightning
after an extended dry period, there is increasing concern of
enhanced fire weather conditions. Daytime humidities will remain
in the 8-15 percent range for most valley locations Tuesday, with
improved overnight recoveries Tuesday night. As the moisture
deepens both daytime and overnight humidities will continue to
increase Wednesday into Thursday. As a disturbance crosses the
area Thursday, additional thunderstorms are likely.

Another disturbance approaching Friday may bring a round of gusty
southwest winds along with lower humidities.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

Kruse/Merrill

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