509
FXUS65 KSLC 302145
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
345 PM 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. Thunderstorms will begin to wind down on Friday.

&&

.DISCUSSION...Key points:
* Above-normal high and low temperatures will result in a
  Moderate/Major HeatRisk on Tuesday for Eastern Box Elder County
  and the Northern Wasatch Front.

* Increasing monsoonal moisture will result in increasing coverage
  of thunderstorms through Thursday, with storms gradually
  trending less dry. A dry microburst threat initially will
  transition into more of a localized flash flood threat by
  Wednesday and/or Thursday.

* Increasing shear by Thursday/Friday may result in more organized
  thunderstorms.

Satellite imagery this afternoon reveals a closed low spinning
just off the coast of California, with developing convection
across portions of Utah as mid-level moisture streams in from the
south. As this low continues to slowly shift eastward, this will
allow additional moisture to filter into the area. Precipitable
water increasing to around 0.70-0.90" by Tuesday will result in
increased instability for more widespread convection, first
starting across the central spine of Utah`s mountains then also
developing along the UT-NV border. Inverted-V soundings with steep
lapse rates suggest the threat of gusty microburst winds, with
the HREF max approaching 40-50 mph in many areas. SPC even has
far northwestern Utah in a Marginal (Level 1 out of 5) risk for
severe wind.

Tuesday afternoon will be the hottest day of this stretch, with
portions of the Wasatch Front approaching 100F and St. George
reaching the upper-100s. Overnight lows will be fairly warm, only
reaching down to around 70F along the Wasatch Front. HeatRisk has
a wide swath of Major (Red) HeatRisk across portions of Eastern
Box Elder County and the Northern Wasatch Front, thus Heat
Advisories have been issued for these areas.

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 on Wednesday. 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...Predominantly VFR conditions are expected to
persist today and tonight with typical evening wind shift around 1-
4Z. Cumulus development to the southeast over the Oquirrhs and
adjacent ranges will send mid-level clouds over the terminal this
afternoon/evening, but otherwise no impacts. Higher thunderstorm
chances are expected tomorrow, bringing a threat of gusty and
erratic winds in the afternoon and evening. The chance of a
thunderstorm directly impacting the terminal or vicinity is
currently less than 30%. Meanwhile, there is uncertainty in
tomorrow`s wind shift; current thinking is south winds will prevail
until erratic outflow winds arrive in the afternoon.

.REST OF UTAH AND SOUTHWEST WYOMING...Increasing moisture will
support greater coverage of thunderstorms tomorrow, particularly
over the higher terrain east of I-15, though these are unlikely to
impact flight categories. Rather, isolated gusty outflow winds of up
to 40-50 mph remain the primary threat. Additionally, isolated
locations in southern Utah (e.g. BCE) will again be impacted by
wildfire smoke. For those areas, early morning stability will again
allow for smoke to drive localized IFR conditions through ~15z.

&&

.FIRE WEATHER...While thunderstorms this afternoon have been more
isolated and limited to higher terrain, increasing moisture each
day will result in higher coverage of thunderstorms through at
least Thursday. Overnight RH recoveries will improve greatly,
especially after tonight. Even tonight, many areas will see
improvement, with the exception being across western valleys and
in lower Washington county, where max RH will still be fairly
poor, around 25-30 percent. Min RH will be a bit slower to
improve through the week.

Given this will be the first lightning after an extended
dry period, there is a heightened threat of dry lightning and fire
weather conditions on Tuesday afternoon. Any thunderstorms that
develop Tuesday afternoon will be capable of producing gusty and
erratic outflow winds up to 40-50 mph. This dry lightning threat
could linger into Wednesday afternoon, though this may feature
more of a mix of wet and dry thunderstorms.

Friday is expected to be much drier than prior days, though
afternoon thunderstorms are still possible. Additionally, another
disturbance approaching Friday may bring a round of gusty
southwesterly winds along with lower humidities.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Heat Advisory from noon Tuesday to midnight MDT Tuesday night
     for UTZ103-104.

     Red Flag Warning from noon to 9 PM MDT Tuesday for UTZ488-493-
     496.

WY...None.
&&

$$

Cunningham/Kruse/Van Cleave

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