978
FXUS65 KSLC 012142
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
342 PM MDT Tue Jul 1 2025

.SYNOPSIS...Expect an increasing threat of thunderstorms through
Thursday, and potentially Friday across northern Utah. Drier air
will likely begin to impact the region Friday into the weekend.

&&

.DISCUSSION...Key points:
* Thunderstorms will continue to trend less dry as additional
  monsoonal moisture moves into the region, with the initial dry
  microburst threat trending towards more of a localized flash
  flood threat.
* Southern Utah will trend drier by Friday, with increasing
  southwesterly winds and near-critical relative humidity.
* Uncertainty remains with the extent of thunderstorms across
  northern Utah on Friday.

Scattered thunderstorms are ongoing across mainly Utah`s mountains
and areas near the UT-NV border as of mid Tuesday afternoon.
Gusts to around 40-50 mph have been observed, with even a few
gusts approaching 60 mph. This wind threat will continue through
the evening, highest across the West Desert where the environment
is most favorable for stronger dry microbursts.

A closed low currently located just south of the Bay Area will
gradually inch closer, allowing additional monsoonal moisture to
flow into the region from the south. Thunderstorm coverage will
thus increase heading into Wednesday, with a higher flash flood
threat compared to today. However, there are a couple of factors
that may limit the spatial coverage of this flash flood threat.
Cloud cover may inhibit instability, and low-level dry air may
reduce precipitation efficiency. Still, with any training and/or
favorable storm motions, the threat is still there. High-res
guidance even suggests some elevated outflow along a cluster of
storms tomorrow afternoon over southern Utah. The West Desert on
the other hand, will be more on the fringe of this moisture, and
thus may have more of an outflow wind threat...just less than
today.

The aforementioned closed low will weaken as it makes its way
across our area late Wednesday into Thursday, producing nocturnal
showers and perhaps isolated thunderstorm as it does so. By
Thursday afternoon, with developing instability and better shear
associated with this upper-level feature, any showers that
develop could be capable of producing gusty winds and small hail,
especially as drier air starts to filter into the area. The flash
flood threat will likely be lower than Wednesday across all but
eastern Utah as PW begins to decline.

Models are starting hone in on a solution for Friday. While there
is still a question of how far south showers and thunderstorms may
reach, it`s looking more likely for at least northwestern Utah to
see thunderstorms and potentially a severe threat given increased
shear as a shortwave trough grazes our area; a brief look at the
ECMWF Extreme Forecast Index suggests an elevated
instability/shear parameter across northwestern Utah. In contrast,
southern Utah will experience warmer temperatures and increasing
dry, southwesterly winds on Friday and into the weekend.

&&

.AVIATION...KSLC...Predominantly VFR conditions are expected to
continue throughout the TAF period. High-based thunderstorms capable
of producing gusty and erratic outflow winds as well as lightning
will continue to be possible through 02-03Z. There is a 30% chance
for storms to impact the terminal through 00Z, with potential to
produce outflow gusts between 30-40 kts. These probabilities drop
slightly to about 20% between 00Z-02Z. Otherwise, most likely
scenario is for SSE drainage winds to become reestablished around
02Z. Latest guidance suggests and early wind shift to the NW around
18Z Wed, with another ~30% chance for thunderstorms with gusty,
erratic winds between ~21Z-01Z.

.REST OF UTAH AND SOUTHWEST WYOMING...A monsoonal moisture push into
the region will lead to more widespread thunderstorm coverage today.
While there is a low chance of impacts to flight categories with
this activity, a heavier thunderstorm core could briefly reduce
visibility, along with any blowing dust associated with thunderstorm
outflow. Storms that develop this afternoon will be capable of
producing gusty and erratic outflow winds between 30-40 kts if they
move into the vicinity of any regional terminals. Otherwise, VFR
conditions to prevail with increasing mid-to-high level clouds
through the remainder of the TAF period. Only exception remains KBCE
where periods of MVFR/IFR conditions are possible through roughly
15z from VIS restrictions due to smoke from nearby wildfires.
Additional shower and thunderstorm activity is likely Wednesday,
developing first over high terrain areas between 17Z-18Z. The
coverage and intensity of rainfall in shower/thunderstorm cores will
be slightly greater on Wednesday when compared to Tuesday.

&&

.FIRE WEATHER...Afternoon thunderstorms will gradually diminish
through the evening, still with a threat of lightning after a dry
period, especially across the central and southern mountains.
Gusty outflow winds up to 40-50 mph are possible statewide through
roughly 1800, though northwestern Utah may still see gusts this
strong through the evening as thunderstorms collapse.

Thunderstorm coverage will increase further heading into Wednesday
and Thursday, with increasing chances for wetting rain across much
of the state, the exception being the West Desert which may still
see more dry microburst winds on Wednesday afternoon. RH will
increase accordingly, with overnight recoveries remaining
excellent through at least Friday.

Friday will be drier across southern Utah, with increasing
southwesterly flow and lower RH approaching Red Flag criteria.
Across northern Utah, thunderstorms may develop once again during
the afternoon with a passing disturbance, though this is a lower
confidence forecast. Warmer and drier weather is expected heading
into the weekend.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Heat Advisory until midnight MDT tonight for UTZ102>106.

     Red Flag Warning until 9 PM MDT this evening for UTZ488-493-
     495>497.

WY...None.
&&

$$

Cunningham/ADeSmet

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