259
FXUS65 KSLC 020937
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
337 AM MDT Wed Jul 2 2025

.SYNOPSIS...A monsoon surge will bring the threat of
thunderstorms to much of the region through Thursday. Drier air
will work into the area for Friday and continue into next weekend.

&&

.DISCUSSION...Early morning upper air and satellite analysis
indicates the persistent upper level low is finally shifting
eastward into central California this morning. Precipitable water
values across Utah have increased from near 0.60" 24 hours ago to
0.70-0.80". These values will continue to increase through the
day, reaching around the 90-97th percentile by 00Z Thursday.

The previously mentioned upper level low will be nearing the
southern Sierras by this afternoon. HREF mean SBCAPE values will
be around 500 J/kg or so this afternoon across portions of
southern and eastern Utah, perhaps a bit lower across northern
Utah. While much of eastern and far southern Utah will see deep
shear at or below 10 kts (and thus slow storm motions), more
significant deep layer shear values approaching 25-30kts can be
found near the Nevada border.

In areas with sufficient shear, the two main threats will be heavy
rain and gusty winds. For the remainder of central and southern
Utah, the main threat will be heavy rain and isolated flash
flooding. Expect showers and thunderstorms to develop quickly near
18-20Z across nearly the entire state. The Storm Prediction
Center has flagged western Utah with a marginal risk for severe
thunderstorms this afternoon and evening.

Looking at the max 1-hour precipitation rates across the CAMS
combined with PWs in excess of the 90th percentile, some
thunderstorms may support rainfall rates in excess of 0.50
inches/hour. Given this potential, increased the flash flood
potential for Zion, Snow Canyon and Buckskin Gulch/Paria Canyon to
"Probable" in the Flash Flood Potential product. This is a good
day to plan alternate activities outside of slot canyons, normally
dry washes and slickrock areas. Additionally, the Weather
Prediction Center has added a marginal threat for excessive
rainfall (implying at least a 15% chance of rainfall exceeding
flash flood guidance within 25 miles of a point) across southern
Utah through Thursday morning.

As the upper level low transitions to an open wave and continues
to weaken Thursday, drier air will slowly entrain into the region.
While another round of convection is expected Thursday afternoon
and evening, current expectation is the threat of flash flooding
will be less. That said, HREF 25th to 75th percentile SBCAPE
ranges from 250-1000 J/kg or so Thursday afternoon...combined with
deep layer shear as high as 30-35kts. There is some potential for
more organized convection Thursday afternoon and evening.
Something to keep an eye on.

Guidance has been inconsistent regarding the path of the upstream
trough on the 4th of July...until the last few runs. While areas
Salt Lake City and north have the highest potential for afternoon
showers and thunderstorms, portions of western Utah will
transition to gusty winds and low humidity. There is a 60-70%
chance winds and humidities will reach critical fire weather
conditions Friday afternoon and evening across western Utah.
Please check with local officials regarding firework/fire bans and
restrictions to reduce the threat of wildfire ignitions Friday
afternoon and evening. Did not issue a Fire Weather Watch on this
shift to allow the day shift to more closely coordinate with
relevant partners.

Next weekend into early next week looks to be largely dry with
gradually increasing temperatures as high pressure sets up shop
across the 4-Corners region.

&&

.AVIATION...KSLC...Overall VFR conditions prevail at the terminal
through the TAF period. High-based thunderstorms are expected to
develop once again this afternoon, with a 30% chance to impact the
terminal between 20-00z. These storms will be capable of
producing gusty and erratic outflow winds between 30-40 kts in
addition to lightning. Otherwise, predominant winds remain light
out of the southeast this morning before transitioning to the
northwest around 19z, though winds may become variable between
20-00z as outflows from nearby storms impact the terminal.

.REST OF UTAH AND SOUTHWEST WYOMING...Increasing monsoonal
moisture across the region will yield widespread thunderstorm
coverage this afternoon. Impacts to flight categories for regional
terminals remains less than 30%, but can`t rule out brief CIG/VIS
reductions to MVFR/IFR conditions especially across southern Utah
terminals where better shear and instability may produce heavier
precipitation cores. Otherwise, storms this afternoon will once
again be capable of producing gusty and erratic outflow winds
between 30-40 kts if they move into the vicinity of any regional
terminals.

&&

.FIRE WEATHER...A slow moving upper level low will continue to
shift eastward and gradually weaken through Thursday. Ahead of
this low, monsoonal moisture has shifted northward. While
thunderstorms Wednesday were a mix of wet and dry, thunderstorms
will shift toward a more likely threat of wetting rain and
isolated flash flooding today. This trend will continue through
Thursday before dry air begins to move into the area later
Thursday into Friday. Ahead of yet another upper level system,
critical fire weather conditions due to low humidity and gusty
winds will be possible Friday afternoon and evening across
portions of southern and western Utah where fuels are critical.

High pressure will build into the area for the weekend.

&&

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

$$

Kruse/Whitlam

For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity