181
FXUS65 KSLC 160444
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
1044 PM MDT Tue Sep 15 2026

.KEY MESSAGES...

- Deep moisture will continue to bring an elevated threat of
  flooding to portions of southern and eastern Utah through at
  least Friday.

- A Flood Watch for flash flooding has been issued from late
  tonight through Thursday morning for portions of southern and
  eastern Utah including Zion National Park, Capitol Reef National
  Park, Glen Canyon Recreation Area, the greater Grand Staircase-
  Escalante National Monument area, and the lower Paria including
  Buckskin Gulch and Paria Canyon north of the Arizona border.

- A marginal risk for severe thunderstorms (level 1/5) continues
  for Wednesday morning into Wednesday afternoon across portions
  of northern Utah.

- A marginal risk for excessive rainfall (level 1/4) continues
  for Thursday and Friday across southern and eastern Utah.

&&

.DISCUSSION...An upper level low will continue to shift down the
Pacific Coast through later Thursday into Friday and then
gradually eject across the Great Basin through Saturday.
Diffluent southwest flow will remain in place, with modest
moisture transport through at least later Thursday. Embedded in
this southwest flow will be a multitude of weak shortwave
troughs or remnant MCVs. This, combined with PWATs in the 96-99th
percentile, and broad ascent will support periods of convection
with very heavy rainfall, especially through Friday morning.

Earlier thunderstorms, with occasional embedded supercells
produced rainfall rates as high as 0.50 inches in 20 minutes,
causing multiple flash floods in the Wahweap, lower Paria
drainages as well as various slot canyons in the San Rafael Swell
including Little Wildhorse north of Goblin Valley State Park.

Current model trends indicate another subtle shortwave ejecting
across northern Arizona/southern Nevada and southwest Utah will
aid in the development of convection overnight through about 6 AM
this morning across lower Washington County, Iron County and
western Kane and Garfield Counties. Rainfall rates in excess of
0.25 inches an hour will be possible with this convection, with
around a 10% chance of rainfall rates in excess of 0.50 inches per
hour. A Flood Watch for flash flooding begins at midnight tonight
and continues through Thursday morning for Zion National Park and
points east. No changes have been made to the going Watch.

The Storm Prediction Center has outlooked portions of northern
Utah for a marginal risk for severe thunderstorms, particularly
for Wednesday morning into early Wednesday afternoon. A few strong
thunderstorms will be possible along the periphery of the deeper
moisture in this area.

Afternoon convection will kick off across the region, with a
multitude of CAMS showing very widespread heavy rain across most
of southern Utah after about 00Z. This may require the expansion
of the Flood Watch into lower Washington, Iron and Beaver Counties
for late Wednesday night into Thursday afternoon. Something to
monitor for future adjustments if CAMS remain consistent.

It is not recommended to have plans into slot canyons, normally
dry washes, and other areas prone to flash flooding over the next
several days. Nearly all National Park and Rec areas are currently
at Probable for the next several days in the flash flood potential
product.

&&

.AVIATION...

KSLC...There is a 30% chance for showers and thunderstorms at the
terminal accompanied by gusty winds in excess of 30 kts and
occasional lightning during the 08-12Z timeframe. Otherwise winds
will remain predominantly southerly through the TAF period, with
gusts in excess of 20 kts developing by 12z and persisting through
the day. Additional showers and thunderstorms are possible Wednesday
afternoon and evening, however the chance of a shower or
thunderstorm impacting the terminal is less than 30%.

REST OF UTAH AND SOUTHWEST WYOMING...Scattered showers and
thunderstorms will develop overnight and impact terminals south of
I-80 during the 08-14Z timeframe. After 14Z, the chance for showers
and thunderstorms impacting northern terminals will fall below 30%
through the remainder of the period as VFR conditions and south
winds prevail. Across southern terminals, the chance for showers and
thunderstorms will increase to 30% again this afternoon, with
widespread showers and thunderstorms beginning 02Z Thursday.

&&

.FIRE WEATHER...An ongoing moisture surge will bring an increased
threat of showers and thunderstorms across eastern and southern
Utah through at least Friday. For locations west of I-15,
humidities will increase above critical levels by Wednesday,
however gusts to 30 mph will continue through Thursday.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Flood Watch from Wednesday afternoon through late Wednesday
     night for UTZ121-129.

     Flood Watch through late Wednesday night for UTZ124-128-130-131.

WY...None.
&&

$$

Kruse/Seaman

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