258
FXUS65 KSLC 281118
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
518 AM MDT Mon Sep 28 2026

.KEY MESSAGES...

- A moderate risk (level 3/4) for excessive rainfall has been
  issued for southern Utah today. A slight risk (level 2/4) for
  excessive rainfall is in effect for the remainder of southern
  and eastern Utah today.

- A slight risk (level 2/4) for excessive rainfall is in effect
  for southern Utah Tuesday.

- A Flood Watch for flash flooding has been issued for portions
  of central and southern Utah through Tuesday morning, with far
  southern Utah in effect through Tuesday night.

&&

.DISCUSSION, Issued 1039 PM MDT Sun Sep 27 2026...
An upper trough continues to deepen of the
California coast this evening, with Utah under a southwesterly
flow aloft. Moisture has increased today, having been drawn up
from what is now post-tropical cyclone Odalys, with PWATs ranging
from around 0.6 inches across northern Utah to close to inch
across the southwest. Meanwhile, hurricane Polo continues to
slowly approach the Baja coast. This hurricane will contribute
additional moisture which will continue spread north tonight
through Monday. This moisture will interact with the upstream
trough, which will evolve into a closed low across central
California Monday before tracking into Arizona Tuesday, to produce
widespread and locally heavy precipitation, especially across
southern, central and eastern Utah. An area of diffluent flow will
be maximized across southern and eastern Utah on Monday.

Models continue to show substantial precipitation amounts. The
latest NBM has a 75-95% chance of 0.5 inches or greater across
southern through east-central Utah for the Monday through Tuesday
timeframe, with a 70-80% chance of 1 inch or greater across much
of the southern quarter of Utah. Amounts decrease farther north,
but the Wasatch Front is still likely to see at least 0.1 inches.
Heavy rain will bring the potential for flooding/flash flooding,
and a Flood Watch is in effect for the southern and central Utah
mountains and southern through east-central valleys from 12z
Monday through 12z Tuesday. There remains a Moderate Risk for
Excessive Rainfall across southern Utah Monday, with a Slight Risk
extending through central and eastern Utah. On Tuesday, there is
a Slight Risk across southern Utah.

There are still some nuances to where the greatest threat for any
significant flash flooding will be. On Monday, while the plume of
deeper moisture will extend across southeast Utah, cloud cover
may limit instability there resulting in potentially more
stratiform rain with just some embedded convective elements.
Greater instability is expected across southwest Utah, where
stronger convection may result in higher rain rates more conducive
to flash flooding, but precipitation coverage could be more
scattered. Lingering moisture on Tuesday will maintain an elevated
flood threat, but with the track of the low across
central/southern Arizona, there is some question regarding how
much dynamics is available to aid in the development of
precipitation. Some models are now a bit less enthusiastic with
the coverage of precipitation by Tuesday afternoon.

The storm system will exit the area on Wednesday, with high
pressure building in behind it. Cooler temperature on Monday and
Tuesday will start to gradually rebound mid to late week. Drier
and more stable conditions are expected through the end of the
week and potentially through the weekend.



&&

.AVIATION...

KSLC...Showers and occasional thunderstorms will continue to
impact the SLC terminal through at least 06-08Z tonight. The best
chance for thunderstorms will be between 18-23Z. Otherwise, gusty
southerly winds will continue through the day, with a 30% chance
of a switch to northwest winds between 02-07Z tonight.

REST OF UTAH AND SOUTHWEST WYOMING...Widespread showers and
thunderstorms will impact the majority of terminal through at
least 00-03Z this evening. Heavier showers and thunderstorms will
bring MVFR to IFR conditions.

&&

.FIRE WEATHER, Issued 405 AM MDT Mon Sep 28 2026...
Deep tropical moisture will combine with a strong
upper level system moving across the Desert Southwest to bring
widespread wetting rains to the region today. An elevated flash
flooding threat will impact much of central and southern Utah.
While drier air will begin to build into the area Tuesday across
western and northern Utah, the flash flood threat will continue
across southern Utah into Tuesday evening.

High pressure will build into the region Wednesday, bringing a
warming and drying trend to through at least the weekend.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Flood Watch through late tonight for UTZ113-115>122-125>127.

     Flood Watch through Tuesday evening for UTZ123-124-128>131.

WY...None.
&&

$$

Kruse/Cheng

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