160
FXUS65 KSLC 280439
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
1039 PM MDT Sun Sep 27 2026

.KEY MESSAGES...

- Widespread heavy rainfall influenced by a strong upper-level low
  and deep tropical moisture brings a heightened risk for flash
  flooding across central and southern Utah starting Monday
  morning, continuing into Tuesday.

- High pressure quickly moves in mid-week, with dry and mild
  conditions persisting through the weekend.

&&

.DISCUSSION...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...Cloud cover and shower chances gradually increase into Monday
morning, particularly after around 12Z as remnant tropical moisture
overspreads the region ahead of a cold front. Some development of
embedded thunderstorms will also be possible Monday afternoon.
Southerly winds are favored to continue, with occasional gusts
during times of precipitation. Models suggest a switch to a
northerly wind direction around 00Z-05Z Tuesday, though uncertainty
is noted. Precipitation chances then decrease overnight into Tuesday
morning.

REST OF UTAH AND SOUTHWEST WYOMING...Remnant tropical moisture will
continue to overspread the area, increasing shower chances Monday
morning on into the day. During the daytime, some embedded
thunderstorms are also expected to develop. Winds will generally
favor a southerly direction, with gusts (and some potential
variability) possible during times of precipitation, and especially
thunderstorms. A cold front will gradually shift southward, allowing
winds to begin to favor a more northerly direction at northern
terminals Monday night into early Tuesday. VFR conditions are
expected to prevail, with some modest decrease to CIGS/VIS during
periods of higher precipitation intensity.

&&

.FIRE WEATHER, Issued 114 PM MDT Sun Sep 27 2026...
Elevated southerly flow aloft will result in gusty
winds developing across the western half of Utah this afternoon
and evening, with widespread gusts 25-35 mph. RH values remain
above critical values given increasing cloud cover from tropical
moisture beginning to spread into the region aloft, therefore
limiting the overall fire weather risk. This increasing moisture
will also result in scattered showers and thunderstorms developing
late this afternoon and evening mainly along and east of the I-15
corridor, with potential to produce gusty and erratic outflow
winds to 50 mph. Deeper moisture overspreading the region originating
from two tropical systems will interact with increasing
instability from an upper level low moving into the Desert
Southwest beginning early Monday, resulting in widespread heavy
rainfall especially across portions of southern and central Utah
through Tuesday morning. Environmental conditions will be
favorable for widespread wetting rains across these areas, in
addition to widespread flash flooding mainly across southern and
eastern Utah. A lull on Tuesday morning will be followed by
additional showers and thunderstorms across far southern Utah
during the afternoon hours, before drier air quickly cuts off any
additional activity late Tuesday. Drier, more seasonable
conditions will persist through the end of the work week.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Flood Watch from 6 AM MDT Monday through late Monday night for
     UTZ117-120-121-123>131.

WY...None.
&&

$$

PUBLIC...Cheng
AVIATION...Warthen
FIRE WEATHER...Whitlam

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