495
FXUS65 KSLC 061217
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
616 AM MDT Sun Sep 6 2026

.KEY MESSAGES, Issued 1002 PM MDT Sat Sep 5 2026...


- Modestly breezy conditions with gusts around 25-40 mph persist
  through Sunday afternoon, primarily west of the I-15 corridor.

- Flash flooding risk increases Sunday, especially from southwest
  to central Utah as tropical moisture increases. A Flood Watch is
  in effect accordingly.

- Isolated severe storms capable of strong to severe wind gusts
  and small hail will be possible across portions of northwest
  Utah Sunday afternoon.

- Drier conditions return for early next week, with uncertainty
  noted on potential for more unsettled conditions from midweek
  onward.

&&

.DISCUSSION, Issued 1002 PM MDT Sat Sep 5 2026...
Evening water vapor analysis shows a broad trough
extending southward through the PacNW with deep southerly flow
noted locally overhead. While a plume of tropical moisture is
evident lifting northward through the Desert Southwest, most
locations across Utah and southwest Wyoming have remained largely
clear, if not sunny. The southwesterly flow has resulted in some
modestly breezy conditions around the area, but temperatures have
remained seasonably mild for early September.

The moisture plume will continue to advance northward overnight,
beginning to encroach into southern Utah with associated shower
activity closer to sunrise. This moisture will then continue to
overspread the majority of the forecast region as the day
progresses, with PWAT anomalies rising to around 150-200% of
climatological normal. Concurrently, will see flow overhead
increase with an embedded shortwave shifting through, providing
increased synoptic forcing for ascent. While mean instability is
only progged to increase to around 150-300 J/kg in the afternoon,
and will to a degree be predicated on cloud cover and degree of
stratiform rain, anticipate the enhanced synoptic forcing will
allow pockets of embedded thunderstorms to develop. Models suggest
any such activity will have potential for rain rates in the 0.5"
to 1.0" per hour range, and with the deep moisture, would expect
even showers will be capable of fairly efficient rainfall
production. Additionally, continued moisture advection in the
southwesterly flow may help bring redeveloping and/or training
storm activity.

Given the setup, Sunday will see potential for excessive rainfall
and instances of flash flooding. The WPC Excessive Rainfall
Outlook includes southwestern to central Utah within a "Slight
Risk" (level 2 of 4) of excessive rainfall, and the majority of
the remainder of the forecast region in a "Marginal Risk" (level 1
of 4). General model consensus supports the highest focus of
activity from southwest Utah through central Utah, especially
along the high terrain and nearby areas. For now, have maintained
the ongoing Flood Watch for this general area, though a shift in
the plume by even 20 miles or so may necessitate expansion of the
watch area. Will have to monitor trends accordingly. Per usual,
the highest threat will be for typically rain sensitive locations
such as recent burn scars, slot canyons, typically dry washes, and
slickrock areas. Those with recreation plans in such areas should
stay weather aware and consider alternatives.

Aside from the flood threat, models also support potential for
more isolated convection forming on the periphery of this plume,
particularly in portions of northwest Utah. While also dependent
to an extent on the degree of destabilization, the enhanced flow
aloft will result strong deep layer shear in excess of 40 kts or
so. This area will also be nearer a slowly approaching front from
the larger PacNW trough. While conditional, any storms that can
become better organized will have at least some threat of strong
to severe wind gusts and small hail.

Precipitation will gradually diminish overnight moving into
Monday morning as the moisture plume exits and the deep PacNW
trough`s evolution will allow a drier and more zonal flow to
develop. The associated cold front will also progress as far south
as central Utah in vicinity of the I-70 corridor or so, bringing
cooler temperatures behind it. Afternoon highs behind the front
Monday will tend to run around 5-10 degrees below normal, with
temperatures ahead of it near to slightly below normal. The front
will begin to wash out quickly, with temperatures for Tuesday
moderating back upwards nearer to typical levels.

Uncertainty increases from Wednesday onward with models diverging
on the exact pattern evolution. There is support that mid to
upper level ridging will be centered somewhere in the southwest
CONUS, but with varying placements. If centered more atop the Four
Corners region the local area will see better potential for
moisture returning, with decreasing favorability the further to
the west it ends up. Around 30% of ensembles support a more marked
moisture surge and higher precipitation potential, around 30%
have a more muted moisture return and likely more isolated
precipitation potential, and the remaining 40% remain on the drier
side of the envelope.



&&

.AVIATION...

KSLC...Southerly winds will become increasingly gusty after 14/15z
this morning, with peak speeds (G30kts) occurring this afternoon
into this evening. An influx of tropical moisture into northern Utah
will result in gradually increasing cloud cover and lowering CIGS
late morning into the afternoon. ~30% chance exists for showers with
local mountain obscuration after 22/23z lasting through the evening.
A boundary will move through the terminal mid morning Monday,
finally switching winds to northwesterly.

REST OF UTAH AND SOUTHWEST WYOMING...Gusty southerly winds across
the airspace will once again be increasing after roughly ~14z. Wind
gusts in excess of 25 kts are expected to develop through the
afternoon for most regional terminals. An influx of tropical
moisture into the region will result in increasing cloud cover from
southwest to northeast this morning, with lowering CIGS as
widespread rain moves in from the south through the day. The most
widespread precipitation is expected across southwestern and central
portions of the airspace today. Showers and thunderstorms taper off
by early Monday morning.

&&

.FIRE WEATHER, Issued 350 AM MDT Sun Sep 6 2026...
The approach of a low pressure system from the northwest
is just now beginning to tap into monsoonal moisture which is
pooled to the southwest over the lower Colorado River Basin.
Strong southwesterly flow aloft will rapidly spread this moisture
into the area from southwest to northeast today, with increasing
showers and storms accompanying. The focus of precipitation is
expected to initially occur across southwestern Utah shortly after
sunrise, then spread northeast into central Utah by midday. A
boundary associated with the low pressure system will begin to
push into northwestern portions late afternoon through this
evening and will drive another area of showers and storms focused
over fire weather zones 478 and 479.

The boundary will push west to east across the district tonight
through Monday morning ushering in a much drier airmass once
again. This dry airmass will remain in place through at least
midweek with temperatures trending from ~5-10 degrees below normal
Monday, to near seasonal norms by mid-week.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Flood Watch through this evening for UTZ113-114-116>120-122-
     124>128.

WY...None.
&&

$$

PUBLIC...Warthen
AVIATION...Merrill
FIRE WEATHER...Merrill

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