979
FXUS65 KSLC 131840
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
1240 PM MDT Sun Sep 13 2026

.KEY MESSAGES, Issued 1005 PM MDT Sat Sep 12 2026...


- An isolated flash flood threat will persist over southeast Utah
  to start the week as monsoon moisture lingers.

- Breezy winds will be in place today ahead of an approaching
  cold front, bringing wind gusts to 40 mph to portions of western
  Utah as well as Uinta county, Wyoming.

- The front will move through the northwestern half of the
  forecast area late today into Monday, bringing noticeably
  cooler and drier conditions behind it. Warmer temperatures and
  elevated moisture will persist over southeast Utah.

&&

.DISCUSSION, Issued 1105 AM MDT Sun Sep 13 2026...
Morning water vapor and H5 analysis place Utah
within a deep southwesterly flow as a deep upper low resides
upstream over eastern Washington, and mean ridging remains
centered near the New Mexico/Texas border. Coincident with the
upper low, a surface cold front is draped from roughly EKO to PIH
with leading edge just now pushing into extreme northwestern Utah.
South of this front the S-N MSLP gradient is driving gusty
southerly winds across much of the forecast area this morning
which are only poised to increase further with continued
slow encroachment of the front and heating of the day. Gusts to
40 mph remain likely across much of western Utah as such.

Deep layer moisture continues to advect SW-NE across the
southeastern third of the state, with PW`s between .8-1.0"
extending from the UT/AZ border region on up through Castle
Country. CAMs continue to advertise modest diurnal destabilization
beginning early afternoon within this plume, and given surface
dewpoints largely in the low-mid 50s and favorable H8.5-H7 mixing
ratios existing across the southeast, will once again be watching
for isolated flash flood threats from the convection that
initiates within this zone this afternoon. Modest shear along the
northern periphery of this zone will also aid the potential for
isolated organized cells in east-central Utah.

The aforementioned cold front will sag through the northwestern
third of the state later today/tonight as a largely dry feature,
but solid CAA coincident with the baroclinic passage will
significantly knock temps down for Monday in its wake. Highs
across the north will drop to some 10 degrees below climo on
Monday north of the boundary, but change only minimally across the
remainder of the forecast area to the south and east. What is a
bit more notable is that the this front will begin to pin moisture
a skosh more to the south and east early in the week, but not
completely out of the area maintaining a diurnal heavy rain threat
with afternoon convection (namely far southern/eastern portions of
the area).

Minimal change in the gross large scale pattern is evident through
Tuesday, but details in the delineation of dry SW flow vs. deeper
layer moisture associated within the return flow begin to wane
midweek. Driving force behind this are subtle differences in
amplitude/placement of the next upper level low which is expected
to carve southeast into the western Great Basin region. Consensus
attm shifts the return flow moisture gradient further west
beginning Wednesday, increasing diurnal convective potential for
the eastern half of the area (at least) during the latter half of
the week.


&&

.AVIATION, Issued 1105 AM MDT Sun Sep 13 2026...


KSLC...Gusty southerly winds will continue through the early
afternoon, with gusts to 20-30kts. A frontal boundary will produce a
transition to northwesterly between 21-22z. Winds may then lighten a
bit between 00-04z before gusting again to around 20-25kts out of
the northwest after 04-05z. VFR conditions will prevail with mostly
clear skies.

REST OF UTAH AND SOUTHWEST WYOMING...Gusty southerly winds will
persist across most areas with gusts to 20-35kts. Isolated to
scattered thunderstorms will develop again after 18z mainly east of
KBCE-KU69, though a shower or two may develop over higher terrain in
the vicinity of KCDC. A frontal boundary will begin to push through
northern Utah after 18z, with a secondary push of gusty
northwesterlies late in the evening. VFR conditions will prevail
with mostly clear skies.

&&

.FIRE WEATHER...Widespread gusty southerly winds exist this
afternoon as a cold front is slowly tracking in from the
northwest. The strongest winds exist across western Utah in
advance of this front, with current location of the front draped
from SW-NE across the Great Salt Lake. Cooler temperatures and a
period of gusty northwest winds will move in behind the frontal
passage prior it stalling across central Utah in roughly 24 hours
time. South of this front, gusty southwesterly winds will remain
in place.

Monsoonal moisture continues to focus across southeastern Utah
today, and this trend will continue through early this week.
Currently this moisture is most prevalent from FWZ 498 northeast
through FWZ 489, and these will be the primary areas for isolated
thunderstorms capable of heavy rainfall in the short term. Due to
the front moving into central Utah over the next 24 hours, this
zone of thunderstorm potential is expected to shift slightly east
early week.

A gradual warming trend is expected to begin on Tuesday across
the northern half of district, but temperatures are only expected
to rebound to near seasonal normals mid/late week. Monsoonal
moisture has the potential to spread across much of
central/southern portions mid to late week, but confidence remains
lower than normal at this time.

&&

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

$$

PUBLIC...Merrill
AVIATION...Cunningham
FIRE WEATHER...Merrill

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