656
FXUS65 KSLC 271914
AFDSLC

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

.KEY MESSAGES...

- Scattered showers and thunderstorms capable of producing gusty
  outflow winds to 50 mph are expected this evening and overnight
  across the western half of Utah.

- 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...Today`s chances for showers and thunderstorms have
trended later given a delayed push of tropical moisture aloft,
with only some isolated showers and thunderstorms possible across
the higher terrain through the early afternoon. Activity becomes
more scattered this evening, with coverage favored first across
southwest Utah before spreading northeastward through early Monday
morning. Given the environment is not yet primed with deep
moisture, main concerns for storms through this period will be
gusty outflow winds to 50 mph, particularly across the West Desert
and northern Utah where the lower levels remain sufficiently dry.

After a lull in activity across southern Utah overnight behind the
first push of convection, widespread rainfall pushes into southern
Utah early Monday morning as an anomalous upper-level low begins
to track into the Desert Southwest. This low will tap into
substantial amounts of tropical moisture originating from
Hurricanes Polo and Odalys in the Eastern Pacific, while
concurrently producing ample instability given strong diffluence
aloft. As such, showers and thunderstorms overspreading the
region, especially across southern and central Utah where PWAT
anomalies are highest, will be very efficient rainmakers. Some
recent CAMs runs suggest the potential for stronger cells to
produce rainfall rates of 0.7-1.0" per hour at times between
Monday morning and Monday evening, particularly across the
southern Utah mountains, Zion National Park area, and the San
Rafael Swell.

Flash flooding will be the main threat between Monday morning and
Tuesday morning, especially across portions of central and
southern Utah generally east of the I-15 corridor where
instability and moisture is maximized; a Flood Watch has been
issued for these areas given the heightened risk of widespread
flash flooding. One limiting factor to the flash flood risk is the
potential for precipitation to become more stratiform, especially
across southeast Utah, as cloud cover overspreading the region
ahead of the main shield of precipitation Monday morning may limit
instability in this area. Regardless, those heading outdoors
across these areas should consider alternate plans and those
living in these areas should be alert should any Flash Flood
Warnings be issued.

Drier air quickly moves in from the northeast early Tuesday as the
low continues to drop southeastward into Arizona, allowing showers
to taper off across most of northern and central Utah and
southwest Wyoming through the morning hours. Moisture wrapping
around the northern periphery of the low will linger across
southeast Utah throughout the day, however, keeping activity going
in this area. Given soils will be primed from recent heavy
rainfall, the flash flood risk will remain heightened especially
Tuesday afternoon before dry northerly flow overtakes the
remainder of the region overnight into Wednesday.

High pressure develops across the western US on Wednesday and
remains the dominant feature overhead through the remainder of the
week. Models were previously hinting at the potential for a
shortwave to impact the region on Saturday, but has trended
further north with little impact to our region other than
moderating temperatures.

&&

.AVIATION...

KSLC...Wind gusts out of the south in excess of 20kts will continue
through roughly 12z tomorrow morning ahead of an incoming system.
Moisture will continue streaming north resulting in increasing cloud
cover and chances for precipitation, with VCSH developing at KSLC
around 09z before becoming predominately -SHRA around 12z.
Additionally, Thunderstorms may develop near or at the KSLC terminal
as early as 18z tomorrow.

REST OF UTAH AND SOUTHWEST WYOMING...Winds out of the southwest
continue to increase across all terminals as a system continues to
move closer to the region. Additionally, cloud cover and chances for
precipitation continue to increase into early tomorrow morning.
Chances for showers and thunderstorms are expected to increase
across all sites around the 06-12z timeframe tomorrow, lasting
through the remainder of the TAF period.


&&

.FIRE WEATHER...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 Monday morning through late Monday night for
     UTZ117-120-121-123>131.

WY...None.
&&

$$

PUBLIC...Whitlam
AVIATION...Worster
FIRE WEATHER...Whitlam

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