629
FXUS65 KSLC 300409
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
1009 PM MDT Sat Aug 29 2026

.KEY MESSAGES...


- Thunderstorms capable of periods of heavy rain and flash
  flooding will once again be possible Sunday and Monday,
  particularly east of the I-15 corridor and south of I-80. A
  Flood Watch is in effect.

- A few isolated thunderstorms may become strong to severe Sunday
  and Monday, capable of strong winds and hail.

- Generally drier conditions return Tuesday on through the work
  week, though more isolated showers and thunderstorms will remain
  a possibility many of those days.

&&

.DISCUSSION...After an active day, weather remains active across
portions of Utah this evening. This is to an extent the result of
a deepening PacNW trough helping to strengthen a Pacific moisture
tap within the associated enhanced southwesterly flow. To that
end, mesoanalysis maintains widespread PWAT values in excess of 1"
across the majority of Utah, or around 150-200% of climatological
normal for late August. Further, the aforementioned deepening
PacNW trough has allowed a frontal boundary to slowly advance into
northern Utah, and the abnormally strong deep layer flow overhead
has allowed for impressive effective shear on the order of 40-60
kts across the northern half of Utah, and around 20-40 kts across
southern Utah. This anomalous combination of ingredients has
yielded numerous strong to severe thunderstorms with strong winds
and hail, and heavy rain resulting in multiple instances of flash
flooding.

Looking ahead to the overnight hours, while overall instability
will decrease with the lack of sun, enough will remain in
combination with ample moisture to result in continued showers and
thunderstorms. In general, anticipate these to tend to be weaker
than those during the daytime Saturday. That said, wouldn`t rule
out one or two pulsing up at times, and with the moisture rich
environment, any stronger Storm or training storm impacting a rain
sensitive basin in particular could pose a flash flood threat. In
terms of coverage, models largely support the bulk of the
scattered activity across portions of central Utah, in the rough
vicinity near and to the south of the frontal boundary.

Sunday appears to have potential to be another active day capable
of strong storms and flash flooding. In terms of the broader
synoptic environment, the ingredients don`t appear to change
significantly, with an embedded midlevel shortwave impulse also
shifting through. Strong flow will remain overhead allowing
moisture will continue to advect into the region. One difference
is it appears some slightly drier air will start to shift into
Utah from the west, with the best available moisture becoming
positioned across eastern Utah to southwest Wyoming, generally
along/east of the I-15 corridor and south of I-80. As such, this
area is highlighted as Slight Risk (categorical 2/4) for excessive
rainfall from WPC, and much of it is also included in a Flood
Watch for potential flash flooding. Elsewhere across all but far
west to northwest Utah, a Marginal Risk (categorical 1/4) of
excessive rainfall is noted. These areas will need to remain
weather aware for strong storms capable of periods of heavy
rainfall once again, with flash flooding especially possible in
those typically sensitive basins (recent burn scars, slot canyons,
typically dry washes, and slickrock areas). One possible
difference is that shear appears to be maybe around 20 kts or so
weaker than Saturday, which may limit the coverage of strong to
severe storms. Still, would anticipate a few organized storms will
still be capable of strong gusty winds and hail.

Monday will yet again see the potential for flash flooding and
strong storms. Overall, the synoptic elements once again do not
shift significantly, and another shortwave impulse will lift
through overhead during the day. Like Sunday, the expectation is
that while strong to maybe a few severe storms will certainly be
possible, the moisture rich environment will favor flash flooding
as the primary risk. As far as the excessive rainfall outlook, the
slight and marginal risk areas change very little from that of
Sunday, and thus the same areas will remain more favored for the
threat. With multiple days of repeat thunderstorms, saturated
soils and any remaining high creeks/rivers/etc. may further
exacerbate this potential.

The deep PacNW trough will more or less maintain its position
Tuesday onward through the upcoming week, but the moisture tap
will become less defined. As such, a general drying trend is
expected across the forecast region, and the threat of widespread
heavy rainfall generally appears lower. Still, the PacNW trough
will offer potential for some grazing shortwaves, and there will
still be enough moisture lingering to result in the development of
some showers and thunderstorms day to day. Even if the threat of
widespread heavy rain may be lower, any stronger or slower moving
storm that gets over a rain sensitive basin will pose a risk, so
cannot say the threat is zero. Overall though, there is some
uncertainty noted in the day to day specifics.

Though on the tail end of the forecast range, next weekend bears
at least some watching. Deterministic models show potential for
the Pacific moisture tap to become reestablished, with ensembles
showing a corresponding increase in mean PWAT values. It does
appear there are some factors that`ll influence how it trends
though, particularly the exact position of the PacNW trough, a
broad central Plains to Rockies ridge, and position/strength (if
it exists) of an east Pacific tropical system. So, not much in the
way of specifics, but as typically the case a week out, worth
watching trends.

&&

.AVIATION, Issued 551 PM MDT Sat Aug 29 2026...


KSLC...Southerly winds are expected to prevail through the evening
and into the morning, with passing showers and thunderstorms causing
periodic gusty and erratic winds. The strongest storms will be
capable of producing heavy rainfall that may result in periods of
MVFR to IFR conditions.

REST OF UTAH AND SOUTHWEST WYOMING...For northern terminals,
widespread showers and thunderstorms are expected to persist through
the evening and into early morning before dissipating. The strongest
storms will be capable of producing gusty and erratic outflow winds
and heavy rainfall that may result in periods of MVFR to IFR
conditions. Southern terminals will remain gusty into early evening.

&&

.FIRE WEATHER, Issued 1226 PM MDT Sat Aug 29 2026...
Active weather continues today with strong to severe
thunderstorms developing this afternoon across northern and
central Utah with a flash flooding threat also developing this
afternoon across central and southern Utah. Regarding the severe
threat further north, wind gusts in excess of 58-70mph and hail to
around 1" are expected this afternoon with any of the stronger
storms that form. Across southern Utah, monsoonal moisture
continues to surge north bringing an attendant flash flooding
threat to the area through at least Monday. While storm
development across southern Utah may be somewhat muted Sunday
afternoon, Monday appears somewhat concerning regarding rainfall
high rainfall rates and amounts. Regardless, a wetting rain is
expected across the entirety of Utah through early next week.

Following this active patter, a drying and cooling trend will take
place as most showers and thunderstorms appear to remain confined
to the higher terrain at this time. Temperatures will run roughly
5F below seasonal normals with RH approaching normals around mid-
week.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Flood Watch through Monday evening for UTZ116>121-123>131.

WY...None.
&&

$$

PUBLIC...Warthen
AVIATION...Verzella
FIRE WEATHER...Worster

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