564
FXUS63 KUNR 151752
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1152 AM MDT Mon Sep 15 2025

.KEY MESSAGES...

-Warmer today with widely scattered showers and thunderstorms this
 afternoon and evening

-Cooling trend into mid week with another upper low bringing more
 chances for rain

-Drying out and warming up by the weekend

&&

.DISCUSSION...(Today Through Sunday)
Issued at 143 AM MDT Mon Sep 15 2025

Unsettled weather pattern will continue as yet another upper low
takes aim at the region. Semi-blocked pattern will develop by mid
week as an upper low slowly migrates east into the Northern Plains
and a sharp ridge develops over western NOAM. This will set the
stage for more rain chances, with the best chances for rain still
to be determined. This type of flow pattern is handled poorly in
forecast models as the path of the upper low tends to be highly
variable. There will be the potential for locally heavy rain
somewhere in the region given slow movement of the system and
resultant showers. Much warmer conditions today as the BL mixes
out deeply ahead of the Northern Rockies upper trough. Inverted V
profiles with steep lapse rates will support high based shower
activity later in the day, with convection expected to move into
northeast WY first, spreading east into western SD by evening. Dry
LL profiles will support gusty winds with stronger cells, with
the potential for isolated severe wind gusts in the western 2/3.
Not expecting much in the way of precip given high based nature of
cells. Convection will move northeast and wane overnight, with
the sfc trough shifting through the FA. Cooler Tues most areas,
except for scentral SD where 80s are expected for highs. Upper
trough will meander into the region supporting increasing chances
for shower and storms Tues afternoon into Wed, with the best
chances Wed across the FA. As mentioned before, the best overlap
of lift and moisture convergence is still to be determined and
will likely fluctuate in later model runs. Hence, low confidence
remains per QPF details, particularity the areas where the highest
numbers will be. Some places will likely see over an inch of rain
once again. Things dry out toward the end of the week, with
warmer and drier weather for the weekend.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1147 AM MDT Mon Sep 15 2025

VFR conditions will continue this TAF period at airports. Widely
scattered thunderstorms are expected to develop this afternoon
and evening, with strong and variable wind gusts to 40 kts
possible in and near any storms. Fropa will veer winds to
northwest this evening, with northwest winds continuing tonight
but becoming northerly on Tuesday morning. VCSH are anticipated
at airports late in the TAF period as an upper level area of low
pressure spins overhead.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...JC
AVIATION...Shamburger