439
FXUS63 KUNR 310816
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
216 AM MDT Sun Aug 31 2025

.KEY MESSAGES...

- Unsettled again today, especially east of the Black Hills
- Warmer Monday/Tuesday ahead of a cold front for Tuesday night
  that brings a short-lived cooldown Wednesday along with a chance
  of precipitation

&&

.DISCUSSION...(Today Through Saturday)
Issued at 212 AM MDT Sun Aug 31 2025

08z surface analysis had trough from central MT into central NE,
which is a reflection of sheared upper trough from eastern MT
into eastern NE per water vapour loop. Regional radar loop had
shra/isolated TS rotating along upper trough with a slow decline
early this morning. Stratus/fog evident over much of western SD
and small parts of northeastern WY per nighttime microphysics
RGB/surface observations. Main concern this forecast is upper
trough in the short term.

Today/tonight, upper ridge over the Rockies inches eastward
pushing sheared upper trough slowly eastward resulting in
decreasing precipitation coverage. 00z KUNR sounding had PWAT of
158% of normal which will support local beneficial precipitation.
Mean MUCAPE this afternoon ~500J/kg with weak shear. Have cut down
temperatures where highest PoPs/cloud cover persists today,
especially over south-central SD. Otherwise, temperatures will be
near guidance.

Monday/Tuesday, Rockies upper ridge builds into MT/WY as upper
trough over Hudson Bay slips southward putting CWA under northwest
flow aloft. Moisture will be limited, but some CAMs suggest
isolated shra/TS may occur during peak insolation. Tuesday
night/Wednesday, a fast-moving cold front brings a chance of
shra/TS along with cooler temperatures. Upper/thermal ridge then
slowly builds back into the northern Plains for the end of the
week into next weekend. Ensemble temperatures spreads about 10F,
which will mean the difference between mild/warm for MaxT.
Precipitation chances will be limited, but not zero.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1033 PM MDT Sat Aug 30 2025

Patchy fog is possible across the western SD plains between 31/10z
and 31/14z with MVFR cigs/vsbys possible as well. Otherwise once
the fog lifts, VFR conds are expected through the remainder of the
valid fcst period for the terminal locations.

&&

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

$$

DISCUSSION/KEY MESSAGES...Helgeson
AVIATION...Hintz