Ideal, South Dakota Weather Forecast Discussion

024
FXUS63 KUNR 301117
AFDUNR
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
517 AM MDT Tue Sep 30 2025
.KEY MESSAGES...
- Significantly above average temperatures with elevated fire
  weather conditions through Thursday
- Gusty southerly winds today
- Pattern change Friday into next week
&&
.DISCUSSION...(Today Through Monday)
Issued at 242 AM MDT Tue Sep 30 2025
08z surface analysis had lee trough from central MT into eastern
CO with a weak trough across southern SD. This trough weakly
focusing 40kt low level jet over south-central SD, creating
isolated very weak convection per regional radar loop. Water
vapour loop had upper ridge over the Great Lakes and upper trough
approaching the northwest CONUS. Northern plains in between with
southwest flow aloft and fairly dry mid-level moisture upstream.
Today/tonight, expect unseasonably warm weather with highs 15-20F
above normal, inline with guidance. Lee trough will advance
eastward later today as a cool front tonight courtesy of upstream
shortwave zipping through MT into Canada. Gradient ahead of trough
will support gusty southwest winds in the west and gusty
southerly winds in the east.
Wednesday, behind cool front temperatures will be about 5F lower
than today. Thursday, thermal ridge pops back into the CWA with
MaxT reaching the lower 90s again (15-25F above normal) for many
folks from southwest into south-central SD where 700mb
temperatures hit 10C.
The pattern change starts Friday as upper trough approaches
allowing a series of cold fronts to push through the CWA into
early next week. Friday will be the transition day with the
weekend looking increasingly PoPpy per decent slug of
moisture/shortwave forcing. Sunday/early next week temperatures
will be seasonal, which will feel noticeably cooler compared to
the recent warm spell. Might even be some white stuff over the
higher Black Hills at night. While confidence in the timing of the
cold fronts is low, confidence high with regard to large scale
pattern change.
&&
.AVIATION...(For the 12Z TAFS Through 12Z Wednesday Morning)
Issued At 516 AM MDT Tue Sep 30 2025
Expect VFR conditions through the period. Gusty south to southwest
winds are expected.
&&
.FIRE WEATHER...
Issued At 242 AM MDT Tue Sep 30 2025
Anomalously warm conditions will persist through Thursday with
high temperatures 10-25F above normal across the region. Expect
gusty southwest winds today over northeastern Wyoming and gusty
southerly winds east of the Black Hills. Minimum relative humidity
around 20-30% will preclude any Red Flag warnings, although gusty
winds/dry conditions will create elevated fire weather
conditions. Warm and dry conditions will persist beyond Tuesday,
but winds are not forecast to be as strong. Despite this, plan
for elevated fire conditions with high to very high grassland fire
danger through Thursday. A cold front will bring in cooler air
and increased moisture this weekend into early next week.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&
$$
DISCUSSION/KEY MESSAGES...Helgeson
AVIATION...Helgeson
FIRE WEATHER...Helgeson

NWS UNR Office Area Forecast Discussion