Reva, South Dakota Weather Forecast Discussion

107
FXUS63 KUNR 272045
AFDUNR
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
245 PM MDT Sat Sep 27 2025
.KEY MESSAGES...
- Dry and breezy with seasonal temperatures
- Near record temperatures expected tomorrow
- Elevated fire weather conditions possible throughout the weekend
&&
.DISCUSSION...(This Evening Through Saturday)
Issued at 143 PM MDT Sat Sep 27 2025
A high pressure system remains centered of the Colorado front
range but is close enough to continue to influence our weather
across eastern Wyoming and western South Dakota. Water vapor
analysis continues to show a closed low spinning across southern
California and a long wave trough approaching the western CONUS.
Ensemble guidance (GEFS/ECMWF) supports the evolution of the
upper ridge eastward across the northern Plains and into the
Midwest through Monday, with a thermal ridge building over the
region. This will promote above-normal temperatures with the NBM
probabilities of max temperatures greater than 90F around 50-90%
east of the Black Hills on Sunday. We could see near-record highs
on Sunday particularly across central and eastern portions of the
forecast area.
Southwest flow aloft develops on the backside of the ridge by
Monday, enhancing lee troughing across the High Plains. This will
tighten the surface pressure gradient supporting gusty southerly
winds. HREF ensemble probabilities for wind gusts exceeding 45 mph
increase slightly east of the Black Hills Sunday and Monday up
from 20% from where they are today. Downslope wind potential may
also help yield locally gusty conditions in the northern Black
Hills and foothills this evening.
There is a very low chance for some high based convection Monday
afternoon. With the very low confidence, decided to keep PoPs near
zero. We will be tracking a broad upper trough establishes over
the northwest CONUS. This trough will gradually shift into the
northern Plains late week. Ensemble spreads in GEFS/ECMWF suggests
slower progress, with PoPs increasing late Thursday in Friday.
Overall temperatures will trend cooler with PoP chances
increasing.
&&
.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 1153 AM MDT Sat Sep 27 2025
Expect VFR conditions through the period. Gusty southerly winds
with peak gusts around 25-30 kts are possible through this
evening. These gusts may sporadically persist through the
overnight, but confidence is low due to nocturnal low-level
stabilization.
&&
.FIRE WEATHER...
Issued At 143 PM MDT Sat Sep 27 2025
Minimum relative humidities will dip to the 20s to mid 30s this
afternoon. Winds will become south, averaging 10-20 mph over
southern South Dakota and 15-25 mph over northwestern South
Dakota. Gusts from 30-40 mph will occur over northwestern South
Dakota this afternoon, before diminishing during the overnight
hours. Tomorrow we are expecting near record high temperatures
across much of the area with dry conditions. Minimum relative
humidity values will range between 18-26% across much of eastern
Wyoming and western SD. The driest air will be across eastern
Wyoming.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&
$$
DISCUSSION/KEY MESSAGES...Woodward
AVIATION...Melo
FIRE WEATHER...Woodward

NWS UNR Office Area Forecast Discussion