631
FXUS63 KUNR 140417
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1017 PM MDT Wed Aug 13 2025

.KEY MESSAGES...

- Hot through Thursday with elevated to near critical fire weather
  conditions for parts of northeast WY and southwestern SD

- Slight risk (level 2 of 5) of severe storms this afternoon and
  evening

- Daily chances for thunderstorms through the weekend

&&

.DISCUSSION...(This Evening Through Wednesday)
Issued at 145 PM MDT Wed Aug 13 2025

Current Water Vapor and upper models depict near zonal flow over
the forecast area and an upper ridge situated over the
southwestern CONUS. Surface analysis shows the low over
southeastern MT with a boundary running south into WY this
afternoon. Temperatures currently sit in the mid 80s and 90s.

Boundary treks across the forecast area this afternoon and
evening, bringing some storms through the CWA. Steep lapse rates
along with 1000-1500 j/Kg CAPE and 30-45kts effective shear will
support severe storms through early this evening before we lose
diurnal support. Damaging winds will be the main threat, however
indices support potential for marginally severe hail.

Upper high in the southwestern CONUS shifts eastward later today
though Thursday, bringing southwest flow and even drier air for
Thursday. Decent capping expected on Thursday, however models
hint at another wave moving through possibly the southern half of
the CWA, which may help to fire off some storms. Less confidence
on severe potential for Thursday, however a strong cell or two is
not out of the question. Thermal ridging continues for Thursday
as well, with widespread 90s and possibly a few low 100s expected.
Heat indexes marginal to support heat advisory for south central
SD in the afternoon, and after collaborating with neighboring
offices will punt any potential headlines to the overnight shift.

Over the weekend, more seasonable temperatures move in. Upper
southwest flow shows multiple waves moving over the CWA,
supporting daily chances for storms. Long range models show upper
ridge amplifying over the northern and central plains, which will
continue our trend for temperatures at or a bit above normal.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Thursday Night)
Issued At 1017 PM MDT Wed Aug 13 2025

VFR conditions expected through the TAF period.

&&

.FIRE WEATHER...
Issued At 145 PM MDT Wed Aug 13 2025

Elevated to near-critical fire weather conditions are expected for
portions of northeastern WY and southwestern SD today/Thursday.
MinRH values will bottom out in the low teens over the far
southwest Thursday. Wind speeds will be marginal for a Red Flag
Warning in southwestern SD Thursday, so have held off any
headlines for the time being.

&&

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

$$

DISCUSSION/KEY MESSAGES...Dye
AVIATION...Wong
FIRE WEATHER...Dye