166
FXUS63 KUNR 060436
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1036 PM MDT Tue Aug 5 2025

.KEY MESSAGES...

- Isolated afternoon/evening thunderstorms today and Wednesday.

- Hot and dry Thursday with highs in the 90s to low 100s.

- Cooler for the end of the week into the weekend.

&&

.DISCUSSION...(This Evening Through Tuesday)
Issued at 223 PM MDT Tue Aug 5 2025

Upper level analysis has high pressure over the western High Plains
centered between two trofs - one over the Pacific Northwest and the
other over the Mississippi River Valley. At the surface, an area of
low pressure is centered just east of the Badlands, with a cold
front extending southward through south central South Dakota.
Temperatures at 20Z range from the mid 70s to around 90 degrees.
Additionally, there is an area of high dew points (65-70 degrees)
From Belle Fourche, southeastward to Rapid City and Hot Springs,
and extending northeastward into north central South Dakota.

The air mass over the forecast area is beginning to recover from the
morning convection. Per 18Z sounding at UNR, the area remains pretty
well capped, but instability over the Black Hills is starting to
result in some CU formation. Moderate to strong buoyancy with MUCAPE
of 2000 to 3000 J/kg and moderate shear would mean storms would most
likely go severe IF they can form over the Black Hills late this
afternoon/early evening. Overall, any coverage should remain
isolated. Latest CAMs indicate a storm or two may fire over the
hills and move east across the foothills onto the adjacent plains
between 22Z and 02Z. Model timing looks good, with the moderately
supportive supercell environment. By 06z, any remaining convection
should be east of the forecast area.

For Wednesday, isolated storms are once again possible over the
Black Hills, but the CAP should be stronger, limiting potential.
Have left low pops over the Black Hills for the afternoon and
evening time frame.

Thursday will be the hottest day of the forecast period as strong
southwesterly flow develops ahead of the approaching cold front.
This will bring warmer air in from the southwest, allowing
temperatures in the 90s and low 100s. For portions of northeastern
Wyoming, the southern Black Hills, and far southwestern South
Dakota, the combination of high temperatures, lower relative
humidity and gusty winds will likely result in elevated fire
weather conditions.

A cold front will move through the area Thursday night and Friday,
bringing cooler temperatures, gusty northwest winds across the
western SD plains, and a higher chance for precipitation.

For the weekend, seasonal and mainly dry conditions are expected
as the upper trof moves off to the east and surface high pressure
build over the area. Although it looks fairly dry, a storm or two
is possible over the Black Hills or near the Nebraska border.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Wednesday Night)
Issued At 1032 PM MDT Tue Aug 5 2025

An isolated storm can`t be ruled out over the Black Hills
tomorrow afternoon. Otherwise, VFR conditions expected through
the valid TAF period.

&&

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

$$

DISCUSSION/KEY MESSAGES...Smith
AVIATION...Wong