FXUS63 KUNR 200944

AFDUNR



Area Forecast Discussion For Western SD and Northeastern WY

National Weather Service Rapid City SD

344 AM MDT Wed Aug 20 2025



.KEY MESSAGES...



- Hot and dry today through most of Thursday, with near-critical

  to locally critical fire weather conditions anticipated over

  portions of the area.



- Unsettled conditions return late this week as temperatures

  moderate behind a front.



&&



.DISCUSSION...(Today Through Tuesday)

Issued at 343 AM MDT Wed Aug 20 2025



Upper level ridge axis stretches across the Northern Plains today

with attendant low level thermal ridge developing over the CWA. 

Afternoon temperatures will climb into the upper 90s to low 100s 

across most of the CWA with highs in the upper 80s across the 

higher elevations of the Black Hills. The drier airmass should 

keep heat indices from reaching criteria level (100F) in most 

spots precluding issuance of a heat advisory at this time. That 

being said, some spots in the eastern third of our CWA could see 

heat indices in the triple digits this afternoon. The hot, dry, 

and breezy conditions will also lead to fire weather concerns, 

will elaborate further in the Fire Weather Discussion.



Upper low over Canada scrapes by the region with attendant sfc 

trof/cool front pushing through the CWA during the day Thursday. 

This should push the hottest temperatures to south central SD with

the rest of the CWA being in the 80s to low 90s. In terms of the 

potential for storms, there will be a strong cap in place thanks 

to the warm 850mb-700mb temps. So while we could see a few showers

and storms along the front as it passes through, not anticipating

any widespread convection and severe potential appears to be 

limited at this time as better deep layer shear lags behind the 

front. Highs on Friday will be 10-20 degrees cooler, staying in 

the mid 70s to 80s across much of the region with temperatures 

cooling off further through the weekend as a trof digs into the 

eastern half of the US and northwest flow develops over the 

region. In terms of precipitation chances, positioning of the low-

level baroclinic zone and large-scale ascent will keep chances for

precip to our south with the southwestern half of the CWA seeing 

the best chances for showers/storms over the weekend.



&&



.AVIATION...(For the 06Z TAFS Through 06Z Wednesday Night)

Issued At 1036 PM MDT Tue Aug 19 2025



VFR conditions are expected for the rest of the forecast period. 

Low level wind shear will be possible tonight through sunrise 

across far western SD and northeast WY.



&&



.FIRE WEATHER...

Issued At 343 AM MDT Wed Aug 20 2025



Near critical fire wx conditions are expected across much of the 

area today. Temperatures this afternoon will climb into the upper 

90s to low 100s with minimum RHs at or below 20% across much of 

western SD into northeastern WY. Northeastern WY into southwestern

SD could see critically low RH values (15% or lower) with breezy 

southerly winds developing through the afternoon hours. Lowest RH 

values and strongest winds won't overlap considerably in time and 

space, so will hold off on issuing any fire weather headlines. 

However, locally critical fire wx conditions are possible this 

afternoon, especially across northeastern WY into southwestern SD.





Elevated to near critical fire wx conditions are possible again 

on Thursday as a cold front pushes through the region. Winds will 

shift to the northwest through the day Thursday with gusts of 

25-30 mph. Temperatures Thursday will still be hot, in the 80s to 

near 100, with minimum RH values in the 25-45% range.



&&



.UNR WATCHES/WARNINGS/ADVISORIES...

SD...None.

WY...None.

&&



$$



DISCUSSION/KEY MESSAGES...Wong

AVIATION...13

FIRE WEATHER...Wong