211 FXUS63 KUNR 082328 AFDUNRArea Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 528 PM MDT Mon Sep 8 2025
.KEY MESSAGES...
- Mostly dry and hot conditions until Wednesday.
- Precipitation chances increase towards the end of the week.
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.DISCUSSION...(This Evening Through Monday) Issued at 121 PM MDT Mon Sep 8 2025
Current upper air models show upper ridge over the Rockies, with weak shortwave over western to central South Dakota, and west northwest flow over the forecast area this afternoon. Surface analysis also depicts a surface trough over central SD, while high pressure sits over western Wyoming. Current radar shows a few high based showers/storms over the central and southern foothills, and some elevated showers in far southeastern MT. Temperatures currently sit in the 80s over most of the forecast area, with a few areas right around 90.
Isolated showers/storms will continue this afternoon into the early evening as shortwave treks across the state, though most places can expect to remain dry today. Upper ridge slides eastward into the northern and central plains Tuesday through early Wednesday as a result of upper trough digging into the PAC NW. Weak energy under the ridge once again tries to fire up a few showers/storms during the day Tuesday into early Wednesday morning, mainly over the Black Hills to southwestern and south central SD, though most places can expect to remain dry again.
Later Wednesday upper ridge axis beings to slide east of the FA as the upper trough digs into the southwest CONUS, setting up southwest flow over the region. Shortwave energy ejecting up into the region the latter half of Wednesday will bring another chance for isolated shower/storms.
Closed upper low develops at the base of the western trough, and ejects into the northern Rockies Friday into the weekend. This results in much better chances for widespread showers and thunderstorms across the area, especially from the Black Hills area and west. With the increase in cloud cover and precip, temperatures will be cooler for the end of the week.
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.AVIATION...(For the 00Z TAFS Through 00Z Tuesday Evening) Issued At 519 PM MDT Mon Sep 8 2025
Isolated thunderstorms will continue across south central and north central South Dakota for the next few hours. Otherwise, VFR conditions and light and variable winds are expected overnight. There is a chance for isolated storms again tomorrow afternoon, but confidence is too low to include in the TAF at this time.
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.UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. &&
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DISCUSSION/KEY MESSAGES...Dye AVIATION...Pettett
NWS UNR Office Area Forecast Discussion