228 FXUS63 KUNR 150744 AFDUNRArea Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 144 AM MDT Mon Sep 15 2025
.KEY MESSAGES...
-Warmer today with isolated showers and thunderstorms mainly this evening
-Cooling trend into mid week with another upper low bringing more chances for rain
-Drying out and warming up by the weekend
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.DISCUSSION...(Today Through Sunday) Issued at 143 AM MDT Mon Sep 15 2025
Unsettled weather pattern will continue as yet another upper low takes aim at the region. Semi-blocked pattern will develop by mid week as an upper low slowly migrates east into the Northern Plains and a sharp ridge develops over western NOAM. This will set the stage for more rain chances, with the best chances for rain still to be determined. This type of flow pattern is handled poorly in forecast models as the path of the upper low tends to be highly variable. There will be the potential for locally heavy rain somewhere in the region given slow movement of the system and resultant showers. Much warmer conditions today as the BL mixes out deeply ahead of the Northern Rockies upper trough. Inverted V profiles with steep lapse rates will support high based shower activity later in the day, with convection expected to move into northeast WY first, spreading east into western SD by evening. Dry LL profiles will support gusty winds with stronger cells, with the potential for isolated severe wind gusts in the western 2/3. Not expecting much in the way of precip given high based nature of cells. Convection will move northeast and wane overnight, with the sfc trough shifting through the FA. Cooler Tues most areas, except for scentral SD where 80s are expected for highs. Upper trough will meander into the region supporting increasing chances for shower and storms Tues afternoon into Wed, with the best chances Wed across the FA. As mentioned before, the best overlap of lift and moisture convergence is still to be determined and will likely fluctuate in later model runs. Hence, low confidence remains per QPF details, particularity the areas where the highest numbers will be. Some places will likely see over an inch of rain once again. Things dry out toward the end of the week, with warmer and drier weather for the weekend.
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.AVIATION...(For the 06Z TAFS Through 06Z Monday Night) Issued At 1138 PM MDT Sun Sep 14 2025
VFR conditions are expected through most of the period. Isolated to scattered showers are possible towards the end of the period with an approaching system, but confidence is still too low for a mention in the TAFs. Winds should remain south or southwesterly for much of the period near RAP before turning more northwesterly Monday evening. Meanwhile, winds near GCC should become northwesterly during the day Monday and persist.
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.UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. &&
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DISCUSSION/KEY MESSAGES...JC AVIATION...Melo
NWS UNR Office Area Forecast Discussion