352 FXUS63 KUNR 141734 AFDUNRArea Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 1134 AM MDT Sun Sep 14 2025
.KEY MESSAGES...
- Soggy Sunday for sections of western SD
- Drying out and warmer on Monday
- Becoming more unsettled mid-week
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.DISCUSSION...(Today Through Saturday) Issued at 241 AM MDT Sun Sep 14 2025
Latest water vapor imagery shows a negative tilted 500hpa trough located across eastern MT south into eastern NM, with closed 500hpa low spinning across northeast CO/southeast WY. Plenty of moisture is streaming northward into the northern high plains in advance of this low, with radar showing widespread showers from SW SD into central SD. Water vapor imagery also shows mid-week system crashing onshore in OR, with ridging taking place between the two 500hpa lows. At the surface, low pressure is located in SW Neb/NE CO with an inverted surface trough poking northeast into central ND.
Aforementioned 500hpa trough will continue to move eastward, impacting the CWA through much of the day. Southerly fetch of Gulf moisture will spell cloudiness over the region through the day, helping to keep temps in check when compared to previous day. Light northeast to easterly winds will produce upslope low clouds along the east side of the Black Hills for much of the day. There is some concern as to how far west the northward advancing rain shield will make it, given dry air already trying to push in from Wyoming. Feel that most of the pcpn will be confined around the inverted surface trough that is located east of the Black Hills, so that is where the highest pops will be confined for much of the day today. This is also where ensembles are painting the highest probabilities (45-70%) of seeing daytime rainfall totals > 1 inch. This also lines up fairly closely with 700hpa trowal analysis. 700Hpa theta-e downglide begins to impact the western CWA by 21Z this afternoon, which should lead to decreasing cloud cover and overall improving conditions.
As the 500hpa trough rotates/lifts northeast out of the area, will see generally improving conditions and an end to the rainfall during the evening and overnight hours. The far northeast part of the CWA will be the last to dry out and see the decrease in cloud cover overnight. Ridging will move into the area to start the week off on Monday, with increasing 850hpa temps. It still appears that the warmest part of the CWA will be SW SD where some low 90s cant be ruled out.
Beginning Tuesday and for the rest of the week, things look to be more unsettled as next 500hpa trough impacts the northern plains. Models show this trough deepening, with closed 500hpa low actually developing and diving into the CWA during the day on Thursday. This should lead to plenty of cloud cover, keeping a lid on temps as well as keeping daily chances for showers/storms in the forecast. Of interest might be the temps for next weekend. Models are suggesting single digit 850hpa temps following on the heels of the exiting closed 500hpa moving into the region. Coupled with subsidence helping to scour out any potential clouds, it could set the stage for some chilly mornings. However, that far out, things will most likely change several times before next weekend arrives.
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.AVIATION...(For the 18Z TAFS Through 18Z Monday) Issued At 1122 AM MDT Sun Sep 14 2025
MVFR conditions will continue at RAP through around 20Z. VFR conditions are then expected to prevail through across the airspace. Isolated showers will impact RAP through 01Z, aided by a frontal movement. Northeast winds will shift south/southwest this evening behind showers.
AEH
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.UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. &&
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DISCUSSION/KEY MESSAGES...Hintz AVIATION...Herdliska
NWS UNR Office Area Forecast Discussion