876 FXUS63 KUNR 221802 AFDUNRArea Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 1202 PM MDT Mon Sep 22 2025
.KEY MESSAGES...
-Cool front will bring breezy winds and a few showers/storms to the area today
-Dry with temperatures at or above normal the rest of the week
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.DISCUSSION...(Today Through Sunday) Issued at 1257 AM MDT Mon Sep 22 2025
Northern Rockies trough will track south into the central Rockies today and force a cold front through the area. After this trough passes through the region, a blocking ridge will then build into the western and central CONUS, supporting dry and warm weather through the remainder of the week. Mostly clear skies and light winds across the FA this morning. Moist easterly upslope flow may allow for a few areas of fog this morning on the SD Plains. Upper trough will dive SE into the central Rockies today, forcing a cold front into the region. Main lobe of forcing will shift southwest of the FA with the best rain chances. However, plenty of moisture will be on the east side of this system, supporting decent elevated CAPE over southwest SD. Progs suggest 1-2 KJ/KG of elevated CAPE just east of the Black Hills on the SD Plains INVOF of a trough axis aloft. This will allow for convection to develop later this afternoon and evening, somewhere between Rapid City and Phillip on a north south axis as many hires models suggest, with convection zippering south along the trough. Given progged CAPE values, cannot rule out a few stronger cells capable of larger hail. However, any storms will likely be of a pulse nature given lack of sufficient cloud bearing shear. Outside of this area of focus, other high based showers will be possible, generally along and south of I90. Shower activity will then shift south out of the area overnight with the upper trough`s support. In addition to rain chances, gusty northwest of 25 to 45 mph are expected on the far western SD Plains today, breeziest east of the Black Hills, with winds gradually tapering off through Tuesday. Upper ridge will then build across the Northern Plains the rest of the week as a quasi-omega block develops, with dry weather and at or above normal temps across the region. Highs will generally be in the 70s and 80s with mostly clear skies. Given an active northern stream, there will be the potential for backdoor cool fronts to advect into the area later in the week. However, nothing of significance is progged attm.
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.AVIATION...(For the 18Z TAFS Through 18Z Tuesday) Issued At 1201 PM MDT Mon Sep 22 2025
An upper level trough and associated cold front will bring breezy NW winds and a chance for showers and thunderstorms to the area this afternoon and evening. TS will be possible INVOF KRAP and across southwest SD this evening. Have added a prob30 for this. Otherwise, rain will shift south out of the area overnight. Winds are expected to weaken closer towards the end of the TAF period.
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.UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. &&
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DISCUSSION/KEY MESSAGES...JC AVIATION...Bunker
NWS UNR Office Area Forecast Discussion