Area Forecast Discussion
Issued by NWS Rapid City, SD
Issued by NWS Rapid City, SD
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650 FXUS63 KUNR 272316 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 516 PM MDT Mon May 27 2024 .KEY MESSAGES... -Mainly dry and warmer into Wednesday. -Showers and thunderstorms return for the last half of the week. Severe storms possible Wednesday afternoon and evening. && .DISCUSSION...(This Evening Through Monday) Issued at 123 PM MDT Mon May 27 2024 Active flow over the northern Pac will continue to offer progressive mean westerly flow through most of the forecast period. Mainly quiet weather ongoing across the fa today. Shortwave trough is progressing across ND, with an associated sfc trough supporting a few showers/storms there. Current ob trends (supported by hires models) shift all precip east of the FA this afternoon/evening, with dry conds expected. However, if enough instability and forcing arises over far NW SD, an isold shower would be possible there through early evening. Have continued with a dry forecast attm. The next stronger upper trough will advect into the region Tue, supporting WAA and shortwave ridging. Expected a quiet day Tues with warmer temps than today into the 70s most areas. Upper trough will shift east with sfc pressure falls ensuing Tues night, supporting the the development of a LLJ. This will allow sfc winds to increase trough the night. In addition, Pos theta-e adv combined with steep mid-level lapse rates may support elevated nocturnal showers/storms on the SD plain late Tue night. Did add a low pop for this. Thermal ridge will pass over the region Wed with gusty SE winds per ongoing pressure falls. Temps will climb into the 80s most places, but may struggle a bit at first given SE winds under a strong inversion. Decent ridge of ll moisture will nose into the region along the high plains, with dewpoints expected into the upper 50s and lower 60s. Lee side trough will kick out in the afternoon, timing with the upper trough, supporting increasing chances for showers and storms, first over NE WY and the northern BH (per eddy convergence). Expecting storms to organize into a broken line with embedded strong to severe cells, esp over NW SD where the strongest forcing will be. Bulk shear is not that great, but ML CAPE in the 1.5-2kJ/kg will me more than ample to support a few severe storms as the line shifts east in the evening. Cold front will progress through Wed night with shower chances shifting east. Much cooler Thurs, with instability showers possible in the afternoon, esp SE of the BH. Large upper trough will slowly progress through southern Canada through the end of the week offering seasonal temps into the weekend locally, with continue near daily chances for showers/storms as impulse ladden flow (stemming from the parked NE PAC upper trough) continues to traverse the region. Warmer temps do look possible by Sunday into the following week, as flow amplifies and WSW flow becomes established in mean model solutions. && .AVIATION...(For the 00Z TAFS Through 00Z Tuesday Evening) Issued At 516 PM MDT Mon May 27 2024 VFR conditions will continue through the forecast period. Breezy northwesterly winds will decrease early this evening. A light shower or two could clip portions of far northwest SD early this evening, mainly across the Lemmon area. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION/KEY MESSAGES...JC AVIATION...26