Area Forecast Discussion
Issued by NWS Rapid City, SD
Issued by NWS Rapid City, SD
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200 FXUS63 KUNR 182300 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 500 PM MDT Sat May 18 2024 .KEY MESSAGES... - Warmer Sunday with thunderstorms. Strong to severe storms possible Sunday afternoon and evening across western South Dakota. - Unsettled pattern continues through the coming week and weekend. && .DISCUSSION...(This Afternoon Through Friday) Issued at 1230 PM MDT Sat May 18 2024 Water vapor shows upper low along the ND/Canadian border, flat ridge over the Northern Rockies, and upper low over southwest BC. At the surface, high is building into western SD, with abundant sunshine, some gusty northwest winds, and early afternoon temps in the 50s/60s. Warm front will lift back into the area after midnight tonight, with 50kt low level jet and decent theta-e advection resulting in a few late night showers/storms in our eastern and northern SD zones. On Sunday, upper low currently over southwest BC will dig into the Northern Rockies, with southwest flow aloft through the Northern Plains and temps rebounding into the 70s to mid 80s behind passage of warm front. Cold front will work into far western during the afternoon, with MLCAPE of 1000-2000J/kg. Scattered thunderstorms will develop along the front first in the Black Hills then spreading east onto the western SD plains through the afternoon and early evening. The linear nature of expected storm development along with inverted-v soundings would suggest more of a damaging wind threat. Storms should exit the eastern zones by early evening. Next upper trof digs a little further south across the Intermountain West on Monday. Northwest winds early will veer northeast during the day as surface low develops over CO. Cloudy skies and cool temps expected with highs in the 50s/60s. Lead short wave will result in quite a bit of showers and non-severe thunderstorm activity by late afternoon with precip chances continuing through the night, with better chance for widespread precip in southern half of zones. Cool/wet conditions likely to continue into Tuesday as main upper low/trof shifts into the Central Rockies. Maybe a small break in precip chances on Wednesday behind first departing upper trof, but next trof looks to work into the Rockies by Thursday for more unsettled conditions. The unsettled pattern with a nearly daily chance for showers/storms will continue into next weekend. Temps should be close to seasonal averages. && .AVIATION...(For the 00Z TAFS Through 00Z Sunday Evening) Issued At 458 PM MDT Sat May 18 2024 VFR conditions are expected through most of the TAF period. Isolated late night high based showers and thunderstorms will be possible toward central SD. Otherwise, another low pressure system will cross the region Sunday and support breezy winds and scattered afternoon showers and thunderstorms, mainly across SD. Local MVFR conds and gusty winds will be possible INVOF TS. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION/KEY MESSAGES...Johnson AVIATION...JC