Area Forecast Discussion
Issued by NWS Rapid City, SD
Issued by NWS Rapid City, SD
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564 FXUS63 KUNR 272246 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 446 PM MDT Sat Apr 27 2024 .KEY MESSAGES... - Chances of rain showers return late tonight into Sunday; best chance for measurable precipitation east of Rapid City into south-central SD. - Temperatures trend warmer to near-normal levels Monday into next week with active flow --> near daily chances of rain showers through the week. - Elevated fire weather conditions Monday and Tuesday; cold front arrives with strong winds and dry air behind it for Tuesday afternoon. && .DISCUSSION...(This Evening Through Saturday) Issued at 135 PM MDT Sat Apr 27 2024 Water vapor imagery shows strong upper level closed low centered over SW CO/northern NM this afternoon with a 80-100 knot jet rounding the base of the trough axis. Our (KUNR) 12z RAOB sampled dry air aloft, with driest layer from ~700mb-500mb; this dry air at mid-levels is well identified by the low-and-mid-level WV bands. Surface high pressure is situated to our north, centered over northern Manitoba, with lee cyclogenesis ongoing across the southern/central Plains. Northeasterly surface flow is ongoing with temperatures in the 40s to mid 50s this afternoon. As the closed upper low continues to eject into the Central and Northern Plains tonight, broad upper level ascent will slowly overspread the forecast area with chances of showers returning later this evening into the overnight hours. Recent trends continue to push the surface and mid-level low slightly eastward, with best synoptic and mesoscale forcing remaining south and east of the forecast area along with drier air quickly filtering in across NE WY/far western SD Sunday. As such, both HREF and LREF (GEFS/EPS/GEPS) ensembles have placed the axis of heaviest precipitation south and east of Rapid City, with best chances of QPF >0.25" across south-central SD and areas southeast. Total QPF amounts taper off quickly along the foothills into NW SD and NE WY, where most areas will remain dry. After this system lifts into the Great Lakes, we will see a return to seasonable temperatures Monday through the upcoming week. Active upper level flow will remain in place with near daily chances of rain showers; thunderstorm chances remain low through at least Thursday/Friday. Of particular note, a quick moving shortwave and cold front will clip the forecast area early Tuesday. Winds will shift NW and ample mixing will result in potential for advisory level wind gusts Tuesday afternoon across NW SD. Moisture will be limited with very dry boundary layer during peak heating -> elevated fire weather potential across much of the forecast area. && .AVIATION...(For the 00Z TAFS Through 00Z Sunday Evening) Issued At 444 PM MDT Sat Apr 27 2024 CIGS over most of western SD will become IFR tonight as upslope flow lowers CIGS and patchy fog develops. Widespread rain will develop east of the Black Hills later tonight, esp toward scentral SD. Over northeastern WY, expect mainly VFR conditions. && .FIRE WEATHER... Issued At 135 PM MDT Sat Apr 27 2024 Temperatures will trend back toward seasonable levels by Monday through the week. Winds will shift southwesterly for Monday with breezy conditions and RH falling into the teens to near 20% across NE WY and portions of SW SD Monday afternoon. A quick moving cold front will arrive early Tuesday morning. While a few spotty showers are possible through the late morning/early afternoon hours, most areas will remain dry. Drier air and gusty NW winds will push in behind the front. Daytime minimum RH from ~12-30% (driest NE WY into the Black Hills and western SD plains) coupled with sustained NW winds 15-20+ mph with gusts 35-50 mph will support near- critical fire weather conditions Tuesday afternoon and evening. Will continue to monitor Tuesday for possible fire weather headlines. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION/KEY MESSAGES...SE AVIATION...JC FIRE WEATHER...SE