Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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066 FXUS63 KDMX 301737 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1237 PM CDT Thu May 30 2024 ...Updated for the 18z Aviation Discussion... .KEY MESSAGES... - Showers and thunderstorms return this evening in western Iowa, expanding central and east on Friday. Severe threat remains quite low. - Additional periodic showers and thunderstorms this weekend and into early next week && .DISCUSSION... Issued at 245 AM CDT Thu May 30 2024 The next wave on track for Iowa is making its way across the plains early this morning. So far the only notable changes locally have been increasing cloud cover across parts of western Iowa. As the southern stream proceeds to produce an upper level cut-off the low the entire pattern slows. This means that in Iowa precipitation will be delayed, reaching parts of western Iowa by this evening. SO while increasingly cloudy, today will be a nice day in the upper 70s. Winds will become breezy with gusts of 20-25+ mph by this afternoon as the pressure gradient continues to tighten across the area. Showers and thunderstorms finally enter the area this evening and pass across the area through the overnight. CAMs have picked up on a gradual fade out of the precipitation as it moves east overnight as the southern stream cuts off forcing and better moisture into the area. The extent is still very much up for debate with the HRRR much more aggressive in diminishing precipitation overnight with other CAMs hang onto spotty showers through Friday morning. By Friday afternoon some redevelopment of convection is expected along the boundary, though where exactly that sets up will depend on how precipitation plays out this evening. While the HRRR was most aggressive in fading precipitation on Thursday night it is also most aggressive with redevelopment on Friday afternoon. Given how the dominant southern stream looks to prevent better moisture return, would suspect that that solution is a bit overdone. In any case, models show weak instability and little shear so any severe risk with these showers and storms is quite low. Models struggle to get this system out of the area with both the GFS and Euro lingering a weak boundary across the area into Saturday with the northern stream. This is followed up quickly with a shortwave swinging across the northern plains and meeting Gulf moisture into the area Sunday into Monday. And, as a more active pattern sets up again, a more robust system looks to move across the area Tuesday into Wednesday. While it is still several days out and model inconsistencies exist, this system is worth monitoring as better forcing looks to impact the area. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1233 PM CDT Thu May 30 2024 Unusually high uncertainty remains with regards to precipitation and thunder potential during this TAF period. Guidance remains widely spread on evolution across the area, affecting all TAF sites. With the broader trend of greater thunder chances residing north and south of the area, have limited mentions of VCTS to KFOD and entered VCSH at remaining sites. Prevailing MVFR cloud cover will be most likely west during latter portions of the period, but confidence not great enough to have prevailing at KFOD or KDSM at this point. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hagenhoff AVIATION...Curtis