Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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101 FXUS63 KDMX 061139 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 639 AM CDT Mon May 6 2024 ...Updated for the 12z Aviation Discussion... .KEY MESSAGES... - Breezy southeast wind this afternoon, approaching advisory criteria in northwest Iowa. - Strong to severe storms sweep across Iowa this evening and overnight. Damaging wind and perhaps a few tornadoes are the primary hazards. Pockets of locally heavy rain are also possible. - Additional storm chances on Wednesday and into the latter half of the week. && .DISCUSSION... Issued at 245 AM CDT Mon May 6 2024 With high pressure sliding east winds have shifted to southeasterly with increasing scattered cloud cover. Further west we catch an early glimpse at the incoming system moving across the central Rockies. The pressure gradient has tightened ahead of the system across the central plains and will continue to do so into Iowa later today. This will resulting in rather breezy southeast winds gusting over 30-35+ mph at times this afternoon. Convection approaches far western Iowa around 5-7pm and the QLCS will sweep across Iowa through the rest of the evening and overnight before exiting east early Tuesday morning. The parameter space remains similar to the past few discussions with MLCAPE around 1000- 1500 J/kg, deep layer shear 40-50 kts, and sweeping hodographs in the lower 2-3 km with 200+ m2/s2 SRH at onset. While lapse rates are rather modest and will offset much of the hail potenitial, damaging winds and a few tornadoes are possible within the line. The low level jet will help to maintain storms through the overnight, however with waning instability the expectation is for storms to begin to weaken later in the evening, especially east of I-35 late Monday night. Thanks to the progressive nature of the line of thunderstorms widespread hydro issues are not anticipated, however 1-1.5" QPF remains on track and should fall in a narrower time frame with these efficient rain producing storms. As such, a few areas with rivers already in or near flood could see quick rises and will need careful monitoring. A few showers and thunderstorms linger in eastern Iowa Tuesday morning as the system shifts east. The upper level low remains largely stationary through this and a few spotty showers or thunderstorms are possible in far northern Iowa on Tuesday afternoon with afternoon heating. By Wednesday this wobbling upper level low spins off another surface low. This will bring renewed chances for showers and thunderstorms. While instability and shear are sufficient, there is not a great forcing mechanism for convection so more organized severe storms appear less likely for now. The whole trough finally lifts east by Friday, however another wave may move across the area quickly on its heels Friday into Saturday. With such an active pattern model solutions diverge this late in the period so details on the timing and progression are fuzzy at this time. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 639 AM CDT Mon May 6 2024 MVFR stratus across southern Iowa will expand through the day. At the same time southeast winds will increase with gusts of 25+ kts through the afternoon. This evening strong to severe thunderstorms will sweep across the area late, impacting sites after 02z and lasting through at least 06z before starting to exit east toward the end of the period. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hagenhoff AVIATION...Hagenhoff