


Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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667 FXUS63 KDMX 220350 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1050 PM CDT Mon Jul 21 2025 ...Updated for the 06z Aviation Discussion... .KEY MESSAGES... - Thunderstorm potential and cloud debris preclude heat headlines for now. Should the warm front lift through the state, heat index values of 100-110 may occur by the afternoon. - Hot and humid Wednesday. - Thunderstorms possible again Wednesday night into Thursday. && .DISCUSSION... Issued at 258 PM CDT Mon Jul 21 2025 Surface warm front is just south of Iowa over far southern Nebraska and into northeast Kansas and southeast towards Kansas City. This boundary has been active all day with ongoing convection which has produced heavy rainfall but also has kept high temperatures in the low to mid 70s. On the north side of the boundary, widespread stratus/stratocumulus over the state. The elevated mixed layer (EML) remains stout over central Iowa though some elevated convective bubbling has occurred into central Iowa. A bit more established elevated convection is ongoing over southern Minnesota which a few fragments have reached far north central Iowa. The boundary will lift into Iowa tonight and on Tuesday. There remains a fair amount of uncertainty regarding the forecast going into Tuesday regarding convective trends. Upper ridging is building north into Tuesday otherwise the overall upper level flow does not support a strong push of the warm front northward and models tend to push these features too fast north. Therefore, expecting a slower warm front movement across central Iowa resulting in thunderstorm chances for at least part of the day. The potential convection and any convective debris will have an impact on high temperatures and also the heat indicies for Tuesday. If sunshine occurs and the boundary lifts north, heat index values will be in the 100 to 110 degree range south of the boundary. On the opposite end of the spectrum, there is also a low chance of widespread thunderstorms with the potential for heavy rain. Due to the uncertainties, will push headlines decisions off for now and it may need to be a short lead time headline. Will continue to advertise heat potential with the storm caveat. A localized severe storm with damaging winds and a few pockets of heavy rain are possible tonight into Tuesday. We have a greater confidence in heat on Wednesday as Iowa should be in the warm sector at that point with highs in the 90s and dewpoints in the 70s. This will place heat index values at 100 to 110 degrees. The upper level ridge will pass off to the with the upper flow becoming southwesterly Wednesday night into Thursday which will allow a boundary to drop back into the state. That boundary will be the focus for more storms and it tis the season for heavy rain potential should storms training along the boundary. Otherwise the parameters are in place for efficient rain processes. A typical July weekend looks on tap while the upper level ridge becomes re- established just west of the area by early next week. That may place Iowa in the northeast quadrant and possibly withing the MCS ring of fire zone. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1050 PM CDT Mon Jul 21 2025 High clouds continue to spread across the state from a storm system all the way in Kansas. Meanwhile, MVFR to IFR stratus is expanding across northeast Iowa. This will impact sites KMCW/KALO/KFOD through Tuesday morning, and further reduction to LIFR is possible. At the same time, patchy light fog development is becoming more likely and have included mentions at KMCW/KALO. Clouds diminish late Tuesday morning, along with increasing south winds. Isolated thunderstorms are also possible late afternoon into the evening, however there is little consistency in model data regarding placement so have kept from TAFs at this time. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Donavon AVIATION...Hagenhoff