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Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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313 FXUS63 KDMX 022055 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 355 PM CDT Tue Jul 2 2024 .KEY MESSAGES... - Threat for severe and flash flooding remains through late afternoon into mid evening. - Quiet but warm on Wednesday - Chances for showers and storms returns on late Wednesday night into Friday. Severe threat appears limited but outdoor activities may be impacted from time to time. && .DISCUSSION... Issued at 354 PM CDT Tue Jul 2 2024 Convection has maintained for much of the morning into early afternoon with a recent uptick as peak heating approaches. Much of the forecast area was overcast through late morning but the past few hours has seen some sunshine across the south with an associated surge in temperatures and dewpoints. MUCAPES of 2500 J/KG have developed into southern Iowa with bulk shear values improving to over 50kts across much of central Iowa. Soundings are also very moist and PWATs have increased to over 2" in the south central - a hydro discussion follows below. Surface flow remains modest at this time although somewhat stronger where mixing has been more robust in the southeast. The severe potential remains decent this afternoon into the early evening although lapse rates are not overly strong which may be limiting updrafts at this point. There is a warm front extending near I80 which may provide some focus for additional strengthening and may be an area for the better threat of severe storms. At this point, damaging wind gusts or a tornado may occur as the system continues to organize with hail remaining an outside threat. The storms pass to the east this evening with drier air arriving overnight as weak surface ridging builds toward the Missouri River Valley in the west. Quiet conditions are forecast into Wednesday with pleasant weather although it will be warm with the drier airmass warming nicely by afternoon. Warm advection begins to increase into Wednesday evening and the overnight ahead of the next shortwave as convection develops across the Plains during peak heating Wednesday afternoon and rides the nose of the low level jet across Nebraska toward southwest Iowa. The bulk of models output suggests this clips the southern counties into Thursday morning. Additional convection is expected near northwest towards north central Iowa as well associated with the upper system passing through South Dakota. This upper low slows to a crawl across southern Minnesota into northern Iowa Thursday night into Friday. This is likley to bring a prolonged period of moderate to locally heavy rainfall in the vicinity of northern Iowa through this time and will need to be watched closely given the very wet conditions that exist in this area. Northwest upper flow then remains in place into next week with several systems sliding into the Midwest. Another system approaches by the end of the weekend with another threat of moderate to heavy rainfall, particularly from the Euro solutions which are slowly with the progress of the system. This continues the threat of renewed river rises or flooding should it come to fruition. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 110 PM CDT Tue Jul 2 2024 Widespread hazards occur this afternoon into tonight with areas of MVFR to IFR conditions, particularly in and near convection. Surface winds from the south to southeast are expected but may approach or exceed 50kts near stronger storms. The convection is expected to depart by late evening with improving conditions late tonight into Wendesday morning with VFR categories returning. Surface winds also become west to northwest late tonight into Wednesday morning. && .HYDROLOGY... Issued at 354 PM CDT Tue Jul 2 2024 Threat of heavy rainfall and potential flash flooding continues across central into southeast Iowa with PWATS remaining at to slightly above 2". Morning convection helped to saturate areas of central into southern Iowa with rainfall of 1-3" in many locations. The potential for some training during the late afternoon may be sufficient for localized flash flooding and the Flood Watch remains into the evening for much of the area. The current river forecasts, which includes 48 hrs of forecast precipitation, do slow the fall along the West Fork Des Moines river. Rises are forecast across most other basins including the East Fork Des Moines, Des Moines, Winnebago, Shell Rock, Cedar and Iowa River basins including a return to Minor Flood stage at Mason City, Shell Rock, Cedar Falls and Waterloo, Stratford and Des Moines at SE 6th. This may also bring additional impacts to these areas including the Saylorville Lake storage, which is currently forecast to reach 882 ft by the Corps of Engineers. && .DMX WATCHES/WARNINGS/ADVISORIES... Flood Watch until 1 AM CDT Wednesday for IAZ017-025>028- 033>039-044>050-057>062-070>075-081>086-092>097. && $$ DISCUSSION...Cogil AVIATION...Cogil HYDROLOGY...Cogil