


Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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103 FXUS63 KDMX 281943 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 243 PM CDT Sat Jun 28 2025 .KEY MESSAGES... - Shower and thunderstorms likely (60-80%) Sunday. A few storms may become strong-severe capable of damaging winds and heavy rain - A few degrees cooler air mass and dry conditions for the first half of the week - More storm chances (20-40%) and and seasonally warm temperatures (similar to today) return for Wednesday into the holiday week (not washouts) && .DISCUSSION... Issued at 243 PM CDT Sat Jun 28 2025 The one-day reprieve of higher humidity yesterday is a distant memory as the high plains surface low advects a low-mid 70F surface dew point air mass within the warm sector across the state today. Aloft, the H3 jet core remains confined to northern Minnesota, with mid-level shortwave energy riding thru it`s southern periphery. At the surface, the warm front resides in a similar area, extending back to the the high plains sfc low. As such, the convective focus overnight will remain north and northwest closer to better theta-e advection and forcing. Similar to last night, all of the CAMs develop a MCS across the Dakotas, sliding southeast in some form on Sunday morning. As typical in relatively light mid/upper-flow situations, models underachieve consensus regarding MCS sustainability and timing. This time is no different. The HRRR is the most aggressive in maintaining it the longest - well into Sunday morning across northern & central portions of the CWA, which if it would occur, would have impact on where and when/where storms initiate on Sunday afternoon and evening. Alternatively, the majority of the other model output weakens/dissipates the activity before redeveloping storms across southern Iowa along a south moving "cool" front in afternoon/evening. Although best deep-layer shear lags the boundary near the jet, values of 25-30 knots should be sufficient for the potential for a few strong/severe storms once they do develop. Although initial updrafts may present a brief hail threat, downdraft CAPE values in excess 1000 j/kg (due to mid- level dry air) points to damaging winds as the primary threat, especially once convection congeals. Also, 0-3 CAPE values remain above 150 j/kg which suggest at least the potential for a few funnel clouds with LCLs near 1 km. However tornadoes are not expected given the environment. Heavy rain will be a good possibility as well, with precipitable water values progd to be 1.5-2" statewide. More details can be found in the Hydrology section below. Storms should depart into Missouri Sunday night giving way to slightly cooler and dry conditions for Monday & Tuesday. The progressive pattern returns by mid-week which will bring storm chances (20-40%) and above normal temperatures along with it for the latter half of the week and into the holiday weekend. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1237 PM CDT Sat Jun 28 2025 VFR conditions expected to prevail at area terminals through the period as south winds of 5-10 knots persist across the state. Thunderstorm chances will return to some terminals just beyond this TAF cycle and will likely need to be included in the next update or two. && .HYDROLOGY... Issued at 243 PM CDT Sat Jun 28 2025 Soil moisture remains high though across much of the CWA owing to last week`s heavy rainfall. NASA SPoRT soil moisture percentiles for the top 40 cm of the soil (usually considered for river forecasting purposes) remain above normal north of US 30, while generally more normal south. Additional rainfall is forecast Sunday into Sunday night, however. At this point, the best chances for heaviest rainfall appears to be with most likely location of more organized storms in the central and south - generally away from the aforementioned area of above normal soil moistures (in the north). Latest tools suggest this additional rainfall will have a minimal impact on existing river trends especially at those locations where levels are or will be running high. The rainfall may add minor amounts to the crests or slow falls. Although not a great chance given that southern Iowa is less flash flood prone, localized flash flooding would be a possibility over urban areas or if storms are able to move parallel to the boundary. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hahn AVIATION...Hahn HYDROLOGY...Hahn