


Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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022 FXUS63 KDMX 270535 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1235 AM CDT Fri Jun 27 2025 ...Updated for the 06z Aviation Discussion... .KEY MESSAGES... - Thunderstorms tracking east-southeastward through the state this afternoon into evening. Damaging winds and heavy rain are the main threats, though a tornado is possible mainly in northeastern Iowa. - Thunderstorm activity moves out late tonight with dry conditions expected on Friday. - Warm temperatures continue this weekend and next week with additional rain and thunderstorm chances through the second half of the weekend and at times next week. && .DISCUSSION... Issued at 109 PM CDT Thu Jun 26 2025 Focus is on the developing activity this afternoon into evening. Midday surface analysis has the warm front hanging out over northern Iowa near the IA/MN border, continuing to become better defined with time. The surface low is ejecting out of eastern SD/NW IA/SE MN and will track across far northern IA/southern MN with time through the afternoon and evening hours. Adjacent to the low is a cool front extending southward through eastern NE and beyond. These features will all be drivers of our showers and storms through the afternoon and evening with storms having already been bubbling into midday over portions of west central Iowa with some showers ongoing in portions of northern Iowa and mostly clear skies to the east of the bubbling storms/showers. The warm sector south and east of the two boundaries is directly over the state where temperatures have warmed into the 80s where precipitation is not ongoing, with very moist and humid conditions as dew points are near-widespread in the 70s. This has translated to instability values (MLCAPE) of 1000-2500 J/kg over the area as of midday with soundings showing robust ECAPE values as we get into later this afternoon as well. Wind shear over much of central to southern Iowa remains weaker, but over north central into far northern Iowa bulk wind shear is much better, 30-40 knots. The farther north is also where LCLs are lowest and is generally where the better tornado environment exists, but is also highly conditional with rain ongoing over that same environment as of midday. The triple point between the fronts and surface low will remain a foci for any potential more discrete storms where the tornado potential would be highest with initial storm development given the low level CAPE and stretching potential in that vicinity. The caveat is how this environment recovers given the activity ongoing around midday. Further south along the front, generally expecting more linear convection with more broken storms the farthest south you go given the very weak shear. For portions of central into northern Iowa, storms along the line may pose a damaging wind threat, though will monitor for any potential spin ups as well the further north you go where the more favorable (though conditional) tornado environment exists. Not really expecting much in the way of hail given the overall environment, but some small, to maybe isolated marginally severe hail could be possible if a more robust storm is able to develop. Overall, storms are expected to develop in western Iowa and track east to southeast with time through the area, but CAMs are not necessarily capturing current trends well so confidence is decreased in how convection plays out through the afternoon. Besides the conditional tornado threat north, and wind threat with the line, will also continue to monitor our hydro situation as the environment remains favorable for efficient rainfall, as it has the last several days. Continue to expect 1-3" with localized higher 3"+ amounts, though again midday activity may affect how the rest of the afternoon/evening progress. By late tonight, storms will have cleared the area with a surface ridge moving over on Friday. This will bring a much-needed quiet day in terms of weather back to the area. Waves moving through our otherwise upper zonal flow will bring precipitation chances back to the forecast at times later in the weekend (Saturday night into Sunday) and again at times next week. Will continue to monitor the threat for any severe weather with uncertainty remaining on where storms may track into Sunday. Otherwise, temperatures remain warm in the 80s to 90s. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1230 AM CDT Fri Jun 27 2025 As rain moves off to the east, the main concern for the rest of tonight will be low clouds and fog potential. IFR ceilings should be quickly entering MCW/FOD, and will eventually reach ALO/DMX within a few hours. Models are not generally suggesting that any fog less than 1SM will occur, but there is a 20-40% chance for MVFR visibilities especially at MCW/DMX and lesser, but non-zero chances at all other terminals. Any fog is expected to lift and scatter out around 11z to 12z, and ceilings are expected to be slower to lift and scatter, but eventually should by mid-to-late morning with VFR conditions expected at all terminals for the rest of the period. The low clouds moving in will occur following a cold front, so expect wind direction to shift to west/northwest within the next few hours. Speeds should remain below 10 kt through the period. && .HYDROLOGY... Issued at 109 PM CDT Thu Jun 26 2025 One final round of heavy rainfall and possible flash flooding is expected today before at least a short break in precipitation on Friday. However, as water is routed through the basins and river systems, river flooding concerns will persist well into next week. A broken line of storms is expected to develop along a cold front this afternoon and move from west to east across much of the CWA into this evening. As in past days, robust moisture content, high freezing levels and ample instability will again lead to efficient rain rates. However, this line of storms should be progressive, moving eastward around 30 mph. Many of the global models and CAMs are indicating widespread 1-2" rainfall amounts, but the progressive nature of the storms should prevent rainfall amounts from getting out of hand. The 26/12Z HREF 24hr PMM valid from 12z Thu to 12z Fri shows this nicely, with only sporadic amounts over 3" indicated. Flash flooding is a concern with the rainfall this afternoon into tonight however for now we have opted to not issue a flood watch for flash flooding because we think the current flash flood guidance (FFG) across our CWA is a little too low. Historically the FFG starts having a tougher time capturing reality in our region during this time of year, due to ag crops taking off in their growth. That issue is admittedly tempered with the recent heavy rainfall, however we still think the FFG is running a little low. Although some isolated flash flooding is possible, at this time we do not believe the flash flooding will become scattered (i.e., rise to the level of needing a watch). If the storms this afternoon and evening do more training than we presently expect, though, then the flash flood risk would increase. In terms of river flooding, we have returned to 24 hrs of QPF in our river forecasts. The river forecast updates today do not have any significant changes aside from some ups and downs within the same category. The main reasons for the forecast changes are mainly QPE vs QPF changes from last night was well as shifting of the QPF locations for today. It should also be noted that for many locations where action stage is forecast, those forecast crests are near flood stage. Due to increased confidence in the river flooding occurring, we have issued river flood watches for those locations where river flooding is forecast. The larger streams of most concern presently include the Cedar, Winnebago and Raccoon Rivers. For some locations, the elevated stages and river flooding is expected to continue well into next week. Additional rainfall is in the forecast for the Sunday timeframe. This rainfall may be locally heavy and may impact area rivers. Depending on the location of the rainfall, this rainfall has the potential to result in quicker rises, slightly higher crests or slower falls after the crests. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...05 AVIATION...DLH HYDROLOGY...05/Zogg