


Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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184 FXUS63 KDMX 140723 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 223 AM CDT Tue Oct 14 2025 .KEY MESSAGES... - Shower chances increase from southwest to northeast today into tonight, then persist mainly north into Wednesday. - Warmer weather returns in the latter half of the week, with highs Thursday and Friday in the mid-70s to lower 80s. - A few showers and storms possible Friday and Saturday. && .UPDATE... Issued at 223 AM CDT Tue Oct 14 2025 Light radar echoes are being observed as moisture advection aloft attempts to promote showers early this morning, but stubborn low-level dry layer has proven too much to overcome so far. Forecast soundings indicate it will take some time yet, with light rain beginning in our west/northwest later this morning and pivoting across about the northern half of the state by tonight. Have adjusted POPs to delay onset accordingly and capped at likelies (60-70%) overnight in deference to concerns about the coverage of measurable precipitation. Still, we should see at least scattered if not widespread sprinkles/light showers tonight, again, mainly north, before they gradually fade out on Wednesday and Wednesday night. Limited instability may support a few thunderstorms at times the next couple of days, but severe weather is not expected. && .DISCUSSION... Issued at 229 PM CDT Mon Oct 13 2025 Very slow moving surface boundary is just to the south and east of the area this afternoon. Dew points in the upper 50s and 60s are pooled along the boundary. Ridge of high pressure is moving in behind this boundary and it has brought much drier air into central and northwest Iowa with dew point values dropping into the 30s this afternoon. A portion of the dew point drop this afternoon can be attributed to diurnal mixing so there should be a modest bounce back up towards sunset. Theta-e advection will commence overnight into Tuesday and will begin to overrun the surface ridge as winds aloft above 4 kft turn southerly. This will lead to descending cloud bases overnight and Tuesday with increasing chances for showers from south to north during this period. Continued the trend of delaying the onset of precipitation due to the saturation process and the dry layer beneath cloud bases. The precipitation chances will become more focused over the northern third of Iowa Tuesday night and in vicinity of the theta-e advection focus. Light rain may linger into Tuesday evening in central and southern Iowa as some saturation remains before some dry air entrainment arrives. Thunderstorm chances through this period remain quite low. Mid-level lapse rates remain below 6 C/km much of the period and while very low MUCAPEs may develop with ideal particle lift points, the vertical extent of lift is quite shallow and likely will not result in lightning. This process is already occurring over eastern Kansas and Oklahoma where the latest lightning data is not returning anything. Clouds will keep conditions cool over northern Iowa while highs over the south will be dependent if some sunshine can occur which despite the arrival of the drier air, is not a certainty. Upper level ridging will become reestablished on Wednesday then a transition to steeper southwest flow to end the work week as the ridge moves east. This will result in seasonably warm conditions return on Wednesday with highs back into the mid to upper 70s for the southwest half of Iowa. High may reach the 80s in some areas on Thursday then slightly cooler on Friday. The moisture return profiles for both low level Gulf moisture advection and the combined Gulf and Pacific mid-level moisture contribution is more favorable with the enhances southwest flow. This environment will be more favorable for a few thunderstorms as the main boundary and short wave pass through the area. At this point though, any activity will likely be sub-severe. A long wave trough and upper northwest flow follows for the weekend. At this point, the NBM forecast for Sunday looks a bit on the warm side unless extreme mixing can occur, which I should note is possible. Gusty winds in this type of setup would seem likely as well. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1045 PM CDT Mon Oct 13 2025 VFR tonight with increasing clouds. Winds shifting to the northeast overnight. As we get deeper into Tuesday the winds will shift to the east. The focus of the forecast continues to be on the rain showers moving in on Tuesday. Still looking more isolated to maybe for the northern Iowa terminals scattered. So opted to stick with PROB30 for now. Late morning to early evening looks to be the best chance at most of the terminals (OTM seems least likely to see rain). Late evening into tomorrow night seems more focused over northern Iowa with the best chances at the FOD and MCW terminals. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Lee DISCUSSION...Donavon AVIATION...NC