


Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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930 FXUS63 KDMX 181911 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 211 PM CDT Sat Oct 18 2025 .KEY MESSAGES... - Period of rain for most locations beginning northwest this afternoon and moving east overnight. - Gusty winds, sunny and cooler Sunday - Next strong system will impact the area Monday and Tuesday. && .DISCUSSION... Issued at 209 PM CDT Sat Oct 18 2025 Two areas of precipitation ongoing early this afternoon with widespread showers and thunderstorms from southern Illinois, central Missouri and into eastern Oklahoma. A more narrow area of precipitation is lagging behind the main system to the south with light rain over southwest Minnesota, southeast South Dakota and Nebraska. These systems are being forced by several factors and are in association with a couple strong PV anomalies that are showing up well in the water vapor imagery. The first is across north central OK with the other over southwest South Dakota though it does have short wave energy extending to the northeast. A couple of upper level jet maxes are also in vicinity of these anomalies. The lead 130 kt jet streak is centered over southeast Iowa and lifting northeast while the other 120 kt jet max is diving southeast through Wyoming and Montana. This will create a coupled jet structure leading to enhanced upper levels divergence and mid-level ascent over parts of central and eastern Iowa by this evening. That forcing will be enhanced by the approaching short wave energy and should lead to an expansion in precipitation as the energy of the southern and western systems combine. The Gulf moisture will remain secluded to the south meaning the precipitation into central Iowa will be reliant on any residual Pacific moisture that is tagging along with the system. While it may be a struggle to saturate enough for cloud bases below 4-6 kft, enough forcing and precipitation loading is expected for widespread precipitation that will impact areas from 1- 4 hours, with the greatest time periods over the east. Gusty north winds will develop today and will persist tonight into at least Sunday morning before diminishing begins in the afternoon as mixed layer winds lower with high pressure ridging arriving from the west. Sky conditions will clear out later tonight for a mostly sunny albeit cool Sunday with highs in the upper 50s to low 60s. Upper level default ridging will move across Iowa Sunday night into early Monday then will transition to a brief period of southwest flow Monday ahead of the next strong system. Strong mid-level theta-e advection will commence as this occurs while a connection to Gulf moisture is reestablished with high pressure moving east of the Mississippi River. Another strong PV anomaly arrives late Monday into Monday night along with low static stability. Precipitation chances will be contingent on available moisture. Given the amount of forcing and the reestablished moisture connection, the NBM and similar deterministic solutions are likely underdone on PoPs. Should enough moisture and saturation occur, thunderstorms could be possible given the low static stability and strong supporting forcing. An upper low will be established over northern Wisconsin by Tuesday morning leading to pronounced cyclonic flow over Iowa. Again, the NBM is likely struggling with this time period in several aspects. Given it is mid to late October, strong cyclonic flow very often results in a broad stratus field over the area. Strong and gusty northwest winds are likely, though the aforementioned stratus may limit those mixed layer depths. Several deterministic soundings do have low level instability and pending that instability depth and the strength of the inversion above this layer, showers may very well occur on Tuesday. The cyclonic/northwest flow will persist into Wednesday and most of Thursday before gradually relaxing late Thursday. High temperatures much of next week will be in the 50s and 60s and there will be some periods with freezing overnight lows, especially over the north. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1240 PM CDT Sat Oct 18 2025 An area of showers and perhaps isolated thunderstorms will move across central Iowa late this afternoon over the northwest and over the rest of the area overnight. Cigs will remain mainly VFR but local MVFR may occur. Vsby restrictions in rain may occur. The period of rain at sites will range from 2-4 hours. Gusty north winds will develop as well later this afternoon and overnight. Expect clearing late tonight and into Sunday. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Donavon AVIATION...Donavon