textproduct: Des Moines

KEY MESSAGES

- Showers and thunderstorms are moving out of the area and will continue to move out through the morning.

- Areas of patchy fog are possible before sunrise, mainly north of I-80.

- More autumnal conditions expected today with cooler temperatures and drizzle throughout the day with the potential for more widespread showers and storms overnight into Monday.

- Cool temperatures and moist weather persist into Monday, with drier conditions expected Tuesday and Wednesday.

SHORT TERM /THROUGH MONDAY/

Issued at 253 AM CDT Sun Sep 20 2026

Showers and thunderstorms are ongoing across portions of central and eastern Iowa. Areas to the north of the showers and storms are currently experiencing patchy fog per the nighttime microphysics satellite band as a moist airmass remains over the region. The showers and storms are being fueled by the Low Level Jet (LLJ) which will both weaken and take on a less favorable orientation closer to sunrise. At the same time, the expansive high pressure that has been pancaked over the southern US has begun to break down, leading to meager flow at 850mb, which means low-level moisture transport into the region is going to be substantially reduced. Furthermore, the breaking down of this high combined with a weak mid-level low forming over the western plains means mid-level moisture transport will be favored better south of Iowa. While this doesn't lead to a completely dry forecast for the next couple of days, it does lead to a day with lowered concerns for heavy rainfall once our current showers and storms exit the area. As for rainfall amounts through the morning, with some of the heavier bands it looks like 1-2 inches of rainfall is expected with a few pockets closer to 3 inches. The axis of heaviest rainfall with this activity remains to our east.

Once the ongoing showers and storms exit the area, much more autumnal conditions are expected. Behind a cold front which will help usher out the remaining showers, northerly flow will persist as high pressure builds over Ontario. This leads to highs generally in the 60s across much of the state with areas in far southern Iowa approaching 70. While a moist airmass is already in place, northeasterly moisture transport in the low levels will help keep much of the atmosphere just above the surface saturated enough for low stratus clouds and drizzle. Sounding profiles show a saturated airmass up to about 800mb across the state. Some soundings show there is very minimal CAPE, leading to the potential for a proper shower or two, but values are low enough (<500 J/kg) that widespread convection is not expected.

While drizzle will persist through the day, conditions for it remain favorable into the overnight before another disturbance moves into the area. A weak low over the Nebraska panhandle will develop. Weak Theta-E advection will allow for more widespread showers and thunderstorms to be kicked off, mainly in western and northwestern Iowa overnight into Monday morning. Weak shear (25kts or less) and limited instability (<500J/kg) lead to the only concern being a few rumbles of thunder with stronger storms.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/

Issued at 255 PM CDT Sat Sep 19 2026

The cooler, fall-like conditions continue into Monday and early next week with highs generally only reaching the upper 50s to near 60 both Monday and Tuesday. Our light rain generally continues into Monday, this time with a bit more synoptic support as a an upper level low meanders into Iowa trudging along in the zonal upper level flow. This low hangs out overhead into Tuesday, but begins to bring drier air into the state. Should this pan out as the models suggest, we should finally see a few dry days Tuesday and Wednesday of next week. However, rain chances do look to return to at least western Iowa on Thursday. More details on that in the coming days.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1241 PM CDT Sun Sep 20 2026

MVFR and IFR conditions will be common over the period. A brief reprieve is expected to occur at KMCW and KALO, but additional stratus is on its way from the northeast. Have timed its arrival. Rain and fog will again be likely overnight, mainly in northern Iowa. IFR and LIFR cigs and occasionally vsbys will accompany rain by morning. Have hedged more aggressively given trends the past few days with lingering fog/stratus.

DMX WATCHES/WARNINGS/ADVISORIES

None.