textproduct: Des Moines

KEY MESSAGES

- Generally dry with seasonal temperatures today, with highs in the upper 70s to lower 80s.

- Widespread showers and thunderstorms (60-100% chance) with a threat for heavy rainfall is forecast Saturday night into Sunday. There is potential for both flash and river flooding, mainly in the southern half of Iowa. There is also a low risk of severe weather (Level 1 of 5) across southern Iowa through Sunday.

- Cool temperatures to follow with highs in the 70s.

SHORT TERM /THROUGH SUNDAY/

Issued at 306 AM CDT Sat Jun 20 2026

A pool of moisture wasn't far from the state this morning and was evidenced by overnight convection in Kansas and Nebraska. Lee cyclogenesis is expected to begin in response to an incoming shortwave riding the northwest flow. The resultant cyclone will intensify the LLJ throughout the day end evening today, increasing clouds this afternoon. Highs will be near 80 again today with rain and storms firing on the theta-e axis in southwest Iowa late this afternoon.

The potential for heavy rain exists tonight, mainly for far southern Iowa, although the heaviest rainfall axis still appears to be in Missouri. Have held off on a Flood Watch this shift. Current expectation is for the heaviest thunderstorm activity to just miss the DMX CWA to the south and west, primarily due to the storm and cold pool propagation. During the daytime, storms that form on the theta-e gradient will have 50kts of deep layer shear to work with, along with 1500 J/kg of MUCAPE. This setup favors supercells, and the bunkers right motion points south-southeast in Nebraska. This means that storms will migrate further into the instability axis and eat into it during the day. Some 00z CAM guidance even had training supercells along that axis (hence the QPF max in Nebraska), eventually congealing into an MCS once the nocturnal inversion sets up. By this point, the surface warm front will be in northern Missouri with the nose of the LLJ into southern Iowa. Rain is certain (90-100%) in Iowa tonight, especially in southern Iowa, but the residence time of the MCS will be short-lived. Corfidi vectors will assume a similar direction as the right mover motion in the day, dropping the heaviest nighttime rain south of the state. Southern Iowa can still expect widespread amounts between 1 and 2 inches, maintaining the low probability (5-15%) of exceeding 5". The Marginal Risk for severe weather roughly outlines the MUCAPE axis, pushed even more south for the D2 (Sunday) Marginal, which is tucked just south of the state line. Isolated damaging winds are the main threat, with hail the secondary.

The threat for flooding impacts remains is reflected well in the hydrology discussion below. Soil moistures in southern Iowa have dried to around 30-40% with FFG over 3". Paired with maturing crops and the geographic tolerance to flooding in southern Iowa, flash flooding would require exceeding guidance. Ponding will be possible in poor drainage areas.

Rain focuses more to the south Sunday, with trends favoring a slowed arrival of the next shortwave. As a result, PoPs in northern Iowa were reduced from NBM guidance. Highs on Sunday will hover near 70 degrees.

LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/

Issued at 213 PM CDT Fri Jun 19 2026

After the precipitation moves out late Sunday into Sunday night, a westerly zonal flow pattern is expected Monday. A broad upper trough is then expected to develop over the central CONUS from mid to late week, resulting in a more northwesterly flow pattern. The result of this will be a "coolish" temperature pattern with H8 temps generally in the +8C to +15C resulting in highs in the 70s to lower 80s. In terms of precipitation, NW flow patterns tend to feature fast moving upper features moving through the area, and this looks no different. Timing of individual rainfall events is generally low confidence, and these events will generally not be all day rainers.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1124 PM CDT Fri Jun 19 2026

VFR conditions are expected to prevail through Saturday afternoon. Clouds will continue to clear out over the next couple of hours with light winds across Iowa. Areas of patchy fog will be possible in western Iowa; however, impacts are expected to be minimal at terminal sites. Most of Saturday will be quiet with clear skies but as we near the end of this TAF period, clouds will increase with widespread showers/storms.

HYDROLOGY

Issued at 233 PM CDT Fri Jun 19 2026

See the main portion of the discussion for the meteorology of the event. In terms of river flooding, the latest guidance from the National Water Model, HEFS, and contingency forecasts, suggest that river flooding could become an issue on Sunday and beyond if the expected QPF materializes. However, this will ultimately depend on the magnitude and location of QPF, which remains uncertain at this time. Assuming a higher end QPF scenario (highest 10% of QPF members) many rivers along and south of US 30 may reach action to minor flooding, with moderate or higher flooding possible. Again, this would assume widespread QPF amounts of 4-5" certainly possible, but not a guarantee at this time. In future model cycles, we'll fine tune the axes and magnitude of the highest QPF.

DMX WATCHES/WARNINGS/ADVISORIES

None.