textproduct: Des Moines

KEY MESSAGES

- Showers and isolated thunderstorms will continue through this evening. While gusty winds to around 40 mph are possible, the risk for severe weather is low.

- Generally dry with seasonal temperatures on Saturday, 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 on Saturday night and Sunday.

SHORT TERM /THROUGH SUNDAY/

Issued at 213 PM CDT Fri Jun 19 2026

This afternoon through Saturday...

An upper shortwave trough continues to slide across MN into WI. In response, low level flow shifted southwesterly which has advected only very modest amounts of moisture ahead of the system. Even so, synoptic scale ascent and low/mid level moisture convergence has led to the development of scattered/numerous showers and isolated thunderstorms over mainly central and northern Iowa. Instability is generally weak, with less than 500 J/Kg of MLCAPE, which should greatly reduce the threat for severe weather, even with an impressive deep layer shear profile. With cloud bases fairly high /5-8k feet/ the inverted V type profile will result in a threat for gusty winds, perhaps as high as 40 mph through the evening hours. Rainfall amounts will also be modest, generally a tenth to quarter inch. As the upper system translates ewd, subsidence on the backside and the loss of daytime heating will bring an end to precip from northwest to southeast, with dry and cool conditions overnight.

On Saturday, sfc high pressure will be in place from the Dakotas sewd across Iowa and into IL, with a sfc low developing in the lee of the Rockies during the afternoon. Good model agreement that conditions will remain dry during the daytime hours as the deeper moisture will reside well south and west of the area. Besides some increase in clouds in the PM, it should actually be a rather pleasant day with highs again in the upper 70s to lower 80s.

LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/

Issued at 213 PM CDT Fri Jun 19 2026

Saturday night into Sunday...

Heavy rainfall and possible flooding is the primary concern in this period. A low amplitude shortwave will track across the central Plains Saturday night and into the Mississippi Valley on Sunday. This will result in the development of a moderate to strong LLJ after 06Z which will slide east and veer across srn Iowa. A significant surge of low level moisture/theta-E is expected with plume of +12C 850mb dewpoints and PWATs from 1-5-2.0" overspreading at least the southern half of Iowa. These values are generally 1-2 standard deviations above climatology. While there is generally good global and CAM model consensus of an axis of heavy QPF developing from one or more MCS's, there is uncertainty on exactly where the low level baroclinic zone/front will reside which will have a major influence on the development and evolution of the resulting convection.

Looking at the various QPF solutions, the global ensembles/NBM continue to indicate the heaviest rainfall over the southern half of Iowa. The latest NBM run is indicating about a 50-70% chance of exceeding 2" of rainfall from generally I-80 and about a 5-15% chance of exceeding 5". Some of the longer range CAM solutions which are now in the window, along with the REFS is highlighting generally the same corridor across southern and southwestern Iowa. Not surprising, the CAMS are showing a higher ceiling of QPF (in some cases over 6-7" in smaller basins) but also more variability in what areas get hit the hardest. Finally, the Extreme Forecast Index (EFI) and various AI guidance tools are zoning in on the same area of southern Iowa. In term of flash Flood Guidance, 6 hour FFG values are suggesting about 3-4" of rainfall would be needed to cause issues. With a few days of relative dryness, and active crops this time of year, would generally lean on the higher side of this guidance, if not more. The WPC Excessive Rain Outlook (ERO) was mostly unchanged, and has Moderate (Level 3 of 4) mostly across portions of NE, MO, KS, although it does scrape far SW IA. The Slight Risk (Level 2) does impact much of southern/central IA. All things considered, decided to hold off on a Flood Watch at this time, mainly due to uncertainty in QPF amounts and location. See more information on river flooding in the Hydro section below.

Not to be left out, there is also a Marginal Risk (Level 1 of 5) on both Day 2 and 3 (focus is Saturday night and Sunday). Instability/CAPE is likely to be rather meager, and mid-level lapse rates will generally be moist adiabatic, so right now feel the severe threat is quite low, but something worth monitoring.

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.