textproduct: Des Moines

KEY MESSAGES

- Storms through today may lead to continued flooding or flash flooding concerns, especially in areas impacted by multiple rounds of heavy rainfall.

- Enhanced risk for severe weather in western Iowa, and Slight Risk for much of the state later this afternoon to evening. All hazards are possible with this activity.

- Uncertainty remains with the forecast into the holiday weekend, but hot and humid conditions persist with thunderstorm chances at times.

SHORT TERM /THROUGH TONIGHT/

Issued at 401 AM CDT Fri Jul 3 2026

Very active weather conditions have become more common across much of Iowa as of last night into early this morning, with radar indicating scattered showers and thunderstorms over central into northern Iowa. While the overall concern for severe weather lowered over the last few hours or so, the main focus as of late shifted significantly over to flooding, as storms have repeatedly developed just south and near the I-80 corridor, before slowly lifting north/northeast. Rainfall estimates over Polk to Black Hawk County reached values generally around 2 inches, with localized amounts in the 4-6 inch range. Hence the issuance of Flash Flood Warnings that are in effect until 7am for Polk county and portions of Jasper county. Despite the concern for the rain that has already fallen over these areas, there remains the potential for additional heavy rain as continued scattered showers and storms are showing development over Madison and Warren counties that are expected to lift into these already flooding areas, further enhancing the risk for rather significant flooding risks over cities and towns, as well as continued rises in rivers. We are also monitoring areas over north-central Iowa for potential flooding, as rainfall amounts so far are pushing over 2.5 to 3 inches over northern Webster and Hamilton counties. Yet another area of concern is the line of showers and thunderstorms in the form of an MCS that is moving over western Iowa, which per radar trends and latest CAM runs have this complex tracking southeast into the forecast area within the hour and tracking across the state through the greater majority of the morning. With this MCS will come returning chances for severe weather, with the environment ahead of this feature characterized by 3000-4000 J/kg, while the effective shear of 30 knots in western Iowa decreases with eastern extent. The main hazards of concern would be damaging winds and small hail as it enters the western part of the forecast area, transitioning to more of an additional hydro threat given high PWATS and warm cloud depths that remain overhead. By mid to late morning, this MCS should have weakened considerably, with model guidance generally showing it exiting the area somewhere after 10a-noon.

Temperatures given the presence of showers and storms through much of the morning, as well as lingering clouds will likely lead to some lowering of highs later on today, though in terms of heat headlines, no changes were made over the far southern portion of the forecast where the least of affects are anticipated by the activity through the day, where heat indices near 100 degrees are most likely. While dry conditions are expected over the afternoon across Central Iowa, the boundary over north/north central Iowa is expected to see development once again of showers and thunderstorms after roughly 4- 6 pm, and increasing in coverage through the evening. This activity is anticipated to dive southeast with time, into an environment that will have more than favorable instability overhead, while shear of less 30 knots may lead to more of a messy storm environment. The primary severe hazards again would be damaging winds and large hail, given DCAPE values over 1000 J/kg and lapse rates around 7 C/km. An Enhanced Risk per SPC remains over western Iowa, with a Slight Risk across the greater majority of Iowa. Additional heavy rain will be of high concern as well, especially in the areas mentioned above that have already experienced flooding, with a Slight Risk for excessive rainfall from the WPC.

LONG TERM /SATURDAY THROUGH THURSDAY/

Issued at 407 PM CDT Thu Jul 2 2026

The synoptic pattern begins to transition to a more zonal flow pattern through the day Friday and into the weekend. This generally keeps the warm and moist conditions going through the weekend, although some reprieve may be on the horizon. Models are currently depicting a shortwave passing through the state Friday night into Saturday morning, bringing another MCS across Iowa. This system will likely ride along the mesoscale boundary/instability gradient (similar to tonight's), which will likely be farther south in the state. As this occurs, damaging winds and heavy rainfall will accompany it, again bringing severe weather and flash flood concerns Friday night into the morning of Independence Day. However, with the less persistent synoptic pattern, conditions seem to stabilize at least through the day on Saturday. The boundary will be pushed either into southern Iowa or northern Missouri, acting as the focal point for redevelopment on the afternoon and evening of Independence Day. Therefore, the southerly extent of the Friday night into Saturday morning storms may be able to spare much of Iowa from storm chances later in the day Saturday. This would also lead to slightly cooler conditions, albeit still warm in the upper 80s. There is still a lot to happen between now and then, so stay tuned to the forecast for the latest on the Independence Day forecast! Warm and humid conditions then persist into the end of the weekend and early next week, although still not to the extremes of the beginning of this week.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1252 AM CDT Fri Jul 3 2026

Shower and thunderstorm coverage has increased through the evening and will generally continue at or near much of the terminals at least through much of Friday morning. While highest confidence on this activity is over the KDSM, KFOD, and KALO terminals given current radar trends, timing and intensity of further activity later in the period, particularly late in the morning through the latter portions of the current period will need to be further assessed and refined at all TAF sites, with amendments likely. Periods of low ceilings falling below 3kft and lowered visibilities due to heavy rainfall are likely, leading to periods of MVFR/IFR. Guidance suggested some spotty LLWS as well this morning, but with this limited coverage have left out of this forecast.

HYDROLOGY

Issued at 455 AM CDT Fri Jul 3 2026

As mentioned in the short term discussion above, Flash Flood Warnings are in effect for all of Polk county and portions of northern Jasper and southern Story counties given QPE estimates in the 4-6 inch range that have fallen, while additional rainfall continues to fall as of this writing. QPF amounts over an inch are likely over these and surrounding areas through the morning as this scattered shower and storm activity slowly lifts north and east ahead of a large storm complex just west of I-35. The current county- based Flood Watch remains generally along and north of I-80 until 10am for this anticipated morning activity, with expectations of additional flooding, especially where storms have and are currently passing through. There is an increasing potential for an additional Flood Watch issuance later today, likely over similar areas as showers and storms develop over north central Iowa late this afternoon into the evening where additional 1-2 inches of rain are expected.

Regarding river flooding, a Flood Warning is in effect for Fourmile Creek at DFMI4, while Flood Watches are in effect at the Cedar River at Cedar Falls (CEDI4) and Waterloo (ALOI4), as well as at Black Hawk Creek at Hudson (HUDI4). Given the expected rainfall throughout the rest of the day, it is expected that runoff from additional heavy rainfall will lead to continued river rises and the potential for an increasing number of river sites to reach into action stage or above, with impacts holding on into the upcoming weekend.

DMX WATCHES/WARNINGS/ADVISORIES

Flood Watch until 10 AM CDT this morning for IAZ004>007- 015>017-023>028-033>039-044>050-057>062. Extreme Heat Warning until 10 PM CDT this evening for IAZ084>086-092>097.