textproduct: Des Moines

KEY MESSAGES

- Quiet and sunny conditions continue today, with warmer temperatures near 90 expected Wednesday.

- Thunderstorm chances return Wednesday afternoon through Thursday morning. A few storms may producing damaging winds and heavy rainfall over north central Iowa.

- Additional rainfall around 1 to 2 inches Wednesday through Thursday may slow or worsen ongoing improvement along area rivers.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 252 PM CDT Tue Jul 7 2026

Today's conditions over Iowa show a similar picture to this time yesterday, with cumulus clouds speckling sunny skies. Winds are light and generally out of the south and temperatures have warmed into the 80s. Heat index values are a bit higher in the upper 80s and low 90s thanks to the moist upper 60 to 70 dewpoints and little cooling from the wind. Surface high pressure is to be thanked for another day of nice conditions, but will be steadily departing the area tonight into Wednesday. Return flow on the backside of the high pressure will bring the warm, moist low to mid-level moisture stream back into Iowa. This will first result in warmer temperatures on Wednesday as highs climb into the upper 80s to low 90s for some. This moist air will also bring some increased cloudiness and rain/thunderstorm chances to Iowa Wednesday through Friday.

The first of this rain and cloudiness could come as early as mid- to late Wednesday morning, as convective debris lingers into Iowa from overnight convection in the Dakotas and Minnesota tonight. Most of short-range guidance has this activity diminishing by the time it arrives in our forecast area, as the airmass over Iowa will be more stable than farther north, at least in the morning hours. However, we saw storms persist into Iowa this morning under less favorable conditions, so it's certainly possible a few showers or even a thunderstorm grazes northern Iowa this morning. Fortunately, these storms would be elevated with less than 1000 J/kg of MUCAPE, so anticipate storms will be sub-severe albeit with some gusty winds possible given the dry sub-cloud air.

A boundary is then expected to set up over western into northern Iowa through the day Wednesday, as a very subtle 500 mb shortwave passes from west to east across northern Iowa. The combination of this weak wave and boundary will result in thunderstorm chances over northern Iowa Wednesday afternoon through the evening. The thunderstorm environment through this period isn't necessarily jumping off the page, depicting modest instability (1500 to 2000 J/kg of MLCAPE) and marginal deep layer shear (25 to 35 kts of 0-6 km shear). This is sufficient for a few organized updrafts and strong to severe storms. The main risk with storms will be the damaging wind potential, as a well-mixed boundary layer ahead of the boundary will promote evaporative cooling and enhanced winds down to the surface. Hail will also be a possibility, although large hail may be difficult to come by, barring an increase in wind shear allowing for supercell development. Finally, the tornado risk also appears low with relatively high LCLs and marginal low level SRH (50 to 100 m2/s2) but can't rule it out with any storms tied into a surface boundary. With 1.7" to 2.0" precipitable water values along the boundary, efficient rainfall may occur with these storms. Rainfall amounts around an inch are expected, with localized pockets of 2 to 3 inches possible, mainly over north central Iowa.

The severe thunderstorm potential generally wanes late Wednesday evening and overnight, but isolated to scattered elevated storm activity may still linger along the boundary as it sags southward into the overnight hours. That said, a lull in activity is possible overnight before more storms begin to move in from the west early Thursday morning, being fed by the LLJ nosed up into the Plains. Model guidance isn't in complete agreement for how this second round of storms will look, as the northward extent of the jet varies among solutions. This comes in the form of a mesoscale convective system, but track will be dependent on the jet and the final position of the boundary. Damaging winds could be possible should this MCS hold on into central Iowa, although guidance is trying to dissipate the system as it enters the state early Thursday. Of similar concern would be more heavy rainfall associated with this system as it moves through, as well as redevelopment associated with any MCVs as it moves through the state Thursday. It's tough to put too much stock in redevelopment on leftover mesoscale features at this range, but will want to watch high resolution models as additional thunderstorm development is possible again Thursday afternoon over far southern Iowa and into Missouri.

LONG TERM /FRIDAY THROUGH MONDAY/

Issued at 252 PM CDT Tue Jul 7 2026

One more shortwave passes through the 500 mb pattern on Friday, bringing more shower and storm chances to the state, albeit to a lower confidence given a lot of the moisture transport will be focused to the south of Iowa. After this Friday wave, 500 mb ridging fills in aloft, keeping conditions dry and warm for most of the state through the weekend. Highs by next week climb back into the upper 80s and potentially the low 90s. This high pressure looks to stick around for a few days, before eventually breaking down late next week.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1223 PM CDT Tue Jul 7 2026

VFR conditions prevail under mostly clear skies and calm to light winds generally out of the south to southwest today. Scattered cumulus clouds around 3k to 3.5k ft have developed, but shouldn't lead to much more than very brief MVFR conditions. Otherwise winds remain light and variable overnight with high clouds drifting through.

HYDROLOGY

Issued at 252 PM CDT Tue Jul 7 2026

Rivers and streams in central Iowa continue to see increased flows as water continues to route through the system. One river in central Iowa maintains a flood warning, which is the South Skunk River near Colfax (CFXI4) that has actively crested at moderate flood stage and will be falling below flood stage this afternoon. This portion of the South Skunk River flows into the Oskaloosa (OOAI4) area, but at this point should remain below it's minor flood stage. Other rivers within the Des Moines and Cedar River basins are also at increased levels as water works it's way down stream, albeit all below flood stage and continuing to recede.

Additional rainfall later this week, especially Wednesday evening through Friday, could lead to slower improvement and/or additional rises on area rivers, depending on what basins this rain affects. The heaviest rain looks like it will fall over north central Iowa, and should be in isolated pockets. However, should one of these isolated pockets fall in the wrong spots, conditions may be exacerbated.

DMX WATCHES/WARNINGS/ADVISORIES

None.