textproduct: Des Moines

KEY MESSAGES

- Limited patchy fog in low lying areas this morning.

- Thunderstorm chances return into this afternoon through Thursday morning. A few storms may produce damaging winds and heavy rainfall.

- 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 307 AM CDT Wed Jul 8 2026

A look at observations across Central Iowa early this morning indicate temperatures in the low 70s, with dewpoints near the same values in some isolated locations under clear skies and calm or very light winds, leading to some patchy fog. While patchy fog may continue to form mainly in low lying areas until sunrise or so, a look further north into Minnesota shows a line of showers and thunderstorms near a boundary that are moving east-southeast with time. The convective debris (cloud shield) is extending southward, which has already started to move into northern Iowa and will likely continue the descent south through the morning, keeping fog formation relatively minimal. The aforementioned boundary is ahead of a mid-level shortwave trough that is currently over the Dakotas, which will continue to push east throughout the day, while the boundary gradually shifts slowly southeastward today. CAM guidance generally indicates that these showers and storms will not arrive into northern Iowa until around 17-18z, though this may be too slow, given how convection is at least slightly further south at this time and may result in an earlier arrival closer to mid-morning. If the current storms in southern Iowa do die before reaching the northern parts of the forecast area, additional storm development is expected to occur near/along this sagging front, with higher confidence in showers and storms entering northern Iowa by early-mid afternoon.

Ahead of this feature, conditions across Iowa will be on the hot and humid side, with highs in the upper 80s to low 90s and dew points in the mid 60s to low 70s, which will allow for instability to increase into the afternoon and remain through the evening, with values around 1500-2000 J/kg and shear values around 30 knots that will be favorable for storms to grow upscale to at least some degree. Less favorable lapse rates below 7 C/km and high freezing level heights (15 kft) will likely lead to difficulty in large hail development, though the damaging wind potential is much more favorable as storms gradually congeal into lines. The risk for a few isolated tornadoes also remains, though low, with SRH values below 100 m2s2 and limited directional shear. The Slight Risk per SPC was expanded further south and west to highlight the increasing potential for severe weather in these areas. A look at the environment for heavy rain potential indicates high PWAT values near 2 inches overhead towards the evening and overnight as this boundary nears the I-80 corridor, paired with the aforementioned deep warm cloud depths. The risk would increase further for flooding if any particular areas sees multiple storms, which would increase concerns substantially for new and renewed rises of rivers and also the potential flash flooding risk, especially in areas that received the several inches of rain late last week.

Through Thursday morning, the expectation per various models suggests that storms should generally have descended into south central to southern Iowa, with the lingering potential for severe weather as forcing for lift increases with some presence of the low level jet into west/southwest Iowa. Total rainfall amounts by Thursday morning are indicated around 1-2 inches, with isolated 3 inches possible over western into west central Iowa and lower values elsewhere across the state. As the boundary moves across southern Iowa, there remains a signal of a developing MCV that tracks eastward, which would bring a renewed potential for damaging winds and heavy rainfall. Recent guidance though has this feature further south into Missouri but still near southern Iowa, so will need to keep an eye on this. As this system departs later in the day, additional convection may fire off again over southern Iowa where the front may linger yet, though severe weather potential by this point looks more limited. The overall evolution of storm placement and track into Thursday will be heavily dependent on how the activity plays out later today into tonight, so trends will be very important to monitor.

LONG TERM /FRIDAY THROUGH TUESDAY/

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 /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 643 AM CDT Wed Jul 8 2026

Clouds will gradually increase from northwest to southeast today, ahead of showers and thunderstorms that are expected to move with a passing boundary across the state this afternoon to evening. Cannot rule out a storm this morning near KMCW given current radar trends, but confidence is not high that these storms will hold together, so have left out at this time and will monitor. While VFR conditions are generally expected, there could be brief periods of MVFR conditions as storms pass through due to visibility and ceiling restrictions. Winds will increase out of the southwest during the daytime hours, then turn variable tonight into Thursday, though storms could produce brief gusty winds.

HYDROLOGY

Issued at 638 AM CDT Wed Jul 8 2026

Rivers and streams in central Iowa continue to see increased flows as water continues to route through the system. Rivers within the Des Moines and Cedar River basins are 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 this 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.