textproduct: Des Moines

KEY MESSAGES

- Quiet, summer-like conditions expected today and Tuesday. Patchy fog may develop overnight into Tuesday morning.

- Warmer temperatures in the upper 80s and 90s on Wednesday, with thunderstorm and heavy rain chances returning Wednesday night into Thursday and potentially Friday.

- Warmer and drier conditions develop late this weekend into early next week.

SHORT TERM /THROUGH WEDNESDAY/

Issued at 245 PM CDT Mon Jul 6 2026

Dry and overall pleasant conditions are in place over Iowa today thanks to surface high pressure overhead. Winds have been calm to light, with cumulus clouds speckling the skies at the top of the mixed boundary layer. At the upper levels, ridging is in place over Iowa as a shortwave trough has stalled out to our south, keeping the gulf moisture stream disrupted. Farther north, weak energy topping the broad, western CONUS ridge is expected to produce thunderstorms along a southwest to northeast oriented boundary over the Dakotas and Minnesota tonight into Tuesday. This activity is expected to generally stay to the north of our forecast area, but there are a few model solutions that bring the outflow from these storms down into far northwestern Iowa. With the high pressure overhead, general subsidence and diminishing instability will likely work to dissipate updrafts as this outflow works southward, so have kept the forecast dry at this time, but will be monitoring for any activity persisting into the area early Tuesday morning.

Outside of any convective debris leaking into northern Iowa early Tuesday morning, skies will generally remain clear with light winds overnight. This, combined with dewpoints still in the mid 60s, will favor more patchy fog development as temperatures cool prior to sunrise early Tuesday morning. Model guidance is generally favoring the eastern portions of the state where winds will be relatively lighter, but could certainly see shallow fog in low lying areas through much of central Iowa. The surface high generally sticks around through Tuesday, maintaining the warm and dry conditions tomorrow.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/

Issued at 245 PM CDT Mon Jul 6 2026

The upper level wave to our south and surface high overhead will begin to depart eastward on Tuesday, bringing southerly return flow back up into Iowa Tuesday night through Wednesday. The result will first be warmer temperatures with highs in the upper 80s to low 90s on Wednesday. The upper level pattern will begin to transition to more zonal flow through this same period and the boundary to our northwest will begin to sink south and east towards the state. Weak energy working through the zonal flow will develop shower and thunderstorm chances along said boundary starting late Wednesday and lasting intermittently over Iowa into Thursday morning. Plenty of moisture (2"+ precipitable water values) and instability (~1500 to 2500+ J/kg of MUCAPE) will be present over Iowa during this same time, although shear will be minimal (20 to 30 kts of 0-6 km shear), suggesting updrafts may struggle to become organized. Likewise, while there does appear to be weak energy moving through the zonal flow, the forcing is unimpressive for most of the area, barring southwest Iowa where the low level jet is expected to nose into overnight. This jet could provide some extra lift for storms through central and southern Iowa Wednesday night into Thursday, but other areas may need a bit more juice to kick things off. Therefore, the main concern at this time is the potential for heavy rainfall fueled by this low level jet. See hydro discussion below.

The pattern remains active through the end of the week, with another shortwave slated to move through the midwest Friday, albeit with more uncertainty on exact track and evolution. However, by this weekend models show good consensus of a broad upper level ridge spanning much of the western and central US. This regime would lend itself to warmer temperatures and drier conditions for Iowa late this weekend and into early next week.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1046 PM CDT Mon Jul 6 2026

Trended more aggressive for fog this issuance as cloud cover will be delayed in reaching most TAF sites. Confidence has increased in river valley fog at KFOD due to less clouds and have reflected transient LIFR conditions typically seen there. KDSM will have a short window of MVFR vsbys from fog. Highest confidence in fog will be at KALO and KOTM with IFR vsbys possible within 2 hours of sunrise.

HYDROLOGY

Issued at 245 PM CDT Mon Jul 6 2026

Rivers and streams in central Iowa continue to see increased flow as water from the heavy rains late last week and this weekend continues to route through the system. Two rivers in central Iowa maintain flood warnings at this time. The first is the South Skunk River near Colfax (CFXI4) which is actively cresting at moderate flood stage and expected to fall below flood stage tomorrow. This portion of the South Skunk River flows into the Oskaloosa (OOAI4) area, but this point should remain below it's minor flood stage. The Iowa River near Tama (TMAI4) also maintains a flood warning as it continues to slowly rise, with an expected to crest at or just below minor flood stage today. 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 exact corridor of the heaviest rain is still uncertain, but will be monitoring closely through the coming days.

DMX WATCHES/WARNINGS/ADVISORIES

None.