textproduct: Des Moines

KEY MESSAGES

- Cloudy through tonight. Drizzle, patchy fog, and spotty showers this afternoon into tonight fading from northwest to southeast over the state through Tuesday morning.

- Brighter skies on Wednesday over parts of the state with some clearing.

- Intermittent showers and occasional storms return later Thursday through at least Saturday evening.

- Cool this week with highs in the 50s into the 60s.

SHORT TERM /THROUGH WEDNESDAY/

Issued at 151 PM CDT Mon Sep 21 2026

GOES-East day cloud phase distinction RGB imagery shows the state covered in low level water clouds with some deeper cores with glaciation associated with showers and a few storms moving into the northeastern part of the state and crossing the Missouri River into west central Iowa. Low level moisture is readily apparent on cross sections and forecast soundings, which will persist through this afternoon and tonight. In addition to the clouds, an upper level cyclonic spin associated with a shortwave trough is pushing over Siouxland early this afternoon as viewed on upper level water vapor imagery. While there will be drizzle at times, an increase is expected in showers over northwestern into central Iowa this afternoon and evening as this shortwave moves overhead. Further, the moisture laden environment with light winds is also conducive to fog, which is already light and present in portions of the state this afternoon. This fog is expected to persist into tonight and Tuesday morning. All of this moisture and cloud cover will also keep low temperatures higher than the initial National Blend of Models and have raised overnight lows a few degrees.

As the main shortwave departs tonight, a trailing, weaker shortwave will move in and pass over the state Tuesday through Tuesday night. Any showers in the southeastern part of the state in the morning should be pushed away and any visibility reductions due to fog will improve. Some sunshine is possible over northeastern sections of the state as well, but for many it will remain cloudy. Following the weak shortwave will be drier air, which will erode much of the mid level moisture late Tuesday into Tuesday night with dewpoints falling into the upper 40s and low 50s. With temperatures falling similarly and relative humidity near 100% with light winds, fog formation comes to mind. Forecast soundings show an elevated layer at worst pointing to clouds with MOS guidance generally unrestricted with visibility so will keep tabs on this possibility in future forecasts. Otherwise, Wednesday is looking like an overall excellent first day of autumn with dry conditions through the day and highs in the 60s as a ridge axis bulges northward. The biggest uncertainty on Wednesday's forecast is how much sunshine will accompany these conditions due to lingering moisture in the low levels per cross sections.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/

Issued at 151 PM CDT Mon Sep 21 2026

The ridge axis that nosed up into the north central US will be pinched off as shortwave energy starts to flow into the region. These pieces of energy will be coupled with waves of low level thermal lift, weak to modest QG convergence surges, and a nocturnal low level jet pointed into eastern Nebraska or Iowa from Thursday into at least Saturday. All these factors point to an active period of wet conditions featuring showers and occasional storms with short spans of dry conditions. Atmospheric moisture will also tick upward from Thursday with precipitable water values back above 1.5 inches, which will be more common than not through Saturday evening. While warm cloud depths and precipitable water values will not be as high as last week, they will still be well above normal for the latter part of September and favor efficient rainfall production and slow movement given the 850-300mb flow between 20 and 30 knots. Rainfall totals from the global models are not eye popping at 1 to 3 inches Thursday through Sunday morning with ensemble probabilities less than 20% for 1" of rainfall in a 24 hour period. However, given antecedent wet conditions (National Water Model analysis showing 60% or higher soil moisture, NASA SPoRT top 4" and 16" showing 70th percentile or high soil moisture south of Iowa 3) and elevated streamflows in all but the upper Iowa River basin and the upper forks of the Des Moines River, will need to monitor rainfall trends for any flash flooding or additional rivers rises later this week into the weekend. Lapse rates during this period will be weak and any amount of instability and favorable shear do not overlap temporally so while there could be a few strong storms, no widespread severe weather is foreseen. This is further supported by AI/ML guidance, which is not pinging on anything late this week and weekend.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1159 PM CDT Mon Sep 21 2026

MVFR to LIFR ceilings and visibilities are impacting much of the area early this morning. Fog and drizzle are spanning much of western into central and southern Iowa, with lingering showers farther east. Conditions won't change much overnight, but will see steady improvement in the morning. Of note, some drier air is moving in near KMCW and KALO, so could see ceilings bounce around between VFR and MVFR/IFR. However, another northward push of moisture will keep low clouds around into tomorrow.

DMX WATCHES/WARNINGS/ADVISORIES

None.