textproduct: Des Moines

KEY MESSAGES

- Occasional shower and storm chances possible tonight and Saturday. Overall severe risk is low, but a few stronger storms could produce hail or gusty winds.

- More widespread shower and storm chances on Sunday. A few stronger storms are possible.

- Increased severe weather and heavy rain chances on Monday. Heavy rain potential continues through mid- week.

SHORT TERM /THROUGH SUNDAY/

Issued at 249 PM CDT Fri Sep 11 2026

Surface high pressure over the Great Lakes region is being slowly pushed eastward as a subtle 500 mb shortwave brings surface low pressure eastward into the state today into tonight. Current conditions are reflective of this transitioning pattern, as skies remain clear and temperatures warm, but with breezy winds signal the tightening pressure gradient ahead of the approaching low pressure.

As we get into this evening and overnight, the low pressure to our north and west will continue eastward, advecting low level moisture northward ahead of it and eventually dragging a boundary through the state. Models have been progging at least isolated showers or storms overnight as this system passes through the area, although the best chances for rain certainly reside farther north over Minnesota nearer to the synoptic lift and where mid-level moisture is more plentiful. Farther south over Iowa, any showers or storms that occur will need to overcome dry mid- levels and primarily rely on convergence along the passing boundary for lift. There will be some instability in the layer (~500 J/kg), so it's certainly possible a displaced parcel or two is able to overcome the dry air and produce a few showers or a brief storm, but this will be far from widespread. Therefore, have maintained low end rain chances (15 to 30%) in the forecast, with the best chances over northern Iowa. The storm prediction center does still have a marginal risk for severe weather over northwest Iowa (wind and hail), but the overall severe risk looks low.

The wave and associated boundary generally push through Saturday morning, flipping us to northerly surface flow and bringing in drier surface dewpoints and low level moisture. However, despite this low level drying trend, another push of mid-level moisture may leave the door open for additional showers and storms in southern Iowa. This appears to be mostly post-frontal and elevated, which should help mitigate the concern for surface based convection. However, 1500 to 2000 J/kg of elevated instability and moderate amount of shear could certainly promote a few stronger storms in southern Iowa Saturday. With thunderstorm activity being elevated, wind and hail will be the main concerns with any organized storms. Again, a marginal risk for severe weather will be in place on Saturday, this time over southern and southwestern Iowa. A marginal risk of excessive rainfall marks the same area, as heavy rain could occur with any of these storms. For the rest of the state, Saturday will bring cooler temperatures and drier conditions as dewpoints generally fall into the 40s and 50s by Saturday afternoon.

Upper level ridging begins to develop to our west as a trough digs in over the pacific northwest on Saturday into Sunday. For Iowa, this will bring another slug of mid level moisture into the state and the potential for more widespread rain and isolated thunderstorms on Sunday. This activity will once again be fairly elevated, as high pressure and cool air will still be in place at the surface. Therefore, expectation is activity will be scattered light to moderate rain associated with the mid level moisture and theta-e advection. The severe risk appears low but thunderstorms are certainly possible with 1000+ J/kg of elevated instability. A stronger storm also can't be ruled out given the increasing flow aloft but hail and wind would be the only concerns, as any storms will be quite elevated.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

Issued at 249 PM CDT Fri Sep 11 2026

The pattern turns quite active starting Sunday night, as deep layer moisture increases ahead of an approaching 500 mb trough and multiple subsequent waves keep the gulf moisture stream open through the first part of the week. The first day of concern will be Monday as the aforementioned 500 mb trough passes through the northern CONUS. This will bring a push of low level moisture and increasing temperatures up into Iowa, along with strong mid and upper level flow. Instability values in our area will maximized Monday afternoon, with plenty of shear for organized storms. Fortunately, a warm nose aloft will work to keep the atmosphere capped off and activity surface based, at least at this lead time. Still, strong 850 mb winds could certainly support some damaging winds. The storm prediction center has already started to key in on Monday, with a Day 4 15% risk over central Iowa.

The active weather continues through at least Tuesday and Wednesday, although the pattern looks to transition to more of heavy rainfall threat through these next two days. Modeled PWATs around 1.9 to 2" will be conducive for efficient rainfall, and multiple days of convection along a quasi-stationary boundary could lead to some flooding concerns. It's still a bit early to get too ingrained in details, as mesoscale factors could cause this boundary to sink or move around, but the current synoptic setup certainly points towards potential hydrology concerns through next week. The weather prediction center is already on top of this as well, with slight risks for excessive rainfall spanning from Sunday to Tuesday of next week.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1232 PM CDT Fri Sep 11 2026

VFR conditions prevail over the area this afternoon. Scattered low clouds (around 2000 to 3000 ft) are slowly dissipating over southern Iowa. Otherwise, breezy south to south southwesterly winds have developed primarily over the northern half of the area, with gusts of 20 to 25 kts ongoing. These winds will diminish some into the evening and steadily become more southwesterly before a frontal passage flips the wind direction to north northwesterly early on Saturday. Finally, an isolated shower or storm is possible overnight, mainly over northern and northeastern Iowa (near KMCW and KALO). Confidence is low in impacts at the terminals, so have maintained only PROB30 SHRA mention.

DMX WATCHES/WARNINGS/ADVISORIES

None.