textproduct: Des Moines

KEY MESSAGES

- Patchy to locally dense fog ongoing across northern and west central Iowa. This is expected to burn off after sunrise.

- Low shower chances through the early part of the day before more widespread strong to severe thunderstorms develop later today into the overnight. There is a Marginal (Level 1 of 5) Risk for severe weather.

- Widespread rain chances move back into Iowa later Thursday night into Friday and Saturday leading to mild and perhaps damp conditions for trick-or-treating. Rumbles of thunder also possible on Friday.

- Temperatures remain seasonal if not above normal through the next week.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 229 AM CDT Wed Oct 28 2026

Patchy to locally dense fog is ongoing across parts of west-central and northern Iowa. A look around various webcams show isolated pockets of poor visibility around Mason City, with less impacts to visibility elsewhere in places like Denison, Fort Dodge, and Algona. All of this jives with the visibilities being reported on METARs. A complexifying factor with this is that the fog is in a relatively narrow ribbon of higher dewpoints ahead of an area of stratus. Regardless, the fog is expected to burn off after sunrise this morning.

Other notable conditions around the state include that we are in southerly flow, which is going to aid in warming the state up to much above-normal temperatures through the day before a cold front sweeps through closer to sunset - more on that later. The southerly flow is noted both at the surface and at 850mb (albeit, with a slight southeasterly component to it), which leads to decent moisture transport into the region. Up at 500mb, flow is a lot more easterly, leading to less moisture transport in the upper levels. Also noted at 500mb is a fairly potent shortwave that will move through the region, which is the feature tied to the aforementioned cold front. While the impacts of the shortwave will be a little spicier north of Iowa where the parameter space is better, strong to severe thunderstorms will still be able to form across portions of western and northern Iowa later today. Additionally, ahead of any convective activity, a tightened pressure gradient will lead to breezy winds gusting as high as 30mph at times throughout the state.

As far as the expectations for any severe weather, sounding profiles around Iowa show that capping could be an issue, with the 00z HRRR and NAM showing a mid-level cap at around Algona and Estherville, while at sites farther south and west (i.e. Fort Dodge, Mason City, and Iowa Falls), mid-level capping is not as much of an issue. The other elephant in the room demanding to be addressed is CAPE. Aforementioned sounding profiles show fairly skinny CAPE profiles, especially farther to the east. This, combined with a low freezing level (~8500ft) and dry air in the mid- to upper-level will support decent hail growth with more robust updrafts. The drier air will also aid in the potential for severe wind gusts. At the same time, lapse rates look fairly low, at around 6.5 degC/km across the state which will help balance how widespread severe storms are able to be. Finally, while there is plenty of low-level turning, capping will keep storms in check across Iowa, making it very difficult for surface-based convection in the area.

As the cold front moves through, it should be clear of the area around or just after midnight, signaling the end of this round of showers and storms. Thursday looks to be largely with temperatures still above normal for this time of year. High pressure will attempt to set up across MN/WI which will influence much of Iowa leading to light winds and calm conditions with fairly clear skies. The next system that will impact the area looks to arrive Thursday night into Friday as another low lifts into the area from the south.

LONG TERM /FRIDAY THROUGH TUESDAY/

Issued at 246 PM CDT Tue Oct 27 2026

While it will not rain continuously, showers are expected from Friday through a good portion of Saturday across many portions of Iowa with peals of thunder likely on Friday as well. There is variability in the models whether this rain will last all the way through Saturday or if Saturday starts to turn drier or if Sunday morning will have lingering showers as well. Regardless, trick or treaters will encounter mild conditions and perhaps damp ones as well Friday or Saturday evening depending on when the festivities are held. Quickly following this southern stream wave will be a more pronounced mid-level trough or closed low that will push over the Rockies by the start of next week and into the central part of the country by the middle of next week. While there is uncertainty in the exact mid-level pattern evolution early next week, confidence is increasing in another round of showers and thunderstorms in this timeframe. With this being one of several rounds of rainfall spread out over the next week with total rainfall between 1.5 and 2.5 inches over the state from the grand ensemble, some within bank rises are possible on mainly smaller streams and tributaries to the larger rivers according to recent runs of the National Water Model forced by the NBM and GFS.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1216 AM CDT Wed Oct 28 2026

VFR to LIFR conditions are expected through the morning. At northern sites (KFOD and KMCW), dense fog has developed leading to LIFR visibilities and ceilings. KFOD in particular is on the edge of the area of fog, however, progression and movement has been extremely slow. Thus, TEMPO groups were introduced. After sunrise, all sites will be VFR through most of the day. The next round of impactful weather looks to be closer to the end of this period as a cold front moves across Iowa. For now, 4-hour prevailing -TSRA was introduced at KFOD, KMCW, and KALO toward the end of the period. This timing will be refined in later issuances, but confidence is high enough to include at these sites. Thunderstorms at KDSM have been handled with a PROB30 with lower confidence in southern coverage, and are not expected to reach KOTM by 06z, but thunderstorms may be introduced in this morning's 12z issuance at KOTM. Of note, transient and marginal low level wind shear is possible at KALO, KDSM, and KOTM with the frontal passage, but confidence is too low at this time to include in the TAFs.

DMX WATCHES/WARNINGS/ADVISORIES

None.