textproduct: Des Moines

KEY MESSAGES

- Fog across much of Iowa again tonight through Thursday morning. Light drizzle or rain possible in souther and southeast Iowa overnight.

- Overnight thunderstorms across Iowa very late Thursday into Friday morning. A few strong to severe storms are possible overnight with hail the primary hazard.

- Strong to severe thunderstorms are possible once again Friday afternoon and evening across Iowa. Uncertainty remains in the evolution of the incoming system which would impact the severity and type of hazards possible on Friday.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 254 PM CST Wed Mar 4 2026

Overcast conditions have lingered across Iowa throughout the day, along with patchy fog across southern Iowa this afternoon. Stratus will remain widespread through the overnight with fog expected to redevelop through Thursday morning. Fog tomorrow morning may not be as dense as was seen this morning and HREF guidance is less aggressive with mean visibility forecasts. Still, model soundings indicate plenty of available moisture with low level saturation through the boundary layer. A system moving across Missouri overnight may bring a few scattered showers to far southern and south east Iowa towards the early morning hours tomorrow.

Our attention then turns to a robust longwave trough that will bring two rounds of thunderstorms to Iowa from Thursday night through Friday. Round one arrives with the strong southerly flow ahead of the wave bringing warm air advection and strong moisture transport into the area. Convection is expected to develop across Iowa very late after midnight (around 3 am) and continue through 7-8 am on Friday morning as the low level jet strengthens and fuels the convection. Soundings indicate that convection should remain elevated with hail being the primary concern. Strong winds are possible west as convection initializes, but that threat should diminish as storms get into central Iowa.

A lull in activity is expected midday on Friday. Evolution of the afternoon convection in Iowa will hinge on two key components. The first is how much clearing occurs after the morning convection across the state. Current model guidance, including soundings, suggests stratus may remain in place and could put a damper on convection later in the day. On the other hand, if we are able to get clearing, even for a short time, instability will increase enough to allow more robust afternoon convection. With plenty of shear around it won't take much instability for robust convective development and this can occur with even short windows of clearing. The other important component is what the synoptic evolution will look like across Iowa. Models remain split with the GFS favoring a tightly wound surface low lifting across the area while the Euro favors and open wave pattern. Both have chances for severe storms, however the GFS solution would result in an increased threat for super cells initially and increase the tornado potential in Iowa. With the Euro solution, the tornado threat would be lower and focus mainly on wind and hail with a more linear structure. With strong shear in place, a quick spin-up would still be possible in this scenario, but the intensity would likely be lower. In both cases severe weather is expected. As additional data is available we will continue to fine to the hazard type and intensity expectations.

LONG TERM /SATURDAY THROUGH TUESDAY/

Issued at 254 PM CST Wed Mar 4 2026

The system quickly departs with high pressure settling across the area through the weekend. Temperatures will be mild on Saturday, then warming further on SUnday with increasing southerly flow into the area. Warm air advection continues into early next week with 60s to near 70 by Monday. The next week looks to remain active with several waves moving across the central US. The next chance for precipitation impacts across Iowa looks to arrive on Tuesday.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1136 AM CST Wed Mar 4 2026

Widespread stratus with lingering light fog remains in place across Iowa this afternoon. While most areas have improved to MVFR, parts of southern Iowa continue to see IFR to LIFR conditions. This evening those poor flight conditions will expand again with widespread fog and low stratus across all sites. IFR conditions are expected across all sites and pockets of LIFR are possible, especially in southern Iowa. A few scattered rain showers are also possible in southeast Iowa at KOTM through the early morning hours.

DMX WATCHES/WARNINGS/ADVISORIES

None.