textproduct: Des Moines

KEY MESSAGES

- Showers and non-severe thunderstorm potential overnight into early Wednesday morning, mainly over far southern Iowa.

- Widespread moderate to heavy rainfall increases from the south and west later Wednesday through Thursday morning. Thunderstorms are possible, but severe threat is low.

- Increasing potential for severe thunderstorm mid-day Thursday into the afternoon and evening. All hazards possible.

- Additional severe thunderstorm potential on Friday, then drier and mild through the weekend.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 301 PM CDT Tue Mar 31 2026

Our cold front today has now passed through the entire area, leaving widespread northerly winds across central Iowa. Winds have been quite breezy today, sustained around 15 to 25 mph with gusts up to 40 mph at times. Cold air advection has lead to milder temperatures as well, dropping many locations almost 10 degrees through the morning. However, sunshine behind the front has still let temperatures warm some today, with much of the area in the upper 40s and 50s. The threat for severe weather this afternoon has generally diminished with the departure of the front, although some elevated instability does remain over southeastern Iowa. That said, a stout warm nose and lack of any robust forcing appears to keep any convective initiation at bay into the evening.

Theta-e advection will steam back northward and overrun the cold front to our south overnight tonight as another surface low develops over the Texas/Oklahoma pan handles. This will introduce the potential for some additional elevated showers and thunderstorms over far southern Iowa early Wednesday morning. Instability will have waned considerably by this point, generally under 500 J/kg, so the risk for severe weather with this activity appears low. Likewise, precipitation has been trending southward in recent guidance, indicating it will be mostly along the Iowa/Missouri border and southward.

The aforementioned weak surface low to our southwest and front to our south will retreat back north toward Iowa on Wednesday, being helped along by a more robust upper level wave and deepening surface low over the planes. This progression through Wednesday will bring a healthy stream of moisture transport up toward Iowa and result in a prolonged period of rainfall overnight Wednesday and into the day Thursday. This moisture plume will boast anomalously high moisture transport for this time of year and PWAT values pushing 1.5. For context, the climatological daily max for this time of year is right around 1.2 to 1.3. While these values arent anomalous for warm season precipitation, they are quite high for an event this early in the year. The net result will be widespread precipitation starting as soon as Wednesday afternoon in the south and west and lasting through at least Thursday morning. QPF output indicates a widespread 1 to 2 of rain, with a few locations potentially exceeding 2 through central Iowa. This will generally be a beneficial rainfall for the area, given dry antecedent conditions but widespread rain of this magnitude may very well prime the area for future rainfall issues. More on potential hydrological impacts in the hydro section below. With the saturated profiles and poor mid-level lapse rates, instability will be marginal overnight Wednesday into Thursday, limiting severe potential until the main low approaches on Thursday. Likewise, warmer temperatures in northern Iowa overnight will help to mitigate concerns with frozen precipitation, although a brief wintry mix could still scrape far northern Iowa through this period. Minimal impacts are expected given the warm air advection.

As we get into the day on Thursday, a negatively tilted upper trough and surface low pressure will lift directly overhead, bringing better instability, 60+ dewpoints and strong kinematics from a 50+ kt low level jet into central Iowa. Time of day and preceding convection from the morning will play a factor in the severe weather environment on Thursday, as will the amount of shear present, but the synoptic set up does raise some concerns. Should the atmosphere recover, severe thunderstorms would certainly be on the table through mid-day Thursday as the surface low pushes through, with all severe hazards possible. The storm prediction center currently has a marginal risk (level 1 of 5) for severe weather on Thursday and a broad slight risk (level 2 of 5) just to our east. This seems reasonable given the uncertainty with the morning convection in the warm sector, but the severe threat Thursday will certainly warrant watching closely. In addition to severe weather potential, strong winds are possible in the warm sector where the stout low level jet exists.

LONG TERM /FRIDAY THROUGH TUESDAY/

Issued at 301 PM CDT Tue Mar 31 2026

The Thursday surface low and coincident upper level wave pushes through the area by Thursday evening, but another prominent upper level trough will follow quickly on its heels. This system arrives in Iowa on Friday, bringing surface low pressure with 60 dewpoints and a healthy amount of instability and deep layer shear through the area. This will introduce yet another day of severe weather potential on Friday. The storm prediction center has issued a 15% risk for severe weather as a day 4 outlook, which again seems warranted given synoptic setup and parameter space. We will continue to evaluate this system as it draws nearer. After the storm potential on Friday, conditions dry out a bit through the weekend with milder temperatures in the 40s and 50s both Saturday and Sunday.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 708 PM CDT Tue Mar 31 2026

Northeasterly winds will shift to ESE through the TAF period, bringing in additional moisture for lowered ceilings and two rounds of precipitation chances. Through the overnight, precip is expected to remain south, with a 30% chance of showers and MVFR ceilings at KOTM from 7-12z. The next round of showers arrives in the morning at the southern sites, and afternoon for the northern sites. Afternoon showers at KDSM and KOTM sites have a 30% of thunder and IFR ceilings, though potential at other sites will continue to be monitored. KDSM and KOTM winds may gust to 20-24 knots after 16z. Exact timing of showers and thunderstorms, along with impacts to ceilings and visibility, will be monitored for future updates.

HYDROLOGY

Issued at 301 PM CDT Tue Mar 31 2026

Multi-day moderate to heavy rainfall event over the next few days will result in short and long term flooding considerations mainly across the southeast half of the CWA. Short term considerations include potential ponding and low-end flash flooding. Soil moisture values are generally running near to below normal. That data combined with the QPF suggests ponding and flash flood concerns will be mainly rate driven vs. amount driven, with the greatest risk in urban areas.

Longer term considerations include potential river flooding. National Water Model, HEFS and QPF ensemble hydrographs indicate the most likely scenario on area rivers will be moderate to significant within-bank rises. A couple locations reaching flood stage are possible as well. The peaks on most rivers would occur this weekend into early next week. Greater concern is the next several days of rainfall may set the stage for more significant impacts going forward since the CPC outlook for April includes above normal precip. Elevated soil moisture and streams will not require as much runoff to become impactful if the wet pattern continues.

DMX WATCHES/WARNINGS/ADVISORIES

None.