textproduct: Des Moines

KEY MESSAGES

- Scattered thunderstorms ongoing early this morning. A few strong storms with large hail could occur. Localized heavy rain could lead to isolated flash flooding should it occur over an urban area. Some gusty winds around 35-45 mph may develop this morning behind the storms as well.

- Additional storms could move into portions of northern to eastern Iowa later this morning and may bring a risk for strong to even damaging wind gusts.

- Warm and humid today with heat indices near 100 in southern Iowa.

- Active weather persists through much of next week with periodic chances for thunderstorms along with the potential for a few strong storms and heavy rainfall.

SHORT TERM /THROUGH TONIGHT/

Issued at 319 AM CDT Sun Aug 9 2026

Showers and thunderstorms have been festering initially in west/southwest Iowa but in the last couple hours additional convection has begun to develop further north on the nose of the strengthening low level jet. Although initially pointed more northerly nearabouts the Missouri River, this jet is expected to arc northeast to point through central Iowa as we get into this morning. With ample moisture pointed into the area, convection is expected to continue to develop and move through the area through the rest of the overnight hours with steep lapse rates and MUCAPE values of up to around 1000-2000 J/kg. CAMs have been having a very difficult time keeping up with current radar observations and overall not reliable for timing shower/storms out in terms of locations or overall coverage. However, expectations from this time last night are being achieved (scattered storms developing on the nose of the low level jet) but started earlier and further west. This ultimately leads to more folks seeing what is likely welcome rain. However, MRMS estimates of 1-1.5" of rain has already fallen with storms previously west of Jefferson indicating that rain totals are starting to add up quickly and rain rates of 1-2" per hour may be achieved at times. This could lead to instances of isolated flash flooding should these rain rates occur over an urban area. In addition to the heavy rain threat, will also be watching for large hail. Many of the storms this morning have likely had, or at least capable of, small hail, but storms that are able to maintain long enough to grow tall enough may result in instances of isolated large hail and this is the main severe threat we'll be monitoring through much of the overnight hours. Beyond that, we'll be watching the storms that are developing over the Dakotas as they look to grow upscale as they track across Minnesota and ultimately into portions of northern and eastern Iowa. These storms could then pose a damaging wind threat as they move across portions of the area later this morning, generally clearing the area prior to midday. These storms will be more progressive but could also bring quick bout of heavy rainfall.

Beyond the storms this morning (both rounds just noted), still seeing signals for some gusty around 35-45 mph winds developing on the backside of the storms so will continue to monitor for those. Then, warmer and humid conditions are on tap today. Forecast highs are in the low 80s in the north to low 90s in the south but dew points in the 70s will send heat indices towards the 100 degree mark if not over in portions of southern Iowa. Heat headlines were considered, but several failure modes are in place that may keep conditions from reaching the 105F degree criteria. First is the lingering convective debris from this overnight activity which will likely delay heating. Second is the wildfire smoke aloft which already kept temperatures down a degree or so yesterday and could certainly do so again. Third is NBM dew points are on the higher end of guidance so in lessening those a degree or so, heat indices fell enough to preclude the need for a widespread heat headline in mainly southern Iowa. Some amount of clearing and atmosphere recovery is expected and should conditions overachieve, a heat headline may still be needed, but overall expectation is for conditions to remain below a widespread 105F needed for a Heat Advisory, though again conditions will still be hot and humid.

With the boundary discussed the last several days still across the state, some redevelopment of storms remains possible but may hold off until later in the evening to overnight again with a strong cap in place thanks to very warm mid level temperatures of +12-14 at 700mb. The jet location is not as favorable tonight as it is this morning, but may still help storms develop in southern Iowa. Will also need to monitor upstream convection with some models hinting at a MCS moving into portions of the area early Monday morning. Confidence in overall evolution of activity remains lower with CAMs all over the place.

LONG TERM /MONDAY THROUGH SATURDAY/

Issued at 235 PM CDT Sat Aug 8 2026

The predominant westerly flow aloft will keep the surface boundary in the vicinity of Iowa through much of next week. This will have a couple impacts. First the wildfire smoke listed above will persist at times. In addition, the active weather pattern will persist with periodic chances for thunderstorms. The storms will bring an attendant chance for severe weather and the potential for heavy rainfall. At this time, it appears that dryer air and Canadian High pressure may bring a brief reprieve of the active and humid weather but already there are hints that return flow and active weather could again return again sometime next weekend.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 612 AM CDT Sun Aug 9 2026

VFR conditions are expected to prevail through this period. Early morning showers and thunderstorms are currently pushing east. Remaining shower activity is expected across the three easternmost terminals (KMCW, KALO, KOTM) through 15z, while KFOD should be clear by 13z and KDSM is clear by 12z. Variable winds are expected across northern Iowa through the day before taking on a prevailing easterly to northeasterly direction. Light winds are expected across northern terminals with gusts around 20kts possible across the south before sunset on Sunday. Otherwise, there is potential for patchy fog across northern Iowa Sunday night. Confidence in widespread impacts is too low for a mention in the TAFs at this time but will be assessed in future issuances.

DMX WATCHES/WARNINGS/ADVISORIES

None.