textproduct: Des Moines

KEY MESSAGES

- Scattered shower and thunderstorm chances this afternoon into the early evening. Severe risk is low, but isolated gusty winds and heavy rainfall are possible, mainly in southern Iowa.

- Drier conditions for most on Sunday with low chance (less than 20%) for scattered showers/storms in far southern Iowa.

- Dry conditions continue during the day Monday, thunderstorm chances returning northwest on Monday then area-wide on Tuesday.

SHORT TERM /THROUGH SUNDAY/

Issued at 246 PM CDT Sat Aug 15 2026

Low stratus continues to span much of the forecast area early this afternoon. This cloud deck has limited sunshine over the northern two thirds of the area, keeping temperatures relatively cooler compared to southern Iowa where skies are clearer. As of 2 pm, temperatures are only in the upper 70s over northern Iowa, but nearing 90 in far southern Iowa. The clearing in southern Iowa is notable not only for temperatures, but also for thunderstorm potential as a subtle shortwave and associated boundary tracks through Iowa today.

Weak radar returns are already being detected by the KDMX radar, albeit mostly showers at this time. Through the afternoon, mixing of the boundary layer will allow for destabilization and surface-based convection to develop, mainly over southern Iowa. Mixed layer CAPE values are expected to exceed 3000 J/kg, providing plenty of energy for displaced parcels. There will be no shortage of moisture around this afternoon, as indicated by the sultry upper 70 to near 80 surface dewpoints and precipitable water values of 2 to 2.1". This will make for rather efficient rainfall rates with any storm that develops. Isolated flash flooding could occur, but the sporadic storm coverage and progressive storm motions should limit the overall risk, so have therefore opted to hold off on another flash flood watch for this evening. With the efficient rain production, gusty winds could become a concern as updrafts go up and collapse into a well-mixed boundary layer boasting DCAPE values of 1500 to 1900 J/kg. This threat will also be fairly isolated and most likely over the southern portions of the area where sun has been more prevalent today.

While there are isolated risks with storms this evening, those mentioned above are generally the only things the storms have going for them. Mid-level lapse rates overhead are quite poor (around 6 to 7 C/km) and will actually be diminishing to under 6 C/km through the afternoon. The kinematics will also be fairly poor and storms will struggle to organize with deep layer shear values mostly under 30 kts. The low level kinematics are also unimpressive given the weak low level flow. Therefore, the risk for severe hail or tornadoes is low, leaving isolated gusty winds and heavy rainfall as the main concerns this evening. The storm prediction center's (SPC) marginal risk for severe weather (level 1 of 5) over southern Iowa seems appropriate for this afternoon. If any gusty wind risk exists, it will be with storms in this area with diminishing threat farther north. On the rainfall side of things, the weather prediction center has trimmed up the slight risk (level 1 of 4) for excessive rainfall to only include eastern and southeastern Iowa and a marginal risk (level 1 of 4) of excessive rainfall for the rest of the area.

Most of guidance pushes the boundary south of Iowa this afternoon, taking most of the remaining instability and overnight shower or thunderstorm potential with it. There is still a chance (~20% or less) for some showers or storms to scrape along the Iowa/Missouri border tonight into early Sunday, but most solutions keep this south of Iowa and over northern Missouri. For most, if not all of the area, Sunday looks like it will be a nice reprieve from the onslaught of shower and thunderstorm chances we've seen over the last week.

LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/

Issued at 246 PM CDT Sat Aug 15 2026

Our lull in precipitation chances will continue into the day Monday but our break is short-lived as shower and thunderstorm potential returns to northwest Iowa Monday night, and area-wide again Tuesday into Wednesday. Given this will be another northwest flow regime, it's tough to get too involved in the details. That said, the Tuesday storms do seem to have a rather healthy environment with increasing instability and modest deep layer shear supportive of more organized convection. SPC does have a day 4 15% risk for most of Iowa and WPC has put out a slight risk for excessive rainfall for Tuesday. The pattern remains relatively active through mid-week and then ridging begins to build through the second half of this week.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 648 PM CDT Sat Aug 15 2026

Showers and thunderstorms remain the primary focus across south central and southeastern Iowa this evening. KDSM and KOTM could see terminal impacts through 04Z. Light showers may affect KFOD, KMCW and KALO over the next few hours, though confidence remains high in no thunder with the northern activity. Showers and storms will taper off tonight, giving way to lower ceilings overnight. MVFR ceilings are expected across much of the area, with IFR to localized LIFR restrictions favored near KALO and KMCW in northeast Iowa. Patchy fog is also possible across northern Iowa late tonight. VFR conditions are expected to return tomorrow afternoon.

DMX WATCHES/WARNINGS/ADVISORIES

None.