Severe Thunderstorm Warning 309, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
245 PM CDT Fri Aug 7 2026

.KEY MESSAGES...

- Scattered thunderstorms through early this evening. A few
  severe storms remain possible.

- Mostly dry tonight into Saturday.

- Additional thunderstorm chances late Saturday night into
  Sunday.

- Active weather will persist through much of next week.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 243 PM CDT Fri Aug 7 2026

Thunderstorms are ongoing over north central Iowa in advance of a
boundary that is moving in from the northwest. MLCAPE values of 2000-
3000 J/kg along with mid-level lapse rates at 8-8.5 C/km have led to
strong initial updrafts with 65 dBZ over 20 kft occurring. The
primary storm initialization is on a pre-frontal trough that has
extended into northern Iowa from west to east. Expect much of the
activity this afternoon to remain associated with the current storm
cluster with the potential for some additional development back
west/southwest along the pre-frontal trough. These storms will
maintain a damaging wind and large hail threat through the remainder
of the afternoon as the entire system settles south/southeast. These
storms should exit south into Missouri by early this evening.

The remainder of tonight into much of Saturday is expected to be
dry. Much drier dew points will settle into the state behind the
boundary with dew point values falling into the low 50s north to low
to mid 60s south. Deep layer drying will also be occurring which
will further support the dry forecast.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 243 PM CDT Fri Aug 7 2026

Return flow begins Saturday night as high pressure moves to the
east of the state. Strong theta- e advection and an increasing
low level jet of 40-45 kts will lead to increasing instability
and thunderstorm chances.

Upper high pressure over Hudson Bay combined with upper high
pressure over the Four Corners region, will lead to progressive
westerly flow over much of the northern CONUS with periodic embedded
short waves passing across Iowa. This flow will also keep a surface
boundary in the Midwest area and resulting in several chances for
thunderstorms before Canadian high pressure arrives early next week.
PWAT values of 1.50-2.00" will be common during active storm periods
that could lead to an aggregate heavy rain threat through the week.
Temperatures will be seasonal and mainly in the 80s through midweek
the gradual cooling as the Canadian high pressure approaches for the
end of next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1237 PM CDT Fri Aug 7 2026

Morning fog has transitioned to a dissipating MVFR stratus
layer. In addition, new MVFR cumulus has developed from this
residual moisture. Expect these cigs to continue to rise and
diminish this afternoon. A boundary will enter the state this
afternoon and will bring thunderstorms from north to south into
the early evening. MVFR or lower vsbys and cigs are possible in
vicinity of storms. Outflow winds are also possible with gusts
over 35 kt. Otherwise, the wind will be mostly 12 kts or less.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

SHORT TERM...Donavon
LONG TERM...Donavon
AVIATION...Donavon

Hazardous Weather Outlook
National Weather Service Des Moines IA
1250 PM CDT Fri Aug 7 2026

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-081800-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun-
Webster-Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene-
Boone-Story-Marshall-Tama-Audubon-Guthrie-Dallas-Polk-Jasper-
Poweshiek-Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union-
Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-
Appanoose-Davis-
1250 PM CDT Fri Aug 7 2026

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

There is a Slight (Level 2 of 5) Risk for severe weather across much
of Iowa today. Large hail is the primary threat but damaging winds
and a tornado is possible.

There is a Marginal (Level 1 of 4) Risk for excessive rainfall
across much of Iowa today.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

There is a Marginal (Level 1 of 5) Risk for severe weather across
much of Iowa Saturday and again on Sunday. Damaging winds are the
primary threat.

There is a Marginal (Level 1 of 4) Risk for excessive rainfall
across much of Iowa Saturday and again on Sunday.

Shower and thunderstorm chances will continue through the weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed, but any storm reports are
appreciated.

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