Severe Thunderstorm Warning 313, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
324 AM CDT Sun Aug 9 2026

.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 /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1159 PM CDT Sat Aug 8 2026

Main challenge in the near term will be shower and storm timing,
as development has been ongoing over western Iowa and is slowly
expanding in coverage. Given recent trends, have pushed up
PROB30 mentions for storms at KDSM and KFOD around 06-07z.
Shower and storm coverage is expected to increase in coverage
through the next several hours, with highest chances near KMCW
and KALO near sunrise as a line of storms arrives into Iowa.
MVFR conditions are possible at times with this activity due to
periods of lowered ceilings and/or visibility restrictions. VFR
conditions across the terminals should return late morning and
through the remainder of the period, with winds turning more
variable as a boundary moves into the state.

&&

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

&&

SHORT TERM...05
LONG TERM...Donavon
AVIATION...Bury

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Special Weather Statement
National Weather Service Des Moines IA
407 AM CDT Sun Aug 9 2026

IAZ023-024-090930-
Humboldt IA-Pocahontas IA-
407 AM CDT Sun Aug 9 2026

...A STRONG THUNDERSTORM WILL IMPACT EASTERN POCAHONTAS AND WESTERN
HUMBOLDT COUNTIES THROUGH 430 AM CDT...

At 407 AM CDT, Doppler radar was tracking a strong thunderstorm 5
miles east of Pocahontas, moving east at 20 mph.

HAZARD...Wind gusts up to 50 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Pocahontas, Rolfe, Gilmore City, Palmer, Bradgate, Pioneer, and
Pocahontas Municipal Airport.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4267 9426 4264 9438 4264 9444 4263 9444
      4260 9457 4277 9471 4291 9444
TIME...MOT...LOC 0907Z 256DEG 18KT 4271 9456

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...50 MPH

05