Severe Thunderstorm Warning 271, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
648 PM CDT Wed Jul 8 2026

 ...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

- Severe thunderstorms are possible this evening and tonight, with
  damaging wind gusts as the primary hazard.

- Heavy rainfall is possible with storms tonight, with a slight
  uptrend in precip totals.

- High pressure is expected to set up over the central U.S. this
  weekend into next week, bringing much warmer temperatures.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 249 PM CDT Wed Jul 8 2026

Currently, showers and thunderstorms are ongoing across southern
Minnesota along a boundary which is expected to push south/southeast
through the afternoon and evening. This forecast gets tricky because
there are two areas where convection is expected. The first is along
the aforementioned boundary across southern MN, and the other is
along an area of deep moisture convergence across western
Iowa/eastern Nebraska. Other than potential forcing mechanisms, the
environment is more or less the same for each area. Shear is
somewhat lacking for widespread severe weather, with 0-6km values
between 25kts on the low end and 45kts on the high end depending on
the model. The most favorable areas for shear are across far
northern Iowa and southern Minnesota, with another somewhat
favorable area in western Iowa.

The primary hazards with storms today are damaging wind gusts and
heavy rain. As for the damaging winds, soundings have the inverted-V
shape to them with T/Td spreads at the surface of nearly 20 degrees.
D-CAPE values are between 1000 and 1500 J/kg across much of Iowa and
guidance shows wind gusts of between 60 and 70mph through the
evening. Some potential uncertainty exists with how long storms
would remain severe. Weaker shear values may lead to cold pools
outrunning storm clusters which leads to a shorter and less
widespread severe window. Should this be the case, after
thunderstorms mature redevelopment could occur between the outflow
boundary and the main cluster. New updrafts in this in between zone
would lower the severe wind threat later this evening.

As for heavy rain, PWAT values still remain in the neighborhood of
2". Storms are expected to be somewhat slow-moving today, between 25
and 30mph. Rainfall totals have been trending upward slightly. REFS
and HREF values for the 90th percentile are still between 2 and 3
inches in areas of western and northern Iowa. Both are also hinting
at a signal for isolated instances of 3-4" or more of rainfall. Mean
values from the HREF and REFS are between 1 and 2 inches. Of note,
the axis of heaviest rainfall is still being progged away from areas
that received heavy rainfall this past weekend.

With regards to the hail and tornado threat for tonight, both are
low and very conditional. Hail is a balancing act between high CAPE
values (2000-3000 J/kg) and decent lapse rates (7+ C/km) will be
fighting a very high melting level and weak shear. The tornado
threat is much more conditional and will be very short lived.
Overall SRH values are very low across much of the area, and a brief
spin-up along the boundary with storm initiation is possible, in
addition to a few funnel clouds due to enhanced stretching, although
both cases have a low chance of happening.

Overnight, as the cluster to the west grows it is expected to dive
south and ride the CAPE gradient. For the most part, this cluster
will be limited in its northern and eastern extent through the
evening. Some guidance suggests that after sunset, instability is
lost and storms across central Iowa aren't able to sustain
themselves, limiting the spatial coverage to west-central and
southwestern Iowa. The Low Level Jet is expected to kick in sometime
around midnight, although it doesn't look like it will have a large
impact on any activity this far north. If the LLJ can nose further
into Iowa, this would help increase storm coverage into central and
south-central Iowa as the cluster moves to the southeast.

Tomorrow will be warm, humid, and largely dry through the day. Highs
around the state will range from the mid 80s to potentially the low
90s. Compared to previous forecasts, the LLJ is progged to kick in
farther south across Missouri. With the LLJ coming in farther south,
some showers and thunderstorms may graze far southern Iowa tomorrow
night as opposed to being more widespread across southern Iowa.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Issued at 249 PM CDT Wed Jul 8 2026

Another 500mb shortwave is progged to pass over Iowa Friday before a
high sets up this weekend pancakes much of the central U.S. Monday.
Once the high sets up, an increase in temperatures is expected with
highs making a run for the 90s through the early part of the
week.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 643 PM CDT Wed Jul 8 2026

Scattered thunderstorms moving across Iowa are the primary
aviation highlight this period. Thunderstorms will move from
north to south with some redevelopment occurring behind the
current activity. Covered storm chances at all sites though KOTM
will be later and diminished. MVFR cigs and vsbys are expected
with any thunderstorms. MVFR cigs may linger behind the
activity, especially over northern Iowa followed by scattering
Thursday afternoon. Outflow wind gusts from variable directions
is also possible. Otherwise wind will become light overnight
then southwesterly on Thursday.

&&

.HYDROLOGY...
Issued at 251 PM CDT Wed Jul 8 2026

Area rivers and streams that peaked earlier this week after the
heavy rain late last week into the weekend continue to recede but
many in the Cedar and Des Moines basins remain elevated, some close
to action stage. 3 hour flash flood guidance in much of northern to
central Iowa is only 2-2.5" with much higher amounts in western and
southern Iowa. This is largely due to the footprint of where the
heavy rain has occurred most recently. Similarly, NASA SPoRT 10 cm
soil moisture remains elevated near the Hwy 20-Hwy 30 corridors.
Some inconsistencies remain in models on how widespread storms will
be through portions of central Iowa with greater confidence in the
far north/northeast and in the west/southwest. Despite this, it may
not take much rain to renew flooding in locations that have recently
experienced flooding so issued a Flood Watch for those areas, and in
locations in northeast Iowa where model QPF is highest with HREF PMM
data suggesting 2-3", localized 4". These QPF totals are also seen
in portions of western Iowa, but as previously noted, flash flood
guidance is much higher in these areas. In terms of the environment,
Pwats top out around 2" near and along the boundary as it moves
southward through the night. These are combined with more than
sufficient warm cloud depths. Storm motions aren't overly slow, but
repeated rounds of rain may still occur as additional storms form on
the outflow from initial storms.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Thursday morning for IAZ006-007-016-017-
025>028-036>039-047>050-059>061.

&&

SHORT TERM...67
LONG TERM...67
AVIATION...Donavon
HYDROLOGY...05

Hazardous Weather Outlook
National Weather Service Des Moines IA
332 PM CDT Wed Jul 8 2026

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-092045-
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-
332 PM CDT Wed Jul 8 2026

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

A Flood Watch is in effect for portions of central and northern
Iowa. Please refer to the National Weather Service website at
weather.gov/desmoines for further details.

Scattered severe thunderstorms are possible across a large portion
of Iowa through this afternoon, evening, and overnight. Main
threats are damaging wind and flash flooding, though large hail
and a tornado cannot be ruled out.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Additional thunderstorms are also possible late week, with the
severe potential better determined in the coming days.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is possible tonight.

Preliminary Local Storm Report
National Weather Service Des Moines IA
642 PM CDT Wed Jul 8 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0633 PM     Tstm Wnd Gst     5 SW Rockwell City      42.35N 94.69W
07/08/2026  M52 MPH          Calhoun            IA   Public

            PWS gust.

&&

MD

Preliminary Local Storm Report
National Weather Service Des Moines IA
714 PM CDT Wed Jul 8 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0643 PM     Tstm Wnd Dmg     Rockwell City           42.40N 94.63W
07/08/2026                   Calhoun            IA   Trained Spotter

            5 inch tree limbs down.

&&

MD

Preliminary Local Storm Report
National Weather Service Des Moines IA
726 PM CDT Wed Jul 8 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0647 PM     Tstm Wnd Dmg     Lohrville               42.27N 94.55W
07/08/2026                   Calhoun            IA   Trained Spotter

            Parts of Lohrville is without power. Tree
            branches reported down.

&&

MD

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