Severe Thunderstorm Warning 261, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
640 PM CDT Thu Jul 2 2026

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

.KEY MESSAGES...

- Strong to severe storms continue tonight into the morning
  hours. Damaging winds, hail and heavy rain are the main
  concerns, but tornadoes are also possible.

- Storms today through Friday may lead to flooding or flash
  flooding concerns, especially in areas impacted by multiple
  rounds of heavy rainfall.

- Uncertainty remains with the forecast into the holiday
  weekend, but hot and humid conditions persist with
  thunderstorm chances at times.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 407 PM CDT Thu Jul 2 2026

A rather eventful forecast remains in place now through the next 24
to 48 hours, as a hot and humid air mass continues to bring
potential for thunderstorms and muggy conditions through the end of
this week and early in the weekend.

Our most immediate concerns are the storms ongoing right now, as a
mesoscale boundary sags southward over the northern half of Iowa. A
moist and unstable air mass with 3000+ J/kg of instability sits over
much of central into eastern Iowa, but the best effective wind shear
around 40 to 45 kts is in place along the mesoscale boundary. All
severe hazards are possible with these storms, including tornadoes
generally in proximity to the boundary where better vorticity is
available to the storms. Likewise, damaging winds and hail are also
possible, with the highest threat being the damaging winds. At least
scattered storms are expected to persist through much of this
afternoon and evening, especially as the low level jet ramps up
overnight. With the east northeast storm motions, and training
development along the boundary expected through the evening, heavy
rainfall also remains a concern as this activity persists into the
evening. Rainfall amounts of 1 to 3" have already been observed over
northern Iowa, with additional storms expected through the evening
and overnight, which would only exacerbate conditions. A Flood Watch
has been issued for much of northern Iowa. Will also be watching for
a southern expansion of the heaviest rainfall, especially as storms
persist through the day and evening.. More on the flooding concerns
in the hydro discussion below.

As we get late into tonight, storms developing to our west over
Nebraska and South Dakota are expected to evolve into a mesoscale
convective system (MCS) which will run along the mesoscale boundary,
fueled by a 45+ kt low level jet. This MCS arrives in western Iowa
early Friday morning, bringing the potential for damaging winds and
more heavy rainfall along similar areas to today. As it tracks
eastward, it will eventually lose support from the low level, but
the 2000 to 3000 J/kg along the boundary and a strong enough cold
pool would help the storms persist all the way across central Iowa.
Of course, this Friday morning MCS will be dependent on how
mesoscale features evolve overnight, meaning the exact path and
evolution will be heavily dependent on how this afternoon plays
out. Regardless, the signal and environment is there for a
complex of storms to pass through the state.

Assuming the morning MCS comes to fruition, conditions will likely
stabilize some through Friday morning. However, the overall
environment generally remains unchanged with strong theta-e
advection continuing. Atmospheric recovery is expected through the
day and more thunderstorm activity will likely develop into Friday
afternoon, especially if there are any leftover outflow boundaries
and/or mesoscale circulations over Iowa. Instability and shear will
once again be sufficient for a few strong to severe storms capable
of producing damaging winds and hail, as well as a brief tornado
along any boundaries that set up. Likewise, the high precipitable
water environment will promote heavy rain. This risk looks to shift
farther south than today's, but any areas or basins that receive
multiple rounds of rainfall could be at risk of isolated flash
flooding and/or rises on creeks and rivers.

In addition to the thunderstorm chances, heat indices will once
again approach the upper 90s to near 100. However, convective debris
leftover from the overnight storms, as well as any additional
development, will likely help keep temperatures cooler over much of
Iowa on Friday. Therefore, have decided to only extend the far
southern portions of the Extreme Heat Warning across southern Iowa
through Friday. It will still be muggy, but likely not to the
extremes of earlier this week.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 407 PM CDT Thu Jul 2 2026

The synoptic pattern begins to transition to a more zonal flow
pattern through the day Friday and into the weekend. This generally
keeps the warm and moist conditions going through the weekend,
although some reprieve may be on the horizon. Models are currently
depicting a shortwave passing through the state Friday night into
Saturday morning, bringing another MCS across Iowa. This system will
likely ride along the mesoscale boundary/instability gradient
(similar to tonight's), which will likely be farther south in the
state. As this occurs, damaging winds and heavy rainfall will
accompany it, again bringing severe weather and flash flood concerns
Friday night into the morning of Independence Day. However, with the
less persistent synoptic pattern, conditions seem to stabilize at
least through the day on Saturday. The boundary will be pushed
either into southern Iowa or northern Missouri, acting as the focal
point for redevelopment on the afternoon and evening of Independence
Day. Therefore, the southerly extent of the Friday night into
Saturday morning storms may be able to spare much of Iowa from storm
chances later in the day Saturday. This would also lead to slightly
cooler conditions, albeit still warm in the upper 80s. There is
still a lot to happen between now and then, so stay tuned to the
forecast for the latest on the Independence Day forecast! Warm and
humid conditions then persist into the end of the weekend and early
next week, although still not to the extremes of the beginning of
this week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 636 PM CDT Thu Jul 2 2026

Have maintained TEMPO and Prob30 groups in the short term for
lingering thunderstorms. Have kept Prob30 at KDSM at initial
issuance due to uncertainty in an outflow boundary reaching the
terminal. It continues to form thunderstorms just north of the
terminal. Have refined timing for a line of storms forecasted to
arrive after 06 from the west. Uncertainty in severe potential,
and have changed to SHRA mentions as it moves southeast. Highest
likelihood for storms tomorrow will be in peak heating times
similar to today (after 20z) with placement most likely at KDSM
and KOTM. Will reflect with mentions once confidence increases.

&&

.HYDROLOGY...
Issued at 407 PM CDT Thu Jul 2 2026

Flash flood and river flood concerns exist over at least the next
couple days due to heavy rainfall potential mentioned above.
Greatest concerns are across northern Iowa mainly coincident with
the flash flood watch. Main flash flood concerns would be in
cities and towns. Soil moisture in some areas has significantly
increased due to heavy rain over the past couple days. Additional
rainfall combined with relatively short soil recovery times may
lead to more runoff than we have recently seen, especially if it
falls in those areas, increasing the flash flood risk to within
flash flood watch criteria. Lower risk of flash flooding exists
farther south into central Iowa. Ponding looks to be the most
likely outcome at this time. If flash flooding occurred then it
would again be most likely in cities and towns.

Flash flood concerns continue into Friday with more heavy rain
possible. Confidence is relatively low in exact placements and
amounts. If the weather evolves tonight as expected then the
greatest risk on Friday would likely be along and north of the US
30 corridor, with lower risk farther south again.

River flooding would tend to be a longer term concern, depending on
heavy rain evolution over the next couple days. National Water
Model, HEFS and QPF ensemble hydrograph output suggest the most
likely scenario would be minor to significant within-bank rises on
many streams north of US 30, with a couple locations possibly
seeing minor flooding. If rainfall is higher than expected then
locally higher river levels would be possible.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Friday morning for IAZ004>007-015>017-
023>028-033>039.
Extreme Heat Warning until 10 PM CDT this evening for
IAZ059>062-072>075-082-083.
Extreme Heat Warning until 10 PM CDT Friday for IAZ084>086-
092>097.

&&

SHORT TERM...Dodson
LONG TERM...Dodson
AVIATION...Jimenez
HYDROLOGY...Zogg

Hazardous Weather Outlook
National Weather Service Des Moines IA
312 PM CDT Thu Jul 2 2026

IAZ044>050-057-058-070-071-081-032015-
Crawford-Carroll-Greene-Boone-Story-Marshall-Tama-Audubon-Guthrie-
Cass-Adair-Adams-
312 PM CDT Thu Jul 2 2026

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

Warm and humid conditions continue this afternoon. There is a
Slight (Level 2 of 5) Risk for severe storms from this afternoon
into evening, and again overnight.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

There is an Enhanced (Level 3 of 5) to Slight (Level 2 of 5) Risk
for Severe Storms on Friday with multiple rounds of storms
possible from the morning through the evening.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed at times tonight into Friday.

IAZ004>007-015>017-023>028-033>039-032015-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun-
Webster-Hamilton-Hardin-Grundy-Black Hawk-
312 PM CDT Thu Jul 2 2026

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

A Flood Watch is in effect for the area. Please refer to the
National Weather Service website at weather.gov/desmoines for
further details.

There is a Slight (Level 2 of 5) Risk for severe storms from this
afternoon into evening, and again overnight.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

There is an Enhanced (Level 3 of 5) to Slight (Level 2 of 5) Risk
for Severe Storms on Friday with multiple rounds of storms
possible from the morning through the evening.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed at times tonight into Friday.

IAZ084>086-092>097-032015-
Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-Appanoose-
Davis-
312 PM CDT Thu Jul 2 2026

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

An Extreme Heat Warning is in effect for the area. Please refer
to the National Weather Service website at weather.gov/desmoines
for further details.

There is a Marginal (Level 1 of 5) Risk for severe storms from
this afternoon into evening, and again overnight.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

An Extreme Heat Warning is in effect for the area through Friday
night. Please refer to the National Weather Service website at
weather.gov/desmoines for further details.

There is a Slight (Level 2 of 5) Risk for Severe Storms on Friday
with multiple rounds of storms possible from the morning through
the evening.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed at times tonight into Friday.

IAZ059>062-072>075-082-083-032015-
Dallas-Polk-Jasper-Poweshiek-Madison-Warren-Marion-Mahaska-Union-
Clarke-
312 PM CDT Thu Jul 2 2026

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

An Extreme Heat Warning is in effect for the area into tonight.
Please refer to the National Weather Service website at
weather.gov/desmoines for further details.

There is a Slight (Level 2 of 5) to Marginal (Level 1 of 5) Risk
for Severe Storms this afternoon into evening, and again
overnight.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

There is a Slight (Level 2 of 5) Risk for Severe Storms on Friday
with multiple rounds of storms possible from the morning through
the evening.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed at times tonight into Friday.

Preliminary Local Storm Report
National Weather Service Des Moines IA
725 PM CDT Thu Jul 2 2026

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

0723 PM     Rain             Grundy Center           42.36N 92.77W
07/02/2026  M5.50 Inch       Grundy             IA   Broadcast Media

            KWWL shared a viewer report of 5.5 in of
            rainfall so far in Grundy Center since 2pm.

&&

Fowle

Preliminary Local Storm Report
National Weather Service Des Moines IA
755 PM CDT Thu Jul 2 2026

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

0754 PM     Rain             2 N Morrison            42.37N 92.67W
07/02/2026  M4.18 Inch       Grundy             IA   Mesonet

            Storm total precipitation from a personal
            weather station.

&&

Fowle

Preliminary Local Storm Report
National Weather Service Des Moines IA
756 PM CDT Thu Jul 2 2026

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

0756 PM     Rain             4 S Grundy Center       42.30N 92.78W
07/02/2026  M4.12 Inch       Grundy             IA   Mesonet

            Storm total precipitation from a personal
            weather station.

&&

Fowle

Preliminary Local Storm Report
National Weather Service Des Moines IA
757 PM CDT Thu Jul 2 2026

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

0757 PM     Rain             2 S Hudson              42.40N 92.45W
07/02/2026  E4.46 Inch       Black Hawk         IA   Mesonet

            Storm total precipitation from a personal
            weather station.

&&

Fowle

Preliminary Local Storm Report
National Weather Service Des Moines IA
758 PM CDT Thu Jul 2 2026

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

0758 PM     Rain             1 SSE Reinbeck          42.31N 92.59W
07/02/2026  M3.99 Inch       Grundy             IA   Mesonet

            Storm total precipitation from a personal
            weather station.

&&

Fowle

Preliminary Local Storm Report
National Weather Service Des Moines IA
803 PM CDT Thu Jul 2 2026

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

0803 PM     Rain             1 S Hudson              42.40N 92.46W
07/02/2026  E4.00 Inch       Black Hawk         IA   Broadcast Media

            KWWL shared an image with 4 in of rainfall
            in Hudson.

&&

Fowle