Severe Thunderstorm Warning 39, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
140 PM CDT Tue Apr 14 2026

.KEY MESSAGES...

- Scattered severe storms (Level 3 of 5) this afternoon and
  evening. All severe weather hazards remain possible. More
  widespread storms and locally heavy rainfall expected tonight,
  especially over the southern half of Iowa, but with a lower
  severe weather threat overall.

- Additional rounds of severe storms and locally heavy rainfall
  still expected on Wednesday afternoon and evening, and again
  on Friday afternoon and evening. Details on those events will
  be fine tuned in subsequent updates.

- Warm and breezy today through Friday with highs in the 70s and
  80s. Much cooler readings in the 40s and 50s by this weekend,
  with a hard freeze likely north Saturday night.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 140 PM CDT Tue Apr 14 2026

A broad 500 MB trough is moving over the U.S. Rockies today, and is
not well coalesced with several vorticity maxima strung out along
its loose axis. Ahead of the trough, Iowa remains beneath
southwesterly steering flow resulting in, relative to the season,
warm and quite humid conditions across the state. A surface low
pressure center is slowly developing ahead of the 500 MB trough,
near the Colorado/Kansas border, with a nearly stationary front
extending northeastward over roughly the northern half of Iowa.
Satellite imagery shows agitated cumulus clouds developing along
and near the frontal zone, and forecast soundings indicate a
weakening EML in place that could break at any time. All CAMs
initiate convection and form scattered thunderstorms within the
next couple hours, most likely near the front roughly north of
I-80. Instability is seasonally strong with SBCAPE in excess of
3000 J/KG south of the boundary, and impressive bulk shear
values of 40-60 KT are overspreading the area. Wind profiles do
show somewhat unidirectional flow in most of the column so this
is nearly all speed shear, which mitigates the tornado threat
somewhat. Nevertheless, surface-based convection is likely to
initiate very soon and continue into the evening. Tornadoes will
be possible in any localized backed flow or storms with deviant
motion, most likely near the frontal boundary. In addition, any
storms will be capable of large hail given the relatively cool
mid-levels, strong speed shear, and impressive instability, and
the stronger winds aloft will be easy to transport down to the
surface with any cold pools. Thus, all modes of severe weather
will be possible with the storms this afternoon and early
evening.

Later this evening and tonight, a subtle shortwave impulse will
eject out of the broader approaching trough and move across
northern Missouri and Iowa, in conjunction with a developing
nocturnal low- level jet. This will provide the impetus for
renewed convection tonight, with scattered to numerous showers
and thunderstorms especially over the southern two thirds or so
of Iowa. Several high- res model solutions indicate that the
surface frontal boundary will be lingering in our southeastern
counties this evening, roughly south of a Creston to Grinnell
line, with instability pooling along it and modest convergence
providing extra focus for initiation. As a result, these
solutions depict stronger thunderstorms developing in that area,
with forecast soundings indicating strong instability and deep-
layer shear supportive of large hail and damaging wind gusts.
This threat should be confined to areas near and south of the
boundary, with instability waning rapidly to the north toward
central Iowa.

On Wednesday the broad trough over the Rockies will kick out
eastward into the Midwest, with the associated surface low gradually
tightening up and moving northeastward to near the Nebraska/Iowa
border by the evening. Within the warm sector ahead of and wrapping
into the surface low, instability will likely increase
significantly during the day. However, there is considerable
uncertainty in convective timing and evolution due to the
after-effects of overnight storms tonight. In fact, many 12Z
model runs from this morning depict additional redevelopment of
elevated storms mid-to-late Wednesday morning, which would
carry some threat of large hail per forecast soundings and
further complicate the forecast for the afternoon and evening.
Even so, the degree of destabilization during the afternoon
should support more rigorous development later in the day, and
once again strong instability and deep-layer shear may be very
supportive of a severe weather threat. This will be particularly
true as the surface low and triple point approach from the west
late Wednesday afternoon/early evening, with backing flow and
boundaries tied into the low supporting some enhancement of the
tornado threat. These storms will surge eastward out of our
forecast area by late evening, though a few weaker storms may
develop later, in association with the main 500 MB trough moving
through, around Wednesday night.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 1239 PM CDT Tue Apr 14 2026

On Thursday a weak ridge will move through Iowa, providing a
most welcome respite in the form of a dry, mostly sunny, and
mild day with highs roughly in the 75-80 degree range and modest
breezes. By Thursday night however, an even deeper longitudinal
500 MB trough will be moving into the Rockies, heralding more
active weather to end the week. A surface cyclone will develop
in the Southern High Plains with a long inverted trough and
sharp baroclinic zone extending northeastward across the
Midwest. By Friday morning this front will span from central
Kansas, across northwestern Iowa, and into western Wisconsin.
Destabilization will occur ahead of the front during the day
Friday, and by the afternoon CAPE of 1500-2500 J/KG is likely in
at least parts of our area, mainly the southern half. Deep-layer
shear will be fairly modest and mostly in the form of speed
shear, however the strong dynamic forcing ahead of the
approaching trough, convergence along the front, and increasing
instability will combine with this shear to be more than
sufficient to support severe weather potential Friday afternoon
and evening, as outlined by SPC outlooks.

The storm system will push quickly through Friday night and
clear us out, though there may be some light wraparound
precipitation in our northern counties lingering into Saturday
as the final lobe of the 500 MB trough moves by. With much
colder air surging in behind the late Friday front and
temperatures expected to fall into the 30s across much of our
area by early Saturday, a few flakes of snow cannot be ruled out
in northern Iowa but no real accumulation or impact would be
expected. Highs on Saturday will be nearly 30 degrees cooler
than on Friday, ranging in the mid-40s to mid-50s, then falling
even further Saturday night into Sunday morning with lows in the
upper 20s to mid-30s across Iowa resulting in a frost/freeze in
many areas. The good news is this cooler weather will be short-
lived, as a ridging pattern sets up in the first half of next
week supporting a gradual warming trend.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1236 PM CDT Tue Apr 14 2026

Cumulus clouds are developing across much of the area this
afternoon and will produce periods of MVFR ceilings in the next
few hours, mainly at FOD/MCW/ALO, before rising to VFR. In
addition, scattered thunderstorms are forecast this afternoon
and evening, then later tonight into Wednesday morning.
Confidence in timing and placement is low, but warrants PROB30
groups during the most likely time windows at each terminal.
Lowered ceilings and visibilities and gusty winds will be
possible in and near any storms. Expect amendments and
refinements to the TAFs later today through tonight.

&&

.HYDROLOGY...
Issued at 119 PM CDT Tue Apr 14 2026

Multiple rounds of seasonally moderate to heavy rain this week will
lead to renewed flooding concerns. Concerns will include possible
renewed or additional river flooding as well as flash flooding.

Output from the GFS- and NBM-forced medium-range National Water
Model (NWM) and the Hydrologic Ensemble Forecast System (HEFS)
suggest the most likely scenario will be moderate to significant
within-bank rises on many rivers and streams across the CWA over the
next week, especially across the southeast half. Some locations may
see minor river flooding as well. These rises will be due to the
additive effect of multiple rounds of rainfall. If rainfall is
higher than presently forecast then the risk of several locations
seeing minor flooding and a few locations seeing moderate flooding
will increase.

Flash flooding is less of a concern than river flooding, however the
risk is nonzero. The additive effect of rain events will result in a
slightly higher risk of flash flooding from Friday into Saturday.
The most likely scenario through the end of this week will be
ponding of water or low-end flash flooding especially in urban areas
or areas that receive repeated heavy rainfall over a relatively
short time period.

&&

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

&&

SHORT TERM...Lee
LONG TERM...Lee
AVIATION...Lee
HYDROLOGY...Zogg

Hazardous Weather Outlook
National Weather Service Des Moines IA
616 AM CDT Tue Apr 14 2026

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-151400-
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-
616 AM CDT Tue Apr 14 2026

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

There is an Enhanced Risk (Level 3 of 5) for severe thunderstorms
across much of central through eastern Iowa later today into
tonight. Large hail, damaging winds, and tornadoes are all
possible.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

There is a Slight Risk (Level 2 of 5) for severe thunderstorms
across much Iowa on Wednesday. Large hail, damaging winds, and a
tornado or two are possible.

There will be additional chances for severe thunderstorms on
Friday. Specific details will be better resolved in the coming
days.

River flooding will also be possible this week as multiple rounds
of rainfall occur. Isolated flash flooding is also possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is possible later today.

Preliminary Local Storm Report
National Weather Service Des Moines IA
404 PM CDT Tue Apr 14 2026

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

0358 PM     Hail             5 N Allison             42.82N 92.80W
04/14/2026  E1.00 Inch       Butler             IA   Emergency Mngr

            Relayed by EM.

&&

MD/AA

Preliminary Local Storm Report
National Weather Service Des Moines IA
407 PM CDT Tue Apr 14 2026

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

0400 PM     Hail             Dike                    42.46N 92.63W
04/14/2026  E1.00 Inch       Grundy             IA   Trained Spotter

&&

TR/AA

Preliminary Local Storm Report
National Weather Service Des Moines IA
412 PM CDT Tue Apr 14 2026

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

0412 PM     Hail             1 W Cedar Falls         42.52N 92.47W
04/14/2026  E1.00 Inch       Black Hawk         IA   Public

&&

TR/AA

Preliminary Local Storm Report
National Weather Service Des Moines IA
415 PM CDT Tue Apr 14 2026

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

0414 PM     Hail             Greene                  42.90N 92.80W
04/14/2026  E1.75 Inch       Butler             IA   Emergency Mngr

&&

TR/AA

Preliminary Local Storm Report
National Weather Service Des Moines IA
420 PM CDT Tue Apr 14 2026

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

0415 PM     Hail             1 WSW Cedar Falls       42.51N 92.47W
04/14/2026  M1.00 Inch       Black Hawk         IA   Trained Spotter

&&

CAH

Preliminary Local Storm Report
National Weather Service Des Moines IA
421 PM CDT Tue Apr 14 2026

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

0421 PM     Hail             1 ENE Waterloo          42.50N 92.33W
04/14/2026  E1.75 Inch       Black Hawk         IA   Trained Spotter

&&

TR/CH