Severe Thunderstorm Warning 48, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
658 AM CDT Wed Apr 15 2026

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- Slight Risk for severe storms expended more to the west today.
  All modes of severe weather possible, with a locally higher
  tornado threat along the I-80 corridor.

- Enhanced Risk expanded for Friday, covering much of the
  eastern half of the state.

- Much cooler over the weekend with a hard freeze likely in
  northern Iowa Saturday night.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 312 AM CDT Wed Apr 15 2026

Showers and storms continued overnight, with the surface warm front
appearing to remain stalled diagonally across the center of the
CWA, seen best by the Td discontinuity between sites such as
KDSM and KBNW. Water vapor imagery showed the main circulation
for today traversing off the Rockies and into the High Plains. A
dry slot could be seen intruding into southeastern Nebraska,
with the surface dry line residing in Kansas. Showers and
isolated storms will continue to fester in the warm sector
through at least the early morning hours, fueled in part by the
interacting upper-level jet maxes. The southern jet max will
round into the warm sector later this morning, the wind field
below unidirectional and similarly enhanced. The dry slot will
move into Iowa ahead of the cold front this morning, increasing
capping and mid-level lapse rates. Trends have favored a lull in
precipitation around midday, opening the opportunity for
potential clearing ahead of the main severe window in the
afternoon. MLCAPE values will approach 1500 J/kg. Deep-layer
shear over 50kts will provide good ventilation for storms and
favor supercells, but low-level shear lacks today, reducing SRH
available for tornadoes. The exception will be near the triple
point as localized backing of surface winds will elongate
hodographs. 00z CAMs had consensus of a longer-lived UH streak
following the path of the triple point, with neighboring super
cells taking advantage of the NSE on the warm front. This will
be the region where the threat for tornadoes is the highest, and
have collaborated with SPC to add in a 5% tornado risk area,
focused along and near the I-80 corridor. A line of storms will
form along the cold front in southern Iowa and pose a wind
threat, although capping will allow for discrete modes to
start, adding in large hail and isolated tornadoes to the mix.
Cold front initiation will begin near the I-35 corridor.
Thunderstorms will follow the departure of the surface low and
be fueled mainly by the upper-level trough.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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 /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 658 AM CDT Wed Apr 15 2026

A few areas of thunderstorms remain mainly over portions of
central to southern Iowa this morning. Any remaining storms this
morning may move over KOTM and KFOD in in the next few hours,
with otherwise showers expected. Additional and more scattered
showers and storms are expected to develop this afternoon to
evening across much of the state, with severe weather possible
at times. Exact timing and coverage will be further refined in
the early afternoon update given latest trends. Low clouds are
expected otherwise to increase this morning otherwise, with
MVFR/IFR ceilings expected across all sites, while any storms
later in the day could also lead to similar conditions as well.
Winds will remain variable across the state given the boundary
draped across central Iowa, with some occasional gusts up to
20-25 mph possible, especially over southern Iowa.

&&

.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...Jimenez
LONG TERM...Lee
AVIATION...Bury
HYDROLOGY...Zogg

Hazardous Weather Outlook
National Weather Service Des Moines IA
411 AM CDT Wed Apr 15 2026

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-160915-
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-
411 AM CDT Wed Apr 15 2026

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

There is a Slight Risk (Level 2 of 5) for severe thunderstorms
across much of Iowa this afternoon and evening. Damaging winds,
large hail, tornadoes, and flash floods are all possible.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

There is an Enhanced Risk (Level 3 of 5) for severe thunderstorms
across much Iowa on Friday. Damaging winds and tornadoes are the
primary threats. Large hail is also possible.

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

Freezing temperatures are expected in northern Iowa Friday night
and across much of the area Saturday night.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is possible later today.