Tornadoes and Flash Flooding in Iowa, June 17, 2026

Area Forecast Discussion
National Weather Service Quad Cities IA IL
219 AM CDT Wed Jun 17 2026

.KEY MESSAGES...

- Slight/Enhanced Risk (level 2/3 of 5) for severe storms early
  this morning around sunrise, lasting through mid morning.The
  primary threat with these storms will be large to very large
  hail.

- Late this morning and through the afternoon, much of the area
  will have a threat for more severe storms, with the whole
  area under a severe threat ranging from a Slight Risk (level 2
  of 5) in our northwest to a Moderate Risk (level 4 of 5) in
  our extreme southeast/east.

- High moisture content over the area will allow for heavy
  rainfall with any storms through today. Flash flooding will be
  possible in areas that see repeating rounds of storms,
  especially in areas that recently saw heavy rainfall. Flood
  Watch remains in effect for areas in West-Central Illinois.

- Quiet weather will be seen through the second half of the
  work week, with the pattern becoming active again this weekend
  and beyond.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 215 AM CDT Wed Jun 17 2026

Severe weather is expected today as a seasonably strong system moves
through the region. This will bring two rounds of storms to eastern
Iowa, northwest Illinois, and northeast Missouri: a first round
in the morning hours (4-9 AM) and second round in the afternoon
hours (12-7 PM). Morning storms are anticipated to have a
primary threat of large hail and low damaging wind potential,
while afternoon storms will be capable of all hazards, including
tornadoes. In addition, heavy rain will lead to localized flash
flooding, especially in areas that see repeated rounds of
storms.

A strong shortwave will move from the Northern Plains into the Upper
Midwest this morning. Pressure heights are near or at the NAEFS
climatological minimum for mid-June, while winds aloft are near or
at their maximum. This can be seen in a strong (50-60 kts) zonal jet
at 500 mb sampled upstream with today's 00Z soundings. As this
system translates into the Upper Midwest early this morning,
southerly to southwesterly flow across the central Plains will
provide warm air advection and moisture, which will amplify with the
LLJ towards sunrise. As a result, dewpoints are forecast to rise
into the mid to upper 60s within a few hours after sunrise, creating
a sharp gradient between the northern and southern halves of
the CWA. Lift along this WAA wing will provide the focus for
morning convection, with showers and storms across the area.

For the morning, the greatest risk for severe storms is along and
south of Interstate 80, though there is some uncertainty given a
strong cap over the region. If storms are able to develop, shear
magnitude and direction suggests a mixed storm mode with multicell
and supercells storms. A favorable severe environment of high lapse
rates (7.5-8.5 degC/km) and up to 2000 J/kg of MUCAPE will support a
primary risk of large hail. In addition to the risk of large hail,
heavy rain will be possible with these these storms. This should be
a soaking rain this morning and flash flooding threat should be
limited, save for areas that have a long residence time with storms.
This would primarily occur with cells that move over the same areas,
as storms in this first round will be moving quickly towards the
east at 40-50 kts.

By mid- to late morning, these storms will move east into central
Illinois, giving the airmass time to recover. At this point, strong
southwesterly flow will continue to feed in moisture and
instability, providing the energy necessary for the second round of
storms. The greatest area of uncertainty is in how much recovery
time will be possible, as morning storms and showers could persist
longer than anticipated. If the atmosphere is able to recover
following morning storms, an environment favoring supercells will
develop, leading to the potential for all hazard severe
thunderstorms.

Around 12 PM, forcing along the cold front will plow into a region
of 2000 (north) to 4000 (south) J/kg of CAPE, providing the forcing
necessary for convective initiation. These storms will be fast
moving, with a storm motion of 50 kts to the east. Large hail and
damaging winds are possible with all storms. Tornado threat will be
more limited, with the best low level shear supporting the highest
tornado threat in west-central Illinois. These storms will exit into
central Illinois around 6-7 PM.

Once these storms move off to our east, CAA advection behind the
front will support westerly to northwesterly winds up to 20-25 mph,
leading to a breezy night.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 215 AM CDT Wed Jun 17 2026

Several pleasant, mainly dry days will follow our big system today.
This will lead to temperatures below normal for highs and lows
Thursday and Friday.  Dry air should keep any rain threat low,
though some energy skirting by aloft could bring some sprinkles
or even a tiny thunderstorm as early as Friday night.

Warm begins to spread northward again towards Saturday, as the flow
aloft shifts towards a more active zonal flow regime. Models remain
consistent in showing a warm front developing over the Midwest
Saturday night, and having at least one significant wave of
rain and thunderstorms/ potentially an MCS Sunday and Sunday
night. There is latitude differences in the latest
deterministic guidance, with the GFS shifting that axis a bit
south, and the EC and GEM maintaining a more northerly frontal
zone. Regardless, that will be the next period for us to focus
on for both heavy rainfall and a thunderstorm risk.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1210 AM CDT Wed Jun 17 2026

A fast moving storm system will bring a quick transition from
VFR with light winds to thunderstorms with very strong winds
aloft (LLWS) towards morning. Storms are expected to rapidly
form in eastern Iowa between 09z and 12Z, then spread quickly
southeast and east through the rest of the area. These storms
will move quickly, produce lots of lightning, hail, and gusty
winds, in addition to IFR conditions in the storms. This period
of widespread storms will extend towards 18z, especially along
and north of Interstate 80 Wednesday. More isolated coverage,
but intense storms are possible in the afternoon, mainly at MLI
and BRL, (south of I-80). These storms could also produce
damaging winds, hail, and some tornadoes as well. Quick movement
to the east should limit the duration of impact to aviation,
with a breezy, but largely VFR evening expected behind the
afternoon storm threat.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...Flood Watch from 7 AM CDT this morning through this evening
     for ILZ009-016>018.
MO...None.

&&

SHORT TERM...Ellingworth
LONG TERM...Ervin
AVIATION...Ervin

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
321 AM CDT Wed Jun 17 2026

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-180830-
Buchanan-Delaware-Dubuque-Benton-Linn-Jones-Jackson-Iowa-Johnson-
Cedar-Clinton-Muscatine-Scott-Keokuk-Washington-Louisa-Jefferson-
Henry IA-Des Moines-Van Buren-Lee-Jo Daviess-Stephenson-Carroll-
Whiteside-Rock Island-Henry IL-Bureau-Putnam-Mercer-Henderson-
Warren-Hancock-McDonough-Scotland-Clark-
321 AM CDT Wed Jun 17 2026

This Hazardous Weather Outlook is for portions of north central
Illinois...northwest Illinois...west central Illinois...east
central Iowa...northeast Iowa...southeast Iowa and northeast
Missouri.

.DAY ONE...TODAY AND TONIGHT

The Wapsipinicon River is experiencing flooding. Please see the
latest Flood Statements and Flood Warnings for details.

A strong system will bring the potential for severe thunderstorms
today. A Moderate, level 4 of 5, risk is forecast for central
Illinois, with an Enhanced, level 3 of 5, risk of severe
thunderstorms south of Highway 30 and the remainder of the area
under a Slight, level 2 of 5, risk. The first round of thunderstorms
will continue through late morning today, with a primary risk of
large hail. After 12 PM, a second round of thunderstorms is expected
along and ahead of the cold front, with all severe weather hazards
possible, including tornadoes. Localized flash flooding will be
possible during both rounds, especially in areas that see multiple
rounds of storms.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

The next chance for thunderstorms will be Sunday and Sunday night.

.SPOTTER INFORMATION STATEMENT...
Spotter activation is expected this morning and this afternoon.

Ellingworth/Ervin