Severe Thunderstorm Warning 247, NWS Quad Cities, IA

Area Forecast Discussion
National Weather Service Quad Cities IA IL
638 AM CDT Tue Aug 11 2026

.KEY MESSAGES...

-  A storm system(QLCS)may still be on track to propagate southeastward
   down across portions of the local area(more likely areas
   along/north of I-80)this morning and midday. Damaging wind is
   the still the primary risk, with a secondary risk of brief
   spin-up tornadoes. Much of the area remains in a Slight to
   Enhanced(levels 2 and 3 out of 5)Risk today. Strong to severe
   storms will be possible again on Wednesday.

- A Heat Advisory remains in effect for areas along/south of an Ottumwa,
  IA to Galesburg, IL line. Storm clouds and outflow may
  prevent it to be needed further north but it will still be
  very humid north of the advisory.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 245 AM CDT Tue Aug 11 2026

The latest sfc analysis continues to indicate a west-to-east oriented
quasi-stationary frontal boundary acrs central IA into northern IL,
with rather light sfc flow going on around it making for another
morning with patchy to areas of fog. Isolated to sctrd elevated WAA
showers and a few thunderstorms are occurring north of the LLVL
front acrs the north half of IA into WI even with a west-southwest
veering H85 MB jet. Profiler network showing better southwesterly
LLJ of 35-40 KTs converging on the MO RVR Valley, just to the lee of
a seasonably robust short wave upper trof seen on water vapor
imagery digging acrs eastern SD/southwest MN ATTM. This should be
the region for MCS generation this morning, with a few storm
clusters already occurring there.

Tightening CAPE and THTA-E gradient and prime H85 20C thermal ribbon
align from southeast SD/ southwest MN down along to north of the
local I-80 corridor through midday, and that's the currently
expected path of an eventual MCS or QLCS type convective feature
feeding on the LLJ jet that should be getting shunted this way ahead
of the short wave as well as a mid level jet max. If this convective
system can organize with a cold pool and mix along at least a 3000
J/kg MLCAPE pool at that time of morning, feel the already 70 KT+
wind gust potential could be there. Several of the latest CAM runs
continue to target the highest wind gusts and bow apex along the Hwy
20 corridor and areas along the northern CWA border from around 10
am to noon or so. Some uncertainty on this, as a southwest tailing
bow structure may also bring damaging winds down toward the I-80
corridor.

As this feature exit by early afternoon, it's cool pool outflow
could very well shunt the main boundary further southward again with
lingering convergence and diurnal heating help produce sctrd showers
and a few thunderstorms in the wake of the main complex until the
short wave can get by. Then would expect little convective activity
by late afternoon and into the evening period as short wave ridging
bulges overhead. Much of tonight may then be quiet until late toward
dawn Wed when heights start to fall again and some LLVL jet
convergence can maybe initiate some isolated showers and storms
along or north of the southward shunted LLVL boundary acrs south
central IA into the southern CWA. These may fester and last well
into Wednesday with some severe risk if even somewhat elevated.
Locally heavy rainfall and flooding may become more of a factor into
Wed as well where the axis of storms can fire...right now it looks
acrs the southern CWA.

As for the Heat Advisory, will let it ride and not expand it north
with worries that this morning storms, debris and outflow will limit
the ambient temps along and north of I-80 enough to fall short of
advisory criteria. But it will still be oppressively humid, and if
the MCS track further to the north than currently expected it may
indeed need to be expanded north.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 245 AM CDT Tue Aug 11 2026

Wednesday...Talked a little bit about Wed above with some morning
convection possible. But then it currently appears that the local
area will lay in between the more organized forcing again for a
potentially low activity period until maybe toward Thu morning
when the next main short wave may be approaching. Also Wed will
be another hot and humid day especially if convection is more
scarce and can't rule out the eventual need of a heat headline
for portions of the area.

Thursday through Monday...If the currently extrapolated short wave
train along the edge of the heat dome is in the ballpark, we may
have another MCS moving into the local area Thu morning with severe
weather and heavy rain risks. The temperature battle will continue
as well with LLVL baroclinicity and thermal ribbon wavering acrs the
region for high heat or not so bad depending on the daily flux.
Rainfall amounts may really add up by the weekend and early next
week on the northern fringe of the heat dome from the west central
plains, acrs IA/IL, and curving down acrs the eastern OH RVR Valley.
Will have to watch the Thu through Friday period for heavy rain and
back building MCS potential depending on LLVL boundary and
convergent flow axis's lay out if long range 2 inch PWAT feed
indicators are accurate.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 638 AM CDT Tue Aug 11 2026

An area of showers and thunderstorms over central IA is on the
doorstep of the terminals this AM. These storms are expected to
slide through the terminals through approximately 17z, bringing
a period of IFR visibilities and IFR/MVFR ceilings, together
with strong wind gusts up to 45kts. For now, it appears the
storms are most likely to affect KCID, KDBQ and KMLI with the
worst conditions, which has been handled with a TEMPO group.
KBRL will get a shorter time period of not quite as poor
conditions, which has been handled with a PROB30 group. Once
these storms move through, most of the rest of the TAF forecast
will be VFR with west to southwest wind of less than 10kts. Fog
becomes a concern after 08z tonight, and have included some MVFR
fog for each terminal.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Heat Advisory from noon today to 8 PM CDT this evening for
     IAZ087>089-098-099.
IL...Heat Advisory from noon today to 8 PM CDT this evening for
     ILZ025-026-034-035.
MO...Heat Advisory from noon today to 8 PM CDT this evening for
     MOZ009-010.

&&

SHORT TERM...12
LONG TERM...12
AVIATION...NWS

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
413 AM CDT Tue Aug 11 2026

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-121100-
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-
413 AM CDT Tue Aug 11 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

A storm complex, likely severe, will impact areas mainly
along and north of Interstate 80 this morning. Damaging winds,
potentially over 70 mph, will be the primary risk. Brief spin-up
tornadoes will be a secondary risk. Much of the area is in a
Slight to Enhanced, levels 2 and 3 out of 5, Risk for severe
storms.

A Heat Advisory remains in effect for areas generally along and
south of an Ottumwa, Iowa to Galesburg, Illinois line this
afternoon and evening.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

Rounds of strong to severe storms will again be possible Wednesday
and Thursday as the area continues to lay under an active storm
track. There is a Marginal, level 1 out of 5, Risk for severe
weather for the portions of the Outlook Area both days. Locally
heavy rain and flooding will also be a concern.

There will continue to be an almost daily chance for thunderstorms
into the upcoming weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is likely today.

12

Special Weather Statement
National Weather Service Quad Cities IA IL
503 AM CDT Tue Aug 11 2026

IAZ041-042-053-054-066-ILZ001-002-007-009-111445-
Delaware-Dubuque-Jones-Jackson-Clinton-Jo Daviess-Stephenson-
Carroll-Whiteside-
Including the cities of Manchester, Dubuque, Anamosa, Maquoketa,
Clinton, Galena, Freeport, Mount Carroll, and Sterling
503 AM CDT Tue Aug 11 2026

...Areas of Fog This Morning...

Areas of fog, some locally dense with visibilities under one half
mile, can be expected through the morning commute.

Motorists should exercise caution this morning, especially during
the morning commute, as visibilities may change suddenly over very
short distances.

This fog is expected to decrease through 8 and 9 AM as showers and
thunderstorms increase and move into the area.

12

Special Weather Statement
National Weather Service Quad Cities IA/IL
508 AM CDT Tue Aug 11 2026

IAZ040-051-052-111045-
Linn IA-Buchanan IA-Benton IA-
508 AM CDT Tue Aug 11 2026

...A strong thunderstorm will impact portions of northwestern Linn,
southwestern Buchanan and northern Benton Counties through 545 AM
CDT...

At 507 AM CDT, Doppler radar was tracking a strong thunderstorm near
La Porte City, or 11 miles southeast of Waterloo, moving east at 50
mph.

HAZARD...Nickel size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to outdoor objects is possible.

This strong thunderstorm will be near...
  Mount Auburn around 515 AM CDT.
  Brandon around 520 AM CDT.
  Urbana around 525 AM CDT.

Other locations in the path of this storm include Center Point.

This includes Interstate 380 between mile markers 31 and 55.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4230 9230 4230 9207 4239 9206 4229 9163
      4206 9174 4225 9230
TIME...MOT...LOC 1007Z 290DEG 41KT 4234 9226

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...<40 MPH

Gross