Severe Thunderstorm Warning 269, NWS Quad Cities, IA

Area Forecast Discussion
National Weather Service Quad Cities IA IL
612 AM CDT Thu Aug 13 2026

...12z Aviation Update...

.KEY MESSAGES...

- Areas of Dense fog this morning, another MCS rolling in from
  the west this morning with potential severe weather, and more
  storms tonight with flash flooding/flooding becoming more in
  the spotlight.

- The active weather pattern will bring a daily risk of showers
  and thunderstorms Friday and through the weekend. HOWEVER,
  there will be and many hours of dry weather each day.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 315 AM CDT Thu Aug 13 2026

Light sfc winds and a juiced boundary layer making for some fog
problems early this morning until more clouds and precip arrive from
the west. Fog Advisory issued. Now eyes turn to the convectively
enhanced short wave out acrs NE and associated convective complex
of storms out that way. Propagation vectors and optimal thermal
tracks bring this feature acrs the DVN CWA mid to late morning.
Still some MLCAPE of 1500-2500 J/kg to work with but shear not as
strong as the last two mornings and quite an EML to overcome for
more sfc rooted behavior. But a later morning arrival and wave
associated shear may help and still see a damaging wind threat of 60-
70 MPH posssible as well as a few embedded tornadoes. A 2 inch PWAT
feed will also fuel heavy rain at heavy rainfall rates thus the
flooding risk is going up. Have issued a Flood Watch for the south
half of the DVN CWA starting this morning to cover the brunt of the
passing MCS banking on the more intense part of it moving along and
south of I-80. But then having the watch go tonight into Friday
midday as well for additional bouts of heavy rain and thunderstorms
with a 2+ inch PWAT feed and airmass in place.

For most of the north half of the DVN CWA, started the flood watch
tonight and continue it through the same end time of 18z Friday.
These areas may get clipped by not quite as heavy rain this
morning/midday, have a partial break for the rest of the afternoon
and early evening before the convergent nocturnal LLJ kicks in and
ignites more thunderstorms along thermal gradients or lingering
boundaries. Feed and shear profiles supports repeated storm
development and back-building along linear segments tonight, and
with a 2 inch PWAT airmass this spells swaths of flash flooding
trouble. For now reluctantly left out the Hwy 20 corridor from the
flood watch with still ongoing uncertainty where the main line or
lines of storms lay out, but after assessment later today there may
be the eventual need to add these counties to the watch as well. The
north may switch positions with the south as several of the latest
CAMs have little overnight activity south of I-80.

Although still muggier than a dog's mouth today, with east winds and
convective debris will limit the need for any heat headlines at this
point.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 315 AM CDT Thu Aug 13 2026

Friday...There may be some lingering flooding problems in the
morning, but convective coverage should be diurnally waning into the
midday. Boundary placement should make for high temp variance from
the upper 70s north, to the upper 80s in the far south. Timing the
next ridge-riding short wave may bring yet another MCS in from the
west by late afternoon and into Friday evening. This would bring
more damaging wind threats as well as more heavy rain to a
potentially water sensitive CWA and there may be a need of another
flood watch. Area creeks and rivers could be really on the rise at
that time as well, will have to keep the hydrological aspects more
in mind as well as the severe risks.

Saturday through Wednesday...Latest ensemble and upper jet trends
suggest the upper ridge and heat dome to get pressed eastward
temporarily maintaining the ring of fire for the weekend with the local
area dangerously near the periphery through at least Sunday. Storm
chances will continue as well as a hot humid Saturday in store, but
then some signs early next week of upper ridge retro-grade allowing
for more of a northwest flow push down the upper MS RVR Valley. A
resultant drier and cooler Monday would be much welcome by then.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 605 AM CDT Thu Aug 13 2026

A challenging TAF cycle with areas of fog and low stratus
trending into an incoming large severe MCS from the west by mid
morning, then more storms along some axis from west-to-east
tonight. The MCS will have the associated hazards and potential
high wind gusts. After the MCS passage, some of the afternoon
there may be a precip lull window or a lingering linear line low
coverage west-to-east of showers/storms somewhere. Later
tonight with nocturnal LLJ kicking in along LLVL remnant
boundaries, there could be bands of persistent thunderstorms and
be a big impact if they camp out over a TAF site or two with
heavy rain. Away from the variable gusts of the thunderstorms,
with the main sfc boundary shunted to the south, the ambient
winds will be generally from the east or have some easterly
component for much of the TAF period.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flood Watch from this evening through Friday afternoon for
     IAZ051>054-063>068.
     Dense Fog Advisory until 9 AM CDT this morning for IAZ053-054-
     064>068-076>078-087>089-098-099.
     Flood Watch through Friday afternoon for IAZ076>078-087>089-
     098-099.
IL...Flood Watch from this evening through Friday afternoon for
     ILZ007-009-015>018.
     Dense Fog Advisory until 9 AM CDT this morning for ILZ001-002-
     007-009-015>018-024>026-034-035.
     Flood Watch through Friday afternoon for ILZ024>026-034-035.
MO...Dense Fog Advisory until 9 AM CDT this morning for MOZ009-010.
     Flood Watch through Friday afternoon for MOZ009-010.

&&

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

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
502 AM CDT Thu Aug 13 2026

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-141100-
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-
502 AM CDT Thu Aug 13 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

Areas of dense fog reducing visibility down to a quarter mile or
less will last through 8 AM before clouds and thunderstorms move
in from the west. A Dense Fog Advisory is in effect for most of
the Outlook Area this morning.

A strong to severe storm system will move in from the west and
impact much of the Outlook Area this morning through midday.
Damaging winds, potentially up to 70 mph, will be the primary
risk. Brief spin-up tornadoes will be a secondary risk. Areas
along and south of the Highway 30 corridor are in a Slight Risk,
level 2 out of 5, for severe storms today. Locally heavy rainfall
and flash flooding will also be a concern.

More thunderstorms are expected to develop tonight. With the
potential for lines of storms to repeatedly develop and move
across the same areas, the primary concern tonight will be
torrential rainfall and flash flooding. Isolated severe storms
with damaging winds and hail will also still be possible. Most of
the Outlook Area is in a Flood Watch today through midday Friday.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

Rounds of strong to severe storms will be possible Friday and
Saturday as the area remains in an active storm track. There is a
Marginal Risk, level 1 of 5, for severe storms both days for much
of the area. Locally heavy rain and flash flooding will also be a
concern, especially Friday night if storms move across areas
already soaked from previous bouts of heavy rainfall.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is likely today and possible tonight.

12