246
FXUS63 KDVN 150759
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
259 AM CDT Tue Sep 15 2026

.KEY MESSAGES...

- Active pattern to continue into the weekend with numerous
  rounds of showers and storms including heavy rainfall at
  times.

- There is Marginal Risk, Level 1 out of 5, for severe storms in
  west-central Illinois and south of Highway 34 this
  afternoon/evening. Isolated damaging winds is the primary
  hazard.

- An elevated flash flooding risk could develop mid-week with
  repeating rounds of storms. There is a medium to high chance
  (40-75%) for portions of eastern Iowa to see over 2 inches of
  rainfall, with localized areas of 4+ inches possible (5-10%),
  leading to rises on area creeks and streams.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 259 AM CDT Tue Sep 15 2026

Widespread showers and storms (80-100%) are expected this
morning along a cold front, mainly north of Highway 34. With the
shortwave trough and mid-latitude cyclone over south-central
Canada lifting to the northeast, a lot of the dynamical support
for the ongoing showers and storms will be lost, so the coverage
and intensity will gradually decrease throughout today,
especially north of I-80. Heading into tonight, the cold front
is forecasted to stall out over northern Missouri, keeping
scattered PoPs (30-60%) around south of I-80, as lows drop back
into the mid-50s and low 60s with the return to northeasterly
flow. There will be a short period late this afternoon/evening
where storms that develop along the cloud-enhanced theta-e
gradient could tap into 750-1250 J/kg of SBCAPE in west-central
Illinois and south of Highway 34. The SPC has highlighted this
area with a Marginal Risk, Level 1 out of 5, for severe storms
with isolated damaging winds as the primary hazard.

On Wednesday, a shortwave over the western CONUS will become cut off
from the main flow and pull weak disturbances in the jet stream
northward from the subtropics. With the stationary front
providing surface lift and the residual mid-level moisture from
today`s system, more scattered showers and storms (50-70%
coverage) are likely to redevelop along and north of this
boundary and persist into Wednesday night. If storms on
Wednesday track over the same areas that received over 1-2
inches of rainfall today, the flash flood risk could become
elevated, and this is noted by the WPC`s Slight Risk, Level 2
out of 4, for excessive rainfall areawide. By Thursday, a lobe
of mid-level vorticity moves into the central Rockies as
surface cyclogenesis occurs across eastern Colorado. While storm
coverage will be lower on Thursday (20-40%), the stationary
front across northern Missouri is forecast to convert into a
warm front, setting the stage for a wet start to the weekend.

In total through Thursday evening, rainfall totals will likely
(70-100%) range from 1-3 inches areawide outside of our far
southeast counties in west-central Illinois and northeast
Missouri. While these numbers are slightly lower than previously
forecasted, there is still a low chance (5-10%) for localized
areas across eastern Iowa to see 4+ inches of rainfall which
could lead to rises on small creeks and streams.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Issued at 259 AM CDT Tue Sep 15 2026

Friday-Saturday...The mid-level trough moves into the Dakotas and
Minnesota, dragging the Colorado low with it towards Iowa. A
WAA wing will likely develop along the warm front moving into
our CWA and force more scattered storms (50-70% coverage).
Muggy conditions are likely (60-90%) to return Friday into
Saturday with dew points back into the upper 60s and 70s
areawide. By Saturday, the low pressure slowly meanders across
the Upper Mississippi River Valley as another round of
scattered storms (40-70% coverage) is forecast to form from the
enhanced surface convergence.

Sunday-Monday...The trough over the western CONUS finally ejects
eastward into the Northern Plain on Sunday, introducing the upper-
level flow needed to kick the low pressure sitting over the
region eastward towards the Great Lakes. With the return to
northerly surface flow/dry air advection on the backside of this
low, PoPs should decrease on Sunday with Monday likely (80-95%
chance) being the first area-wide dry day in over a week as
seasonable conditions resume!

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 104 AM CDT Tue Sep 15 2026

Moderate showers with isolated thunderstorms are expected at
CID, DBQ, and MLI through 14 UTC with short breaks in between.
A brief thunderstorms cannot be ruled out at BRL. With the
heavier showers, visibilities could drop to MVFR conditions and
briefly to IFR. The southwesterly LLWS at 34-45 knots currently
over all TAF sites is forecasted to weaken/dissipate through
sunrise from south to north. Ceilings are expected to remain
above 5 kft also through 14 UTC before a MVFR cloud deck moves
into CID, DBQ, and possibly MLI (30% chance) with an
approaching cold front. The winds are forecasted to shift from
southerly to northwesterly over the next 24 hours and weaken
behind the front where scattered showers could redevelop late
morning into the evening.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

SHORT TERM...Delaune
LONG TERM...Delaune
AVIATION...Delaune