862
FXUS63 KDVN 300700
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
200 AM CDT Wed Sep 30 2026

.KEY MESSAGES...

- A prolonged period of wet weather will be seen through late
  week, as rounds of rainfall pass through the area, some heavy
  at times.

- A Flood Watch has been issued for areas expecting to see the
  heaviest rainfall, which will lead to rises on area rivers and
  potential areal flooding.

- A drier and cooler weather pattern will set up this weekend
  and into early next week.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 152 AM CDT Wed Sep 30 2026

We are in for an active stretch of weather through Thursday night,
as a system digging into the southern Rockies tracks towards the
Upper Midwest. Ahead of this, we will see a baroclinic zone set up
over the region, with persistent bouts of vorticity moving overhead.
This pattern is also favorable for anomalous amounts of moisture
pumping into the region, owing to the tropical connection of the
upper level jet stretching from the Eastern Pacific and the LLJ
bringing moisture into the area from the Gulf. Thus, we will have
plenty of moisture and forcing moving overhead through the next 48
hours. For our area, this means that we are in for a prolonged
stretch of wet weather. Our forecast area falls under the area where
we will generally see continuous forcing, resulting in persistent
rainfall, where heavy rainfall can be expected. While there will be
some dry time between showers, we are expecting to remain damp and
showery throughout much of this timeframe. There will be a few
rounds where the heaviest precipitation is expected to fall. The
timing of these rounds will generally be through the day today,
tonight into Thursday AM, and then again Thursday night into Friday
AM. These more intense rounds of precipitation can be attributed to
increases in the LLJ as stronger vort maxes approach. Again, we will
continue to see rainfall chances between these, but these will be
the best timeframes for heaviest rainfall. PWATs will be
unseasonably high, roughly sitting around 2.00"+, favoring
heavy/efficient rainfall. There will be the chance for embedded
thunderstorms as well, which could locally enhance rainfall
rates, but should remain largely isolated owing to weak
instability and shear.

Looking into total rainfall accumulation when this ends Friday AM,
guidance is honing in on a sizable swath of 2-3" of rainfall for
much of our forecast area. Given the environmental setup, there will
be some locations exceeding 3", but confidence on the location and
coverage of these higher-end amounts is low. Guidance continues to
fluctuate north and south with the axis of heaviest rainfall, with
the latest 00z runs having a northward shift in heaviest amounts in
the REFS/NAM guidance. Thus, there remains some uncertainty on where
the heaviest axis will setup. Although, much of guidance generally
keeps this axis between the Interstate 80 and Highway 20 corridors.

Areas that see the heaviest rainfall will have a low-end flash flood
threat, with WPC highlighting our area in a Slight Risk, level 2 of
4, for Excessive Rainfall. One thing that might limit the flash
flood threat will be the duration of rainfall. We are not expecting
this rainfall to fall over a three hour period. Rather, we expect
these totals over a 24-48 hour period. Thus, the long duration
should allow for more infiltration than a short duration heavy
rainfall event. Rises along area rivers can be expected, especially
areas that saw rises with the recent heavy rainfall, with some areal
flooding also possible. Thus, we have opted to issue a Flood Watch
roughly along the Highway 30 and Interstate 80 corridors, as well as
areas farther southwest towards Fairfield, Iowa.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Issued at 201 PM CDT Tue Sep 29 2026

Friday through Tuesday
Assessment...medium to high confidence (50-70%) of dry and cool
conditions

By late Thursday night and into Friday morning, rain will end from
northwest to southeast. Friday afternoon looks to be cool with
temperatures only in the 60s.

Starting this weekend and continuing into the first half of next
week cool fall-like temperatures are expected.  The global models
have been advertising this scenario for over a week but have slowly
shifted the brunt of the coolest air to the eastern Great Lakes and
New England.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1239 AM CDT Wed Sep 30 2026

A busy aviation forecast is ahead of us, as widespread rainfall
overtakes the area. This rainfall will continue for most of the
TAF period, with some brief dry periods between showers.
Although, we will be dealing with rainfall and its impacts to
cigs/vis through today and tonight. Most locations will start
the TAF period VFR, deteriorating to MVFR/IFR for most locations
by 10-12z. BRL has the best chance at remaining VFR for much of
today. Overcast skies will remain, with IFR cigs moving into
CID/DBQ and remaining through much of Wednesday. The MLI
terminal will be on the edge of IFR/MVFR cigs. Opted to stay
MVFR at this time, with cigs dropping to around 1000 ft. There
remains some uncertainty on timing and intensity, hence the
introduction of PROB30 groups. Otherwise, we will see reductions
in vis throughout the area due to rainfall, generally ranging
between 3-5 SM, but brief periods of vis <3SM are possible.
Otherwise, winds will remain around 10 KTs out of the
south/south-southwest through Wednesday.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flood Watch through late Thursday night for IAZ051>054-063>068-
     076>078-087>089-098.
IL...Flood Watch through late Thursday night for ILZ007-009-015-016-
     024.
MO...None.

&&

$$

SHORT TERM...Gunkel
LONG TERM...08
AVIATION...Gunkel