835
FXUS63 KDVN 291113
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
613 AM CDT Tue Sep 29 2026

.KEY MESSAGES...

- Active stretch of weather through midweek, as an approaching
  system brings rounds of rainfall. Heavy rainfall is expected,
  with the potential for areal flooding and rises along area
  rivers.

- Drier weather returns late this week and through the weekend,
  with cool and pleasant weather.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 131 AM CDT Tue Sep 29 2026

Upper ridge starts to track easterly as the trof over the eastern
CONUS breaks down and moves offshore through tonight. Upper level
southwesterly flow will then set up over the region, with a long
fetch reaching towards the Eastern Pacific. As such, surface high
pressure will move east of the area today. With high pressure
tracking east, llvl winds will increase out of the southwest as
well, setting the stage for warm advection into the region. Thus,
temperatures will remain in the 70s throughout the area today, with
moisture also on the rise. Some in our south might approach 80 this
afternoon, which is above seasonal norms. We expect to remain dry
through today and the first half of tonight, as plenty of dry air
remains. Although, the increase in moisture that we do see will be
in the way of increasing cloud cover through today, especially
overnight tonight. We can expect a mix of mid/high clouds and sun
through the day today, with overcast skies taking over tonight. The
LLJ will increase quite a bit after sunset this evening, with the
jet core oriented off to our west early. After midnight, the LLJ
will start to center over our area, resulting in widespread
increases in PoPs, with most seeing 50-80% chances for showers and
embedded storms by sunrise Wednesday.

Severe weather is not expected at this time. Since rainfall will
largely be starting after midnight, the threat for flash flooding is
low, with WPC indicating largely <0.50" of rain overnight. Short
term guidance and ensemble suites generally favor ~0.50" with 30-50%
probabilities for most and about 50-70% for areas along/north of a
line from Cedar Rapids to Dubuque, IA. Pockets of higher amounts up
to an inch will be possible, but will remain localized.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 131 AM CDT Tue Sep 29 2026

Wednesday/Thursday...

This will be quite the dreary stretch of weather, as we will
continue to see bouts of vorticity flowing into the region ahead of
the potent wave over the southern Rockies. There will also be a
baroclinic zone that sets up, which will act as a focus for heavier
rainfall. Although, there is much uncertainty on where this will set
up at this time. Over the last few forecast runs, this axis has
trended south, closer to the Interstate 80 corridor. Although,
some guidance still has this north. In either case, we will be
saturated with continuous bouts of vorticity passing overhead,
favoring widespread rainfall through much of this timeframe.
Overall, this will generally be in the form of persistent light-
moderate rain showers passing through, with heavier rainfall
expected at times. While there will be some dry time between
showers, we are expecting to remain damp and showery throughout
much of this timeframe. PWATs will be unseasonably high, roughly
sitting around 2.00". Thus, if we manage to get more convective
activity, then we will have the chance to see heavier rainfall.
Although, there remains some uncertainty on this.

WPC continues to favor much of the area seeing 1.50-3.00" of
rain when all is said and done, with localized areas potentially
seeing 3.00"+. Confidence on these higher totals is low at this
time, with ensemble guidance still in disagreement on amounts
and location of the heaviest rainfall axis. The Euro suite
remains the most aggressive with rainfall, highlighting chances
for 2.00"+ of rain by Friday AM around 70-90% roughly along the
I-80 corridor. Although, the GFS and other ensemble suites are
farther north with this axis and only favoring 2.00"+ with about
40-70% probabilities. 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.
Some rises on area rivers may be possible though, especially
areas that saw rises with the recent heavy rainfall, along with
the potential for some areal flooding.

Friday and Beyond...

Late this week and into the weekend, zonal to northwest flow will
set up over the region. Some guidance hints at a wave passing
through Saturday into Sunday, but moisture will be limited. The
drying trend continues from last forecast package, with NBM
indicating dry conditions through the weekend. Thus, this wave may
just come through with some passing clouds and a wind shift.
Otherwise, a cooler and pleasant weekend is currently forecast for
the area.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 610 AM CDT Tue Sep 29 2026

Today will be quiet and VFR, with southeast winds under 10 kts
this morning, and around 10 kts this afternoon, turning due
south by this evening. After midnight tonight, periods of rain,
possibly with some thunder, will move through the area.
Initially, this may be VFR for a few hours before a long period
of MVFR/IFR conditions in rain spread over the region towards
daybreak Wednesday. This period of rain and some thunderstorms,
will continue throughout the day into Thursday night. Rain will
be possible at any time, but should not be continuous the entire
period.

&&

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

&&

$$

SHORT TERM...Gunkel
LONG TERM...Gunkel
AVIATION...Ervin