496
FXUS63 KDVN 292321
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
621 PM CDT Tue Sep 29 2026

...Updated for 00z Aviation...

.KEY MESSAGES...

- A prolonged period of wet weather will be seen through late
  week in the form of three rounds of heavy rain. In between
  each round, spotty showers and potentially drizzle will be
  seen.

- Given the long duration of the rain, rises on area rivers will
  occur. The probability of a flood watch being needed at some
  point over the next 72 hours is around 30 percent.

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

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 201 PM CDT Tue Sep 29 2026

After a pleasantly warm fall day, rain showers will develop tonight
and evolve into a widespread rain by sunrise Wednesday. The rain
will taper off to more spotty showers and potentially drizzle for
Wednesday afternoon.

Prime time for the first round of heavy rain looks to occur between
midnight and noon Wednesday. Any thunderstorms will be isolated so
rain rates look to be light to moderate with periods of heavy rain.
HREF probabilities of exceeding 0.25 inches/hour are at 30-40%. The
axis of this round of heavy rain looks to lie between Cedar Rapids
and the Quad Cities.

&&

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

Wednesday night through Friday
Assessment...very high (>90%) confidence of widespread heavy rain

Round 2 of heavy rain will occur Wednesday night into Thursday
morning. The probabilities of heavy rain are the highest during this
time frame as PWATS are just over 2 inches and the overall forcing
will be enhanced with the passage of a weak surface low.

The axis of the heaviest rain looks to run from Cedar Rapids up to
Dubuque; thus there will be some overlap between round 1 and 2. Like
the previous night the probability of rainfall rates exceeding 0.25
inches/hour is 30-40 percent. Thus this will be another long period
of light to moderate rainfall with periods of heavy rain.
Thunderstorms will be possible but are still expected to remain
isolated to low end scattered (20-30%).

Another period of spotty showers and drizzle looks to occur Thursday
afternoon before round 3 begins late Thursday afternoon into
Thursday night.

Unlike the previous two rounds of heavy rain, this round will be
further to the south and east. Right now the rough axis looks to be
from roughly Keokuk, IA to Peru, IL. Given the southward trend with
the heavy rain, the possibility does exist that the axis of round 3
could be further to the south and east. Thunderstorms will be
possible but will remain isolated to low end scattered (20-30%).

Like the previous two round of heavy rain, the probability of
rainfall rates exceeding 0.25 inches/hour are 30-40%.

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.

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

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 /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 615 PM CDT Tue Sep 29 2026

A round of rain/showers and possibly isolated storms is expected
tonight through early Wednesday afternoon. This will be largely
with VFR to MVFR conditions, with IFR possible. Guidance is
wanting to bring in IFR ceilings overnight and throughout the
day on Wednesday, particularly at KCID and KDBQ. Confidence is
somewhat low on this, as currently much of the guidance is
verifying too expansive/overdone with low conditions to our
west. I did maintain the IFR ceilings at KCID and KDBQ, but
given the guidance trends opted to push back these until
Wednesday morning. There is a signal for improvement back to
VFR at KBRL and KMLI later Wednesday afternoon as the initial
round of rain diminishes and low level flow veers from S/SW offering
potential for some lifting ceilings.

&&

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

&&

$$

SHORT TERM...08
LONG TERM...08
AVIATION...McClure