107
FXUS63 KDVN 302334
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
634 PM CDT Wed Sep 30 2026

...Updated for 00z Aviation...

.KEY MESSAGES...

- Prolonged period of wet weather continues, with two more
  rounds of rain through Thursday night. A Flood Watch remains
  in effect and has been expanded north for excessive rainfall,
  rising rivers, and potential areal flooding.

- Pleasant early Fall weather this weekend into early next
  week, with dry conditions and seasonable temperatures.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 224 PM CDT Wed Sep 30 2026

A gloomy and wet last day of September is occurring across the
CWA, with low clouds and rain keeping temperatures in the 60s
for much of the daylight hours. Rainfall amounts from the 1st
round that is now nearing the eastern edge of the forecast area,
were in the 1-2" range primarily within the initial flood watch
area, with some 2"+ totals at some mesonet sites in Keokuk,
Washington, Muscatine, and Cedar counties as of 1pm. These
totals fell in an already saturated area from last week`s rain
resulting in rises on the English, Skunk, Iowa, Cedar, and Des
Moines rivers. Additional flood watches and warnings have been
issued for locations on these tribs based largely on the
forecast QPF in the next 48 hrs. See hydrology section for
additional details.

A brief lull or at least a decrease in overall rain amounts is
expected late this afternoon/evening before the next round
arrives after midnight. Upper low currently over western NM
will slowly move east this evening, with its warm moist conveyor
belt continually pulling high PW moisture up into the central
Plains and into IA. In fact, our 18z DVN sounding recorded a
2.03" PW which is the 9th highest for the month of September!
The most recent sounding that is comparable to that value was
back on the 00z 9/22/2019 sounding. A very moist environment to
say the least for Sept 30th. Diffluent flow aloft and
convergence along a theta-e gradient will allow widespread
showers and thunderstorms to continue across northern
KS/southern NE this evening/overnight spreading eastward over
IA. Deep warm cloud depths combined with a strengthening LLJ
will allow these storms to be efficient rain producers with
moderate-heavy rain likely for several hours at any one
location. WPC has continued its moderate ERO for excessive
rainfall for areas just west of the CWA, with a slight (level 2
of 4) risk for excessive rain in our area north of a line from
Memphis, MO to Galesburg. The question becomes where does this
2nd round of storms layout over the CWA. Most 12z deterministic
and ensemble guidance suggests the axis of heaviest rain
(another 1-3") will be displaced slightly north of the 1st
round, which would be across north central IA into northeast IA.
This scenario is favored and if it comes to fruition would be
ideal for limiting any significant flash flood/areal flooding
concerns. However, if it falls closer to the Hwy 30/I-80
corridor then there would be more urban flooding issues and
perhaps even a flash flood threat just prior to the AM commute.

In addition, the 12z HREF/REFS both have a 1-3hr window between
06z-12z tonight with 3hr QPF amounts exceeding 3hr FFG just
north of Cedar Rapids. For this reason, have opted to expand the
Flood Watch north into the Hwy 20 corridor.

Thursday, rain will be ongoing during the morning hours similar
to today with the overall intensity decreasing as LLJ veers off
to the east. Highs may struggle to reach 70 degrees once again
with extensive cloud cover overhead. The last and final round of
rain arrives during the afternoon and evening, likely occurring
in our IL counties. Some of the latest guidance coming in
suggests the bulk of this round may occur just to our south,
which may allow our Flood Watch to be cancelled early.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 224 PM CDT Wed Sep 30 2026

Pleasant early October weather is forecast late Friday through early
next week, with dry conditions and seasonable temperatures.
Highs in the 60s and lows in the 40s will be seen. A large
1027mb surface high will build into the upper Midwest bringing a
drier airmass into the CWA. It will be a fantastic weekend for
any outdoor activities! On Monday, ensemble 850mb temps drop
into the 4-8C range and as a result we could see some overnight
lows dropping into the upper 30s Monday night.

The next chance of rain will come on Wednesday, as a cold front
moves through. Moisture will be limited as noted by 1000-500mb RH
progs and this could end up just bringing an increase in clouds.
This would be good news for farmers wanting their fields to dry out
to start planning their harvest.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 624 PM CDT Wed Sep 30 2026

Predominantly MVFR to IFR conditions expected in low clouds,
fog, rain/drizzle/showers during the period with pockets of
LIFR (KCID/KDBQ) and VFR (KBRL). Anticipate a bout of
heavier convective activity arriving later tonight into
Thursday morning tied with increasing synoptic scale ascent
with negative theta-e lapse rates in the 850-500 mb layer
supportive of embedded thunder. A cold front will sag
southward across the terminals late Thursday morning through
afternoon bringing a wind shift to a northerly direction.
Conditions could improve to VFR post-frontal mid to late
afternoon Thursday, particularly at KDBQ and KCID.

&&

.HYDROLOGY...
Issued at 1232 PM CDT Wed Sep 30 2026

Many of the area rivers have not fully returned to normal
streamflows after the last rainfall event in mid-September.
That leaves them primed for additional flooding where the higher
rainfall totals end up over the next couple days, especially
along the Iowa and Skunk rivers. Several river watches and
warnings have been issued where flooding is most likely to
occur. There will also likely be rises along the Mississippi
River especially south of New Boston. These river forecasts are
largely based on rain that hasn`t fallen yet, so the forecasts
will likely be adjusted once we see how much rain falls and
where the highest amounts are across the area leading to a
higher confidence in flood category. Please keep an eye on
forecast and updates to flood products in the coming days.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flood Watch through late Thursday night for IAZ040>042-051>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...Gross
LONG TERM...Gross
AVIATION...McClure
HYDROLOGY...Schreck