413
FXUS63 KDVN 281929
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
229 PM CDT Mon Sep 28 2026

.KEY MESSAGES...

- High pressure overhead will result in a beautiful start to the
  work week, with mostly clear skies and mild temperatures.

- Another active weather pattern will set up mid-late week,
  bringing the potential for rounds of showers and storms with a
  threat for heavy rainfall.

- Temperatures will remain near to slightly above seasonal
  norms through the next week.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 215 PM CDT Mon Sep 28 2026

Beautiful weather for late September will continue with high
pressure centered over the Great Lakes and Ohio Valley. Locally,
for eastern Iowa and northwest Illinois we can expect mild
temperatures and dry conditions. Mainly clear skies this
evening/tonight will give way to increasing high clouds through
the day on Tuesday. Highs will once again reach into the 70s,
with even some upper 70s south of Highway 30 as steady
southerly winds advect a warmer air mass into the region.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 215 PM CDT Mon Sep 28 2026

Trough over the eastern CONUS continues to break down through
Tuesday/Wednesday, with the ridge that has been locked in place
overhead tracking easterly. Upper level flow will then increase out
of the southwest as a deep trof digs into the Desert Southwest. A
strong fetch of moisture in connection with the Eastern Pacific will
set up, directing an unseasonably moist airmass into the central
CONUS. This increase in moisture is aided by tropical systems that
will get caught in the flow from the Eastern Pacific, serving as a
moisture conveyor into the region, with plenty of forcing to favor
precipitation chances. Not only will this help supply moisture to
the region, but llvl southerly/southwesterly flow will usher Gulf
moisture in as well. Thus, an anomalously moist airmass will be in
place through mid week, with PWATS between 1.50-2.00" or higher
moving in. As such, the WPC has highlighted our area in a Slight
Risk, level 2 of 4, for Excessive Rainfall and Flash Flooding
for Wednesday and Thursday. The wave digging into the Desert
Southwest will slowly traverse over the Rockies, guiding bouts
of energy towards the Upper Mississippi River Valley, with a
baroclinic zone setting up nearby. This baroclinic zone will
serve as a focus for the potential for rounds of showers/storms,
with heavy rainfall possible.

Latest model trends have the heaviest axis of QPF across
portions of central into eastern Iowa, where some areas could
receive over 3" of rainfall from late Tuesday night through
Thursday night. However, the exact north/south placement is
uncertain. The EC ensemble mean continues to be the southern
most solution (and wettest) with the highest rainfall amounts
along the I-80 to Highway 30 corridors. Other ensemble models
(GEFS/AIGEFS/EC AIFS/CMC) are shifted more to the northwest,
but still clip our northwest counties with some of the higher
rainfall amounts of 2"+. Given this uncertainty, and since the
heavy rain will come in several separate waves Wednesday -
Thursday, will hold off on a Flood Watch for now.

The timing has also trended later over recent forecast runs. We
were initially looking at the potential first round of
showers/storms moving in Tuesday night, but we are now looking
at potential onset closer to the early Wednesday AM timeframe.
The more widespread rainfall chances will hold off until
Wednesday PM and into Thursday (60-90% chances). Through this
~2 day stretch, WPC has a widespread 1.75" to 2.5"+ across the
outlook area, with the highest amounts favored west of the
Mississippi River. Certainly, localized higher totals of 3"+ are
possible. The latest NBM 48-hr QPF probabilities for 2"+ are
fairly high between 50-80% (southeast to northwest). We will
continue to monitor trends in the forecast, especially as more
hi-res guidance comes in.

Late this week and into the weekend, zonal to northwest flow will
set up over the region. We might see some weak waves work through
the flow, but much uncertainty remains on moisture availability.
Guidance has trended drier through the weekend than in previous
runs, with chances between 15-30% at this time.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1255 PM CDT Mon Sep 28 2026

High pressure in control over the Mid to Upper Mississippi
Valley region will result in quiet weather with prevailing VFR
and light winds through the period.

&&

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

&&

$$

SHORT TERM...Uttech
LONG TERM...Gunkel/ZU
AVIATION...Uttech