493
FXUS63 KDVN 211035
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
535 AM CDT Mon Sep 21 2026

...Updated for 12z Aviation...

.KEY MESSAGES...

- An upper low over the northern plains will roll toward the
  area through Tuesday morning, leading to occasional showers
  and continued cool and cloudy conditions early to mid week.
  Then a precip break for Wednesday thru Friday.

- Expectations for a few nice dry early Fall days are growing
  for mid to late week, with highs in the 60s/near 70 and lows
  in the 40s/50s.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 230 AM CDT Mon Sep 21 2026

Upper low center seen spiraling on the latest water vapor(WV)
imagery acrs SD looks like it will be on it`s way rolling down acrs
IA and the local area by Tue morning as it become part of a Rex
Block in a rather complex upper air pattern acrs much of the CONUS.
The cool core nature of this upper level system will generate cloudy
and cool weather in it`s vicinity including the DVN CWA through at
least Tuesday. After some patchy drizzle out of low cloud decks this
morning, sctrd shower activity should increase acrs the local area by
this afternoon and especially tonight as the upper wave rolls in
closer. With elevated MUCAPEs of 300-500 J/kg tonight suppose there
may be an isolated lightning flash possible, but lapse rates in the
low to mid layers are poor and will just keep shower mention for
now. As for rainfall amounts by Tue morning, most areas that get in
on some shower activity will receive a quarter inch of less, with a
few localized spotty areas up to 0.40" of an inch. These amounts
should not be enough to effect the recent hard hit heavy rainfall
areas. It`s interesting that the 00z ECMWF does produce some spotty
amounts of 0.50 to near 0.90" of an inch acrs southeast IA.

AS for temps and winds today and tonight, an aligned pressure
gradient from north to south acrs the region to maintain a persistent
northeasterly sfc wind of 10-15 MPH with gusts up to 25 MPH through
much of the near term. High temps today not recovering much from
current values with a lot of low to mid 60s occurring. Clouds and
wind keeping lows in the 50s tonight, as well as limiting much of
any fog production in an otherwise saturated boundary layer(BL).

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 230 AM CDT Mon Sep 21 2026

Tuesday...More of the same as Monday(cloudy with temps in the 60s)
as the upper low nearby fills and weakens. This may allow for the
sctrd shower activity to wane as Tue afternoon and evening progress.
A clear out and sfc wind decrease may allow for cool overnight low
temps in the 40s by Wed morning, and may have to keep some fog in
mind especially valley and ground types.

Wednesday through Friday...Ensemble and upper jet trends suggest
that the local area to benefit from becoming under the influence of
some of the ridging of the blocked pattern aloft, which like the
previous shift mentioned, would lead to some fine fair weather fall
days with highs in the 60s to near 70 and overnight lows in the 50s
and 40s. Will have to watch for some upper trof energy to try and
undercut the ridging and shuttle some showers or way Thu or into
Friday, but the latest ensembles suggest an omega ridge to get
pumped up along the MS RVR Valley from subsidence off developing
east coast deep cyclone and erode precip as it tries to near the
area from the west Thursday and especially on Friday.

Saturday and Sunday...Getting into a more uncertain period, but the
same ensembles suggest another ridge-undercutting trof may finally
bring in some shower chances to the area Sat into early Sunday.
Currently temps look seasonable for the weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 530 AM CDT Mon Sep 21 2026

Predominantly MVFR conditions (mostly for CIGs) anticipated
during the period. Some patchy IFR CIGs and IFR to MVFR
visibility will be found this morning with low stratus, patchy
fog and drizzle. Conditions should lift to mainly MVFR as
the day progresses, and areas along and north of the Hwy 30
corridor could improve to VFR CIGs by late afternoon and
evening. There will be spotty light showers and sprinkles at
times, which may induce passing bouts of MVFR visibility for
much of the TAF period. Winds look to remain generally from the
NE at 10-15+ kt.

&&

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

&&

$$

SHORT TERM...12
LONG TERM...12
AVIATION...McClure