791
FXUS63 KDVN 082340
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
640 PM CDT Tue Sep 8 2026

.KEY MESSAGES...

- A storm system passing through the Upper Midwest will bring widespread
  showers and storms to the area tonight into Wednesday
  morning. Severe storms and heavy rainfall with the potential
  for some localized flash flooding will be possible in eastern
  Iowa.

- Quiet cooler weather Thursday into Friday, as high pressure passes
  overhead.

- Another stretch of potentially active weather this weekend
  into the next work week, bringing daily chances of
  precipitation for some.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 245 PM CDT Tue Sep 8 2026

This afternoon`s water vapor imagery showing tonight`s and Wed
weather maker wave acrs southwest MT, and also showing large long
fetch baroclinic leaf from southwest of the CA Baja to western
Quebec. This as well as LLJ feed off the western Gulf will make for
a moist atmospheric column tonight with 2+ inch PWATs still on track
acrs the region into Wed morning. The current activity from NE into
northern IA will look to get revved up by a increasing SW LLJ of 35-
45 KTs and increasing effective shear profiles of at least 35 KTs as
the evening and night progress. This and MLCAPEs of 1000-1500 J/kg
may make for some strong to marginally severe storms as they flame
up in the area or move in from the west as maturing bows, with the
already advertised damaging winds being the primary threat. But
marginal mid level lapse rates of only 6 C/km and signs in the fcst
soundings of developing llvl inversions overnight may limit the wind
cause especially late.

Storm outflows may gush out well ahead of the main sfc front tonight
into Wed morning, setting the focus of repeated storm development
and then training along these outflow boundaries or even the
incoming main front itself, if the fcst shear profiles and
orientation are correct. This potential utilizing the high PWAT feed
supports the advertised threat for some swaths of high rainfall(1-3+
inches) and localized flash flooding especially in urban environments
such as Cedar Rapids. Some uncertainty remains on the eventual
primary axis north-south lay out of the main convective zone in the
latest CAMs and coarser models, but ensembles are pointing to more
of the Along and north of I-80 to Hwy 30 corridor for longer
duration storms and rains making it the more likely axis for heavy
rainfall. Low temps tonight in the upper 60s to low 70s, with some
patchy fog at least temporarily possible in rain lulls along with
light and variable sfc wind trends along boundaries.

Wednesday and Wednesday night...The post frontal rains will continue
through at least midday, with a slow southward frontal migration as
the day progresses. Thus could see high temps held down in the upper
70s to low 80s acrs much of the area. Flattening steering flow aloft
and additional short wave shuffle may keep additional over-running
showers going in the southern CWA Thu night. With a light post-
frontal sfc wind regime looking to be on tap, if there will be any
cloud thinning or clearing in the north late Wed night into Thu
morning, may have to keep some fog in mind especially acrs heavy
rainfall areas if they occur in the northern CWA.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 245 PM CDT Tue Sep 8 2026

Thursday and Friday...A couple of decent looking days look in store
with bouts of both sfc and upper ridging allowing for dry and near
seasonable conditions.

Saturday through Monday...The latest  suite of medium range models
continue to suggest flattening flow again embedded with passing
short wave and associated sfc fronts making for a potentially active
period.  First in line may be Saturday with a sfc front getting
swept through the area off a passing LLVL cyclone along the
US/Canadian border. Then maybe a short lull for Sunday before signs
of a digging longer wave trof acrs the western high plains arching
steering flow in a southwesterly fashion toward the upper midwest.
This could make for another unsettles period for Sunday night into
early next week if this pattern verifies.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 620 PM CDT Tue Sep 8 2026

A stormy night is ahead of us, bringing impactful weather to all
terminals. A complex of strong to severe storms is currently
located over central Iowa, tracking east over the next few
hours. This complex will near CID between 01-03z, reaching MLI
between 03-05z. After this initial surge of storms, we expect
widespread showers and storms to develop throughout the area for
the remainder of the night. DBQ will be the more questionable
area on how long and persistent the storm coverage is, but
should be the quickest for storms to move out of Wednesday AM.
This initial complex of storms will bring the potential for
strong to severe wind gusts and hail, but there remains some
uncertainty on the severe threat after 03z. With all
showers/storms, we can expect vis reductions to 3-5 SM with
lower possible in the strongest storms. Otherwise, cigs largely
look to remain MVFR-VFR throughout the night. After 12z
Wednesday, we will see the coverage of showers/storms decrease
from north to south through the area. At this time, the overall
chances for storms will be decreasing, largely becoming
stratiform rain or showers.

Winds will start the TAF period light and largely out of the
south. Over the next few hours, these storms and their
associated outflow boundaries will result in variable winds
that will remain through much of tonight. After 12z Wednesday,
winds will be light and out of the southwest, becoming
northwesterly after the cold front passes through the area later
in the day.

&&

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

&&

$$

SHORT TERM...12
LONG TERM...12
AVIATION...Gunkel