784
FXUS63 KDVN 081132
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
632 AM CDT Tue Sep 8 2026

.KEY MESSAGES...

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

- Quiet weather Thursday into Friday, as high pressure passes
  overhead. Seasonal conditions will remain, with mostly clear
  skies.

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

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 303 AM CDT Tue Sep 8 2026

Water vapor imagery shows a shortwave trough moving into southern
Saskatchewan early this morning. As it is doing so, low level flow
across the central Plains has become southwesterly. Warm advection
along this axis and a strong LLJ is bringing in a warm, moist
airmass that is supporting several clusters of showers and storms
from Kansas to Minnesota. As this airmass moves into eastern Iowa
and northwest Illinois this morning, these showers are expected to
decay as they encounter dry air and a dying LLJ.

Any remaining cloud debris and remnant showers will help keep high
temperatures north of Highway 30 in the 80s. South of Highway 30,
highs in the low to mid 90s are expected with peak heat indices in
the 90s. However, these peak heat indices are expected to last for
only a few hours, which should limit any major impacts.

Of greater concern is the potential for widespread showers and
thunderstorms this evening through midday Wednesday. Moisture
advection throughout the day will bring in PWATs of 2.00+ inches
ahead of a slow-moving cold front. Weak forcing ahead of this
boundary will support the development of showers and storms this
afternoon across central Iowa. Modest instability of 1000-2000 J/kg
of MUCAPE from central to eastern Iowa, combined with bulk shear of
30-40 kts, will support the development of isolated to scattered
severe thunderstorms with damaging winds embedded within the showers
and storms. These storms appear most likely from 7 PM this evening
through 5 AM Wednesday morning due to the nocturnal LLJ enhancing
the shear profiles. Due to this risk, SPC has issued a Slight, level
2 of 5, risk for severe thunderstorms west of a Marengo to Cedar
Rapids to Masonville line, and a Marginal, level 1 of 5, risk west
of a Fairfield to Bellevue line.

An additional concern with these showers and storms is the potential
for heavy rain and hydro concerns. As previously mentioned, moisture-
laden air with PWATs of 2.00+ inches will be in place, which will
provide ample moisture for heavy rain. In addition, vertical wind
shear profiles will be oriented parallel to the boundary, which will
be supportive of training storms that last over one location for
several hours. This long duration and the potential for localized
higher rainfall amounts in thunderstorms leads to increased risk of
flash flooding despite the recent dryness. This risk will be highest
west of Highway 218 in eastern Iowa, 1-2 inches of rain are expected
with localized chances (30-60%) for 3+ inches. Elsewhere, rainfall
totals of 0.3-1 inch are anticipated. Due to this, WPC has issued a
SLight, level 2 of 5, risk for excessive rainfall for eastern Iowa
west of Highway 218.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 214 PM CDT Mon Sep 7 2026

Cold front isn`t expected to be out of our area until early
afternoon on Wednesday, which will keep precipitation chances over
much of the area through the first half of the day. We will see
shower/storm coverage decrease from northwest to southeast through
the morning, with best chances for precipitation in the afternoon
hours for areas in western Illinois and northeastern Missouri. At
this time, we are not expecting much in the way of strong-severe
storms. Much of the remaining instability will have been worked
through, leaving us with a shield of stratiform rain and little/no
embedded thunder. Otherwise, we will see mostly cloudy conditions
through the day, with temperatures in the low 80s and light west to
northwest winds.

Thursday into Friday, upper level flow becomes more northwesterly as
a weak wave passes through and weak ridging builds over the Central
CONUS. This wave will be through our area by midday Thursday, with
surface high pressure moving in behind. A brief period of quiet and
seasonal weather will result, with mostly clear skies and
temperatures around 80 on Thursday into Friday. Overnight
temperatures will cool off a bit compared to recent nights, with
most in the mid 50s. Friday, the weak ridge will pass east of the
area, with southwesterly flow increasing ahead of a quickly-
approaching shortwave trof. This wave is due to come through Friday
night into Saturday, prompting our next chance of precipitation (30-
60% chances). Showers and storms will be possible along the
associated cold front, but accumulations should be on the lower-end
due to the quick movement of this wave. There remains some
uncertainty, owing to moisture availability.

Saturday and beyond appear to be a continuation of potentially
active weather, with us falling largely under upper level zonal to
southwesterly flow. This patten would favor us falling under the
path of passing shortwaves through the weekend and into next week.
Thus, daily PoPs (20-40%+) are in the forecast through this stretch,
with temperatures remaining above seasonal norms.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 632 AM CDT Tue Sep 8 2026

VFR conditions are expected through at least the afternoon hours
today before a cold front approaches from the northwest,
bringing increasing chances (70-100%) of showers and storms
this evening into Wednesday morning. Confidence on the exact
coverage and timing of storms remains low for now, so we used
PROB30 groups to help depict the potential for an earlier start
compared to what we have prevailing. Once storms begin,
confidence is high for them to produce heavy rainfall, which
should lead to MVFR/IFR visibility reductions. Some storms could
become strong, too, so locally strong wind gusts up to 40 knots
are possible. This activity is expected to continue after 12z
Wednesday.

&&

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

&&

$$

SHORT TERM...Ellingworth
LONG TERM...Gunkel
AVIATION...Schultz