177
FXUS63 KDVN 190637
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
137 AM CDT Wed Aug 19 2026

.KEY MESSAGES...

- Potential for patchy dense fog into the Wednesday morning
  commute, largely in our northern counties along a stalled-out
  boundary.

- Shower and storm chances have increased for areas along and
  south of Interstate 80 this afternoon and evening, where some
  storms may be strong to severe.

- A period of mostly-dry and seasonal weather will be seen late
  this week and through the weekend.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 128 AM CDT Wed Aug 19 2026

For the remainder of the overnight hours and into the Wednesday
morning commute, there will be the chance for patchy dense fog. With
a boundary north of the area slowly working south, this will act as
a weak axis of convergence, allowing for fog to develop. We remain
mostly cloudy overhead, which may limit some areas from developing
fog, but areas along the boundary hold the best chance. Areas at
best risk seem to be in northwest Illinois and some locations along
Highway 20 in Iowa. Uncertainty remains on how far south this will
spread, along with overall coverage.

Broad upper trof over the Great Lakes Region will continue to slowly
push east through today and tonight, with weak bouts of energy
continuing to pass overhead through the day today. The associated
cold front will continue to make very slow southerly progress
through this morning, essentially stalling out somewhere near the
Interstate 80 to Highway 34 corridors by midday. Better moisture
will be along/south of this boundary. Thus, with weak bouts of
energy streaming overhead and the stalled out boundary in place,
there will be the chance for showers/storms along and south of
Interstate 80 this afternoon/evening. North of the Interstate,
chances for storms are low, as a weak surface high pressure passes
just north of the area, shunting things to the south. Highest PoPs
will be along/south of the Highway 34 corridor, with 30-60% chances.
Between Interstate 80 and Highway 34, we will generally see 20-40%
chances. The overall trend in convective coverage has been upwards
since mid-afternoon model runs, increasing our confidence in storm
chances. A look at model soundings would also indicate that the
environment south of the aforementioned boundary would be
favorable for some organized convection, with deep layer shear
around 35-45 KTs and instability around 2000-3000 J/kg. With
this environment in place, there will be the chance for a few
strong to severe storms as well. As such, the SPC has
highlighted areas along and south of Highway 34 in a Marginal
Risk, level 1/5, for severe weather. Primary threat will be
severe wind gusts, with hail secondary. The main limiting factor
in severe chances will be meager lapse rates. PWATs are also
forecast to be between 1.50-1.75", which would be favorable for
heavy rainfall in thunderstorms. Some short term models also
indicated that there can be some localized training storms. This
would lead to a localized flash flood threat as well, largely
for areas along/south of Highway 34.

Going into the overnight hours, the better forcing will have moved
out of the area. Thus, shower/storm activity should gradually
decrease by mid-late evening. From there, we will be left with
decreasing cloud cover, light winds, and temperatures cooling into
the upper 50s in the north to mid 60s south.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 147 PM CDT Tue Aug 18 2026

Thursday through Tuesday...
Assessment...low (20-30%) confidence on late week rain chances

The models have another front moving through the area in the late
Thursday night through Friday evening time frame. Northwest flow
aloft dominates well into next week so the overall moisture
available for rain will be limited. The current model consensus is
at a 20-35% chance of rain with the better chances generally along
and north of I-80.

Outside of this time period, the prospects for rain is very limited
with temperatures near normal.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1218 AM CDT Wed Aug 19 2026

VFR conditions will start the TAF period out, with light and
variable winds. A boundary stalled out north of the area has
allowed for areas of fog to develop. Although, plenty of clouds
continue to stream overhead. Thus, there remains uncertainty on
if we will see impacts from fog tonight. Best chances will be
closest to the boundary, largely impacting DBQ. Thus, opted to
add a TEMPO group for fog at DBQ, introducing 5 SM and mist
elsewhere at this time. There will also be the chance for a
broken stratus deck between 2000-3000 ft between 10-15z this
morning, with a brief period of lower cigs possible at DBQ.
After 15z, we will see cigs lift and remain VFR until at least
18z. After 18z, we will see the chance for showers/storms,
largely impacting areas along/south of Interstate 80. Opted to
include a PROB30 group for BRL at this time, as that is where
highest confidence in impacts are.

&&

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

&&

$$

SHORT TERM...Gunkel
LONG TERM...08
AVIATION...Gunkel