974
FXUS63 KDVN 152338
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
638 PM CDT Sat Aug 15 2026

.KEY MESSAGES...

- Chances for showers/storms return this evening and overnight
  as a weak cold front arrives in the area.

- High pressure will bring a period of much needed quiet and dry
  weather Sunday through Monday, prior to the pattern becoming
  more active Tuesday through midweek.

- Strong to severe storms are possible Tuesday, as a much more
  potent cold front arrives into the region.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 113 PM CDT Sat Aug 15 2026

Low level moisture remains plentiful over the region in the wake of
the overnight storms and heavy rain. These rains fell in the
southern 1/2 of the area, and were heaviest in our far southern
counties. We now have saturated conditions found south of I-80, and
rather wet soil conditions found to the north. This antecedent
condition will keep the threat for isolated flash flooding possible
for any slow moving or strong thunderstorm tonight.

We do have the treat for additional storms tonight, but with a much
smaller footprint of heavy rainfall expected, and reasonable
confidence it will be a narrow swath of heavy rain, I am inclined to
hold off on any new flood watch for now.

Looking at the environment, much like yesterday, nearly every
model is too warm regarding low level temperatures, but humidity
remains very high, and is handled reasonably well. Thus, far,
this combination is keeping heat index readings under 95 degrees
in all areas. Tonight, the front will arrive rather late at
night, if not nearly morning, however, a pre-frontal wind shift
to the west is expected to combine with lift from a mid level
short wave to bring showers and storms to the area. There is
quite a bit of variation in placement of storms tonight, but
decent agreement on timing and character of storms. A small
cluster, possibly with an advancing cold pool is forecast to
move through between 7PM and Midnight. PWATs remain very high,
around 2 inches, but movement should be rather quick, especially
if storms are strong. Thus a narrow stripe of QPF around 1 inch
is possible, with amounts elsewhere very low, or dry. SPC
generally is following that progression as well, as we remain in
a marginal, level 1 risk. The late evening arrival supports a
cold pool and faster movement as well, in a mature stage of
convection. Wind gusts of 40-50 mph can be expected with this
line, with some threat 20-30% for winds over 60 mph.

&&

.LONG TERM /SUNDAY THROUGH SATURDAY/...
Issued at 113 PM CDT Sat Aug 15 2026

Sunday Through Monday...

This timeframe will be relatively quiet, as we will be fully post
frontal and generally in cool/dry advection by midday Sunday. Upper
wave and cold front will be east of the area by early Sunday
morning, which will effectively help flatten the ridge that was set
up over the area the last week, which brought persistent rainfall.
Thus, this will shunt the active baroclinic zone south of the area,
with surface high pressure passing over through Monday. A period of
quiet and dry weather will be seen, with near seasonal temperatures.
Monday looks to be a beautiful day with mostly clear skies. Enjoy
this reprieve from the active stretch of weather that the region has
been experiencing, as the pattern becomes active once again Monday
night through midweek.

Tuesday and Beyond...

Monday night into Tuesday, weak ridging will pass east of the area,
pushing the surface high pressure out and resulting in increasing
llvl southwesterly flow. Temperatures and moisture will both
increase on Tuesday, with best moisture moving in later in the day.
LLJ will kick in Tuesday evening and through the night, as a quick-
moving upper wave approaches the area from the northwest. A
seasonally strong cold front will accompany this wave, providing
sufficient surface and upper level forcing for thunderstorms. A
brief look at model soundings during this timeframe would indicate
the potential for an overnight complex of thunderstorms passing
through the area, as we have seen over the last week. The main
difference with this system is that it will be progressive, pushing
out of the area by early-midday Wednesday and leaving us in a post-
frontal airmass through the remainder of the week. The best moisture
will move into the area ahead of the cold front Tuesday night, with
global guidance indicating 1.50-2.00" PWATs moving in. Thus, heavy
rainfall will be on the table with these storms. It is still
early, but SPC is outlining that period for a Slight, level 2,
severe threat, given the pattern and environment in place.

After this wave pushes out of the area on Wednesday, we will see
weak zonal-northwesterly flow set up again over the region. Surface
high pressure will pass through late in the week, which should bring
a period of mostly dry weather. Although, there remains some
uncertainty, as some long term models indicate subtle waves passing
through bringing low-end PoPs. NBM favors the mostly-dry forecast,
leaving PoPs <20% through Friday. The post-frontal airmass will keep
temperatures cooler through the second half of the week, with most
in the mid 70s.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 632 PM CDT Sat Aug 15 2026

A weak cold front will move through eastern Iowa and northwest
Illinois this evening and tonight, bringing a chance for
scattered showers (20-50%) and storms mainly south of CID. With
low confidence on areal coverage, have mentioned the thunder
chances at MLI and BRL in PROB30s. Occasional MVFR ceilings are
possible at MLI overnight into Sunday AM, with periods of IFR
likely at DBQ. Additionally, fog may develop at DBQ tonight with
potential for visibilities to drop near or below 1 mile at
times.

&&

.HYDROLOGY...
Issued at 1225 PM CDT Sat Aug 15 2026

Rainfall ranging from 2 to 6 inches,fell across southern parts
of the area, mainly south of the tributary forecasts it was
expected to fall 24 hours ago. This is a helpful thing, though
flooding did impact portions of McDonough through Lee County
overnight, and this warranted minor flood warnings for the Skunk
River at August today, and a moderate flood warning for Colmar,
on the La Moine River.

Flood warnings and watches on portions of the Iowa,
Wapsipinicon, and upstream Skunk have been cancelled, as this
rainfall fell south or downstream of these forecast points.

&&

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

&&

$$

SHORT TERM...Ervin
LONG TERM...Ervin
AVIATION...Uttech
HYDROLOGY...08