771
FXUS63 KDVN 111723
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1223 PM CDT Mon Aug 11 2025

.KEY MESSAGES...

- Several rounds of scattered thunderstorms are forecast through
  Tuesday with localized heavy rainfall on saturated ground the
  primary concern. The strongest storms could produce torrential
  rainfall rates between 1-2" per hour and locally damaging
  winds.

- A break from the rainy pattern is expected for the middle of
  the week as a slightly less humid air mass works into the
  region.

- The heat and humidity returns by Friday, with thunderstorm
  chances back in the forecast for the weekend (20-40%).

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 300 AM CDT Mon Aug 11 2025

As of 3 AM, SPC mesoanalysis had a weak surface trough across
the Mid to Upper Mississippi Valley region and a tight west to
east PWAT gradient across Iowa into Illinois (0.9" in western
Iowa to ~1.9" north of Chicago). The radar was clear across
eastern Iowa and northwest Illinois, mainly because the axis of
enhanced 925-850mb WV transport has shifted slightly east of the
area. Light surface winds (5 mph or less), humid conditions
with dewpoints in the upper 60s to lower 70s, and pockets of
clear skies has led to shallow fog development across the area.
Some of the fog could become locally dense and last into the mid
morning hours, likely to quickly dissipate after 8 or 9 AM.
Difficult to predict where the fog will become most prevalent,
but areas north and west-southwest of the Quad Cities appear to
be the favored locations. The HRRR has been consistently
developing pockets of dense fog across portions of eastern Iowa
where winds are calm and dewpoints depressions are already
zero. Have messaged fog potential with a Special Weather
Statement and will continue to closely monitor surface
observations and coverage of the dense fog.

Another warm and humid day is expected with increasing chances
for scattered showers and thunderstorms, especially late in the
day and into tonight. The low-level jet and axis of higher 850mb
WV transport is forecast to surge back into the region, causing
PWATs to jump to 1.7" - 2". Mid-level impulses associated with
ongoing and/or decaying convection across the Central Plains
into NW Missouri are forecast to occasionally roll across
eastern Iowa and northwest Illinois, coincident with large scale
ascent in the right entrance region of an upper jet. Therefore,
we can anticipate an increase in shower/storm coverage, though
likely still remaining scattered, later this afternoon/evening
and lingering through most of tonight (30-60%); highest chances
in the counties along and east of the Mississippi River.
Locally heavy rainfall on saturated ground is a concern and
could result in localized flash flooding. WPC has a Marginal
Risk (level 1 of 4) for excessive rainfall across the area, so
it`s a lower risk than the past few days mainly due to less of a
threat for training convection over the same areas. Given
moderate instability (1000-2000 J/kg MLCAPE), the strongest
storms could produce isolated damaging wind gusts.

The active pattern continues for Tuesday with additional rounds
of scattered showers and storms possible (20-50%) as a weak
cold front approaches from the northwest.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 300 AM CDT Mon Aug 11 2025

Wednesday is shaping up to be dry as high pressure builds into
the region. Northwesterly winds will usher in less humid air
with dewpoints in the 60s. The humid conditions will make a
quick return late in the week with dewpoints back into the 70s
by Friday. For the upcoming weekend, expect hot and very humid
conditions, along with periodic chances for scattered showers
and thunderstorms (20-40%). NBM highs are in the mid 80s to
lower 90s Friday - Sunday.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1213 PM CDT Mon Aug 11 2025

VFR conditions will start out our TAF period, with MVFR to IFR
conditions possible this evening/night. Some PROB30 groups were
introduced for the low-end chance of showers/storms this
afternoon at BRL/MLI. Otherwise, better chances for
showers/storms move in later throughout the area. This evening
and through the night, we expect scattered showers/storms to
develop and persist. Frequent lightning and heavy rain will be
the main threats with these storms, but some gusty winds cannot
be ruled out. These showers/storms will bring cigs down to
1500-2500 ft, with vis between 3-5 SM. These conditions
aren`t expected to last the whole time. Rather, this can be
expected when storms track through the area. Otherwise, an
overcast deck >5000ft will remain, with light and variable
winds.

&&

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

&&

$$

SHORT TERM...Uttech
LONG TERM...Uttech
AVIATION...Gunkel