173
FXUS63 KDVN 171913
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
213 PM CDT Mon Aug 17 2026

.KEY MESSAGES...

- There is a conditional Marginal (level 1 of 5) risk for severe
  storms Tuesday. Primary threats will be damaging wind and
  locally heavy rain.

- Another stretch of quieter weather returns late in the week
  and into the weekend, with limited light precipitation
  chances.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 205 PM CDT Mon Aug 17 2026

A much welcomed dry day, with more comfortable humidity levels
was seen today compared to what we have seen in previous days!
Early afternoon temps were in the upper 70s/low 80s, with
dewpoints in the low to mid 60s (9 to 14 degrees cooler than
24hrs ago). GOES visible satellite imagery depicts a nice Cu field
around 3-4kft across the entire area.

High pressure ridge to drift across the region late evening/early
Tuesday providing clearing skies and quiet conditions. Some
model guidance is beginning to show some fog potential,
particularly east of the MS RVR closer to the ridge axis and
where the boundary layer and soil moisture remain quite moist.
Decided not to add any fog mention to the forecast just yet, but
will pass on to the evening shift.

Tuesday...two weak shortwaves to track across the area providing
enough lift and top down saturation to bring rain showers back
into the forecast. The first wave to move across prior to
sunrise and with the latest 17z RAP showing a 35kt LLJ
developing, scattered showers with some embedded thunder will
be possible during the morning hours. No severe storms are
anticipated with this round. The question then becomes do we
clear out and recover or does precip and clouds remain overhead
for a good portion of the day thereby limiting heating. Latest
CAMs remain mixed in their respective solutions regarding
afternoon/evening storms along and ahead of the next shortwave
and cool front. This leads to a lower confidence and conditional
severe risk hinging on whether we see clearing take place. Our
current forecast would favor clouds lingering longer in the
morning, keeping our afternoon/evening severe risk limited. That
said, if any differential heating/breaks in clouds can occur
the kinematics are there for a few isolated severe low topped
storms, albeit would like to see steeper mid-level lapse rates.
Damaging wind and locally heavy rain would be the primary
threats. The SPC Day 2 afternoon update has removed the Slight
(level 2 of 5) out of the CWA, with the entire area now in a
Marginal risk for severe (level 1 of 5). 0-3km shear is progged
around 35kts and 0-3km CAPE around 150-200 J/Kg across the
southern two tiers of counties, which would be the area to watch
late afternoon/evening if storms were to form. With PWs around
2" once again, heavy rain will also be a concern and with such
wet antecedent conditions south of I-80, WPC has a Day 2 Slight
for excessive rain.


&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 205 PM CDT Mon Aug 17 2026

The storm system that moves across the area Tuesday into
Tuesday night will usher in a pattern change to northwesterly
flow across the Upper Midwest with ridging and a heat dome to
our west and a trough over the eastern US. This places Iowa near
the main storm track and in the transition zone to warmer
temperatures to our southwest. This flow will lead to shortwave
energy moving across the area every 36 to 48 hours with
scattered showers and storms possible with each passing
shortwave. Rain amounts are expected to be light with NBM
probabilities of 0.5 inches or more below 10% through the
period.

Tuesday night, a cool front is forecast to move southeastward across
the area through 12 UTC Wednesday. The better lift is forecast to
overspread the area after 00 UTC Wednesday. There is some
disagreement between the different models on the amount of
instability available after 00 UTC but 0 to 6km shear of 30 to 40
knots will be in place with the NBM mean CAPE of 1000 to 1500
J/KG of CAPE. There is also a similar signal in the HREF.
Rainfall amounts will be light with most locations receiving
less than a quarter of an inch. NBM probabilities of greater
than a quarter of an inch are 10 to 15%. High pressure is
forecast to quickly build into the area at the surface and
aloft. This will bring quiet weather to the area

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1153 AM CDT Mon Aug 17 2026

VFR conditions expected through much if not all the TAF cycle.
Fair weather cumulus around 3kft will begin to dissipate around
sunset, with winds also becoming light. With mostly clear skies
and calm wind late tonight, some guidance is hinting at some
MVFR fog potential particularly at BRL/DBQ prior to sunrise.
Left out mention for now as probabilities remain under 20%. A
storm system to track across the upper Midwest overnight,
bringing a chance of scattered showers late in the period at
CID/DBQ and have included PROB30 groups for this possibility.

&&

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

&&

$$

SHORT TERM...Gross
LONG TERM...Cousins
AVIATION...Gross