857
FXUS63 KDVN 190804
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
304 AM CDT Tue Aug 19 2025

.KEY MESSAGES...

- Cloudy and cooler today, with areas of fog this morning
  mainly west of the Mississippi River.

- Dry and more seasonal conditions tonight through the rest of work
  week.

- Cooler and less humid this weekend, with a slight chance of
  precipitation Saturday.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 256 AM CDT Tue Aug 19 2025

Morning water vapor imagery shows shortwave responsible for
yesterday`s storms over southern Lake Michigan, with radar
mosaics showing all precip to our east. Nighttime Microphysics
satellite loop depicts a large area of low stratus dropping
south out of WI and northeast IA, with surface observations
showing dense fog developing over northern IA and southern MN
just to the west of the low stratus.

A very moist boundary layer combined with near calm winds will set
the stage for areas of fog this morning, primarily west of the
Mississippi. The main questions will be how dense and how long
will this fog linger. The 00z HREF probabilities of visibility
less than a half mile are highest (30-40%) west of a line from
Dubuque to Mt Pleasant before 9am and quickly improve
thereafter. The 06z HRRR would show areas northwest of a Dubuque
to Cedar Rapids the most favored. In any case, will hold off on
any dense fog headlines for now and will continue to monitor
trends.

Rest of Today...Northerly low level flow and weak CAA will
keep clouds around for most of the morning before scattering
out. This will keep us cooler today and have lowered highs by
several degrees amd are now only in the low to mid 80s. This
will keep heat indices below 90 degrees today, which is a
welcome change compared to yesterday.

Tonight...A weak shortwave will drop southeast out of MN,
likely just bringing a brief increase in clouds due to limited
sub-cloud moisture. Overnight lows to drop into the mid to upper
60s, with more fog potential possible early Wednesday.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 256 AM CDT Tue Aug 19 2025

A mostly dry and less humid stretch of weather is forecast for the
remainder of the work week and into the weekend. The large upper
ridge across much of the central CONUS to start the period, will
retrograde west and break down in response to an upper low moving
east across southern Canada and Hurricane Erin tracking north just
off the eastern coast. A large surface high will build over the
Great Lakes, with dry easterly flow developing late week that will
keep dewpoints in the 60s for the rest of the work week.
Seasonable highs in the 80s and lows in the 60s are forecast.

The next chance of precipitation will arrive Saturday, as the
aforementioned upper low drags a cold front through the area.
Moisture will be limited with the front and even if some
precipitation reaches the surface, all 12z ensembles show exceedance
probabilities of rain greater than 0.1" at 20% or lower. Behind
the fropa, an even cooler airmass will advect into the region.
Model 850mb temps are expected to drop into the 8-10C range by
Sunday, which is at/below the 10th percentile per SPC sounding
climatology for this time of year. While northwest flow will
bring this cooler air, something to watch for in later forecasts
will be whether or not wildfire smoke will be advected down
from Canada bringing more hazy skies next week. Highs only in
the 70s and lows in the 50s are likely Saturday through Tuesday,
which will feel more like late September! Enjoy this weekend
weather.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1232 AM CDT Tue Aug 19 2025

Expansive deck of LIFR/IFR stratus across WI to drift south into
portions of eastern IA and northwest IL this morning. In
addition, a very moist boundary layer and winds under 4kts will
allow for fog formation prior to sunrise. Some of this fog may
become dense, with highest probabilities (60-70%) occurring
after 11z at DBQ. Have left out of other TAF sites for now, but
will monitor trends upstream and amend if necessary. Model
guidance is mixed as to when conditions improve to VFR today,
but should start to scatter out by late morning and early
afternoon. Northerly winds under 10kts will be seen through the
period.

&&

.CLIMATE...
Issued at 256 AM CDT Tue Aug 19 2025

The latest Climate Prediction Center`s 6-10 day and 8-14 day
temperature outlooks has 60 percent or higher probabilities of below
normal temperatures for the last week of August across the entire
outlook area. Normal highs for this time of year are in the lower
80s and normal lows are in the upper 50s and lower 60s. This will be
a very much welcomed change compared to recent days, even a taste of
Fall perhaps!

&&

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

&&

$$

SHORT TERM...Gross
LONG TERM...Gross
AVIATION...Gross
CLIMATE...Gross