112
FXUS63 KDVN 201032
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
532 AM CDT Wed Aug 20 2025

.KEY MESSAGES...

- Patchy fog this morning, some of which could become dense
  prior and during the AM commute.

- There is a low chance (20-30%) of scattered showers and
  isolated thunderstorms today. No severe weather is expected,
  however some funnels may develop this afternoon.

- Dry and cooler stretch of weather begins late this weekend
  into next week. Below normal temperatures are likely.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 259 AM CDT Wed Aug 20 2025

Another warm and humid night is unfolding, with 2am temperatures
and dewpoints in the upper 60s and lower 70s. GOES 19 Night Fog
channel and surface observations show patchy to areas of fog
beginning to develop primarily along and east of the MS RVR and
in river valleys. Area radar mosaics show a few showers in
northeast IA and southwest WI. These were occurring along
850-925mb Td and 0-3km MLCAPE gradients per SPC mesoanalysis.
This was also the reason we had a persistent thunderstorm track
due south last evening in our far northwest.

Early This Morning

A very moist BL and calm winds will allow fog to develop and/or
continue, possibly becoming dense prior to AM commute. Areas
most favored are in southeast IA and east of the MS RVR. Will
continue to monitor trends and webcams for any need for an SPS
or Dense Fog advisory this morning. Any fog will quickly burn
off by 9-10a.

Today

A mix of sun and clouds will be seen today, with a low chance
(20-30%) of some scattered showers/isolated t-storms. Various
hi-res CAMs weaken the incoming showers from the north, before
developing more late this morning and afternoon mainly south of
I-80. Daytime heating in a moist environment will build
instability (CAPE over 1500 J/kg and steeping 0-3km lapse
rates) and while deep layer shear will be under 14 kts, some
stretching in the weak low level flow may allow for some funnels
to form as the precip activity moves south. RAP NST parameter
increases over 2 this afternoon. If any funnels occur, they will
be short lived. Highs today will be similar to yesterday, with
readings reaching the low to mid 80s. Overnight lows will drop
into the lower 60s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 259 AM CDT Wed Aug 20 2025

Thursday-Friday...a large area of high pressure will track over the
Great Lakes, bringing a dry and cooler easterly flow to the region.
While afternoon dewpoints may still reach the low to mid 60s, this
will feel noticeably less humid compared to last week. Near
seasonable highs in the upper 70s/low 80s and lows in the upper
50s/low 60s are forecast.

Friday Night-Saturday...a strong upper low moving east in southern
Canada will help drag a cold front through the CWA. This will bring
our next and likely only chance of precipitation in the extended.
Moisture will be the limiting factor locally, with better moisture
to our west as evident by 850mb theta-e progs off the 00z NAM, GFS,
and ECMWF. In any case, NBM PoPs have risen slightly (20-30%)
with the fropa for some very light showers overnight. Behind the
front, a much drier airmass will arrive for the start of a
beautiful weekend! Afternoon highs Saturday to top out in the
upper 70s/low 80s with comfortable humidity.

Saturday Night-Wednesday...a beautiful stretch of cooler and
comfortable weather is expected. WPC 500mb cluster analysis shows a
relatively deep upper low for this time of year over Ontario,
with a cooler airmass being advected down into the CONUS through
the period. 12z NAEFS output shows 850mb temps near the bottom
of spectrum (1th percentile) compared to climatology leading to
high confidence in below normal temperatures. The 00z
deterministic solutions this evening continue this trend with
850mb temps between 6-10C beginning Sunday night. This will
yield highs in the 70s and lows in the 50s (perhaps mid 40s
Monday night?) which will definitely bring a fall-like feel to
the area. Taking a quick look at record lows for the 26th show
that values are in the low 40s, so just out of reach for now.
As mentioned in a previous discussion, while this forecast is
spectacular we may need to watch for some wildfire smoke next
week with 500mb spaghetti plots showing a persistent cyclonic
flow aloft that may transport Canadian smoke into the CONUS.
Still a great end to the weekend and start to next week is
forecast!

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 531 AM CDT Wed Aug 20 2025

Model trends and surface observations now suggest more
optimistic conditions this morning regarding visibility
restrictions due to fog. Brief MVFR/IFR fog will be possible
at MLI/BRL this morning prior to 9am. Otherwise, VFR conditions
will be seen with northeast winds under 10 kts through the
period. A few VFR showers may develop this afternoon south of
I-80, but coverage too low to include mention at this time.

&&

.CLIMATE...
Issued at 256 AM CDT Wed Aug 20 2025

The latest Climate Prediction Center`s 6-10 day temperature
outlook has 85-90 percent or higher probabilities of below
normal temperatures for the Aug 25th-29th time frame. Normal
highs for this time of year are in the lower 80s and normal lows
are in the upper 50s and lower 60s.

&&

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

&&

$$

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