770
FXUS63 KDVN 122317
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
617 PM CDT Fri Sep 12 2025

.KEY MESSAGES...

- Hot and moderately humid conditions are expected this weekend
  into next week.

- Aside from some low chances for rain tonight, we have to wait
  until next week for some better rain chances.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 228 PM CDT Fri Sep 12 2025

The heat is on its way. A mid and upper level ridge is building
over the Southern Plains and into the Middle Mississippi River
area. A shortwave trough is currently rounding the top of the
ridge, bringing a few showers and a stray thunderstorm from
central Iowa north through Minnesota. This will continue to
slowly progress eastward overnight before dropping south on the
other side of the ridge toward morning. Seeing upstream radar
echoes and a few rain reports has increased our confidence that
we`ll get at least scattered showers out of this as it crosses
our area tonight. A few thunderstorms are also possible as low
level moist advection accompanies the passage of the mid level
wave. Greatest chances will be in the east across northern
Illinois.

The ridge expands northward on Saturday into Sunday and we`ll
see some of the hottest temperatures of the year spreading into
our area. NBM forecast highs have continued to come down, more
in line with the rest of guidance in the low to mid 90s.
Mercifully, we don`t have a lot of humidity to accompany this
heat, so it won`t feel like the hottest day of the year.
Dewpoints only in the low to mid 60s will bring the heat index
up a degree or two over the air temperature, but staying largely
below 100. With the modest increase in humidity we will see an
increase in instability as well. We`re a bit unsure on the
degree of capping we`ll see, but it remains possible that we see
a few widely scattered afternoon showers and thunderstorms. Wind
flow will be weak, so anything that forms will tend to rise and
fall in place fairly quickly, affecting only a small area.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 228 PM CDT Fri Sep 12 2025

As we go into next week, multiple troughs to our west attempt to
push back the ridge, but generally fail. The ridge holds firm
over the Great Lakes through midweek before a trough finally
breaks through on Wednesday or Thursday. So for the first half
of the week we`ll be more under the influence of the ridge with
summer heat continuing. Guidance has come into a bit better
agreement compared to 24 hours ago on the idea that we will
finally see a trough push into the area Wednesday into Thursday.
So that gives us a clearer idea of when the heat will end and
when we`ll finally see some more widespread rain chances.

Among the 00Z ensemble guidance, 60 to 80 percent of members
produce measurable rain across our forecast area in the 24 hours
ending Thursday. Those are the highest numbers we`ve seen in a
while. NBM PoP is a bit lower still, mainly due to timing
uncertainty and the general tendency for NBM to take a few
cycles to catch up to an emerging consensus. So I`d expect these
PoPs to come up a bit more in the coming few forecast cycles if
this consensus continues and greater timing clarity emerges.
While there`s not a clear signal for severe weather, I wouldn`t
completely rule it out at this point. As the trough moves in we
will see better southwesterly flow aloft ahead of it, increasing
wind shear, and there will likely still be instability around
in the waning days of the hot, moderately humid air mass. So
there will at least be a few ingredients nearby and we`ll have
to see if they line up in time and space to produce any
significant threats.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 614 PM CDT Fri Sep 12 2025

Weak disturbance will fight dry air across eastern Iowa and
northern Illinois through 12z/13. Sprinkles and isolated SHRA
are possible through 12z/13. While the probability is under 5
percent, a rogue TSRA cannot be ruled out along/east of the
Mississippi River. Otherwise winds to become more southerly as
high pressure moves into the eastern Great Lakes.

&&

.CLIMATE...
Issued at 315 AM CDT Fri Sep 12 2025

Record High Temperatures:

September 13:
KBRL: 98/1927
KCID: 96/1930
KMLI: 97/1939
KDBQ: 96/1939

September 14:
KBRL: 99/1939
KCID: 96/1939
KMLI: 99/1939
KDBQ: 97/1939

&&

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

&&

$$

SHORT TERM...Kimble
LONG TERM...Kimble
AVIATION...08
CLIMATE...Uttech