165
FXUS63 KDVN 011034
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
534 AM CDT Mon Sep 1 2025

.KEY MESSAGES...

- Seasonable temperatures and dry weather is expected through
  Tuesday.

- A strong cold front on Wednesday brings light rain with much
  cooler temperatures for the rest of the week.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 224 AM CDT Mon Sep 1 2025

Surface high pressure continues to nudge eastward this morning,
with its center pushing into northern New England today. The
cool, dry influence it`s had on our weather is similarly
gradually waning, with temperatures today warming a degree or
two over yesterday`s values. A persistent shortwave trough over
Nebraska has kept rainy conditions across Nebraska and western
Iowa, but has thus far remained too far west to bring
significant impacts to our forecast area, though some mid and
high level cloud cover does stretch across our southwestern
zones. This trough finally gets the boot today, beginning to
trek to the SSE toward Missouri, but confidence is high that
rain associated with this will remain west of our forecast area
again today. Cloud cover may hold temperatures back a few
degrees for northeast MO and southeast IA, but we still expect
temperatures to reach the upper 70s to near 80. For Tuesday
we`ll see even less influence from the departed shortwave, so
more sunshine should allow temperatures to warm to their warmest
levels of the week, in the low 80s for most.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 224 AM CDT Mon Sep 1 2025

For our next weather maker, we have to look to the north. A
potent trough is currently moving east across the Canadian
Arctic, but a secondary trough behind it will begin to move
south today, dragging a cool, Arctic air mass with it. The core
of this trough digs to about Duluth, MN by Wednesday where it
stalls and deepens for a day or so before wobbling off to the
northeast later this week. The end result for us will be at
least one strong cold front and a shift toward much cooler
temperatures later this week and potentially through the
weekend.

Long range guidance continues to be in good agreement that the
initial cold front moves through our region during the day on
Wednesday. We have a rather large temperature gradient across
our forecast area on account of that daytime frontal passage.
For southern areas where it arrives later, we do warm into the
upper 70s to near 80 for one more day, but once the front blows
through we drop back into the 60s. Light rain and perhaps a few
thunderstorms accompany the front as it moves through on
Wednesday. Among the 12Z ensemble guidance, 90 to 100 percent of
members produce measurable rain across the forecast area in the
24 hours ending Wednesday evening, so confidence remains high
in a widespread period of rain. However, moisture is somewhat
lacking, relying on remnant moisture over the Plains rather than
a fresh pull of Gulf moisture. While some limited instability
exists for thunderstorms, it`s currently expected to be quite
weak, and greater wind shear is delayed until after the frontal
passage. As a result we concur with SPC that the severe weather
threat is low.

There continues to be good consensus on the arrival of the cool
air, including on just how cool it will be. The coolest day will
likely be Thursday as cold advection is strongest and the air
mass is freshest. Most of the day will be spent in the 50s to
low 60s depending on how deep the mixing is behind the front and
how extensive the cloud cover will be. Gusty winds may
accompany the cool air, making it feel even cooler.

The greatest source of uncertainty of late has been how long the
cool air lasts, as guidance has varied considerably on the way
the upper trough wobbles from Thursday onward. There`s now
beginning to be a greater consensus that while the initial
trough begins to pull away to the northeast on Thursday, another
trough drops southward on the back side bringing another cold
front early Friday. So just when we start to recover from the
initial cold blast, we get another shot of cool air. Whether we
get another round of rain is a little more uncertain and
dependent on how deep this second trough is. Model solutions
with a deeper, sharper trough squeeze more precipitation out of
it as it moves through Friday morning. Among the 12Z ensemble
members, 50 to 70 percent produce measurable rain in the 24
hours ending Friday afternoon. NBM PoP has begun to respond with
the greatest chances peaking at about 30 percent early Friday
morning. This will likely increase as the timing of this wave
becomes better resolved.

NBM forecast temperatures this weekend have continued to nudge
downward as confidence is building that broader troughing
lingers and at least one additional cold front will keep the
cool air in place longer. It now looks likely that we`ll spend 3
or 4 days in the 60s to low 70s. Our coldest night will likely
be Saturday night into Sunday morning when surface high pressure
moves into the region. Whether we can reach the full potential
of this air mass (lows in the low 40s to upper 30s) will depend
on whether we can get clear, calm conditions. Some guidance
continues to show additional shortwave troughs rotating around
the back side of the broader trough even into Sunday morning
which would have the effect of bringing additional cloud cover
and spoiling our chance at a clear, calm night. After Sunday,
confidence grows that we`ll be on a warming trend. Ridging
builds in from the west behind the departing trough and surface
winds turn southerly again. An early look at next week suggests
temperatures warm back to near or slightly above normal levels,
in the upper 70s to low 80s.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 534 AM CDT Mon Sep 1 2025

Light winds continue across the region today under a mostly
clear sky. VFR conditions continue.

&&

.CLIMATE...
Issued at 300 AM CDT Sun Aug 31 2025

With the upcoming cool air mass, some daily record lows and
record cool highs are in range of being tied or broken. The
current records for Thursday and Friday are shown below:

RECORD COOL HIGH TEMPERATURE:
              September 4      September 5
Moline        61 in 1874       61 in 1876
Dubuque       58 in 1994       61 in 1920

RECORD LOW TEMPERATURE:
              September 4      September 5
Moline        39 in 1974       42 in 1974
Dubuque       38 in 1974       44 in 1988 and others
Cedar Rapids  38 in 1974       42 in 1974
Burlington    40 in 1974       44 in 1962

&&

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

&&

$$

SHORT TERM...Kimble
LONG TERM...Kimble
AVIATION...Kimble
CLIMATE...Kimble