877
FXUS63 KDVN 291044
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
544 AM CDT Fri Aug 29 2025

.KEY MESSAGES...

- Mild late-summer temperatures continue through the weekend.
  Other than a stray shower at times, expect mostly dry
  conditions through early next week.

- A cold front midweek brings a better chance of rain followed
  by much cooler temperatures.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 243 AM CDT Fri Aug 29 2025

Yesterday`s cold front has already begun to wash out as high
pressure shifts eastward into the Great Lakes today. Low level
winds turning southerly on the back side of the high trigger at
least weak moist advection across much of Iowa and Minnesota
generating enough instability this afternoon for a few stray
showers or perhaps a thunderstorm. The greater potential for
this is further north in Minnesota, but as we`ve seen the last
few days it doesn`t take much to trigger some stray showers
especially with a subtle shortwave trough aloft. Among the 00Z
HREF high resolution guidance, approximately 20 to 40 percent of
members produce measurable rain within the area of greater
moisture this afternoon. For that reason, we`ve added some low
end PoP this afternoon, although if a shower does occur it won`t
amount to much considering the lack of significant or deep
moisture. With the cool surface high over the Great Lakes we`ll
see temperatures a few degrees cooler today than yesterday for
most of the region (in the 70s), although some warmer
temperatures remain over the southwestern forecast area where
the cooling influence is not as strong.

Thunderstorms upstream over Minnesota should be dying out by the
time they reach our northern forecast area this evening,
although we have included some low end PoP for the potential for
remnant showers extending into northwest Illinois. More
extensive cloud cover from this activity will likely prevent
stronger nocturnal cooling, holding temperatures into the 60s
and upper 50s overnight. Saturday will be pretty similar to
Friday with temperatures in the 70s to low 80s with perhaps a
shower or storm in the afternoon.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 243 AM CDT Fri Aug 29 2025

There are some changes coming in the long term forecast.
Northern stream ridging moves into the Canadian prairies this
weekend, gradually pushing aside the persistent troughing over
the eastern Great Lakes and New England. But by the time this
ridge begins to nudge closer to our region, it will already be
being overtaken by a more robust trough dropping quickly south
out of the Canadian Arctic. This trough will be ushering in much
cooler air into the Upper Midwest for the middle to later part
of next week.

At the surface, high pressure over the western Great Lakes
gradually weakens and shifts east through early next week.
Temperatures remain near or slightly below normal for late
summer, mainly in the 70s for highs and 50s for lows. The focus
for daily showers and thunderstorms remains off to the west
where shortwave troughs embedded in the northwesterly jet
produce more frequent showers and storms over the Northern
Plains and into western Iowa. We can`t rule out a stray shower
mainly across our Iowa counties most days, but the chances
remain fairly low this far east with dry conditions generally
prevailing.

The best chance of rain this week comes with the arrival of the
trough and associated cold front Tuesday night into Wednesday.
Among the 00Z long range ensemble guidance, 40 to 60 percent of
members produce measurable rain with the passage of this
feature. Rain amounts won`t be excessive as there`s a lack of a
deep moisture connection ahead of the front and it does move
through fairly quickly.

The air mass taking aim at us behind next week`s front is
coming straight out of the Canadian Arctic, and it`s likely to
be at least a bit cooler than the last one we saw. There`s still
some variability in the guidance on how deep this trough is,
where its core tracks, and how long it lingers. So there is some
corresponding uncertainty in just how cool we get and for how
long. For daytime temperatures in this air mass we take a look
at 850MB temperatures to get a feel for what can be achieved in
fully mixed conditions. 850MB temperatures in the 2-6C range
suggest highs in the 60s with that variability also showing up
in the NBM interquartile range increasing to about 7 to 10
degrees late this week. On the cooler side of that range, some
areas may not get out of the 50s. As far as nighttime
temperatures, we look to dewpoints for a feel for what the air
mass is capable of if we can get a clear, calm night. Dewpoints
forecast in the low 40s suggest that if we do get a night of
strong cooling then temperatures could approach or perhaps
exceed those dewpoints in spots. However, it`s unclear at this
stage whether we`ll see the right conditions lining up for us to
get a full taste of this chill. With such a strong trough
there`s a good chance that winds behind the front remain strong
enough to prevent good nighttime cooling at least initially.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 543 AM CDT Fri Aug 29 2025

Light winds become southerly today in otherwise VFR conditions.
There`s a low chance of afternoon showers or even a
thunderstorm, but confidence is too low to include in any TAF at
this time.

&&

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

&&

$$

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