Walnut Grove, Illinois Weather Forecast Discussion

304
FXUS63 KDVN 210543
AFDDVN
Area Forecast Discussion
National Weather Service Quad Cities IA IL
1243 AM CDT Sun Sep 21 2025
.KEY MESSAGES...
- On and off periods of showers and thunderstorms are expected
  through the weekend and the first half of next week. The
  threat for severe thunderstorms remains low.
- Lower confidence in forecast midweek as models differ
  dramatically on solutions.
&&
.SHORT TERM /THROUGH MONDAY/...
Issued at 130 PM CDT Sat Sep 20 2025
First of two shortwaves affecting the area is moving east this
afternoon. South of I-80 we have seen a pretty constant shield
of light to moderate stratiform rain. Some thunder has been
imbedded within this stratiform area. The better forcing for
ascent is well east of the area. As such, thunderstorms have
developed just south and east of the area.
Tonight, very weak H5 ridging is expected to transverse the
area. This will likely lead to a minimum in precip. Guidance
strongly suggests the development of fog tonight, especially
near daybreak. Some of this could be dense, especially across
the western CWA. At this time, decided to just mention in AFD
and patchy fog in the grids. Not confident in it being dense at
this time as H5 ridging is short-lived.
Tomorrow, a second wave is expected to pass north of the area. A
MCV is forecast to move across our area in the afternoon. With
the shortwave trof to the north and the MCV moving into the area
late in the morning, I think that we may be partly to mostly
cloudy across most of the area. This MCV will bring better shear
to the area. Looking closely at guidance there appears to be a
subtle wind shift where the very low levels of the environment
have a northerly wind as the MCV approaches the area. This leads
to a cooler surface temp. A more defined thermal boundary across
IL exists due to this wind. As such, thunderstorms could develop
ahead of the MCV in IL. Think we have a 1 to 2 hr window across
the east in the early afternoon when storms are possible. The
hodograph appears to be relatively straight at this time,
suggesting maybe some organized updrafts that attempt to split.
So small hail and wind cannot be ruled out. Also can`t rule out
any severe weather as well.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 130 PM CDT Sat Sep 20 2025
Little change in the long term forecast. Overall we will
continue to see daily chances (20-50%) of showers and occasional
thunderstorms Monday through Wednesday as the large-scale
weather pattern continues to feature a series of shortwave
troughs moving through the central CONUS region. Any storms that
develop are expected to be your garden variety storms (not
likely to become strong to severe) due to a lack of robust deep-
layer shear, but modest instability will be enough to generate
some storms at times. Midweek, the GFS is different than the
other deterministic models with overall kinematics. Precip
chances through Tuesday look good after this, things could
change.
In fact, by the time we get to Friday, we could see some relief
from the daily chances of precipitation as some of the guidance
suggests stronger mid-level ridging to develop, which would
help kick out any troughs that would otherwise support rain
chances.
In terms of temperatures, there doesn`t appear to be too much of a
change over the next several days, with highs maintained in the
upper 70s to lower 80s for most locations. A slight cooldown is
possible for Wednesday through Friday as winds shift more
northeasterly as opposed to southerly, with the NBM indicating highs
in the lower to middle 70s each day.
&&
.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1226 AM CDT Sun Sep 21 2025
VFR conditions were common across the area as of TAF issuance.
However, we continue to see a trend towards MVFR/IFR visibility
reductions due to fog across the area, most likely over
southeastern Iowa and points north. Fog is likely to begin over
areas that saw rainfall yesterday and expanding from there. The
coverage of fog will also depend on if we can get any breaks in
the cloud cover, which is expected to happen over southeastern
Iowa with cloud breaks seen on the latest satellite imagery over
south-central Iowa, expanding eastward. IFR/LIFR ceilings are
also expected for much of the area.
Eventually, conditions will improve back to VFR by the afternoon
hours Sunday, with a period of dry conditions expected. Another
round of showers could move across our south Sunday evening.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.
&&
$$
SHORT TERM...Gibbs
LONG TERM...Gibbs
AVIATION...Schultz

NWS DVN Office Area Forecast Discussion