Clermont, Iowa Weather Forecast Discussion

267
FXUS63 KARX 100809
AFDARX
Area Forecast Discussion
National Weather Service La Crosse WI
309 AM CDT Wed Sep 10 2025
.KEY MESSAGES...
- Scattered showers linger across portions of Iowa and Wisconsin
  early this morning with dense fog building in across portions
  of Minnesota.
- Warming through the weekend with highs topping 80 degrees for
  most Friday through Sunday
&&
.DISCUSSION...
Issued at 300 AM CDT Wed Sep 10 2025
This Morning - Tonight
Areas of showers and a few rumbles of thunder continue early
this morning across the area as an upper level shortwave trough
continues to trek east through the Upper Midwest. Showers will
continue to track in a general eastward direction through the
morning hours with some lingering showers across West Central
and Southwest Wisconsin after 12Z. As the rain and clouds clear
from the west, many sites across Minnesota have started to
develop dense fog. Depending on how quickly clouds clear out in
our area, a Dense Fog Advisory may be needed, likely for
portions of Southeastern Minnesota, by daybreak. Will continue
to monitor trends and traffic cams through the morning hours for
this potential.
As the shortwave and subsequent showers push off to the east
through the day, clouds will begin to lighten up by the
afternoon. With clearing skies, light winds, recent wetting
rains, and low dew point depressions, another round of fog looks
to be possible across much of the area tonight and into
tomorrow morning. Confidence in this is still on the lower end
for now but went ahead and included patchy fog in the forecast
for much of the area.
Thursday - Early Next Week
Temperatures: An upper level ridge is expected to build across
the Plains late this week with the ridge axis gradually pivoting
over the Upper Mississippi Valley as an upper trough over the
west coast moves into the Rockies and High Plains. Warm air is
expected to pool under this ridge, especially Saturday and
Sunday. Southerly mid to low level flow will allow anomalously
warm 850 mb temperatures to surge northward into the region
starting late Friday and continuing through the weekend. These
850 mb temps in question will be 7-10 degrees C above normal for
mid-September. With the increased heights aloft from the
ridging and warm 850 mb temperatures, highs will be rather mild
for the weekend. NBM 10.01Z probabilities show a 60-90% chance
of temperatures at or above 80 degrees on Friday. These only
increase for Saturday into Sunday with 70-100% chances of highs
at or above 80 degrees. The only places that could stay out of
the 80s would be far northern portions of Clark and Taylor
counties where probabilities tend to drop off. The GFS
continues to show a warm bias among the ensembles (the only
ensemble showing slight potential for 90s Sat/Sun) and it seems
to be skewing the NBM towards the higher end of guidance. This
is likely due to the recent stretch of dry conditions we`ve seen
over the last few weeks. Have decided to blend high
temperatures Saturday and Sunday down a few degrees to keep
highs more in line with the bulk of current guidance.
Temperatures these days are still expected to be 10+ degrees F
above normal in the mid to upper 80s.
Models are still struggling with how to handle the evolution of
the upper level pattern after Saturday. The general thought is
that our area would return to a more weak zonal pattern. This
would favor a more gradual return to near normal high
temperatures by mid-week (low to mid 70s). Until then, high
temperatures Monday and Tuesday are expected to hold in the
lower 80s for most.
Rain Chances: The aforementioned upper level ridge is expected
to weaken as we move into the weekend. However, as mentioned
earlier, models are struggling with how to handle the upper
level pattern after this happens. If we lean towards the more
zonal solution, which appears most plausible at this point,
this would keep some upper level energy around and would likely
move some shortwaves over the Upper Mississippi Valley. With
decent moisture still present across the area (pWats in the
1.25-1.5 inch range), this could create some chances for rain.
However, due to the lack of low level forcing and no discernible
foci for convection as of yet, confidence in where rain could
form is very low. Once the upper level pattern comes a bit more
into focus, PoPs will likely be refined but for now have kept
with the model blend which tends to keep PoPs in the 15- 30%
range through mid-week.
&&
.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1154 PM CDT Tue Sep 9 2025
VFR to MVFR conditions currently present across the region with
areas of light to moderate showers slowly pushing east/southeast
through the area. These showers will continue to move away from the
terminals and into Central/Eastern Wisconsin over the coming hours.
Behind these showers, areas of dense fog have begun to develop
across northern and central Minnesota. This is expected to fill
in behind the rain and could impact the RST terminal in the
coming hours. RST currently looks to be right on the edge of
where the dense fog will likely set up so have stuck with MVFR
visibilities and IFR CIGs for now though this may need to be
amended should the fog over-perform. LSE should stay clear of
the fog this morning and remain VFR. Winds will remain light
through the period becoming more northerly through the afternoon
hours.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Barendse
AVIATION...Barendse

NWS ARX Office Area Forecast Discussion