495
FXUS63 KARX 011047
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
547 AM CDT Wed Oct 1 2025

.KEY MESSAGES...

- Dry conditions and above normal temperatures continue through
  the end of the week.

- Probabilities for rain increase this weekend into early next
  week (20-40%).

&&

.DISCUSSION...
Issued at 253 AM CDT Wed Oct 1 2025

Today - Saturday: Dry and Very Mild

The main driver of weather across the region continues to be a
stout upper ridge, currently centered over the Western Great
Lakes. A weak shortwave trekking through the ridge is creating
ample cloud cover for much of the Midwest this morning. This
cloud cover will limit diurnal heating this afternoon which
should keep high temperatures lower than previous days in the
upper 70s to low 80s. We`re not expecting any precipitation with
this shortwave passage as 01.06 RAP/HRRR soundings show an
abundance of dry air in the low to mid levels with a low level
cap expected to remain in place through much of the day.

Heat is expected to continue to build across the North Central
CONUS through the end of the work week and into Saturday. The
ridge should flatten out and begin to phase east with a surface
high pressure looking to build across the eastern seaboard by
Friday. This will create a large fetch of warm southerly flow
into the Northern Plains and Upper Midwest. In addition to the
increasing surface warmth, with the subsidence from the ridge
still prevailing over the region, this will keep the dome of
warm 850/925 mb temperatures already in place overhead. 850 mb
temps are expected to range between 15-18 deg C (roughly 8-13
deg C above normal) through this weekend, peaking Friday into
Saturday. The EC ensemble EFI is showing a 90-99% chance of
abnormally warm temperatures with an SOT of 1 over the Driftless
Region both Friday and Saturday. This indicates that there is
strong potential for highly unusual to potentially extreme
temperatures for early October. NBM forecast highs for each day
are in the mid to upper 80s and right around the 90th percentile
for NBM high temps. Probabilities for highs at or above 90
degrees remain low at less than 30% for areas across NE Iowa and
the immediate Mississippi River Valley but have gone up from
previous forecasts, consistent with the uptick in temperatures.
Records could be broken with these high temperatures both Friday
and Saturday, though Saturday looks more likely. Record highs
for RST and LSE for Friday are 93 and 91 respectively, both
occurring back in 1997. With forecast highs not quite reaching
the 90 degree threshold, these records appear safe for now.
Record highs for RST and LSE for Saturday are 84 and 88
respectively, both occurring in 2005. These appear much more
likely to fall with the current forecast highs for RST and LSE
sitting at 86 and 87 respectively.

With this increase in temperatures and prolonged period of dry
conditions, fire weather concerns look to increase through the
end of the week. Through Friday, winds are expected to remain
too light with minimum RHs too high to lead to elevated/near
critical fire weather conditions. Concern does increase for
Saturday as a surface low pressure system begins to approach
from the west with southerly winds increasing to between 15-25
mph west of the Mississippi River. There remains disparity in
models as to how strong the surface low will be by Saturday and
since this will play a key role in winds, it will be something
to keep an eye on in the coming days. Minimum RHs that day look
to stay above 30 percent with the lowest RHs likely not co-
located with the strongest winds. The warm temperatures and dry
conditions will also allow for fall vegetation to continue to
dry out and prime fine fuels across the region. The areas of
greatest concern in regards to dry vegetation/soils will be West
Central and Southwest Wisconsin.

Sunday - Mid Next Week: Rain Chances Return

A strong upper trough is expected to move onto the West Coast
late Friday into Saturday and trek east towards the Rockies into
the weekend. This will transition our area into southwest flow
aloft. There remain differences in the 01.00 GEFS/EPS/GEPS
ensemble means as to how this trough will evolve through the
weekend and into early next week (timing, amplitude, etc.) but
the general consensus keeps us in southwest flow aloft through
early/mid next week. There is also decent consensus on a surface
low forming somewhere across the Northern Plains and lifting
northeast into Canada. A cold front dragging behind it is
expected to swing through the region, giving some low level
focus for convective development Sunday into Monday. AI/ML
severe probs for Sunday have increased slightly from days
previous but there is still significant uncertainty regarding
this potential as whether enough buoyancy will be in place and
if the best shear will be co-located along the front or lag
behind both remain in question at this stage. Overall rain
chances start with the approach of the cold front early Sunday
and continue into mid next week with transient shortwaves
potentially passing overhead in the southwest flow aloft. Cold
air advection behind the cold front will help to bring
temperatures down back closer to normal with post-frontal highs
by Tuesday in the mid 60s to around 70.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 547 AM CDT Wed Oct 1 2025

VFR conditions will continue through the TAF period. Sustained
southeast winds of 10 to 15 mph are expected today. High level
clouds around 20kft to 25kft linger into the overnight period.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.

&&

$$

DISCUSSION...Barendse
AVIATION...Cecava