Lancaster, Wisconsin Weather Forecast Discussion

707
FXUS63 KARX 172310
AFDARX
Area Forecast Discussion
National Weather Service La Crosse WI
610 PM CDT Wed Sep 17 2025
.KEY MESSAGES...
- Scattered showers and thunderstorms through the weekend with
  increasing coverage heading to the weekend.
- Warmer temperatures continue through Thursday with highs
  mainly in the 80s, then drop into the 70s through early next
  week.
&&
.DISCUSSION...
Issued at 148 PM CDT Wed Sep 17 2025
Shower and Storm Chances Through the Weekend:
An upper-level low will continue to spin over the northern Plains
today and Friday. As it does so, various shortwave impulses will
impact the Upper Midwest. This will increase rain chances and
coverage of rain chances through the weekend, as the low gradually
shifts eastward. For todays convection, while a couple bands of
shortwave energy moves over the area, there is also some
vorticity advection with diffluence aloft and combining this
with 500 to 1250 J/kg of MLCAPE, showers and storms formed this
morning and will continue to do so through the afternoon. By
this evening, another shortwave impulse arrives and will help to
keep rain chances ongoing through the overnight. As the low
shifts eastward through the weekend, rain chances will continue.
Another thing to look at is moisture transport, which despite
weak flow aloft, does have a signal lingering through the
weekend as these shortwaves push through the region. This adds
to the confidence of showers and storms continuing to be
possible.
Severe storm potential, while quite low, cannot be ruled out. There
were some hail reports yesterday, however the mid-level lapse rates
were higher (closer to 7 C/km) whereas today and Thursday they will
be closer to 6 C/km. There was also higher amounts of instability
yesterday compared to today. With PWATs mostly ranging between 1.25
to 1.5" and storm motions being quite slow due to the weak
aloft, the main potential hazard would be localized heavy rainfall.
Uncertainty for Early Next Week:
Ensemble and deterministic guidance are disagreeing on what will
transpire next week. Both the deterministic GFS and EC have a low
that comes down from Canada and then deepens over the northern
Plains. The CMC does not have this but rather has a shortwave that
moves through early next week with the longwave trough staying north
of the US border. Ensemble cluster analysis has disagreements on the
strength and location of the longwave trough. This will be something
to watch as this could bring cooler temperatures, increased
precipitation chances, or windy conditions.
Temperature Forecast:
Today is the last day for locations to be in the low to mid 80s. By
Friday, highs are in the low to mid 70s. Depending on what happens
next week, temperatures are currently forecasted to be in the mid to
upper 70s. Low temperatures start out in the low 60s for tonight and
Thursday, then gradually decrease towards the mid to upper 50s by
early next week.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 604 PM CDT Wed Sep 17 2025
VFR conditions currently present across the area. Showers and a
few rumbles of thunder continue to move northeast into the area
which may lead to some low-end VFR/high-end MVFR visibilities
at the terminals in the next two hours. Chances for showers and
storms return later overnight with the potential for
redevelopment mainly along and west of the Mississippi with a
weak MCV moving into the area. Confidence is higher at RST than
LSE but still on the lower side given the smaller scale of the
forcing overall so have covered these potentials with PROB30s
for the time being. Low shower chances will continue through the
day tomorrow but confidence is too low on location to include
in this package. Better chances for showers look to come beyond
the scope of this package after 00Z tomorrow. Winds through the
period should be light generally out of the south to southeast
at less than 10 kts.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Cecava
AVIATION...Barendse

NWS ARX Office Area Forecast Discussion