Coon Valley, Wisconsin Weather Forecast Discussion

431
FXUS63 KARX 180551
AFDARX
Area Forecast Discussion
National Weather Service La Crosse WI
1251 AM CDT Thu Sep 18 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 /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1231 AM CDT Thu Sep 18 2025
Low confidence TAF due to persistent scattered shower/storm
potential through the 18.06Z period. Radar imagery at 18.06Z TAF
issuance shows an arc of showers quickly progressing north
through southeast Minnesota and western Wisconsin into west-
central Wisconsin. KLSE ASOS registered a Trace with these
passing showers from 0515-0540Z.
The persistent weather pattern causes transient IFR visibility
potential from scattered storms primarily during the daytime
hours today. Higher, widespread storm chances progress east
across the forecast area tonight, as early as the 18-24 forecast
hour. Initial local higher storm chances primarily affect
smaller airports in southeast Minnesota (KAUM, KTOB) and
northeast Iowa (KCCY). Initial timing and eastern extent limits
overall confidence, below mentionable for KRST TAF, and will
need to be further investigated in coming TAFs (12-18hour
forecast).
FRIDAY THROUGH MONDAY.. Widespread, high storm chances Friday
and Friday night (60-80%). Low to moderate storm chances
(20-50%) Saturday through Monday.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Cecava
AVIATION...JAR

NWS ARX Office Area Forecast Discussion