058
FXUS63 KARX 111912
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
212 PM CDT Mon Aug 11 2025

.KEY MESSAGES...

- Rain chances (50%) in southwest Wisconsin and adjacent
  northeast Iowa tonight as another system brushes the area.
  Any storms will be able to produce decent rain rates and
  possibly isolated 1" totals but flooding is not currently
  expected.

- Thunderstorms may (40%) occur Tuesday, mainly east of
  the Mississippi. A stray strong storm may occur as well.

- Very warm and muggy conditions return Friday

- Friday and Saturday may bring thunderstorms to the region.
  Trends for severe storm potential will need to be monitored
  over the coming days.

&&

.DISCUSSION...
Issued at 210 PM CDT Mon Aug 11 2025

Rain chances tonight:

17z WV satellite reveals an upper disturbance moving northeast over
the NE/IA/MO/KS quad-state area. At the surface, weak SW-NE boundary
appears to be present roughly along a CCY-ISW line with dewpoints in
the upper 60s and lower 70s to the southeast and in the lower 60s
northwest. Tonight, the upper disturbance should kick off showers
and thunderstorms to our southeast and these will likely (60%)
affect portions of far SW WI and adjacent parts of NE IA. Per 11.12z
HREF, PWAT values will likely (50-80%) exceed 1.5", so localized
heavy rain may occur. That said, storms should be moving northeast
at 20 mph or greater so am not too concerned about flooding
potential, although a few localized issues could occur given the
abundant rainfall over the past weekend.

Tuesday shower and thunderstorm potential:

Tuesday, longwave upper trough, currently located over the Canadian
Prairies, swings eastward over Lake Superior. While best moisture -
the moist axis southeast of the weak boundary draped across the area
today - will be displaced to the southeast, still enough residual
moisture for appreciable instability to develop as the mid levels
cool. Indeed,  11.12z HREF has a 60% chance for SBCAPE to top 1000
J/kg east of the advancing cold front. Thus, another round of
convection appears likely (60%) for the eastern half of the area as
the cold front pushes parcels upward. With progged sfc-6km bulk
shear around 30 kts, cannot rule out a strong to perhaps severe
thunderstorm. Unidirectional shear profile suggests rotating
updrafts may struggle to persist, limiting top end hail concerns.
Well-mixed surface layer would support potential for a few
strong downdraft gusts, however.

Very warm and muggy Friday:

Friday afternoon, both NAEFS/ECENS 700mb temperatures look to
surpass the 97.5th percentile as 850/925mb humidity surpasses the
90th percentile. The end result looks to be heat index values in the
90s perhaps approaching 100 if everything comes together.

Thunderstorm potential Friday and Saturday:

Aforementioned return to moist conditions will leave the area
vulnerable to potential thunderstorm development across at least
Friday and Saturday afternoon/evening as quasi-zonal flow aloft
occurs. While potential instability will certainly be supportive of
convective development, main point of uncertainty looks to be the
position and magnitude of an upper level ridge centered to our south
as this both may leave the area capped and also keep stronger flow
aloft - and thus appreciable deep layer shear - to our north. That
said, 11.00z LREF shear/instability joint probabilities, GEFS-based
ML severe outlooks, and ECENS-based neural network severe outlooks
suggest we`ll need to keep an eye on both days for severe storm
potential, especially for the northern half of our CWA.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1245 PM CDT Mon Aug 11 2025

Broken mid- and high clouds will move through the area through
tonight as a shortwave trough moves northeast through the Mid
Mississippi River and into the southern Great Lakes. The clouds
will become scattered toward morning which will provide a window
late tonight and Tuesday morning for IFR/MVFR ceilings and
visibilities across parts of northeast Iowa and southwest
Wisconsin. In addition, there will be some fog potential in the
Mississippi River tributaries. The boundary layer winds and
winds aloft look too strong over the main channel of the
Mississippi for widespread valley fog.

&&

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

&&

$$

DISCUSSION...Ferguson
AVIATION...Boyne