La Crosse, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

520
FXUS63 KARX 141845
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
145 PM CDT Wed May 14 2025

.KEY MESSAGES...

- Isolated showers and storms possible this afternoon (20-40%)

- Severe thunderstorms are possible Thursday afternoon-evening.
  Greatest risk along and east of the Mississippi River. Large
  hail (2"+) and tornadoes are the primary hazards, but damaging
  winds are possible.

- A busier weather pattern is expected this weekend into next
  week.

&&

.DISCUSSION...
Issued at 142 PM CDT Wed May 14 2025

Isolated Showers and Storms this Afternoon

Similar to yesterday, various shortwaves move northwestward
into the area today. These shortwaves combined with increasing
moisture via southeasterly flow and increasing instability via
diurnal heating will (and have begun to) allow for isolated to
scattered shower and thunderstorm activity again this afternoon.
Showers and storms will continue into the evening hours before
waning after sunset. Storms are expected to remain weak.

Severe Weather Thursday Afternoon and Evening

Model guidance is in much better agreement with the timing and
location of the surface extratropical cyclone expected to deepen
over the northern Great Plains tonight and Thursday in response to a
500hPa trough ejecting eastward off the Rocky Mountains.

Looking into the kinematics of Thursday, a 60-70kt jet streak
overspreads the Upper Midwest during the day, increasing 0-6km bulk
shear to 40-50kts with the orientation of these shear vectors
nearly orthogonal to the surface cold front. 0-3km shear shows
decent curvature, with the associated SRH values at 200-300
m2/s2. Overall, kinematics are supportive rotating updrafts and
a discrete storm mode. Storm motion will be quick given the
strong cloud layer winds.

From a thermodynamic perspective, "fat" CAPE profiles in excess of
2000 J/kg continue to be depicted across the region along and ahead
of the approaching cold front (above 3000 J/kg looking at the
RAP/HRRR) as surface dewpoints climb into the mid 60s.
700-500hPa lapse rates also remain impressive, forecast to be
7.5-8C/km. Model soundings continue to suggest some drier mid-
level air, less so than previous runs, but DCAPE values around
1000 J/kg and WBZ heights around 10kft remain.

Overall, storms that develop Thursday afternoon are expected to
quickly become severe. Currently thinking storms will initiate
near the Mississippi River around 2-4pm, moving quickly
eastward into eastern Wisconsin by 6-7pm. Given the shear
orientation orthogonal to the surface cold front, supercells are
expected, forming a broken line along the cold front. The
primary hazards are large hail of 2 inches or greater and
tornadoes. Damaging winds are a secondary, but very possible,
threat. Given the fast motion of the storms, flash flooding is
not expected.

Busier Weather Pattern Ahead

The area of low pressure associated with Thursday`s severe
weather will slowly shift eastward as we head into the weekend.
Winds increase substantially in the 925-850hPa layer Thursday
night into Friday around the low, upwards of 50kts. Model
soundings suggest an inversion should be in place across much of
the area overnight, but stronger gusts over 30kts are possible,
especially during the day Friday.

As the low slowly moves eastward Friday into Saturday morning,
additional showers will move through the area. Upper ridging
builds into the area Saturday into Sunday bringing a brief drier
period. Ridging then begins to break down early next week as
another trough developing across the United States, brining
additional precipitation chances into next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1248 PM CDT Wed May 14 2025

Isolated to scattered showers and storms are on the table again
today, similar to yesterday. It is challenging to pin down
exactly when and where a storm will develop, but along and east
of the Mississippi River is favored for the most development,
but everywhere may see some showers/storms. Have included
PROB30 groups at both RST/LSE given this possibility. Any
impacts from showers/storms will be brief, and development
should begin to wane after sunset.

An area of lower clouds moves northward into Thursday morning.
Models suggest MVFR ceilings are possible, around 30-40%, but
somewhat uncertain about how low the clouds may be. Southeast
winds then increase in speed Thursday.

&&

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

&&

$$

DISCUSSION...Falkinham
AVIATION...Falkinham