506
FXUS63 KARX 190531
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1231 AM CDT Wed Aug 19 2026

.KEY MESSAGES...

- High confidence in drier conditions for Wednesday decreases
  through Thursday as highest confidence for storms grazes northwestern
  peripheral counties from southeast Minnesota into central
  Wisconsin.

- Storm chances continue through Friday with low confidence
  (30%) for heavy rain as the main impact.

&&

.DISCUSSION...
Issued at 1231 AM CDT Wed Aug 19 2026

Dry Wednesday:

A cooler, drier airmass, seen through central Minnesota with mid 50
isodrosotherms on nighttime surface observations, is expected to sag
southeast through the forecast area through Wednesday concurrent
with anticyclonic flow solidifying drier conditions.

Storm Chances Thursday:

The high confidence in dry conditions decreases through Thursday as
upper level extratropical cyclonic flow, seen on GOES water vapor
imagery loops tonight over the Canadian Rockies enhances low level,
moisture-laden flow through the Upper Mississippi River Valley.
While current timing and strength of advecting flow and forcing
abates higher severe storm probabilities northwest of the local
forecast area, a slight eastern shift in machine learning severe
hazard probabilities over recent runs now grazes the western
periphery of the local forecast area with 5-15%. Therefore, while
current confidence is lower (<15%), farther eastern shift in model
solutions will be the initial locally impactful detail to remain
cognizant of in coming forecasts.

Heavy Rain Chances Friday:

While /most/ long term global ensemble models and their
deterministic counterparts agree on the accompanying low center
remaining relatively benign initially through Thursday, glancing
locally northern counties in west-central and central Wisconsin with
highest (100%) precipitation probabilities, deepening of the
accompanying lingering trough has increased probabilities for
heavier (0.1" & 0.5" /24hrs) rainfall across the northern /half/ of
the forecast area through Friday and into the weekend in most recent
ensemble runs. Should Thursday nights storm advection result in more
eastern solution to the accompanying frontal boundary, this threat
would shift east, potentially east of the local forecast area.
Therefore, although current WPC Excessive Rainfall Outlooks don`t
depict much of a threat, will be subsequent detail to monitor in
coming forecasts. Severe storm threat remains conditional on
clearing skies permitting low level diurnal instability to build as
long, skinny instability profiles in individual LREF member plumes
exhibit stunted hodographs until the stronger mid-upper level winds
Friday night into Saturday.

Mostly Cool & Dry Weekend:

In the wake of Friday`s storm potential, a cooler weekend is
expected with daytime highs from the 70s to low 80s through Monday.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1231 AM CDT Wed Aug 19 2026

Fog/low-stratus development will be the primary aviation
concern overnight into the morning hours with calm winds and
clear skies expected. Consequently, have already noticed some
development in the Mississippi River and various tribs with
bkn003 and 5sm observed at KLSE as of 05z. As a result, have
opted to include a prolonged period of vsby and cig reductions
through 13z this morning given winds likely staying calm
overnight. Otherwise, conditions will improve to VFR towards
daybreak with winds remaining light and variable throughout the
TAF period.

&&

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

&&

$$

DISCUSSION...JAR
AVIATION...Naylor