312
FXUS63 KARX 150404
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1104 PM CDT Wed Aug 14 2024

.KEY MESSAGES...

- From Tonight into Thursday morning, there will be a round of
  showers and storms. Some of these could produce heavy rain.

- From Thursday afternoon into Thursday evening there will be an
  additional round of showers and thunderstorms. While rain
  rates look to be less, there could be some strong to severe
  storms. This is highly dependent upon afternoon cloud cover.

&&

.DISCUSSION...
Issued at 319 PM CDT Wed Aug 14 2024

Tonight through Thursday night...

The 14.12z models continue to show that a low pressure system
will move slowly east northeast through the area and gradually
deepen. Even though it will be deepening, the 0-6 km shear is
rather messy. This is especially the case in the 3-6 km shear.
The 0-3 km shear look a bit better, but its shear is in the
20 to 30 knot range. Unlike yesterday, there appears to be a bit
more instability in the wake of the morning convection. Many of
the models are suggesting 1-2K J/kg 0-1 km CAPES. There are
even a few models up to 2500 J/kg. This will all depend on
the cloud cover during the afternoon. In addition, there will be
some moderate to steep mid-level lapse rates. This could result
in some pulse severe storms, so the marginal Day 2 SPC outlook
looks reasonable.

With precipitable water values increasing to around 2 inches
and warm cloud depths of 3.5 to 4 km, these showers and storms
will be highly efficient rain producers. WPC has the area under
marginal risk for excessive rain. It continues to look like most
areas will see anywhere from 0.75 to 1.5 inches of rain. The
24-hour HREF QPF ensemble localized probability matched mean
has an area of 2-3 inches from northeast Iowa northeast into
north-central Wisconsin.

Friday...

The 14.12z models continue to show that surface low will
continue to move east northeast into the northern Great Lakes.
This will keep scattered showers and maybe a few storms as
shortwaves rotate around this low. With limited instability and
the best moisture to our east, rainfall totals still look to be
on the lighter side.


Days 8 to 14 (August 22-28)...

Unlike the past several days, it looks like there will be a far
less amplified 500 mb pattern across the northern United States
and the Canadian Prairies. As a result, it is looking like the
omega high in the 6 to 10 day period will quickly flatten as a
series of shortwave troughs move through this region.

Northwesterly flow aloft will bring unseasonably cool air south
into the region. As a result, the chances for below-normal
temperatures have increased across the Upper Mississippi River
Valley east into the Great Lakes. While the temperatures look a
bit cooler, there continues to be enhanced chances for drier
than normal.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1105 PM CDT Wed Aug 14 2024

Scattered showers will continue into the early morning hours.
Shower coverage is expected to increase as a band of
precipitation moves through the area roughly between 07Z and 15Z.
As coverage increases, there is an increased chance for
thunderstorms to occur, between 20 and 40%. After this band
exits the area, scattered showers will remain in the area into
the afternoon before scattered thunderstorms become possible
through the afternoon. CIGS will lower into MVFR/IFR flight
categories during the overnight before going back to VFR for
Thursday afternoon. Predominant southeast winds through Thursday
morning before shifting more westerly for the afternoon and
evening.

&&

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

&&

$$

DISCUSSION...Boyne
AVIATION...Cecava