186
FXUS63 KARX 130721
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
221 AM CDT Thu Jun 13 2024

.KEY MESSAGES...

- Isolated to scattered strong/severe storms are still possible
  early this morning. Any additional strong and severe storms
  this afternoon look to be south of the area.

- Severe weather chances look less for this weekend, but still
  could see some localized flooding.

- Above-normal temperatures expected for next week. However,
  the temperature anomalies are uncertain. In addition, shower
  and storm chances are also uncertain. These uncertainties are
  due to questions on the western extent of the 500 mb ridge and
  strength of the cap.

&&

.MESOSCALE...
Issued at 221 AM CDT Thu Jun 13 2024

As a shortwave trough moves southeast through the area
early this morning, 850 mb moisture convergence along and ahead
of this trough will keep showers and storms going through dawn.
With DCAPE of a 1000 to 1500 J/kg, we will have to watch for
the potential damaging winds. However, as this convection moves
southeast, the low-level CIN will be increasing into the 400 to
500 J/kg range along and south of Interstate 90. This will limit
the damaging wind threat. The effective shear will remain in
the 25 to 35 knot range north of Interstate 90 and from 35 to 50
knots across the remainder of the area, so may have to watch
for some isolated to scattered supercells between 3 AM and 6 AM
south of Interstate 90. Hail would be the primary threat. As the
850 mb moisture transport shifts off to the east toward dawn,
the showers and storms will quickly come to the end across the
area.

&&

.DISCUSSION...
Issued at 221 AM CDT Thu Jun 13 2024

Today...

Another 700-500 mb shortwave trough and surface cold front will
move through the area today. Between 8 AM and 10 AM, a band of
showers and scattered storms will begin to move into the areas
north of Interstate 90 between 8 AM and 10 AM. While the deep
shear is favorable for supercells, the instability remains weak
generally less than 500 J/kg for much of the area. However,
there are some CAMs suggesting anywhere from 500 to 1500 J/kg in
our far southern areas. This might result in a few strong in
these counties, but overall the better severe weather chances
look to be south of our area.

The CONSShort precipitation chances looks too low, so used the
CAMs to raise the precipitation chances up into the categorical
range. This made sense considering the good agreement in timing
and location of their precipitation.

Father`s Day Weekend...

The models continue to show that a 500 mb ridge will build
northward and then move east of the region. As this occurs, a
warm front will lift northward into the region. On Saturday and
Saturday night, the better shear and instability remains to the
southwest of the area. As a result, it looks like the severe
weather chances have dramatically lessened for this time
period.

The warm front will move north across much of the area on
Sunday. As this occurs, temperatures will warm well into the
mid- and upper 80s. There may be even some lower 90s. Due to
differences in the low level dew points, there continues to be
some differences in the 0-1 km mixed-layer CAPEs. The GFS has
CAPEs between 1000 and 3000 J/kg. Meanwhile, the ECMWF is in the
1000 to 2000 J/kg range. The GFS has a weaker 500 mb ridge and
this results in a cold front dropping south into the region on
Sunday night. If this does indeed occur, the strongest 0-6 km
shear remains post frontal, so organized severe weather chances
look to be low. Meanwhile, the ECMWF and Canadian has a
stronger ridge and capping over the region, so there are
questions on whether any showers and storms will even develop.

With a mean precipitable water value around 1.5 inches and warm
cloud layer depths climbing to around 4 km, any showers and
storms that do happen to develop will be efficient rain
producers. This could result in some localized flooding.

Monday through Wednesday...

There continues to be uncertainty on the location of the eastern
U.S. 500 mb ridge. Both the ECMWF and Canadian have their ridge
further west into the Upper Mississippi River Valley. This
results in well-above normal temperatures (mid-80s to mid-90s)
and dry. Meanwhile, the GFS is further east with the ridge and
this results in temperatures more in the 80s with periodic
showers and storms. Some of these could be strong to severe. In
addition, with warm cloud layer depths of around 4 km and and
precipitable water values of 1.5 to 2 inches, there will be the
potential for localized flooding.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1149 PM CDT Wed Jun 12 2024

The potential for thunderstorms at LSE/RST overnight remain the
main concern over the next TAF cycle. Confidence has decreased
in occurrence over the past several hours given latest trends in
observations and short term guidance. Have therefore altered
prevailing mentions of TS to TEMPO groups and adjusted timing.
Otherwise, abundant low level moisture, particularly if storms
occur, suggest fog at LSE may occur around sunrise Thursday.
Given low confidence, have elected to only include an MVFR
mention at this time.

&&

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

&&

$$

MESOSCALE...Boyne/Skow
DISCUSSION...Boyne
AVIATION...Ferguson