013
FXUS63 KARX 101810
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
110 PM CDT Mon Jun 10 2024

.KEY MESSAGES...

- Scattered showers and thunderstorms Tuesday. Marginal risk
  (level 1 of 5) for severe weather with gusty winds and hail
  as the main threats.

- Thunderstorm chances return Wednesday night. Higher severe
  risk compared to Tuesday with more focus over Minnesota and
  west central Wisconsin (level 2 of 5).

- Below normal temperatures for Monday/Tuesday, but a warming
  trend into the weekend with temperatures trending normal to
  above normal with highs in the 80s.

&&

.DISCUSSION...
Issued at 341 AM CDT Mon Jun 10 2024

Tue: Marginal Risk (level 1 of 5) for Severe Weather

A ridge will be over the area for the beginning of the week. Heading
into Tuesday, a shortwave trough dips down from Canada and brings
the area its next chance of precipitation. Moisture transport
increases Tuesday afternoon just as dewpoints approach the upper 50s
to near 60F. Guidance continues to show some showers moving out
ahead of the main trough in the morning to early afternoon. As the
trough gets closer, instability increases with MLCAPE values
potentially getting as high as 1000 J/kg and bulk shear, 0-6km,
ranging from 40 to 50kts. The key for these storms is
sufficient daytime heating. Depending on how the timing of the
showers that move through and how long they stick around will
help in determining on unstable the atmosphere can get. Another
thing to aid in increasing instability is the warm southwest
flow that will increase as 850hPa flow increases during the day.
After the early showers move through, isolated to scattered
thunderstorms are expected to form and CAMS have shown this
occurring in the late afternoon to early evening on Tuesday.
With these ingredients in place, SPC has gone ahead and placed a
marginal risk (level 1/5) for severe weather to occur.

Wed into Thu: Thunderstorm Chances and Severe Weather

The ridge flattens out for mid-week allowing for a couple of
shortwave troughs to pass through the region. The first disturbance
has deeper moisture and stronger southwest flow allowing for
moisture transport to increase as a result. If this convergent zone
ends up maintaining its strength, there could be a risk of heavy
rainfall across the area. Westerly flow is in place for the mid
levels while southwest flow will be in place for the lower levels.
The area will also be in the exit region of a jet that will be
moving into the area. Strong instability and high lapse rates are
expected across South Dakota and Minnesota. Bulk shear across this
area is forecasted to be in the 40 to 50kt range. Storms are
expected to fire up in this area during the afternoon and move
eastward into the overnight period. Given these stronger ingredients
compared to Tuesday, current SPC outlook has a slight risk (level 2
of 5) for portions of southeast Minnesota and west central
Wisconsin, with a marginal risk (level 1 of 5) for the rest of the
forecast area. Temperatures will be a bit warmer with the stronger
southwest flow, with highs generally between 5 to 8F above normal.
This means high temperatures around the area are forecasted to be in
the upper 70s to mid 80s. Current NBM probabilities have between a
20 to 30% chance for parts of northeast Iowa and river valley
locations to hit 90F both days.

Fri through the Weekend: More Storm Chances?

As the weekend approaches, the ridge strengthens and drier
conditions are expected for Friday and Saturday. There is something
else to watch however, as ensemble and deterministic guidance
continue to show a closed low over the Intermountain West. This low
is forecast to move into the Upper Mississippi River Valley later
this coming weekend. This will be another potential to watch as the
weekend gets closer.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 110 PM CDT Mon Jun 10 2024

VFR conditions look to continue through much of the TAF period.
Light winds will turn more southeast to south, increasing into
the morning/day on Tuesday. Otherwise, light shower chances move
in from the west Tuesday morning. Expect there will be some
updates and refinements to timing with following issuances. With
models showing limited instability with these early showers,
have not included thunder in the TAFs. However, additional
isolated shower and thunderstorm chances will be possible beyond
this TAF period Tuesday afternoon.

&&

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

&&

$$

DISCUSSION...Cecava
AVIATION...EMS