105
FXUS63 KARX 240923
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
423 AM CDT Mon Jun 24 2024

.KEY MESSAGES...

- Showers and thunderstorms return to the forecast tonight.
  However, there still remains quite a bit of uncertainty
  revolving around storm evolution. A Slight Risk (level 2 of 5)
  for severe weather remains across the area. Should everything
  come together and severe storms develop, a more widespread
  damaging wind risk may evolve.

- Another brief break for mid-week before additional shower and
  storm chances return late in the period. Details to be refined
  in the coming days.

&&

.DISCUSSION...
Issued at 423 AM CDT Mon Jun 24 2024

Today - Tuesday:

Bottom line up front... the environment is very favorable for severe
storms tonight. However, there still remain some considerable
questions on storm evolution (where, when, and even if).

An upper level low will continue to move eastward across Canada
today, with a surface low and attendant frontal boundaries
advancing across portions of the region. Moisture will be on the
increase into the area with surface dewpoint temperatures
forecast to increase into the 60s to low 70s. Strong warm air
advection will also be increasing from the southwest through the
day. This along with steep mid level lapse rates will allow for
strong instability to build in. However, strong capping is
expected to be in place with the EML moving into the region.

The latest hi-res model guidance continues to show various solutions
on how storms may evolve. It is possible we could see some elevated
showers develop early this evening with mid level saturation shown
in forecast model soundings. However, an interesting signal to
mention, that has been persistent in a few of the hi-res models, is
for storms to develop and track across Interstate 90. With not much
focus for lift and the strong capping in place, this seems to be the
less likely scenario at this time (but not throwing it out as
impossible). Highest attention turns a bit later where a more
significant scenario may be possible where hi-res guidance shows
storms developing and intensifying into an MCS. With this solution,
storms would likely track around the capping in place/along the CAPE
gradient. While there are varying solutions on the track and timing,
ensemble consensus seems to favor tracking the complex
southeast along the Interstate 94 corridor. Though there is
some signal for the southern edge of the system to brush south
towards Interstate 90. If this scenario does occur, a more
widespread swath of damaging winds would be possible. Overall,
will need to continue to monitor trends and guidance through the
day. There is quite strong instability and shear to work with,
so IF storms can develop tonight they are very likely to become
severe.

As we head into Tuesday confidence unfortunately does not increase
much more. A cold front is forecast to drop down across the area
with some model guidance suggesting further storm development.
However, how storms evolve on Tuesday will likely depend on tonights
storms. Especially as there has been some indication for the cold
front to be forced further south quicker. SPC has maintained its
Slight Risk (level 2 of 5) for southern portions of the local area
for now with the given uncertainties and multiple possible
scenarios.

Mid-week onward:

High pressure builds in across the region behind our early week
system. This looks to offer another break in shower and thunderstorm
chances, with a bit cooler temperatures for mid week. However,
another low pressure system is forecast to move across the region
towards the end of the week. This brings a return of showers and
thunderstorms to the area. However, there still remains typical
spread in ensemble guidance regarding overall details. Will hang
with the latest blended model guidance for now, which increases
chances Thursday night into Friday evening/night.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1057 PM CDT Sun Jun 23 2024

VFR conditions are forecast for Monday. However, during the
evening hours, thunderstorms could develop over central MN and
move southeast toward the airfields. There is very warm air
above the surface which should favor thunderstorms to form
further north and east - toward KMSP to KDLL and northeast
generally. Wind shear profiles combined with the instability,
should it be released, would form severe thunderstorms with
large hail and mainly a damaging wind threat.

For now, have decided to add VCSH and a VFR BKN cloud deck for
Monday evening until confidence can grow in a given outcome.

&&

.HYDROLOGY...
Issued at 613 AM CDT Sun Jun 23 2024

Heavy rainfall over the previous couple of days has resulted in many
area rivers and streams running high or in flood stage. Flooding
concerns will last well into the week, with the Mississippi
River also continuing to rise. Fortunately, little rainfall is
expected into Monday. However, another round of showers and
thunderstorms will be possible Monday night into Tuesday.
Although some details are uncertain at this time, will need to
monitor for any further potential hydro impacts with these
storms. Please continue to reference the latest flood
statements for additional updates and details.

&&

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

&&

$$

DISCUSSION...EMS
AVIATION...Baumgardt
HYDROLOGY...EMS