995
FXUS63 KMKX 230921
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
421 AM CDT Thu May 23 2024

.KEY MESSAGES...

- Two rounds of showers and thunderstorms will likely occur
  Friday morning and late Friday afternoon. Gusty winds are the
  main threat.

&&

.SHORT TERM...
Issued 419 AM CDT Thu May 23 2024

Today through Friday:

Friday is a complex weather day. A line of storms is expected
to develop over eastern SD/NE tonight, which would be associated
with a midlevel shortwave trough and a coincident warm front on
the nose of a nocturnal low level jet. The parent mid level
closed low will be over the western Dakotas during this time, so
the system will be occluding. The line of storms should be just
east of Des Moines at 12Z/7 AM Friday morning, with the
northward extent near the Twin Cities and the southward extent
possibly down to Kansas City, per the meso models.

The line may hold together as it tracks across southern WI
Friday morning, but it should be weakening as it gets farther
away from that parent upper low. Models have that exiting or
dissipating midday, so we can call that the morning round. This
morning round has the potential to bring gusty winds west of
Madison if it manages to remain organized. If it falls apart due
to the lack of upper forcing and the weakening low level jet,
then there may be a stalled boundary lingering over south
central WI.

The next mid level shortwave will arrive in south central WI
mid afternoon, along with a surface cold front. Around the same
time, a weak shortwave will be rolling across MO and southern
IL. With high instability there, a storm complex with broken
lines of storms is anticipated to develop and have upscale
growth where it zippers northward just ahead of the cold front
and phases with that WI shortwave. As long as that morning
round didn`t work over the environment in southern WI too much,
we should have thunderstorms develop along this shortwave, area
of surface convergence, and nose of the low level jet.

Dewpoints should creep into the lower 60s near the WI/IL border
ahead of this front, so CAPE is forecast to be 1000 to 1500
j/kg in southern WI. The 0-3km shear is very high (35-40 kt) due
to southeast winds at the surface and SSW winds with the low
level jet. These ingredients are favorable for qlcs tornado
development with any line of storms moving ENE. However, the
main severe threat with these anticipated storms with the
afternoon round is wind damage. Timing of these storms across
southern WI looks like roughly 3 to 8 PM, but the forecast
timing between the models is all over the place.

Temperatures Friday are uncertain due to the uncertainty of the
thunderstorm coverage, but highs should be in the mid to upper
70s.

Cronce

&&

.LONG TERM...
Issued 419 AM CDT Thu May 23 2024

Friday Night through Wednesday:

The actual cold front will probably lag behind the convective
line Friday night and feature a wind shift to the northwest.
Cooler temperatures are expected on Saturday of Memorial Day
weekend with highs in the lower 70s. Sunshine will prevail with
high pressure and light winds overhead.

The next system of interest will arrive Sunday morning with a
mid level shortwave trough and surface low tracking through MO,
IL and WI. Right now it looks like the mid level lapse rates
will be weak, so not a lot of instability to work with to
develop stronger storms. The next shortwave trough looks more
robust and is expected to swing across IL Monday night or
Tuesday morning. These shortwaves are rotating around a closed
low that will be sitting over the Upper Great Lakes or Quebec,
depending on which model you choose. Nevertheless, we can expect
rounds of showers with a few thunderstorms Sunday through
Tuesday.

We will transition to a zonal pattern by the end of the week
which should give us a break in the storm complexes.

Cronce

&&

.AVIATION...
Issued 419 AM CDT Thu May 23 2024

A weak shortwave tracking from IA to southern WI this morning
through early afternoon is expected to provide steep mid level
lapse rates again today. The better chance of pop-up
thunderstorms is west of Madison again. Bases will be VFR around
7000 ft outside of any convection.

Cronce

&&

.MARINE...
Issued 419 AM CDT Thu May 23 2024

High pressure will drift across the Great Lakes today. Light to
modest westerly winds will prevail over the entire lake. Winds
will become east-southeast on Friday as a low pressure trough
approaches from Wisconsin. Thunderstorms are likely along this
trough Friday afternoon and night. Winds will shift to the west
in the wake of the trough Saturday morning and high pressure
will overspread the Lake Michigan. Low pressure will slide
across the Midwest Sunday and across Lower Michigan Monday.

Cronce

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

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