419
FXUS63 KMKX 231805
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
105 PM CDT Thu May 23 2024

.KEY MESSAGES...

- Two rounds of showers and thunderstorms will likely occur from
  Friday morning into Friday evening. There is a potential for
  severe thunderstorms with the 2nd round of storms.

&&

.UPDATE...
Issued 104 PM CDT Thu May 23 2024

Broken high based cumulus has formed as a weak shortwave trough
moves across central and srn WI this afternoon. There is also
very weak low to mid level warm advection occurring around the
high. Fcst soundings and CAMs suggest central WI is the
preferred area for isold to sct showers and isold storm
development this afternoon, with some lgt showers already
developing over said area. Increased PoPs to 30-40 percent
toward central WI through the afternoon. Otherwise high temps in
the middle to upper 70s looks good for today while a lake
breeze at the lake front will move inland later this afternoon.
Upper ridging and a quiet night is then expected.

For Fri, a negative tilt upper wave and associated sfc low will
move from the ern Dakotas into Canada while deepening then
occluding. A surge of low to mid level warm, moist advection and
elevated CAPE will bring a 1st round of showers and storms from
west to east across srn WI Fri AM into the early afternoon,
with some weakening expected in the east, especially toward east
central WI. A few hours or more of decreasing pcpn coverage and
the nwd advance of the warm front is then expected over srn WI
before the cold front arrives from late afternoon into the
evening. There is uncertainty on the airmass recovery and the
amount of MLCAPE and MLCIN within the narrow warm sector, but
believe MLCAPE of 1000 J/KG is very probable while some MLCIN
will remain. However some PVA should aid the frontal forcing
and most CAMs and models do suggest another round of storms.

Deep layer shear will range from 30-45 kts while 0-2km SRH will
likely be rather high around 200-300 m2/s2 as veering profiles
remain in the narrow warm sector. As the fronts advance the lake
breeze should eventually retreat toward the lake but early
afternoon convection could reinforce it as well. All SVR threats
will be possible with supercellular development and/or QLCS
development. If the airmass recovery suffers, any meaningful
MLCIN would keep the tornado threat rather small.

Nwly winds and cold advection will then drop temps into the
middle 40s to lower 50s by sunrise Sat. High pressure will then
shift across the state on Sat with temps rebounding into the
lower 70s for the afternoon.


Gehring

&&

.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 104 PM CDT Thu May 23 2024

Sct-bkn050-070 cumulus this afternoon with scattered showers and
isold storm development toward central WI. The precipitation
will end by early evening with a quiet night and VFR conditions
expected. Showers and storms will then move west to east across
srn WI during the morning daylight hours of Fri. There will be a
break of a few hours or so followed by more showers and storms
late afternoon and early evening. Areas of MVFR Cigs will be
possible over south central WI throughout the day and may spread
into ern WI for the evening.

Gehring

&&

.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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