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195
FXUS63 KMKX 202104
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
404 PM CDT Mon May 20 2024

.KEY MESSAGES...

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- This afternoon`s strong to severe thunderstorm threat has
  ended.

- A complex severe weather event is expected for Tuesday, with
  multiple rounds of thunderstorms expected. The greatest severe
  weather threat continues to be Tuesday evening.

- All severe weather hazards will be possible Tuesday evening,
  including strong winds, large to very large hail, and
  tornadoes.
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&&

.UPDATE...
-- Changed Discussion --
Issued 359 PM CDT Mon May 20 2024

This afternoon`s strong to severe potential has ended across the
region. The area of most favorable forcing tied to an MCV has
shifted east across Lake Michigan, with subsidence beginning to
prevail across southern Wisconsin. Severe Thunderstorm Watch 267
has thus been cancelled. Apart from a few light rain showers,
quiet weather is anticipated through the first half of this
evening.

Quigley
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&&

.SHORT TERM...
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Issued 248 PM CDT Mon May 20 2024

Rest of this Afternoon through Tuesday night:

Convection is ongoing across the region this afternoon,
associated with a convectively enhanced shortwave/MCV working
through the area. Strong southerly flow associated with this
feature has helped bring a warm front north into extreme southeastern
Wisconsin, with reinforcing east to northeast flow along and
north of the track of the MCV. Convection will continue to
develop and push east through early evening, with occasional
strong/severe storms producing large hail and gusty winds.

The evening hours tonight should be fairly quiet, with the
region within an area of subsidence behind the departing MCV. A
weak pressure gradient combined with the moist airmass will pose
a fog threat overnight, especially over the eastern half of the
area. Some areas of dense fog will be possible.

The nose of a low level jet then begins to push into the area
from the west and southwest late tonight/early Tuesday. An
initial area of elevated thunderstorms will likely push into
the area during the predawn hours. Locations north and west of
Madison will have the greatest chance of seeing convection, with
considerable uncertainty as to how far east this activity makes
it before pushing north.

By late morning, a warm front will lift into the region as low
pressure deepens across Minnesota. Despite the convection
along/north of the warm front, very deep and strong southerly
flow will favor a more progressive northward movement to the
front. This should put nearly all of the CWA solidly within the
warm sector by mid afternoon. From that point forward, things
will really depend on where exactly convection fires east of the
cold front in Iowa. There could be one round as early as mid
afternoon, if storms develop along a prefrontal trough just west
of the Mississippi River, but this is uncertain. The front will
eventually surge eastward during the evening, clearing the area
around midnight. Storms are very likely along the front as it
moves east.

While the outcome will ultimately depend on "game day" mesoscale
details, this is a very dynamic system with a very favorable
airmass ahead of it. Some combination of supercells and QLCS(s)
are probable. Very steep mid level lapse rates and appreciable
low and mid level shear will pose a threat for tornadoes and
very large hail with any supercells. If/when cold pools begin to
congeal, one or more strong QLCSs could develop, with an
attendant wind and QLCS tornado threat.

Boxell
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&&

.LONG TERM...
Issued 248 PM CDT Mon May 20 2024

Wednesday through Monday:

The low pressure associated with Tuesday`s thunderstorms will
continue propagating northward into Canada on Wednesday, with
gusty west winds, cold air advection, and decreasing cloud
coverage across southern Wisconsin in response. Upper level
ridging and high pressure will build into the Midwest Wednesday
afternoon into Thursday allowing for drier weather through Friday
morning.

A shortwave trough and associated surface low pressure system
will approach Wisconsin on Friday, leading to the next chance for
showers and thunderstorms Friday afternoon through Saturday
morning. The GFS and Euro look to be in better agreement regarding
timing of this system, but the GFS continues to be a little more
rambunctious regarding shower/thunderstorm development and QPF
Saturday morning, especially near the Wisconsin/Illinois border.

Another shortwave looks to move across the state during the day on
Saturday which will help support chances for showers and
thunderstorms. Weak ridging moves into the region on Sunday and
Monday leading to lower precipitation chances before another upper
trough propagates towards the region Monday afternoon.

Falkinham

&&

.AVIATION...
Issued 248 PM CDT Mon May 20 2024

Showers and thunderstorms will continue to push east of the area
this afternoon. A combination of MVFR and VFR ceilings are
expected this afternoon, with ceilings lifting to VFR by this
evening. Later tonight, light winds and ample low level moisture
will favor fog, and at times some low stratus. IFR is likely
with any fog or stratus overnight.

A warm front will lift northward through the region tomorrow,
turning winds southerly as the front moves through. A few rounds
of thunderstorms are possible, with the first occuring in the
morning hours, with one or two more in the late afternoon and
evening. Strong/severe storms are increasingly likely with the
afternoon and evening hours.

Boxell

&&

.MARINE...
Issued 248 PM CDT Mon May 20 2024

Southeast winds will turn southwesterly for a time late this
afternoon over the southern third of the lake, as a compact area
of low pressure moves through the area. Winds then turn
westerly tonight.

Winds will turn more south to southeasterly again Tuesday. Breezy
southerly winds are expected as a deepening low pressure approaches
the Upper Great Lakes Region and tracks northeast into
Wednesday. There looks to be periods of thunderstorms over the
lake, especially southern portions Monday through Wednesday
morning. Small Craft conditions are likely Tuesday afternoon
and night.

Boxell

&&

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

$$

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