Hail and Heavy Rain in Wisconsin, May 23, 2020

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
435 PM CDT Sat May 23 2020

.SHORT TERM...

Late This Afternoon And Evening...Forecast Confidence Is Medium.

At 3 PM CDT, wind directions across southern WI remain mainly
easterly, quickly veering to a more predominate southeasterly
direction is just south of the WI/IL state line. The greatest low
level wind veering and helicity is coincident with this
boundary/wind shift. This boundary will continue to move slowly
north this afternoon and this evening, as surface low pressure
just west of Dubuque, IA moves to the northeast. It should be in
the Lone Rock, WI vicinity by early this evening.

As always, there are some questions with how things evolve.
Effective deep layer shear is 30 to 40kt, which is good enough
for storm organization, though it drops off steadily the further
north you travel from the WI/IL state line. Low level (0-1km)
shear is decent at 20 to 25kt, but the directional shear is most
interesting, with both 0-1km and 0-3km SRH in the 200-250 m2/s2
range. Instability is modest, but supportive. A ridge of 500-1000
J/kg MLCAPE is nosing into southern WI, with SBCAPE around 1000
J/kg. Low level CAPE, however, is very good. The 18Z DVN sounding
measured ~120 J/kg of 0-3km CAPE, and short range models have had
a good beat on this axis of higher low level CAPE along the
surface boundary.

All told, supercellular structures are expected, though it will
not be surprising to see more messy multi-cellular behavior from
time to time. It should be noted that key features will be a bit
lower in the atmosphere. As a result, the further away from any
radar you go, you will be more likely to see the top of
rotational features (if any features at all in some cases).

The greatest risk for severe weather will be associated with this
boundary, as there has already been numerous reports of funnel
clouds and tornadoes to our southwest and south. Given good low
level shear and very good low level instability, tornadoes will be
a concern through early evening. There will be a risk for hail up
to 1 inch in diameter and localized wind gusts as well.

The risk for severe will drop steadily heading into the mid
evening hours, as peak heating subsides and convection exits to
the northeast.

Later Tonight Through Monday Night...Forecast Confidence Is
Medium.

Winds will shift west later tonight but remain light, as the
surface low exits the area. They will remain light into Sunday
morning. The light winds with the moist low levels may allow for
dense fog to form across the area. For now, kept this mention out
of the forecast, but will continue to monitor this potential.

Chances for showers and thunderstorms will continue Sunday into
Monday night across the area, as warm and humid conditions move
into the area. There is not much in the way of forcing mechanisms
for upward vertical motion to speak of during this period.
However, there will be decent mean layer CAPE and moisture to work
with, in case any storms do form. Some indications of a cap on
Sunday, which may limit storm development. Given the instability
and modest deep layer shear, outside chances for severe storms
during this period.

.LONG TERM...

Tuesday Through Saturday...Forecast Confidence Is Medium.

Chances for showers and storms will continue Tuesday into
Thursday, until the cold front finally pushes southeast through
the area. Again, no great forcing mechanisms until the front sags
through the area Thursday. Too early to tell if any stronger
storms may occur. Warm and humid conditions should continue
during this period. High pressure should then bring quieter
weather for the end of the week.

&&

.AVIATION(21Z TAF UPDATES)...

Main area of showers and thunderstorms should continue to move
east northeast through the area through the middle evening hours,
affecting the terminals in a 2 to 4 hour window as they move
through. Severe storms with large hail, damaging winds and a
tornado or two are possible during this time. May see ceilings and
visibility values drop to IFR in the strongest storms. Gusty east
winds late this afternoon should weaken this evening.

Winds will shift to the west and remain light later tonight, with
some fog development possible overnight into Sunday morning.
Dense fog is possible, but did not mention in TAFs yet due to
modest confidence. VFR conditions should return by middle to late
morning Sunday, lingering through the afternoon. Light south winds
are expected by the afternoon. Chances for showers and storms
will increase by Sunday night, but left out of TAFs for now due to
uncertainty.

&&

.MARINE...

Dense fog is expected to linger across the nearshore and open
waters of Lake Michigan through at least Sunday, and perhaps into
early next week, as a warm and humid airmass moves over the cool
lake waters. The fog may improve briefly, while the storms move
through into this evening. Thus, the Dense Fog Advisory has been
extended through Sunday for the nearshore and all of the open
waters of Lake Michigan.

Another low pressure system moving from the central Plains into
southwest Ontario will keep the shower and thunderstorm chances
going for the first half of next week. Winds and waves are
expected to remain on the low to moderate side into early next
week.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Dense Fog Advisory until 7 PM CDT Sunday for LMZ080-261-362-364-
     366-563-565-567-643>646-669-671-673-675-777-779-868-870-872-
     874-876-878.

&&

Late This Afternoon/Evening...Gagan
Later Tonight Through Saturday and Aviation/Marine...Wood

Hazardous Weather Outlook...UPDATED
National Weather Service Milwaukee/Sullivan WI
445 PM CDT Sat May 23 2020

WIZ046-047-051-052-056>060-062>072-242145-
Marquette-Green Lake-Fond du Lac-Sheboygan-Sauk-Columbia-Dodge-
Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee-
Lafayette-Green-Rock-Walworth-Racine-Kenosha-
445 PM CDT Sat May 23 2020

This Hazardous Weather Outlook is for portions of east central
Wisconsin, south central Wisconsin and southeast Wisconsin.

.DAY ONE...Late This Afternoon And Tonight

A Tornado Watch remains in effect along and south of a Lone Rock
to Madison to Milwaukee line until 8 PM CDT this evening.
Scattered thunderstorms will continue to move east northeast
through southern Wisconsin into this evening.

These storms may become severe, producing a few tornadoes, hail
to one inch and wind gusts to 60 MPH. The best chances for
tornadoes will be in areas southwest of Madison. Heavy rainfall
may accompany the thunderstorms.

Dense fog may develop later tonight.

.DAYS TWO THROUGH SEVEN...Sunday through Saturday

Dense fog may linger into Sunday morning.

The chances for thunderstorms continue off and on through the
Memorial Day weekend and for much of next week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will be needed into this evening.

LMZ643>646-242145-
Sheboygan to Port Washington WI-
Port Washington to North Point Light WI-
North Point Light to Wind Point WI-
Wind Point WI to Winthrop Harbor IL-
445 PM CDT Sat May 23 2020

This Hazardous Weather Outlook is for the nearshore waters
from Sheboygan Wisconsin to Winthrop Harbor Illinois.

.DAY ONE...Late This Afternoon And Tonight

Areas of dense fog are expected, due to humid air moving over the
cooler nearshore waters of Lake Michigan. A Dense Fog Advisory has
been extended tonight, for visibilities frequently reduced to 1
mile or less.

A Tornado Watch is in effect south of North Point Lighthouse
until 8 PM CDT this evening. Scattered thunderstorms are expected
to move east northeast into Lake Michigan late this afternoon and
evening. These storms may become severe, with a waterspout, hail
to one inch and wind gusts to 50 knots possible.

.DAYS TWO THROUGH SEVEN...Sunday through Saturday

Dense fog is expected into Sunday, with a Dense Fog Advisory now
in effect until 7 PM CDT Sunday evening for the nearshore waters.

Dense fog will be possible throughout the rest of the Memorial
Day weekend and into next week, as a humid airmass flows over the
relatively cold waters of Lake Michigan.

The chances for thunderstorms continue throughout the Memorial
Day weekend into next week.

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-242145-
Lake Michigan Michigan City IN to St. Joseph MI 5 NM offshore to
mid-line of lake.-
Lake Michigan from Seul Choix Point to Rock Island Passage 5NM
offshore to Mid Lake-
Lake Michigan South of a line from Seul Choix Point to the
Mackinac Bridge and North of a line from Charlevoix MI to South
Fox Island 5NM offshore-
Lake Michigan from Charlevoix to Point Betsie MI 5NM Offshore to
mid lake-
Lake Michigan from Point Betsie to Manistee MI 5NM offshore to
Mid Lake-
Lake Michigan from Rock Island Passage to Sturgeon Bay WI 5NM
offshore to mid lake-
Lake Michigan from Sturgeon Bay to Two Rivers WI 5NM offshore to
Mid Lake-
Lake Michigan from Two Rivers to Sheboygan WI 5NM offshore to Mid
Lake-
Lake Michigan from Sheboygan to Port Washington WI 5NM offshore
to Mid Lake-
Lake Michigan from Port Washington to North Point Light WI 5NM
offshore to Mid Lake-
Lake Michigan from North Point Light to Wind Point WI 5NM
offshore to Mid Lake-
Lake Michigan from Wind Point WI to Winthrop Harbor IL 5NM
offshore to Mid Lake-
Lake Michigan from Winthrop Harbor to Wilmette Harbor IL 5NM
offshore to Mid Lake-
Lake Michigan from Wilmette Harbor to Michigan City in 5NM
offshore to Mid Lake-
Lake Michigan from Pentwater to Manistee MI 5NM offshore to Mid
Lake-
Lake Michigan from Whitehall to Pentwater MI 5NM offshore to Mid
Lake-
Lake Michigan from Grand Haven to Whitehall MI 5NM offshore to
Mid Lake-
Lake Michigan from Holland to Grand Haven MI 5NM offshore to Mid
Lake-
Lake Michigan from South Haven to Holland MI 5NM offshore to Mid
lake-
Lake Michigan from St Joseph to South Haven MI 5NM offshore to
Mid Lake-
445 PM CDT Sat May 23 2020

This Hazardous Weather Outlook is for the open waters of Lake
Michigan.

.DAY ONE...Late This Afternoon And Tonight

Areas of dense fog will continue to affect the open waters of
Lake Michigan, reducing the visibility to less than one mile. A
Dense Fog Advisory has been extended for all of the open waters
tonight.

Scattered thunderstorms are expected to move east northeast across
Lake Michigan late this afternoon and tonight. These storms may
become severe over the southern one quarter of the lake, with
large hail to one inch, wind gusts to 50 knots and a waterspout
possible.

.DAYS TWO THROUGH SEVEN...Sunday through Saturday

Dense fog is expected into Sunday, with a Dense Fog Advisory now
in effect until 7 PM CDT Sunday evening for all of the open waters.

Dense fog will be possible throughout the rest of the Memorial
Day weekend and into next week, as a humid airmass flows over the
relatively cold waters of Lake Michigan.

The chances for thunderstorms at times will continue throughout
the Memorial Day weekend into next week, with the best chances
over the southern half of Lake Michigan.

Wood
www.weather.gov/mkx