Tornadoes and Flash Flood in Wisconsin, July 28, 2023

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
356 AM CDT Fri Jul 28 2023

.SHORT TERM...
(Issued 353 AM CDT Fri Jul 28 2023)

Today and Tonight:

Main Points for today:
 - Another hot and muggy day with higher heat indices nearing and
   exceeding 100F.
 - Potential for a line of strong to severe storms later this
   afternoon and evening with strong to damaging winds possible.

Scattered showers and a few thunderstorms from overnight activity
continue to linger across the area. CAMs seem to struggle in
handling this line of storms with only the 00z NSSL taking the line
all the way through south ern WI and into IL, where the strongest
storms exist this morning. Given the 00z NSSL performance, will
lean a bit more on its trend for development later today.

Expecting this lingering activity to gradually diminish through
daybreak as the mid-level shortwave trough pushes east. Already
seeing the environment recover a bit north of the morning showers
with southerly flow and a bump in the dewpoint closer to the
surface boundary extending across the Upper Midwest/northern WI.
Most CAMs show return flow and moisture advection to increase
through the morning as the surface front gradually slides south
with dewpoints climbing back into the lower 70s. Also expecting
deep/fat CAPE profiles to develop over the area through the day
with HREF probabilities of SBCAPE exceeding 1000 J/kg and 2000
J/kg on the higher end (>70 percent). Pair with deep layer shear
exceeding 40 kt and steep mid-level lapse rates of 7 C/km and the
ingredients will be present for strong to sever thunderstorms
later today.

Although there continues to be some minor disagreement between the
latest models on handling convection today, there is a consensus
to see a MCS develop along/near the surface front and roll across
southern WI. The question is where will it develop and timing as
models differ on the frontal placement with some solutions such as
the 00-06z HRRR firing things further north across central WI,
while other solutions such as NSSL and NAM 3km are slightly
further south along I-94 corridor. Nonetheless, there is
increasing potential for southern WI to see the a line of strong
to severe storms this afternoon. Could see some larger hail early
on as storms develop, but the main concern will definitely be
stronger to damaging winds. There are hints of 0-1km SRH exceeding
100 m2/s2 , thus still cannot rule out a tornado of two embedded
within the line, but chances remain on the lower side.

Lastly with any of the shower and thunderstorm activity along the
boundary, there is a potential to see some training resulting some
flooding concerns, but the precedent dry conditions may help limit
the impacts. However, flash flooding is possible with any heavier
rain rate over the same area.

Otherwise expecting another hot and muggy day as the morning
activity clears up. Looking at heat indices to climb through the day
and top off at or above 100F for southwestern areas away from the
lake, but areas closer to the lake will still be unpleasantly hot
with heat indices in the 90s.

Wagner

&&

.LONG TERM...
(Issued 353 AM CDT Fri Jul 28 2023)

Saturday through Monday:

High pressure builds southeast into the Great Lakes this weekend
into early next week, bringing some a cooler, more seasonable air
mass down from Canada. So we will see a break from the heat with
highs temperatures back down in the low/mid 80s. Closer to Lake
Michigan, northeast to north winds will help keep temperatures
locally cooler into early next week. There is a weak shortwave that
digs southeast across the Upper Great Lakes over the weekend, but
most this activity is expected to remain north of our area.

Tuesday through Thursday:

We will see a warming trend as high pressure moves east of the
region and upper-level ridging attempts to build back north.
Conditions look to remain dry through mid-week, with better chances
for showers and thunderstorms towards Wednesday night/Thursday as a
stronger shortwave digs south across the Great Lakes region.

Anderson

&&

.AVIATION...
(Issued 353 AM CDT Fri Jul 28 2023)

Showers and storms this morning will wrap up and VFR conditions are
expected through the morning with mainly southerly winds. Expect hot
and muggy conditions to give way to showers and thunderstorms later
this afternoon and evening. Expecting a line of storms to develop
along and ahead of the front and push through this evening. Strong
to severe storms with damaging winds will be the main concern.
This activity will bring lower flight conditions to area
terminals, but conditions are expected to improve into Saturday
morning as the line of showers and storms moves out.

Wagner

&&

.MARINE...
(Issued 353 AM CDT Fri Jul 28 2023)

A few rounds of thunderstorms are possible through Friday night,
which could be strong to severe, as a cold front slowly sags south
across the region. Winds become easterly today as the front slowly
moves into the area, then northeast tonight through Saturday and
northerly Saturday night. As winds take on more of a northerly
component, expect winds to increase slightly to perhaps around 20
knots. This will allow waves to build across the southern half of
the lake Saturday/Saturday night, but waves look to remain below
small craft advisory for now.

High pressure then builds into the region late this weekend into the
middle parts of next week, helping keep winds around or below 15
knots.

Anderson

&&

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

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Hazardous Weather Outlook
National Weather Service Milwaukee/Sullivan WI
335 AM CDT Fri Jul 28 2023

WIZ046-047-051-052-056>060-062>072-290845-
Marquette-Green Lake-Fond du Lac-Sheboygan-Sauk-Columbia-Dodge-
Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee-
Lafayette-Green-Rock-Walworth-Racine-Kenosha-
335 AM CDT Fri Jul 28 2023

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

.DAY ONE...Today and Tonight

A heat advisory is in effect for areas southwest of a line from
Wisconsin Dells to lake Geneva. Heat indices are expected to reach
100 to 105 degrees this afternoon.

A slight chance for showers and thunderstorms lingering this
morning. Stronger thunderstorms are expected to develop north and
west of the region or perhaps directly over the region this
afternoon, then drift ESE-ward across the region through tonight.
Gusty winds and hail are the main severe weather threat.

A moderate swim risk is expected for the lake front overnight
tonight.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

A moderate swim risk is forecast for the lake front throughout
Saturday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed, especially this afternoon and
evening.

LMZ643>646-290845-
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-
335 AM CDT Fri Jul 28 2023

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

.DAY ONE...Today and Tonight

A slight chance for showers and thunderstorms lingering this
morning. Stronger thunderstorms are expected to develop north and
west of the region or perhaps directly over the region this
afternoon, then drift ESE-ward across the region through tonight.
Gusty winds and hail are the main severe weather threat.

A moderate swim risk is expected for the lake front overnight
tonight.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

A moderate swim risk is forecast for the lake front throughout
Saturday.

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-290845-
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-
335 AM CDT Fri Jul 28 2023

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

.DAY ONE...Today and Tonight

A slight chance for showers and thunderstorms lingering over the
lake this morning. Stronger thunderstorms are expected to develop
west of the lake this afternoon, then drift ESE-ward across the
southern 2/3 of the lake this afternoon through tonight. Gusty
winds and hail are the main severe weather threat.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

No hazardous weather is expected at this time.

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