Special Weather Statement, NWS Milwaukee, WI

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
910 AM CDT Wed Jul 14 2021

.UPDATE...
(Issued 910 AM CDT Wed Jul 14 2021)

Strong warm air and moisture advection associated with low level
jet fueling line of severe convection across northern IA into
southern WI. As llj pivots east and north, this line should move
into southern and central Wisconsin in the early afternoon. The
area from Mineral Point to Fond du Lac has a bigger chance of
being affected by this line of storms, with less of a chance
farther to the southeast. Portions of southeast WI may remain dry
through the evening, especially toward the IL border.

Kavinsky

&&

.SHORT TERM...
(Issued 406 AM CDT Wed Jul 14 2021)

Today and Tonight:

With the potential for multiple rounds of thunderstorms and for
strong to severe storms it is best to be weather aware for this
afternoon into tonight.

The first round is currently over South Dakota and Nebraska
associated with 500mb wave, 850 low level jet, and 850mb warm air
advection feeding into it. You can also track this wave under the
250mb shortwave ridge which is providing some directional
divergence aloft. Current timing would place this area of
convection into western Wisconsin during the early afternoon. This
will continue to track eastward with the 850mb low level jet
feeding into it into the early evening. With the low level jet
expect an increase in wind shear and storm relative helicity.
We'll see CAPE values increase to around 2,000 J/kg with 0-6km
bulk shear around 30 knots. There is some uncertainty with how
far south this line of convection will extend and with corfidi
vectors oriented west to east, it doesn't look favorable for an
outflow boundary to push convection farther south. Areas along the
WI/IL border may miss out on round one...but if they don't
they'll be in the area of higher instability and storm relative
helicity increasing the potential for severe storms. The main
concern with this first round will be 60-70 mph winds with 1 inch
hail and the possibility for tornadoes as a secondary concern.

As the low level jet continues to build over the area into this
evening with southwest flow stacked up to 250mb shear values look
to increase to around 40 knots. As long as we clear out after the
first wave and we are able to recover instability wise, there is
another round of convection expected to develop along a surface
boundary stretching from northeast Wisconsin down into Iowa. This
will be another focus for severe thunderstorms. Initially anything
isolated will have a concern for strong winds, large hail, and a
tornado potential with the increase in storm relative helicity and
the boundary. Storms are then expected to congeal into a line and
shift southeast through the night. With the stacked southwest
flow and a slow moving southwest to northeast boundary there is a
concern for training storms to cause flooding. Precipitable water
values will be close to 2 inches, which is in record territory
with Green Bay's sounding record for the date at 1.89" and
Davenports at 2.02". Dry soils also won't absorb water as fast so
there is an increased runoff potential. We'll be monitoring the
forecast closely this morning and if confidence increases, Flood
Watches could be issued later today.

RAH

&&

.LONG TERM...
(Issued 406 AM CDT Wed Jul 14 2021)

Thursday through Tuesday:

Thursday, the main frontal boundary will slowly sag south across
southern Wisconsin, bringing additional chances for showers and
thunderstorms throughout the day. Any outflow boundaries that
push well south of our area from overnight convection will likely be
the main focus for more widespread activity down in Illinois during
the day. However, with the right entrance region of the upper-level
jet impacting much of the area throughout the day, this should
supply enough large-scale lift to foster additional development
along the main frontal boundary as it drops south throughout the
day. PWATs will remain high, around 1.75 inches or so ahead of
and along the frontal boundary, so heavy rain will occur with any
thunderstorm activity. As for the potential for severe weather, we
will likely see extensive cloud cover and an overall lack of strong
daytime heating, so it appears we may struggle to see any surface
based instability develop. With poor lapse rates aloft, there
doesn't appear to be much MUCAPE to work with either.

Thursday night into Friday morning, high pressure begins to build
south across the Upper Mississippi Valley and the slow moving
frontal boundary continue to move south into Illinois. This will
allow for a drying trend for much of southern Wisconsin. During the
day on Friday, the main upper-level trough moves across the region
and allows for a weak surface low to develop along the northern edge
of the frontal boundary. It does look like the majority of
precipitation and the heavy rain threat will be south of our area,
mostly down in Illinois again. Thus, do have a mostly dry forecast
for Friday.

This weekend into early next week looks to remain dry and quiet
weather wise, as large-scale subsidence dominates with high
pressure anchored across the region. Temperatures will gradually
modify back up into the mid to upper 80s during this stretch.

Anderson

&&

.AVIATION...
(Issued 910 AM CDT Wed Jul 14 2021)

Several rounds of thunderstorms are still expected to affect
southern Wisconsin this afternoon and tonight. Some of the storms
could be severe, producing strong winds and large hail. Aviation
personnel will need to keep a close on radar and the latest
conditions for your airport. Ceilings and vsbys in and near any
storms could drop to MVFR/IFR.

Kavinsky

&&

.MARINE...
(Issued 406 AM CDT Wed Jul 14 2021)

Southerly winds build into Thursday as a low pressure axis sets up
over the area. This will also bring periods of rain and
thunderstorms this evening into Thursday with the potential for a
few strong to severe storms. Gusts around 25 knots will briefly be
possible late tonight over the nearshore with gusts around 30
knots over the open waters. Winds become more northerly Thursday
night into Friday as high pressure builds over the Great Lakes
Region this weekend.

RAH

&&

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

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Hazardous Weather Outlook
National Weather Service Milwaukee/Sullivan WI
428 AM CDT Wed Jul 14 2021

WIZ046-047-051-052-056>060-062>072-150930-
Marquette-Green Lake-Fond du Lac-Sheboygan-Sauk-Columbia-Dodge-
Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee-
Lafayette-Green-Rock-Walworth-Racine-Kenosha-
428 AM CDT Wed Jul 14 2021

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

.DAY ONE...Today and Tonight

Two rounds of thunderstorms are expected this afternoon and
tonight, but the second round will depend on how fast the first
round clears out. Severe storms will be possible with strong
winds, large hail, and tornadoes possible. Training storms tonight
may cause flooding.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Rain and thunderstorms linger through Thursday evening.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will be needed this afternoon and tonight.

LMZ643>646-150930-
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-
428 AM CDT Wed Jul 14 2021

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

.DAY ONE...Today and Tonight

Two rounds of thunderstorms are expected early this evening and
late tonight, but the second round will depend on how fast the
first round clears out. Severe storms will be possible with strong
winds as the main concern and the potential for large hail.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Rain and thunderstorms linger through Thursday evening.

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-150930-
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-
428 AM CDT Wed Jul 14 2021

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

.DAY ONE...Today and Tonight

Two rounds of thunderstorms are expected early this evening and
late tonight, but the second round will depend on how fast the
first round clears out. Severe storms will be possible with strong
winds as the main concern and the potential for large hail.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Rain and thunderstorms linger through Thursday evening mainly over
the southern half of the lake.

www.weather.gov/mkx

Special Weather Statement
National Weather Service Milwaukee/Sullivan WI
1222 PM CDT Wed Jul 14 2021

WIZ056-062-067-141815-
Lafayette-Iowa-Sauk-

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT LAFAYETTE...IOWA AND
SAUK COUNTIES...

At 1222 PM CDT, radar indicated strong thunderstorms were located
along a line extending from near La Farge to near St. Donatus.
Movement was east at 40 mph.

Winds of 30 to 40 mph and pea size hail are possible with these
storms.

Locations impacted include...
Reedsburg, Dodgeville, Wisconsin Dells, Mineral Point, Darlington,
Lake Delton, Spring Green, Shullsburg, Belmont, Benton, Argyle,
Blanchardville, Barneveld, Wiota, Highland, Arena, Plain, North
Freedom, Ridgeway and Avoca.

LAT...LON 4320 9043 4321 9029 4317 9019 4355 9019
      4356 9031 4364 9031 4364 8979 4324 8978
      4321 8984 4251 8984 4251 9042
TIME...MOT...LOC 1722Z 261DEG 33KT 4360 9054 4239 9059

CMILLER

Special Weather Statement
National Weather Service Milwaukee/Sullivan WI
120 PM CDT Wed Jul 14 2021

WIZ056-057-062-063-068-069-141915-
Green-Columbia-Rock-Iowa-Sauk-Dane-

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTHERN GREEN...
EASTERN IOWA...NORTHWESTERN ROCK...COLUMBIA...DANE AND EASTERN SAUK
COUNTIES...

At 120 PM CDT, radar indicated strong thunderstorms were located
along a line extending from near Wisconsin Dells to near
Blanchardville. Movement was east at 40 mph.

Winds of 40 to 50 mph and pea size hail are possible with these
storms.

Locations impacted include...
Madison, Sun Prairie, Fitchburg, Middleton, Stoughton, Waunakee,
Baraboo, Verona, Portage, Oregon, McFarland, Monona, Mount Horeb,
Windsor, Edgerton, Columbus, Prairie Du Sac, Marshall, Sauk City and
Wisconsin Dells.

LAT...LON 4281 8987 4364 8990 4364 8913 4363 8912
      4363 8901 4285 8901 4285 8891 4282 8891
TIME...MOT...LOC 1820Z 269DEG 34KT 4367 8981 4277 8981

CMILLER

Special Weather Statement
National Weather Service Milwaukee/Sullivan WI
153 PM CDT Wed Jul 14 2021

WIZ063-064-069-141945-
Rock-Jefferson-Dane-

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT ROCK...SOUTHEASTERN
DANE AND SOUTHWESTERN JEFFERSON COUNTIES...

At 153 PM CDT, radar indicated strong thunderstorms were located
along a line extending from near Oregon to near Evansville to
Brodhead. Movement was east at 45 mph.

Wind gusts up to 50 mph and pea size hail are possible with these
storms.

Locations impacted include...
Janesville, Beloit, Stoughton, Fort Atkinson, Oregon, South Beloit,
Milton, Edgerton, Evansville, Clinton, Cambridge, Orfordville,
Brooklyn, Footville, Lake Ripley, Lake Koshkonong, Fulton, Albion,
Newark and Magnolia.

LAT...LON 4250 8936 4285 8937 4286 8947 4291 8951
      4305 8895 4288 8878 4249 8878
TIME...MOT...LOC 1853Z 251DEG 38KT 4289 8945 4277 8938 4262 8941

CMILLER