Special Weather Statement, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
621 AM CDT Tue Aug 25 2020

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 347 AM CDT Tue Aug 25 2020

Showers and thunderstorms will be ongoing across central and
east-central Wisconsin early this morning along a sagging cold
front. These storms could be strong to severe as MUCAPEs remain
around 1000 J/kg with bulk shear values of 30 to 35 knots, mainly
south of highway 29. In addition to the severe threat, PWAT values
of 1.5 to 2 inches and training cells could lead to localized
flooding. This activity should dissipate later this morning as the
front continues to sag south.

Across the north low level moisture and clearing skies has led to
some fog, which is expected to affect the morning commute. The fog
should mix out later this morning after sunrise.

The cold front will linger across the region through the afternoon
hours, which could set off additional showers and thunderstorms.
Highs today will be a few degrees cooler behind the boundary,
mainly in the lower to middle 80s.

The front will then lift back north as a warm front tonight, which
is expected to set off another round of showers and thunderstorms
as it surges north. This activity is expected to start out across
central and east-central Wisconsin this evening, then lift north
towards north-central Wisconsin later tonight into Wednesday
morning. These storms could be strong to severe with MUCAPE values
of 1000 to 1500 J/kg with 30 to 40 knots of bulk shear.

Lows tonight will be fairly warm, ranging from around 60 across
the north, with middle to upper 60s across the south. Dew points
in the middle to upper 60s could cause heat index values to rise
into the mid 90s across central and east-central Wisconsin
Wednesday afternoon.

Much of the showers and thunderstorm activity should lift north by
Wednesday afternoon as a capping inversion prevents activity on
the warm side of the warm front. However there will still be a
chance for showers and thunderstorms across north-central
Wisconsin closer to the frontal boundary. Temperatures on
Wednesday will once again be hot and humid as highs range from the
lower to middle 80s across the north, with highs around 90 or even
the lower 90s across central and east-central Wisconsin.

.LONG TERM...Wednesday Night Through Monday
Issued at 347 AM CDT Tue Aug 25 2020

Forecast concerns continue to revolve around the thunderstorm
potential through Friday.

Wednesday night through Thursday night...A cold front will be
sagging southeast across northern Wisconsin on Wednesday night. Most
thunderstorm activity will likely remain north of the region closer
to the better upper dynamics.  But will have a low chance of
showers/storms over northern WI where modest elevated instability
will be present.  Not out of the question that a few strong storms
could develop. The front will lay out across central WI on Thursday.
Convergence will be weak along the boundary, but could have a few
showers/storms pop with the heat of the day. Southwest flow
increases over the front on Thursday night ahead of a surface wave
moving east over the northern Mississippi Valley. Thunderstorms are
expected to become more widespread once again where deep layer shear
will be in excess of 40 kts.  Severe weather may be possible over
parts of central WI late Thursday night if parameters continue to
look the way they do.

Rest of the forecast...Widespread thunderstorms look to continue on
Friday as the surface wave moves across the region.  Heavy rainfall
appears possible over central and east-central WI just north of the
surface boundary.  Behind the system, the upper flow will turn to
the northwest and will bring a break in the hot/humid/stormy weather
for the weekend.  The next chance of rain will then occur early next
week.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 621 AM CDT Tue Aug 25 2020

A cold front will stall over central/southern WI today. Expect
isolated showers and thunderstorms across portions of central
Wisconsin during the early morning hours. VFR conditions will
exist where no precipitation occurs. However, vsbys could quickly
drop to MVFR/IFR under of the storms. Further north some LIFR/IFR
patchy dense fog should mix out in the next few hours as the sun
rises.

As long as the stalled front is in the vicinity, a few showers
and thunderstorms may develop throughout the day, however most of
the activity is expected in the afternoon hours. While VFR
conditions to be most prevalent, vsbys could drop into the MVFR
category under any precipitation. Additional chances of showers
and storms will linger into tonight as the front lifts northward
as a warm front, again, some of those storms could become strong
to severe very late tonight. Confidence in these storms hitting
the TAF sites is not high enough to include in this set of TAFs.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SHORT TERM.....Kurimski
LONG TERM......MPC
AVIATION.......Kurimski

Hazardous Weather Outlook
National Weather Service Green Bay WI
412 AM CDT Tue Aug 25 2020

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-260915-
Vilas-Oneida-Forest-Florence-Northern Marinette County-Lincoln-
Langlade-Menominee-Northern Oconto County-Door-Marathon-Shawano-
Wood-Portage-Waupaca-Outagamie-Brown-Kewaunee-Waushara-Winnebago-
Calumet-Manitowoc-Southern Marinette County-
Southern Oconto County-
412 AM CDT Tue Aug 25 2020

This Hazardous Weather Outlook is for north-central and northeast
Wisconsin.

.DAY ONE...Today and Tonight

There is a marginal risk of severe weather over mainly central
and east-central Wisconsin this morning and across north-central
Wisconsin later tonight. Hail, gusty winds and torrential
downpours will be possible.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Thunderstorms will be possible at times through Friday. Another
severe threat may occur over north-central and northeast Wisconsin
Wednesday afternoon and Wednesday night, and Thursday night into
Friday. Damaging winds, large hail, and heavy rainfall will be
the main threats.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed today and tonight. Spotters are
asked to report any hail, strong winds or rainfall over one inch.

LMZ521-522-541>543-260915-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
412 AM CDT Tue Aug 25 2020

This Hazardous Weather Outlook is for portions of northwest Lake
Michigan and the waters of Green Bay.

.DAY ONE...Today and Tonight

Isolated strong storms are possible this morning, mainly south of
Sturgeon Bay, and across the entire area tonight. Gusty winds and
hail are possible with the strongest storms.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Thunderstorms will be possible at times through Friday. Another
round of strong to severe storms will be possible Wednesday
afternoon into Wednesday night, especially north of Sturgeon Bay.
Thunderstorms are also likely on Thursday night into Friday. Any
storms that develop will pose a hazard to boaters.

Kurimski/MPC

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Special Weather Statement
National Weather Service Green Bay WI
517 AM CDT Tue Aug 25 2020

WIZ005-010>013-018-019-251330-
Vilas-Oneida-Forest-Florence-Northern Marinette County-Lincoln-
Langlade-
517 AM CDT Tue Aug 25 2020

...LOCALLY DENSE FOG EXPECTED THIS MORNING...

Clearing skies and abundant low level moisture has led to some
patchy fog across portions of north-central Wisconsin this
morning. The fog may become locally dense at times, reducing
visibility to one-quarter of a mile. The fog is expected to
quickly dissipate around sunrise.

Motorists traveling during the morning commute should be prepared
for sudden changes in visibility and be sure to allow extra time
to reach your destination.

Kurimski

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREEN BAY WI
741 AM CDT TUE AUG 25 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0705 AM     HEAVY RAIN       5 SE NEKOOSA            44.26N 89.81W
08/25/2020  M1.96 INCH       WOOD               WI   MESONET

            MESONET STATION NKAW3 NEW ROME 4 ENE.

0700 AM     HEAVY RAIN       4 SW NEKOOSA            44.26N 89.94W
08/25/2020  M1.81 INCH       WOOD               WI   COCORAHS

            COCORAHS STATION WI-WD-7 NEW ROME 3 WNW.

0729 AM     HEAVY RAIN       1 NNE OMRO              44.04N 88.74W
08/25/2020  M1.21 INCH       WINNEBAGO          WI   MESONET

            MESONET STATION OMROY OMRO 1 NNE.

0725 AM     HEAVY RAIN       OMRO                    44.03N 88.75W
08/25/2020  M0.93 INCH       WINNEBAGO          WI   MESONET

            MESONET STATION EW3427 OMRO.

&&

Special Weather Statement
National Weather Service Green Bay WI
913 AM CDT Tue Aug 25 2020

WIZ048>050-251515-
Calumet WI-Winnebago WI-Manitowoc WI-
913 AM CDT Tue Aug 25 2020

...STRONG THUNDERSTORMS MOVING THROUGH THE SOUTHERN FOX VALLEY...

At 912 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from Valders to 6 miles west of Chilton to 9 miles
west of Oshkosh. Movement was southeast at 50 mph.

Torrential rainfall will be possible with these storms.

Locations impacted include...
Appleton, Oshkosh, Menasha, Chilton, Brillion, Cleveland, Valders,
St. Nazianz, St Anna and Camp Rokilio Scout Camp.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is occurring with these storms, and may lead to
localized urban flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4409 8889 4412 8889 4425 8846 4424 8824
      4412 8790 4399 8763 4389 8770 4389 8816
      4394 8816 4394 8840 4389 8840 4389 8857
TIME...MOT...LOC 1412Z 307DEG 43KT 4407 8791 4404 8828 4406 8874

Kieckbusch