Special Weather Statement, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
247 PM CDT Thu Aug 1 2024

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Thunderstorms are possible into tonight. A few storms may
   become strong to severe into the evening. However, heavy
   rainfall and localized flooding will be the main concern as
   storms will be slow moving.

 - Above normal temperatures continue through Saturday. A cold
   front will then move through the area Saturday night into
   Sunday morning, returning temperatures closer to normal early
   next week.

 - Storm chances will return at times from Saturday night through
   Tuesday. It is possible that a MCS moves across the southern
   half of Wisconsin Monday night into early Tuesday.

&&

.DISCUSSION...
Issued at 246 PM CDT Thu Aug 1 2024

Short Term...Tonight and Friday

An upper low and associated surface system will move across southern
Wisconsin into northern Illinois and northern Indiana tonight,
and produce slow moving lines of thunderstorms with flood potential,
and some discrete storms which could produce large hail and strong
winds. The flood threat is greatest across central and portions
of east central Wisconsin. The activity will end from northwest to
southeast overnight, with some clearing possible by daybreak.
Lows will 5 to 10 degrees above normal.

Drier air will arrive Friday as upper ridging arrives from the
northern Plains, and a weak surface high builds in. Temperatures
will actually be warmer Friday than today due to increased sunshine,
a northwest downslope wind and lower surface dewpoints. This will
add up to a pretty hot day, with heat indices in the middle 80s
to low 90s.

Long Term...Friday Night Through Thursday

Broad and strong H5 ridge over the southwest CONUS gradually will
be suppressed due to larger scale troughing developing from Hudson
Bay toward the Great Lakes and into eastern Canada. Eventually
this will bring cooler and less humid conditions to the western
Great Lakes late this weekend into much of next week. Though the
weekend starts off dry, this pattern will also bring a return to
unsettled weather with chances for showers and thunderstorms
Sunday through early next week. There will be some severe potential
and as has been a common theme this summer, there is a potential
for excessive rainfall at times.

For Friday night and Saturday, dry conditions as high pressure
prevails. Late in the day Saturday, a cold front will approach
from the northwest. This front will drift across the area into
Sunday. Greatest risk for severe Saturday night will be to the
west, but on Sunday with the front across the area and ample
shear over 35 kts, even weaker instability toward 1000/kg could be
sufficient to support at least an isolated severe potential during
peak heating. This front will be what finally beats the heat and
humidity back to the south and southwest. Highs on Saturday will
reach the upper 80s to near 90, but with mostly lower 60s dewpoints,
heat index values will mainly stay 90 or lower.

Questions arise Sunday night into Monday on how far south the
front will sink. There is decent agreement now from the Canadian,
GFS and ECMWF that there could be mainly dry conditions to the
area later Sunday night into Monday. Not a lot of change in models
showing potential MCS over parts of WI on Monday night. This will
be occurring within strong belt of westerlies on the northeast
edge of higher MUCAPE. Effective shear over 40 kts more than
sufficient for severe. Main question is where will the MCS track.
ECMWF and Canadian favor southern half of WI whereas the GFS still
is farther north and would impact most of the GRB forecast area.

Dry, cooler and less humid conditions settle in behind the system
for Tuesday. It remains cooler Wednesday and Thursday, but at
least small chances of rain will also return, especially later
Wednesday into Thursday.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1250 PM CDT Thu Aug 1 2024

An upper level disturbance will move across Wisconsin today and
bring scattered showers and thunderstorms this afternoon and
evening. VFR ceilings are expected outside of any convective
activity. Some clearing is possible late tonight, with mostly
clear skies and good flying weather Thursday.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

DISCUSSION.....RDM/JLA
AVIATION.......RDM

Hazardous Weather Outlook
National Weather Service Green Bay WI
246 PM CDT Thu Aug 1 2024

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-022000-
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-
246 PM CDT Thu Aug 1 2024

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

.DAY ONE...Tonight

Slow moving thunderstorms could produce localized flooding through
the evening hours, especially south of highway 29. A few strong to
severe storms are possible as well, with large hail and strong winds.

.DAYS TWO THROUGH SEVEN...Friday through Thursday

There is a chance of thunderstorms at times Saturday night through
Tuesday. Stronger storms may be possible Monday night into Tuesday
morning.

.SPOTTER INFORMATION STATEMENT...

Spotters are requested to report any hail, damaging winds or flooding
to the National Weather Service in Green Bay.

LMZ521-522-541>543-022000-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
246 PM CDT Thu Aug 1 2024

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

.DAY ONE...Tonight

Thunderstorms are possible this evening. A few of the storms
could contain gusty winds and hail.

.DAYS TWO THROUGH SEVEN...Friday through Thursday

Periodic storm chances then return Sunday through Tuesday. Any
storms during this time may pose a threat to mariners.

RDM/JLA

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Special Weather Statement
National Weather Service Green Bay WI
610 PM CDT Thu Aug 1 2024

WIZ045-048-020000-
Winnebago WI-Waushara WI-
610 PM CDT Thu Aug 1 2024

...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN WINNEBAGO AND
SOUTHEASTERN WAUSHARA COUNTIES THROUGH 700 PM CDT...

At 609 PM CDT, Doppler radar was tracking a strong thunderstorm near
Berlin, moving northeast at 10 mph.

HAZARD...Wind gusts up to 40 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Oshkosh, Rush Lake, Omro, Winneconne, Eureka, Pickett, Butte Des
Morts, Highland Shore, Lake Butte Des Morts, and Rivermoor.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Conditions are favorable for the development of weak, brief funnel
clouds. This type of funnel cloud is harmless, but on rare occasions
they can briefly touch down, producing wind gusts over 40 mph. If a
funnel cloud is spotted move indoors and report your sighting to the
National Weather Service.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4398 8889 4398 8897 4401 8900 4415 8900
      4415 8875 4411 8859 4403 8858 4390 8858
      4389 8862 4390 8889
TIME...MOT...LOC 2309Z 220DEG 7KT 4398 8889

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH

GK

Special Weather Statement
National Weather Service Green Bay WI
613 PM CDT Thu Aug 1 2024

WIZ018-030-020000-
Marathon WI-Lincoln WI-
613 PM CDT Thu Aug 1 2024

...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN LINCOLN AND
NORTHWESTERN MARATHON COUNTIES THROUGH 700 PM CDT...

At 613 PM CDT, Doppler radar was tracking a strong thunderstorm 13
miles south of New Wood Wildlife Area, or 16 miles east of Medford,
moving southwest at 25 mph.

HAZARD...Wind gusts up to 40 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Abbotsford, Colby, Athens, Hamburg, and Milan.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Conditions are favorable for the development of weak, brief funnel
clouds. This type of funnel cloud is harmless, but on rare occasions
they can briefly touch down, producing wind gusts over 40 mph. If a
funnel cloud is spotted move indoors and report your sighting to the
National Weather Service.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4503 9031 4504 9020 4512 9020 4512 9005
      4523 9004 4517 8981 4503 8985 4495 9008
      4488 9032
TIME...MOT...LOC 2313Z 055DEG 21KT 4511 9001

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...40 MPH

GK