Special Weather Statement, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
1245 PM CDT Tue Jul 6 2021

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 423 AM CDT Tue Jul 6 2021

A nearly stationary front stretched from roughly MSP to GRB at
09Z. A surface low is expected to move along the front today while
a surface high north of Lake Superior tries to push the front
southward along the lakeshore. Thunderstorms will move along the
front as it edges slowly south. Elevated instability across
northern Wisconsin could create a hail threat while the far south
could have enough sunshine to create surface based CAPE and storms
with strong winds and hail. Highs today will likely occur before
noon in most places.

An approaching upper trough is forecast to produce cyclogenesis
over southern Minnesota, with the system moving across Wisconsin
tonight. The ECMWF has a much deeper surface low and much stronger
low level warm advection. This results in higher QPF totals of 2
to 3 inches over 24 hours. HPC QPF forecaster thought that the
ECMWF might be overdone due to convective feedback. The other
models still have a decent surface low and a good overrunning
rainfall event of 1 to 2 inches. The medium and large rivers
should be able to take that much rainfall, but there could be
some flooding or small streams or urban areas with an heavy
convective rainfall.

The showers and thunderstorms will end from northwest to
southeast Wednesday as the surface low goes by and a surface high
builds in from the north. It will be much cooler and breezy as
well, with temperatures about 20 degrees below normal.

.LONG TERM...Wednesday Night Through Monday
Issued at 423 AM CDT Tue Jul 6 2021

Main focus is on changes to the forecast this weekend. Otherwise,
temps will be below normal through most of the weekend and return
to near normal early next week.

Wednesday night and Thursday...Continue to carry chance PoPs in
east- central WI through Wednesday night as departing low and
shortwave could linger a few showers or thunderstorms mainly
along and east of the Fox Valley. Dry and cool high pressure
builds in for Thursday with highs about 10 degrees below normal
in the upper 60s/low 70s.

Friday through Sunday...Medium range models have come into better
agreement this cycle and bring a surface low and mid-level
shortwave through the Northern Plains and then stalling out in the
corn belt region. This puts the strongest forcing southwest of the
forecast area. As a result, lowered PoPs from Friday through
Sunday, especially across northern WI. Also removed the mention of
thunder with no instability present. If this trend continues will
need to lower PoPs quite a bit more as the GFS, ECMWF, and CMC
all depict a mostly dry weekend with high pressure keeping the
surface low blocked to the south. Temperatures will still be a few
degrees below normal due the mid/upper trough in place. Highs are
forecast to reach the 70s with lows in the 50s.

Early next week...Models have varying solutions at this point,
with the general consensus showing the high moving east which
allows the low to move north/northeast towards the western or
central Great Lakes. Could see a few showers if/when this low
passes through the area. Stuck with blended model solution during
this time which features chance PoPs.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1239 PM CDT Tue Jul 6 2021

Low pressure moving along a nearly stationary front across
central Wisconsin will bring showers and thunderstorms to the
area from west to east this afternoon and tonight. Scattered
strong to severe thunderstorms are expected across central and
east central WI between 3 pm and 9 pm. Have added TEMPO groups for
the most likely periods of thunderstorms at all TAF sites, except
RHI, where little instability is expected. Ceilings and visibility
will fall to MVFR by late afternoon or early evening and to IFR
later this evening. Poor flight conditions will continue Wednesday
morning, though rain may taper off at RHI later in the morning,
allowing for improvement to MVFR.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement from 4 PM CDT this afternoon through
Wednesday morning for WIZ040-050.
&&

SHORT TERM.....RDM
LONG TERM......KLJ
AVIATION.......Kieckbusch

Hazardous Weather Outlook
National Weather Service Green Bay WI
1135 AM CDT Tue Jul 6 2021

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-071645-
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-
1135 AM CDT Tue Jul 6 2021

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

.DAY ONE...This Afternoon and Tonight

There is a slight chance of severe thunderstorms, mainly for
areas south of highway 29 between 3 pm and 8 pm. Damaging winds,
torrential rainfall and hail are the main threats. An isolated
tornado is also possible in central Wisconsin. A threat of heavy
rainfall and urban and small stream flooding will continue through
tonight.

Building waves on Lake Michigan late this afternoon and tonight
could create dangerous swimming conditions at beaches along Lake
Michigan.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Urban and small stream flooding remains possible through Wednesday
morning as rainfall continues.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening.

LMZ521-522-541>543-071645-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
1135 AM CDT Tue Jul 6 2021

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

.DAY ONE...This Afternoon and Tonight

Conditions hazardous to small craft are expected late this
afternoon and tonight due to gusty northeast winds and building
waves. A Small Craft Advisory is in effect.

Thunderstorms are possible at times this afternoon and overnight.
Gusty winds, hail, and cloud to water lightning will pose a threat
to boaters.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Conditions hazardous to small craft are possible Wednesday into
Thursday due to persistent and gusty northeast winds.

Kieckbusch

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREEN BAY WI
130 PM CDT TUE JUL 6 2021

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

0124 PM     TSTM WND GST     MANITOWOC               44.08N 87.66W
07/06/2021  M56 MPH          MANITOWOC          WI   AWOS

&&

SAC

Special Weather Statement
National Weather Service Green Bay WI
136 PM CDT Tue Jul 6 2021

WIZ020-022-031-037>040-045-048>050-074-061930-
Calumet WI-Southern Oconto County WI-Waupaca WI-Shawano WI-
Kewaunee WI-Outagamie WI-Winnebago WI-Waushara WI-Manitowoc WI-
Door WI-Brown WI-Menominee WI-
136 PM CDT Tue Jul 6 2021

...SIGNIFICANT WEATHER ADVISORY FOR BROWN...KEWAUNEE...SOUTHERN
DOOR...CALUMET...SOUTHEASTERN MENOMINEE...WINNEBAGO...EASTERN
WAUSHARA...EASTERN WAUPACA...SOUTHERN OCONTO...OUTAGAMIE...EASTERN
SHAWANO AND MANITOWOC COUNTIES UNTIL 230 PM CDT...

At 133 PM CDT, Doppler radar was tracking strong thunderstorms
scattered around northeast and east central Wisconsin. The strongest
storms were located near Clintonville and Manitowoc, and were moving
east at 20 mph. Storms are expected to increase in coverage over the
next hour or two, and a few may become severe.

Half inch hail and wind gusts up to 50 mph will be possible with
these storms.

Locations impacted include...
Green Bay, Appleton, Oshkosh, Manitowoc, Shawano, Sturgeon Bay,
Kewaunee, Bay Shore Park, Menasha and Kaukauna.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional
information and possible warnings from the National Weather Service.

&&

LAT...LON 4390 8889 4398 8889 4398 8895 4489 8891
      4489 8777 4486 8777 4471 8792 4463 8793
      4469 8780 4487 8765 4488 8727 4472 8729
      4433 8748 4418 8745 4407 8759 4390 8769
      4389 8816 4394 8816 4394 8840 4389 8840
TIME...MOT...LOC 1833Z 253DEG 10KT 4455 8868

Kieckbusch