Special Marine Warning 44, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
601 AM CDT Tue Aug 24 2021

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 352 AM CDT Tue Aug 24 2021

The main concern in the short-term portion of the forecast will be
the potential for strong to severe storms today and the overall
evolution of the thunderstorms this morning into early this
afternoon.

Radar imagery this morning shows a persistent MCS rolling across
west-central MN with some convection developing ahead of the feature
near Minneapolis. This secondary area of convection is along the
surface frontal boundary. Overall convective evolution may be
impacted by interactions with this leading convection, but the
latest HRRR guidance seems to have a very good depiction of
intensity and placement of the convection. That has been the case
through much of the night.

Today: A nearly stationary front, draped across central MN eastward
through northern WI, will lift slowly north this afternoon as a warm
front. Aloft, a shortwave is expected to shift eastward along or
just south of the front. The ongoing line of strong to severe
thunderstorms over western MN this morning, will continue to shift
eastward into central WI by late morning or early afternoon.
Provided that the storms remain strong to severe, the most likely
impact would be damaging winds and brief heavy downpours. As far as
location, most of the hi-res guidance has been inconsistent (model
to model/run to run) on placement; however, the HRRR has been more
consistent and in line with the latest observed
precipitation/convection. The HRRR solution as tends to make sense
as the strongest portion of the storms would likely remain south of
the aforementioned front and would likely remain along the CAPE
gradient. The greatest CAPE gradient is progged to be from roughly
Marathon County eastward to roughly Brown and Kewaunee County, where
mid-level lapse rates are expected to be near 7 to 7.5 C/km. Again,
those areas would run the greatest risk of seeing damaging winds and
heavy downpours. Deep-layer shear vectors (similar to 0-3km) are
expected to be around 30kts to 40 kts and orthogonal to the the
north/south line of storms. This would support surging/bowing
sections in the line, again, leading to a damaging wind threat.
Otherwise, temperatures are expected to warm into the mid to
possibly upper 80s, with more humid conditions.

Tonight: Low pressure will slowly approach from the west as the
aforementioned warm front becomes nearly stationary along the UP/WI
border as a cold front slowly approaches from the west. This will
keep scattered showers and thunderstorms in the forecast through
much of the night. The greatest threat for seeing showers and storms
will remain near the fronts as the forcing will be greater in those
areas, but storms can't be ruled out in the unstable airmass,
provided that there is enough of a trigger from lingering
boundaries. The NAM/GFS are hinting at a shortwave passing through
the area tonight, but this has not been a consistent signal over the
past few runs. MUCAPE values are expected to be around 1000 J/kg,
but shear is only expected to be around 20 to maybe 25kts. This will
help to limit any severe potential tonight. Overnight lows are
expected to be in the 60s to around 70, warmest central/east-central.

Wednesday: The surface low is expected to lift northeast and east as
it drags the cold front through the area from west to east
throughout the day. Instability is expected to increase ahead of the
front, greatest across east-central and far northeast Wisconsin,
with values reaching around 1500-2500 J/kg. Deep-layer shear is only
progged to be around 20kts, so not expecting widespread severe
weather. The storms could pulse up from time to time over east-
central and far northeast Wisconsin with the main threat from any
storms being small hail, gusty winds and heavy downpours. Otherwise,
high temperatures are expected to be in the 80s for much of the
forecast area.

.LONG TERM...Wednesday Night Through Monday
Issued at 352 AM CDT Tue Aug 24 2021

Similar to the past several nights, the extended forecast remains
active with several rounds of rain and thunderstorms through early
next week. An upper level trough across the Pacific Northwest and
a broad ridge across the southeast CONUS will lead to southwest
flow across WI. Within this flow will be several embedded
shortwaves and sfc boundaries. A cooler/drier airmass will reside
north of this upper jet, and to the south a warm and moist
airmass with high pwats will be in place. Combine this with
effects from daytime heating and the nocturnal LLJ, and bouts of
heavy rain and thunderstorms will be possible nearly every
day/night. Timing out these episodes is nearly impossible as each
event will influence the next, so there will be dry times as
well, despite the abundance of PoPs in the forecast.

The next main period of interest and potential impact is Thursday
into Friday. With a sfc boundary still lingering and a shortwave
coming through models are indicating a complex could develop west
of the forecast area, and then track through central and/or
northeast WI bringing heavy rainfall and storms with strong winds.
Timing is still all over the place, but the GFS/ECMWF/CMC all
show high QPF amounts of 2+ inches during this stretch. Pwats will
be near climatological maximum as well. As a result, WPC has
highlighted nearly the entire CWA in the Day3 Marginal Risk of
excessive rainfall (level 1 out of 4) with central WI in a Slight
Risk of excessive rainfall (level 2 out of 4). Will continue to
evaluate trends as the time gets closer.

Temps will be above normal each day, sometimes by a degree or two,
other times closer to 10 degrees above normal, just depending on
where the boundary situates each day. Temps and humidity look to
fall back closer to normal Thursday and Friday, and then bounce up
again for the weekend.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 601 AM CDT Tue Aug 24 2021

Patchy dense fog can be expected at each of the TAF sites through
sunrise or just after sunrise. Outside of the dense fog early in
the TAF period, a complex of thunderstorms will approach the TAF
sites first across central Wisconsin and then into east-central
Wisconsin by late morning or early afternoon. Additional
development is possible late in the afternoon, but confidence is
fairly low at this point. Gusty winds, heavy rain and frequent
lightning will be the main threats. Outside of the fog this
morning, ceilings and visibilities are expected to be VFR, except
as low as IFR in intense rainfall. Some patchy fog may form again
tonight, depending on cloud cover and any lingering showers and
storms.
&&

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

SHORT TERM.....Cooley
LONG TERM......KLJ
AVIATION.......Cooley

Hazardous Weather Outlook
National Weather Service Green Bay WI
450 AM CDT Tue Aug 24 2021

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-251000-
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-
450 AM CDT Tue Aug 24 2021

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

.DAY ONE...Today and Tonight

Patchy dense fog may cause rapid reductions of visibilities on
roadways through the morning commute, which may pose a hazard to
motorists.

Thunderstorms are expected today and tonight. Some of the storms
could be severe, especially late this morning through mid
afternoon. The primary risk will be damaging wind gusts.
Torrential rainfall and hail are also possible.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Thunderstorms are possible at times during the remainder of the
upcoming work week. It is too early to determine whether
subsequent rounds of storms will pose a severe weather threat;
however, very heavy rainfall will be possible at times.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed late this morning into this
afternoon.

LMZ521-522-541>543-251000-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
450 AM CDT Tue Aug 24 2021

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

.DAY ONE...Today and Tonight

Thunderstorms are expected today and tonight. Any thunderstorms
will pose a hazard to mariners.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Thunderstorms are possible at times during the remainder of the
upcoming work week. Any thunderstorms will pose a hazard to
mariners.

Cooley/KLJ

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREEN BAY WI
1057 AM CDT TUE AUG 24 2021

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

1047 AM     TSTM WND GST     WAUSAU                  44.96N 89.63W
08/24/2021  M44 MPH          MARATHON           WI   ASOS

&&

ECKBERG

Special Weather Statement
National Weather Service Green Bay WI
1124 AM CDT Tue Aug 24 2021

WIZ019>021-030-031-035>038-074-241715-
Southern Oconto County WI-Waupaca WI-Shawano WI-Langlade WI-
Outagamie WI-Northern Oconto County WI-Wood WI-Marathon WI-
Portage WI-Menominee WI-
1124 AM CDT Tue Aug 24 2021

...Showers and thunderstorms will impact portions of eastern Wood,
Portage, eastern Marathon, Menominee, Waupaca, Oconto, northwestern
Outagamie, southern Langlade and Shawano Counties through 1215 PM
CDT...

At 1123 AM CDT, Doppler radar was tracking a large cluster of
showers and thunderstorms across central into portions of northeast
Wisconsin this morning. The strongest storms extended across Portage
and Waupaca counties. The showers and thunderstorms were moving east
at 35 mph.

HAZARD...Wind gusts to around 40 mph and locally heavy rainfall are
         possible with the strongest storms.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
  Clintonville, Embarrass, Shawano, Navarino Wildlife Area, Waupaca,
  Embarrass, Big Falls, Stevens Point, Bancroft, Wausau and Mosinee.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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

&&

LAT...LON 4512 8963 4512 8943 4517 8942 4530 8845
      4478 8813 4424 8912 4425 9006
TIME...MOT...LOC 1619Z 268DEG 31KT 4474 8907

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH

Eckberg

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREEN BAY WI
1126 AM CDT TUE AUG 24 2021

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

1102 AM     TSTM WND GST     APPLETON                44.26N 88.40W
08/24/2021  M38.00 MPH       OUTAGAMIE          WI   AWOS

1102 AM     TSTM WND GST     WAUTOMA                 44.06N 89.28W
08/24/2021  M37.00 MPH       WAUSHARA           WI   AWOS

&&

ECKBERG

Special Weather Statement
National Weather Service Green Bay WI
1128 AM CDT Tue Aug 24 2021

WIZ036>040-045-048>050-241730-
Calumet WI-Waupaca WI-Kewaunee WI-Outagamie WI-Winnebago WI-
Waushara WI-Manitowoc WI-Portage WI-Brown WI-
1128 AM CDT Tue Aug 24 2021

...Strong thunderstorms will impact portions of Brown, southeastern
Portage, Kewaunee, Calumet, Winnebago, Waushara, southern Waupaca,
Outagamie and Manitowoc Counties through 1230 PM CDT...

At 1125 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 7 miles northeast of Black Creek to 6 miles
east of Kaukauna to near Central Lake Winnebago. Movement was east
at 30 mph. Additional clusters of thunderstorms were occurring
across much of Waushara County, and will shift east into the Fox
Valley within the next hour.

HAZARD...Winds in excess of 40 mph, half inch hail and torrential
         rainfall.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible. Periods of torrential rainfall could result in
         some urban flooding in the Fox Valley.

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

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with these storms and may lead
to localized urban flooding in the Fox Valley. Do not drive your
vehicle through flooded roadways.

&&

LAT...LON 4390 8889 4398 8889 4398 8960 4425 8963
      4429 8911 4457 8851 4459 8825 4465 8824
      4468 8799 4476 8787 4463 8793 4478 8772
      4468 8774 4468 8764 4443 8744 4390 8769
      4389 8816 4394 8840 4389 8840
TIME...MOT...LOC 1625Z 257DEG 26KT 4453 8833 4432 8814 4398 8846

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

Kieckbusch

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