Special Weather Statement, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
1256 PM CDT Thu Jun 24 2021

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Friday
Issued at 314 AM CDT Thu Jun 24 2021

Clusters and small lines of strong to marginally severe
thunderstorms have developed in NW WI, on the nose of a 40+ knot
low-level jet, and on the northern edge of a strong elevated
instability gradient. Deep layer shear of 35-40 knots, and SRH
of 200-400 was aiding in the organization, and a cell or two were
exhibiting supercell characteristics. Expect this activity to
shift southeast through GRB CWA between 09z-15z. Due to the
elevated nature of the storms and DCAPE values of only 600-1000
J/KG, suspect it will be difficult to get severe winds to the
surface. Could see some marginally severe hail, especially across
northern WI, where WBZ heights were around 10K feet.

Expect somewhat of a lull in the convection after the first round
exits in the mid to late morning. Although meso-models offer
varying solutions, there is some support for redevelopment near a
cold frontal boundary in parts of north central and far northeast
WI in the late afternoon. This activity would sag south during the
evening, then gradually weaken with the loss of daytime heating.
This scenario is not a slam dunk, as this morning's convection and
lingering cloud cover could limit destabilization. Plus there is
not much of a trigger evident, aside from the frontal boundary.
Any storms that develop will have potential to produce heavy
rainfall, as PWATs are expected to increase to 1.5+ inches.

Have gone a bit more aggressive in decreasing the pops from
northwest to southeast overnight tonight, and only plan to keep
small pops over central and east central WI on Friday, as the
cold front shifts south of the region.

Highs both days will be in the 70s to lower 80s. Lows tonight
should range from the middle to upper 50s far northwest to the
middle to upper 60s south.

.LONG TERM...Friday Night Through Wednesday
Issued at 314 AM CDT Thu Jun 24 2021

Mean flow to become highly-amplified this weekend with strong
upper ridges over the western CONUS/western Atlantic and a
longwave trough over central/east-central NOAM. Once this pattern
develops, do not anticipate much of a change which leave northeast
WI vulnerable to several embedded shortwaves to rotate through WI
next week. Trying to time precipitation chances will be the
biggest forecast challenge. Temperatures look to be near normal
through the period.

Friday night and Saturday...
Quasi-stationary front (former cold front) appears to be situated
from southwest WI through east-central WI Friday night and remain
the main focal point for showers/thunderstorms. Thus, northern WI
may now not see much precipitation and have kept pops rather low.
Conversely, high chance pops continue over east- central WI with
convergence along the front. Min temperatures to range from the
lower to middle 50s far north-central WI, to the lower 60s over
east-central WI. The main challenge for Saturday will be the
eventual track of a surface wave that is expected to ride along
the frontal boundary. Models continue to significantly differ on
this track which places a great deal of uncertainty on where to
place highest chances for precipitation. A southern track could
keep northern WI completely dry Saturday, while a northern track
could bring a decent amount of rain to much of northeast WI.
Severe potential looks minimal due to cloud cover and lack of
instability. However, localized flooding is possible with PW
values greater than 1.5 inches over central/east-central WI. Max
temperatures on Saturday to mainly be in the lower to middle 70s,
although a southern track would allow readings to be warmer over
the north.

Saturday night and Sunday...
If the northern track of the surface wave is correct (as is
favored by the majority of the models), additional rounds of
showers/thunderstorms would move across northeast WI Saturday
night, especially during the evening hours. Once again, locally
heavy rain is possible so isolated flooding cannot be ruled out.
Min temperatures to range from the lower 50s north-central, to
around 60 degrees east-central WI. Potential does exist for a
break in the precipitation on Sunday as the surface wave exits
the area, the frontal boundary sags farther south and the new
upper trough to still be digging south-southeast over the northern
Plains/Upper MS Valley. Do not have enough confidence to go rain-
free as residual moisture still over the region and any subtle
mid-level shortwave could generate showers. Max temperatures on
Sunday to range from the middle 70s to around 80 degrees.

Sunday night and Monday...
Models appear to be digging this new upper trough far west
(northern/central Plains) than what has been indicated over the
past couple of days. This shift could keep most of northeast WI
dry Sunday night, then reintroduce a chance of showers/slight
chance of thunderstorms mainly for Monday afternoon as daytime
heating interacts with shortwave energy moving through the
southwest flow aloft. Max temperatures on Monday to be in the
middle to upper 70s north/near Lake MI, upper 70s to lower 80s
elsewhere.

Monday night and Tuesday...
Precipitation would diminish Monday evening with the loss of
daytime heating with the rest of Monday night looking dry. Models
have different ideas with respect to the upper trough by Tuesday
as the GFS closes off the trough into an upper low over the
northern Plains, while the ECMWF/GEM shift the trough east into
the Upper MS Valley. Either way, anticipate a repeat of Monday
with a chance of precipitation developing primarily in the
afternoon. Max temperatures to mainly be in the upper 70s to lower
80s.

Tuesday night and Wednesday...
Precipitation chances would then continue Tuesday night into
Wednesday as the upper trough swings into the western Great Lakes
region (assuming the majority solution is correct). Chance pops
will suffice for now with max temperatures on Wednesday again in
the upper 70s to lower 80s.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1255 PM CDT Thu Jun 24 2021

ceilings of 2500 to 3500 feet and scattered showers
are expected across the area through the late afternoon and early
evening hours. Thunderstorms are expected to form between MSP and
EAU during the late afternoon and expand northeast ahead of a
weak cold front. The activity is forecast to move slowly southeast
across the region during the evening hours.

Shower and thunderstorm activity should diminish overnight, with
low clouds and IFR conditions over much of the area after
midnight.

Low clouds may be slow to leave Friday morning, but once they do
conditions should improve to VFR in most areas by late afternoon.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement through late tonight for WIZ022-040-050.
&&

SHORT TERM.....Kieckbusch
LONG TERM......Kallas
AVIATION.......RDM

Hazardous Weather Outlook
National Weather Service Green Bay WI
328 AM CDT Thu Jun 24 2021

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-250830-
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-
328 AM CDT Thu Jun 24 2021

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

.DAY ONE...Today and Tonight

Thunderstorms will move through the region this morning. Although
an isolated severe storm with large hail is possible, most of the
storms should remain below severe limits, with gusty winds, small hail
and brief heavy downpours anticipated.

Additional thunderstorms are possible, especially during the late
afternoon and evening. There is a slight risk of severe storms
with damaging winds, large hail and heavy rainfall.

Hazardous swimming conditions are likely along Lake Michigan
beaches through this evening.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Thunderstorms are possible Friday into Friday evening. No severe
weather is expected at this time.

Periodic chances of thunderstorms can be expected from Saturday
into Wednesday. At this time, it is too early to determine
whether any of these storms may become severe.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed today into tonight.

LMZ521-522-541>543-250830-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
328 AM CDT Thu Jun 24 2021

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

.DAY ONE...Today and Tonight

Conditions hazardous to small craft are expected today into this
evening, mainly on Lake Michigan.

There is a chance of thunderstorms this morning and again later
this afternoon into tonight. Any storms will pose a hazard to
boaters.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Periodic chances of thunderstorms can be expected Friday into
Saturday. Any thunderstorms would pose a hazard to boaters.

Kieckbusch/Kallas

Special Weather Statement
National Weather Service Green Bay WI
825 AM CDT Thu Jun 24 2021

WIZ037>040-045-048>050-241415-
Calumet WI-Waupaca WI-Kewaunee WI-Outagamie WI-Winnebago WI-
Waushara WI-Manitowoc WI-Brown WI-
825 AM CDT Thu Jun 24 2021

...SPECIAL WEATHER STATEMENT...

At 824 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Two Creeks to near Valders to 10 miles
northwest of Oshkosh to near Wautoma. Movement was southeast at 35
mph.

Half inch hail, winds in excess of 30 mph and torrential rainfall
will be possible with these storms.

Locations impacted include...
Appleton, Oshkosh, Manitowoc, Kewaunee, Wautoma, Menasha, Kaukauna,
Little Chute, Kimberly and Chilton.

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. Do not drive your vehicle through
flooded roadways.

&&

LAT...LON 4390 8889 4398 8889 4398 8938 4421 8950
      4434 8864 4436 8799 4451 8757 4438 8746
      4418 8745 4407 8759 4389 8770 4389 8816
      4394 8816 4394 8840 4389 8840
TIME...MOT...LOC 1324Z 330DEG 29KT 4432 8762 4412 8793 4416 8864 4402
8929

Kieckbusch

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREEN BAY WI
826 AM CDT THU JUN 24 2021

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

0824 AM     HAIL             ZITTAU                  44.21N 88.78W
06/24/2021  M0.25 INCH       WINNEBAGO          WI   TRAINED SPOTTER

&&

BERSCH

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREEN BAY WI
838 AM CDT THU JUN 24 2021

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

0823 AM     HAIL             4 SE APPLETON           44.22N 88.34W
06/24/2021  M0.25 INCH       CALUMET            WI   PUBLIC

&&

MPC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREEN BAY WI
1019 AM CDT THU JUN 24 2021

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

1000 AM     HEAVY RAIN       ROSHOLT                 44.63N 89.30W
06/24/2021  M1.15 INCH       PORTAGE            WI   CO-OP OBSERVER

1000 AM     HEAVY RAIN       WAUPACA                 44.34N 89.06W
06/24/2021  M1.09 INCH       WAUPACA            WI   AWOS

&&

BERSCH

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREEN BAY WI
1206 PM CDT THU JUN 24 2021

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

1200 PM     HEAVY RAIN       6 SE FREMONT            44.20N 88.77W
06/24/2021  M1.46 INCH       WINNEBAGO          WI   CO-OP OBSERVER

&&

BERSCH

Special Weather Statement
National Weather Service Green Bay WI
116 PM CDT Thu Jun 24 2021

WIZ020>022-031-073-074-241915-
Southern Oconto County WI-Southern Marinette County WI-Shawano WI-
Northern Oconto County WI-Door WI-Menominee WI-
116 PM CDT Thu Jun 24 2021

...SPECIAL WEATHER STATEMENT...

At 113 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from South Branch to 7 miles southeast of Gillett to
6 miles north of Bay Shore Park. Movement was east at 30 mph.

Heavy rain, pea size hail and winds in excess of 30 mph will be
possible with these storms.

Locations impacted include...
Marinette, Sturgeon Bay, Menominee, Oconto, Gillett, Jacksonport,
Pound, Ephraim, Egg Harbor and South Branch.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm.

&&

LAT...LON 4508 8699 4467 8733 4467 8782 4499 8742
      4503 8754 4494 8759 4491 8777 4469 8793
      4473 8825 4485 8851 4512 8864 4526 8771
      4517 8774 4511 8766 4512 8754 4504 8753
      4500 8742 4508 8736 4521 8742 4532 8695
TIME...MOT...LOC 1813Z 264DEG 26KT 4500 8851 4482 8819 4472 8776

Bersch