Special Weather Statement, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
640 AM CDT Tue Apr 27 2021

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 403 AM CDT Tue Apr 27 2021

Forecast Highlights:
--Today... Showers and thunderstorms expected across much of the
area, with marginal severe weather threat.
--Tonight/Tomorrow... Rain intensity diminishes around sunrise, with
lingering clouds and a few light showers into the afternoon.

--General Discussion--

Today... As has been well-advertised over the past week, showers and
thunderstorms are expected across the area. Trends have been for the
"warmest" temperatures to stay to our south, and that trend has
continued for this update. Last week, it appeared temperatures would
be in the 70s for today, but confidence is high that the 70s will
stay in southern Wisconsin, leaving highs in the 50s for most of our
area. As such, the greatest threat for thunderstorms will be south
of our area as well. The threat for severe weather in NE/Northern
Wisconsin is low. Rainfall amounts for today look to be in the 0.1
to 0.25 inch range, with most of the rain falling in the afternoon
and evening hours.

Tonight/Tomorrow... At this time, there may be lingering
thunder/lightning into early Wednesday morning from the Tuesday PM
storms. But by sunrise Wednesday morning, only showers are expected,
and rainfall intensity will diminish. Clouds and light showers will
likely linger into the afternoon hours, but Wednesday afternoon
rainfall amounts should only be a few hundredths of an inch at best.

--Scientific Discussion--

Today... All eyes on how far north the boundary of warm air makes it
into Wisconsin today. Trends over the past few days have nudged the
boundary further and further south with each run. As evidenced from
a 950mb frontogenetical forcing cross-section, the leading surge
of warm air looks to be close to the I-94 corridor, with the
secondary boundary layed out near the WI/IL border. This area is
where the sufficient focusing will be to perhaps punch the cap for
a few elevated storms that could produce small hail. There is a
non-zero chance for severe weather in our area, but at this time,
it appears difficult to find a focusing mechanism sufficient to
break the cap. As mentioned above, temperatures trending
downward... current forecast still may be a few degrees too warm.

Tonight/Tomorrow... Forecast models in good agreement with advecting
boundary southward into Illinois. By 12z Wed, boundary should be
near the Quad Cities to Chicago area. Along with it, the best
kinematic forcing should be south of our area. Still a broad area of
light/weak 850mb frontogenetical forcing over a "stagnant" air
field at 850mb will help keep stratus deck and some light showers
across our area into Wednesday afternoon. As mentioned above,
minimal QPF, with no thunder forecast.

.LONG TERM...Wednesday Night Through Monday
Issued at 403 AM CDT Tue Apr 27 2021

Precipitation can be expected to start off the extended period
before weak high pressure rounds out the work week and the
beginning of the work week. As zonal flow aloft establishes itself
over the weekend, a fairly progressive pattern will bring multiple
rounds of active weather through the region early next week.

Wednesday night through Thursday...The first challenge for the
extended forecast comes Wednesday night, as a weak low pressure
system over the Central Plains moves northwards towards the Great
Lakes. The latest trend by the GFS brings this low across the
western Great Lakes, which would bring in more widespread
precipitation overnight into Thursday, but most other models keep
the WAA and low to the south. For now, kept some chance pops in
from initial guidance, but wouldn't be surprised if updates bring
a drier forecast going forwards. In either case, another shortwave
follows on the heels of this system, skirting across northern
Wisconsin Thursday night for another light precipitation chance.
The uncertainty in the pops will unfortunately carry over into the
high temps for Thursday, as temps will be quite a bit cooler if
the overnight pops materialize. Again, trended on the warmer side
for now, as the pops do seem a bit overdone at this time.

Rest of the forecast...Weak high pressure will move into the
region at the end of the work week and the beginning of the
weekend. This should provide a dry period for at least Friday and
early Saturday. Flow aloft then flattens out to a more progressive
and zonal pattern, which will serve to bring multiple shortwaves
through the region during the weekend, and a few stronger system
next week. The exact strength and timing are difficult to assess
at this point in time, but several chances for precipitation are
likely towards the end of the extended. The good news is that
temperatures should come up considerably towards the end of the
week, with highs into the 70s by the Friday and over the weekend.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 637 AM CDT Tue Apr 27 2021

KRHI has been in LIFR all morning, and northern Wisconsin should
stay in the LIFR/IFR range through today and into the overnight
hours tonight. Elsewhere, VFR skies will gradually lower to MVFR
by this afternoon and seemingly IFR overnight tonight.

Included VCTS during the afternoon/early evening during the best
chances for thunder. Will likely need to fine-tune this with the
next TAF issuance.

&&

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

SHORT TERM.....Kotenberg
LONG TERM......Uhlmann
AVIATION.......Kotenberg

Hazardous Weather Outlook
National Weather Service Green Bay WI
419 AM CDT Tue Apr 27 2021

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-280930-
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-
419 AM CDT Tue Apr 27 2021

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

.DAY ONE...Today and Tonight

Thunderstorms are possible today. There is a marginal risk for
severe weather, with hail as the main threat.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

A few thunderstorms are possible into early Wednesday morning.
Severe weather is not expected.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not likely be needed.

LMZ521-522-541>543-280930-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
419 AM CDT Tue Apr 27 2021

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

.DAY ONE...Today and Tonight

Gusty east winds and building waves will create conditions hazardous
for small craft on Lake Michigan this morning.

Thunderstorms are possible today and tonight, which would create a
lightning hazard to mariners.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

There is a chance of thunderstorms early Wednesday morning, which
would create a lightning hazard to mariners.

Kotenberg/Uhlmann

Special Weather Statement
National Weather Service Green Bay WI
1036 AM CDT Tue Apr 27 2021

WIZ013-019>021-073-271630-
Southern Marinette County WI-Langlade WI-Northern Oconto County WI-
Menominee WI-Northern Marinette County WI-
1036 AM CDT Tue Apr 27 2021

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL MARINETTE...NORTH CENTRAL
MENOMINEE...NORTHERN OCONTO AND EAST CENTRAL LANGLADE COUNTIES UNTIL
1130 AM CDT...

At 1035 AM CDT, Doppler radar was tracking strong thunderstorms near
Wausaukee, 5 miles east of Lakewood and 20 miles east of Antigo,
moving northeast at 35 mph.

Penny size hail will be possible with these storms.

Locations impacted include...
Mountain, Wausaukee, White Lake, Gardner Dam Scout Camp, Bear Paw
Scout Camp, Langlade, Middle Inlet, Lakewood, Athelstane and Boot
Lake Campground.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4506 8877 4524 8877 4555 8782 4554 8780
      4550 8779 4547 8781 4544 8786 4541 8785
      4538 8788 4537 8787 4535 8789 4535 8788
      4536 8787 4534 8785 4535 8782 4535 8775
      4539 8769 4535 8765
TIME...MOT...LOC 1533Z 244DEG 31KT 4530 8827

Eckberg

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREEN BAY WI
1218 PM CDT TUE APR 27 2021

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

1218 PM     HAIL             CRIVITZ                 45.23N 88.01W
04/27/2021  M0.50 INCH       MARINETTE          WI   TRAINED SPOTTER

&&

SAC

Special Weather Statement
National Weather Service Green Bay WI
1220 PM CDT Tue Apr 27 2021

WIZ020-021-030-031-036-073-074-271800-
Southern Oconto County WI-Southern Marinette County WI-Shawano WI-
Northern Oconto County WI-Marathon WI-Portage WI-Menominee WI-
1220 PM CDT Tue Apr 27 2021

...STRONG THUNDERSTORMS MOVING ACROSS PORTIONS OF CENTRAL INTO
NORTHEAST WISCONSIN...

At 1220 PM CDT, Doppler radar was tracking strong thunderstorms
along a line from Junction City in Portage County to Wittenberg to
Neopit northeast into northern Oconto County. The thunderstorms were
moving northeast at 30 mph.

Half inch hail and brief heavy rain will be possible with these
storms. Some of these storms could intensify this afternoon and
produce large hail.

Locations impacted include...
Stevens Point, Whiting, Bevent, Wittenberg, Mountain, Big Smokey
Falls, Bear Paw Scout Camp, Neopit, South Branch and Keshena.

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.

&&

LAT...LON 4537 8809 4515 8801 4468 8915 4468 8922
      4465 8922 4446 8967 4459 8981
TIME...MOT...LOC 1717Z 225DEG 26KT 4508 8862 4448 8989

Eckberg