Severe Thunderstorm Warning 30, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
653 PM CDT Fri Jul 28 2023

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Saturday
Issued at 337 PM CDT Fri Jul 28 2023

Complex/messy mesoscale/synoptic set-up making for a complicated
forecast this afternoon into tonight. Main focus will be timing
best chances for storms and if any will be on the strong side.

For this afternoon into tonight...weak surface boundary,
instability gradient and FGEN centered around 850mb, combined
with daytime heating generating MUCAPEs of 1000-2000 J/kg will
continue to produce isolated to scattered showers and storms
extending east-west over parts of central and east-central WI.
Main threats with this activity will be heavy rain and small hail
as they should mainly remain elevated. Then attention turns to
this evening as a more potent shortwave tracks into WI, likely
kicking off additional showers and storms. Instability gradient
still expected to be in place, with the pool of very instability
well to our south in southern WI. Think the strongest of the
storms, along with the main threat for severe weather, will build
south/east into the better instability. We will be on the northern
part of this and it may clip the southern CWA. Models are mixed
on if and how widespread activity north of the main complex will
behave tonight, with the HRRR very aggressive with more widespread
activity, but other models have little to no activity. So
confidence not great on how it will play out as you work to the
north. Plenty of bulk shear to work with (around 50 kts) so any
storms could be well organized and have the chance to produce hail
and some brief gusty winds (especially if a cold pool can get
established with the complex and it clips the southern counties).
Some fog is expected later tonight as temps cool, especially in
central and north central WI where winds are lighter in the
boundary layer. Lows will drop into the 50s to low 60s for most
spots.

For Saturday...some lingering showers will be possible over north
central WI in the early morning, then additional showers will be
possible in the later morning and afternoon as a weak secondary
frontal boundary drops south across northeast WI within a
northwest upper flow, along with a weak shortwave and departing
upper jet. A narrow ribbon of moisture and instability be just
enough to touch off a storm, but will just mention showers for
now. If models continue to trend more aggressive with this
activity, PoPs will need to be expanded. It will be a little
cooler and noticeably less humid with highs in the mid 70s to mid
80s.

.LONG TERM...Saturday Night Through Friday
Issued at 337 PM CDT Fri Jul 28 2023

Summary: Generally quiet weather will prevail Sunday into
Tuesday, outside of warming temperatures. There may be a period of
strong thunderstorms again Wednesday PM as southerly flow returns
and a low pressure system in northern Ontario crosses the Upper
Great Lakes region.

Deep low pressure centered over northern Quebec on Sunday and
amplifying ridging over the northern High Plains keeps the central
United States under mild northwest flow Sunday into Monday. This
is generally expected to be a dry period for north-central and
northeast Wisconsin. Temperatures aloft warm by a degree or two
from Sunday into Monday, but largely support near-normal daytime
high temperatures for the beginning of next week.

The ridge axis aloft shifts eastward into the Missouri Valley
Monday night into Tuesday as lower-level high pressure over the
Upper Midwest drops into the Ohio River Valley. This creates a
return flow into northeast Wisconsin by Tuesday morning. Expect
an increase in daytime high temperatures for Tuesday as a result.
Low pressure over northern Manitoba breaks down the central CONUS
ridge Tuesday night to further increase temperatures Wednesday
ahead of the next chance of possible stronger thunderstorms to
work into northeast Wisconsin later Wednesday. There may be a
chance of severe thunderstorms in this time period as well, but
further analysis will be needed over the next few days pending
similar guidance trends.

Northwest flow may then return behind the cold front later
Thursday as the low then centered in northeast Ontario moves
further eastward.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 653 PM CDT Fri Jul 28 2023

Outflow from elevated storms that were ongoing at the beginning of
the TAF period over and west of GRB produced additional
thunderstorms across central to northeastern WI. These storms are
slow moving with mainly a hail concern that may expand into
central WI, impacting AUW and CWA. Included a prevailing
thunderstorm for the central WI areas. Additionally, storms coming
through from western WI will be a little faster moving, and may
bring some rain and winds gusts to the Fox Valley a few hours
later. A few wind gusts up to 30 or 35 knots have been observed,
but confidence remains low these will hold together for the
region. Forecast still calls for the strongest storms, along the
southern portion of this line, to mostly miss the Fox Valley to
the south. Will amend in the next few hours if the wind threat
becomes higher in confidence. Behind the storms from tonight, fog
will be possible across central to north-central WI before dawn.
Good flying weather then prevails for Saturday.

.KOSH...

TSRA activity north of the airfield from early in the afternoon is
not expected to impact the airfield for the first few hours of the
TAF period. Prevailing rain and possible some thunderstorms are
now expected to arrive with the line of storms to the west, so the
TEMPO group was pushed back. Still minimal wind threat observed
within this line, so confidence in including winds in the TEMPO
group was low. Suspect small hail and heavy rainfall will be the
primary concerns. Behind this, some scattered low stratus will be
possible. Good flying conditions follow for Saturday.
&&

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

SHORT TERM.....Bersch
LONG TERM......NLY
AVIATION.......Uhlmann

Hazardous Weather Outlook
National Weather Service Green Bay WI
640 PM CDT Fri Jul 28 2023

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-292345-
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-
640 PM CDT Fri Jul 28 2023

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

.DAY ONE...Tonight

There is a chance of thunderstorms, especially across central and
east-central WI. A severe thunderstorm watch is in effect from for
portions of central Wisconsin. Some of these storms may become
strong to locally severe into this evening, mainly along and south
of Highway 29. Hail, damaging winds, and heavy downpours and
localized flooding are be the primary threats.

.DAYS TWO THROUGH SEVEN...Saturday through Friday

The chance of thunderstorms will return during the Wednesday
through Thursday time frame and may produce some stronger
thunderstorms.

.SPOTTER INFORMATION STATEMENT...

Spotters are requested to report hail, wind gusts over 40 mph, and
rain totals over one inch to the National Weather Service in
Green Bay.

LMZ521-522-541>543-292345-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
640 PM CDT Fri Jul 28 2023

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

.DAY ONE...Tonight

There is a chance of thunderstorms. Some of these storms may
become strong and could pose a hazard to mariners.

.DAYS TWO THROUGH SEVEN...Saturday through Friday

The chance of thunderstorms will return during the Wednesday
through Thursday time frame and may produce some stronger
thunderstorms.

Uhlmann

Preliminary Local Storm Report
National Weather Service Green Bay WI
742 PM CDT Fri Jul 28 2023

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

0725 PM     Hail             2 WSW Rib Falls         44.95N 89.93W
07/28/2023  E1.00 inch       Marathon           WI   Public

            Report from mPING: Quarter (1.00 in.).

&&

Preliminary Local Storm Report
National Weather Service Green Bay WI
756 PM CDT Fri Jul 28 2023

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

0356 PM     Hail             1 S Iola                44.49N 89.11W
07/28/2023  M1.00 inch       Waupaca            WI   Public

            Two public reports of estimated quarter to
            half dollar sized hail that fell on the
            south side of Iola. Time estimated based on
            combination of reports and radar.

&&

Preliminary Local Storm Report
National Weather Service Green Bay WI
813 PM CDT Fri Jul 28 2023

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

0751 PM     Hail             3 SSE Mountain          45.15N 88.45W
07/28/2023  E1.50 inch       Oconto             WI   Public

            Public report of around ping pong ball to
            possibly golf ball sized hail. Time
            estimated based on report and radar.

&&

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Preliminary Local Storm Report
National Weather Service Green Bay WI
851 PM CDT Fri Jul 28 2023

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

0843 PM     Tstm Wnd Gst     Wisconsin Rapids        44.40N 89.84W
07/28/2023  M46 MPH          Wood               WI   ASOS

&&