Severe Thunderstorm Warning 14, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
812 PM CDT Mon Apr 28 2025

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Multiple rounds of thunderstorms are expected late this
  afternoon through tonight. A significant severe weather outbreak
  is possible this evening into the early overnight hours. Most
  of the forecast area has an Enhanced Risk of severe
  thunderstorms, with parts of central WI in a Moderate Risk.

- Thunderstorm chances are lower during the late afternoon.
  However, any storms that do develop could quickly become severe,
  with tornadoes, damaging winds and large hail all possible.
  Confidence in the details is lowest for this round of storms.

- The final round of storms is forecast to impact the area this
  evening into the early overnight hours. Confidence is higher
  that a line of storms will impact the area, with potential for
  widespread damaging winds and embedded tornadoes.

&&

.DISCUSSION...
Issued at 233 PM CDT Mon Apr 28 2025

Short Term...Tonight and Tuesday

Scattered elevated convection has develop across central WI this
afternoon as mid-level lapse rates have steepened. Radar returns
are indicating some non-severe hail is occurring with in these
storms. Expect these pulse-type storms to grow in coverage over the
next few hours, however, the likelihood that any cells become severe
is low, as the greatest SBCAPE values remain along and west of the 1-
35 corridor in central MN and RAP analysis soundings still show a
strong cap around 850mb.

CAMs continue to show the best window for severe thunderstorm
initiation between 00-02Z as the cap erodes. Strong moisture
advection will create a much more unstable atmosphere as a warm
front currently draped across southwest WI moves north and east.
Initially discrete supercells will be possible across central WI as
storms initiate. SBCAPES increasing to 100-1500 J/kg along with
strong low-level (0-1km) shear 30-35kts (SRH 290 m2/s2) does point
to a potential tornado threat with any storms that do develop. Steep
mid-level lapse rates also bring severe hail, up to 2" into play
with the strongest storms. As the event progresses and a cold front
starts to push into the western part of the forecast area storms are
forecast to grow upscale into a QLCS. As this occurs damaging severe
winds gusts along with embedded tornados will become possible. If an
organized QLCS is able to develop it will likely remain severe as it
moves east across the region, however, storm intensity may start to
weaken as they approach Lake Michigan. The severe weather threat is
expected to end around or just after midnight.

Behind the cold front there may be some lingering thunderstorms
Tuesday morning, but the risk for any severe storms at that time
will be low. Winds behind the front also look gusty for Tuesday with
peak gusts reaching 30-40 mph.

Long Term...Tuesday Night Through Monday

Tuesday-Monday:

Cooler conditions are expected on Tuesday in the wake of the surface
cold front as Canadian high pressure builds into the area.
Instability quickly wanes as drier air works in, but a few showers
remain possible as a mid-level shortwave trough swings through.

Otherwise, broad troughing will overspread the area later in the
week as northern/stream shortwave troughs transect the central US.
Although details of this system are somewhat unclear, rain chances
increase by Thursday (40-80%), with chances lingering into Friday.
Trends favor the area being on the cooler side of this system,
keeping any severe weather potential farther south.

The pattern looks to trend drier heading into the weekend as mid-
level ridging builds across the central US downstream from large
scale trough development across the western US. Trends favor a
return to above average temps in this regime.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 812 PM CDT Mon Apr 28 2025

Main focus will be showers and storms, some strong to severe,
pushing across the area through the late evening. Expect activity
to continue to pop up ahead of the main line, then the line of
storms will cross the area mainly between 02-06z. Overall, the
storms have been struggling to our west, but some better
organization is still possible in the next couple/three hours
then a weakening trend is expected as it pushes towards far eastern
WI. The strongest storms may be capable of producing strong winds
gusts over 40kts, hail over 1", and a tornado. Intense downpours
may also drop vsbys to MVFR/IFR at times.

South/southwest surface winds will continue to gust ahead of the
line, with winds shifting to the west then northwest on Tuesday.
The northwest winds could gust up to ~40 kts for a time Tuesday
morning, before diminishing in the late morning and afternoon.
LLWS is expected to continue across much of the area through late
tonight, due to a low-level jet of 50 to 55 kts.

&&

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

&&

DISCUSSION.....GK/JM
AVIATION.......Bersch

Special Weather Statement
National Weather Service Green Bay WI
837 PM CDT Mon Apr 28 2025

WIZ010>012-290215-
Florence WI-Oneida WI-Forest WI-
837 PM CDT Mon Apr 28 2025

...A STRONG THUNDERSTORM WILL IMPACT NORTHERN FOREST...FLORENCE AND
SOUTHEASTERN ONEIDA COUNTIES THROUGH 915 PM CDT...

At 836 PM CDT, Doppler radar was tracking a strong thunderstorm 7
miles northwest of North Otter Creek Natural Area, or 9 miles north
of Crandon, moving northeast at 70 mph. Numerous other strong storms
extended from southeast Oneida County to Florence County.

HAZARD...Wind gusts up to 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

This strong thunderstorm will be near...
  Popple River around 840 PM CDT.
  Whisker Lake Wilderness around 855 PM CDT.
  Florence around 905 PM CDT.

Other locations impacted by this storm include Gagen, Popple River
Headwaters Natural Area, Bastile Lake Natural Area, Lasalle Falls,
Spread Eagle, Starks, Pelican Lake, Nashville, Argonne, and Lennox.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm 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.

A Tornado Watch remains in effect until 200 AM CDT for north central
and northeastern Wisconsin.

&&

LAT...LON 4602 8851 4599 8849 4600 8846 4598 8842
      4599 8838 4596 8833 4596 8832 4595 8829
      4596 8825 4595 8824 4595 8819 4592 8810
      4588 8810 4587 8807 4584 8811 4547 8909
      4549 8943 4553 8943 4602 8853
TIME...MOT...LOC 0136Z 234DEG 61KT 4570 8886

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

Kieckbusch

Special Weather Statement
National Weather Service Green Bay WI
842 PM CDT Mon Apr 28 2025

WIZ013-019>021-073-290215-
Southern Marinette County WI-Langlade WI-Northern Oconto County WI-
Menominee WI-Northern Marinette County WI-
842 PM CDT Mon Apr 28 2025

...A STRONG THUNDERSTORM WILL IMPACT CENTRAL MARINETTE...NORTH
CENTRAL MENOMINEE...NORTHERN OCONTO AND EAST CENTRAL LANGLADE
COUNTIES THROUGH 915 PM CDT...

At 841 PM CDT, Doppler radar was tracking a strong thunderstorm near
Gardner Dam Scout Camp, or 23 miles east of Antigo, moving northeast
at 65 mph.

HAZARD...Wind gusts up to 30 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

This storm will remain over mainly rural areas of central Marinette,
north central Menominee, northern Oconto and east central Langlade
Counties, including the following locations... Boot Lake Campground,
Townsend, Caldron Falls Rese, Caldron Falls Reservoir, Mcclintock
County Park, Governor Thompson State Park, Boulder Lake Campground,
Silver Cliff, Crooked Lake, and Langlade.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

A Tornado Watch remains in effect until 200 AM CDT for north central
and northeastern Wisconsin.

&&

LAT...LON 4537 8815 4502 8871 4519 8883 4538 8854
      4538 8843 4545 8842 4552 8832
TIME...MOT...LOC 0141Z 229DEG 55KT 4519 8869

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...30 MPH

MPC

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