Severe Thunderstorm Warning 26, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
1249 PM CDT Fri May 16 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Gusty southwest winds are expected today with highest gusts up
  to 40 mph, primarily between Fox Valley and Lake Michigan.

- Scattered showers and thunderstorms are expected this
  afternoon. Damaging wind gusts and small hail may be possible
  with any stronger storms.

&&

.DISCUSSION...
Issued at 1205 AM CDT Fri May 16 2025

A warm and windy day is in store for today. The low will be
over northwest MN at 7AM this morning and should make it to
Duluth around 7PM. A lobe of vorticity is expected to swing up
from IA through eastern WI during the day. Vorticity advection
and also upper divergence from the left exit region of an upper
jet will provide synoptic forcing to allow for showers and
storms.

Forecast soundings show very steep low and mid level lapse
rates during the afternoon, with 500 to 1000 j/kg CAPE. Some
models show a weak cap while others try to mix us all the way up
to 10kft. The winds through the profile are very strong with SW
winds up to 43kt at 5kft and 50 to 60kt at 10kft. There will
probably be a weak cap that will help keep our wind gusts in
check today, but a few gusts over 39kt (wind advisory criteria)
are not out of the question. If gusts begin to over-achieve by
noon today, we will know we need a wind advy for the afternoon.

Despite the weak cap, the overall synoptic forcing should be
enough for scattered thunderstorm development. The CAPE values
and low freezing level of 9 or 10kft support the chance for
small hail, with a report of two of 1 inch hail possible. There
is strong shear. The main threat for any stronger storms that
develop is the damaging wind potential, since the strong winds
aloft will efficiently mix down with momentum transfer.

As the upper low tracks across MN today, another frontal
boundary will push into north central and eastern WI. This will
feature cooler temperatures, low clouds, and rain or drizzle.
Northern WI will be fully engulfed in these damp, brisk
conditions Friday night.

Saturday, expect breaks in the clouds as the upper low starts to
exit the region. With steep low level lapse rates and lingering
low level moisture, scattered showers are expected, although
coverage is still uncertain. In addition, expect gusty west
winds up to 30 mph during peak daytime heating/mixing. Saturday
highs will range from the upper 50s north central to the mid 60s
east.

MRC

Saturday night through next Thursday

Upper trough exits across the eastern Great Lakes Saturday night with
ridging aloft beginning to build from the plains into the western Great
Lakes. Surface high pressure over Manitoba and northern Ontario will ridge
into MN and WI Saturday night with more influence of ridging by Sunday night.
The ridge will bring dry weather and also the risk of frost Saturday night
and/or Sunday night. PWATs lower Sunday night, but with high more off to the
north than the east, the area will keep some wind in lowest 1kft with tighter
pressure gradient on southern edge of high. It still appears that temps could
drop into the mid 30s north Saturday night and/or Sunday night. NBM probabilities
of min temps less than 35 are 30 to 40 percent Saturday night over Vilas County,
but increase and expand to 40-80 percent Sunday night north of highway 29. If and
where winds become light, some frost could occur either of these nights, though
Sunday night looks more favorable at this point.

Troughing over the western CONUS late this weekend shifts east early next
week, bringing the next chance of showers and storms to the area Monday night
into Tuesday. One trend that seems to be emerging though is the dry east flow
out of the high to the north may restrict chances of rain only to the southern
part of the forecast area on into southern WI. Risk of any stronger storms also
is well to the south of the area. Given these trends, its feasible that much of
northern WI could stay dry early this week.  Whatever chances of rain occur will
shift south and east of the western Great Lakes Wed into Thu as broad 850-700mb
low shifts across lower Great Lakes. Cool flow in wake of the low flowing across
the region could lead to more clouds and a small chance of spotty showers by
Thursday. Overall a cooler than normal stretch is expected for the coming week
with highs in the upper 50s to mid 60s.

JLA.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1249 PM CDT Fri May 16 2025

Mostly clear skies and VFR conditions were observed for most
early this afternoon; however, satellite imagery shows mid-clouds
starting to enter central WI. The main feature was the winds with
SSW gusts to around 30 kts.

Scattered showers and thunderstorms are likely to develop this
afternoon, but exact location is difficult to pinpoint. Coverage
will not be as widespread as yesterday, but the chance (30-45%)
exists everywhere. Main time window is 20Z-24Z. Included TEMPO
groups to account for this. Precip chances will be minimal the
rest of the evening into Saturday morning. A few spotty showers
are possible, but coverage/confidence was too low to include in
TAFs this issuance.

Cloud bases will lower late this evening with a mix of MVFR/IFR
cigs tonight (approx. 06Z) through Saturday morning. Winds will
also increase again and peak late Saturday morning through the
afternoon with gusts up to 30 kts.

&&

.MARINE...
Issued at 1205 AM CDT Fri May 16 2025

Gusty south-southwest winds are expected today, highest over
land. Cooler lake water should keep wind gusts below gale
force, so a Small Craft Advisory goes into effect mid morning.
We initially set the end time of 7PM this evening, but after a
brief lull in the winds tonight, gusty westerly winds will
develop. Therefore, we extended the end time all the way until
7PM Saturday.

MRC.

&&

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

&&

DISCUSSION.....
AVIATION.......KLJ
MARINE.........

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Special Weather Statement
National Weather Service GREEN BAY WI
Issued by National Weather Service Milwaukee/Sullivan WI
201 PM CDT Fri May 16 2025

WIZ019-020-031-037-161930-
Waupaca WI-Shawano WI-Langlade WI-Menominee WI-
201 PM CDT Fri May 16 2025

...A STRONG THUNDERSTORM WILL IMPACT WESTERN MENOMINEE...NORTH
CENTRAL WAUPACA...SOUTH CENTRAL LANGLADE AND WESTERN SHAWANO COUNTIES
THROUGH 230 PM CDT...

At 201 PM CDT, Doppler radar was tracking a strong thunderstorm near
Wittenberg, or 23 miles south of Antigo, moving northeast at 40 mph.

HAZARD...Wind gusts of 50 to 55 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.

Locations impacted include...
Wittenberg, Big Smokey Falls, Neopit, Marion, Pella, Tigerton,
Gresham, Mattoon, Bowler, Shepley, Lake Noseum, Split Rock,
Lyndhurst, Phlox, Upper Bass Lake, Zoar, Caroline, Whitcomb, Tilleda,
and Leopolis.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4469 8922 4514 8903 4507 8860 4463 8886
TIME...MOT...LOC 1901Z 214DEG 33KT 4480 8907

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...55 MPH

BOXELL

Special Weather Statement
National Weather Service GREEN BAY WI
Issued by National Weather Service Milwaukee/Sullivan WI
229 PM CDT Fri May 16 2025

WIZ022-040-162000-
Kewaunee WI-Door WI-
229 PM CDT Fri May 16 2025

...A STRONG THUNDERSTORM WILL IMPACT NORTHERN KEWAUNEE AND
SOUTHWESTERN DOOR COUNTIES THROUGH 300 PM CDT...

At 229 PM CDT, Doppler radar was tracking a strong thunderstorm near
Algoma, or 12 miles north of Kewaunee, moving northeast at 55 mph.

HAZARD...Wind gusts of 50 to 55 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.

Locations impacted include...
Sturgeon Bay, Algoma, Forestville, Clay Banks, Lincoln, Valmy,
Gregorville, Rankin, Euren, Rosiere, Carlsville, Rio Creek, Vignes,
Maplewood, Institute, Potawatomi State Park, Kodan, Alaska, Whitefish
Dunes State Park, and Kolberg.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4491 8722 4487 8721 4484 8727 4479 8732
      4470 8735 4460 8744 4452 8748 4460 8769
      4487 8751 4486 8750 4488 8745 4488 8743
      4489 8743 4484 8739 4489 8738 4491 8740
      4500 8735 4493 8718
TIME...MOT...LOC 1929Z 213DEG 49KT 4463 8754

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...55 MPH

BOXELL

Special Weather Statement
National Weather Service GREEN BAY WI
Issued by National Weather Service Milwaukee/Sullivan WI
233 PM CDT Fri May 16 2025

WIZ019>021-030-031-036>038-074-162000-
Southern Oconto County WI-Waupaca WI-Shawano WI-Langlade WI-
Outagamie WI-Northern Oconto County WI-Marathon WI-Portage WI-
Menominee WI-
233 PM CDT Fri May 16 2025

...STRONG THUNDERSTORMS WILL IMPACT NORTHEASTERN PORTAGE...
SOUTHEASTERN MARATHON...MENOMINEE...WAUPACA...WEST CENTRAL OCONTO...
NORTHWESTERN OUTAGAMIE...SOUTH CENTRAL LANGLADE AND SHAWANO COUNTIES
THROUGH 300 PM CDT...

At 232 PM CDT, trained weather spotters reported a cluster of strong
thunderstorms along a line extending from near Bevent to near
Clintonville. Movement was northeast at 55 mph.

HAZARD...Wind gusts of 50 to 55 mph and pea size hail.

SOURCE...Trained weather spotters.  There have been multiple reports
         of wind gusts around 50 MPH.  Blowing dust is also causing
         reduced visibilities in some areas.

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

Locations impacted include...
Stevens Point, Shawano, Clintonville, Gillett, Bevent, Wittenberg,
Amherst, Embarrass, Big Smokey Falls, South Branch, Legend Lake,
Keshena, Neopit, Stockton, Belle Plaine, Bonduel, Royalton, Red
River, Manawa, and Iola.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4508 8914 4503 8816 4434 8891 4455 8969
TIME...MOT...LOC 1932Z 218DEG 46KT 4478 8934 4467 8883

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...55 MPH

BOXELL