NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 212340
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
640 PM CDT Sat Jun 21 2025

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Multiple days of dangerous heat are forecast through Monday.
  Heat index values reach 95 to 105 degrees, peaking on Sunday.
  Heat indexes on Monday will be highest over east-central WI
  Tuesday.

- The chances of thunderstorms will continue at times next week.
  Strong or severe storms are possible Monday into Monday night
  with damaging winds and large hail. It is too early to determine
  the risk of severe weather after Monday.

&&

.DISCUSSION...
Issued at 207 PM CDT Sat Jun 21 2025

Main forecast concerns involve heat for this weekend into Monday
followed by a round of stronger weather and the transition to a
more active pattern over the next week.

Heat...
As southwesterly flow continues today through Sunday a surge of
warmer and very humid air will be in place across the region. High
temperatures in the 90s along with dewpoints in the 70s will bring
heat indices into the 100-105 degree range during the afternoon.
Nighttime lows also remain quite warm, staying in the upper 70s to
lower 80s both tonight and Sunday night. With the prolonged heat
and no relief overnight, heat will be a major concern for anyone
unprepared or staying extended periods outdoors. A Heat Advisory
remains in place for all of the region except for Door County,
which may see some slightly lower temperatures thanks to the
influence of Lake Michigan. Eventually, could see the end of the
advisory to be trimmed over the north on Monday as cold front and
convection chances keep max heat index values lower there.

Severe Weather Potential Monday...
As the ridge shifts eastwards Monday a cold front will move into
the region which will bring a round of active weather. This
remains the best chance for strong to severe weather in the
upcoming work week, with MLCAPE generally still ranging in the
1000-2000 J/kg. Better shear still remains lagged behind the
front, which would favor more of a pulse storm environment than
more organized storms. Monday remains in the Slight Risk Category.

Active Weather Rest of the Week...
The front mentioned above will largely stall out over the Upper
Midwest, bringing both a relief to the heat but also several
periods of active weather, with periods of on and off active
weather expected through much of Tuesday- Thursday. The ridge
just to our east will allow for ample Gulf moisture to reach the
region, as indicated by PWATs still pushing into the 90th
percentile for much of the week. As a result, expect multiple
periods of active weather and the potential for any thunder to
also carry with it heavy rainfall. The perhaps best defined
feature and timing for the week will be sometime Thursday night
Friday as an upper shortwave moves across the Central Plains and
helps to better organize the active weather. Finally, there are
some hints that a drier pattern may develop over next weekend into
next week, but this is a ways out yet.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 640 PM CDT Sat Jun 21 2025

A field of fair weather VFR cumulus will continue north of
highway 29 through the early evening. Clear skies are expected to
return overnight through Sunday morning.

Winds will pose a concern through the TAF period, with gusts up
to 30 knots at times through the early evening. As surface winds
decouple overnight, a period of LLWS is expected across the region
before gusty winds return on Sunday.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 7 PM CDT Monday for WIZ005-010>013-018>021-
030-031-035>040-045-048>050-073-074.

Beach Hazards Statement through Monday evening for WIZ022-040-
050.
&&

$$

DISCUSSION.....Uhlmann
AVIATION.......Kurimski