Green Bay, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

005
FXUS63 KGRB 152100
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
Issued by National Weather Service Milwaukee/Sullivan WI
400 PM CDT Thu May 15 2025

.KEY MESSAGES...

- Marine Dense Fog Advisory for the nearshore areas of Lake
  Michigan through the early evening. A Small Craft Advisory

- A broken line of strong thunderstorms will cross northern WI
  between 4 and 9 PM today. Some severe storms are likely with
  the passage of a cold front. All hazards possible over central
  WI and large hail possible over eastern WI.

- Another period of showers and weak storms expected Friday with
  some potential for gusty winds with some of these
  showers/storms.

&&

.DISCUSSION...
Issued at 304 PM CDT Thu May 15 2025

The Rest of this Afternoon through Friday Night:

A broken line of cellular storms has broken out, currently from
Eau Claire down to Madison WI. This is line is expected to
develop further and ramp up in intensity this evening. Hail and
gusty winds are expected, owing to SBCAPE around 2500 J/kg amid
effective shear around 40 knots. A couple tornadoes also look
possible, given effective SRH values around 200 m2/s2 over much
of NE WI, and an effective warm front parked from the Fox
Valley up through Marathon and Lincoln County. The peak timing
for storms looks to be from 5pm through 8pm this evening as the
broken line moves northeast. A Tornado Watch is out from now
through 10pm over much of our CWA.

Storms will quickly move through and a dry punch aloft will
clear out skies fairly quickly behind the storms. There will be
a bit of a lull overnight, but tomorrow, enhanced mixing will
lead to gusty southwest winds with some scattered gusts to 40
mph. A secondary shortwave pivoting around an upper level low
and lingering moisture will squeeze out some more scattered
thunderstorm activity in the afternoon. Very dry low levels and
the high based nature of the storms will cause the potential for
gusty winds with any storms that get established enough in the
environment.

Saturday through Wednesday

The upper low will linger into Saturday. Cooler conditions are
expected due to clouds and the cooler air aloft and highs will
top out in the low to mid 60. Diurnally driven scattered
showers may occur through the day. This upper low should move
east on Sunday, restoring relative high pressure, but clouds
will likely linger along with cooler temperatures as winds will
come around to northeasterly. By late in the extended period, a
large low pressure system is expected to approach the upper
Midwest Monday into Tuesday, bringing a prolonged period of
showery rain and clouds to the area. Winds will remain
northeasterly off of the lake, keeping our CWA cool with highs
in the 50s.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 304 PM CDT Thu May 15 2025

Current conditions still largely remain VFR across the CWA with
SCT to CLR conditions most everywhere save for areas from west
of KGRB to KCWA where BKN040 is largely present. A line of
storms currently present, arching from KMSN to KMSP, and this
line should continue to develop and move northeast between now
and 03z this evening. These storms will feature gusty winds, and
large hail. Following storms, skies are expected to remain
clear overnight as a dry slot moves in, with mostly clear winds.

VFR ceilings return tomorrow afternoon with sfc wind gusts
becoming strong out of the southwest to 35 knots in spots. There
may be additional scattered thunderstorm development in the
afternoon with gusty winds being the primary threat.


&&

.MARINE...
Issued at 304 PM CDT Thu May 15 2025

Marine dense fog will continue into this evening until
thunderstorms and a front pass during the early evening hours. A
small craft advisory will also continue into tonight on
southeast winds. Following the passage of the front, winds
should ease for a time overnight and then come around to
southwesterly by tomorrow at dawn. Gusty southwesterly winds are
then expected to pick up leading to a potential second period of
Small Craft Advisory conditions during tomorrow afternoon.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WI...None.
MARINE...Dense Fog Advisory until 7 PM CDT this evening for LMZ521-522-
     541>543.
     Small Craft Advisory until 1 AM CDT Friday for LMZ522.
     Small Craft Advisory until 11 PM CDT this evening for LMZ542-
     543.

&&

$$

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