NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 020546
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1246 AM CDT Thu Jul 2 2026

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- A Heat Advisory is in effect until 8 PM today for east-central
  and far northeast Wisconsin, including the lakeshore counties.
  Additional heat headlines may be needed Thursday.

- Chance for severe weather late this afternoon into tonight with
  potential for damaging straight-line wind gusts, large hail, and
  isolated tornadoes. Isolated flash flooding is also possible.

- Additional chances for thunderstorms through the holiday
  weekend.

&&

.DISCUSSION...
Issued at 249 PM CDT Wed Jul 1 2026

Morning and early convection has largely shifted to the east as of
2PM. Expect a lull in thunderstorm activity across the forecast area
over the next 4-6 hours before the next round of thunderstorms
begins to develop and move into central and east-central WI. This
round of thunderstorms is expected to be focused along a nearly
stationary boundary that that extended from near Green Bay back
toward La Crosse and then toward central IA. A mid-level short-wave
is also evident on water-vapor imagery over western IA and southern
MN. As this short-waves moves east it will be overspreading a highly
unstable environment with dew points in the low to middle 70s and
temperatures quickly warming through the 80s. At 500mb the region is
located under the right rear quad of an 80kt jet streak resulting in
0-6 shear of 40-50kts. This creates a favorable parameter space for
strong to severe thunderstorms capable of producing damaging wind
gusts, large hail, and possible tornados. The tornado threat is
conditional on any storms remain discreet for a period this evening.
As storms grow upscale this may transition a damaging wind event
with 60-80mph wind gusts possible. The window for these higher end
severe hazards is 7PM to midnight. 18Z HRRR also shows convection
reinvigorate overnight as a LLJ noises into central and east-central
WI. This round of storms is very conditional on where this evenings
convection shifts the stationary boundary. If storms do develop
there would be a marginal threat for severe winds and hail.

In addition to the multiple rounds of storms this evening and
overnight, there will is a flooding threat given deep warm cloud
depths and PWATs around 2 inches during times of convection. The
flash flood threat is also conditional on training storms as storms
are expected to be moving quickly to the east, especially if they
develop into a bowing complex.

Models indicate additional convection may develop on Thursday,
however this will depend greatly on the evolution of today/tonight's
convection and where outflow boundaries reside. Latest guidance
would suggest convection developing somewhere from central WI to
southern WI during Thursday afternoon, likely along the instability
gradient. If the strong to severe storms end up in our forecast
area, damaging winds would be the main threat.

The next chance for widespread showers and storms appears to be on
Friday with the passage of the first of multiple mid-level
shortwaves throughout the 4th of July holiday weekend. Timing and
intensity of storms related to this short-wave are highly uncertain.
However, one signal that is persistent for Friday in a round of heavy
rainfall across central and east-central WI as the region remains
under a very humid air mass. Additional rounds of thunderstorms are
possible on Saturday and Sunday, however, however, given the
volatile nature of this air mass it predictability with any
details at this time is low. Beyond Sunday global ensembles and ML
models do trend toward a drier period through the first half of
next week.

Heat/Temperatures...Heat Advisory for central and east-central WI
remains in effect until 8 PM this evening as clearing skies are
quickly leading to rapid warming with temperatures in the low to
middle 80s and heat indices in the middle to upper 90s. A few spots
may near 100 degree heat indices again on Thursday, but will again
depend on thunderstorm activity. For Friday through the holiday
weekend, temperatures and dew points look to slightly decrease, but
will continue to monitor the need for additional heat headlines.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1246 AM CDT Thu Jul 2 2026

A cold front sagging southeast through the area tonight, has
touched off an area of showers and thunderstorms. These storms
will linger through the first couple hours of this TAF issuance
(mainly at ATW, GRB, MTW), while gradually weakening as they sag
to the southeast through 08Z/02. Visibility will be reduced in the
heaviest rainfall with a brief lower ceiling around 3kft possible.
Showers will linger for the first couple hours at AUW, CWA before
quickly diminishing, while RHI will remain far enough north of the
front to stay mainly dry. VFR/IFR ceilings may develop overnight
at those locations as well. In fact, the probabilities are around
50-60% that RHI drops below 2kft and closer to 40% at AUW and CWA.
The best chance of seeing visibilities drop to or below 5 miles
will be at RHI. Improving conditions are then expected through the
day Thursday.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 10 AM CDT this morning for WIZ020-030-031-
035>040-045-048>050-074.
&&

$$

DISCUSSION.....GK
AVIATION.......Cooley