895
FXUS63 KGRB 071128
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
628 AM CDT Tue Jul 7 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Shower and storm chances at 20-40% across the Northwoods into
  far northeast WI this afternoon. Wind gusts to 45 mph, small
  hail and brief heavy rain are possible with stronger storms. An
  isolated severe storm can`t be ruled out.

- Upgraded to a Slight Risk (Level 2) of severe thunderstorms on
  Wednesday south of a Wausaukee to Merrill line, while to the
  north there is a Marginal Risk (except much of Vilas County).
  Rain chances are at 70-90%.

- Severe weather hazards on Wednesday include: main risk will be
  strong or damaging winds while large hail and an isolated
  tornado are also possible.

- There is potential for flash flooding on Wednesday as
  thunderstorms gradually sink southward during the afternoon and
  evening. Rainfall rates as high as 1-3" per hour will result in
  urban flooding, rising water levels in ditches, creeks and
  rivers.

- Above normal temperatures are expected over the next week, with
  more intense heat expected early next week. Combined with
  increasing humidity levels, heat-related impacts may be felt.

&&

.DISCUSSION...
Issued at 153 AM CDT Tue Jul 7 2026

A weakening complex of showers and thunderstorms was moving into
west-central and northwest WI early this morning. This complex is
expected to weaken and dissipate as it move further east this
morning. Could not rule out a few light showers over north-central
WI. Otherwise, a warm summer day is expected with highs mainly
in the 80s. This will result in scattered convection developing
across north-central and far northeast WI this afternoon. Brief
heavy rain, gusty winds to 45 mph and small hail will be possible
with any stronger storms. Could not completely rule out an
isolated severe storm. Bufkit soundings at Rhinelander indicated
CAPE values of 1,000-1,500 J/KG however shear values around 20
knots.

Attention then turns to tonight and Wednesday. Any lingering
convection from this afternoon should end around mid-evening.
Focus later tonight will be on a weak cold front sagging southward
into northern Wisconsin with another round of convection late
tonight into Wednesday morning across the north. The SPC Day 1
Outlook has the Marginal Risk of severe storms almost to the
Oneida County line late tonight. Expected scattered convection
to break across north-central WI shortly after 06z, with
widespread convection across north-central WI by 12z Wednesday.

The latest Storm Prediction Center Day 2 Outlook has upgraded
portions of the forecast area into a Slight Risk, generally south
of a Wausaukee to Merrill line with a Marginal Risk to the north
(except for most of Vilas County). With ongoing convection across
the north during the morning, will need to watch for outflow
boundaries that push the convection south quicker than what some
of the models would indicate. The Green Bay bufkit soundings ahead
of the storms indicated around 1,500 J/KG of CAPE and 0-6km shear
values around 30 knots to support strong or severe storms. Storms
that interact with any outflow boundaries will have the potential
for producing a brief tornado. The other big concern will be the
potential for heavy rain and localized flooding. We are in a
Slight Risk of Excessive Rainfall on Wednesday. Bufkit soundings
indicated a precipitable water value of 2.1 inches which would be
near record levels for the date. Showers and storms will
gradually end across the north and taper off to scattered showers
across central and east-central WI late Wednesday night. For
Thursday, daytime heat will trigger addtioanl convection across
central into northeast WI.

After Thursday, fairly quiet conditions are expected Friday through
the weekend. Building heat and humidity will be the concern early
next week with highs well into the 80s and lower 90s for several
days, which will lead to heat related impacts. Current forecast is
a little cooler than the MEX Guidance values, so highs may be
bumped up in the coming days.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 622 AM CDT Tue Jul 7 2026

Cumulus field between three and five thousand feet will develop
later this morning into the afternoon. Scattered showers and
storms are expected the north during the afternoon into the
evening across northern and far northeast WI. South to southwest
winds of 5 to 10 knots should prevail. Attention then turns to
late tonight into Wednesday. A complex of storms is expected to
move into north- central WI late tonight and continue Wednesday
morning. Have a tempo group for thunder at KRHI/KAUW/KCWA between
09z-12z. Thunderstorms will continue through Wednesday into
Wednesday evening. Strong or severe storms could impact aviation
operations at times. Main risk would be strong wind gusts to 50
knots or greater and torrential rainfall that could reduce
visibilities at times below one mile in heavy rain.CIGS could drop
into the MVFR category or lower across the north after 12z
Wednesday.

&&

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

&&

$$

DISCUSSION.....Eckberg
AVIATION.......Eckberg

NWS GRB Office Area Forecast Discussion