661
FXUS63 KGRB 121741
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1241 PM CDT Sun Jul 12 2026

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- A few showers and storms are possible across the north this
  afternoon into this evening. If the storms develop, a few may
  become strong or severe capable of producing damaging wind gusts
  and hail.

- Intense heat is expected Monday and Tuesday with highs in the
  90s with a few locations flirting with the 100 degree mark. Heat
  indices both days will rise into the middle 90s up to 105F
  resulting in heat related impacts.

- There is a chance of thunderstorms at times next Thursday
  through Saturday. It is too early to determine if or when the
  would become severe.

&&

.DISCUSSION...
Issued at 154 AM CDT Sun Jul 12 2026

Skies were mostly clear early this morning with temperatures
in the 60s to lower 70s. Monitoring satellite images for
convection to fire across northern Minnesota and southern province
of Ontario then move southeast towards Upper Michigan towards 12z.
So far, convection has not develop except well north of the border
where there were a few cells. This convection, if it develops,
could clip our far north-central counties between 12z-15z. These
storms are not anticipated to be severe. Attention turns to this
afternoon with convection firing along lake breeze boundary across
Upper Michigan with convection sagging southward into far
northeast WI during the mid to late afternoon, possibly lingering
into the early evening. Convection would be isolated in nature,
but any storms that do form would produce strong/damaging winds
and large hail. Bufkit soundings at Escanaba, MI indicated 1-2
thousand CAPE and 30 knots of shear to support the severe weather
risk.

Attention then turns to intense heat, peaking Monday and Tuesday
with highs in the 90s to around 100F. 925mb/850mb temperatures
support a few 100 degree temperatures across the north with
readings a few degrees lower to the south. Much of the area will
likely reach Heat Advisory criteria (100F) with some locations
across east-central WI possibly flirting with Extreme Heat Warning
(105F) both days. Deeper mixing over north-central WI may not
allow the heat index at some location not to reach 100F.

Ironically, this year is the 90th anniversary of the most intense
heat wave in northeast WI from July 7-14. Many locations set their
all time record high during this period. In the Green Bay
forecast area, the hottest temperature was 112F at Willow
reservoir on the 13th and Hancock on the 14th. The Wisconsin state
record high is 114F at the Wisconsin Dells on the 13th.

Wednesday will be slightly cooler as a weak boundary drops into
the area. Highs will still be in the middle 80s to lower 90s.
Beyond Wednesday, things begin to become unsettled with periodic
chances of thunderstorms Thursday into Saturday. It is too early
to get into specifics about timing or the potential for severe
weather and heavy rainfall.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1240 PM CDT Sun Jul 12 2026

A FEW/SCT cu field developed over north-central and far northeast
WI early this afternoon with cloud bases of 3500 to 4500 ft AGL.
Elsewhere saw clear skies. Anticipate these clouds to dissipate by
this evening leaving clear skies in place through Monday morning.
The only exception is the low potential for a few showers and
storms to sink southward into far northeast WI late this afternoon
into this evening. This could impact KSUE but should stay
northeast or dissipate by the time it reaches KGRB.

West/southwest winds of 5 to 10 kts will continue through tonight,
with gusts to around 15 kts mainly at KRHI through early this
evening. Winds turn westerly Monday morning and increase with
gusts to around 15 kts.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion