624
FXUS63 KGRB 132334
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
634 PM CDT Sat Jun 13 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Marginal (level 1/5) risk for isolated strong or severe storms
  over east-central Wisconsin this afternoon. Wind and hail would
  be the primary concerns, though trends show most areas remaining
  dry.

- Gusty west winds up to 25 kts will result in conditions
  hazardous to small craft along the Lake Michigan shoreline
  through this afternoon.

- Cool and showery pattern to take hold over the course of the
  next week. Temperatures to run around 5 to 10 degrees below
  normal.

&&

.DISCUSSION...
Issued at 1035 AM CDT Sat Jun 13 2026

This afternoon... CAMs remain unimpressed with storm potential,
let alone severe weather potential, for this afternoon as guidance
shows better convergence along the front off to our south. This
being said, modest instability (500 to 1,000 J/kg MUCAPE) continues
to build under mostly clear skies, which may be sufficient for
convective initiation over east-central Wisconsin within the next
hour or two. If a stronger storm were to develop, steepening lapse
rates, elongated hodographs, and 40+ knots of bulk shear would
support gusty winds and hail as the primary concerns. Window for
any stronger storms remains tight, with 20 to 30% PoPs going until
around 5 PM. Lack of upper support should prevent any storm
organization. All of this to say, odds are looking better for most
areas remaining dry throughout the afternoon.

Extended... Pattern shift to cooler and more showery takes place
over the course of the next week as closed upper low sitting and
spinning over the Hudson Bay puts us under northwesterly flow
regime. Result will be temperatures running around 5 to 10 degrees
below normal, with highs reading mainly in the upper 60s to mid
70s.

Several chances for showers then exist throughout the week as
multiple shortwaves migrate through the base of a broader longwave
trough. The first of these chances arrives in the vicinity of a
surface low Monday into Tuesday, though better chances for more
widespread rain will be Wednesday into Thursday as PWATs increase
into the 1 to 1.25" range. It is still too soon to explicitly
determine severe weather potential during this time, though a
cursory glance shows instability to be fairly weak.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 633 PM CDT Sat Jun 13 2026

Primarily VFR conditions are forecast through the TAF periods, with
the exceptions being a period of possible MVFR status across
northern and central WI Sunday morning.

A surface frontal boundary has pushed south across the region this
afternoon and currently snakes from KMTW southwest to KDBQ. North of
the boundary low and mid level northwesterly flow has lead to the
development of stratocumulus based around 4.5-6 kft across northern
WI. As the northwesterly flow continues overnight expect these low
end VFR cigs to overspread the entire region. Cigs across central
and northern WI are expected to descend to around 2.5-3 kft (MVFR)
between 07-12Z. These lower cigs should start to rise and scatter
out as much drier air pushes into the region mid Sunday morning.

Northwest winds will become breezy again Sunday with gusts
increasing to 18-20kts after 14-16Z.

&&

.MARINE...
Issued at 1035 AM CDT Sat Jun 13 2026

Post-frontal winds continue to ramp up and veer to northwesterly
early this afternoon. As such, gusts to 25 knots will be possible
along the Lake Michigan shoreline through this evening, though
waves should be held down to generally 1 to 3 ft. Have opted to
hold onto the Small Craft Advisory, though marginal, due to warm
weather and weekend status. The Advisory remains in effect until 5
PM today.

&&

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

&&

$$

DISCUSSION.....Goodin
AVIATION.......GK
MARINE.........Goodin

NWS GRB Office Area Forecast Discussion