548
FXUS63 KGRB 111858
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
158 PM CDT Thu Jun 11 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Thunderstorms will bring a risk for 30 to 50 mph winds with
  isolated gusts to 60 mph late this afternoon and evening.

- Heavy rain will bring a potential for flash flooding over much
  of central WI where the ground is saturated. A Flood Watch is in
  effect until 10 PM. Localized flooding could occur elsewhere,
  especially in urban and poor drainage areas.

- Hazardous boating conditions on the bay and lake tonight into early
  Friday morning. High waves and dangerous currents for Lake
  Michigan beaches tonight into early Friday morning.

- A few stronger storms capable of gusty winds and small hail are
  possible Saturday afternoon along a secondary cold front.

&&

.DISCUSSION...
Issued at 158 PM CDT Thu Jun 11 2026

The latest RAP analysis and satellite/radar imagery show a potent
shortwave trough moving east across the northern plains early
this afternoon. At the surface, low pressure is strengthening over
northeast Iowa while last nights cold front remains stalled over
southern Wisconsin. Along this stalled front, the first MCS of the
day has dissipated across southern Wisconsin. Areas across
central Wisconsin were on the northern fringes of this system,
where strong winds behind the complex have developed due to a wake
low feature. These winds have mostly dissipated early this
afternoon. Elsewhere across the country, an unseasonably amplified
pattern is setting up with a building ridge across the West Coast
and an expanding central trough that will dictate regional
weather into early next week.

Thunderstorm and Flood Potential This Afternoon/Evening: The
surface low over Iowa is forecast to track northeast directly
across southwest to northeast Wisconsin through this afternoon and
evening. Strong dynamic forcing accompanies this low, driven by a
potent 40-50 kt low-level jet surging ahead of the system and
into east-central Wisconsin. This setup will likely trigger
another round of strong thunderstorms across the region, with the
most favorable timing window falling between 3 PM and 8 PM. Due to
the intense wind fields just above the surface, even non-severe
showers and storms will have the potential to mix down 30 to 50
mph winds. An isolated damaging wind gust remains possible,
particularly within the stronger storm cores aligned with the low-
level jet from central into northeast Wisconsin. However, the
threat of widespread severe weather has trended further south
today based on the latest CAM guidance and updraft helicity
tracks. The primary forecast uncertainty lies in daytime
instability, as developing east winds this afternoon are expected
to suppress surface-based CAPE. If instability can advect into
the area, a higher severe risk would target areas from Waushara
to Calumet county, and potentially into Waupaca and Outagamie.

Heavy rainfall is the other major concern. Flash flood guidance is
notably low across areas that received 2 to 4 inches of rain
yesterday, where a Flood Watch remains in effect. A quick 1-2
inches of rain will cause localized flooding, and hourly rainfall
rates over an inch could prompt urban flooding. Rain will linger
over north- central Wisconsin through the rest of the evening
before finally exiting overnight.

Friday and Weekend Outlook: Clearing will gradually occur
overnight into Friday morning before convective clouds increase
again in the afternoon. A cooler and drier synoptic pattern will
briefly take hold behind the departing low pressure system as a
broad longwave trough anchors itself from Hudson Bay into the
western Great Lakes. Tightening pressure gradients will foster
breezy conditions on Friday, with west wind gusts up to 30 mph
likely over land. A quick shortwave will bring a renewal of
showers and storms to north-central Wisconsin Friday night.
Saturday stands out as the more active day of the weekend as a
secondary cold front drops south across the state. Boundary layer
moisture and daytime heating will allow instability to moderate to
around 750-1000 J/kg by Saturday afternoon. When combined with a
belt of 30-50 kts winds in the 700-500 mb layer, this environment
will support a few stronger storms capable of producing gusty
winds and small hail, with the highest precipitation chances
focused over central and northeast Wisconsin.

Extended Trends: Behind the secondary weekend cold front, a distinct and
reasonably strong cooling trend takes hold across the upper
Midwest. High temperatures in the low 70s to low 80s through
Saturday will fall back into the mid 60s to mid 70s from Sunday
through Tuesday. The broad upper troughing pattern looks to
flatten and turn more zonal toward midweek. The next appreciable
chance for widespread rainfall is forecast for Tuesday into
Tuesday night as a northern stream shortwave digs into the western
Great Lakes, with yet another quick-moving system potentially
bringing light rain by Wednesday.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1222 PM CDT Thu Jun 11 2026

Flight conditions are expected to deteriorate this afternoon as
low pressure tracks northeast towards the region. Showers and
thunderstorms are forecast to become more widespread, with light
rain already moving into central and north-central Wisconsin. This
are of light rain from cloud bases above 6 kft will continue to
shift east early this afternoon.

Meanwhile, the surface low will bring another round of showers
and thunderstorms to the region from 20-21Z through 01-02Z. Wind
fields becoming increasingly strong aloft with the arrival of the
low level jet (50-60 kts at 850mb) during this time. Even with
the main corridor of severe storms trending south of the area
later today, any showers and storms will be capable of bringing
down wind gusts of 30-50 mph to the surface. The showers and
storms will also bring periods of MVFR and IFR ceilings and
visibilities.

After the precipitation ends in the evening, MVFR to IFR ceilings
will likely persist across north-central WI overnight into Friday
morning. Some improvement to ceilings are expected to begin by
13-15Z.

Lastly, low level wind shear is expected to develop with passage
of the surface low this afternoon into tonight. Gusty west winds
from 20 to 25 kts are expected on Friday.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement from 7 PM CDT this evening through
Friday morning for WIZ022-040-050.

Flood Watch until 10 PM CDT this evening for WIZ030-031-035>037-
045.
&&

$$

DISCUSSION.....MPC
AVIATION.......MPC

NWS GRB Office Area Forecast Discussion