275
FXUS63 KGRB 101802
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
102 PM CDT Wed Jun 10 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Severe storms are expected this afternoon and evening (2-7 PM),
  bringing damaging winds, large hail, and a brief tornado threat
  to central, parts of north-central, and east-central Wisconsin.

- Another round of severe weather is possible Thursday afternoon
  and evening, mainly over east-central Wisconsin.

- Heavy rain is an increasing hazard through Thursday. Localized
  flooding is expected where heavy rain occurs.

- Dense fog will continue to pose a hazard to mariners along the
  Lake Michigan shoreline.

- Cooler, drier air arrives for the weekend, with intermittent
  rain chances through Tuesday.

&&

.DISCUSSION...
Issued at 102 PM CDT Wed Jun 10 2026

The latest RAP analysis and satellite/radar imagery show a potent
northern Plains trough is lifting northeast into south-central
Canada, pushing a cold front east across western Minnesota. An
effective warm front extends from near Minneapolis to Fond Du Lac
early this afternoon, establishing a volatile and highly unstable
warm sector across southern Wisconsin. Even further south, an
shortwave impulse and associated convection over Iowa and
southeast Minnesota is primed to track northeastward, providing
large- scale ascent later today.

Severe Thunderstorm Potential This Afternoon/Evening: Destabilization
is expected this afternoon as this mornings thunderstorm activity
has exited. Extremely strong instability resides south of the
warm front, where surface- based CAPE values are ramping into the
3000-4000 J/kg range, driven by surface temperatures warming into
the middle 80s and dewpoints pooling into the middle 70s. Steep
mid- level lapse rates of 7-8 C/km and downdraft CAPE in excess of
1000 J/kg point to a volatile airmass highly favorable for severe
weather. As a shortwave impulse tracking out of Iowa provides
deep layer forcing, storms are expected to gradually intensify as
they shift northeastward between 3 PM and 8 PM. Convective
evolution carries some uncertainty, as high- resolution guidance
splits between a consolidated cold pool bowing system and discrete
clusters or broken line segments. Damaging wind gusts and large
hail are the primary threats. However, an isolated tornado threat
cannot be ruled out near the effective warm front across central
to east- central Wisconsin where low- level flow is locally
backed. The greatest severe threat is expected south of a
Rhinelander to Manitowoc line where a Severe Thunderstorm Watch is
in effect.

Some CAMS indicate develop additional thunderstorms along the cold
front due to move across the region late this evening. While
expectation is that the atmosphere will be worked over thereby
limiting buoyancy potential, an isolated strong storm will be
possible. The threat of storms will diminish by early overnight.

Thursday Severe Potential: The main surface cold front will
settle downstate overnight. After a lull Thursday morning, a very
dynamic shortwave trough will drive a surface low pressure system
northeastward across the region Thursday afternoon into early
Thursday evening. Model spread remains rather large regarding the
exact track of the surface low, leading to below normal forecast
confidence. The general consensus navigates the surface low
across east-central Wisconsin late Thursday afternoon. Areas south
of this track will possess the highest severe weather threat.
Instability will be substantially lower than today, maxing out
near 1000 J/kg, but wind fields will be considerably stronger.
Given the robust wind fields aloft, significant instability will
not be required, just sufficient for severe weather. Damaging
winds and an isolated tornado will be possible from the lows
triple point southward, placing east-central Wisconsin at the
greatest risk for severe weather. Sfc highs will range from the
mid 70s to low 80s.

Friday Wind and Marine Impacts: A cooler and drier weather
pattern returns on Friday in the wake of the departing surface
low as a longwave trough establishes itself from Hudson Bay into
the western Great Lakes. A tight pressure gradient on the southern
periphery of the trough will foster breezy conditions across the
entire area. Sfc wind gusts of 30 to 35 mph are expected over
land, and these strong winds will likely necessitate a Small Craft
Advisory across the nearshore waters of Lake Michigan and Green
Bay due to building waves.

Weekend and Extended Outlook: Spotty showers and storms will
linger over north-central Wisconsin Thursday night behind the main
surface low, but dry conditions return for most locations by
Friday morning. Saturday looks to be the more active day of the
weekend as a secondary cold front drops south. Instability will
moderate to around 500-700 J/kg by Saturday afternoon, which when
combined with mid-level wind fields of 30-50 kts, will support a
few storms capable of gusty winds. Behind this second front, a
distinct cooling trend takes hold. 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 next appreciable chance for
widespread rainfall will arrive on Tuesday as a northern stream
shortwave digs into the western Great Lakes.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1235 PM CDT Wed Jun 10 2026

Main forecast challenges are timing additional rounds of convection
this afternoon and evening as well as low clouds/fog preceding and
following. Most favorable timing for thunderstorms appears to be in
the 21-02Z timeframe. Any storms are capable of winds to 60 mph and
large hail, as well as frequent lightning. Prior to the storms,
stubborn IFR clouds at the beginning of the TAF should scatter out
quickly, except likely lingering into mid-afternoon at MTW. Tonight,
lower clouds and fog may redevelop, but confidence is low on flight
categories and duration. Maintained MVFR cigs/fog for now. Expect
these to dissipate after sunrise on Thursday.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement through Thursday morning for WIZ022-040-
050.
&&

$$

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

NWS GRB Office Area Forecast Discussion