474
FXUS63 KGRB 110759
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
259 AM CDT Thu Jun 11 2026

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Strong to severe storms possible this afternoon and evening,
  especially Fox Valley to lakeshore. Main hazards are damaging
  winds and large hail. Enhanced risk for severe storms southern
  Fox Valley to the lakeshore.

- Heavy rain this afternoon may result in flash flooding for
  portions of central WI where the ground is saturated due to
  multiple rounds of heavy rain that occurred on Wednesday. A
  Flood Watch is in effect for portions of central WI from Noon
  to 10p. 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.

&&

.DISCUSSION...
Issued at 258 AM CDT Thu Jun 11 2026

Severe potential this afternoon through This Evening... Cold
front slowly making its way over WI this morning. Low pressure
that will ride along this front will be main focus for next round
of strong to severe storms this afternoon into this evening in the
form of a strong MCS that is expected to develop early this
morning eastern NE/western IA. Good agreement on where low is
through this morning, then significant differences develop on how
far north the low tracks this afternoon. Along and south of the
low, rapid increase in instability will fuel severe storms, again
potentially in the form of an MCS. Using max of HREF sfc based CAPE,
the CAPE gradient reaches into southern third of WI where it
coincides with effective shear 40-60 kts by late afternoon. Thus,
there is decent agreement in HREF members and perusal of medium
range model output that southern and southeast portions of the
area (Waushara County east-northeast into the southern Fox Valley
and to the lakeshore) could be clipped by the potential MCS (also
shown by orientation of 850-300mb thickness lines). This same
area is also impacted by higher updraft helicities (UH) late this
afternoon which may also signal development of additional
supercell thunderstorms as the main sfc low arrives, perhaps
helped by outflow from earlier activity. Primary severe hazards
would be damaging winds and large hail as greatest tornado threat
would likely remain south along the sharpest gradient of sfc based
CAPE. No big qualms with the SPC enhanced risk clipping
southeast, with Slight risk from Waupaca to north of Green Bay.
Approximate window for severe weather is as early as 1pm (northern
end of MCS) through 10pm (last of departing convection with sfc
low moving through).

Heavy rain potential this afternoon through this evening...As
forecast correctly by HREF higher percentiles 24hr ago, multiple
rounds of storms brought heavy rain to central WI. Observations of
2-3" with MRMS estimates as high as 4 inches in portions of Wood
and Marathon counties. Even with the break in rain into this
morning, soils are very primed and flash flood guidance is low
with even 3hr FFG not even 1.5 inches. Using 90th-95th percentiles
from HREF/NBM/LREF and with support from other models, there is
good agreement that another 1-3" of rain could occur from central
WI into north- central WI closer to incoming mid-level trough, jet
energy. Will issue a Flood Watch from early afternoon through
late evening for Wood, Portage, Marathon, Shawano, and Waupaca
counties. Other area that has higher ceiling today for rainfall
amounts is in the far southeast cwa, closer to the sharp gradient
of SBCAPE already noted. Since this area was not hit with heavy
rainfall and has overall higher FFG, will leave them out of a
watch. However, this area will have to be watched, especially if
more vulnerable urban Fox valley locations are hit by the swath of
heaviest rain.

This recent bout of higher impact active weather pattern shuts
down later tonight once sfc low shifts east and shoves the
instability axis out of the area.

Extended...Broad trough remains anchored over the upper Great
Lakes through the coming weekend. Saturday still looks to be the
more active day of the weekend as a secondary cold front drops
south. Instability will moderate to around 750-1000 J/kg by
Saturday afternoon, which when combined with mid-level wind fields
of 30-50 kts, will support a few stronger storms capable of gusty
winds and small hail. Pops have steadily increased over last few
days, now pushing into the likely category northeast and east-
central WI. 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 is Tuesday into Tuesday night as a northern stream
shortwave digs into the western Great Lakes.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1148 PM CDT Wed Jun 10 2026

An area of showers and thunderstorms across central Wisconsin
should track east but away from the main TAF sites during the
overnight hours. Low level moisture will bring some occasional
MVFR/IFR stratus and light fog through Thursday morning before
clearing makes its way in from the west. Fair weather cumulus
between 1,500 and 3,000 feet will develop Thursday morning.
Another round of strong to severe storms is expected to develop
Thursday afternoon. Wind gusts to or over 50 knots will be
possible. Placed initial timing into the TAF sites with TEMPO
groups with showers lingering behind the main line into Thursday
evening.

&&

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

Flood Watch from noon CDT today through this evening for WIZ030-
031-035>037.
&&

$$

DISCUSSION.....JLA
AVIATION.......Kurimski