NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 121122
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
622 AM CDT Fri Jun 12 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Showers and some storms late tonight. Severe weather not
  expected, but small hail could occur.

- Scattered storms Saturday. Marginal risk (level 1 of 5) for
  severe storms in the afternoon.

- Hazardous boating conditions on the bay and lake late this
  morning through early this evening.

&&

.DISCUSSION...
Issued at 227 AM CDT Fri Jun 12 2026

Near term through tonight...Primary cold front has shifted east
pushing plume of deeper moisture and highest instability over the
lower Great Lakes. Reinforcing cold front moves in late tonight
and swings through on Saturday. Ahead of that front, deeper mixing
will result in breezy conditions by this afternoon, including on
the bay and lake waters with conditions reaching Small Craft
Advisory criteria. Good deal of sunshine and lingering warmth
aloft should allow max temps to reach upper 70s to low 80s,
warmest far northeast WI to east-central WI where NW winds
downslope. Very small chance of a few sprinkles far north where cu
is more developed this afternoon, but cloud depths in soundings
appear too shallow to include it.

By late this evening and overnight, shortwave/mid-level speed max
and LLJ/fgen will combine to produce swath of showers and also
some thunder as MUCAPEs increase to 500J/kg. Rainfall amounts
locally up to 0.50 inch could occur north of highway 29. Despite
effective shear 40 kts, limited instability should preclude severe
storms, though small hail could occur in stronger cells.

Severe potential Saturday...Cold front settles to eastern WI
Saturday afternoon. Convergence along front is weak, but there is
sharp moisture convergence with low 60s dewpoints east, while 40s
dewpoints shift into north-central WI. Sfc based CAPES increasing
to 1000-1500 J/kg Fox Valley to the lakeshore paired with effective
shear up to 50 kts supports the risk of severe storms, with hail
and damaging wind gusts the primary hazards. SPC continues to
highlight areas from Waushara to Door counties and points southeast
in a Marginal Risk (level 1 of 5) for severe. At this point, CAMs
not too excited with coverage of stronger storms based on HREF
paintballs for reflectivites over 40 dbz and where max updraft
helicities are located, so coverage of severe storms may end up
more isolated.

Extended...Behind the secondary weekend cold front, strong cooling
trend takes hold through much of next week as broad troughing with
heights well below average becomes centered over the upper Great
Lakes. High temperatures will fall back into the mid 60s to mid
70s through late in the week. Coolest days will be Sunday/Monday
and Wednesday. Chances for showers and some storms Tuesday and
Tuesday night as a northern stream shortwave digs into the western
Great Lakes, with yet another quick-moving system bringing more
showers and storms on Wednesday. Small chances for rain linger at
the end of the week as well given the troughing pattern in place.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 620 AM CDT Fri Jun 12 2026

A few IFR clouds linger at RHI to start the TAF period. Otherwise,
rest of day into the evening will be VFR at all terminals with few
cu this afternoon. Clouds thicken later this evening with scattered
showers blossoming over MN into western WI moving across the area
mainly after 06z. Some thunder may be embedded in the showers.
Generally VFR with the showers, but late tonight MVFR cigs may
develop at RHI.

Westerly winds gusts of 15 kts increase to 25 kts late this
morning through the afternoon, before diminishing to 15 kts again
tonight. Low-level jet ramping up will result in LLWS at RHI overnight.

&&

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

&&

$$

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