030
FXUS63 KGRB 121753
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1253 PM CDT Sat Jul 12 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Rain continues this morning before a break in the precipitation
  arrives. Additional storms to develop in the afternoon.

- A few strong to severe storms will possible this afternoon and
  evening, with the best chance in far northeast Wisconsin near
  the Upper Peninsula border. Gusty winds are the main threat.

- Smoke will return over the weekend. An air quality advisory is
  in effect through Monday morning.

- Next round of active weather arrives during the middle of next
  week.

&&

.DISCUSSION...
Issued at 259 AM CDT Sat Jul 12 2025

Precipitation/Thunderstorm Chances...

The meso-low that brought rain to the region overnight will make
its slow departure to the northeast through the mid to late
morning hours. Reduced the additional rainfall totals for the
morning period a little, as the bulk of the more convective
elements with this system have largely passed to our southwest at
this time.

The departure of the overnight system could bring a brief break to
rainfall to the region, but a fast moving cold front and upper
shortwave will follow closely on its heels, with some isolated
convection already forming along the front upstream this morning.
Model soundings for the early afternoon suggest hitting
convective temperatures by around 1-3 PM, producing areas of
1000-1500 J/kg of surface based CAPE. This will generally coincide
with the arrival front in central Wisconsin, so additional
convective development is expected in the afternoon. Deep layer
sheer during this time period is around 35-45 knots, which would
also serve to organize any potential storms. That said, the main
source of uncertainty in the forecast will the degree to which we
destabilize, given the lingering rain and cloud cover from the
morning and the early arrival in the afternoon. Thus, while a
strong storm or two over central or north-central WIsconsin can`t
be ruled out, best chance for any stronger or severe storms will
likely be further east where a few more hours of destabilization
will be possible. CAMs point the main potential towards far
northeastern Wisconsin in the afternoon, along the Upper Peninsula
border, which makes sense. If severe storms form, damaging winds
will likely be the main threat given the speed of the front and
the potential for a more organized cold pool, but some brief hail
will also be possible. Dry conditions then return to the region by
the mid to late evening.

Medium range models continue to show potential for some isolated
to scattered convective activity both Sunday and Monday as a weak
boundary crosses the region. Added some low pops to the afternoon
and evening both days but would expect any rain to be low impact.

Finally, the next widespread active weather system will cross into
the region around the middle of next week along a cold front.

Smoke...
The passage of the cold front today will bring back northerly flow
and smoke to the region. The bulk of the smoke will cross the
region behind the front, giving a hazy appearance to the skies
even when clouds are absent. The DNR has issued an air quality
advisory that will last through Noon on Monday.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1253 PM CDT Sat Jul 12 2025

A mix of VFR and MVFR conditions will continue this afternoon. A
line or two of isolated to scattered showers and storms is
expected to move east across eastern WI this afternoon, but
overall storm coverage looks to be limited, due to a weak capping
inversion and limited surface convergence, so will keep the
thunder threat confined to PROB30 groups and add a TEMPO group if
necessary. As the line exits to the east, dry conditions are
expected tonight into Sunday morning.

Large area of smoke will spread into the Great Lakes today into
tonight. Upstream VSBYs mainly in the 2-5SM range, so have added
smoke into all the TAF sites.

&&

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

&&

$$

DISCUSSION.....Uhlmann
AVIATION.......Bersch