NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 121148
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
648 AM CDT Tue May 12 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Showers (50-80% chance) and isolated thunderstorms overspread
  the region this morning, then exit mid-day. Scattered showers
  and storms redevelop later this afternoon. A few strong to
  marginally severe storms possible over mainly east central WI
  from 3-7 pm.

- Windy conditions expected today through Wednesday, with
  hazardous conditions for small craft on the lake and bay.

- Additional rain chances expected Thursday night into Friday, and
  late Saturday night through Monday.

- Above normal temperatures expected later this week into early
  next week.

&&

.DISCUSSION...
Issued at 326 AM CDT Tue May 12 2026

High pressure and temperatures in the 30s lingered over far
eastern WI early this morning, but developing south winds and
increasing WAA combined to boost temperatures into the lower to
middle 40s farther west. Despite abundant dry below 500 mb (seen
on the 06z/Tue GRB sounding), strong WAA on the nose of a 40-50
kt LLJ and mid-level frontogenetic forcing was generating showers
and isolated thunderstorms in central and north central WI. WV
imagery showed a potent short-wave trough moving into NW MN. A
more concentrated area of storms was developing ahead of this
feature.

WAA showers and embedded elevated thunderstorms will overspread
the forecast area this morning. These showers should exit eastern
WI by around noon, followed by partial clearing, with subsequent
heating leading to modest SBCAPE of 400-800 j/kg over mainly
central and east central WI. As a cold front and the previously
mentioned short-wave move through in the mid to late afternoon,
scattered showers and storms should redevelop. Despite the
marginal instability, moderate to strong deep layer shear and
synoptic forcing should be sufficient to generate a few strong
storms capable of producing hail and gusty winds. SPC has
pushed the Marginal risk of severe storms farther north, covering
roughly the eastern two-thirds of the forecast area. This may be
a bit too far north, as temperatures over the Northwoods will
likely remain in the 50s and lower 60s, in sharp contrast to the
upper 60s and lower 70s anticipated over central and east central
WI. Winds will gust to 25 to 35 mph from the south ahead of the
cold front today, then from the northwest tonight into Wednesday.
Scattered showers linger over mainly northern WI this evening.

High pressure arrives later Wednesday into Thursday, with
associated dry conditions lingering into Thursday evening.

Another frontal system arrives Thursday night into Friday, with
showers and embedded storms expected.  After a brief dry period
Friday night into Saturday evening, a pattern change to southwest
flow aloft will commence. As this occurs, a cold front will
move slowly through the region, interacting with a surge of Gulf
moisture (PWATs of 1.25 to 1.75 inches) and instability, and
producing periods of showers and storms from late Saturday night
through Monday or Monday night. The pattern supports potential
for heavy rainfall, but models are all over the place regarding
timing and placement.

Temperatures will remain below normal over northern WI today
and across the entire forecast area on Wednesday, but are
expected to climb above normal late this week into early next
week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 634 AM CDT Tue May 12 2026

WAA on the nose of a 40 to 50 knot low-level jet was generating
showers and a few thunderstorms this morning. These are expected
to shift east of the region mid-day, with additional scattered
showers and storms developing ahead of a cold front in the
mid to late afternoon. Showers will linger across northern WI into
the evening before dissipating. Flight conditions will remain VFR
in most areas through late afternoon, then post-frontal MVFR
ceilings will overspread the region from NW to SE through the
evening.

SE-S winds will quickly ramp up this morning, with gusts to 25 to
30 knots expected. The winds will veer SW-W this afternoon as
the cold front moves through, then NW by early evening. Continued
gusts to 25 knots can be expected. LLWS will also overspread the
region this morning, then taper off in the early to mid afternoon.

&&

.FIRE WEATHER...
Issued at 326 AM CDT Tue May 12 2026

Pine fuels have reached their peak volatility and fine fuels have
still not greened up over northern WI, so upcoming dry and windy
weather on Wednesday and low relative humidity (RHs 20-30%) on
Thursday will result in elevated fire weather conditions.

&&

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

&&

$$

DISCUSSION.....Kieckbusch
AVIATION.......Kieckbusch
FIRE WEATHER...Kieckbusch