NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 122308
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
608 PM CDT Mon Oct 12 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- There is a 30 to 90% percent chance for light rain across the
  region this evening and early overnight, highest chances north.
  A couple rumbles of thunder will also be possible at times.

- Chances for more widespread soaking precip arrive late this
  week, though there is still much uncertainty. Much cooler
  temperatures next weekend.

&&

.DISCUSSION...
Issued at 223 PM CDT Mon Oct 12 2026

Precipitation tonight...
A surface low will track into the area this evening, accompanied
by a mid-level shortwave. The highest rain chances (70-90%)
accompanying the low will be on the northern edge of the warm air
this afternoon across northern Wisconsin, mainly north of a line
from Merrill to Oconto. Probabilistic guidance keeps a corridor of
40-60% chance of exceeding a half an inch of rainfall for the
northern areas. Precipitation potential will quickly taper off
south of this line, with around 20-40% chance across most of the
rest of the area. Still, would expect some short-lived showers to
produce some quick accumulations for central to east- central with
more measurable precipitation for northern Wisconsin. Some meager
upper instability accompanying showers could prove sufficient to
produce an occasional rumble of thunder (10-20% chance), but
expect widespread thunderstorms to be unlikely.

Precipitation Towards the End of the Week... A larger phasing
system is expected towards the end of the week as southern and
northern streams merge. Phasing systems generally have much
uncertainty in terms of timing but some general agreement has come
into alignment with the most recent forecast cycles. Rain will
start sometime in the late morning to afternoon hours and cross
the region into the overnight hours. How long the system remains
around into Friday remains uncertain and will depend largely on
whether the phasing occurs overhead or to our east. On the shorter
end, dry conditions could be back by Friday morning and on the
longer end some wrap around moisture could keep a few showers
around into Friday afternoon. Both solutions do still suggest
bringing enough cold air in on the backside of the system to
produce the first snowflakes across far north- central Wisconsin
near the Upper Peninsula border, but accumulations will generally
be brief and light. This system will also bring another period of
windy conditions for Friday.

Temperatures...
The near-record temperatures today will be the warmest
temperatures in the forecast, with high temperatures seeing a
downward trend through the end of the week. Friday is expected to
be the coldest day, with highs in the upper 40s in the northwoods
to middle 50s in the warmest areas. A small warmup trend is then
in store for the region over the weekend into next week.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 608 PM CDT Mon Oct 12 2026

Clouds continue to increase across the region as showers and
thunderstorms develop across central and north-central Wisconsin
early this evening ahead of an approaching low pressure system.
This activity looks like it will most likely affect central,
north-central, and northeast Wisconsin and less likely across
east-central Wisconsin. Therefore, will put in TEMPO groups for
the north and west with higher confidence and maintain the PROB30
groups for the east-central Wisconsin TAF sites as the main
activity is expected to lift north of these areas but a dry
forecast is not guaranteed. This activity should dissipate later
this evening with the loss of daytime heating as instability
wanes. While conditions are expected to remain VFR, any heavier
activity could briefly lower conditions to MVFR.

Lower clouds will wrap in behind the low pressure system in the
mid to late morning Tuesday, so would expect ceilings to drop to
MVFR and eventually IFR during the mid-morning hours. The lowest
conditions are expected across north-central Wisconsin.
Improvements to VFR are expected across central and east-central
Wisconsin later Tuesday morning and to MVFR across north-central
Wisconsin Tuesday afternoon.

&&

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

&&

$$

DISCUSSION.....Uhlmann
AVIATION.......Kurimski