940
FXUS63 KGRB 302306
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
606 PM CDT Wed Sep 30 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Another round of rain is expected tonight into Thursday. Total
  rainfall amounts up to about 0.5 inches are forecast for
  portions of central to east-central Wisconsin.

- Persistent Southerly winds will result in hazardous swimming
  and boating conditions on Lake Michigan through this evening.

- Patchy frost will be possible at times across northern Wisconsin
  late this week into the weekend. Greatest chance for a freeze is
  Sunday night across northern WI.

&&

.DISCUSSION...
Issued at 1203 PM CDT Wed Sep 30 2026

Rain chances into Thursday: Isolated to scattered showers will
continue through this afternoon across far northeast WI as weak
isentropic ascent continues over the region. Overnight into Thursday
morning another round of widespread light to moderate rain will
overspread central and east-central WI as a weak short-wave coupled
with a surface cold front trek across the region. CAMs continue to
trend the axis of heaviest rain south, focused more along the I-94
corridor. Areas along and south of HWY 10 have about a 30-60% chance
to see at least 0.5" of rain, with lower amounts expected further
north. Areas across north-central WI may miss out on rain entirely.
Along with the rain a saturated boundary layer will lead to areas
of fog developing tonight into Thursday morning. Rain will come to
an end from northwest to southeast Thursday as cooler drier air
filters over the region behind the front.

Extended... High pressure builds back in across the upper Midwest
Thursday evening, lasting through at least the middle of next week.
Only exception will be a 25 to 40% chance for rain on Saturday with
the passage of a fast moving short-wave. Otherwise, main forecast
concerns for the extended is potential frost/freeze conditions
toward the end of the week as high sits overhead and 850 mb
temperatures fall to near 0C. There will be a high likelihood of
patchy frost occurrence several times across the north through
early next week, though we could be looking at a more widespread
frost/freeze event Sunday into Monday. Will continue to monitor
trends for headline potential as we approach the end of the
growing season.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 606 PM CDT Wed Sep 30 2026

A cold front over northwest Wisconsin will gradually drop
southeast as a low pressure system tracks from the Central Plains
tonight across northern Illinois on Thursday morning. With
abundant low level moisture, mainly MVFR/IFR ceilings will lower
and return north through 05-07Z Thu with spotty showers in the
area. Coverage is expected to be sufficiently sparse to exclude
from the forecast.

As the low tracks closer, light rain chances will increase in the
07-16Z Thu period, mainly over east-central WI. KATW and KMTW have
the greatest potential to be impacted from the showers. KGRB,
KAUW, and KCWA will be on the northern periphery and confidence of
shower activity is lower there. Regardless, lowering ceilings
should result in widespread LIFR/IFR conditions along with
IFR/MVFR visibilities.

As rain potential ends after 16Z Thu, winds will shift to the
northwest and finally usher in drier low level air. Will therefore
see ceilings increase with a return to VFR conditions possible at
all terminals by 21Z Thu.

&&

.MARINE...
Issued at 1203 PM CDT Wed Sep 30 2026

Southerly winds will result in a period of hazardous marine
conditions along Lake Michigan nearshore waters through late
tonight. Winds will be sustained at around 10 to 15 knots with gusts
to 25 knots, highest near Death`s Door. Waves will build between 3
and 5 ft. Waves then subside Thursday morning as winds decrease and
veer to the northwest. High waves and strong currents will also
result in dangerous swimming conditions along Lake Michigan beaches
in Manitowoc, Kewaunee, and Door counties through late tonight.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement until 4 AM CDT Thursday for WIZ022-040-
050.
&&

$$

DISCUSSION.....GK
AVIATION.......MPC
MARINE.........GK