492
FXUS63 KGRB 182345
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
645 PM CDT Fri Sep 18 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- A period of moderate to heavy rainfall is expected through
  Saturday, with the heaviest rain occurring tonight. A 40 to 60
  percent chance of rainfall exceeding 2 inches exists roughly
  south of a Marshfield to Appleton line.

- A Beach Hazards Statement and corresponding Small Craft Advisory
  has been issued late tonight into Saturday evening for areas
  south of Algoma.

- A quieter and drier weather pattern will settle into the region
  early to mid next week.

&&

.DISCUSSION...
Issued at 129 PM CDT Fri Sep 18 2026

Heavy Rainfall Potential through Saturday: Rain associated with a
low pressure system emerging from the Plains is having issues
making steady progress into the area given the abundant amount of
low level moisture being pumped in from a high pressure system
over western Quebec. The initial surge of moisture should moisten
the low levels through this afternoon, which will set the stage
for steadier rain to make its way through the region later this
afternoon and into tonight. This rain will last through Saturday
when the low tracks to our south, coming to an end Saturday night.
The heaviest rain still looks to be just to our south coincident
with the best instability and frontogenesis. While there are still
some models that edge the heavier rain into the southern CWA, the
general trend and consensus is to keep the higher amounts to our
south. The southern solution also looks to be the most reasonable
given we mostly miss out on instability from this event, which is
needed to produce the heavier rain showers.

Quiet Weather Next Week: Looking ahead to next week, shortwave
energy originating from the western North American trough will
slowly migrate east from the central Plains to the southern Great
Lakes and eventually the east coast. Therefore, it appears that
most of the rain will remain south of the region. Otherwise,
strong high pressure over northern Ontario and northern Quebec
looks to keep ample dry air across northern Wisconsin which should
keep next week mostly dry.

With high pressure maintaining dry and quiet conditions for the
bulk of the extended period, temperatures will be undergoing a
slow warming trend. Daytime highs ranging from the low to mid 60s
on Monday will gradually warm each day, reaching the low to mid
70s by Thursday and next Friday.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 644 PM CDT Fri Sep 18 2026

Poor flying conditions expected through most of the TAF period as
low pressure moves across the region, bringing low clouds,
reduced visibility, and periods of rain. A rumble of thunder is
also possible, mainly south of Hwy 29, but chances too low to
include, with higher storm chances just south of the area.
Ceilings will continue to fall this evening and settle mainly in
the IFR range overnight into Saturday, with a few LIFR conditions
possible at times. Reduced visibilities to high end IFR to low end
MVFR are likely in the heavier downpours.

East/southeast winds will be rather steady tonight into Saturday
morning, then will shift to the northeast Saturday afternoon/
evening. Gusts to 20 kts are expected.

&&

.MARINE...
Issued at 129 PM CDT Fri Sep 18 2026

Gusty easterly winds ahead of and during the passage of the
aforementioned low pressure system will build wave heights
significantly on Lake Michigan from late tonight through
Saturday evening. This will create hazardous conditions for small
craft and increase the risk for dangerous rip currents along
beaches south of Algoma. Given the higher certainty will issue a
Small Craft Advisory and Beach Hazards Statement for the Lake
Michigan nearshore and beaches south of Algoma through Saturday
evening.

Another round of hazardous marine conditions looks likely Sunday
through Monday due to gusty northeast winds 20 to 30 kts and high
waves.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement from 3 AM CDT Saturday through Saturday
evening for WIZ040-050.
&&

$$

DISCUSSION.....Kurimski
AVIATION.......Bersch
MARINE.........Kurimski

NWS GRB Office Area Forecast Discussion