579
FXUS63 KGRB 160230
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
930 PM CDT Thu Oct 15 2026

Forecast discussion for routine evening forecast issuance

.KEY MESSAGES...

- Widespread rain continues tonight, becoming scattered into
  Friday morning. Most locations should see an additional 0.25 to
  0.5" of rainfall.

- Northwest winds increase on Friday, with gusts between 30 and 40
  mph expected. Locally higher gusts to 45 mph will be possible
  along the lakeshore counties. Gale force gusts are expected
  across marine zones.

- A Freeze Watch remains in effect for Friday night as low
  temperatures fall into the upper 20s to low 30s for areas inland
  of Lake Michigan.

&&

.DISCUSSION...
Issued at 900 PM CDT Thu Oct 15 2026

Rain chances through Friday... Radar and surface obs show
widespread stratiform rain ongoing late this evening as cold front
infringes on northwest Wisconsin and phased upper trough
approaches the Great Lakes. Expect rain to become more scattered
in coverage overnight into Friday morning with the loss of
moisture advection and upper jet support, though most locations
should still pick up an addition 0.25 to 0.5" of QPF.
Probabilities for receiving 0.5" of rain through tonight sit at
around 30 to 60%, highest over far northeast Wisconsin where
modest mid-level FGEN resides in proximity to the surface low.
Rain then tapers off from west to east late Friday morning, though
wrap around moisture may keep showers or drizzle around over
east-central Wisconsin through the afternoon.

Winds... Gradient winds ramp up Friday morning as a surge of CAA
accompanies northwesterly wind shift and building high pressure
over the Plains. Deep daytime mixing will tap into 40 to 45 knot
winds at 850 mb Friday afternoon, resulting in a high confidence
(60 to 90%) setup for widespread surface gusts between 30 and 40
mph. Only caveat will be Door County, where locally higher gusts
will be bumping up against advisory criteria. HREF currently
shows a 20 to 40% chance for gusts exceeding 44 mph over northern
Door, with sustained winds also coming within a mph or two of
criteria. Current thinking would be to hold off on an advisory for
the time being due to low confidence, though CAM trends will have
to be monitored on subsequent shifts.

Temperatures... Intrusion of arctic high paired with stout
northwesterly flow will result in a brief spell of well below
normal temperatures Friday and Friday night. Highs will struggle
to meet 50 degrees for many locations, with lows then plummeting
into the mid 20s to low 30s. Setup still looking favorable (50 to
70%) for a hard freeze Friday night, so have retained the Freeze
Watch. A rapid pattern shift to more seasonable temperatures then
occurs over the weekend as return flow sets up and upper flow de-
amplifies. As such, highs are progged to read mainly in the mid to
upper 60s through at least mid-week, with several shots at seeing
70 degrees.

Extended... High pressure looks to be the main driver of the
synoptic pattern through at least the middle of next week, with
no organized systems on the horizon. More active pattern then looks
to set up toward the end of next week as upper flow re-amplifies,
though details are few this far out.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 600 PM CDT Thu Oct 15 2026

Expect IFR cigs to persist through at least 06Z, though brief
improvements to MVFR will be possible. Otherwise, main impacts to
aviation will revolve around ongoing periods of light to moderate
rain that are forecast to continue through Friday morning. Have
thus gone prevailing SHRA with reduced vsbys at all TAF sites.
Rain coverage then becomes more SCT late tonight into Friday
morning, which should signal an improvement to more widespread
MVFR cigs. Potential for cigs lifting to VFR then exists after
18Z.

Northwesterly winds ramp up late Friday morning as rain comes to
an end from west to east. Surface gusts between 30 and 40 mph are
forecast for all terminals, peaking early Friday afternoon. A
brief period of LLWS will be possible over RHI, AUW, and CWA early
Friday morning as 850 mb winds increase.

&&

.MARINE...
Issued at 900 PM CDT Thu Oct 15 2026

Gale Warning remains on track for the Bay and Lake as northerly
winds ramp up following cold FROPA later this evening. HREF
probabilistic guidance is currently showing a 65 to 95% signal for
10-meter wind gusts exceeding 39 mph, which should translate
pretty well to gale force gusts over our marine zones. Waves will
build 4 to 7 ft on the Bay and 6 to 10 ft on the Lake during this
time. Have opted to throw out a wind down Small Craft Advisory
along the Lake Michigan nearshore waters on this shift, as waves
remain elevated through around 08Z Saturday as winds shift to more
westerly.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Freeze Watch from late Friday night through Saturday morning for
WIZ020-030-031-035>040-045-048>050-073-074.
&&

$$

DISCUSSION.....Goodin
AVIATION.......Goodin
MARINE.........Goodin

NWS GRB Office Area Forecast Discussion