683
FXUS63 KGRB 152318
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
618 PM CDT Tue Sep 15 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Breezy west winds gusting 20 to 30 mph this afternoon will
  subside early this evening.

- Hazardous marine conditions with Small Craft Advisories expected
  on Green Bay and Lake Michigan through early this evening. A
  dangerous rip current risk along Lake Michigan beaches will
  continue through early this evening.

- Widespread rain expected late Friday into Saturday, with a 50 to
  70 percent chance of rainfall exceeding 1 inch across much of
  northeast Wisconsin.

&&

.DISCUSSION...
Issued at 120 PM CDT Tue Sep 15 2026

Gusty westerly winds behind a departing cold front will subside
shortly after sunset with the loss of daytime heating. Surface
high pressure building across the northern Great Lakes will bring
dry and tranquil weather for tonight and Wednesday. Radiational
cooling beneath clear to partly cloudy skies and light winds will
promote the formation of patchy ground fog late tonight into early
Wednesday morning, particularly across far northern Wisconsin.
High temperatures Wednesday will be seasonable, reaching the upper
60s to low 70s.

As the frontal zone slowly returns north Wednesday night,
elevated warm advection will bring a 30 to 50 percent chance of
light showers to the region. However, moisture availability is
modest and elevated instability reaches only 100 to 200 J/kg,
keeping the probability of rainfall exceeding 0.50 inches under 10
to 20 percent, with no heavy rain impacts anticipated.

A more dynamic weather system is forecast to impact north-central
and northeast Wisconsin late Friday into Saturday as a shortwave
ejects from the western United States trough. Supported by a
40 to 50 knot low-level jet and precipitable water values rising
to around 1.70 inches (roughly 95 percent of seasonal normal),
widespread showers and embedded thunderstorms will spread across
the region. Probabilities of 24-hour exceedance have increased
this run as the NBM percentages for 1 inch or more is 50 to 70%,
with a 30-50% chance of exceeding 2 inches, and a small but not
insignificant probability of 10-25% of exceeding 3 inches Friday
and Saturday. Elevated instability remains limited with MUCAPEs
generally under 500 J/kg, keeping the severe thunderstorm risk
low.

Forecast predictability decreases markedly Sunday into Monday
depending on how quickly the main western trough moves eastward,
but lingering mid-level energy will maintain a 20 to 30 percent
chance of showers through Monday.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 616 PM CDT Tue Sep 15 2026

VFR conditions will prevail across much of the area through
Wednesday afternoon. The exception will be late tonight
from 07z-14z across the north where patchy fog may bring
some MVFR/IFR CIGS and VSBYs. The next chance of rain
will be on Wednesday night.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement until 7 PM CDT this evening for WIZ022.
&&

$$

DISCUSSION.....Kurimski
AVIATION.......Eckberg

NWS GRB Office Area Forecast Discussion