326
FXUS63 KGRB 101049
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
549 AM CDT Thu Sep 10 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Chances for thunderstorms return on Friday night into Saturday
  morning. The severe weather threat is low.

- Potential for heavy rainfall and thunderstorms increases Sunday
  into Monday as a stronger low pressure system tracks near the
  region, though forecast uncertainty remains high.

&&

.DISCUSSION...
Issued at 218 AM CDT Thu Sep 10 2026

A few patchy areas of shallow ground fog may develop early this
morning across central WI with clear skies and calm winds, otherwise
with high pressure moving across the region no impactful weather
is expected today

Storm Chances Return Late Friday: Next chance for
showers/thunderstorms comes late Friday night into Saturday morning
as an upper trough drags a cold front across the region. The risk
for any severe storms is very low (less than 5%) as forecast
soundings show a stout capping inversion during the period. Guidance
also continues to show the axis of greatest instability and
moisture remaining well west of the forecast area. There is still
some timing uncertainty with when rain may come to an end Saturday
as recent model guidance has come in slower with the passage of
the front which could lead to showers lingering through the
morning Saturday. Weak high pressure is then progged to move in
returning dry conditions for the remainder Saturday.

Heavy Rain and Storms Early Next Week: A dynamic synoptic system is
progged to lift northeast across the northern Plains and western
Great Lakes late Sunday into Monday. Global ensembles show a
strong mass response ahead of this system with PWATS increasing
near 2" which is around 200% of normal for this time of year. The
high moisture content and strong dynamical lift does support an
increased risk for heavy rainfall with NBM probs showing 30-50%
chances greater than 2" of rain across much of the forecast area.
There is also a low risk for a few stronger storms to develop
Monday as strong ~50kt deep layer shear overspreads an unstable
airmass, however, forecast soundings show a stout inversion near
the surface which may keep storms elevated rather than surface
based.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 549 AM CDT Thu Sep 10 2026

VFR conditions will prevail through the TAF period. Westerly winds
will remain under 10 kts today. SCT fair-weather cu, with cigs
around 5000-6000 ft AGL, will develop late this morning across
central and north-central WI TAF sites and continue through the late
afternoon. Cigs may briefly become BKN at RHI, and FEW reaching the
east-central WI TAF sites. Skies will clear out this evening (after
00z). A few patchy areas of ground fog may develop early Friday
morning, but confidence that fog impacts any TAF sites is low.

Beyond the TAF period the next chance for showers and thunderstorms
arrives with the passage of a cold front late Friday into Saturday.

&&

.MARINE...
Issued at 218 AM CDT Thu Sep 10 2026

A Small Craft Advisory and Beach Hazards Statement will likely be
needed from Friday afternoon through Saturday morning for gusty
south winds to 30 kts and waves 3-6 ft.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion