282
FXUS63 KGRB 241057
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
557 AM CDT Fri Jul 24 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Hazardous boating conditions for small craft are expected on
  Lake Michigan and central Green Bay this afternoon through late
  tonight. There is also an increased risk of rip currents on
  Door County beaches adjacent to Lake Michigan.

- Heat and humidity will build across the region this weekend into
  early next week, with heat indices reaching the middle to upper
  90s on Sunday and Monday.

- Periodic chances for thunderstorms return late tonight through
  Monday. The highest potential for strong to severe storms is
  expected on Sunday afternoon and evening and possibly again on
  Monday.

&&

.DISCUSSION...
Issued at 200 AM CDT Fri Jul 24 2026

The latest RAP analysis and satellite/radar imagery show high pressure
stretching across the southern Great Lakes early this morning. Surface
observations across northern Wisconsin indicate quiet, fair weather with
temperatures dropping into the low 50s to low 60s and calm to
light southwest winds. Upstream, weak shortwaves and modest warm
advection are generating light showers across central Minnesota
and northern Iowa. Further west, a potent subtropical ridge is
building northeast over the Intermountain West while a cold front
moves east across Saskatchewan. As this strong upper ridge expands
eastward and the cold front approaches the region, heat and
periodic thunderstorm potential will remain the primary focus
through early next week.

High pressure will slide to the eastern Great Lakes today, allowing southwest
flow to increase across the region. Breezier conditions are expected with
gusts up to 20 mph. Diurnal fair-weather cumulus will develop by late morning
around 4500 to 5500 feet before dissipation this evening. Highs today will rise
into the upper 70s to lower 80s. Clouds will increase tonight as
a cold front advances into northern Minnesota. A few showers and
elevated thunderstorms will approach north-central Wisconsin after
midnight as elevated instability increases to 500-1000 J/kg.

The cold front will lose definition as it crosses the Upper Peninsula and
Wisconsin on Saturday, with the strongest low-level convergence residing over
the Upper Peninsula. Warm, humid air will surge into the area on Saturday as
instability increases to 1000-2000 J/kg. Isolated thunderstorms could form
during peak heating, though capping in the 800-700mb layer will limit overall
coverage. Should storms develop, seasonably strong vertical shear would
support organized cell structures capable of producing large hail and damaging
winds. Highs on Saturday will climb into the mid 80s.

On Sunday and Monday, large-scale ascent driven by warm advection and passing
shortwaves will bring the highest potential for organized convection. A warm
front is forecast to lift northeast into the area by Sunday afternoon,
providing a surface focus beneath strong warm advection aloft. An environment
characterized by 2000-3000 J/kg of CAPE, 35-40 knots of deep-layer shear, and
an upper-level jet streak will be favorable for severe storms. However, capping
will remain a significant hindrance as 700mb temperatures rise to near 12C.
Potential for strong to severe storms will persist into Monday as a shortwave
trough and weak cold front push through the state.

Increasing heat will accompany the mid-level ridge on Sunday and
Monday. Afternoon highs on Sunday will range from the upper 80s to
mid 90s, with dewpoints in the upper 60s to lower 70s pushing
heat index values into the mid-to-upper 90s across central and
east- central Wisconsin. Heat indices will remain in the mid 90s
on Monday. Following the frontal passage on Monday night,
temperatures will remain slightly above seasonal averages through
Tuesday, Wednesday, and Thursday, with high temperatures generally
reaching the upper 70s to mid 80s. Widespread precipitation
chances look to remain low through the remainder of the work week
as high pressure settles back across the region.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 557 AM CDT Fri Jul 24 2026

High pressure sliding to the eastern Great Lakes will support VFR
conditions across KGRB, KATW, KMTW, KAUW, KCWA, and KRHI through
early tonight. Broken ceilings at 6000 ft from Marshfield to
Manitowoc will give way to diurnal cumulus near 4500 to 5500 ft
late this morning, which will lift to 5000 to 7000 ft this
afternoon before dissipating early this evening. Southwest winds
will increase today, with a 30% chance of gusts to 20 kts at KMTW
and KRHI.

Clouds increase tonight ahead of an approaching cold front, with
isolated showers near KRHI possible towards the end of the TAF
period. Ceilings will lower overnight, with MVFR ceilings
possible across central and north- central Wisconsin late in the
period. High confidence in VFR through early evening, with medium
confidence in ceiling trends overnight.

Outlook...Scattered thunderstorms and lower flight categories are
possible at times over the weekend as a warm and unstable airmass
shifts into the region.

.KOSH...
Broken 6 kft ceilings reside over OSH this early this morning.
These ceilings may stick around for several hours into the TAF
period before fair weather clouds develop late this morning with
cloud bases around 5-6 kft AGL. A period of broken ceilings is
possible from roughly 17-20Z. Southwest winds 5-10 kts may gust
up to 15 kts this afternoon before subsiding again tonight.

&&

.MARINE...
Issued at 200 AM CDT Fri Jul 24 2026

As high pressure shifts toward the eastern Great Lakes, the
surface pressure gradient will tighten across Lake Michigan,
helping to produce breezy south winds from 15 to 25 knots and
waves 3 to 5 feet this afternoon and evening. A Small Craft
Advisory and Beach Hazard Statement have been issued.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement from 4 PM CDT this afternoon through
late tonight for WIZ022.
&&

$$

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

NWS GRB Office Area Forecast Discussion