273
FXUS63 KGRB 231142
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
642 AM CDT Sun Aug 23 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Dry weather today into Monday, with chances (50-80%) arriving
  Tuesday afternoon into Wednesday. Shower/storm chances linger
  into Thursday.

- Slightly below normal temps today, then a return to near or
  slightly above normal readings for most of the new work week.
  Lows tonight drop into the 30s across north-central.

&&

.DISCUSSION...
Issued at 109 AM CDT Sun Aug 23 2026

Today into Monday...Quiet weather conditions are on tap for the
Great Lakes region as northwest flow prevails. The cooler air
moving over the Great Lakes will generate some cloud development
at times, especially over northern and eastern WI. Some daytime
cumulus clouds are also expected later this morning and afternoon.
Some showers/sprinkles are also expected across the central and
eastern U.P. today. A couple of these could clip northern Door Co.
Otherwise, dry conditions are expected as surface high pressure
moves in. Northwest winds will increase this morning, with gusts
to around 20 mph from mid-late morning into the afternoon, with
winds easing after sunset. Some very patchy ground fog will be
possible this morning and again Monday morning, especially across
central and northern WI.

Tuesday into Wednesday...Next chance for showers and some storms
arrives Tuesday afternoon through Wednesday afternoon as a sharp
mid-level trough and surface cold front work through. Details
remain a little elusive as timing/strength differences remain with
the front/forcing. So can`t put too much confidence into when the
best shot for rain will occur or the threat for stronger storms,
but 50-80% PoPs arrive Tuesday evening/overnight as the initial
WAA arrives. Chances for additional storms on Wednesday as the
front moves across the area, but timing will determine when the
highest chances will occur. LREF showing MUCAPEs up to ~1000 J/kg
late Tuesday and up to ~1500 J/kg on Wednesday with deep layer
shear in the 20-35 kt range. So some stronger storms will be
possible if things line up right. Machine Learning not
highlighting much of a severe threat at this point either. So will
have to monitor for severe weather trends.

Thursday into Saturday...After the front exits to the east, and
similar to Saturday, steep low-level lapse rates, a weak shortwave
and colder air aloft combined with peak heating should produce
isolated to scattered showers and storms on Thursday, mainly in
the afternoon. Dry conditions look to return on Friday with
another possible weather system arriving next weekend.

Temperatures...Below normal temps are expected today with highs
ranging from the mid 60s to low 70s over northern WI to the 70s
elsewhere. It will be chilly tonight with ideal radiational
cooling conditions, with lows dropping into the mid 30s to around
40 across northern WI (where some very patchy frost is possible)
and into the 40s to around 50 elsewhere. After the brief cool day
down today and tonight, temps return to near or slightly above
normal with highs mainly in the mid 70s to mid 80s. Normal highs
for the coming week start off in the 77-78F range, but by next
weekend fall off into the mid 70s.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 642 AM CDT Sun Aug 23 2026

Other than some very patchy ground fog across north-central WI
early this morning and possibly early Monday morning, look for
VFR conditions through the TAF period. A small batch of mid-clouds
will move across parts of central and northern WI this morning,
with additional fair weather VFR (5-7 kft) cumulus clouds forming
later this morning and afternoon. Skies will clear out late this
afternoon and evening.

Northwest winds will gust between 13-18 kts today, then become
light and variable this evening.

&&

.MARINE...
Issued at 109 AM CDT Sun Aug 23 2026

Northwest winds of 10-20 kts will continue today into tonight
with gusts to 25 kts possible mainly north of Sturgeon Bay. Gusts
have been struggling to get to 25 kts overnight, with only the
mid-lake buoy hitting 25 kts for a short time. With CAA
continuing this morning, still could see gusts to 25 kts. And the
HREF 10m gust ensemble mean still showing 25-30 kt winds right
to Washington Island, but keep the stronger winds towards northern
Lake Michigan. Will continue the Small Craft Advisory for the
central Bay and for Lake Michigan nearshore waters north of
Sturgeon Bay through 15z.

Offshore winds will limit waves to 1 to 3 ft for most spots on the
bay and nearshore waters, with any 3-4 foot waves staying near
Deaths Door and in the open waters.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion