347
FXUS63 KGRB 281119
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
619 AM CDT Thu Aug 28 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Breezy on the lake and bay today into this evening. Conditions
  will be hazardous to small craft on Lake Michigan, with small
  craft advised to exercise caution on the Bay of Green Bay.
  Higher waves will result in dangerous currents, especially for
  beaches of Manitowoc County. A Beach Hazards Statement has been
  issued.

- A Frost Advisory has been issued for late tonight into early
  Friday morning for Vilas County. 60-90% probability of
  temperatures 36 degrees or colder.

- Small chance of rain added to the forecast over central WI
  Friday. Overall though, dry and comfortable through Labor Day.

&&

.DISCUSSION...
Issued at 325 AM CDT Thu Aug 28 2025

Shortwave and lead sfc trough is supporting broken band of showers
with very isolated thunderstorms arcing from Rapids to Oshkosh,
and to Manitowoc. Storm over Clark County in central WI has had
the most lightning and some signal of small hail in the last couple
hours, but more southerly track of this will lead to it missing
western Wood County. Cold front is dropping into northern WI with
rapidly expanding stratus over Upper Michigan into far northern
WI. Areas of dense fog are currently present over north-central
WI, especially Vilas County, but once stratus moves in this fog
may thin some as did occur in Upper Michigan. Will monitor near
term trends to see if Dense Fog Advisory is needed. Possible that
the fog could expand farther south as the rain ends. Any fog should
diminish between 8 and 10 am.

Once the showers shift south and fog diminishes, expect the main
issue today to be over the waters as northerly winds increase
behind the cold front. Winds and wind gusts will result in
building waves on Lake Michigan, especially south of Algoma.
Extended Small Craft Advisory in time to catch lingering higher
waves. Also, though bulk of higher waves remain just offshore,
shoreline that jets farther into Lake Michigan north of Two Rivers
will be prone if there are any issues from the waves. Have issued
a Beach Hazards Statement to cover the dangerous swimming conditions.
Both the Small Craft Advisory and Beach Hazards Statement run
from noon through 1 am Friday. Also, though winds/gusts are
marginal, put a Small Craft exercise caution out on the bay with
waves becoming choppy, up to 3-4 feet. Otherwise, for today
expect clouds to clear out this afternoon with highs staying
mainly in the mid 60s north and near the lakeshore, to as warm as
the lower 70s central.

High pressure and dry air aloft (low PWATs around 25 percent of
normal) settles overhead tonight and frost becomes the main
focus. Greatest risk for temps to drop into the lower and middle
30s remains over Vilas County with some potential also into far
northern Forest County and extreme northeast Oneida County.
Probabilities of temps less than 37 have decreased in areal
coverage, but remain 60-90% for these specific areas. However,
could also see some fog and possible low stratus impact cooling
and there is now even a signal for light precip to move into far
northwest WI late tonight, spreading some cloud cover toward
north-central. MOS guidance which would be pretty locked in at
this point is not all that cold, even at typical cold spots
(lowest at LNL and TKV is 34). This may be due to all the above
factors. Main point is there are some mixed signals on how cold
it gets tonight and the impact on frost potential. Have issued
Frost Advisory for Vilas County only at this point, which matches
up well against NWS DLH (Iron County WI) and NWS MQT (Gogebic and
Iron County MI). Dayshift can look to see if any expansion to the
headline is needed.

Last item to cover in the near term is models now showing a bit
more precip on Friday over central WI. Weak wave, mid-level fgen
on southwest side of sheared out jet seem to be what is driving
the precip. Variance in models, ensembles is whether much QPF
makes it as far east as central WI. Followed HREF and added slight
chances (15-20%) for showers with a buffer mention of sprinkles
southwest of Wausau to Oshkosh line. At the least, this area of
central WI will see mostly cloudy skies for the day. Elsewhere,
plan on mostly sunny skies and high temperatures generally staying
below 70.

Beyond Friday, it still looks dry right through Labor Day. High
temperatures will be on the rebound with readings lifting back
into the mid 70s. The next chance of rain and some thunder arrives
late Tuesday into Tuesday night.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 617 AM CDT Thu Aug 28 2025

IFR to lower MVFR stratus did develop overnight and has now
expanded from the north, now extending as far south as AUW/GRB/MTW.
Expect the stratus to shift farther south and persist through the
morning, with further lowering possible based on upstream obs.
Eventually though, much drier air will move in, with clearing
arriving late this morning at RHI, and during the early afternoon
at the rest of the TAF sites. After a period of mostly clear skies
from late this afternoon through much of the night, another round
of less widespread IFR stratus is expected after midnight over
northern WI, including RHI.

Winds will turn NW-N this morning, then increase later this
morning, especially in the Fox Valley/lakeshore areas where
gusts to 15 to 20 knots are anticipated through the afternoon.
Winds become light by this evening.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 1 AM to 8 AM CDT Friday for WIZ005.

Beach Hazards Statement from noon CDT today through late tonight
for WIZ050.
&&

$$

DISCUSSION.....JLA
AVIATION.......JLA