829
FXUS63 KGRB 061731
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1231 PM CDT Thu Jun 6 2024

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Breezy conditions are expected today and Friday, with gusts to
  30-35 mph. Wind gusts to 40 mph are possible today in/around
  any shower activity.

- Conditions hazardous to small craft are expected today and
  Friday.

- Showers are expected at times today, especially over northern
  WI. Additional showers are possible at times this weekend, with
  a chance of thunderstorms on Saturday.

&&

.DISCUSSION...
Issued at 424 AM CDT Thu Jun 6 2024

Short Term...Today...Tonight...and Friday

A pattern more akin to fall arrives today, bringing breezy and
showery conditions. Things dry out on Friday but it will remain
breezy. Main forecast concerns revolve around shower chances,
whether we will get a stray storm today and how high winds will
gust.

Showers Trends / Thunder Threat / Winds:

Dry conditions, along with some clearing, will start off the day.
However, clouds will spread back into the area from northwest to
southeast through the morning, reaching the Fox Valley and lake
shore last. Deeper moisture and another shortwave will rotate
through the area today, as the parent upper low drifts across Lake
Superior. This will produce scattered to numerous showers over
northern WI later this morning and afternoon, with more spotty
coverage as you work further south. Coverage will decrease in the
late afternoon and evening, with mainly dry conditions expected
overnight into Friday as some drier air and ridging briefly works
into the western Great Lakes. A stray thunderstorm is possible
late this morning and afternoon as MUCAPE climbs to around 200
J/kg, But with chances staying around 10%, opted to not include in
the forecast. Better chances look to be in the U.P. where some
lake boundaries will aid in convergence and slightly more
instability is forecast.

West-northwest winds will gust up to around 30 mph today, with
some better mixing in/around any shower bringing down winds up to
40 mph at times, as winds at 5000 ft will remain around 35 kts.
The gustiness will ease this evening and overnight, then west-
northwest winds will gust to around 35 mph again on Friday.

Temps / Humidity:

Have leaned toward the cooler guidance today as clouds/precip
will hold down temps. This is pretty much in line with the
previous forecast, holding highs in the mid and upper 50s in
north-central WI and the lower and middle 60s over eastern WI. If
the rain/clouds hold off a little longer, temps will get into the
upper 60s over the south/east. Lows tonight will drop into the mid
40s to mid 50s. Highs on Friday will rebound back into the mid 60s
to low 70s as WAA pushes in from the west. It will be much less
humid today into Friday as dewpoints remain in the 40s and low
50s.

Long Term...Friday Night Through Wednesday

Main focus from this forecast period revolves around the
precipitation chances for the weekend. Biggest change from the
previous forecast is the strength of the closed low progged to sit
over the eastern Great Lakes/southeastern Ontario/southern Quebec
region, which has trended weaker. This will allow for any shortwaves
circulating around the closed low or any embedded shortwave energy
riding along the mean northwest flow present over the Upper
Mississippi Valley to more easily move over the area.

That being said, the next chance for precip looks to occur sometime
on Saturday associated with shortwave energy riding along the
northwest flow in combination with a shortwave trough circulating
around the closed low over southern Quebec. While most locations
across the forecast area look to receive some precip, models are not
in agreement with which feature will be the stronger of the two,
causing uncertainty with who will see the better chances.
Thunderstorms will be possible, but will be dependent on if precip
occurs during the morning or peak heating, as some models are
suggesting. Additional showers are possible on Sunday as energy from
the shortwave trough continues to circulate over the western Great
Lakes. These showers will likely be diurnally driven and should stay
confined to northern WI.

Dry conditions return for Monday with upper-level ridging progged to
build over the Upper Mississippi Valley. The trailing trough looks
to bring the next chance for showers and possible storms on Tuesday,
followed by dry weather for midweek.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1230 PM CDT Thu Jun 6 2024

Pop-up showers have developed north of an OSH to MTW this morning.
The coverage of these showers is more widespread across northern WI
with more isolated coverage further south. Expect these showers to
continues across the region through the afternoon before waning
this evening. Northwesterly winds have also increase this morning
with gusts reaching 20-25 kts at most locations. Breezy conditions
will remain through this afternoon and evening. A few strong
gusts between 30-35 kts will also be possible this afternoon
around any showers that move over a terminal. Low-end VFR cigs are
forecast for this afternoon with periodic drops to MVFR north of
a AUW to IMT line as showers move over terminals.

Did include LLWS in the CWA, AUW, and RHI TAFs for a brief period
around midnight as winds at the surface decrease slightly, but winds
at 1.5-2 kft remain around 30-35 kts. Expect breezy conditions again
Friday as a strong upper-level jet moves over the region.

&&

.MARINE...
Issued at 424 AM CDT Thu Jun 6 2024

Have expanded the Small Craft Advisory to include all of our area
as soundings showing better mixing near Lake Michigan today.
Highest winds look to be south of Sturgeon Bay. Offshore winds
will keep waves mainly under 2 ft. Similar set up on Friday with
gusts to around 25 kts likely, so another Small Craft Advisory
may be needed.

&&

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

&&

$$

DISCUSSION.....Bersch/Kruk
AVIATION.......GK
MARINE.........Bersch