555
FXUS63 KGRB 271642
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1142 AM CDT Fri Sep 27 2024

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Areas of fog, locally dense, are possible in north central
  Wisconsin late tonight.

- Warm temperatures to prevail through the end of the work week, with
  highs running between 10 to 15 degrees above average.

- Conditions hazardous to small craft are expected Saturday and
  Saturday evening for the Lake Michigan nearshore waters south of
  Sturgeon Bay. A Beach Hazards Statement has also been issued for
  Manitowoc County.

- The next chance of precipitation is expected to arrive Monday
  evening into Tuesday.

&&

.DISCUSSION...
Issued at 349 AM CDT Fri Sep 27 2024

Short Term...Today...Tonight...and Saturday

Forecast concerns include fog trends/potential, increasing winds
and associated marine and beach hazards on Saturday, and
continued much above normal high temperatures.

High pressure, mostly clear skies and light winds have allowed
patchy ground fog to form in river valleys and other sheltered,
low-lying areas early this morning. Otherwise, dry conditions
prevailed, with temperatures ranging from the middle 40s to the
50s across the forecast area.

Fog trends: Fog is expected to become a bit more widespread
shortly before sunrise, but should quickly mix out between
13z-14z. Fog will be a concern again tonight, but only over
north central and far northeast WI, where boundary layer winds
remain 5 to 10 knots. Farther south, increasing surface and
boundary layer winds should prevent fog formation.

Winds and associated hazards: The remnants of Hurricane Helene
will lift north toward the Ohio Valley today, and linger there
into Saturday. A gradual strengthening of the pressure gradient
will cause NE winds to increase later today into Saturday, with
gusts approaching 25 kts and waves building to 3 to 5 feet in our
southern marine areas by Saturday morning. Since much warmer than
normal temperatures may draw boaters out on Lake Michigan this
weekend, have opted to issue a Small Craft Advisory a little
earlier than usual. Likewise, have also issued A Beach Hazards
Statement for Manitowoc County, where 4+ foot waves and strong
currents may lead to increased potential for rip currents on
Saturday.

Temperatures: Much above normal temperatures will continue today
into Saturday, with highs both days in the upper 70s and lower
80s, except lower to middle 70s lakeside. Lows tonight will be in
the upper 40s to middle 50s in most locales.

Long Term...Saturday Night Through Thursday

Generally dry conditions are expected to purists through the
extended forecast with only a few slight chances (15-25%) for
precipitation. The above normal temperatures will also remain into
the early part of next week before moderating back toward normal
behind a cold front Tuesday.

Precipitation/Wind...Ensembles continue to trend dry Sunday as the
remnant moisture from tropical cyclone Helene is expected to remain
shunted off to the south and east. Main impact of Helene on
northeast WI will be more breezy conditions Sunday afternoon with
gusts along the lakeshore expected to reach 20-25 mph. NBM probs do
show a low-end (10%) for gusts reaching 30 mph across Manitowoc
County.

Next chance (15-25%) for rain showers is forecast to arrive late
Monday into Tuesday as a negatively tilted upper-trough and surface
cold front move across the western Great Lakes. Best chances for
measurable rain will be across northern WI, as that region will
reside closer to the dynamic forcing and deeper moisture. With
limited instability during this period the severe weather potential is
low, however, a narrow ribbon of higher mid-level lapse rates ~ 7-
7.5 C/km may support a few rumbles of thunder.

With a dry continental air mass over the region for the middle of
next week expected more dry conditions. Long range models do hint at
another possible chance for rain late next week with an upper trough,
but it`s too early to pin down any details.

Temperatures...The above normal temperatures will stick around
through into the early part of next week with highs in the lower to
upper 70s through Monday. The passage of a cold front will bring
more seasonal temperatures with highs in the upper 50s to upper 60s
for the middle part of next week.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1142 AM CDT Fri Sep 27 2024

VFR conditions are expected this afternoon through Saturday, with
the exception of a few hours of ground fog and IFR conditions in
northcentral Wisconsin late tonight through around 13z Saturday.

High cirrus clouds on the northern fringe of tropical storm
Helene will increase from southeast to northwest across Wisconsin
this afternoon and tonight. Scattered Cumulus clouds with bases
above 4000 feet are possible this afternoon and Saturday
afternoon.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement from Saturday morning through Saturday
evening for WIZ050.
&&

$$

DISCUSSION.....Kieckbusch/GK
AVIATION.......RDM