184
FXUS63 KGRB 230840
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
340 AM CDT Mon Sep 23 2024

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Winds and waves will continue to decrease early this morning on
  Lake Michigan. A Small Craft Advisory remains in effect through
  7AM south of Sturgeon Bay. Dangerous swimming conditions
  continue on the beaches of Manitowoc Co. through 7AM.

- Patchy to areas of frost are expected across north central
  Wisconsin early this morning and possibly again Tuesday
  morning. A Frost Advisory remains in effect for portions of
  northern Wisconsin through 8AM.

- Temperatures close to normal are expected today and Tuesday then
  above normal temperatures are expected into the weekend. High
  temperatures could run as much as 10 to 15 degrees above normal.
  Current high temperatures Thursday and Friday are in the 75-90
  percentile range of the guidance values.

&&

.DISCUSSION...
Issued at 340 AM CDT Mon Sep 23 2024

Short Term...Today...Tonight...and Tuesday

A fairly quiet start to the new work week. Main forecast concerns
will be temp trends & frost potential, cloud trends, and small
rain and fog chances. Cooler (but near normal) temps are on tap
today and Tuesday.

Early This Morning: Temps across north central WI have fallen
pretty much as expected, with readings in the mid and upper 30s.
The typical cold spots will bottom out in the low 30s. Will not
make any changes to the frost advisory. Some ground fog also
developed, mainly across north central WI, which will burn off
shortly after sunrise.

Rest of Today: A quiet mid-late September day is expected for the
region as weak surface high pressure slides across the Great
Lakes. A few daytime cumulus clouds, along with a few clouds off
of Lake Michigan, are expected with high clouds increasing from
the south during the afternoon. 925mb between 12-13C support highs
in the mid 60s to around 70, which is near normal.

Tonight: Dry conditions are expected for most/all of the area.
Only thing to watch will be far east central WI where a pocket of
deeper moisture will work northward overnight. Still some low-
level dry air to contend with and better chances will stay to our
south/east, but could see some light showers or sprinkles closer
to Lake Michigan, along with more clouds. Mostly clear skies,
light winds and a low-level inversion will once again promote some
fog development overnight into early Tuesday, mainly across parts
of central and north central WI. SREF showing less than 10%
chance of visibilities 3 miles or less, with the HREF not
supporting much fog either. Think the fog will once again be
patchy ground fog and will burn off quickly after sunrise. Leaned
toward the colder guidance for lows across north central WI,
where clouds should be the highest/thinnest. Lows look to range
from the mid 30s to low 40s (coldest in the typical cold spots) to
the upper 40s and low 50s in the Fox Valley and lake shore. If
clouds stay out of the north, another frost advisory may be
needed, but lows look just slightly warmer than this morning.

Tuesday: Weak surface low pressure will track into southern Lake
Michigan, as a upper trough drops across the western Great Lakes.
This will bring more clouds to the region, along with low chances
(under 25%) mainly across far eastern WI. 925mb temps do not
change much, so highs should be similar to today, with perhaps
slightly cooler readings closer to Lake Michigan due to more cloud
cover.

Long Term...Tuesday Night Through Sunday

After a couple of days with near normal temperatures, above
normal temperatures will return Wednesday and continue into next
weekend. The upper trough across the central United States Tuesday
is going to evolve into a closed low over Missouri and Arkansas
with 500mb ridging across the western Great lakes into Thursday.
It gets interesting Thursday as the models are depicting a
tropical system moving northward across the Gulf of Mexico with a
landfall across the eastern Gulf Coast states. The remnants of
the tropical system will then dumbbell around the closed low
across Arkansas Thursday night into Saturday. The GFS/Canadian
models brush our southern counties with some light rain with this
feature. However, the ECMWF is much more pronounced with the 500mb
ridge across the Great Lakes, leaving the area dry Saturday with
a small chance of showers on Sunday.

With ridging across the area, expecting mostly clear skies and
light winds during the night which may result in some patchy
fog during the overnight hours to a few hours after sunrise
each morning. Expecting a larger than normal diurnal range each
day as well due to the dry air mass and longer nights. Guidance
values would suggest highs Thursday and Friday will run 10 to 15
degrees above normal, which was in the 75 to 90 percentile of all
guidance values. Guidance values for next weekend are heavy
weighted toward climatology, which now would be highs in the 60s.
Do expect high temperatures to go up a few degrees in the coming
days.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1035 PM CDT Sun Sep 22 2024

Mostly clear skies are expected overnight as high pressure builds
in across the western Great Lakes region. Some patchy ground fog
may develop across north-central Wisconsin late tonight into
early Monday morning, which may lower conditions to MVFR/IFR at
times. Any fog will lift Monday morning, with mostly sunny skies
and VFR conditions expected Monday into Monday evening.

Light winds below 10 knots are expected during the TAF period.

&&

.MARINE...
Issued at 340 AM CDT Mon Sep 23 2024

Winds have dropped under criteria across the bay and nearshore
waters of Lake Michigan early this morning. However, high wave
action continues on Lake Michigan. The mid-late buoy is still at
4ft at 3AM, with a SPOT buoy off of Two Creeks is reporting waves
around 5 ft around 3AM, which the wave model has captured very
well. As waves slowly subside, will cancel the Small Craft
Advisory for the bay and north of Sturgeon Bay on Lake Michigan at
09z and continue it south of Sturgeon Bay through 12z when waves
will drop under 4 ft.

As waves continue to subside this morning, the threat for
dangerous currents will end as well, with the higher waves
expected to be closer to the open waters. Manitowoc Co. will still
see a high swim risk through 7AM. Otherwise, the swim risk will
remain in the moderate category this morning. Will cancel the
Beach Hazards Statement for Door and Kewaunee.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 8 AM CDT this morning for WIZ005-010>012-
018-019.

Beach Hazards Statement until 7 AM CDT this morning for WIZ050.
&&

$$

DISCUSSION.....Bersch/Eckberg
AVIATION.......Kurimski
MARINE.........Bersch