506
FXUS63 KGRB 260812
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
312 AM CDT Thu Sep 26 2024

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Areas of fog, locally dense, will impact morning commuters today
  and again on Friday.

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

- Only slight chances for rain this weekend as residual moisture
  from Helene is primarily shunted to our south and east. The next
  chance of precipitation is expected to arrive Monday afternoon.

&&

.DISCUSSION...
Issued at 310 AM CDT Thu Sep 26 2024

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

High pressure, mostly clear skies and light winds have allowed
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.

The fog will mix out between 13z-14z, followed by abundant
sunshine and temperatures rising into the upper 70s and lower 80s.
Developing southeast winds will keep highs in the middle 70s near
Lake Michigan.

Fog will once again be the main forecast concern tonight, with
similar conditions to this morning. Expect areas of fog and
patchy dense fog, especially in NC/C/far NE WI. Low temperatures
will be in the middle 40s to middle 50s.

Fog mixes out early Friday, with mostly sunny skies helping to
boost temperatures into the upper 70s and lower 80s, except middle
70s lakeside. Winds will turn northeast, in response to the
remnants of Hurricane Helene moving into the Ohio Valley.

Long Term...Friday Night Through Wednesday

A generally dry forecast through the extended with only a few low-
end chances for precipitation Sunday into Monday morning the with
the remnants of Hurricane Helene, and Monday evening into Tuesday
with the passage of a cold front. Otherwise, temperatures for this
weekend are expected to trend above normal before moderating back to
or just slightly below normal behind the aforementioned cold front.

Precipitation...A dry continental air mass will reside over the
region to begin the weekend as a rex block pattern breaks down with
a flattening ridge shifting toward the eastern Great Lakes. This
will allow for remnant moisture from tropical cyclone Helene to
surge northward through the Ohio Valley, and may lead to a few
showers south of highway 10 Sunday afternoon through Monday morning.
However, LREF and NBM probs have consistently shown the better
chances for rain during this period will be shunted off to the
south and east over southern lower Michigan and northern Indiana.

As the remnants of Helene shift off to the east attention will then
turn to a rather dynamic upper-level trough this is forecast to dig
into the western Great Lakes late Monday into Tuesday. This through
along with its accompanying cold front will bring a chance (15-30%)
for rain showers, mainly north of highway 29 Monday evening through
Tuesday. Given the lack of instability during this time the severe
weather threat is low, however, with a ribbon of steeper mid-level
lapse rates ~ 7-7.5 C/km wouldn`t rule out a few rumbles of thunder
Monday evening.

Beyond Tuesday long range models generally favor a dry middle of the
week with another trough potentially crossing the region toward the
end of the week.

Temperatures...Anomalously warm 850mb temperatures ~ 14-16C will keep
conditions summer-like this weekend with highs in the middle to
upper 70s each day. Anticipate a rather sharp cold front moving
across the region late Monday into Tuesday which will trend
temperatures near to or just slightly below normal for the middle
of next week with highs in the upper 50s to middle 60s. Depending
on cloud cover Wednesday morning looks to be the coldest morning
over the next week with lows in the low to middle 30s across the
Northwoods to the upper 40s along the lakeshore. Will continue to
monitor this period for potential frost/freeze headlines.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1023 PM CDT Wed Sep 25 2024

Mostly clear skies and VFR conditions were noted across the TAF
sites late this evening. Ground fog will be the main concern for
tonight, as cooler temperatures and clear skies allow fairly
widespread fog. The best chance for fog will be across north-
central Wisconsin and near the Lake Michigan shoreline, so the
lowest visibility forecast was included for these areas.
Conditions in the fog could drop as low as IFR/LIFR at times.

The fog should mix out a few hours after sunrise, with good
visibility and flying conditions expected the rest of the day on
Thursday.

&&

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

&&

$$

DISCUSSION.....Kieckbusch/GK
AVIATION.......Kurimski