Forecast Discussion for GRB NWS Office
FXUS63 KGRB 090501

Area Forecast Discussion
National Weather Service Green Bay WI
1101 PM CST Wed Feb 8 2023

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Thursday
Issued at 245 PM CST Wed Feb 8 2023

Mostly clear skies are expected this evening, which
should allow temperatures to fall fairly quickly where there is
still significant snow on the ground. Clouds will increase again
after midnight and keep temperatures from falling much further
later tonight.

The computer models all forecast a negatively tilted 500mb trough
to lift rapidly northeast from Tulsa at midnight to Milwaukee
around midday Thursday and Lake Huron by Thursday evening. Strong
upper diffluent flow combined with low level warm advection and
Gulf moisture should produce a three or four hour period of
moderate to heavy snow between 10am and 2pm with lighter snow a
few hours before and after.

850mb temperatures are initially above freezing, but should drop
due to evaporative cooling once precipitation begins, and cool
even more due to strong vertical motion during the midday hours.
So there may be some rain mixed in with the snow at the start but
think the precipitation will be mostly snow. The snow will be wet
and heavy and difficult to shovel and plow.

.LONG TERM...Thursday Night Through Wednesday
Issued at 245 PM CST Wed Feb 8 2023

Once Thursday`s system exits the region Thursday evening, a less
active pattern with above normal temperatures is anticipated through
this forecast period.

Thursday night through Friday...As Thursday`s system continues to
exit the region, lingering snow showers will prevail through
Thursday evening. A couple tenths of additional slushy snowfall is
possible through Thursday evening, mainly in east-central and far
north-central WI. Some rain may still mix with the snow as it comes
to an end in east-central WI, but there is still uncertainty with
this as models vary on how quickly the colder air moves into the
region from the northwest. Snow showers will continue in far north-
central WI through Friday morning due to northwest winds generating
lake-effect snow. Gusty northwest winds will gradually decrease
throughout Thursday night and into early Friday morning. Do not
anticipate major impacts from the gusty winds and snow, but cannot
rule out some drifting snow in far north-central WI.

Rest of the extended...A split flow will remain in place for the
weekend and into next week resulting in little chances for
precipitation. Saturday may be gusty due to a tightening pressure
gradient from a clipper tracking north of the region. Models then
indicate a weak shortwave may spark off some rain or snow showers on
Monday, but there are timing and placement differences. Temperatures
will also be above normal through the weekend and into early next
week with high temperatures in the 30s each day.

.AVIATION...for 06Z TAF Issuance
Issued at 1101 PM CST Wed Feb 8 2023

Good flying conditions are expected for most of the region still
overnight, although some patchy fog has developed along the
lakeshore which will affect MTW. Then attention turns to the
approaching winter system from the south, which will bring IFR
conditions for much of Thursday for areas roughly from Escanaba
to Wisconsin Rapids and eastwards. The only change to the forecast
for this system has been a slight shift southeast and a timing
change of a couple hours. Those in the Fox Valley and lakeshore
will likely still see a few inches of slushy accumulation through
the day Thursday, especially for the southern Fox Valley and
eastwards to the Lake Michigan shoreline. Snow will last most of
Thursday but some improvement will already be likely towards the
end of the TAF period Thursday evening. MVFR conditions will be
north and west of the aforementioned line, with some lighter snow
over the day Thursday.

Winter Weather Advisory from 6 AM to 6 PM CST Thursday for


LONG TERM......Kruk

NWS GRB Office Area Forecast Discussion