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000
FXUS63 KGRB 151733
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1133 AM CST Sat Dec 15 2018

Updated aviation portion for 18Z TAF issuance

.SYNOPSIS...
Issued at 320 AM CST Sat Dec 15 2018

Mild and quiet weather is expected for the next several days.

The current upper pattern consists of zonal flow across the
Pacific which splits as it enters North America. Gradual
amplification over the Pacific will lead to a more consolidated,
higher amplitude regime downstream over North America by the
middle to latter part of next week. That change isn`t expected to
last long however, as the pattern will trend back toward zonal
during the following weekend.

Temperatures will remain above normal, though there will be a bit
of a cool down early next week. A more sustained trend back
toward normal will begin late in the period. Dry weather is
expected through early next week, then some light precipitation is
likely as an upper trough begins to form over the region in
conjunction with large scale amplification. Amounts for the period
will be below normal.
&&

.SHORT TERM...Today...Tonight...and Sunday
Issued at 320 AM CST Sat Dec 15 2018

The position of the forecast area between the main branches of the
split flow will result in quiet weather.

Frost deposition could result in isolated slick spots on the roads
this morning, so will mention that in the HWO. Some passing
middle and high clouds are expected tonight as the area is brushed
by the tail of a northern stream shortwave migrating across
Canada.

For temperatures, started with a blend of top performing guidance
products and then adjusted for local effects. Lows tonight were
the toughest forecast, as the surface pressure gradient may be
just weak enough to allow winds to drop to calm at times, which
would allow the climatological cold spots to drop substantially
during the calm periods.

.LONG TERM...Sunday Night Through Friday
Issued at 320 AM CST Sat Dec 15 2018

A mid level trough is forecast to pass northeast of Wisconsin
Sunday night/Monday. A ridge over the central CONUS will then move
through the region toward the middle of next week. Dry weather can
be expected with the trough passing to our northeast and the
ridge moving across the area.

Precipitation chances return to the forecast Wednesday afternoon.
Models bring a chance for rain or snow to parts of central and
east-central Wisconsin during the latter half of the day on
Wednesday ahead of a mid level trough and surface cold front, with
just slight chances across most of the rest of the forecast area.

There is a chance for precipitation across most of the area
Wednesday night as the trough and cold front make it to Wisconsin.
Expect mainly snow, but there is a chance for some light rain or
a mix of rain and snow in part of central Wisconsin and from the
Fox Valley east to Lake Michigan during the evening before a
changeover to all snow occurs. Precipitation should start to clear
out of parts of central Wisconsin during the day on Thursday.
Snow may mix with rain across much of the area by early afternoon.
Chances for snow will remain across north-central Wisconsin
Thursday night and Friday in cold cyclonic flow behind the
departing surface system.

Highs should be around 5 to 10 degrees above normal Monday
through Thursday. It should only be a little warmer than normal
on Friday in the wake of the passing cold front.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1028 AM CST Sat Dec 15 2018

Relatively quiet weather through the taf period. A dry cold front
will move across the area tonight. Increasing south winds aloft
will lead to llws developing from late evening through overnight,
mainly over north-central WI. The strengthening pressure gradient
should prevent fog from becoming an issue, but continued mvfr
vsbys over the eastern WI taf sites where winds will be lighter.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS.......Skowronski
SHORT TERM.....Skowronski
LONG TERM......MG
AVIATION.......MPC