Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 121648
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1048 AM CST Tue Dec 12 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 343 AM CST Tue Dec 12 2017

Snow showers and flurries should end by midday as a surface ridge moves
across the area. Gusty northwest winds across the Door Peninsula will
also diminish by midday. Temperatures today will be around ten degrees
below normal. At least some clearing is expected this afternoon before
middle and high clouds return tonight ahead of the next clipper system.

The clipper system looks like is has more potential to produce significant
snow than the last couple of systems. This one has a coupled upper jet,
is moving slower, has better low level warm advection and convergence
and should have a better trajectory for winds coming across Lake Michigan.
The models all suggest that 3 to 5 inches of snow are likely over much
of the area Wednesday, with some potential for six inches or more south
and east of Green Bay. Winter Weather headlines will likely be
issued later today.

In addition to the snow, gusty northeast winds will produce some blowing
and drifting snow in the Lakeshore and Fox Valley Wednesday afternoon
and evening.

.LONG TERM...Wednesday Night Through Monday
Issued at 343 AM CST Tue Dec 12 2017

500mb ridge across western North America with a resulting downstream
trough across eastern North America will will dominate the weather
pattern into the weekend. The pattern should gradually flatten next
week. This pattern will bring periodic chances of light snow with
clipper systems dropping southeast out of Canada. Behind the
departing systems, lake effect snow showers are possible at times
across far northern Wisconsin. Temperatures should run at or below
into the weekend, then temperatures may return to or slightly
above normal early next week.

The first clipper system will bring a chance of light snow or
flurries to portions of northeast Wisconsin Wednesday evening.
Any additional accumulation should be less than an inch. Across
the north, the chances of lake effect snow showers will linger
into Thursday morning. Another weak upper level disturbance will
bring a chance of light snow or flurries to north-central and
central Wisconsin later Thursday afternoon, then across northeast
Wisconsin Thursday night. The chances of lake effect snow showers
increase through the night Thursday night and continue into
Friday.

Attention turns to another clipper system Friday into Saturday.
Low confidence in timing and location of this system based on the
different model solutions. Otherwise, night time lows should stay
above zero across the north during the period based on expected
wind and cloud cover. If we should get a night with light winds
and clear skies, temperatures may need be lowered at least 10
degrees. A clipper system passing to the north of the area early
next week should usher in milder air across the region Monday.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1048 AM CST Tue Dec 12 2017

Northwest to southeast band of lower end VFR or higher end MVFR
cigs will slowly diminishing this afternoon as a surface high
pressure ridge slides overs. What clearing occurs, mid level
clouds will be on the increase this afternoon and evening as a
clipper system approaches. Conditions will deteriorate overnight
to IFR levels as snow spreads over the area. These conditions are
expected to continue through much of Wednesday.  Latest data
suggests a swath of snow of 3 to 5 inches over central and east
central Wisconsin.
&&

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

$$

SHORT TERM.....RDM
LONG TERM......Eckberg
AVIATION.......TDH


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