Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 182332
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
532 PM CST Sat Nov 18 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Sunday
Issued at 244 PM CST Sat Nov 18 2017

Relatively quiet 24 hour coming up as the one main system heads
toward the northeast CONUS and high pressure builds toward the
Great Lakes. The main forecast concerns to be on lingering lake
effect snow showers over Vilas County tonight and how cool to take
temperatures both tonight and Sunday.

The 19z MSAS surface analysis showed an area of low pressure over
northwest OH, bringing thunderstorms to the Ohio Valley. An area
of high pressure was centered over the northern High Plains. A
tight pressure gradient existed over the Upper Midwest/western
Great Lakes, thus providing for some gusty north-northwest winds.

Light lake effect snow showers will be possible over Vilas County
as delta-T values hover around 20. Negatives for much accumulation
include: low inversion heights, trajectories that are northwest
versus preferred north-northwest and a dry air mass in place (PW
values only 0.15-0.20"). This should keep accumulation numbers at
an inch or less across the favored snowbelt areas of Vilas County.
Otherwise, dry and cold conditions are expected for the rest of
northeast WI under partly to mostly cloudy skies and a steady
west-northwest wind at 10 to 20 mph. Min temperatures to range
from 10 to 15 above north-central Wisconsin, to the middle 20s
near Lake MI.

Any lake effect snow showers or flurries should diminish Sunday
morning as the ridge of high pressure approaches and winds back
more to the west. This surface ridge is forecast to gradually
shift east across WI by Sunday afternoon, keeping dry conditions
in place for the rest of the day. A northwest flow aloft may send
a weak shortwave into the Great Lakes on Sunday, but with a dry
air mass overhead (plus the surface ridge), only some clouds are
expected as sky conditions could range from mostly sunny to mostly
cloudy at times. Even as WAA starts to overspread WI on Sunday,
temperatures will be below normal with readings only topping out
in the middle to upper 20s north, upper 20s to lower 30s south.

.LONG TERM...Sunday Night Through Saturday
Issued at 244 PM CST Sat Nov 18 2017

Northwest upper flow will produce mostly dry and seasonably cold
weather this week. Lake effect snow showers are possible Tuesday
and Tuesday night in Vilas county as an upper system comes by and
a reinforcing push of cold air arrives. The wind direction does
not look favorable for much snow accumulation.

An Alberta Clipper could produce some precipitation Friday or Saturday,
but there are considerable differences in the model track and timing.
The best chance looks to be across northern Wisconsin.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 524 PM CST Sat Nov 18 2017

MVFR ceilings will continue at most locations through late tonight
or early Sunday morning, followed by widespread clearing as a
ridge of high pressure moves into the region. The arrival of drier
air and downsloping northwest winds may cause ceilings in
northeast WI to reach VFR before the clearing occurs. Scattered
lake-effect snow showers will affect Vilas county tonight, and a
mix of rain/snow showers is possible over northern Door county,
otherwise dry weather is anticipated.

&&

.MARINE...
Issued at 244 PM CST Sat Nov 18 2017

Gusty northwest winds will continue tonight into early Sunday
morning. A few gale force gusts are possible through this evening
before winds slowly diminish later tonight. A small craft advisory
remains in effect for the nearshore waters.
&&

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

$$

SHORT TERM.....Kallas
LONG TERM......RDM
AVIATION.......Kieckbusch
MARINE.........Kallas



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