Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 200020
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
620 PM CST Mon Feb 19 2018

Updated aviation portion for 00Z TAF issuance
and new information added to update section

.UPDATE...
Issued at 607 PM CST Mon Feb 19 2018

Strong isentropic lift will continue this evening as a wave rides
northeast along the baroclinic zone stretched out across the area.
The strongest lift will be focused south of the area, but pockets
of heavier precipitation are likely to continue to clip east-
central Wisconsin at times.

A pronounced lull in the precipitation is likely from late evening
overnight as the LLJ veers and gets focused off to the east. That
will leave mainly FZDZ across the area, which will continue to
result in some icing and hazardous travel conditions.

The primary concern is what happens late tonight and Tuesday
morning as a mid-level shortwave ejecting out of the Plains heads
toward the western Great Lakes region. That will likely result in
increased lift, and another surge of heavier precipitation toward
the area. But it`s not clear whether/how far it will push into
the forecast area, as it could pass through mainly to the
southeast. Temperatures will also be an issue, as some of the
models show the surface front lifting back north toward the area,
or at least a decrease in depth of the cold air. That may allow
enough warming for temperatures to creep above freezing,
especially to the south and east of the city of Green Bay.

Current expectations are that the amount of icing will remain
light enough to cause mainly travel problems (though admittedly
those could be significant at locations where mainly FZRA/FZDZ
occur). However, if the surge tomorrow morning makes it into
east-central Wisconsin and temperatures cannot recover, then a
more substantial build-up of ice is possible and we might begin to
see some damage to tree limbs.
&&

.SHORT TERM...Tonight
Issued at 244 PM CST Mon Feb 19 2018

A mix of snow, sleet and freezing rain was noted across much of
the region. The only exception was across portions of Waushara,
Winnebago, Calumet and Manitowoc counties where air temperatures
were still several degrees above freezing. Road temperatures well
above freezing from Wautoma to Green Bay/Fox Cites east to the
lake. This should change quickly tonight once the sun goes down.
Latest road temperature forecast have road temperatures dropping
below freezing early this evening, thus motorist should anticipate
slick conditions. To the north and west of the Fox Valley, a mix
of snow, sleet and freezing rain was occurring.

For tonight, the steadier precipitation should taper off by mid
evening to freezing drizzle, except across the far north where
some light snow is possible. Some of the latest model guidance
would suggest there could be a few hours where they may be no
precipitation. However, think freezing drizzle will be back on
the increase again late tonight as the next system approaches from
the southwest. Did make some adjustments downward to minimum
temperatures since we were already close to the forecast values.

.LONG TERM...Tuesday Through Monday
Issued at 244 PM CST Mon Feb 19 2018

Starting with the Tuesday period, progs indicate another wave of
mixed precipitation will slide over the area mainly tuesday
morning. Precipitation will be along and ahead of the 850 frontal
boundary sliding over the area. Forecast soundings, another round
of ice accumulation up to 0.10 inches. Trends has been a bit
quicker and its possible later shifts will be able to cancel the
winter weather advisory a bit quicker Tuesday afternoon. Roads may
be a mess from the morning pcpn for another reason to linger the
advisory.

High pressure to settle into the area Wednesday into Thursday for
a period of quiet weather. Models in better agreement with the
timing of the next chance of mainly snow towards Thursday night
into Friday morning as a weak trough slides over the area. Some
trend with a southwest flow aloft developing with upper heights
increasing late next weekend, for a turn to a milder trend.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 607 PM CST Mon Feb 19 2018

Mainly IFR conditions are expected during the next 12-18 hours as
lift continues over the strong frontal zone stretched out south of
the area. Periods of freezing precipitation are also likely,
though it is not expected to be heavy.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM CST Tuesday for WIZ005-
010>013-018>022-030-031-035>040-045-048>050-073-074.
&&

$$

UPDATE.........Skowronski
SHORT TERM.....Eckberg
LONG TERM......TDH
AVIATION.......Skowronski


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