Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 142259

Area Forecast Discussion
National Weather Service Green Bay WI
459 PM CST Sun Jan 14 2018

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Monday
Issued at 156 PM CST Sun Jan 14 2018

The main forecast concern remains snow accumulation potential
across the entire forecast area tonight through Monday (and

The 19z MSAS surface analysis showed a weak area of low pressure
over northwest MN and strong high pressure over the eastern Great
Lakes/Appalachians. A southerly wind between these two weather
features has brought somewhat warmer air into the region, along
with a deck of low clouds that has overspread all but far eastern
WI. Radar mosaic and ground truth indicated light snow or flurries
had reached western WI at mid-afternoon.

The clipper low pressure is still forecast to dive southeast from
the Upper Mississippi Valley to roughly northern IL tonight,
followed closely by a shortwave trough that will amplify into a
closed upper low. An initial surge of WAA will aid in saturation
late this afternoon/early this evening with light snow over the
entire forecast area by mid-evening. While most locations should
see 2-4" of accumulation by daybreak, the main concern to be the
lakeshore counties as winds back to the southeast later tonight to
add lake enhancement/lake effect to the synoptic snow. This would
raise totals overnight to 2-5" for Manitowoc/Kewaunee counties,
4-8" for Door County. Anticipate temperatures to reach their lows
early this evening, then be either steady or slowly rise through
the night.

The surface low is progged to slow and pivot northeast toward
southern Lake MI or southwest Lower MI on Monday as the closed
upper low settles toward southern WI by 00z Tuesday. During this
process, winds will continue to back and be more east-northeast,
thus easing (a bit) the lake enhancement/effect over Door County.
Nonetheless, there will be a general increase in accumulation
numbers for our lakeshore counties versus inland counties. Models
still show an inverted surface trough extended from the surface
low west-northwest toward west-central WI. Between this feature,
moisture wrapping around the system and shortwave energy moving
around the upper low, light snow will continue over northeast WI
through the day. Accumulation totals between tonight and Monday
are forecast to range from 4-6" inland, 6-8" Manitowoc/Kewaunee
and 7-10" Door County (local 12" possible). Have kept headlines
alone as they appear well-placed. Max temperatures to be in the
15-20 degree range central WI, 20-25 degree range eastern WI.

.LONG TERM...Monday Night Through Sunday
Issued at 156 PM CST Sun Jan 14 2018

Lingering snowfall Monday night will be the first issue during
this period. After a brief period of cold air through mid week, a
a moderating temperature trend is expected for the remainder of
the week with a chance for more precipitation perhaps next

Ongoing headlines will likely be in effect for Monday night as the
storm system slowly departs southeast of the area. Northeast flow
will tend to support continued lake enhanced snows along the
lakeshore. Eventually winds turn more north late Monday night into
Tuesday to end the lake effect snows along Lake Michigan but
increase the potential of Lake effect snows over Vilas County.

Cold Dry air works into area later Tuesday through Wednesday.
Winds turn more westerly to end the Lake effect snows across the
far north.  Moderating trend later in the week may also include
a period of blustery west then southwest winds.

Next chance of precipitation toward next week. Progs are all over
the place with this system, with the latest trend is more south
and perhaps precipitation type will be more snow vs a mix over
parts of central and east central Wisconsin.

.AVIATION...for 00Z TAF Issuance
Issued at 459 PM CST Sun Jan 14 2018

Despite VFR conditions at TAF issuance, conditions will
deteriorate rapidly from west to east this evening as a clipper
system dives south from the Upper Mississippi Valley toward
northern IL. Cigs will quickly lower to MVFR conditions, while
vsbys drop to IFR once the snow develops and remain in these
respective categories for the rest of tonight through Monday.
Vsbys may lower to LIFR over the eastern TAF sites late tonight
into Monday morning as lake enhancement will bring heavier snows
to these locations.

Winter Weather Advisory until midnight CST Monday night for

Winter Weather Advisory from 8 PM this evening to midnight CST
Monday night for WIZ012-013-021-039-049-073-074.

Winter Storm Warning from 8 PM this evening to 6 AM CST Tuesday
for WIZ022-040-050.


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