Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 132052
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
252 PM CST Wed Dec 13 2017

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Thursday
Issued at 251 PM CST Wed Dec 13 2017

The latest RAP analysis and satellite/radar imagery show low
pressure moving into north-central WI early this afternoon. The
coldest cloud tops and heaviest snowfall rates are occurring over
northeast WI where visibilities are down to 1/4sm at times. East
winds are increasing along the Bay and Lake with gusts to 35
mph. As snow continues to pile up over northeast WI and winds
shift to the northeast, expect blowing and drifting snow to impact
areas into the Fox Valley this afternoon. Added Manitowoc County
to the warning, given a report of 5 inches so far at Mishicot and
winds gusting up to 30 kts on the lakeshore. No additional changes
expected as the snow and snow/blowing snow should keep roadways
in poor shape through the evening commute. The worst conditions
should occur over far northeast WI. Snow/wind trends are the main
forecast concern.

Tonight...Low pressure will continue to move southeast towards
northern Ohio this evening. Hi-res models indicate that snow will
be ending over northeast WI by mid-evening. Winds will remain
gusty through midnight over eastern WI though, so roads may will
likely be slow to improve. Additional accums are projected to be
less than an inch this evening, highest over the lakeshore areas.
Models then insist on rapid clearing taking place from the north
behind the system, particularly for central and east-central WI
overnight. But with winds onshore from Lake Superior there is
potential for clouds to remain broken for the entire night. Lows
ranging from the mid single digits to mid teens.

Thursday...The next clipper will pass across the region, though it
will be considerably weaker and have less moisture to work with
than todays potent system. Still though, should see clouds
increase again in locations which saw clearing tonight. In
addition, moisture looks deep enough for flurries and light snow
showers from mid morning over central WI and midday over eastern
WI to the end of the afternoon. Some areas could see a dusting.
Seasonable with highs ranging from the upper teens to mid 20s.

.LONG TERM...Thursday Night Through Wednesday
Issued at 251 PM CST Wed Dec 13 2017

A weak upper level disturbance will track across the area Thursday
night into Friday, bringing snow showers and flurries to much of
the area, but accumulations will be under a half inch for all but
far north central WI where an inch or two is possible as some lake
effect/enhancement from Lake Superior is expected. Friday looks to
be the coldest day in the period, with highs struggling to get
into the teens in the Northwoods and into the lower 20s in the Fox
Valley.

The chance for flurries or snow showers will continue Friday night
into Saturday, especially across northern WI, as another
shortwave rotates along the western edge of a upper low sitting
over northeast Ontario. Most persistent and heaviest activity will
remain over north central WI as Lake Superior continues to aid in
the snow shower development. Some dry air will get into the mid-
levels on Saturday, leading to the chance of some freezing
drizzle, but confidence not high enough that precip will actually
occur to add to the forecast. Friday night looks to be the
coldest night in the period, with lows below zero possible across
north central WI and single digits above zero across the rest of
the area, away from Lake Michigan.

Models bring another shortwave into the area this weekend, now
focusing more on Sunday, but model differences are significant,
especially between the GEM/ECMWF and the GFS. Models handle both
the system crossing the northern Plains and another system
tracking NE from the southern Plains. The interaction of these two
systems will determine what, if any, precip chances will occur
this weekend into early next week. Temperatures look to return
closer to normal on Saturday, then slightly above normal Sunday
into early next week as the flow turns more W/SW.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1114 AM CST Wed Dec 13 2017

Snow will continue for most area through mid-afternoon, then the
snow will end from northwest to southeast during the late
afternoon or early evening hours. The worst conditions should
occur over northeast WI where increasing northeast winds to 25 kts
will cause blowing and drifting of the snow. Clearing is expected
for a time over all but far north-central Wisconsin overnight.
More mvfr cigs arrive on Thu morning.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM CST this evening for WIZ005-
010>013-018>021-030-031-035>038-045-048-049.

Winter Storm Warning until 9 PM CST this evening for WIZ022-040-
050.

Winter Storm Warning until 6 PM CST this evening for WIZ039-073-
074.
&&

$$

SHORT TERM.....MPC
LONG TERM......Bersch
AVIATION.......MPC



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