Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 180001
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
601 PM CST Fri Nov 17 2017

Updated aviation portion for 00Z TAF issuance

.UPDATE...
Issued at 509 PM CST Fri Nov 17 2017

Area of weak elevated instablity ahead of approaching cold front
and weak shortwave impulse has contributed to some isolated
thunderstorms over the Fox Valley from near Appleton south to Fond
du lac. Thunder should be short-lived perhaps the next hour or
so. Updated short-term grids accordingly.
&&

.SHORT TERM...Tonight and Saturday
Issued at 220 PM CST Fri Nov 17 2017

The main forecast focus remains on precipitation type for tonight
as WAA ongoing changes to CAA behind the passage of a cold front.
Still anticipate some kind of mix across the north this evening
and into central WI after midnight.

The 19z MSAS surface analysis showed the cold front stretch from
western Ontario southwest to the central Plains where an area of
low pressure was situated (north-central KS). Gusty south winds
ahead of this front had pulled deeper moisture northward into WI
this afternoon and light rain had broken out over much of the
region. The only exception was far north-central WI where
temperatures hovered at or slightly above freezing and a mix was
still ongoing (rain/freezing rain/sleet).

A messy forecast is expected across northeast WI tonight as the
initial surge of WAA late this afternoon/early evening is replaced
by the onset of CAA behind the passage of the cold front. The
ongoing concern was the potential loss of ice crystals which would
bring freezing drizzle possibility into play over northern WI.
However, some forecast soundings did show that enough moisture
would hold through the column tonight such that precipitation
type would be either rain, snow or a mix as temperatures fall
below freezing. After collaboration with DLH and MQT, have decided
to keep the drizzle/freezing drizzle in the forecast after
midnight across the north due to some drying in the lower levels
of the atmosphere. Central WI would see mainly rain this evening,
then mix with snow at or shortly after midnight, eventually to all
snow toward daybreak. East-central WI would remain all rain
through the night. Min temperatures to range from the middle to
upper 20s north- central WI, to the middle 30s east-central WI.

Steady CAA overspreads WI on Saturday as the bulk of the
precipitation should be to our south and east. That being said,
have kept a small pop across the southeast half of the forecast
area for Saturday morning. Precipitation type would be a mix of
rain/drizzle east, to light snow over portions of central and far
northeast WI. For this entire event, areas away from Lake MI may
see a minor accumulation (one-half inch or less). The arrival of
drier air by Saturday afternoon should bring mixed sunshine,
especially to central WI. An exception would be north-central WI
where weak lake effect snow showers are possible through the day.
Do not see much in the way of diurnal warming (CAA), thus max
temperatures to only make the lower 30s north-central, to around
40 degrees east-central WI.

.LONG TERM...Saturday Night Through Friday
Issued at 220 PM CST Fri Nov 17 2017

The long term forecast remains fairly calm, with all the active
weather in the short term. Lake effect showers will be present
Sunday before winds shift and again on Tuesday into Tuesday night
as a clipper system passes through the region.

Winds will diminish overnight Saturday into Sunday as colder
temperatures in the teens and middle 20s move into the region. A
few snow showers will remain in the north over Vilas county
throughout the day on Sunday, while partly cloudy conditions
remain elsewhere. Temperatures on Monday will pick back up into
the 40s with southerly flow. A lack of moisture should keep skies
mostly sunny and active weather out of the region. Tuesday a
passing clipper system will bring back northwesterly winds, colder
temperatures towards the midweek, and a chance to see some more
lake enhanced snow showers in northern Wisconsin. Dry conditions
then follow into Thanksgiving.

Temperatures will be just a few degrees below normal on Sunday,
well above normal on Monday, and then return closer to seasonal
values through the rest of the week after the cold front passes on
Tuesday.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 600 PM CST Fri Nov 17 2017

A cold front will continue to push east across the Fox Valley and
lakeshore areas during the late evening with a wind shift to the
north-northwest. Rain showers ahead of the front will gradually
become less numerous by midnight followed by areas of drizzle
until about daybreak Saturday. Cigs/vsbys will continue to lower
this evening with most locations reaching IFR conditions for most
of tonight. As colder air overspreads the region later tonight,
the light rain and drizzle is expected to mix with light snow or
even some patchy freezing drizzle across northern and central WI
as drier air aloft pushes in behind the front. The GRB/ATW/MTW TAF
sites should remain warm enough to sustain all rain through the
night. Some lingering light rain or drizzle may carry over into
Saturday morning over eastern WI, but a drying trend will be noted
for the rest of the day. Cigs are forecast to rise to MVFR during
the morning and reach VFR conditions by Saturday afternoon.
&&

.MARINE...
Issued at 220 PM CST Fri Nov 17 2017

Gusty south winds are expected to diminish this evening ahead of
an approaching cold front. This front will sweep across Wisconsin
tonight and as a low pressure system tracks through the Great
Lakes on Saturday, a few gale force gusts are possible as
northwest winds rev up Saturday morning and continue into at least
Saturday evening.
&&

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

$$

UPDATE.........ESB
SHORT TERM.....Kallas
LONG TERM......Uhlmann
AVIATION.......ESB
MARINE.........Kallas



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