Area Forecast Discussion
Issued by NWS Green Bay, WI

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753
FXUS63 KGRB 202343
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
543 PM CST Mon Feb 20 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Tuesday
Issued at 300 PM CST Mon Feb 20 2017

Cloudy cover and southeast winds continued this afternoon. Showers
were just now approaching central Wisconsin. Temperatures were
mainly in the upper 40s to middle 50s, cooler by the bay and lake.
It appears that one record high was set or tied at Wisconsin
Rapids.

Showers and a few thunderstorms will move across the region,
ending from west to east overnight. Hourly temperatures tricky
as they may rise some this evening across eastern Wisconsin where
winds will turn to the south and then southwest away from the
colder waters of Lake Michigan and the bay of Green Bay. It is
not every day you forecast lows in the middle to upper 40s which
is expected across east-central Wisconsin. There will be low
clouds and fog once the rain ends.

Low clouds and fog will linger early Tuesday morning, then skies
will become mostly sunny. Since numerical guidance has been
performing on the cool side of late, went above guidance for
highs in the upper 50s to middle 60s. If clouds clear out early,
high temperatures may be still a little cool as 925mb would
support highs well into the 60s.

.LONG TERM...Tuesday Night Through Monday
Issued at 300 PM CST Mon Feb 20 2017

Quite the dichotomy emerges with this forecast as we go from the
potential to hit the all time record high for February, to a
significant snowstorm all in the same week.

The forecast starts out with a low pressure system tracking
through the western Great Lakes region. Ahead of the low
temperatures will soar into the lower to middle 60s across central
and east-central Wisconsin. Model soundings support these
temperatures as the area mixes to 925 mb with temperatures around
10 celsius at this level. Further north highs are expected to be
limited to the 50s with additional cloud cover and afternoon rain.

This front will bring a stalled out cold front across Wisconsin on
Thursday, as a cooler airmass limits highs to the upper 30s to mid
40s. A strong low pressure system developing across the plains
will track northeast towards the western Great Lakes Friday and
Saturday. The system still has a lot of questions associated with
it as model soundings indicate a dry slot could introduce freezing
rain with a warm layer putting sleet in play as the low tracks
through the area. The other issue is the timing as the ECMWF is
more progressive while the GFS and Canadian are slower as the low
occludes across the western Great Lakes region. Despite the model
differences, they seem to be converging on producing a swath of
heavy snow north and west of the Fox Valley, with central and
north-central Wisconsin being the hardest hit areas. The Fox
Valley and areas east to the lakeshore are more likely to see a
wintry mix of precipitation and even rain at times, which will act
to hold down snowfall totals across these areas. This comes with
an important caveat that a shift in the track would completely
change this scenario, so a close look at future updates is
encouraged. Behind this low a cooler airmass will bring
temperatures down to near normal with fairly quiet weather for the
second half of the weekend into the early part of next week.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 542 PM CST Mon Feb 20 2017

mainly IFR conditions overnight with light to moderate
rain and low level wind shear with winds around 50 knots at 1000
ft agl. The rain should end around daybreak with conditions
becoming VFR by afternoon as a weak front moves by.
&&

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

$$

SHORT TERM.....Eckberg
LONG TERM......Kurimski
AVIATION.......RDM



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