Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 102137
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
337 PM CST Tue Jan 10 2017

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Wednesday
Issued at 337 PM CST Tue Jan 10 2017

There seem to be too many concerns in the short term to pick just
one or two.

Heavy snow was falling this afternoon to the left of an
intensifying surface low pressure system that was passing through
Wisconsin. Some locations in central and north central Wisconsin
reported snowfall rates in the 1 to 2 inch per hour range during
the afternoon. Warm air in east central Wisconsin changed
precipitation to mostly rain for a good chunk of the day. There
was at least isolated thunder in east central Wisconsin to add to
the already active situation. Strong west-northwest winds are
expected in the tight surface pressure gradient in the wake of
the departing low. This may cause some issues with blowing and
drifting snow, especially north and west of the Fox Valley. This
was a major reason for extending winter weather headlines. Winds
in the Fox Valley and Lakeshore areas should be strong enough to
at least reach the low end of wind advisory criteria during the
late afternoon and evening.

The arrival of much colder air will cause any falling rain to
change to snow, and rain that was already on the ground to rapidly
freeze. Precipitation should end during the early evening as the
system quickly departs. Winds are expected to weaken by around
midnight, winter weather and wind headlines, over the land, should
all be gone after that. Clouds and winds will keep overnight lows
from getting colder than the single digits and teens.

There is only a brief respite before snow chances and amounts
enter the picture again. Upper jet dynamics, along with a mid
level trough, will bring a chance for snow to the area starting
Wednesday morning, with snow likely across the north by midday.
12Z model snow amounts differed, and they were not even in total
agreement whether the entire area will get measurable snow. Have
opted to confine the likely pops to the northwest half of the
forecast area, which generally matches the forecast grids from
surrounding offices. HPC guidance suggest that headlines may be
needed for this upcoming event as well.

.LONG TERM...Wednesday Night Through Tuesday
Issued at 337 PM CST Tue Jan 10 2017

There is a big difference to start this forecast period
Wednesday night, depending on which model solution is most correct.
The NAM has been consistent in showing a wave moving northeast
along the surface front across northern Illinois to southern lower
Michigan with a coupled jet structure moving across central and
east central Wisconsin with strong mid level convergence producing
a few more inches of snow. The GFS suggests this as well but to a
lesser degree, while the ECMWF just has some light snow across northern
Wisconsin associated with the right entrance region of the jet. The
NAM seems to have done a better job with this past system so will
side with it for now. After this goes by there could be some light
snow across the southeast quarter of the forecast area early Thursday
as some jet energy moves through. Then dry and colder Thursday afternoon
through Saturday with temperatures 5 to 15 degrees below normal.
Fresh snow will make nights especially cold.

Milder weather looks likely next week as the upper flow becomes
nearly zonal. There could be significant snow or mixed precipitation
at times as some fairly significant upper systems arrive from the
Pacific and move across the Rockies into the Plains states. Highs
should be 5 to 10 degrees above normal.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1148 AM CST Tue Jan 10 2017

IFR conditions will continue across the area through
the evening hours with several aviation hazards.

Moderate to heavy snow will continue west of a STE to IMT line
through the afternoon and snow plows and deicers will be needed.
Blowing and drifting snow will continue tonight. A mixture of
rain and sleet will change to snow before ending further east.

Strong west winds gusting to 40 knots are possible around dusk at
PCZ/CLI/ATW/GRB/OSH/MTW/OCQ/SUE/MNM/EZS with rapid refreezing of
wet surfaces as temperatures drop quickly below freezing.

Winds will diminish and skies clear later tonight but clouds will
increase and snow should return to the whole area by Wednesday
afternoon. The snow should continue Wednesday night.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until midnight CST tonight for WIZ022-038>040-
048>050.

Winter Weather Advisory until 10 PM CST this evening for WIZ037-
045.

Winter Storm Warning until 10 PM CST this evening for WIZ005-
010>013-018>021-030-031-035-036-073-074.
&&

$$

SHORT TERM.....MG
LONG TERM......RDM
AVIATION.......MG



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