Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 171952
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
252 PM CDT Mon Apr 17 2017

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Tuesday
Issued at 252 PM CDT Mon Apr 17 2017

An upper level disturbance was moving across the region this
afternoon. Isolated showers were noted from Shawano and Waupaca
counties east to the lake shore. The shower activity should end
by late afternoon as they move east out over the lake.

For tonight, skies will be partly to mostly cloudy this evening,
then turn mostly cloudy again late tonight as the next system
approaches from the west. Did not stray far from guidance and
previous forecast for lows tonight as the previous forecast
seemed reasonable.

Cold front moves into the region Tuesday afternoon. Total totals
around 45C, lifted indices around 0C and mid level lapse rates
around 6 C/KM still supported a slight chance of thunderstorms.
Best dynamics lifting to the north of the area, and the Canadian
model splits the rainfall across our north and over our southeast
counties. Went likely chances for rain across the north where it
will be closer to the better dynamics and a chance across the
south with the cold front. High temperatures across the north and
west a little tricky depending on how quick precipitation arrives
late Tuesday morning. Trended lower on high temperatures across
the north due to thicker cloud cover and rain, and raised
temperatures across the east where rain won`t arrive until the
afternoon hours. The main story will be the wind. Wind gusts of
30 to 40 mph are expected. Winds are a little stronger on
the GFS bufkit soundings, thus midnight shift will need to
monitor winds and may need to bump them up a little.

.LONG TERM...Tuesday Night Through Monday
Issued at 252 PM CDT Mon Apr 17 2017

Precipitation trends, QPF amounts and potential for snow
accumulations over northern WI Wednesday night through Thursday
night, are the main forecast concerns.

A cold front will move through the forecast area Tuesday evening,
but only scattered showers are anticipated, as the best dynamics
shift north, and best instability stays south. Have removed the
thunder chances across our southern counties Tuesday evneing.
After the front clears the region, a brief period of dry weather
is expected overnight into Wednesday morning.

A more significant low pressure system is expected to arrive
late Wednesday, and linger through Thursday evening. The GFS
and ECMWF have come into better agreement, with a surface low
that tracks farther northwest, through southern WI, Wednesday
night into Thursday. This system will have ample moisture to
and dynamics, so likely to categorical pops and significant
QPF are anticipated. There is also the potential for at least
minor snow accumulations over northern WI late Wednesday night
into Thursday morning. Will start with accumulations of a half
inch to an inch for now, but these may need to be raised a bit.
Winds may also gust to around gale force late Wednesday night
into Thursday morning. Precipitation should taper off Thursday
evening.

Generally dry conditions are anticipated for the rest of the
extended period.

Aside from below normal temperatures on Thursday, temperatures
are expected to remain near normal levels for the remainder of the
extended period.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1218 PM CDT Mon Apr 17 2017

An upper level disturbance will bring a chance of showers to
northeast Wisconsin through mid afternoon. Did not include them
in the 18z tafs as the showers should miss the taf sites. Otherwise,
there are areas of IFR/MVFR cigs across far northeast Wisconsin
early this afternoon which will continue through much of the
afternoon. Attention tonight turns to increasing low level
wind shear from the south/southeast at 30 to 40 knots. Have
included this scenario in the latest issuance of the tafs.
On Tuesday, it will be windy by mid to late morning as the
pressure gradient increases ahead of the next cold front.
Gusts of 25 to 35 knots are likely. Showers will move into
north-central Wisconsin by late morning, and then across
the rest of the region during the afternoon. A thunderstorm is
also possible. The system departs the area Tuesday evening.
&&

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

$$

SHORT TERM.....Eckberg
LONG TERM......Kieckbusch
AVIATION.......Eckberg



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