Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 171035
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
535 AM CDT Tue Apr 17 2018

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 356 AM CDT Tue Apr 17 2018

The pattern remains active, with the emphasis on the mid week
system and potential headlines.

Cold cyclonic flow continues to produce scattered snow showers
and flurries across the area this morning. The snow showers were
more numerous across the far north. Eventually the snow showers
and flurries will depart to the northeast as the upper low
system shifts east.  Afternoon high temperatures dependent on a
few breaks of some April sun. Satellite imagery showing some
breaks across central and east central Wisconsin early this
morning.

A high pressure ridge settles into the region tonight. With the
widespread snow cover, overnight low temperatures will be at the
mercy of cloud trends. Mid to high level clouds may be on the
increase late tonight with the next weather system approaching
southwest Wisconsin.

Progs are becoming a bit more aggressive with the next system to
track over the south half of the state starting later Wednesday.
A west to east band of snow is possible mainly south of highway
21 or perhaps highway 10. Forecast soundings are indicating a mix
sleet type at the onset Wednesday before turning to mainly snow.
latest snow amounts are indicating an advisory type of snow.
Watch and advisories headlines are already posted for southern
Wisconsin. Later shifts can expand far southern portions of the
forecast area with later trends.

.LONG TERM...Wednesday Night Through Monday
Issued at 356 AM CDT Tue Apr 17 2018

Precipitation Wednesday night is the main focus during this part
of the forecast. Other than that, dry conditions with a gradual
warming trend can be expected through next Monday.

Models showed a 500 mb low, that is forecast to track along the
Wisconsin/Illinois border, starting to move away from the state
Wednesday evening. A surface low will pass southeast of Wisconsin
and be near the East Coast by Thursday morning. The 00Z models
continue with measurable precipitation across the southern part of
the forecast area Wednesday evening and the GFS keeps some near
the shores of Lake Michigan 06Z-12Z Thursday. Looks like another 1
to 2 inches of snow accumulation Wednesday evening and there
could be some light freezing at times in parts of central and
east-central Wisconsin.

Surface high pressure and a mid level ridge should help to keep
the area dry through next Monday. High temperatures should be a
bit warmer each day, but they will still be a few degrees below
normal by Monday.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 535 AM CDT Tue Apr 17 2018

Cold cyclonic flow will continue to produce cloudy skies and
scattered snow showers or flurries this morning. Ceiling heights
will mainly be in the MVFR category across the north and a mix of
MVFR and lower end VFR south. A ridge of high pressure building
into the area later today into tonight will eventually produce
mainly VFR conditions.
&&

.HYDROLOGY...
Issued at 356 AM CDT Tue Apr 17 2018

Forecast conditions through at least Wednesday indicate a gradual
melt of the deep snow pack, actually it will likely be more of a
settling of the snowpack. Some locations south of a Marshfield to
Green Bay line may add to the snow pack Wednesday afternoon and
evening with a system passing over southern Wisconsin. Forecast
temperatures later this week into the weekend appear closer to
normal for a potential of a steadier melt in the daytime, but
overnight lows fall to or below freezing to stop or slow down the
melt. Expect some periods of April sunshine to work on the snow,
however surface dewpoints remain low and after this Wednesdays
weather system, looks mostly dry through early next week. A cold
front dropping over the area next Tuesday may generate up to 0.25
inches of rain. Rivers will eventually respond to the snow melt,
hopefully the runoff will get spread out enough to limit the
flooding potential.
&&

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

$$

SHORT TERM.....TDH
LONG TERM......MG
AVIATION.......TDH
HYDROLOGY......TDH



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