Area Forecast Discussion
Issued by NWS Green Bay, WI

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939
FXUS63 KGRB 171705
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1205 PM CDT Tue Apr 17 2018

Updated aviation portion for 18Z 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 18Z TAF Issuance
Issued at 1155 AM CDT Tue Apr 17 2018

MVFR CIGS will give way to VFR CIGS this afternoon across northern
Wisconsin. Northwest winds of 10 to 20 knots will gradually
diminish this evening. Skies will become clear to partly
cloudy for awhile, then mid and high clouds will be on the
increase later tonight and Wednesday as next weather maker
approaches from the west. Light snow is expected to arrive
across central Wisconsin late Wednesday morning and then
could become moderate at times Wednesday afternoon into
early Wednesday evening across central and east-central
Wisconsin. Very sharp gradient in the snowfall totals are
expected. KAUW/KECS/KGRB could see a dusting to an inch
while KISW/KMFI/KY50/KOSH/KMTW could see 2 to 5 inches
with locally higher amounts near KISW/KY50. Snow should
taper off from north to south Wednesday evening.

&&

.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.......Eckberg
HYDROLOGY......TDH



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