Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 241726

Area Forecast Discussion
National Weather Service Green Bay WI
1126 AM CST Fri Feb 24 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Saturday
Issued at 335 AM CST Fri Feb 24 2017

Much anticipated winter Storm working into the area this morning.
Forecast challenge today into tonight centers on any adjustments
to ongoing headlines. As of the forecast issuance, no changes
needed to the headlines, but changes later this morning or today
not ruled out due to the convective elements with this system.

Early this morning...area radars show plenty of convection noted
over southern Wisconsin into the developing southern edge or
deformation area over Iowa and Nebraska. At 200 am, the south edge
of the convection over southern Wisconsin was near the
Wisconsin/Illinois border and gradually diminishing. A larger area
of convection will be sliding over southeast Wisconsin before 4am
and may brush areas east of the Fox River toward Manitowoc. Web
cams show snow sticking to the ground over east central Wisconsin,
and will need to closely watch to see if the advisory will hold
with these convective elements working into the area, or a warning
will be needed this morning. These convective elements were
moving fairly quickly, but were producing inch per hour snows. As
of 2 am, snow amounts mainly were around 2 inches over areas south
of a line from Wausau to Green Bay. Warming height 700 mb
temperatures over east central wisconsin this morning should start
to turn the snow to more of a snow mix to hold amounts down.
While precipitation is diminishing over eastern Iowa, the dry slot
not impressive at this time.

Other concern is the consensus model track of the 850 low is a
little more southeast, which would support the deformation band of
snow more southeastward as well. Southern edge band of snow
downstream into Iowa/Nebraska is being masked by the convection
sliding northeast over iowa and southern minnesota. Early
extrapolation analysis suggests extending into north central
Wisconsin today, but confidence with this is low due to colder air
working into the region. Higher snow ratios confined over central
and northcentral wisconsin with the colder air settling in.

As far as pcpn types, mainly snow reported over the forecast area
early this morning with rain and isolated thunderstorms over
southern wisconsin. Forecast soundings suggest some mixing with
or changing to sleet for a period of time this morning over east
central wisconsin. Freezing rain or freezing drizzle possible
later on if the dry slot can work into the area later today.
Continued cooling will turn precipitation to all snow late today
into tonight.

Storm system departs northeast of the area late tonight into
Saturday for a snow from southwest to northeast, with the
exception of lake effect snow showers far north.

.LONG TERM...Saturday Night Through Thursday
Issued at 335 AM CST Fri Feb 24 2017

As the surface system and mid level trough currently impacting the
area move away from the state, a weak low and mid level short
wave will approach from the west-northwest. 00Z models differed
in their handling of the surface system and associated QPF for
late Saturday night and Sunday. The blended solution showed only
minimal amounts of precipitation, so there is only a dusting of
snow in the forecast across the north, for now.

Short wave energy moving into the region in advance of a broad
upper trough, along with a surface low, will bring precipitation
chances back to the southern part of the forecast area starting on
Monday night. Models still showed significant differences in the
strength and placement of the low, but were a bit closer than they
were 24 hours ago. The blended solution kept a chance for
precipitation across the area through Tuesday evening. Looks like
mainly rain during the daytime and snow at night, with some mixed
rain and snow as precipitation type changes. Cold cyclonic flow
behind the departing system will keep a chance for snow across at
least part of north central Wisconsin through Wednesday night.
After that, an approaching clipper will bring snow chances to
most of the area starting on Thursday.

Near normal high temperatures are expected for Sunday, with a
slight warming trend into Tuesday followed by a slight cooling
trend through Thursday.

.AVIATION...for 18Z TAF Issuance
Issued at 1126 AM CST Fri Feb 24 2017

Surface low pressure is forecast to track into Lower MI this
afternoon, before lifting into southeast Ontario tonight. Expect
primarily MVFR cigs/vsbys to continue through tonight as either
snow or a wintry mix this afternoon changes to all snow across the
entire region tonight. In addition to the precipitation, windy
conditions are expected especially at the GRB TAF site as winds
funnel down the bay where gusts will approach 40 knots and may
briefly restrict vsbys to IFR category. These winds are forecast
to weaken a touch tonight into Saturday, but remain gusty. The
precipitation will gradually diminish from west to east on
Saturday as a ridge of high pressure builds into the region. VFR
conditions should return Saturday morning and continue into
Saturday night.

Winter Weather Advisory until 6 AM CST Saturday for WIZ013-

Winter Storm Warning until 6 AM CST Saturday for WIZ005-010>012-


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