Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 141700
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1200 PM CDT Sat Apr 14 2018

Updated aviation portion for 18Z TAF issuance

.UPDATE...
Issued at 1027 AM CDT Sat Apr 14 2018

A narrow band about 60 miles wide of heavy snow was noted from
Wausau to Marshfield to Wisconsin Rapids eastward to Green Bay
and Oconto east to the lake including Sturgeon Bay, Fish Creek
and Kewaunee. Snowfall amounts in this band were from 7 to 18
inches. To show how sharp the heavy snow band was, Manitowoc to
Oshkosh to Wautoma received about 1 to 3 inches of snow and sleet.
Meanwhile on the north side of the band, Merrill received 3.7
inches and White Lake 4.6 inches. Little or no snow was reported
across the far north.

The first band of snow from Marinette to Green Bay to Oshkosh east
to Manitowoc and Sturgeon Bay should exit the region around noon.
Meanwhile, scattered snow showers were moving rapidly northward
into central Wisconsin late this morning. Scattered snow showers
should over spread much of the region for the afternoon hours.
Some of the more intense snow showers will produce brief heavy
snow with snowfall rates of 1 to 2 inches per hour and could
produce a quick inch of snow resulting in snow covered and
slippery roads. Motorist can expect poor visibilities below one
mile in the heavier snow showers and at times could be down to a
quarter of a mile or less.

For tonight, the next round of heavy snow will overspread much of
the region. Mixed precipitation is possible from Oshkosh east to
Manitowoc which will continue through much of Sunday.
&&

.SYNOPSIS...
Issued at 523 AM CDT Sat Apr 14 2018

An intense spring cyclone will produce strong winds and
heavy snow through the weekend.

A southern stream upper trough will slowly progress east from the
Plains the next couple days. The initial cyclone with the trough
has occluded and will weaken along the Iowa/Missouri border
today. Redevelopment will occur at the triple point this evening,
with the new low lifting north across Indiana and western Lower
Michigan through Sunday night. That will bring another round of
heavy precipitation to the area.
&&

.SHORT TERM...Today...Tonight...and Sunday
Issued at 523 AM CDT Sat Apr 14 2018

The direct feed of moisture with the warm conveyor belt resulted
in a persistent band precipitation across the area overnight.
Strong lift generated just enough cooling aloft to knock out the
warm layer, and cold dry air flowing in from the northeast kept
the boundary layer AOB freezing across the area (though MTW just
snuck up to 33F). The result was mainly heavy snow with the band,
with reports starting to come into the office indicating 4-8
inches of rather wet heavy snow has already fallen.

Some power outages have been noted south of GRB thus far, but
nothing widespread. Will continue to monitor the OSH area closely
since the ASOS there has had mainly FZRA, and the I-groups
indicate icing is occurring on elevated surfaces. But do not plan
to upgrade to an Ice Storm Warning unless it becomes apparent
conditions will deteriorate considerably from where they area now.

The band has begun to weaken, and that trend should continue. As
usual, the models differed on the specifics, but most showed a
lull in precipitation during the day. We`ve been anticipating
that, and initially expected the later rounds of precipitation
with the triple point cyclone to be main show. But now that we`ve
gotten heavy snow and will maintain the wind, we`ll keep the areas
that were upgraded overnight in a warning through the whole event
and attempt to detail the lull in the specifics of the grids and
our text products. Although significant snow is expected with the
second phase of the system, it is possible it may not fall as
heavily as with the first band. The direct feed of moisture will
be shifting east of the area. So the second phase will be more of
a typical long-duration snow event within the comma head of the
cyclone.

Those areas that were still in the watch at issuance time were
upgraded to warnings for the second phase of the event. The snow
total forecast is tricky, because at some locations it`s hard to
tell what we have so far. Maintained storm total wording for now,
but may need to switch to additional accumulation wording at some
point.

Although the models have underestimated the cold air thus far,
it is still possible the warm layer aloft could drive back
northward some once the lift/precipitation diminishes. So there
is still the potential for a considerable mix at the start of the
second round of the event, especially from ATW/GRB S and E.

.LONG TERM...Sunday Night Through Friday
Issued at 523 AM CDT Sat Apr 14 2018

Remnants of the ongoing winter storm are the main concern during
this part of the forecast.

Precipitation should wind down Sunday night and Monday as the
surface low continues to move away from Wisconsin and the 500 mb
low passes east of the state. There will still be some additional
snow accumulation, mainly in north central Wisconsin where there
could be another 1 to 3 inches of snow. Snow and freezing rain
are possible across the eastern part of the state Sunday night
with some minor ice accumulation. Expect winds to weaken as they
shift north and then northwest Sunday night.

After a brief respite early in the week another system is forecast
to impact the area, but there are timing differences among the
models leading to low confidence in precipitation type. Handled
this with a chance for snow and rain during the middle part of
the week. Expect a warming trend, but it will remain colder than
normal throughout the week.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1157 AM CDT Sat Apr 14 2018

Poor flying conditions are expected across much of the area today,
except the far north. Scattered snow showers are expected this
afternoon with MVFR/IFR conditions expected in the stronger snow
showers. Very poor flying conditions expected tonight into
Sunday evening due to snow and strong northeast winds. Freezing
drizzle possible at times.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until midnight CDT Sunday night for
WIZ020>022-030-031-035>040-045-048-049-073-074.

Lakeshore Flood Warning until 1 PM CDT Sunday for WIZ022-039-040-
074.

Winter Weather Advisory until 7 PM CDT this evening for WIZ018-
019.

Winter Storm Warning from 7 PM this evening to midnight CDT
Sunday night for WIZ005-010-018-019.

Winter Storm Warning from 10 PM this evening to midnight CDT
Sunday night for WIZ011>013-050.

Winter Weather Advisory until 10 PM CDT this evening for WIZ050.

Lakeshore Flood Advisory until 1 PM CDT Sunday for WIZ050.
&&

$$

UPDATE.........Eckberg
SYNOPSIS.......Skowronski
SHORT TERM.....Skowronski
LONG TERM......MG
AVIATION.......Eckberg



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