Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 251109
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
509 AM CST Sat Feb 25 2017

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Sunday
Issued at 302 AM CST Sat Feb 25 2017

Light snow with minor accumulation will linger this morning as
the deformation region of the departing system drifts eastward.
Some patchy freezing drizzle may persist a few more hours along
the lakeshore, otherwise mid levels saturating to produce light
snow. Next issue is timing the end of the light snow today.

Extrapolation of the back edge of the light snow and weakening
deformation area appears to reach around 1130z for central and
northcentral Wisconsin and then departing eastern wisconsin around
15z. Lake effect snow showers may continue across far northern
wisconsin after 12z. Otherwise will let the advisory expire at
12z.

Next issue is forecast min temperatures tonight. Satellite imagery
indicates clearing edge about 4-5 hours in the wake of the back
edge of the light snow, but anticipate breaks to occur before
that. Clouds ahead of weak shortwave trough will begin to spread
over the region tonight. Clear skies, fresh snow, low surface dewpoints
along with light winds with a weak passing surface ridge will
likely produce min temperatures this evening.

Upstream, scattered snow showers already showing up over North
Dakota with this next system. Several progs consistent with a
weak surface boundary stretching over northern wisconsin from a
low pressure sliding over north of the area. Even though guidance
temperatures suggest some mid 30s for max temperatures across east
central and northeast Wisconsin Sunday afternoon, will keep pcpn
type all snow showers due to the cold forecast soundings and steep
lapse rates aloft. Progs indicate total totals approach the lower
to mid 50s Sunday to indicate just how unstable aloft.

.LONG TERM...Sunday Night Through Friday
Issued at 302 AM CST Sat Feb 25 2017

A surface ridge passing across Wisconsin should help to keep the
area dry Sunday night through Monday evening as upper flow becomes
west-southwest with a trough moving into the western CONUS.

Short wave energy in the upper flow, along with an approaching
surface low, will bring precipitation chances back to the area
starting late Monday night. 00Z model solutions were much more
consistent in their handling of this surface system, at least
until Tuesday night when they start to diverge. Warm advection
Monday night is expected to cause precipitation type issues toward
daybreak on Tuesday. Most locations will start out with snow, but
freezing rain and sleet chances generally spread from southeast
to northwest followed by rain, which should cover the entire
forecast area by early Tuesday afternoon. A gradual change to all
snow is expected on Tuesday evening before the snow ends across
central and east central Wisconsin overnight. A clipper system
will move into the region and bring snow chances back to the area
for Thursday into Thursday evening. Some lake effect snow may
persist into Friday morning in north central Wisconsin as this
system departs.

A warming trend is expected into Tuesday, when highs should be
around 10 degrees above normal. Highs on Wednesday will be a bit
cooler, but still several degrees above normal. Temperatures on
Thursday should be near normal, but Highs on Friday look to be at
least a few degrees below normal.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 509 AM CST Sat Feb 25 2017

MVFR cigs and vsbys with light snow will gradually improve to VFR
conditions from west to east this morning. VFR conditions then
expected for the rest of today into this evening with increasing
mid level clouds late evening. There is a chance of light snow
with MVFR conditions late tonight as a weak low pressure system
slides across the northern Great Lakes region. Marginal LLWS
conditions may develop late tonight for part of the area. Will
leave the LLWS mention out of the tafs for now and let later
shifts monitor trends.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM CST early this morning for
WIZ010>013-018>022-030-031-035>040-045-048>050-073-074.

Winter Storm Warning until 6 AM CST early this morning for
WIZ005.
&&

$$

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


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