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FXUS63 KGRB 251706

Area Forecast Discussion
National Weather Service Green Bay WI
1106 AM CST Sat Feb 25 2017

Updated aviation portion for 18Z 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 

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 18Z TAF Issuance
Issued at 1054 AM CST Sat Feb 25 2017

Snow showers and flurries will diminish this afternoon as low
pressure moves away from the region. A brief period of clearing
will then push in from the west from late this afternoon into this
evening, before additional clouds arrive from the west ahead of a
weak clipper. These clouds should lower overnight into low mvfr
range over central and north-central WI, with potential for
scattered light snow flurries/showers. Scattered snow showers will
likely persist across northern Wisconsin for much of Sunday with
arrival of a cold front, and possibly push into the Fox
Valley/Lakeshore areas during the morning. IFR visibilities will
be possible within any snow showers.




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