Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 211652

Area Forecast Discussion
National Weather Service Green Bay WI
1052 AM CST Tue Feb 21 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 313 AM CST Tue Feb 21 2017

North to south band of light rain will continue to drift eastward
over eastern Wisconsin this morning. A few showers may linger
along the lakeshore a few hours longer after daybreak. Otherwise
drier air on westerly winds will move into the area. Forecast
challenge turns back to max temperatures today. Much of the area
will get a warm start this morning with anticipated sunshine by
this afternoon. Satellite imagery shows a large area of stratus
from northern Minnesota into the northwest half of the state.
Observations over the southeast half of the state show mid level
clouds with the departing light rain. With westerly winds, these
low level clouds may attempt to drift eastward over the area this
morning. Forecast sounding suggests subsidence mixing with dry air
aloft will diminish the low clouds today, so will continue to go
with the current forecast of returning sunshine today. Depending
on cloud trends, temperatures could be adjusted either way.

Mid level clouds over the northern Plains this morning will be on
the increase over northwest Wisconsin late today into tonight.
These clouds are associated with a weak short wave with frontal
system to slide over tonight into Wednesday. A couple of showers
are possible across the north with this system. Forecast max
temperatures will continue to be above normal, but northern areas
may be held in check a bit depending on clouds again.

.LONG TERM...Wednesday Night Through Monday
Issued at 313 AM CST Tue Feb 21 2017

Model differences and their impact on an approaching system for
late in the week are the main forecast concerns.

Some differences among the models were already apparent by the
time this part of the forecast begins. A passing mid level short
wave and a surface low moving through the region will bring a
chance for precipitation to the northern part of the forecast
area Wednesday night. Temperatures should generally be warm
enough for rain, but the rain may change to a wintry mix shortly
before coming to an end. Thursday morning looks to be dry but rain
chances reach parts of central and east central Wisconsin during
the afternoon ahead of the next approaching system.

The 00Z GFS and ECMWF were farther north with the approaching
surface low, taking it across Wisconsin. The 00Z Canadian and NAM
were farther south, taking it across Illinois. The northern path
would bring warmer air into the forecast area, causing precipitation
type issues in parts of central and eastern Wisconsin. It would
also result in the heaviest snow falling farther to the west and
north. After this system passes, much colder air arrives. Highs
should be below normal Saturday through Monday. The colder air
could bring some lake effect snow showers to the far northern part
of the forecast area.

.AVIATION...for 18Z TAF Issuance
Issued at 1048 AM CST Tue Feb 21 2017

VFR conditions expected through Wednesday afternoon. The only
exception may be for some MVFR visibilities due to fog across far
northern Wisconsin late tonight into early Wednesday morning.
Also, low level wind shear around 35 knots from the
south/southwest will develop later this evening and continue
until 14z on Wednesday. The mild weather will come to an end
Thursday/Friday. A significant snow is also possible across
northern Wisconsin Thursday night into Saturday morning.
Stay tuned!




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