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Area forecast discussion 
National Weather Service Green Bay WI
537 am CDT Wednesday Aug 31 2016

Updated aviation portion for 12z taf issuance

Short Thursday
issued at 312 am CDT Wed Aug 31 2016

Northerly winds will continue to usher in a cooler and drier air
mass into the region from today into Thursday as a surface
Canadian high pressure ridge builds into the region. Surface
dewpoints were already in the mid 40s across the northern Great
Lakes region early this morning. Main focus today through Thursday
centers on cloud trends and the potential of subtle precipitation
chances along the Lake Michigan shore areas.

Satellite shows a band of MVFR clouds associated with a boundary
associated with lower dewpoints and northeast winds from the lake
shifting south of the area. The primary cold front has shifted
well south of the area Tuesday evening. Satellite imagery shows
more widespread clouds just north of Minnesota and Lake Superior
associated with the cyclonic flow around a deeper low over Canada
and colder air working southward. Present rate suggests these
clouds will reach northern Wisconsin late morning. Delta T/S over
Lake Superior may also aid in cloud development across the north.
A mid level trough axis will continue to shift southward along
Lake Michigan with continued cold air advection over Lake
Michigan. As a result will add more clouds...especially with a
diurnal and instability component near the Great Lakes.

Some progs also suggests very isolated light instability showers
near the Great Lakes. Glance at the iwd and mtw forecast
soundings suggests steep low level lapse rates with some small
cape values. Will add a brief period of sprinkles to the Door
Peninsula this afternoon with cooling over the warm waters and
then again toward Thursday morning with the h850 temps cooling to
around 6 degrees, otherwise coverage too low to add to the

Long term...Thursday night through Tuesday
issued at 312 am CDT Wed Aug 31 2016

A pretty quiet late Summer pattern will be in place until late in
the weekend or early next week. With a slower trend of weather
features noted by the previous shift, prefer to lean on the ECMWF,
which also more closely matches the ensemble means.

Thursday night through Saturday night...Canadian high pressure will
be centered across the region Thursday night and Friday. With
mostly clear and calm conditions, will side with the colder guidance
for low temps on Thu night. Plenty of sunshine for Friday with
temps a few degrees warmer than Thursday. The surface high will be
slowly shifting east on Friday night through Saturday night. Surface
winds will become southerly and will be gradually pushing in warmer
air. With any threat of precip remaining west of the region, temps
will return to near normal during these periods.

Rest of the forecast...southwest flow begins to strengthen on
Sunday, but ample dry air should keep the region dry for one more
period. The arrival of low pressure over the northern Mississippi
Valley and more humid air will lead to a chance of showers and
storms returning on Sunday night. Though this low shifts north of
the region for Monday, potential for its cold front along with some
help from shortwave impulses will lead to a shower and thunderstorm
threat for Monday and Tuesday.

Aviation...for 12z taf issuance
issued at 537 am CDT Wed Aug 31 2016

Patchy MVFR/IFR vsbys due to ground fog will persist to around
daybreak, otherwise VFR conditions expected for the start of
today. Clouds will be on the increase from the north today as a
cooler air mass filters over the Lake Superior. Scattered areas of
MVFR cigs may develop across the far north late afternoon and may
persist tonight. These MVFR cigs may spread southward along the
Lake Michigan shoreline or east central Wisconsin overnight.

Grb watches/warnings/advisories...


Short term.....Tdh
long term......mpc

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