Area Forecast Discussion
Issued by NWS Green Bay, WI

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098
FXUS63 KGRB 181748
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1248 PM CDT Fri Aug 18 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Saturday
Issued at 327 AM CDT Fri Aug 18 2017

Cloud trends today into this evening and small precipitation
chances late today the focus of this period.

Satellite imagery shows plenty of clouds over the state early this
morning in the cyclonic flow, with a few temporary holes opening
up over parts of eastern Wisconsin at times. As the system pulls
away today into this evening, anticipate some decrease in clouds
from southwest to northeast. However how much of a decrease in the
clouds today is a challenge due to weak pieces of energy in the
northwest flow over the northern plains may work into parts of
western or southwest wisconsin later this afternoon and evening,
and may reach central areas as well. Mid to high level clouds
arriving from the west and surface dewpoints in the upper 50s
creating cu rule parameters in the broken category may keep clouds
around. Steep low level rates and up to 200 J/kg CAPES today
suggests the potential of minor convection. Will leave the
forecast dry for now due to the coverage may be too small, but
will brief the next shift of the possible need for a small pop for
later today.

What clouds hang around this evening will be on the decrease
tonight as the upper ridge builds into the Western Great Lakes
region and surface high pressure area settling over the area.
Clearing skies tonight along with surface dewpoints still in the
55 to 60 range, combined with lighter winds, may lead to fog
formation overnight. Weak southwest flow Saturday will bring
warmer temperatures along with more sunshine.

.LONG TERM...Saturday Night Through Thursday
Issued at 327 AM CDT Fri Aug 18 2017

Dry conditions are expected across the region Saturday night into
Sunday as high pressure remains in place across our area. A warm
front will bring active weather to the region in the evening on
Sunday and through the overnight hours. A few strong thunderstorms
will be possible in western Wisconsin as convective temperatures
are reached, but with little upper level support, currently expect
storms to quickly diminish overnight to showers.

Better upper level support arrives for Monday as a shortwave
moves through the region with the passage of a cold front.
Its too early to comment heavily on severe potential, as outflow,
cloud cover, and potential showers from Sunday will play a role in
determining how things shape up Monday. That said, models continue
to place high moisture values into the region ahead of this system
so heavy rainfall is likely.

Following the active weather early in the week, northwesterly
flow and mostly dry conditions return to region ahead of the next
upper level ridge. Temperatures through the period will trend
higher than normal Monday before coming closer to normal by the
end of the week.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1243 PM CDT Fri Aug 18 2017

Weakening cyclonic northwest flow and daytime heating will cause
MVFR ceilings to rise to VFR by 19z-20z. As low clouds erode,
they will likely be replaced by mid-level clouds associated with
a short-wave trof. This trof may produce a few light showers
or sprinkles in central WI in the late afternoon or early evening,
but will not mention any rain in the TAFs. Clearing is expected
to occur overnight, which should allow some fog to develop,
especially in the favored locations of north central WI. The fog
should mix out by 14z/Sat.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....TDH
LONG TERM......Uhlmann
AVIATION.......Kieckbusch



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