Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 191736

Area Forecast Discussion
National Weather Service Green Bay WI
1236 PM CDT Tue Sep 19 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 300 AM CDT Tue Sep 19 2017

A weak mid level short wave will continue to slide northeast of
the area this morning to diminish or end the isold showers.
Showers were also aided by mid level warm air advection ahead of a
deeper trough dropping into the Northern Plains today into this
evening. Showers and storms will be on the increase from west to
east tonight with the increasing LLJ ahead of the northern plains
trough and cold front.

The cold front passage arrives Wednesday with continued chances of
showers and storms. Due to ideal timing of the cold front in the
afternoon and evening, some potential for strong to severe storms.
MU cape values reach 1500 J/kg above an eroding cap in the
afternoon over eastern Wisconsin. Total totals climb into the mid
50s early evening over eastern WI. Shear values range from 30-40
kt shear, with a brief period of a deeper layer shear in the
evening as the upper jets lifts northward over the Northern Plains
and far northeast area of the Great Lakes.

Southeast surface winds will keep lake michigan temperatures in
check but above normal temperatures continue today with some
slightly cooler readings for Wednesday due to more clouds and

.LONG TERM...Wednesday Night Through Monday
Issued at 300 AM CDT Tue Sep 19 2017

The lack of warmth in August will be made up this week with
temperatures by the weekend some 10 to 20 degrees above normal.
Temperatures early next week will return closer to seasonal
normal which by this time will be in the middle to upper 60s.

Several chances of thunderstorms are in the forecast. A cold
front moving across the region Wednesday afternoon evening
will trigger scattered thunderstorms. A few of these storms
could be strong or possibly severe into early Wednesday evening.
The cold front will clear the area by later Wednesday night,
bringing an end to the rain. High pressure will move across
the region on Thursday. Return flow on the backside of the
high pressure system may trigger a shower or thunderstorm
across the far north Wednesday night, thus warranting a
small chance of rain.

The next chance of showers and thunderstorms will be on Sunday
into Monday. Low confidence in the chance of showers and storms
on Sunday, as hurricanes Jose and Maria spin off the east coast
of the United States. This scenario will probably slow down the
weather pattern until the move away from the United States.

The main story will be the increasing heat and humidity by the
end of the week into next weekend. Highs Friday through Sunday
will be in the 80s, with a few locations approaching 90 on Friday
and Saturday. Temperatures will return closer to normal early next

.AVIATION...for 18Z TAF Issuance
Issued at 1236 PM CDT Tue Sep 19 2017

Most of the area was free of clouds at 17Z but MVFR ceilings
lingered in parts of eastern Wisconsin where light easterly winds
prevailed and dew points were mostly in the lower 60s. Visible
satellite imagery showed a decrease in the clouds over the east
so would expect VFR conditions by late afternoon or early

Models had IFR ceilings moving into central and north central
Wisconsin tonight in southeast surface flow. The rest of the area
should see some MVFR, and possibly IFR, fog overnight. Showers
will move into central and east central Wisconsin from the west
on Wednesday morning. Did not include thunder at this point, but
by later in the day there is plenty of instability ahead of an
approaching cold front so showers and thunderstorms will spread to
the east later in the afternoon.



LONG TERM......Eckberg
AVIATION.......MG is the U.S. government's official web portal to all federal, state and local government web resources and services.