Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 101934

Area Forecast Discussion
National Weather Service Green Bay WI
234 PM CDT Tue Oct 10 2017

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Wednesday
Issued at 233 PM CDT Tue Oct 10 2017

The latest RAP analysis and satellite/radar imagery show low
pressure spinning over the central Mississippi Valley, and a
Canadian high pressure from the northern Great Lakes to the west-
central Great Plains. Rain showers from the surface low are
lifting northward over eastern Iowa and western Illinois, but are
running into dry air emanating out of the high to the north. Mid-
level clouds are beginning to move into central WI early this
afternoon, and this increasing cloud trend will continue for the
rest of the day. As the low pressure moves northeast, precip
chances and trends are the main forecast concerns.

Tonight...The low pressure system will track across central
Illinois and Indiana. Central and northeast Wisconsin will be on
the northern periphery of the system, with a continued feed of low
level dry airmass from the northeast. This may hold off precip for
a while, but should see enough push of moisture for precip chances
to ramp up over central to east-central WI early to mid-evening.
Have increased pops based on more bullish model solutions. Areas
south of Wisconsin Rapids to Kewaunee will stand the highest
chance of rainfall. The precip will likely pull out of central WI
late tonight. Farther north, will see an increase of mid-level
clouds during the evening, but dry air is too entrenched for
precip. Low temps will range from the low 30s north to near 50

Wednesday...Any lingering shower activity is expected to exit
east-central WI early in the morning. Then high pressure will
reassert itself for the rest of the day. Will likely see more
clouds linger over central than northern parts of the state. Highs
ranging from near 60 in the north to mid 60s south.

.LONG TERM...Wednesday Night Through Tuesday
Issued at 233 PM CDT Tue Oct 10 2017

The main forecast concern will be precipitation trends, and
the potential for heavy rain and thunderstorms, over the weekend.

Expect a period of quiet weather from Wednesday night through
Thursday night. Precipitation will return Friday into Friday
night, as light to moderate post-frontal rain develops in the
wake of a cold frontal passage.

Models are coming into better agreement with the timing and track
of a surface low that lifts northeast along the lingering frontal
boundary over the weekend. Both the GFS and ECMWF track the low
through southeast WI Saturday night, before taking it into the
eastern Great Lakes Sunday evening. This system will have fairly
potent dynamics, plus PWATs around 1.5 inches and some elevated
instability over our southeast counties. Current indications are
that rain will overspread the area during the late afternoon and
evening on Saturday, becoming heavy at times over parts of central
and east central WI Saturday night before gradually tapering off
Sunday afternoon or evening. Have added a slight chance of
thunderstorms to the southeast portion of the CWA Saturday night.

Quiet weather returns for the early part of the work week.

Temperatures will warm to above normal late in the work week,
return to near normal over the weekend, then moderate a bit
again toward the end of the forecast period.

.AVIATION...for 18Z TAF Issuance
Issued at 1040 AM CDT Tue Oct 10 2017

Mid level clouds will increase from south to north later this
afternoon and into tonight as a low pressure tracks through the
Ohio Valley. The northern TAF sites should remain mostly clear,
however, rain showers are possible over the Fox Valley and MTW
taf sites during the mid-evening through late tonight. Despite
the rain, conditions are expected to remain VFR due to abundant
dry low level air. Skies will clear early Wednesday morning behind
the system.



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