Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 151911
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
211 PM CDT Fri Sep 15 2017

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Saturday
Issued at 211 PM CDT Fri Sep 15 2017

Mainly dry conditions and above normal temperatures will continue
into Saturday ahead of a Northern Plains frontal system. Forecast
issues will be how much above normal temperatures and small
precipitation chances in the increase warm air advection.

Last night, some very light isolated high base convection drifted
over parts of central and north central Wisconsin before
dissipating mid morning. This afternoon, a nearly stationary
boundary extended across the northern Great Lakes region with the
Lake Superior Breeze reaching into far northwest Wisconsin.
Satellite imagery indicated a bit more high base cu or AC over
northwest Wisconsin and area radars indicate some convection
developing. Will add a chance for storms to north central
Wisconsin through evening due to proximity to the boundary.
Otherwise the main short wave energy was lifting northward over
Minnesota.

For tonight the medium range models remain dry, however a few
meso models develop isolated convection overnight over central
Wisconsin and lift it northward. Upper heights do increase
overnight ahead of the approaching deep trough and lift the
stationary front further north as a warm front. Confidence low of
development with upper heights increasing but will brief the next
shift on the small potential. Will overall continue with the dry
forecast tonight into saturday, then begin to add a mention to
north central areas Saturday afternoon with the approaching
frontal system.

Little change to going max and min temperatures. If clouds arrive
quicker than expected for Saturday, max temperatures will need to
be adjusted down a little over parts of central and north central
Wisconsin.

.LONG TERM...Saturday Night Through Friday
Issued at 211 PM CDT Fri Sep 15 2017

Focus in the long term is on shower and thunderstorm potential
through midday Sunday, and then various pcpn chances through the
week.

Showers and thunderstorms will be at or just about reaching the
western forecast area Saturday evening. Models are in good
agreement that pcpn will enter central Wisconsin between 00Z and
06Z Sunday as a surface cold front moves closer. Storms are
expected to initiate in central/eastern Minnesota earlier Saturday
afternoon along this front, then progress east into Wisconsin.
Higher instability will lead to greater potential for
strong/severe storms in western WI Saturday afternoon. By the time
activity reaches central Wisconsin instability begins to wane,
and the strongest mid and upper level forcing are well to our NW,
making the overall dynamics unfavorable for severe storms. With
that said, some brief gusty winds, heavy rain, or small hail is
possible as the storms enter the area. This threat will also be
decaying through the night.

Models remain in agreement with progressing the cold front to the
southeast Sunday afternoon. Lingering showers should clear
eastern Wisconsin by around 18Z, with drier and cooler air quickly
moving in behind the front. Skies should clear from NW to SE
through the late morning and afternoon. Highs on Sunday will be
cooler than this week, but still a few degrees above normal.

Beyond Sunday, long range models still suggest a trough will
deepen across the western CONUS with a ridge building across the
east. Details vary greatly from model to model and run to run.
Hard to make any modifications to the forecast beyond the blended
solution, which continues to feature on/off pcpn chances through
the week. With the forecast area positioned to be in SW flow
during this time will likely see some disturbances affecting us at
some point, but there will also be ample dry times.

Temperatures will be close to seasonal normals on Monday, then
beginning warming up through the week as mid/upper heights rise.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1137 AM CDT Fri Sep 15 2017

Mainly VFR conditions to continue this afternoon into
Saturday as the region is between high pressure drifting east and
a frontal system slowly approaching from the Northern Plains.
Surface winds have been slow to pick up today and with increasing
925 mb winds to 35 kts tonight, will add a period of low level
wind shear to the TAFS overnight. Even though upper heights
increase tonight, a few of the meso models develop a brief period
of convection over central and north central Wisconsin late
tonight as the LLJ works into the area.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement until 8 PM CDT this evening for WIZ022-
040.
&&

$$

SHORT TERM.....KLB
LONG TERM......TDH
AVIATION.......TDH



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