Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 301955
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
255 PM CDT TUE AUG 30 2016

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Wednesday
Issued at 255 PM CDT Tue Aug 30 2016

There are several weather factors that need to be dealt with
ranging from extent of any precipitation this evening, how low
temperatures can get tonight and strength of northerly winds,
especially near Lake MI.

The 19z MSAS surface analysis showed a cold front stretched from
central Lower MI southwest into southern WI and continuing into
central sections of IA. Trailing the cold front was a dew point
discontinuity which truly separated the humid air from much drier
air. This discontinuity axis extended from Northern Lake MI
southwest through central WI into southern MN. The radar mosaic
picked up on a line of thunderstorms along the cold front, with
only isolated showers along the dew point discontinuity. Finally,
there was an area of high pressure building into the Northern
Plains.

This dew point discontinuity is not expected to clear the
southeast half of the forecast area until this evening, thus there
remains a small chance of seeing showers and possibly a
thunderstorm yet. Once this discontinuity sags away from the area,
the influx of drier air will begin with dew points dropping into
the upper 40s north and 50s south by daybreak. Expect some gusty
north winds near Lake MI as the cooler/drier air arrives this
evening, but speeds should hold short of small craft criteria.
Otherwise, look for decreasing clouds with winds away from the
lake becoming light and variable overnight. This may lead to some
patchy ground fog, but not enough to warrant a mention in the
forecast at this point. Min temperatures will range from 45-50
degrees north, upper 50s to around 60 degrees east-central WI.

The area of high pressure is forecast to build into the Great
Lakes on Wednesday, bringing mostly sunny skies, more seasonal
temperatures, lower humidity levels and a north-northwest wind to
the region. Look for max temperatures to reach the lower to middle
70s north/lakeshore, middle to upper 70s south.

.LONG TERM...Wednesday Night Through Tuesday
Issued at 255 PM CDT Tue Aug 30 2016

long-wave ridging will become entrenched over the western Great
Lakes during the middle to late part of the week with a much
cooler and fall like atmosphere settling in across the area. The
high will bring dry weather to the region during this period, with
the one caveat being Thursday when some lake effect clouds off
Lake Michigan affect the lakeshore counties. Although some models
are still generating QPF across these counties during this period,
there are still dry model solutions, therefore will not break up a
dry forecast despite the possibility of a stray shower during this
period.

Later in the forecast the high shifts east, allowing for return
flow as temperatures inch close to and warmer than normal by the
weekend. A low pressure system developing across the northern
plains will bring the next chance for rain later in the weekend
and into early next week. Model solutions are consistently
pushing this chance back, with the chance for rain on Saturday
night looking very slim. In fact the ECMWF solution does not bring
rain into the western CWA until Sunday evening. At this point will
stick with the superblend with the disclaimer that there is a
chance Sunday could be mostly if not completely dry. The chance
for rain picks up precipitously early next week as this system
continues tracking east with the threat for heavy rain given the
strong dynamics and PWAT values approaching 2 inches.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1151 AM CDT Tue Aug 30 2016

Cold front about to exit east-central WI, sending the best chances
for showers and thunderstorms into southern WI. However, drier air
remains a good 150 miles behind the cold front, therefore cannot
rule out additional isolated showers or storms this afternoon.
Once the drier air arrives this evening, the precipitation threat
will end and skies will gradually become mostly clear. VFR
conditions should predominate, but there is a narrow band of MVFR
cigs associated with the leading edge of the drier air for this
afternoon/early this evening. Finally, look for brief gusty winds
at the ATW, GRB and MTW taf sites early this evening when the
winds turn to the north-northeast. Winds could gust over 20 knots
at times before settling down overnight.
&&

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

$$

SHORT TERM.....Kallas
LONG TERM......Kurimski
AVIATION.......Kallas



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