Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 292348

Area Forecast Discussion
National Weather Service Green Bay WI
648 PM CDT THU SEP 29 2016

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Friday
Issued at 311 PM CDT Thu Sep 29 2016

A 500mb low that moved from Indiana to Kentucky today was forecast

to move very slowly to the north tonight before reaching southern
Indiana again on Friday. As the low moves to the north, clouds
will spread across the forecast area late tonight with chances for
showers returning to central and eastern Wisconsin during the day
on Friday. Lighter winds across northern Wisconsin with scarce
cloud-cover will result in patchy fog development there late
tonight. Expect cooler temperatures in locations that cloud-over
early, but highs should be similar to today in the north where
clouds will take longer to reach. Northeast winds should increase
as the surface gradient tightens.

.LONG TERM...Friday Night Through Thursday
Issued at 311 PM CDT Thu Sep 29 2016

Some minor changes to this period, more so with the next week

The return of the upper low for the weekend will bring clouds and
precipitation chances for at least the first half of the weekend.
Noted PWATS increases through Friday evening over parts of east
central Wisconsin for a possible timing of a more steady light
rain. Will confine higher pops east of the Fox River as the drier
air west of the Fox river may limit rain chances. Will leave
chance pops elsewhere after Friday evening before tapering off
late Saturday into Saturday night as the upper low weakens and
shifts to the east. Will also leave TSRA out of the fcst as the
cold upper low core of temps remain over Lower Michigan and total
totals values of 50 or more remain east.

A quieter stretch of weather for the first half of the new work
week as an upper ridge drifts over the area and a western states
trough slowly approaches. Some model differences show up by middle
of the week with the evolution and timing of the western states
trough. ECMWF and GFS have shifted to more of a closed upper low
system over the northern plains with a frontal boundary sliding
over the Great Lakes region mid to late week. The ECMWF was a bit
faster with this frontal boundary, tracking over Wednesday
afternoon and Wednesday night, compared to a roughly a day slower
GFS. Nevertheless, with the tropical system or likely hurricane
moving along the east coast next week, the western system may trend
slower in the coming days. Instability not high for next week but
the ECMWF does track a LFQ region of an upper jet over the area
during frontal passage. So a TSRA possible during frontal passage.

.AVIATION...for 00Z TAF Issuance
Issued at 636 PM CDT Thu Sep 29 2016

Low pressure in the Ohio Valley will drift back to the northwest
during the TAF period, and bring showers back into the region on
Friday. The rain should reach MTW shortly after daybreak, GRB/ATW
toward midday, and AUW/CWA in the late afternoon. As the rain and
deeper moisture arrive, ceilings will drop to MVFR, and could
deteriorate to IFR in steadier rain at MTW in the afternoon.

An additional area of low clouds and patchy fog may form over
parts of north central WI late tonight into early Friday, due to
easterly upslope flow.




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