Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 252334
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
634 PM CDT SUN SEP 25 2016

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Monday
Issued at 258 PM CDT Sun Sep 25 2016

Precipitation trends remain the main forecast focus over the next
24 hours, although increasing winds will create issues over the
bay and Lake MI on Monday.

The 19z MSAS surface analysis showed a cold front stretched from
northeast MN south-southeast into western WI, then south into
western IL. Some breaks in the clouds over eastern WI had allowed
temperatures to warm near 80 degrees and with dew points in the
upper 60s, thunderstorms had started to blossom over southern WI
which are headed northeast in our direction.

Showers/scattered thunderstorms will continue to track across the
rest of eastern WI this evening as the cold front sweeps eastward
through the region. Some semblance of a dry slot should bring a
brief respite to the precipitation for a time over central and
east-central WI overnight, however as a strong shortwave trough
pushes into the Western Great Lakes after midnight, increasing
cyclonic flow, mid-level shortwave energy and CAA will allow for
at least a chance of light rain showers across northern WI. A
tightening pressure gradient, steepening lapse rates and strong
subsidence behind the cold front will bring gusty west winds to
the area later tonight which will carry over into Monday. Min
temperatures will be in the mid to upper 40s north-central, upper
40s to lower 50s elsewhere except lower to middle 50s along Lake
MI.

The shortwave trough is progged to become a closed upper low over
southwest Ontario/Western Lake Superior on Monday. Cyclonic flow
to remain in place with individual shortwave energy rotating
through this mid-level trough. CAA, in concert with the cyclonic
flow and daytime heating, will bring an unsettled weather day
across the forecast area, especially the farther north you go.
Breezy conditions will also continue through the day with
sustained west winds of 15 to 25 mph and gusts that could approach
35 mph. It will also feel like autumn on Monday as max
temperatures are only expected to reach the lower to middle 50s
north, around 60 degrees elsewhere.

.LONG TERM...Monday Night Through Sunday
Issued at 258 PM CDT Sun Sep 25 2016

The upper low will move slowly south from Lake
Superior to the Ohio Valley by the middle part of the week. The
cyclonic flow and cold temperatures aloft will result in cloudy
skies and scattered showers, especially in the afternoon and in
the north. Temperatures are cold enough aloft for lake enhancement
to the showers in far northern Wisconsin and near Lake Michigan if
winds become northeast Tuesday or Wednesday.

The upper system moves far enough away for dry weather to follow
for the rest of the week if the GFS is correct. The ECMWF brings
the weakening upper system back towards the western Great Lakes by
the end of the week, which might bring showers to our area if
correct. Will leave it dry for now.

Cooler than normal temperatures are expected Monday and Tuesday
afternoons, but otherwise seasonable temperatures are expected.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 621 PM CDT Sun Sep 25 2016

The main band of showers and scattered thunderstorms was exiting
far eastern WI early this evening, but scattered showers continued
to develop ahead of the cold frontal boundary. These showers should
shift east of the region late this evening. However, wrap-around
showers will work their way into north central and far northeast
WI late tonight into early Monday, and affect the northwoods
region through the day. Farther south, the showers are expected to
be more isolated.

VFR and patchy MVFR conditions are expected early in the TAF
period, but more widespread MVFR conditions should spread back
into the RHI/AUW/CWA TAF sites by midnight. A period of IFR
conditions is likely in north central WI late tonight into
Monday morning.

Winds will become westerly in the wake of the frontal passage
this evening, and will become quite gusty by mid to late
morning on Monday. Gusts to 25 to 30 kts are likely.
&&

.MARINE...
Issued at 258 PM CDT Sun Sep 25 2016

Behind the cold front, gusty west winds are expected Monday into
Tuesday. Gale force gusts are possible at times Monday afternoon
into Tuesday afternoon across the coastal waters of northern Door
County. Winds should begin to decrease later Tuesday afternoon and
Tuesday night.
&&

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

$$

SHORT TERM.....Kallas
LONG TERM......RDM
AVIATION.......Kieckbusch
MARINE.........Kallas



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