Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 232248

Area Forecast Discussion
National Weather Service Green Bay WI
548 PM CDT Wed Aug 23 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Thursday
Issued at 209 PM CDT Wed Aug 23 2017

The latest RAP analysis and satellite/radar imagery show northwest
flow continues off Lake Superior early this afternoon, with moisture
fluxes leading to a broken cu field over the northern part of the
state.  Still seeing sporadic obs of light drizzle being reported
over Vilas County.  The next shortwave is moving southeast over
southern Manitoba where scattered light rain showers are occurring.
The mid-level cloud deck associated with this system is already
approaching northeast Minnesota.  Precip chances with this system,
and impact on temps are the main forecast concerns.

Tonight...Shortwave trough over southern Manitoba will swing across
the region late tonight.  Mid and high clouds will be on the
increase during the evening hours.  But low levels will struggle to
saturate due to the very dry airmass as evident by the 12z GRB
sounding.  As a result, precip chances look to be confined to mainly
central Wisconsin between 08-12z approximately, and will increase
precip chances some there.  The influx of clouds will likely hold up
temps for a period over north-central WI before they fall again late
as skies begin to clear.  Though patchy frost remains possible in
the cold spots, concerns about cloud cover are high enough not to
issue a frost advisory.  Will instead issue an SPS in case the
clouds diminish before reaching northern WI.  Lows ranging from the
mid 30s in the cold spots to near 50 degrees over the southern Fox

Thursday...As the shortwave departs, clouds will be exiting central
and northeast Wisconsin during the morning hours.  High pressure
will then reassert itself for the rest of the day, with a drier
airmass than the one currently present over the area.  As a result,
should see less cloud cover during the afternoon hours.  Highs
ranging from the mid 60s to near 70.

.LONG TERM...Thursday Night Through Wednesday
Issued at 209 PM CDT Wed Aug 23 2017

Cool high pressure will continue to dominate the region Thursday
night into Friday. Clear skies and light winds provide the
potential of patchy fog Thursday night. Thursday night overnight
lows across northern Wisconsin may also support pockets of frost
over the climatological cool spots.

Progs are trending for a wetter weekend for part of the area.
While a surface high pressure system remains anchored over the
Great Lakes region, return flow over the Northern Plains will
spread over parts of the western Great Lakes region. Progs then
drift an 850 mb low with surface low across the state Saturday
night into Sunday. The more aggressive GFS model run provides up
to a quarter inch of rain over much of the area Saturday night and
Sunday while the ECMWF is a bit slower with the arrival Saturday

The low pressure region then gradually shifts south Sunday into
Monday but still near the area for continued rain chances. High
pressure then attempts to build back into the area as upper
heights increase. Precipitation chances then become more isolated
or end and temperatures return to more normal levels.

.AVIATION...for 00Z TAF Issuance
Issued at 542 PM CDT Wed Aug 23 2017

Scattered to broken vfr cumulus clouds will quickly dissipate with
sunset this evening. However, an upper level disturbance will
bring a chance of light showers to mainly central WI late tonight,
but conditions should remain VFR with this system, with mainly
broken to overcast mid-level clouds. Skies will clear early
Thursday morning across most of the area and remain mostly sunny
and VFR through the afternoon with light winds.



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