Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 181216 AAA

Area Forecast Discussion...UPDATED
National Weather Service Green Bay WI
616 AM CST Wed Jan 18 2017

New Information added to update section

Issued at 616 AM CST Wed Jan 18 2017

Uptick in southwest winds early this morning has been enough to
improve vsbys to less coverage of dense fog. Will cancel the
advisory an hour earlier.

.SHORT TERM...Today...Tonight...and Thursday
Issued at 226 AM CST Wed Jan 18 2017

Forecast issue next 24 hours centers on cloud trends and fog
formation. Areas of dense fog has developed early this morning due
to a moisture boundary, light winds and clearing skies tuesday
evening. Dense fog continues to trend to more widespread so
will issue a dense fog advisory for most locations, except the
far north. Morning inversion as per forecast soundings will also
tend to keep clouds around at least the morning hours. H850 temps
approaching +8 C this afternoon will increase the inversion and
may tend to keep clouds around. However mixing on the increase as
well with 25 kt winds at the 850 level. Higher terrain locations
over northern Wisconsin may clear out quicker today.

All progs depart stratus clouds for the afternoon hours with
increased mixing. Anticipated clear skies may lead to more fog
formation tonight but likely not as widespread due to increased
southwest winds.

For Thursday, clouds will be on the increase from the south with
the approach of a short wave trough later in the day. Hopefully we
can get a dry sunny period before the clouds later Thursday to
help erode some of the ice accumulation from the last few days.
Previous data were not in agreement with lifting this energy
northward into the area.

.LONG TERM...Thursday Night Through Tuesday
Issued at 226 AM CST Wed Jan 18 2017

Split flow continues to look like the predominate pattern across
North America through the middle of next week.  The medium range
models are struggling with this pattern, due to the blocky nature of
the flow and various upper lows migrating east across the center of
the country.  Will continue to put more stock into the ecmwf.

Thursday night thru Friday night...The models are more ambitious
pushing a shortwave into a rather stout mid-level ridge positioned
over the western Great Lakes late Thursday night into Friday.  Some
of this precip could reach central and east-central WI late in the
evening into the overnight, but north-central and far northeast WI
may have to wait until Friday morning for the arrival of precip.
Some potential for freezing rain in central and east-central WI late
Thursday night with warm layer temps in the +3-4 range and surface
temps around 32/33 degrees. Temps are projected to be colder over
far northeast and north-central WI, so if precip arrives before
diurnal heating sufficiently warms surface temps, they could also
see a window for freezing rain on Friday morning.
The wave will be weakening as it lifts north of the area for Friday
evening, but soundings look rather saturated above 800mb, which
could mean that drizzle/freezing drizzle will persist into Friday
night over northern WI.  Though there will be less of a chance of
drizzle over central and east-central WI, temps will likely remain
above freezing, so a freezing drizzle threat looks relatively low.

Rest of the forecast...Despite mild temperatures continuing through
the weekend, low level moisture looks to become trapped beneath a
subsidence inversion.  With shortwaves passing by in close proximity
to our west, think we could see occasional drizzle or light shower
chance continue through the weekend, high probabilities over central
and north-central WI. A more significant upper low could bring
widespread light precip late Sunday into Monday.  Even yet another
potent low could traverse the region during the middle of next week.

.AVIATION...for 12Z TAF Issuance
Issued at 541 AM CST Wed Jan 18 2017

Widespread IFR cigs and vsbys with areas of LIFR vsbys
and cigs due to dense fog will linger this morning. Vsbys may
improve during the morning however cigs will be slower to improve
this morning due to an inversion to overcome. Improvement to
continue to mainly VFR conditions this afternoon and tonight.
Anticipated clear skies this evening with light southwest winds
may provide conditions to develop IFR cigs and vsbys again tonight
due to fog and stratus.



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