Area Forecast Discussion
Issued by NWS Green Bay, WI

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183
FXUS63 KGRB 211655
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1055 AM CST Sat Jan 21 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Sunday
Issued at 245 AM CST Sat Jan 21 2017

Fog along with precipitation trends and type continue to provide
the forecast challenges this weekend.

Fog and drizzle continues to spread into the region with the
moist feed ahead of the upper low system shifting toward the
western Great Lakes region. Radars show a band of light showers
moving northward this morning ahead of aN 850 MB warm front.
Temperatures early this morning ranged from a few degrees above
freezing over central and northeast Wisconsin to near freezing
across north central Wisconsin. Reports from last evening over
north central Wisconsin along with latest state road report early
this morning suggest a continued support for the winter weather
advisory for the north this morning for mainly freezing drizzle.
The scattered light bands of light rain showers will be working
into northern Wisconsin as well this morning to also support the
headline.

Dense fog is observed over most locations except over north
central Wisconsin. The rain showers passing over were producing
enough mixing to improve vsbys briefly. Will consider adding north
central Wisconsin to the advisory if vsbys begin to fall this
morning.

Light precipitation will shift northward tonight into Sunday as
the upper low system lifts to Lake Superior. While precipitation
is expected to be on the decline from south to north, light winds
and moisture boundary will keep the threat of fog around.

.LONG TERM...Sunday Night Through Friday
Issued at 245 AM CST Sat Jan 21 2017

Forecast concerns revolve around precip chances during this period.
Will follow a blend of the gfs/gem for Sunday night through Monday
night as they compare relatively well.  Then for the fast moving
cyclone projected to arrive midweek, have a preference for the ecmwf.

Sunday night through Monday night...Low level troughiness will
continue to hang back across the region, which should lead to the
continuation of the low cloudiness, fog, and possibly drizzle for
Sunday evening. Some drizzle could be freezing over far north-
central WI.  Mid-level moisture will push west as it rotates around
a large upper low positioned over the southeast conus, and into
eastern WI late Sunday night into Monday. Saturation depth improves
during this time sufficiently enough for showers over eastern WI,
which could extend into Monday night as well.  No real push of dry
air for central and north-central WI, so think will mostly cloudy
skies continue.  Little changes to temps, should remain in the 30s
for Sunday night and Monday, and could fall into the upper 20s over
northern WI on Monday night.

Rest of the forecast...Partial clearing could occur on Tuesday
morning as weak ridge of high pressure moves across the region.  But
clouds will be rapidly on the increase on Tuesday afternoon ahead of
the next cyclone.  Still plenty of uncertainty remains with the
track/timing of this cyclone although models have been converging
over the past 24 hours of runs.  As precip overspreads the region
from southwest to northeast as early as Tuesday afternoon, but
probably more towards Tuesday night, temps could be warm enough for
a mix over parts of east-central Wisconsin, but precip should be
mainly snow to the north and west.  Early indications are that this
has potential to be a 3-6 inch snowfall depending upon the eventual
track and temperature profile. Behind the system for later Wednesday
through Friday, northwest winds will bring in more seasonable
temperatures.  Cyclonic flow will bring occasional snow showers
during this time as well.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1044 AM CST Sat Jan 21 2017

Dense fog will linger across much of the region through Sunday
morning. For locations from KRRL to KRHI to KLNL/KD25, visibilities
were in the 1 to 2 mile range due to rain. The dense fog should
arrive in this area this afternoon once the steadier showers exit
the region. The dense fog in this region should continue through
mid day on Sunday. The dense fog may also deposit a thin coating
of ice across far northern Wisconsin on untreated surfaces as
pavement temperatures are forecast to fall to around freezing
late tonight into early Sunday morning. It should be noted that
the dense fog could linger into the afternoon on Sunday as mild
air remains over the region.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until noon CST Sunday for WIZ011>013-019>022-
030-031-035>040-045-048>050-073-074.

Winter Weather Advisory until noon CST today for WIZ005-010>013-
018-019.
&&

$$

SHORT TERM.....TDH
LONG TERM......MPC
AVIATION.......Eckberg



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