Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 232049
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
249 PM CST Mon Jan 23 2017

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Tuesday
Issued at 248 PM CST Mon Jan 23 2017

Low clouds and fog continue to be the main concerns for tonight
into Tuesday morning, then chances for rain or snow late
tomorrow afternoon across central Wisconsin.

Latest webcams from northern Door County indicated visibilities
down to a few hundred feet at Death`s Door. Latest observations
from Sturgeon Bay and Sister Bay were at a quarter of a mile.
Also, some patchy dense fog was also noted at Marshfield which
should diminish here in the next hour.

For tonight, areas of fog will redevelop outside of Door County
with abundant low level moisture due to melting snow and high
dewpoints. The fog may be locally dense with visibilities down
to around a quarter of a mile in a few spots. For Door County,
weak trough to the east may be enough to stir up the dense fog
later this evening. Confidence is low if this will clear the
dense fog, thus evening shift may need to extend the dense fog
advisory for Door County. Also, included a chance of drizzle this
evening as 500mb trough moves across the region. A few observations
across Minnesota were reporting unknown precipitation, which is
probably drizzle.

For Tuesday, any lingering fog should burn off by mid morning. The
big change is to slow down the chances of precipitation during the
afternoon. Only have slight chances across our southwest counties.
If model trends hold true, midnight shift may be able to go dry
for the entire afternoon. Highs tomorrow should be in the middle
30s to around 40.

.LONG TERM...Tuesday Night Through Monday
Issued at 248 PM CST Mon Jan 23 2017

Main forecast focus continues to be on the system to affect the
area Tuesday night into Wednesday. While there are still some
slight timing/track differences in the models, the latest runs
are converging on a solution closer to the ECMWF. Latest runs
also show a slowing trend which would hold most of the
precipitation back for our area until Tuesday evening.

Beginning 00Z Wednesday most of the forecast area should still be
dry. Precipitation will then start to move in from southwest to
northeast during the 00z to 06z time frame. A rain/snow mix during
the onset still looks reasonable, especially from the Fox Valley
and south, as boundary layer temperatures will be in the middle
30s. As temperatures cool would expect to see all snow by late
Tuesday evening. Models along with WPC guidance continue to show
the axis of heaviest precipitation to our southwest where there is
stronger forcing. Then as the system moves east it begins to
weakens some. Because of this would expect higher snowfall totals
in our central Wisconsin counties, where 4 to 6 inches seems
reasonable, with a broad 2 to 4 inches further north and east. Any
slight change in the system track would change these values, but
with a fairly good run to run consistency with the ECMWF have more
confidence today in snowfall amounts. With relatively warm
temperature expecting a wet, heavier snow that would likely impact
travel Wednesday morning.

For the rest of Wednesday, the slower timing of the system also
means a chance for light snow showers and/or flurries through the
day. Dropped temperatures a bit Wednesday as guidance seemed too
warm. This also cut back on rain/drizzle chances, but a light mix
is possible in the east as the system pulls away.

Focus Thursday through the weekend will be on the potential for
lake effect snow in the north as northwest flow takes over. This
will depend on the exact wind trajectory, which may become
slightly too west at times, but still too early to determine those
details. Otherwise, long term forecast looks generally cloudy
with a couple shortwaves possibly passing by, but nothing to
really pin down at this point. Temperatures settle closer to
average by Friday and stay there through at least early next week.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1132 AM CST Mon Jan 23 2017

IFR/MVFR CIGS and patchy lower visibilities due to fog will
continue this afternoon into Tuesday morning, and possibly Tuesday
afternoon in a few spots. The fog should become more widespread
tonight and early Tuesday morning. The fog may also be locally
dense at times this afternoon across Door County and across the
entire region and Tuesday morning. An accumulating snow is
expected across much of the area Tuesday night into Wednesday
morning.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 PM CST this evening for WIZ022.
&&

$$

SHORT TERM.....Eckberg
LONG TERM......KLB
AVIATION.......Eckberg


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