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Area Forecast Discussion
Issued by NWS Green Bay, WI
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FXUS63 KGRB 010458
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1058 PM CST Tue Jan 31 2017

Updated aviation portion for 06Z TAF issuance

.UPDATE...
Issued at 540 PM CST Tue Jan 31 2017

A cluster of intense snow showers will move through central
Wisconsin early this evening. Some of the instability generating
the snow showers resulted from surface heating in an area where
breaks developed in the overcast, so the snow showers will
probably diminish as they head east. However, still expect
localized visibilities well below 1/4SM and a very quick inch or
two of snow in the strongest snow showers. KEAU reported 1/4SM
TSSN a short time ago. The snow showers will mainly affect areas
from ISW-STE-PCZ-ATW-MTW southward. Will re-issue the SPS to
highlight what will likely be a sudden onset to very hazardous
travel conditions.
&&

.SHORT TERM...Tonight and Wednesday
Issued at 223 PM CST Tue Jan 31 2017

The latest rap analysis and satellite/radar imagery show low
pressure sliding east over eastern New York, and an associated
trough curving northwest from this low across northern Lake Michigan
to Lake Superior.  Light to moderate snowfall with this trough and
also a shortwave located over northeast Wisconsin has finally exited
north-central WI, and the back edge is entering the Fox Valley. Snow
showers of a more scattered variety are moving southeast over
northern Minnesota and western Wisconsin, associated with additional
shortwave impulses. Some of the more intense snow showers could
reach Wood and Waushara counties late this afternoon into early
this evening and drop a quick half inch or inch of snow. Forecast
concerns in the short term include snow shower chances followed
by clouds.

Tonight...Cyclonic flow will remain present through the evening,
with weak shortwave energy passing overhead.  These impulses will
likely provide scattered snow showers and flurries through midnight
or early overnight under cloudy conditions. Central and north-
central WI could see up to an additional inch of fluff. Drier air
tries to push in from the west overnight, but with flow off Lake
Superior and a weak surface trough positioned over the Upper
Peninsula, think it will be tough to see clearing take place
across northern WI. Better chances of at least partial clearing
should occur over central and east- central WI late tonight with
the added help of downsloping. Lows mainly falling into the teens
except with a few 20s along the Lake.

Wednesday...That surface trough over the Upper Peninsula will weaken
as it drops south into northern Wisconsin during the morning hours.
Scattered snow showers could accompany this trough over the far
north and will keep a small chance through midday.  Areas where
clouds scattered overnight will likely see clouds build again by
late morning as models depict steep low level lapse rates developing
with heating of the day.  Wouldnt be surprised to see a few
flurries, but moisture depth does not look deep enough at this time.
Some clearing could return from west to east by late afternoon with
another surge of dry air.  Highs ranging from the middle teens in
the far north to the middle 20s in the south.

.LONG TERM...Wednesday Night Through Tuesday
Issued at 223 PM CST Tue Jan 31 2017

Broad area of low pressure over the Hudson Bay and Quebec keeps
Wisconsin in west/northwest flow through the end of the work week.
This sets up a quiet and dry weather pattern with the main focus
on colder temperatures and wind chills. As the low moves east and
weakens this weekend, this allows for a more active setup across
Wisconsin and the focus turns to a couple of weather system to
affect the area.

With high pressure building in Wednesday night drier air will
allow for mostly clear skies and below normal temperatures
through Friday. Winds Wednesday night into Thursday look to back
to the west, keeping the lake effect snow potential north of the
Wisconsin/Michigan border. However, would still expect more clouds
in north-central Wisconsin. With the broad area of low pressure
still situated to the northeast, will see a slight increase in the
pressure gradient as high pressure builds in. While winds don`t
look too impressive, the colder air will be much more noticeable
with this wind. Coldest time looks to be Friday morning with lows
in central and north-central Wisconsin in the -5 to -10 degree
range. This time period will need watching, but right now wind
chill values should stay above criteria, with the coldest
readings between -15 to -20 Friday morning in central and north-
central Wisconsin. Northeast and east- central Wisconsin will not
feel quiet as cold with wind chills of about -10 to -15.

On Saturday, winds shift to the south and we start to see warming
temperatures. Also expect to see increasing clouds ahead of our
next system. Surface low accompanied by mid- level trough and WAA
look to bring a round a snow to the area in the Saturday afternoon
through early Sunday time frame. Models consistently show this
system passing through the area, however run-to-run consistency on
timing and available moisture varies. In the last three runs the
GFS has changed from 0.02" to 0.06" to 0.23" of liquid over Green
Bay for this event. Due to these differences it is still too early
to determine best timing and snowfall amounts.

Following this system the winds will need watching for potential
lake effect snow showers over far north- central Wisconsin through
Sunday. Models have also been showing a weak front pass through
Monday which could bring some very light snow or flurries,
primarily to the north. Moisture still looks limited for this so
kept the mention out of the forecast for now.

Early next week, long range models show a potent system bringing
precipitation to the forecast area beginning Tuesday. Temperatures,
moisture profiles, and corresponding precipitation types could be
a concern with this system. It`s still too early to pin down
details and would expect those to get sorted out in the coming
days.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1057 PM CST Tue Jan 31 2017

Cloud trends for the period are rather unclear. There will
probably be more clouds during the next 12 hours and fewer
thereafter. Generally VFR conditions are expected, though there
will be some MFVR ceilings at times.
&&

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

$$

UPDATE.........Skowronski
SHORT TERM.....MPC
LONG TERM......KLB
AVIATION.......Skowronski
National Weather Service Regional Headquarters
