Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 111200
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
600 AM CST Thu Jan 11 2018

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Friday
Issued at 419 AM CST Thu Jan 11 2018

Very warm air has worked its way into our southeast counties in
advance of an arctic cold front, with readings in the 45 to 50
range from Wautoma to the Fox River Valley. Farther north, where
the snow pack was deeper, temperatures were only in the middle to
upper 30s. Road temperatures and spotter reports indicate that
road surfaces remain below freezing over much of north central and
parts of far northeast WI. light freezing rain/drizzle and frost
deposition has resulted in very icy conditions, especially
northwest of a line from Wausau to Florence. Areas of dense fog
were also reported from Wausau and Marshfield eastward to Shawano
and Clintonville, though visibilities in eastern WI have improved
greatly over the past several hours. Precipitation has been
spotty and light so far, but the radar mosaic indicated an
intensifying frontogenetic band extending from IA through
southeast MN to north central WI. This band should result in a
quick increase in precipitation over our far northwest counties
during the next hour or two, with freezing rain gradually
changing to snow. MSAS surface analysis showed the arctic cold
front just edging into far northwest WI.

Models continue to show the best forcing persisting over our
northwest counties during the day, with total snow accumulations
of 3 to 6 inches anticipated. There has been a trend toward
increasing QPF amounts a bit farther east than previous forecasts.
The combination of icy roads and freezing rain potential this
morning, plus slightly higher snowfall amounts of 1 to 3 inches
from Wausau to Florence, has resulted in a need to expand the
Winter Weather Advisory another tier of counties to the east.
Although snow and ice accumulations should be fairly minimal
farther east, the arrival of much colder air later this afternoon
and evening could cause a flash freeze on the roads, leading to
hazardous travel for the evening commute. Will continue to handle
this threat with the Hazardous Weather Outlook, Special Weather
Statements, Weather Stories and social media. Used a blend of
various models for temperatures today, with readings expected to
fall into the teens across parts of north central and central WI
by evening.

Light snow will persist into this evening before diminishing,
though snow showers will linger in the Lake Superior snow belt
overnight, along with additional minor accumulations. Otherwise,
the main story will be colder weather, with highs only in the
single digits and teens on Friday.

.LONG TERM...Friday Night Through Wednesday
Issued at 419 AM CST Thu Jan 11 2018

Main story for this period will be the bitter cold this weekend,
then the chances of snow late Sunday afternoon into Monday night,
and then continued cold for the first half of next week. There are
some indications that temperatures will moderate by the end of
next week.

For Friday night and Saturday, high pressure will move into the
region. A northwest flow off the relatively warmer waters of Lake
Superior could still bring a few light snow showers or flurries to
northern Vilas county. Low level winds are relatively light and
are a bit more westerly, thus any accumulation would be light for
each period. On Saturday night, high pressure will be centered
across the region. The combination of clear skies and light winds
will allow for temperatures to tank in the typical cold spots
north and west of the Fox Valley. Did lower minimum temperatures
several degrees. Clouds will be on the increase Sunday with light
snow arriving across the west by late afternoon. The latest ECMWF
model is a little quicker, thus it is possible snow chances will
need to be increased with later forecasts. The numerical guidance
has come in a little more robust with snow totals compared to last
night. Could see at least several inches of snow. Something to
watch over the next several days is the models are indicating low
level winds turning to the east/northeast off Lake Michigan Monday
afternoon into Monday night, which really could enhance snow totals
across the Fox Valley and especially the lakeshore region. Will
have to wait and see if the models continue this signal in the
winds.

Cold weather to continue through the first half of next week.
It now appears that a significant moderating trend is expected
late next week into the weekend of Jan 20-21.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 538 AM CST Thu Jan 11 2018

Aviation trends may not be as clear cut as earlier thought, as
fog and low stratus has at least temporarily departed parts of
central and eastern WI, due to the arrival of a warm front.
Farther northwest and over the deeper snow pack, LIFR/VLIFR
flight conditions in fog and low clouds persisted. After mainly
drizzle or freezing drizzle during the overnight period, a more
significant band of mixed precipitation had recently moved into
north central WI. This mixed precipitation should change over to
snow at RHI/AUW/CWA during the mid to late morning, with
accumulations occurring on runways through early evening.

Expect flight conditions to gradually deteriorate again over our
southern and eastern counties as precipitation fills in and the
cold front approaches. Rain will change to snow at the GRB/ATW/MTW
TAF sites during the mid to late afternoon. Light snow should
taper off later in the evening, with conditions returning to VFR
at most locations. The exception may be in the Lake Superior
snowbelt, where MVFR/IFR flight conditions are possible in snow
showers.

Have continued LLWS through late afternoon or evening, especially
for the eastern TAF sites. Gusty northwest winds will develop in
the wake of the arctic cold front this afternoon and tonight.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM CST this evening for
WIZ010>012-018-019-030.

Winter Weather Advisory until 9 PM CST this evening for WIZ005.
&&

$$

SHORT TERM.....Kieckbusch
LONG TERM......Eckberg
AVIATION.......Kieckbusch



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