Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 201103

Area Forecast Discussion
National Weather Service Green Bay WI
503 AM CST Mon Nov 20 2017

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 239 AM CST Mon Nov 20 2017

Southerly winds ahead of an approaching low pressure system will
bring above normal temperatures to the area today. With very dry
air in place, the weather is expected to be dry with mostly sunny
skies for much of the morning. Increasing clouds will come in
from the west this afternoon as the low pressure system gets
closer to the area. Highs today will generally be in the 40s
across northeast Wisconsin.

A clipper system will track through southern Canada tonight,
bringing a cold front through the western Great Lakes. Despite the
passage of a cold front, the main effect will be clouds and a wind
shift as model soundings indicate a lack of deep moisture with the
best dynamics well to the north coincident with the low itself.
Lows tonight are expected to range from the lower 20s across the
north, with lower to middle 30s across east-central Wisconsin and
the lakeshore.

Although high pressure will build in across the northern Plains on
Tuesday, winds will be conducive for some lake effect snow across
the far north as delta T values climb to the middle teens. The
best chance for accumulating snow will be in Vilas County, where a
few tenths or an inch of snow is possible. The rest of the area
will be fairly dry with skies clearing out in the afternoon hours
as the high inches eastward. Highs Tuesday will range from the
middle to upper 20s across the north, with highs in the middle 30s
across east-central Wisconsin and the lakeshore areas.

.LONG TERM...Tuesday Night Through Sunday
Issued at 239 AM CST Mon Nov 20 2017

The main concern for this package will be the chances of snow
showers across the far north Tuesday night, rain chances and high
temperature on Friday, and lake effect snow showers across the far
north next weekend.

For Tuesday evening, scattered lake effect snow showers or flurries
will be ongoing across far north-central Wisconsin, especially
across Vilas county. Low level winds are bit west of north, thus
snowfall amounts will be limited across the northern portion of
Vilas county. The snow showers will come to an end late Tuesday
night as low level winds back more westerly and drier air filters
into the region. For Wednesday, travelers should see mostly sunny
skies with highs in the upper 20s to middle 30s.

For Thanksgiving Day, it will start out seasonably cold with
morning temperatures in the teens to lower 20s. High temperatures
during the afternoon should warm into the middle 30s to lower 40s
which is very close to normal. The forecast on Friday is somewhat
uncertain with the next cold front approaching the area from the
west. The latest ECMWF/Canadian model surface temperatures indicated
readings in the lower to middle 50s. Current forecast has highs
in the 40s, thus high temperatures may need to be raised several
degrees if the model trends continue. As for precipitation type,
will go with a chance of showers on Friday. Of note, mid level
lapse rates were around 6 C/KM, thus wouldn`t be surprised if
there was a clap of thunder Friday afternoon especially across
northern Wisconsin. Blustery to windy conditions are expected
ahead and behind the cold front which is expected to move across
the area Friday night. A colder northwest flow noted behind the
front. The chances for lake effect snow showers across the far
north will be on the increase later Friday night and continue into
Saturday night or Sunday morning. After a mild Friday, temperatures
return to or below normal by next Sunday.

.AVIATION...for 12Z TAF Issuance
Issued at 503 AM CST Mon Nov 20 2017

Mid and high level VFR clouds are anticipated through the TAF
period. Gusty south winds are expected this afternoon and this
evening, before turning westerly later tonight as a cold front
passes through. The main aviation concern is LLWS, which will
develop in advance of a cold front this evening, as southwest
winds aloft increase to 40 to 50 kts.

Issued at 239 AM CST Mon Nov 20 2017

Pressure gradient is forecast to tighten between high pressure
over the Mid-Atlantic states and the clipper low pressure moving
across southern Canada today and tonight. A small craft advisory
is in effect starting this afternoon. A few Gale force gusts are
possible tonight and Tuesday as winds become northwest, however
they are not expected to last long enough to issue a Gale Warning
with this issuance. Winds are expected to drop below small craft
criteria by Wednesday as ridging moves through the western Great



SHORT TERM.....Kurimski
LONG TERM......Eckberg
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