Area Forecast Discussion
Issued by NWS Green Bay, WI

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843
FXUS63 KGRB 150441
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1041 PM CST Sat Jan 14 2017

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Sunday
Issued at 248 PM CST Sat Jan 14 2017

Tranquil weather to continue for one more day as high pressure to
be our main weather feature. Thus, near-term issues to focus
solely on temperatures.

The 20z MSAS surface analysis showed a large area of high pressure
that extended from the northern Plains eastward through the Great
Lakes to the New England states. Last of the low clouds have
finally dissipated over east-central WI, leaving clear skies
across the rest of the forecast area.

Quiet and very cold conditions to exist across northeast WI as the
high pressure to dominate the Great Lakes region. Mainly clear
skies with very light winds should provide nearly ideal
radiational cooling conditions to prevail and this will allow
temperatures to tank, especially over our typically colder
locations over north-central WI. Look for min temperatures to
generally be in the -5 to -10 degree range north, zero to 5 below
range south, except around 5 above along Lake MI.

The surface high begins to slide toward the eastern Great Lakes on
Sunday, but remain the dominant weather feature for northeast WI.
Winds will gradually back from the west, to a south-southwest
direction in the afternoon. This would allow for weak WAA to
develop across WI with 8H temperatures rising into the -2C to 0C
range by 00z Monday. Other than some high clouds drifting across
the southern half of the state ahead of our next weather system,
Sunday should see plenty of sunshine with max temperatures mainly
in the lower to middle 20s. A few upper 20s are possible west of
the Fox Valley.

.LONG TERM...Sunday Night Through Saturday
Issued at 248 PM CST Sat Jan 14 2017

Primary focus continues to be on the low pressure system
approaching the western Great Lakes early in the work week. NWP
models, save for the outlier NAM, continue to trend slower with
the system approaching the area. The 12z model runs have very
little QPF with the low until Monday afternoon, with some
solutions holding off most of the QPF until Monday night,
especially across the north. Given these recent developments and
overall model trends, will push back POPs from the previous
forecast and SuperBlend with this forecast issuance.

The system itself will have many challenges with respect to
precipitation type as a warm layer aloft and some dry air aloft
starts out the precipitation mainly as snow, then mixes in sleet,
freezing rain and rain. Areas across the north have the best
chance for all snow, with areas across the south with the best
chance for liquid precipitation. Despite air temperatures warming
above freezing at times on Monday, pavement temperatures are not
expected to rise above freezing to mitigate the freezing rain
threat until later on Tuesday with several hours of above freezing
temperatures.

This complicated system is expected to produce around a tenth of
an inch or less of ice across the Fox Valley and lakeshore region,
with a tenth to a quarter of an inch just to the north and west of
the Fox Valley with a prolonged period of freezing rain expected
given the cooler surface temperatures. A Winter Weather Advisory
is anticipated in future issuances given the wintry mix expected,
with a Winter Storm Warning possible if ice accumulations approach
a quarter of an inch to the north and west. Given how far out the
system is and continued uncertainty regarding the exact track will
hold off on headlines with this issuance.

The main weather concern beyond this system will be temperatures
warming to around 40 Friday and next Saturday with the chance for
rain as another low pressure system affects the western Great
Lakes region.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1040 PM CST Sat Jan 14 2017

VFR weather expected through at least Monday morning. A winter weather
system will bring low clouds, snow, sleet, freezing rain and rain to
the area Monday afternoon or Monday night through part of Tuesday.

&&

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

$$

SHORT TERM.....Kallas
LONG TERM......Kurimski
AVIATION.......RDM



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