Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 171706

Area Forecast Discussion
National Weather Service Green Bay WI
1106 AM CST Sun Dec 17 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Monday
Issued at 404 AM CST Sun Dec 17 2017

Quiet weather expected through Monday with nearly zonal flow
aloft and just a couple weak upper jets moving by. The low level
moisture in place does not seem deep enough to produce freezing
drizzle or snow flurries, so dropped it from the forecast near the
lake and bay today. Not a hundred percent sure it won`t happen
but at this time it does not look likely. A weak shortwave trough
will move across northern Wisconsin this afternoon and could
produce enough seeding of the low clouds to produce some light
snow showers so added them there this afternoon. Highs today would
be a few degrees above normal with light winds.

Skies might clear for awhile tonight, making low temperature
forecasts tricky. Betting that it will remain mostly cloudy and
kept lows near normal.

South winds and warm advection will make for a milder day Monday.
Highs could hit 40F where there is less snow cover over parts of
Wood, Portage, and Waushara counties. The regional Canadian model
depicts this nicely.

.LONG TERM...Monday Night Through Saturday
Issued at 404 AM CST Sun Dec 17 2017

A possible winter storm for the latter portion of the upcoming
week continues to be the primary forecast concern.

Monday will feature mostly dry conditions and mild temperatures
as zonal flow aloft keeps active weather out of the region. A cold
front will pass into Tuesday with a decent chance of mixing down
some stronger winds from the 925-850 mb levels. Increased winds a
little across the region to account for this, but the primary
impact will be a brief chance for gale force gusts.

The potential winter storm then becomes the focus of the forecast
starting Wednesday afternoon into Friday. This event has the
potential to be long lived. Warm air advection through the mid
levels along the warm front will serve to set up the initial snow
bands and keep moisture in the region, aided by the right
entrance region of an upper level jet. The region then remains
under the influence of the jet as the upper level trough moves
towards the region accompanied by the surface low pressure system.
Tentatively favor Thursday night as the time of the heaviest
precipitation and snow accumulations as the low pressure system
passes southeast of the region. Snow totals will be determined by
frontogenetical forcing and the longevity of the snow bands in
any particular area, which are difficult to determine at this
time, especially with the lack of a clear shortwave. A further
complication could be possible Thursday afternoon as strong warm
air advection in the mid levels could bring mixed precipitation
towards the area. Current models keep the region below freezing,
so kept this out of the forecast for the time being, but this will
be something to watch.

Temperatures will start above normal and remain around normal
through the latter part of the work week before dropping well
below normal by next weekend.

.AVIATION...for 18Z TAF Issuance
Issued at 1100 AM CST Sun Dec 17 2017

Moist air near the ground will keep IFR/LIFR ceilings and
MVFR/IFR vsbys in fog across most of the area through most of
the forecast period. IN addition, there may be a few hours of
light snow across northern WI during the late afternoon and
early evening. Ceilings and visibilities should slowly climb
later Monday morning, as southwest winds increase and mix out
some of the low level moisture.



LONG TERM......Uhlmann
AVIATION.......Kieckbusch is the U.S. government's official web portal to all federal, state and local government web resources and services.