Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 140418

Area Forecast Discussion
National Weather Service Green Bay WI
1018 PM CST Mon Feb 13 2017

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Tuesday
Issued at 247 PM CST Mon Feb 13 2017

The main forecast concerns are primarily focused on Tuesday as a
cold front/strong mid-level shortwave trough sweeps across WI.
Precipitation type is a problem initially late tonight as we lose
ice aloft behind an initial weak cold front. As the main system
arrives on Tuesday, how warm will temperatures be once the
precipitation begins? Who will see snow versus rain?

The 18z MSAS surface analysis indicated an area of high pressure
extended from the Ozarks into the Ohio Valley. The first cold
front extended from the Upper MS Valley southwest into the central
Plains. Visible satellite imagery showed high clouds had started
to overspread WI ahead of the frontal boundary.

The first (weak) cold front is forecast to move across northeast
WI during the late evening/overnight hours, however the atmosphere
is too dry to support any precipitation, thus have maintained a
dry forecast for most of the forecast area. The exception would
be north-central WI where a slight chance of freezing drizzle is
possible due to a lack of ice aloft behind the cold front and some
weak lift is expected to persist through the night. The rest of
northeast WI will see clouds thicken and this will help to hold
temperatures up overnight. Look for min temperatures to be in the
middle to upper 20s north, upper 20s to lower 30s south (which is
our normal max temperature for mid-February).

A stronger cold front, accompanied by a strong mid-level shortwave
trough, is progged to drop southeast into the Great Lakes mainly
during the afternoon hours of Tuesday. Lift from the cold front,
coupled with strong mid-level Q-G forcing and steep low/mid-level
lapse rates, should bring a chance of snow showers and/or rain
showers to the region. Better likelihood of seeing a minor snow
accumulation would be north-central WI (especially Vilas County
where lake enhancement is expected as winds veer northwest).
Meanwhile, southern sections of the forecast area will not see any
accumulation at all. Blustery conditions will be noted behind the
front behind the cold front with sustained winds of 10 to 20 mph
and gusts of 25 to 35 mph. Max temperatures on Tuesday will reach
the lower 30s north-central, upper 30s east-central WI.

.LONG TERM...Tuesday Night Through Monday
Issued at 247 PM CST Mon Feb 13 2017

Lake effect snow showers over far north central Wisconsin
should diminish Tuesday night as drier air arrives and a low level
temperature inversion sets up. Maybe a half inch to an inch of
additional snow possible in Vilas county.

Dry and colder weather expected for the middle of the week, but
just back to normal temperatures for this time of the season. A
flat upper ridge is forecast to move in Thursday and Friday with
southerly flow at the surface. This will produce well above normal
temperatures Friday and Saturday despite a weak cold front moving
through Saturday.

The upper flow should become southwest Sunday night or Monday,
and southerly low level flow will bring up Gulf moisture Monday
night or Tuesday along with a chance of rain. Warm and moist air
moving north across the cold ground and remaining snow cover may
produce areas of low clouds and fog.

.AVIATION...for 06Z TAF Issuance
Issued at 1018 PM CST Mon Feb 13 2017

A cold front will drop over the state overnight into Tuesday
morning. A low-level jet will lead to low level shear conditions
while surface winds shift from southwest to northwest through
Tuesday morning. Gusty northwest winds to 30 knots are possible
Tuesday in the wake of the front. Cigs tonight should mainly be in
the VFR levels at the onset due to an initially dry air mass.
Some patchy MVFR cigs may occur late tonight across the far north.
Colder air aloft on Tuesday may lead to bkn cigs of a higher end
MVFR or lower end VFR.



SHORT TERM.....Kallas
AVIATION.......TDH is the U.S. government's official web portal to all federal, state and local government web resources and services.