Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 122315

Area Forecast Discussion
National Weather Service Green Bay WI
515 PM CST Sun Nov 12 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Monday
Issued at 300 PM CST Sun Nov 12 2017

A mid level trough is forecast to be east of Wisconsin by 00Z
Monday and continue to move away from the state tonight and
Tuesday as a weaker short wave passes to the north. At the same
time, a surface ridge will pass across Wisconsin.

A wedge of clearing developed from western into east central
Wisconsin, and clouds farther north and south were slowly pushing
east. Not sure if the rest of the area will clear during the night
since Bufkit time/height plots indicated plenty of low level
moisture through Monday morning. Also, fog developed under the
surface ridge last night so patchy fog seems like a good bet
tonight. Used temperatures close to the 12Z MAV for highs on
Monday, so most locations should at least reach the mid 30s.

.LONG TERM...Monday Night Through Sunday
Issued at 300 PM CST Sun Nov 12 2017

The main forecast concern is the potential for a winter storm
with accumulating snow and strong winds Friday into Saturday.

A weak short-wave and jet streak will pass through the region
Monday night, but a lack of significant lift or deep saturation
should prevent precipitation development. Mostly cloudy skies
are anticipated, with developing return flow resulting in an
increase in low clouds across north central and central WI late.

WAA and a surge of moisture below 800 mb will bring a chance of
very light rain or drizzle on Tuesday. Rain chances will increase
Tuesday night as a 30-35 knot low-level jet develops ahead of a
cold front, and a short-wave trof approaches the region. The rain
should end from west to east Wednesday morning as the cold front
exits the forecast area. Scattered lake effect snow showers may
affect north central WI in the afternoon and evening as cold
northwest winds develop in the wake of the front.

High pressure will bring another brief period of dry weather
Wednesday night into Thursday.

Forecast confidence has increased a bit concerning the potential
for a rapidly deepening low pressure system moving through the
western Great Lakes late in the week. WAA and a 40 knot LLJ ahead
of the system should bring light rain or snow to the region
Thursday night, with some minor accumulations possible north. The
low is expected to deepen rapidly as it approaches and moves
through the southeast half of WI on Friday and Friday night, in
response to the arrival of a sharp, negatively-tilted short-wave
trof. This track could bring a significant snowfall to our
northwest counties, with rain changing to snow farther southeast.
Another potential impact is very strong northwest winds late
Friday night into Saturday, with possible Gale or Storm force
gusts on Lake Michigan. The GFS is still faster than the ECMWF,
but both models show an intense and rapidly deepening system.
Roughly half of the GFS ensemble members depict lows with similar
tracks/trends and strength as the operational run, so that`s
pretty decent confidence for a potentially high impact day 5/6

.AVIATION...for 00Z TAF Issuance
Issued at 515 PM CST Sun Nov 12 2017

Late this afternoon conditions ranged from p6sm skc southeast of
a line from MRL to GRB to MTW, and then MVFR cigs northeast of
this area. Anticipate this area of clouds will change little with
the weak flow. However as with the previous long night, fog and
IFR stratus may develop under the region of clear skies this
evening and may linger into Monday morning.



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