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Area forecast discussion 
National Weather Service Green Bay WI
1036 PM CST Friday Dec 19 2014

Updated aviation portion for 06z taf issuance
updated short term

Short term...tonight and Saturday
issued at 1035 PM CST Friday Dec 19 2014

Southerly low level flow will return tonight as an
upper trough approaches from the west and surface high over the
western Great Lakes edges east. Clouds should be on the increase
overnight from the south and west so northeast Wisconsin will
likely have the coldest temperatures overnight. Some patchy fog
possible later tonight before clouds arrive.

Lowered mins a bit across the far northeast where clear skies hung
on the longest this evening. Temperatures will become steady or slowly rise
toward daybreak as clouds increase.

Long term...Saturday night through Friday
issued at 250 PM CST Friday Dec 19 2014

Potentially active pattern for next week with a developing upper
low system over the Great Lakes region.

Light mix potential will be on the increase early Sunday as a middle
level trough approaches from the west. Weak warm air advection and return south
flow will allow moisture to gradually return to the area Sunday
into Sunday night.

Challenge with the forecast increases starting Monday when the
upper system slowly drifts eastward and deepens over the western
Great Lakes. Location of the upper system will serve to impact
temperatures and precipitation type...with the more western trend supporting a
rain and snow mix through Tuesday. 500 mb model center low
position for this deepening low late Tuesday range from Iowa for
the GFS and European model (ecmwf) to central Minnesota for the Gem. While the GFS and
European model (ecmwf) produce 0.25 to 0.35 quantitative precipitation forecast for Tuesday night...the Gem dry
slots the area. The GFS also brings in a higher amount of mainly
rain for Wednesday ranging mainly from 0.25 to 0.50 over far
eastern Wisconsin...while the rest of the models develop more of a
dry slot.

The evolution of the upper system continues to cause issues with
precipitation type Tuesday night and especially Wednesday with colder air
approaching from the northwest. This rate of change over to all
snow will affect snow accumulations.

Eventually the forecasts shift this deep upper low just east of the
area Wednesday night for a complete transition to snow from west
to east...but by then the surface low is lifting over lower
Michigan and the majority of the system precipitation shifts northeast as
well. Track of the developing h850 low would support more snow
over north central Wisconsin. While further snow accumulation may
wrap around this system through Thursday...winds will be on the
increase to possible Wind Advisory levels at least. Depending on
snowfall Tuesday and Wednesday and going snow Thursday...various
headlines may be needed including Wind Advisory headlines where
snow not an issue. At this time...north central Wisconsin appears
to be most impacted from this system due to more snow is anticipated
before the winds increase. Would like to see more model
consistency from run to run and model to model before adding
better detail of the impacts to affect the region. The warmer
solutions if correct may also impact the river and lake ice

Due to limited confidence issues with days 3-5...low confidence
issues expected for day 6-7...due to lack of consistency with a
trailing system along the baroclinic zone. Runs 24 hours ago were
well south...but morning runs track the system back over the
Great Lakes region with the European model (ecmwf) much more robust with a winter
event next Friday into Saturday.

Anyone with travel plans next week should stay tuned to the latest

Aviation...for 06z taf issuance
issued at 1035 PM CST Friday Dec 19 2014

A large variety of conditions continue across the area late this
evening. Low clouds slowly developing/moving east-northeast into NE wisc.
Clouds will continue to increase and lower over the entire area
during the overnight. Cloud cover should remain across the area
Saturday with ceilings lowering again Saturday night.


Grb watches/warnings/advisories...


Short term.....Rdm
long term......tdh

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