Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Green Bay WI
546 am CST Monday Nov 24 2014
Updated aviation portion for 12z taf issuance
Short term...today...tonight...and Tuesday
issued at 413 am CST Monday Nov 24 2014
Very unusual and challenging winter storm. Phasing
of two upper jets will produce deepening surface low that rockets
off to the northeast today and tonight. It does leaves behind a
surface trough back into our area and more importantly the storm
is so vigorous that it will drive moisture all the way from the
eastern United States across southern Canada and then southwest
into Wisconsin. 850 mb moisture transport vectors show this
nicely. This should result in an area of significant snow across
central and east central Wisconsin with light snows elsewhere.
The numerical weather prediction models typically have difficulty
with these phasing systems and so do we forecasters. Was initially
reluctant to issue a warning for east central Wisconsin because of
the uncertainty but the snow will be the first real snow of the
season in most of this area and will arrive around the late
afternoon and evening drive time. Winds will increase and cause
blowing and drifting snow this Evening. Lake effect potential not
as impressive for Vilas County though we decided to keep the
The snow will end late tonight with partial clearing Tuesday.
Highs will be much colder than the past couple of days and be
around 10 degrees below normal.
Long term...Tuesday night through Sunday
issued at 413 am CST Monday Nov 24 2014
The latest GFS ensemble mean continues to indicate above normal
heights moving into the western Great Lakes during the first week of
December...as the dominant northern stream finally retreats. Until
this occurs...the first item of concern is a potential clipper
during the Wednesday and Wednesday night period. Models are
trending south with this clipper...but there remains timing/track
issues. The latest sref is the closest to middle of the Road...and
given the recent consistency problems of the models...will try to
minimize error. Thereafter...models are seemingly all over the
place and its difficult to be confident in the details of any
solution. Will just side with the superblend.
Tuesday night through Wednesday night...a digging shortwave in the
left exit region of a beefy 140kt jet stream will dive from the
northern plains to the central Mississippi Valley Tuesday night.
Clouds will be on the increase ahead of the system...but precipitation
chances look too far to the southwest. Though most of the energy
from this system will pass over central or southern
Illinois...guidance is still indicating an inverted trough moving
across western Wisconsin in the morning...and across central
Wisconsin during the afternoon. Will lower precipitation chances during
the morning...and reduce them across the east during the afternoon.
The inverted trough will continue to move east across eastern
Wisconsin Wednesday night which will keep light snow in the
forecast. Thinking less potential for accumulations than last
night...and will show under an inch in the forecast. But the area
could also miss any snow entirely. The lone exception will be Vilas
County where conditions will be supportive for lake effect snows.
Some uncertainty about wind direction but at least the northwest
part of the County could get an inch or two.
Rest of the forecast...think most of the light snow will have exited
the region except for the snow belt...but the snow there too should
be winding down. The rest of Thursday and Thursday night should be
dry thanks to high pressure. Then should see a chance of warm
advection snows on Friday and Friday night across the north. Once
the trailing cold front moves through Saturday or Saturday
night...Arctic high pressure will return for Sunday into Monday.
Aviation...for 12z taf issuance
issued at 545 am CST Monday Nov 24 2014
IFR ceilings expected across much of the area today.
Rain or drizzle will change to snow from west to east. Moderate
snow and LIFR conditions possible during the late afternoon and
evening hours roughly south of a Wisconsin Rapids to Marinette
line. Snow will diminish overnight with partial clearing expected
Winter Storm Warning from noon today to 6 am CST Tuesday for
Winter Storm Warning from 3 PM this afternoon to 6 am CST
Tuesday for wiz020-022-031-038>040-049-050-074.
Winter Weather Advisory from 10 am this morning to 3 am CST
Tuesday for wiz030-035.
Winter Weather Advisory from 3 PM this afternoon to 3 am CST
Tuesday for wiz010-018-019-021-073.
Lake effect Snow Advisory from noon today to 6 am CST Tuesday