Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Green Bay WI
515 am CST Sat Feb 6 2016

Updated aviation portion for 12z taf issuance

Short Sunday
issued at 305 am CST Sat Feb 6 2016

The last of a parade of weak clippers will slide over eastern
Wisconsin early this morning. Visibilities indicate flurries mainly
falling from this departing system. Otherwise focus turns to a
stronger system slowly dropping into the area for the remainder of
the weekend.

The previous clippers the last few days were always followed with
a clearing trend...however that may not be the case today.
Stratus clouds becoming more widespread over Wisconsin into
Minnesota in a region of warm air advection ahead of slowly evolving storm
system moving into the northern plains today...and eventually
Great Lakes region remainder of the weekend.

Precipitation expected to be light on the onset with the ongoing warm air advection
tonight due to saturation issues. Forecast soundings trending
toward a mix precipitation type later tonight and especially into Sunday.
Forecast soundings for at least the southeast half of the forecast
area on Sunday suggests a mix of zr-/S- but forecast temperatures above
freezing and would support a r-/S-.

Warm start this morning should allow temperatures to climb above norm
levels today...and any significant breaks in the clouds...then
much above. Expect near steady temperatures tonight with continued warm air advection
through Sunday.

Long term...Sunday night through Friday
issued at 305 am CST Sat Feb 6 2016

Highly-amplified flow consisting of strong upper ridging over western noam
and deep upper troffing over east-central noam to persist through the middle
of next week before both features weaken a bit for the latter part
of next week. Main weather feature of interest continues to be the
movement of a strong clipper system and associated closed upper low
that lw impact the Great Lakes from Sunday into possibly early
Tuesday. This system will likely produce some light snow for several
periods...followed by an intrusion of Arctic air and lake effect
snow showers for north-central WI.

Snow chances to increase across NE WI Sunday night as the surface low
tracks east-southeast into the Great Lakes...accompanied by a cold front and a
nearly closed upper low. While the snow is expected to be light with
accumulations ranging from one-half inch near Lake Michigan to an inch
and a half over north-central WI...this may be enough to generate slippery
stretches on area roadways for the morning commute. Min temperatures to
range from the lower 20s north-central the upper 20s eastern WI.

This system does not move much headed into Monday...mainly due to a
storm moving up the East Coast into New England. NE WI to reside
on the cyclonic side of the Great Lakes system with several
individual shortwaves rotating around the upper low. Anticipate
additional light snow to fall over the region with accumulations
at an inch or less. This fresh snow...coupled with increasing north-northwest
winds will tend to blow/drift the snow around and possibly impact
the evening commute with reduced visibilities. Onset of cold air advection will temper
much of a temperature rise on Monday despite the mild start to the
day. Look for maximum temperatures to only reach the lower to middle 20s
N-cntrl...but lower 30s for east-central WI.

Light snow...or more likely just snow showers...should linger through
Monday night as the system edges eastward into the eastern Great Lakes. Do not
see much more in the way of accumulation with most areas under
one-half inch at best. This would bring entire storm totals into
the 1-3" range through Monday night. The exception will be north-central WI where
lake effect snow showers will persist since trajs are favorable and
Delta-T values to reside in the lower 20s. Parts of Vilas County could
see totals of 3-5" combined from Sunday night through Monday night. Min
temperatures for Monday night will range from 5 to 10 above central the
upper teens near Lake Michigan. Arctic air intrusion will continue to overspread
the region on Tuesday as 800 mb temperatures fall into the -18c to -20c range.
Prevailing north-northwest winds...aided by a weak west-to-east orientated
surface trough...should allow for More Lake effect snow showers to impact
north-central WI. The rest of the forecast area should mainly be dry under
mostly cloudy skies. Cannot totally rule out a few snow showers near
Lake Michigan that would drift S-southeast from Lake Superior. Temperatures will fall to
below normal levels on Tuesday with readings only from 10 to 15 above around 20 degrees near Lake Michigan.

These lake effect snow showers should carry over through Tuesday night and
may even extend into Wednesday as the persistent northwest flow aloft...coupled
with Arctic little sign of letting up. A ridge of hi pressure
is prognosticated to begin building eastward toward the western Great Lakes region on
Wednesday and start to back the surface winds toward the W-NW. This would
gradually keep the Better Lake effect potential north of the Michigan
border. Otherwise...expect to see some sunshine return to the
area...although with Arctic air in place...temperatures to remain double
digits below normal (upr single digits to lower teens north...mainly
middle teens south).

This area of hi pressure is forecast to mvoe into the western Great Lakes Wednesday
night and bring a very cold night to the region. May need to lower
temperatures down further with sub-zero mins north and part of central
WI...single digits above zero east. Quiet conditions to prevail on
Thursday with the surface hi in control of NE WI weather. Models continue to
show a weak clipper to race eastward roughly along the U.S.-Canadian
border and drag a cold front through WI on Friday. Look for clouds to quickly
increase Thursday evening with an area of light snow forecast to arrive
later Thursday night that would continue into Friday. Along with the snow chances
would be another reinforcing shot of Arctic air that would persist
into next weekend.

Aviation...for 12z taf issuance
issued at 515 am CST Sat Feb 6 2016

Low level moisture trapped in the lower levels have produce
widespread IFR conditions over central and east central Wisconsin
overnight...with ceilings lowering to MVFR levels early this morning
over eastern areas. Little change expected this morning...some
improvement possible this afternoon into tonight as southwest
winds and mixing increase.

Grb watches/warnings/advisories...


Short term.....Tdh
long term......kallas

National Weather Service Glossary of Abbreviations