Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Green Bay WI
1105 PM CST sun Feb 7 2016
Updated aviation portion for 06z taf issuance
Short term...tonight and Monday
issued at 331 PM CST sun Feb 7 2016
Region radar mosaics showed a large area of snow moving into
northwest Wisconsin this afternoon. Water vapor satellite
imagery showed a middle level cyclone around the Minnesota arrowhead
early this afternoon...and surface observations indicated a low
pressure system over Western Lake Superior.
The 500mb low is forecast to pass through most/all of Wisconsin
tonight as a western noam ridge amplifies. At the same time...the
surface system is expected to make its way across Upper Michigan.
Snow will move into the area as these features pass...and once
they do so there will be additional lake effect snow in northern
Wisconsin as colder air wraps around the back side of the
Still expect a rather long period of light snow through Monday
with some accumulation. Have left the advisory in place for Vilas
County but snow totals appear borderline and am not sure winds
there will be strong enough to produce much blowing snow. Will
have to wait and see.
Expect temperatures to remain above normal tonight and Monday.
Long term...Monday night through Sunday
issued at 331 PM CST sun Feb 7 2016
Eastern Continental U.S. Will remain dominated by broad trough through the
extended portion of the forecast with the western Great Lakes
remaining in northwesterly upper flow. Occasional pieces of
shortwave energy will drop southeast out of Canada into the
northern Continental U.S. But timing and location of these features still
uncertain. With exception of the Lake Superior snow belt
region...any preciptation during this period will be light with
temperatures remaining below normal into next weekend.
By 00z Tuesday...pronounced upper-level low forecast to be situated
somewhere over southwest lower Michigan...with elongated and
negatively tilted surface low pressure trough stretching from Lake
Ontario northwestward to Eastern Lake Superior. Upper low and
associated surface reflection forecast to move slowly and meander
over the eastern Great Lakes through Wednesday morning. Deeper
moisture associated with this system along with weak upper-level
impulses rotating around the primary upper circulation will lead
to an extended period of light snow or light snow shower activity.
Still expecting maybe another inch of snow overnight Monday into
Tuesday...especially over the Fox Valley where low to middle-level
forcing and deeper moisture will reside. In addition...pressure
gradient forecast to tighten Monday evening and remain relatively
strong into Wednesday morning.Thus some blowing and drifting of
the newly fallen snow seems likely especially overnight Monday
into Tuesday morning.
Meanwhile lake effect snow showers will still be ongoing over
Vilas County with an additional couple of inches possible by
Tuesday evening. However...the intensity of the les bands will
gradually diminish later in the day on Tuesday as drier air and
more robust subsidence work into that region. Forecast trajectories
will remain somewhat favorable for a continued chance for light
les activity over Vilas County even into Wednesday but accumulations
expected to be minor by then. May need to consider extending the
advisory for Vilas County beyond Monday evening. Will let
subsequent shift take a closer look at that possibility.
Will continue to lean toward the more amplified pattern suggested
by the European model (ecmwf) for late in the work week...characterized by deeper
trough holding firm over the eastern Great Lakes. This would tend
to shun any fast-moving clipper systems to south of the forecast
Taking a peak at longer range guidance it appears amplified
pattern may start to break down by the end of next weekend
allowing for a moderation in temperatures...and perhaps a weak
system to impact the area around Sunday. In the meantime daily
average temperatures will remain below normal through the upcoming
work week with highs likely not to climb out of the teens after
Tuesday. Coldest morning still appears to be Thursday with surface
ridge nearby...lighter winds and minimal cloud cover.
Aviation...for 06z taf issuance
issued at 1105 PM CST sun Feb 7 2016
Ceilings continue to lower across the taf sites from west to east as a
middle level shortwave and surface low pressure system track through
the western Great Lakes. Conditions have been slow to
lower...especially across the eastern taf sites where VFR
conditions remain. However upstream observations show these
conditions should eventually lower later tonight and into Monday
morning with snow showers as this system tracks through. Veering
winds will result in lake effect snow showers over northern
Wisconsin overnight and into Monday.
Winter Weather Advisory until 6 PM CST Monday for wiz005.