Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Green Bay WI
1151 am CST Monday Feb 8 2016
Updated aviation portion for 18z taf issuance
Short term...today...tonight...and Tuesday
issued at 332 am CST Monday Feb 8 2016
Slow motion clipper system continues to drop into the area today.
Light snow will continue to spread over the area as the cold and
saturating air mass spreads east. The snow growth region also expands
today into tonight and Tuesday for continues light snow or
flurries. Most locations can expect 1 to 3 inches from today into
Tuesday. Pieces of energy rotating around the upper low may produce
locally higher amounts...with one piece dropping into southwest
Wisconsin early this morning and another currently enhanced with
the lake effect over far northwest Wisconsin.
Even though model data suggests some drying works into at least
western areas later Tuesday...deep snow growth region with steep
surface lapse rates will could produce pockets of moderate snow
showers. So will continue higher end probability of precipitation for this period.
Observations indicate lake enhanced snows underway across the far
north...and conditions will linger into tonight...so will extend
the advisory for Vilas with the emphasis the northwest portion.
Most locations will see morning or early day highs otherwise a
downward trend in temperatures will start the new work week.
Long term...Tuesday night through Sunday
issued at 332 am CST Monday Feb 8 2016
The amplified pattern consisting of the western noam upper ridge/eastern noam
upper trough to persist through middle-week before the upper ridge weakens and
shifts eastward in response to a new upper trough to hit the West Coast by
next weekend. The prevailing northwest flow aloft over the Great Lakes
wil usher in an Arctic intrusion with temperatures well below normal
during the entire extended forecast. Precipitation amounts will be below normal
as Gulf moisture is non-existent and there are no signs of any
siginificant storms on the horizon.
Lake effect snow showers over northern WI continues to be the primary concern
Tuesday night...especially for Vilas County as conditions remain
favorable. On the plus side...trajs are ideal (n-nw)...Delta-T
values are in the middle 20s and surface trough lingers near Lake Superior.
The one big negative will be the low inversion heights that would
limit snow amounts. Still believe that the snowbelt region of
Vilas County will see snow showers and have raised probability of precipitation into the likely
category with an inch or two of accumulation. The rest of NE WI
should be fairly quiet with only widely scattered snow showers and little
in the way of any accumulation. Min temperatures to range from the single
digits below zero central WI...single digits above zero eastern WI. Add
in a gusty northwest wind and wind chills could approach advisory criteria
over parts of central WI.
The lake effect is forecast to persist through Wednesday...but be in a gradual
diminishing Mode as an area of hi pressure builds into western WI and
advects drier air into the western Great Lakes. Parts of Vilas County
could see up to an additional inch of accumulation...again limited
by low inversion heights. Otherwise...parts of central/E-cntrl WI
could see some sunshine on Wednesday as cyclonic flow weakens and the
surface hi approaches. Maximum temperatures may not make it out of the single
digits above zero over N-cntrl/parts of central WI...while eastern WI
only reaches the 10 to 15 degree range.
The surface hi is prognosticated to stretch from Lake Winnipeg southeast through western WI
to the Tennessee Valley Wednesday night...bringing a decrease in clouds and
diminishing winds to NE WI. Only exception would be Vilas County
where lake clouds/perhaps a few leftover snow showers to exist. The
amount of clearing will be key as to how cold we can get considering
the lighter winds and some fresh snow cover. Look for min temperatures to
range from zero to 5 above near Lake Michigan...to near 10 below zero over
the colder spots of N-cntrl/central WI. This broad area of hi pressure
to east slightly farther east on Thursday and back the winds to a west-northwest
direction...thereby finally allowing north-central WI to see the sun.
Expect to see a lot of the sun for the rest of the forecast area...
although temperatures to remain 10 to 20 degrees below normal. This would put
maximum temperatures in the 10 to 15 above zero range central WI...generally
middle teens eastern WI.
The benign and cold weather pattern is forecast to hold sway through Sat
as the hi pressure continues to dominate NE WI. There will be a weak system
(mid-level shortwave with frontogenetical forcing) that should
stay to our west and south on Friday...but could veer the winds northwest
again and lead to more clouds/small chance for lake effect snow showers
over Vilas County. The rest of the area to remain mostly clear to
partly cloudy and cold with little change in the air mass. Temperatures
to hold well below normal.
The hi pressure finally does shift to our east by Sat night...allowing
winds to come around to the S-southeast direction with warmer air to try
and push back into WI. There may be a gradual increase in middle/hi
clouds later Sat night as this warmer air aloft arrives. The next
real chance of seeing precipitation across the region would be Sunday at the
earliest as a shortwave trough pushes across the upper Midwest. Timing
of this feature varies a bit among the models...but plenty of time
to sort out these differences in the coming days.
Aviation...for 18z taf issuance
issued at 1151 am CST Monday Feb 8 2016
Ceilings across the area were mainly in the MVFR category...and visibilities
were mostly VFR. Visibilities dropped to MVFR...and IFR at times...in
snow showers. Snow showers were most widespread in eastern
Wisconsin and in the Lake Superior snowbelt at midday. Expect
coverage to increase later this afternoon into at least the early
evening....before things winds down in all but the snowbelt.
Increasing northwest winds are expected for today as a cold
front...that was near the Lake Michigan shoreline late this
afternoon...continues to push eastward.
Winter Weather Advisory until midnight CST tonight for wiz005.