Scientific Forecaster Discussion
fxus63 kmkx 090939
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
339 am CST Fri Dec 9 2016
Today and tonight...forecast confidence is high.
The broken stratocumulus and flurries over portions of south central
WI will continue to decrease from north to south this morning.
Otherwise partly cloudy skies are expected until late today or
tonight when middle to high clouds will overspread the region. This
is associated with mid level warm advection along with a couple vort
maximums passing across Iowa and Illinois. Flurries may be possible. Weak
cold advection today will keep temps in the lower 20s. Temps for
tonight are challenging with the timing of the thicker cloud cover
critical to when temps will bottom out. Upper single digits to teens
is a good compromise of the models for now.
Saturday through Monday...forecast confidence is moderate.
Models have trended toward one long duration snowfall this weekend.
The consensus is for 5 to 9 inches but it could be more. Due to snow
accumulating over a 30 to 36 hour time period this is looking like
an advisory type event right now. Snow probabilities are available
Cyclogenesis occurs east of The Rockies on Saturday with strong warm
air advection ahead of it pushing into SW WI in the evening. There is
favorable upper divergence from a 115 kt jet. Models are in good
agreement with snow spreading across southern WI during the evening
along this baroclinic zone and continuing through the night as low
level frontogenesis slides through the region.
The surface low moves toward the region on Sunday passing southeast
of the state Sunday night. All models have come on board with this
scenario so it looks like snow will continue through the day on
Sunday. A shortwave approaches the region and the upper jet recharges
so upward vertical motion continues. The low moves away on Monday
bringing and end to the precipitation.
Temperatures will increase Sunday and Monday with the strong push of
warmer air with this system.
Tuesday through Friday...forecast confidence is high.
There are chances for light snow at times. There is much
higher confidence in colder temperatures. A Deep Cut off low drops
down from Canada as Arctic high pressure settles in at the surface.
It will be cold with highs in the single digits starting on Tuesday
with daytime wind chill values near to below zero. Below normal
temperatures will likely extend beyond this period.
Aviation/12z tafs/...broken stratocumulus at 3-3.5 kft and
flurries will slowly decrease from north to south for areas west of
Madison this morning. Otherwise scattered stratocumulus are expected
today with broken mid to high clouds for late today and tonight.
Marine...a Small Craft Advisory remains in effect until 6 am
today. The gusty wnwly winds will gradually weaken this morning.
However, sustained modest wly winds will continue for today and
tonight but weaken further on Sat.
Lm...Small Craft Advisory until 6 am CST early this morning for