Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
325 am CST Monday Jan 26 2015
Today and tonight...forecast confidence medium to high.
A couple shortwave troughs from Minnesota into Canada will track southeastward
across southern WI later today and tonight. A well organized warm advection
pattern ahead of the trough and frontogenesis will generate a band
of snow from west to east from the morning into the afternoon. The
surface trough will linger through the night along with the passage of
the shortwave trough so very light snow will linger especially over
eastern WI. The models do show a weakening of this system as it moves
across the state so snow totals will be less over eastern WI. Snow accumulate
forecast ranges from one inch over eastern WI to 1-2 inches over south
central WI. Forecast soundings showing the potential for some freezing
drizzle mainly over south central WI in the wake of the main area of
light snow. The impact of any freezing drizzle will likely be
minimal with the snow falling first and Road treatments occurring.
Tuesday - confidence...medium
500 millibar negative vorticity advection starts to work into the area. Low level thermal
trough lingers so expect a good deal of cloud cover to linger.
Hint of inverted surface trough early then high pressure dominates
across the western Great Lakes.
Wednesday - confidence...medium
with the high pressure ridge into the Ohio Valley a return
southerly flow sets up. Shortwave activity remains in the northern
plains with surface low development focused near southern Iowa. Decent
warm air advection ahead of this system sends 850 temperatures above zero. The European model (ecmwf) has
precipitation well north of the area...the NAM looks wetter across southern WI
with splotchy 0... the GFS more of a compromise with precipitation
across northern WI. Will leave dry forecast intact. 925 temperatures suggest at
least middle 30s for highs.
Wednesday night and Thursday - confidence...medium
models in decent agreement in bringing precipitation to the area as
upper dynamics approach and low pressure passes south of WI. Quantitative precipitation forecast
amounts not that impressive...less than 0.10. Still potential for
some mixy precipitation prior to 6z with the warm layer into southern WI.
After 6z...the low wraps colder air into the air to convert any
lingering mix to light snow. 00z European model (ecmwf) keeps light precipitation around
longer while the NAM and GFS tend to wrap things up in the
morning. Getting snow amounts of around a half to 1 inch.
Friday - confidence...medium
surface high quickly takes hold midday dominating the western
Great Lakes. High shifts east later in the day though any
influence of next approaching system holds off to our west.
Saturday - confidence...low
models show cold front swinging through the area with the European model (ecmwf)
quicker and more assertive on cold air intrusion in the wake of
the frontal passage. Blended quantitative precipitation forecast amounts are again on the light side with
the GFS showing more widespread coverage and the European model (ecmwf) just
clipping the NE County Warning Area.
Sunday - confidence...low
still considerable disparity on the duration and extend of
potentially Arctic cold low level thermal trough. The European model (ecmwf) is
still showing 925 temperatures of -20 to -22c well entrenched while the
GFS 8-10 degrees warmer and already hinting at some return warm air advection by
later in the day. Blended approach still best way to go at this
Aviation/12z tafs/...MVFR ceilings via lake effect stratocumulus will
linger early this am over far southeast WI...but should clear around
sunrise as the boundary layer flow becomes southerly. The light snow will
then begin to move slowly from west to east across southern WI beginning
around 16z at kmsn and 20z for the southeast WI taf sites. Visibilities within the
snow will range from 1-3 miles with ceilings falling to 1 kft or below
at times. Patchy freezing drizzle may occur over south central WI
from the afternoon into the evening. With a weak surface trough over the
area tonight...the low ceilings and visibility restrictions will continue even
after the snow or freezing drizzle ends.
Today/tonight and aviation/marine...gehring
Tuesday through Sunday...collar