Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
326 PM CST Thursday Feb 26 2015
Tonight - confidence...high
Middle level positive vorticity advection translates to our south
during the overnight hours. North winds will continue to slowly back
towards a more westerly direction this evening and overnight as a
1004 mb high pressure system moves into the region. This high
pressure will increase subsidence and clear our skies...leading to
very chilly temperatures. 925mb temperatures look to be near -18 to -
19 across the forecast area. Lows tonight could reach into the teens
below zero. Wind chill values look to approach 20 below zero...but
remain above this value. Winds will be extremely light...with
sustained winds in the lower single digits. Issued a Special Weather Statement to
address the cold temperatures tonight.
Friday - confidence...high.
Arctic high pressure will swing through the region Friday to our
south. With associated subsidence...and a fairly dry airmass moving
into place...conditions will be very quiet. Winds will strengthen by
tomorrow afternoon as the pressure gradient tightens and continues to
back towards a more southwesterly direction as the high pressure
moves off to the east.
Friday night and Saturday - confidence...high
High pressure will move from Indiana to the East Coast. Winds will
be light out of the southwest. With min temperatures in the negative single
digits expecting wind chill values -15 to 19 Saturday morning.
Saturday night through Sunday night - confidence...high
A weak trough of low pressure will move across the region on Sunday.
Warm air advection starts on Saturday on southwest flow. The main
core of precipitation will be south of the state associated with right
entrance region of 140 knots jet and broad area of low pressure to the
south. Weak 700mb Omega moves across the region on Sunday but
greatest forcing at this level is also to the south. Models differ
on the timing of the precipitation. The European model (ecmwf) is the fastest bringing it in
Saturday night but all models show light snow on Sunday. The far
south could see a couple inches. Upper level short wave and surface
cold front passes through Sunday evening with dry weather overnight.
Monday through Tuesday night- confidence...moderate
High pressure will pass overhead on Monday as a 500mb ridge sets up
over the region. Heights are forecast to be around 555mb. Low
pressure is then shown to develop over the Central Plains and move
near or across southeast WI on Tuesday or Tuesday night. The 12
European model (ecmwf) has come more in line with the GFS low track. There will be
plenty of lift associated with right entrance region of a 150 knots jet
and upper level shortwave. Precipitation is expected Tuesday and Tuesday
night. Precipitation type is uncertain. The GFS is stronger...quicker...and
warmer with the system.
Strong warm air advection will occur ahead of this system. The GFS
shows low level temperatures reaching 3-6 degree c across the eastern two
thirds of the County Warning Area yielding rain Tuesday. The European model (ecmwf) and Canadian
are colder indicating snow or sleet in far southeast WI. There is better
agreement on snow across the northern forecast area. Model
consensus indicates highs in the lower 30s on Tuesday.
Wednesday and Thursday - confidence...high
High pressure and dry weather will dominate the region as a deep
trough drops across the state. Middle level flow becomes west
northwest by the end of the week.
Expect mainly VFR conditions as a strato cumulus deck will dissipate later
this evening and overnight as low level lapse rates flatten out by
early this evening. An area of high pressure will also bring
subsidence to the region...assisting in dissipating clouds. This
high pressure system will also help to shift the winds from a more
northerly direction this afternoon and evening to a more westerly
direction later tonight. Conditions will be cold tonight as well as the
clouds dissipate and clearer skies take hold.
Winds will continue to shift from a more northerly direction to the
northwest during the evening and overnight hours as an area of high
pressure will move into the region. Gusts will be in the upper single
digits into the teens this evening and overnight. Very chilly
temperatures will be in place later tonight as winds weaken and skies
clear over the region.
Tonight/Friday and aviation/marine...jts
Friday night through Thursday...marquardt