Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
333 PM CST Wednesday Nov 25 2015
Tonight and Thanksgiving...forecast confidence...high
Temperatures and moisture will continue to increase into Thursday
under a southerly low level flow. Precipitable water values will
rise to around 1.25 inches by Thursday afternoon...very high on
the scale for this time of the year. With plenty of moisture and
forcing as the trough/cold front move through...still looks like a
good shot of rain developing by Thursday afternoon. Will probably
see a few showers or drizzle tonight into Thursday morning as the
atmosphere continues to saturate.
Trended temperatures and dewpoints toward the GFS/ECMWF/Canadian
solutions for tonight and tomorrow...as the NAM seems much too
cool...possibly impacted by the snow cover. Even with the clouds
and rainfall...will see highs in the 50 to 55 range most places
tomorrow...well above average values for Thanksgiving.
Thanksgiving night through Sunday...forecast confidence high.
A warm conveyor belt with a southerly 50 knots low level jet and precipitable waters rising to 1.1
inches will develop into the region...ahead of the upper troughs
over southern Canada and the Great Basin...for Thursday after and night. At
the surface...a surface trough/cold front will gradually shift east-southeastward
across southern WI Thursday nt. Well organized and fairly strong low to middle
level frontogenesis is depicted with continued high quantitative precipitation forecast values.
The rainfall forecast for Thursday after and night will range from 1-1.40
inches. Expect several rivers over far southern WI to rise and reach
bankfull stage on Friday or over the weekend. Only a couple rivers
may reach minor flood stage. Will let the hydrologic outlook
expire at 22z since overall impact will be minor. The river
statements will address the trends of each river affected by
bankfull stage or minor flood stage. The cold advection late Thursday
nt and Friday am will probably lead to mixed precipitation on the back edge of
the precipitation area but this precipitation would be light with little to accumulate of
snow or ice. Northerly winds and cold advection will weaken Friday nt with
a west to East Ridge of high pressure over the Great Lakes for the
weekend. Mild temperatures for Thursday and Thursday nt will return to near normal
for Friday and the weekend.
Long term...Monday through Wednesday...forecast confidence
The large upper low currently over the Great Basin will eject northeastward
to the Great Lakes for Monday nt and Tuesday. Expect some cyclogenesis as
is does so but the track of the low and thermal profiles are in
question. However...there will be a cooling trend with rain
chances becoming snow chances during this period. High pressure
and cool temperatures for Wednesday.
Ceilings will gradually go down this evening into tonight as moisture
continues to increase. Delayed the onset of MVFR conditions given
upstream observation. Will probably also eventually see some lower visibilities
tonight into Thursday as dewpoints continue to rise and there is
still snow in a few locations.
Rain chances will then increase overnight into Thursday...with
widespread rainfall arriving by Thursday afternoon. Ceilings will
likely be very low through the much of this event...with some
lower visibilities at times.
Kept Small Craft Advisory times as is for now. Conditions look
pretty borderline tomorrow though...so may need to consider
shortening the end times. Winds and waves will eventually pick
back up Thursday evening into Friday...so more headlines will be
Lm...Small Craft Advisory until 6 PM CST Thursday for lmz645-646.
Small Craft Advisory until noon CST Thursday for lmz643-644.
Tonight/Thursday and aviation/marine...ddv
Thursday night through Wednesday...gehring