Scientific Forecaster Discussion
fxus63 kmkx 162305
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
505 PM CST Sat Nov 16 2019
The short range forecast is on track for tonight into Sunday
morning. A quiet and rather pleasant evening is taking shape.
VFR conditions are expected through mid morning on Sunday. Then
look for an area of light snow to push into south central
Wisconsin after 15z Sunday, becoming mixed with mixing with then
changing to rain as it pushes east through the day. Ceilings will
quickly lower to MVFR then IFR levels with the developing
precipitation. The lower ceilings will reach kmsn by 17z Sunday and
kmke/kues/kenw by 20-21z Sunday. Those lower conditions will
persist through Sunday evening.
Any snow accumulations are expected to be less than 1 inch,
especially across the southeast where temps will be warmer during
the day. There was concern in previous forecasts for a period of
freezing drizzle, but that is no longer expected due to the milder
Previous discussion... (issued 249 PM CST Sat Nov 16 2019)
Tonight through Sunday night...forecast confidence is moderate.
Lake effect clouds will continue to slowly thin from mke to sbm
through the afternoon. Intermittent broken high cloud cover will
also continue through the afternoon into the evening.
For tnt, sly winds, warm advection and thicker cloud cover will
make for a milder night than previous ones. The upper trough that
will move into the Great Plains later today will split into two
focused areas. The more substantial upper wave will dive sewd
toward the middle MS River Valley, while a nrn upper wave will
track across srn Canada with a weakening sfc low. At the sfc, a
weak cold front will move ewd across srn WI from late afternoon
into the evening.
A narrow N-S band of light snow will move into areas west of kmsn
for the morning daylight hours, but weaken as it moves east due
to weakening frontogenesis. A new focused area of lgt rain and
snow will then develop from Illinois into se WI for the afternoon. Sfc
temps will warm into the middle to upper 30s, making pcpn types a
mix of rain and snow. Relatively mild temps will continue into
the evening with small chances for drizzle, while freezing drizzle
will be very unlikely.
Monday through Tuesday night...forecast confidence is moderate.
500 mb flow remains northwesterly across the region during this
period. Models are bringing a fairly potent vorticity maximum
southeastward and differential cva into the area later Monday
night into early Tuesday morning. Some focused warm air advection
tries to push into the area during this time as well. Upward
vertical motion is rather modest.
Forecast soundings from NAM/GFS are showing varying amounts of
column moisture and low quantitative precipitation forecast Monday night into early Tuesday. For
now, kept mainly small pops for Monday night, when moisture and
upward vertical motion would coincide. Left out mention of light
freezing drizzle for now for Monday night, as there is model
uncertainty with the amount of ice crystals available.
Otherwise, mostly cloudy skies Monday into Tuesday morning should
gradually give way to partial clearing Tuesday afternoon and
night. Temperatures should warm from the upper 30s Monday into the
lower 40s Tuesday, still a little below seasonal normals.
Wednesday through Thursday...forecast confidence is moderate.
GFS/European model (ecmwf) continue to show some differences with the low track for
Wednesday night into Thursday across the region. The GFS is more
northerly, taking the low from the south Central Plains Wednesday
into northeast Iowa Wednesday night, then across southern
Wisconsin into lower Michigan on Thursday. The gfe ensembles are a
little further to the southeast with the low track than the
operational GFS, and the gefs mean quantitative precipitation forecast shows the operational GFS
is on the high end with its quantitative precipitation forecast amounts.
The European model (ecmwf) and Canadian are further southeast with the low track,
taking it mainly through northern Missouri into northeast Illinois
Wednesday night, into Southern Lower Michigan Thursday. Thus, with
this and the GFS ensembles/gefs quantitative precipitation forecast trends, sided more with these
models than the operational GFS. The southwesterly low level jet
should transport a decent amount of moisture into the area
Wednesday night, with some possible jet streak divergence coupling
by 12z Thursday.
Enough upward vertical motion and moisture to keep likely pops
going for later Wednesday night into Thursday morning, especially
in eastern and southern parts of the area. Thermal profiles
suggest a rain/snow mix in the northwest half of the area
Wednesday night, with mainly rain to the southeast. A mix may then
shift southeast Thursday, as temperatures cool with cold air
advection as the low passes by to the southeast. At this time, not
seeing a big impact with snow, but we'll see how the low track
trends as we get closer. There could be some wet, slushy light
accumulations that affect the Thursday morning commute in northern
parts of the area.
Temperatures Wednesday should be in the lower 40s ahead of the
low, with temperatures near or a little below seasonal normals
Wednesday night into Thursday.
Thursday night through Saturday...forecast confidence is moderate.
Models are a little less in agreement with timing and placement
of features in this period across the region. However, it appears
that 500 mb flow will remain northwesterly over the region, with
possible vorticity maxima shifting through at times. No major
systems appear to move through the region during this time, which
could change being this far out in the future. Temperatures appear
to be near or a little below seasonal normals.
Aviation(21z taf updates)...
Bkn015-025 stratocumulus via lake effect will continue to
gradually dissipate from mke to sbm through the afternoon. VFR
conditions elsewhere and over ern WI for tnt. Light rain and snow
will then gradually move ewd across srn WI on sun. Cigs will fall
to 600-1900 feet over south central WI during the morning daylight
hours, then continue into se WI for the afternoon.
High pressure of 30.7 inches over southwest Quebec and southern
Ontario will move to New England into tonight. Modest southeast to
south winds will prevail into Sunday, as low pressure of 29.7
inches moves across Ontario and the northern Great Lakes. Light to
modest westerly winds will follow for sun nt-Mon, following the
passage of a weak cold front. A Small Craft Advisory is in effect
from Port Washington and nwd for later this evening into sun am
for 3 to 5 foot waves.
Lm...Small Craft Advisory from 9 PM this evening to 10 am CST Sunday