Scientific Forecaster Discussion
fxus63 kmkx 142325
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
525 PM CST Thu Nov 14 2019
Clouds have cleared all but the far southeastern corner of the
forecast area. Expect a period of clear skies this evening, before
more cloud cover moves in late tonight with the weak front.
Temps will likely fall rather quickly this evening given the clear
skies, before leveling off late as the next batch of clouds moves
MVFR stratus has cleared all but far southeastern Wisconsin at
this hour, and should continue to push south of the area this
evening. A weak frontal boundary will pass through the area late
tonight, bringing with it another area of stratus. This area of
clouds should be fairly narrow, and will likely be dissipating as
it moves through the area. Ceilings will likely bounce between scattered
and broken at times.
Initial west winds this evening will become more northerly
tomorrow behind the front. Winds will continue to veer with time,
becoming northeasterly tomorrow evening as high pressure pushes
through the region.
Previous discussion... (issued 335 PM CST Thu Nov 14 2019)
Tonight and Friday...forecast confidence is high.
Broken stratus is on track to clear from the north and west into
the early evening. At least a light wly sfc flow will prevail tnt
but with a wnwly low level jet of 35 kts developing ahead of an
approaching and weak Canadian cold front. A narrow band of stratus
may develop just ahead and along the cold front for early Fri am
with some clearing after the cold frontal passage later Fri am.
Lgt nly winds and sunshine will prevail for the afternoon with
temps warming into the middle to upper 30s.
Friday night through Saturday... forecast confidence is high.
High pressure will move off to the east. Return flow around the
high with southerly winds will keep mild air in the area. A
lingering lake effect cloud/shower band over Lake Michigan is
expected to shift westward over the southeast WI shoreline
overnight as winds veer to the south. Moisture does not appear to
be deep or cold enough to reach the snow growth zone, but if that
changes, we can't rule out a few snowflakes or drizzle from these
Clouds will increase from the southwest Friday night. In addition,
lake effect clouds should move onshore late in the night. This
will keep min temps from falling into the teens- lows will be in
the lower to mid 20s, except upper 20s near the lake. Saturday
highs will be in the mid to upper 40s.
Saturday night through Sunday night... forecast confidence is
A mid level trough will slide from the northern plains to the
upper Great Lakes. The period of strongest warm air advection and
vorticity advection will be during the day Sunday. Dry air in the
low levels will probably delay the precip later than what is in
our forecast Saturday night, so more likely it will begin Sunday
morning, spreading in from west to east.
Moisture looks deep enough for snow at the onset of the precip,
but then it dries out from the top down as the trough passes over
southern WI Sunday afternoon and evening. This means we will
probably lose the ice crystals and shift into drizzle or freezing
drizzle. Since it's Sunday afternoon with relatively mild air
temperatures, we should see mainly drizzle. If the trough lingers
longer and temps start to drop below freezing, we could see a
period of freezing drizzle before precip ends Sunday night.
There is a large spread in qpf amounts for this event, with GFS
the highest. Precip type is a large uncertainty based on critical
surface temperatures and the depth/temp profile of the moist
Monday through Thursday... forecast confidence is medium.
There is a signal for the upper trough to stall over the Great
Lakes for the first half of next week. This would keep higher
cloud cover over southern WI. Max temperatures will continue to be
below seasonal normal, but are expected to reach values above
freezing each day. Minimum temps should be in the upper 20s.
The next weather maker is expected to arrive Thursday. This looks
like it will be mainly rain.
Marine...brisk wly winds will develop for tnt over Lake Michigan
especially the north half where gusts may approach gale force. The
higher wind speeds are in response to strong low pressure
developing near James Bay with its trailing cold front approaching
the Great Lakes. The cold front will pass from north to south
across Lake Michigan from early Fri am through late Fri am. The winds
will shift to nwly with the frontal passage but winds will also
weaken. A Small Craft Advisory likely will not be needed from
Sheboygan to Winthrop Harbor but a few wind gusts may approach 22
kts or greater during the night.