Gale Watch 5, NWS Milwaukee, WI

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
234 PM CST Mon Jan 13 2020

.DISCUSSION...

Tonight through Tuesday Night...Forecast Confidence is Medium...

Similar setup to last night with a shortwave moving out of CO and
lifting E/NE into the Great Lakes. The upper level jet passes
to the south, putting us in the left exit region once again.
However, this go around the better vorticity advection will be
displaced to the north. In addition to that, the surface low is
expected to track through north-central MN and into northern WI
early Tuesday morning, which is a bit further north than with the
system last night.

The 12z sounding from DVN showed dry conditions above 850mb but as
the system evolves today expect moisture to move back in aloft.
There is some question in model profiles on whether we'll get
enough ice in the cloud for all things to stay all snow tonight.
Think with the system displaced more to the north we end up on the
fringe where we could see a bit of snow and freezing drizzle. Made
some adjustments to reflect this possibility and this would put in
a very light glaze of ice with any freezing drizzle that does
occur. Snow amounts across the area may not make it much above
half an inch with only a trace possible in the far SE. A few slick
spots on any untreated surfaces are possible early Tuesday
morning.

Based on how the past few days have gone and models being too
quick to clear clouds out, have adjusted sky grids to hold onto
clouds for much of Tuesday. It may not be until closer to the
late afternoon hours as winds shift more to the NW that we
actually see clouds begin to clear. This will impact highs and
have kept temps a bit cooler with values holding in the mid 30s
for much of the area. With partly cloudy skies and a cooler N/NW
flow Tuesday night into Wednesday expect temps to fall into the
teens for lows.

Wednesday - Confidence...Medium
A mid level shortwave will arrive and be accompanied by a
surface/850 millibar low. the ECMWF shows a more pronounced thermal
ridge into the area while the GFS suppresses the thermal field and
keeps things cold enough for snow. Bufkit soundings show some hints
of ice loss in the dendritic growth zone but confidence not high
this will be sustained so will likely keep things as snow for now
but should this trend continue may need to add some freezing drizzle
or freezing rain in for the morning. Models have come into a little
better agreement on qpf, though the NAM still showing a drier look.
This should have a little more moisture than the prior system from
Monday night, so think a couple inches, perhaps up to 3 in the
northern counties closer to 850 low.

Thursday - Confidence...Medium
Cold surface high should prevail this period. Has been a good deal
of consistency and consensus that this would be a quiet day with
the dry weather lasting into Thursday night as well.

Friday through Saturday - Confidence...Low to Medium
The models are still showing a potentially prolific snow maker towards
the end of the week. A warm and moist flow increases on Friday with
an expansion of snow across the area as the day wears on. Some hint
that a mix could work into the south Friday night however the ECMWF
is colder and suggesting all snow. A currently proggd southern track
of the low (south of WI) combined with qpf and thermal fields suggests
this type of system has the potential to produce several inches of
snow.

Sunday through Monday - Confidence...Medium
Looks like a largely dry period with high pressure taking hold. The
00z GFS had shown a weak wave coming in Sunday night but this has been
dampened out with the 12z run, so will keep the pops quiet this period.

&&

.AVIATION(21Z TAFS)...MVFR cigs continue to hold for much of southern
WI. However, observations to the W/SW in IA show a lower cloud deck
moving towards the area. This is in response to a system that will
move across south-central MN and northern WI tonight into Tuesday.
IFR cigs will spread in later this evening, then as the system passes
to the NW of the region expect cigs to lower even further down to LIFR
with fog and light snow possible. Any accumulations will be less than
0.5 inches. There is now better agreement in guidance for freezing
drizzle to occur late tonight into Tuesday morning and the 21z amendment
will reflect this change. These conditions should continue until 12-14z
when cigs begin to improve to MVFR but the low stratus will hold for
much of the day.

&&

.MARINE...A system moving through western Lake Superior will bring an
increase in southerly winds late tonight through Tuesday. Gusts could
approach small craft conditions during the afternoon hours before
diminishing overnight Tuesday into Wednesday. A stronger system is
lined up to move across the southern portion of Lake Michigan on
Wednesday and this could bring a period of gusts that approach gale
force at times Wednesday night through Thursday.

Another strong system will impact the region Friday and Saturday
with gale force gusts possible at times.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

Tonight through Tuesday night/Aviation/Marine...Stumpf
Wednesday through Monday...Collar

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