Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 180344
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
944 PM CST Wed Jan 17 2018

.UPDATE...

We`re still seeing a few decent wind gusts along the southern
Lakeshore counties owing to good low-level mixing and downward
momentum transport from a 50 knot low-level jet. As such, some
additional drifting of snow is still possible in the short-term.
Based on upstream obs these higher gusts seem to be transient in
nature, so feel that they should ease off in the coming hour or
so. We`ll remain well mixed overnight, so gusts of 20 to 25 mph
are still expected overnight. Snow covered and slick stretches of
roadways (especially rural and secondary ones) will remain the
primary hazard overnight into tomorrow morning. Motorists should
exercise caution.

As a result of the better mixing, temperatures have been slower to
fall than previously anticipated, so nudged both hourly and low
temperatures up just a tad.

&&

.MARINE...

A few gale force gusts are possible in the nearshore waters over
the next hour or so, with gusts of 25 to 30 knots continuing
overnight. A Small Craft Advisory continues into Thursday
afternoon.

&&

.PREV DISCUSSION... (Issued 536 PM CST Wed Jan 17 2018)

UPDATE...

Gusty west-southwest winds have produced minor visibility
restrictions and slick spots on area roadways with temperatures
remaining well below freezing. Sheboygan County officials indicate
that blowing/drifting snow has produced slick areas on roadways
there, so will hold on to the Winter Weather Advisory for impacts
in that area. Elsewhere, caution is advised for slippery spots on
roads and walks tonight.

Breezy conditions will continue overnight owing to the tight
pressure gradient, as southern Wisconsin remains between low
pressure over southern Canada and strong high pressure located
over the southern Mississippi valley. With elevated mixing in the
surface layer, low temperatures should be several degrees warmer
than were observed last night. Will be watching trends, however,
and making adjustments as needed.

AVIATION(00Z TAFS)...

VFR through the TAF period with patchy blowing snow this evening.
Winds will remain elevated overnight, with low-level wind shear
occurring.

PREV DISCUSSION... (Issued 250 PM CDT WED JAN 17 2018)

TONIGHT and THURSDAY...Forecast Confidence - Medium to High.

Strongest winds expected next several hours, with gusts of 25 to 30
mph, potentially reaching 35 mph in the Sheboygan area.  No problems
reported by law enforcement yet due to blowing and drifting snow.
Expect some drop in gustiness with loss of insolation this evening,
however strongest low level winds will be moving across southern WI
at this time.  Winds of 30 to 40 knots will be just off the surface
around 1k feet so potential for gustiness to continue at least
through the evening.

Otherwise, a quiet period expected as northerly steering winds back
to the northwest. This will allow milder air to advance into
southern WI during the period.  Strong, compact mid-level short wave
over southern Canada will track east southeast across the Lake
Superior/UP area on Thursday.  This will carry a period of mid-high
level cloudiness across the area on Thursday.  Low levels remain
parched so no precipitation is expected.  925H temps warm to around
zero on Thursday.  Expect temps to warm to the lower 30s, tempered
by the fresh widespread snow field.  Also, breezy southwest winds
will add an additional chill to the air.

THURSDAY NIGHT THROUGH SATURDAY - Forecast Confidence...Medium to
High.

Quiet conditions to continue through this period as upper level
winds continue to back and become more zonal, ahead of short wave
trof pushing into the southwest CONUS.  This zonal flow will allow
milder air in the low levels to settle over the western Great Lakes.
925H temps will be in the zero to 5C above range both Friday and
Saturday. Little low level moisture but passing high level clouds
expected at times. Fresh snow will continue to retard temps but with
night time low level mixing keeping temps a bit warmer, daytime
temps should climb above freezing resulting in some settling/melting
of widespread snow cover. Mixing should also prevent significant fog
development at night.  Will need to watch for slick spots developing
at night from melting snow.

EXTENDED PERIOD...

SATURDAY NIGHT THROUGH WEDNESDAY - Forecast Confidence...Medium.

Main focus of this period will be deepening plains low pressure that
looks likely to track northeast into southern/central WI Sunday
night and Monday.  Increasing southerly winds ahead of the
strengthening low will allow deeper low to mid level moisture to
stream northward into the region. Last several runs of the GFS and
ECMWF showing some waffeling of track of low pressure Sunday night
and Monday, however GFS ensembles in good agreement on the surface
low pressure tracking across southern WI on Monday.

Still looks like warmer air will sweep into southern WI ahead of
this system resulting in mostly a liquid precipitation type Sunday
into Monday, possibly beginning as a mix Saturday night. Pavement
temperatures will be a concern at the onset but should warm above
freezing quickly. Northwest and far western CWA will be more on the
edge of colder low level temps and may receive more of a rain/snow
mix. Wedge of drier air wrapping into circulation may end
precipitation for a time on Monday before colder air and light snow
spreads into the area Monday night into Tuesday.  Colder air will
return for mid-week, with a potential period of accumulating snow
and rain/snow mix late in the week.

AVIATION(21Z TAFS)...

VFR conditions to continue with patchy blowing snow next few hours.
Core of strong low level winds will cause low level wind shear
across the area for a time overnight.

MARINE...

Small Craft Advisory continues into Thursday afternoon.  Will need
to watch gusts closely north of Port Washington this evening as
potential for a few gusts to 35 knots.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 3 PM CST Thursday for LMZ643>646.

&&

$$

Update...SPM
Tonight/Thursday and Aviation/Marine...MBK
Thursday Night through Wednesday...MBK



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