Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 160525
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1125 PM CST Mon Jan 15 2018

.UPDATE...

No real changes to the overall forecast at this point. The final
remnants of the large lake enhanced snow area have pushed south
into Illinois, with just occasional lake effect showers moving
onshore. This should continue overnight, until the lake effect
becomes better organized and eventually forms a band of snow. This
band is expected to brush the shoreline tomorrow morning,
bringing a quick shot of additional snow where (if) it moves
onshore.

&&

.AVIATION(06Z TAFS)...

For MSN...Just a few light snow showers will continue for a few
more hours, before snow dissipates overnight. Expect an
improvement to VFR after sunrise. Winds should remain northwest.

For KMKE, KEUS, and KENW...Things are a bit more complicated for
the terminals near the lake, as lake effect snow showers will
continue through the overnight hours. Initial showery activity
should eventually become better organized into a band of lake
effect snow by daybreak, which is currently expected to brush the
shoreline area. Variable flight conditions are likely overnight,
with vis coming in and out of IFR as snow showers pass through.
Once the more organized band forms, all will depend on where
exactly the band tracks. If it tracks over any terminals, IFR
conditions with light to moderate snow will be likely. Otherwise,
MVFR would be expected to improve to VFR with time. Updates are
likely overnight as the track of the lake effect snow band becomes
more clear.

&&

.PREV DISCUSSION... (Issued 911 PM CST Mon Jan 15 2018)

UPDATE...

Area of moderate snow continues to pivot counterclockwise across
the southeastern portion of the forecast area. Have increased snow
totals a bit for this area based on reports, with a general 1-2
inches of new snow for the 6 PM to Midnight time period.

We continue to watch lake effect snow showers take shape upstream,
with confidence growing that at least some impacts will be
realized for the lakeshore area into tomorrow morning. As a
result, we`ve gone ahead and extended the Winter Weather Advisory
for the lakeshore area until 18Z/noon Tuesday, which now matches
up with the expiration time for the Winter Storm Warning for
Ozaukee and Sheboygan Counties. Nearly all available model
guidance points toward lake effect snow bands forming...the only
question will be if they move onshore or stay out over the lake,
and if so, how much snow will be generated. For now, have an
additional 1-2 inches of snow right along the lakeshore, with
lesser amounts further to the west. As is the case with lake
effect, any movement of just a few miles east or west will have a
drastic impact on eventual snow totals. Interests across the
I-94/I-43 corridor should certainly keep up with updates to the
forecast overnight and early Tuesday morning.

MARINE...

Small Craft Advisory is in effect from 6 AM to 3 PM Tuesday for
areas north of North Point Light for higher waves. Expect 3 to 5
ft waves associated with north-northeast winds. Waves will be
highest near open waters.

Expect northerly winds to persist through Tuesday, before they
become westerly and then southwesterly by Wednesday. Another Small
Craft Advisory will likely be required by this time.

AVIATION(00Z TAFS)...

A few bands of heavier snow will affect the various TAF sites this
evening, with a lake enhanced band moving into and through the
KUES, KMKE, and KENW terminals. Further west, a few pockets of
enhanced snowfall are affecting KMSN, and these should persist
for another couple of hours before dissipating. Across all
terminals, expect visibility to fall to between 1/2 and 1 mile as
the heavier snow moves through.

Snow should end for the Madison area later tonight, but will
likely persist in some form for the terminals closer to Lake
Michigan into Tuesday morning. One or more areas of lake effect
snow are expected to form later tonight, and ride along the
lakeshore into the morning hours tomorrow. The exact position of
this band will be tricky to forecast ahead of time, leading to
lower confidence in snow potential and impacts late tonight and
tomorrow morning. For now carried -SHSN and/or VCSH tomorrow
morning, but it`s possible that impacts may be more widespread
than currently indicated.

PREV DISCUSSION... (Issued 217 PM CST Mon Jan 15 2018)

SHORT TERM...

Tonight and Tuesday...Forecast confidence is high.

The lake effect snow band that has mainly impacted Sheboygan and
Ozaukee county this afternoon, will gradually pivot to an
east/west orientation and become part of the surface low
convergence axis as it drifts south this evening...reaching
Kenosha by around midnight. Although the southeast has gotten into
a period of subsidence that diminished/ended the snow for a time,
it will pick up again as that band approaches. The trough axis
will stretch west across the forecast area, under a deep cyclonic
flow, so much of southern Wisconsin will stay in the light snow
into the evening. Will keep the advisory going due to the ongoing
snow and slippery secondary/tertiary roads that will likely get
worse with sunset. The surface low and upper trough axis move
south of the area by/after midnight. At that point, we should see
northeast winds bring continued lake effect snow showers to the
lakeshore counties into Tuesday morning. The snow will taper off
inland at that point.

Eventually, winds will turn off shore, taking the showers east by
Tuesday afternoon.

LONG TERM...

Tuesday night through Thursday... Forecast confidence is high.

High pressure will drift through the Plains tomorrow night and
into southeast U.S. on Thursday. Meanwhile, a shortwave trough
crossing the Upper Midwest and western Great Lakes Wed night into
Thu will create a tight surface pressure gradient over southern
WI. We can expect some breezy southwest winds on Thursday. This
will help temperatures rise into the lower 30s.

Friday and Saturday... Forecast confidence is high.

An upper trough approaching from the Northern Plains will bring
another period of breezy southwest winds to southern WI on Friday.
Look for temperatures to warm into the upper 30s and lower 40s Fri
& Sat.

Sunday through Monday... Forecast confidence is low.

That upper trough is expected to become amplified as it phases
with the southern stream. This will bring a well-organized surface
low with plenty of moisture through the Midwest early next week.
There is still a lot of uncertainty with the low track this far
out. The ECMWF and Canadian models have the low tracking through
southern WI which gets us into the warm sector (rain, storms
possible), while the GFS tracks it through central IL which keeps
us in the snow and cold. High temperatures on Sunday could be
anywhere from 30 degrees to 55 degrees. Stay tuned.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until midnight CST tonight for WIZ046-
     047-051-056>058-062>064-067>070.

     Winter Weather Advisory until noon CST Tuesday for WIZ059-065-
     066-071-072.

     Winter Storm Warning until noon CST Tuesday for WIZ052-060.

LM...Small Craft Advisory from 6 AM to 3 PM CST Tuesday for LMZ643-
     644.

&&

$$

Update...Boxell
Tonight/Tuesday and Aviation/Marine...Boxell
Tuesday Night through Monday...99



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