Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 152345
AFDMKX

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

.UPDATE...

No changes to headlines or snow totals at this time.

Widespread area of snow continues across the forecast area early
this evening. Along and near Lake Michigan, the lake
effect/enhanced band continues to pivot onshore, and should sweep
south across the eastern third or so of the forecast area this
evening. Expect quick drops in visibility and an additional inch
to perhaps two inches of snow as that band rotates through. Light
snow will continue ahead of and behind the heavier band into
tonight.

Further west, a few pockets of enhanced snow have developed from
just west of Janesville to the Madison area. Brief drops in
visibility can be expected here as well, along with another inch
or so of snow.

The widespread snow should slowly dissipate after midnight as the
upper level trough starts to pull east. Attention will then turn
to continued lake effect potential into at least the first half of
the day on Tuesday, as north-northeast winds continue across the
lake. Short term model guidance brings several bands of lake
effect snow south across the lake, with the bands just brushing
against the shore. As tends to be the case with lake effect, a
5-10 mile difference east or west will make all the difference
between a snowy Tuesday morning or having the bands stay offshore.
We`ll continue to watch trends tonight.

.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.

&&

MARINE...

The small craft advisory will continue north of Port Washington
until 6 pm this evening. Then we have a lull in winds and waves
tonight. But, increasing northeast winds will bring large waves
for a time on Tuesday with small craft advisory conditions likely
being met during the day. We`ll address that after the current one
expires.

A tight pressure gradient develops over Lake Michigan Wednesday
with low pressure over Canada and strong high pressure to the
south. The resultant south to southwest winds will likely reach
small craft advisory conditions Wed through Thu.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 6 AM CST Tuesday for WIZ059-065-
     066-071-072.

     Winter Weather Advisory until midnight CST tonight for WIZ046-
     047-051-056>058-062>064-067>070.

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

LM...Small Craft Advisory until 6 PM CST this evening for LMZ643.

&&

$$

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



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