Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 161759 AAB
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1159 AM CST Sat Dec 16 2017

.UPDATE...

There looks to be patchy freezing fog across areas away from Lake
Michigan later tonight into the middle morning hours Sunday. Low
stratus clouds under inversion should help trap moisture, with
rather light easterly winds inland. Closer to the lake, the winds
will be a little stronger, and should limit any freezing fog
potential there.

The freezing fog may cause slippery spots on roads later tonight
into Sunday morning, especially in low lying areas. Not confident
enough for a Freezing Fog Advisory at this time, but will need to
be watched by later shifts.

Wood

&&

.AVIATION(18Z TAFS)...

Main concern is potential for light freezing fog on runways later
tonight into the middle morning hours Sunday away from the lake.
Patchy freezing fog is anticipated, which may cause slick spots on
runways. Visibility values should generally be in the 3 to 6 mile
range in this area.

Area of IFR stratus clouds should gradually shift southward this
afternoon and early this evening. These clouds should then hang
around later tonight into Sunday, remaining in the 500 to 800 foot
range.

Light and variable winds in southern portions of the area will
become easterly this evening. Winds will remain easterly elsewhere
this afternoon. The easterly winds linger tonight into Sunday
morning, becoming light as low pressure moves northeast into the
area Sunday afternoon.

Wood

&&

.PREV DISCUSSION... (Issued 1002 AM CST Sat Dec 16 2017)

UPDATE...

The low stratus deck should remain over the northern portions of
the area this afternoon, before gradually spreading southward
tonight. This is mainly north of a stalled frontal boundary, which
will slide southward tonight.

Areas south of the front should see partly to mostly sunny skies
into this afternoon. This should allow for highs to warm into the
upper 30s to lower 40s. Areas in the low cloud deck should remain
in the upper 20s to lower/mid 30s for highs this afternoon.

There is some potential for freezing fog or drizzle overnight into
early Sunday morning. Still evaluating this potential, as it may
remain more of a low stratus deck during this period. There could
be some slick spots on roads if the freezing fog or drizzle
occurs.

Wood

MARINE...

Easterly winds of 10 to 20 knots north of the stalled front will
linger this afternoon, mainly north of Wind Point. This should
bring increasing waves into the 2 to 4 foot range this afternoon.
These easterly winds will then develop south of Wind Point this
evening and linger overnight. Thus, the waves will increase to 2
to 4 feet in this area as well. No Small Craft Advisory is
anticipated at this time into tonight, as most gusts should
remain around 20 knots, with waves at or below 4 feet.

Wood

PREV DISCUSSION... (Issued 526 AM CST Sat Dec 16 2017)

UPDATE...

Light snow showers are beginning to taper off across the far
northeastern corner of the CWA. This trend will continue, with
precip ending by mid morning at the latest.

AVIATION(12Z TAFS)...

Light easterly winds are expected today and tonight across the
area. Ceilings will initially be VFR this morning, but will lower
as the day goes on as moisture increases. MVFR is expected by
afternoon or evening, then IFR is expected overnight for most
locations.

PREV DISCUSSION... (Issued 205 AM CST Sat Dec 16 2017)

DISCUSSION...

Early this Morning through Tonight...Forecast Confidence is
Medium to High...

A band of light snow continues across the northeastern corner of
the forecast area early this morning. This snow remains very
light, with just minor additional accumulations expected through
sunrise.

As the precipitation ends this morning, a very brief period of
freezing drizzle is possible, at least in pockets across the Fond
du Lac and Sheboygan areas as cloud ice begins to dissipate.
Right now, it doesn`t look like any freezing drizzle would be
widespread enough to cause significant impacts, but it`ll be
something to keep an eye on this morning.

A few peeks of sun will be possible in counties adjacent to the
Illinois state line today, but everywhere to the north will remain
cloudy. Temperatures will reflect the range in sunshine, with
readings near 40 along the state line, to just the low to mid 30s
across the Highway 23 corridor.

Skies will remain overcast tonight, with temperatures falling back
into the 20s area-wide.

Sunday and Sunday night - Confidence...Medium
Broad mid level wave passes to our south. Surface low proggd to
near or into srn WI midday into the afternoon. Another mild day
though cloud cover expected to be stubborn. Models trending precip
to our south and blended guidance just clips our far southeast.
Surface trough passes with nearly neutral or even positive thermal
advection. Any clearing Sunday night could set up a fog scenario
though LLVL moisture for now is keeping the stratus in check with
progd MOS surface vsbys not reflective of fog at this time.

Monday through Tuesday night - Confidence...Medium
Mild west/southwest flow will maintain mild conditions into at
least early Tuesday. A cold front will pass Monday night though
and start to pull in some cooler air as Tuesday wears along. The
GFS collapses the 925 thermal pattern a bit more quickly during
the day than the ECMWF. It will be on the brisk side as well with
a tight gradient in the wake of the cold front. High pressure
along with a chillier airmass takes hold for Tuesday night with
high pressure nudging closer.

Wednesday - Confidence...Medium
The high and cold airmass lingers into early before a developing
WAA regime takes hold. The progs are showing the bulk of this lift
would be focused across northern/central WI though our northern
CWA could end up being on the southern fringe. So may have to
consider some pops as we draw closer but for now blended guidance
is keeping this north of our area so will leave it dry for now.

Thursday and Friday - Confidence...Medium
Progs continue to show an unsettled period with surface/850 low
to our west on Thursday morning and then slowly shifting east
along a rather tight baroclinic zone. Influence of a milder
airmass out ahead of the low at least into the morning. Colder air
starts to arrive Thursday afternoon with cold advection
continuing into Friday in blustery fashion. The ECMWF and GEM have
a more interesting surface low evolution and more favorable track
for decent snows than does the GFS. Pops are on the high side and
best consensus on the window for steadiest/heaviest snowfall
being Thursday night. The northern and western CWA could end up
seeing a longer period of snow being in the colder airmass
longest. Potential there for several inches of accumulation CWA
wide from this system.

MARINE...Easterly flow will continue across the nearshore waters
today and tonight. Waves will approach Small Craft Advisory levels
(4 ft) at times, but right now are expected to remain just below
at 2-3 ft.

Winds will become easterly again Sunday night, with waves
decreasing in response.

&&

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

$$

Update...Wood
Today/Tonight and Aviation/Marine...Boxell
Sunday THROUGH Friday...Collar


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