Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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780
FXUS63 KMKX 171640
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1140 AM CDT Thu Aug 17 2017

.UPDATE...

An occluding low pressure system will track from northwest
Wisconsin towards Lake Superior by this evening. A surface cold
front was progressing through eastern portions of our area, with a
few showers out ahead of it. Dewpoints will gradually drop behind
the front this afternoon, but there will still be enough moisture
and instability within the cyclonic regime to continue shower
chances through the afternoon. A rumble of thunder is possible as
well. Gusty southwest winds will veer to westerly by this evening.

Look for cloudy skies tonight, with a slight chance for a shower.
Otherwise, windy conditions are expected due to strong pressure
rises resulting from the deep layer cyclone departing to our
northeast. Wind gusts of 30 to 35 mph are possible this evening,
with gusts decreasing somewhat through the night. The winds will
remain more elevated near Lake Michigan through the late night
hours.

We`ll see a bit more sunshine on Friday as low pressure pulls
away. Winds will become gusty during the day as the mixed layer
deepens and a lingering pressure gradient remains. A shortwave
trough and weak surface low will approach during the afternoon,
but any rain chances appear to hold back to our west through early
evening.

&&

.MARINE...

Small Craft conditions are expected for the nearshore waters
through early Friday afternoon. Gusty southwest winds this morning
will veer westerly tonight, with frequent gusts to 25 knots
expected through early Friday afternoon. Initially high waves
north of Port Washington should shift more towards the open waters
later today as the winds turn more offshore. Mariners should
exercise caution.

.BEACHES...

A Beach Hazards statement remains in effect for Sheboygan County
through this evening. There is still enough onshore component this
morning for high waves near the shore, but as winds shift later
this afternoon the highest waves will be pushed more towards the
open waters. The high swim risk for Sheboygan County means that
swimming is not advised.

&&

.PREV DISCUSSION... (Issued 629 AM CDT Thu Aug 17 2017)

UPDATE...

AVIATION(12Z TAFS)...

Low ceilings early this morning are expected to rise to around
2000 feet above ground level in south central Wisconsin by middle
to late morning. VFR category ceilings above 3000 feet are
forecast in southeast Wisconsin by middle to late morning. MVFR
ceilings between 1000 and 2000 feet should gradually spread
across northern portions of the area during the afternoon into
tonight.

Scattered showers and isolated thunderstorms may affect far
eastern portions of the area for the next few hours. More of this
activity should develop later this morning into this afternoon.
Showers should taper off from southwest to northeast tonight. May
see briefly reduced visibility values and brief heavy rainfall
with any heavier showers or storms.

Gusty southwest winds are expected to develop by middle to late
morning, lingering into the afternoon. These winds will veer to
the west tonight. Gusts up to around 25 knots are expected at
times.

May see low level wind shear conditions develop this evening into
the overnight hours, with west northwest winds around 30 knots at
2000 feet above ground level. For now, left mention out of TAFs,
due to low confidence of these winds reaching 40 knots at 2000
feet.

PREV DISCUSSION... (Issued 351 AM CDT Thu Aug 17 2017)

SHORT TERM...

TODAY AND TONIGHT...Forecast Confidence Is Medium.

Models are in decent agreement with main 500 mb low shifting
northeastward across northern Wisconsin into the Upper Peninsula
of Michigan today. It then continues further to the northeast
tonight. One area of showers and a few thunderstorms should
continue to slide northeastward across the area early this
morning. This is in association with the low level jet nose
pointing into the area.

Mainly scattered showers and isolated thunderstorms are then
forecast for the rest of today, with differential cyclonic
vorticity advection with the passing 500 mb low. The showers
should gradually taper off tonight from southwest to northeast
across the area, as the 500 mb low moves away.

Humid conditions are expected today, until cold front pushes
through the area later this afternoon. Dry slot with 500 mb low
may try to bring in partial sunshine in the eastern portions of
the area for at time today. However, kept forecast mostly cloudy
given close proximity of 500 mb low and associated cloud shield.

Highs should not be much higher than current values in south
central Wisconsin. Highs may reach the upper 70s in southeast
Wisconsin, where warm sector airmass will reside the longest.
Pressure gradient will become tight today and tonight, along with
some low level mixing, allowing for gusty southwest winds today.
These winds will veer west tonight.

LONG TERM...

Friday and Friday night... Forecast confidence is medium.

The surface low over northern Michigan will continue to shift
east through the day. The lingering strong pressure gradient and
steep low level lapse rates will lead to gusty west winds through
midday, then diminishing winds in the afternoon.

A shortwave trough will track through the area Friday night and
bring a chance for scattered showers and storms to southern WI and
northern IL. Moisture is questionable with this system.

Saturday through Sunday... Forecast confidence is high.

The upper trough should be east of southeast WI by Saturday
morning, so expecting a dry weekend with light winds and
increasing temps and humidity

Monday through Wednesday... Forecast confidence is medium.

A front will slowly sag southeast through WI Monday and Tuesday.
The ECMWF is faster with clearing southern WI than other models.It
looks like showers and storms should hold off until the
afternoon here. As long as there are not excessive clouds from
storms that would be over MN, IA or northern WI, there is hope for
a view of the eclipse in southern WI on Monday. Stay tuned.

Conditions will remain favorable for scattered storms through
Tuesday evening until that front gets south of the IL border.
There could be some severe storms ahead of this front.

AVIATION(09Z TAFS)...

Low ceilings early this morning are expected to rise to around
2000 feet above ground level in south central Wisconsin by middle
to late morning. VFR category ceilings above 3000 feet are
forecast in southeast Wisconsin by middle to late morning. MVFR
ceilings between 1000 and 2000 feet should gradually spread
across most of the area during the afternoon into tonight.

Area of showers and isolated thunderstorms should spread northeast
across the area early this morning, with more scattered showers
and isolated storms later this morning into this afternoon.
Showers should taper off from southwest to northeast tonight. May
see briefly reduced visibility values and brief heavy rainfall
with any heavier showers or storms.

Gusty southwest winds are expected to develop by middle to late
morning, lingering into the afternoon. These winds will veer to
the west tonight. Gusts up to around 25 knots are expected at
times. May see low level wind shear conditions develop this
evening into the overnight hours, with west northwest winds
around 30 to 35 knots at 2000 feet above ground level.

MARINE...

Small Craft Advisory is in effect north of Port Washington, and
will go into effect at 18Z today south of there. High waves of 3
to 5 feet are expected to linger north of Port Washington into
this morning, before winds shift offshore and push the high waves
further into the open waters.

Tightening pressure gradient will allow for gusty southwest winds
by midday, and will veer west tonight. Frequent gusts to 25 knots
are expected to linger into Friday morning. Thus, the Small Craft
Advisory was extended until 18Z Friday. Highest waves will remain
over the open waters of Lake Michigan.

BEACHES...

A Beach Hazards Statement is in effect for the beaches along Lake
Michigan in Sheboygan County until 02Z tonight. High waves are
expected to continue into this morning, before being pushed
further into the open waters by midday. This will bring a high
swim risk.

There are gusty southwest winds expected by midday, lingering
into this afternoon and veering west tonight. High waves will be
over the open waters, so the Beach Hazards Statement may not be
needed for the afternoon and early evening.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement until 9 PM CDT this evening for WIZ052.

LM...Small Craft Advisory until 1 PM CDT Friday for LMZ644>646.

     Small Craft Advisory until 1 PM CDT Friday for LMZ643.

&&

$$

Update...SPM
Today/Tonight and Aviation/Marine...Wood
Friday THROUGH Wednesday...Cronce



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