Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 180352
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1052 PM CDT Thu Aug 17 2017

.AVIATION(06Z TAFS)...

The clouds wrapping around the strong low pressure system pulling
away from the region are a mix of MVFR and VFR CIGS across
southern Wisconsin. They may settle to MVFR later tonight with
skies clearing by around sunrise. Look for the westerly winds to
remain somewhat elevated overnight, increasing for a time during
the morning. The winds will diminish Friday afternoon.

&&

.PREV DISCUSSION... (Issued 845 PM CDT Thu Aug 17 2017)

UPDATE...
We have some lingering showers around the area as a spoke of
vorticity rotates around the bottom the upper low center. Very
isolate stuff and should be gone by around midnight. Otherwise,
continued cloudy with elevated west to northwest winds overnight.
Temperature forecast is on track.

MARINE...
Strong low pressure will continue to lift northeast toward the
eastern basin of Lake Superior overnight. Look for the west to
northwest winds to remain elevated overnight and into early Friday
afternoon. A small craft advisory remains in effect through 1 pm
Friday.

PREV DISCUSSION... (Issued 542 PM CDT Thu Aug 17 2017)

AVIATION(00Z TAFS)...
The clouds wrapping around a large low pressure system lifting
northeast from the U.P. of Michigan will bring a mix of VFR and
MVFR CIGS through the evening. The bulk of the MVFR CIGS will
remain north of Milwaukee and Madison, but all areas should
gradually improve to VFR by mid morning on Friday. Any lingering
showers will end with sunset and the loss of heating. Westerly
winds will remain elevated overnight, gradually relaxing from west
to east later tonight as the low pulls away.

PREV DISCUSSION... (Issued 222 PM CDT Thu Aug 17 2017)

SHORT TERM...

Tonight and Friday...Forecast Confidence is high.

An occluding low pressure system will track from northern
Wisconsin towards Lake Superior tonight. Any showers due to
instability within the cyclonic regime should quickly end around
sunset. Otherwise, look for mostly cloudy skies tonight. Windy
conditions will continue due to the strong pressure gradient
associated with the departing low. Gusts to around 30 mph are
possible this evening, with gusts decreasing somewhat later
tonight. The winds will remain quite gusty along Lake Michigan
overnight.

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 by afternoon, but any
rain chances appear to hold back to our west through early
evening.

Friday night and Saturday...Forecast confidence is high.

The upper trough continues to sharpen across Wisconsin Friday
night before reaching the Great Lakes region Saturday. The
strongest upper level divergence occurs across northern illinois
Friday evening, but moderate 700 mb upward motion does affect far
southern Wisconsin until around midnight. The 850 mb
west/southwest wind max remains to the south more towards central
Illinois. The NAM has precipitation mainly to the south of
Wisconsin, while the GFS and, to a lesser extent ECMWF does bring
in some rain. GFS zero to 1 km CAPE is around 200 Joules/kg, but
does have some steeper lapse rates in the 700 to 500 mb layer.

Mid and lower layers then dry, with just enough moisture around
850 mb to bring a few fair weather cumulus Saturday afternoon.

LONG TERM...

Saturday night through Sunday... Forecast confidence is high.

The northwest flow becomes more zonal.

Surface high pressure will move across the Great lakes with some
weak warm air advection beginning Sunday.

Monday through Thursday... Forecast confidence is medium.

A shortwave will push across the plains Monday and into Wisconsin
Monday night and Tuesday.

A surface trough will be near southern Wisconsin later Monday and
Tuesday. The ECMWF is slower in bringing precipitation, holding
off until Monday night, while the GFS is faster with showers and
thunderstorms beginning Monday. This system would bring clouds
which will affect viewing the eclipse in southern WI on Monday.
Stay tuned.

Conditions will remain favorable for showers and scattered storms
through Tuesday evening until a cold front drops south. There
could be some severe storms ahead of the front.

High pressure and cooler air will then dominate on Thursday.

AVIATION(18Z TAFS)...

Mixture of VFR/MVFR CIGS should continue into tonight. A few lower
CIGS are possible, especially north of MKE and MSN. Scattered
showers should taper off around sunset. Gusty SW winds will veer
westerly tonight, with gusts to around 25 knots at times. Low
level wind shear is possible from this evening into early tonight,
and included this in the TAFs. Ceilings should rise to VFR levels
by early tomorrow afternoon, with gusty W to NW winds developing.

MARINE...

Small Craft Advisory conditions are expected for the nearshore
waters through early Friday afternoon. Gusty southwest winds this
afternoon will veer westerly tonight, with frequent gusts to 25
knots expected through early Friday afternoon. Mariners should
exercise caution.

BEACHES...

A Beach Hazards statement remains in effect for Sheboygan County
through this evening. Winds are now turning more offshore, which
should push the highest waves towards the open waters. Hazardous
swimming conditions should persist until the waves heights decline
later this afternoon.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 1 PM CDT Friday for LMZ643>646.

&&

$$

Update...Davis
Tonight/Friday and Aviation/Marine...SPM
Friday Night through Thursday...Hentz


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