Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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841
FXUS63 KMKX 222311
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
611 PM CDT Fri Sep 22 2017

.SHORT TERM...

Tonight And Saturday...Forecast Confidence Is High.

The 500 mb anticyclone will remain over the southern Great Lakes
into the Ohio River Valley during this period. High pressure will
linger east of the area at the surface. This will continue to
bring very warm and humid conditions tonight into Saturday. Lows
tonight will only fall into the middle to upper 60s.

Given the expected 925 mb temperatures, Saturday`s highs should
be in the upper 80s to lower 90s in most areas. Temperatures will
turn cooler near Lake Michigan in the late morning and afternoon,
with a south to southeast lake breeze. Heat index values Saturday
should be in the lower to middle 90s.

Saturday night and Sunday...Forecast confidence...High

The upper ridge extends from Texas to the Great Lakes with a large
trough across the northern and central Rockies. The 700/850 mb
ridge is across the Great Lakes with the 850 mb jet mainly west
across Iowa and into Minnesota.

A surface high will remain centered over the Great Lakes, putting
southern Wisconsin in light southerly flow. The atmosphere looks
rather dry with a shallow layer of moisture above the low level
steep lapse rates up to 840 mb. This may be enough for a few fair
weather cumulus. All this will result in temperatures remaining
at near record values across most of the forecast area.

Expect a lake breeze to develop but not reach too far inland.
Additionally, dewpoints in the upper 60s may set us up for at
least patchy fog along Lake Michigan.

Sunday night and Monday...Forecast confidence...High

The upper ridge pushes off to the east as the large trough across
the northern and central Rockies moves a little toward the east.
The 700/850 mb ridge is across the eastern Great Lakes with the
850 mb flow across much of southern Wisconsin.

A surface high over the Great Lakes weakens, with southern
Wisconsin still in the in light southerly flow. The atmosphere
still looks rather dry, except for increasing moisture between
700 and 850 mb. The GFS is faster in bringing showers and
thunderstorms into south central Wisconsin, with the ECMWF slower
and still dry.

Expect a lake breeze to develop but not reach too far inland.


.LONG TERM...


Tuesday through Friday...Forecast confidence is medium:

Guidance continues to show an upper shortwave moving into the
Upper Mississippi Valley region Tuesday, with the upper trough
re-establishing itself over the Upper Mississippi Valley or Great
Lakes by Friday.

Both the GFS and ECMWF swing a band of showers and thunderstorms
with a cold front Tuesday, with cooler air (near normal) Thursday
and Friday.

&&

.AVIATION(18Z TAFS)...

VFR conditions are expected tonight and Saturday across the area.
south to southeast lake breeze will continue to push inland until
early this evening. South winds are expected elsewhere into early
this evening, with some gusts up to 20 knots around and west of
Madison.

South winds will become light tonight and linger on Saturday.
Another southeast lake breeze is expected to develop a bit quicker
than today, moving inland by the late morning hours and lingering
into the afternoon. Some ground fog is possible in low lying
areas overnight. Some diurnal cumulus clouds may develop in the
afternoon as well.

&&

.MARINE...

South to southeast lake breeze of 10 to 15 knots will linger
until early this evening, and again late Saturday morning and
afternoon. Waves of 1 to 2 feet are generally expected, highest
toward the Sheboygan area. There may be some light fog during the
overnight hours tonight and Saturday night.

&&

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

$$

Tonight/Saturday and Aviation/Marine...Wood
Saturday Night through Friday...Hentz



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