Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 230224
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
924 PM CDT MON AUG 22 2016

.UPDATE...

Expect quiet conditions overnight as southern Wisconsin remains
along the eastern periphery of surface ridging. As the high slides
away to the east, the pressure gradient will tighten a bit
overnight in response to organizing low pressure over the Great
Plains. Mixing within the boundary layer should remain sufficient
to prevent fog formation in most areas with the possible exception
of the Wisconsin River valley. Low temperatures are on track to
reach the upper 50s, with lower 60s along the Lakeshore. No
appreciable clouds or rain chances are expected until Tuesday
night into Wednesday as a shortwave trough moves across the
region.

&&

.AVIATION/06Z TAFS/...

High pressure passing to our southeast will provide prevailing
VFR conditions into Tuesday. Southerly winds will increase Tuesday
in response to a tightening pressure gradient ahead of approaching
low pressure. Gusts of 15-20 kt are possible Tuesday afternoon.
Few to scattered diurnal cumulus around 4 kft should develop
around 17z Tuesday and persist through evening.

&&

.MARINE...

Increasing southerly winds are expected on Tuesday ahead of
approaching low pressure. Wind gusts should reach small craft
advisory levels north of Port Washington, with building waves to 3
to 5 feet. Hoisted a small craft advisory from Port Washington to
Sheboygan from late Tuesday morning through late Tuesday night for
wind and waves. Small craft should exercise caution in the
nearshore waters on Tuesday.

&&

.BEACHES...

A high swim risk exists for beaches in Sheboygan and Ozaukee
Counties tomorrow. Southerly winds of 10 to 20 mph should allow
building waves up to 5 feet, and promote the development of
dangerous currents, especially near Piers and Breakwalls. A beach
hazards statement may be necessary for these areas on Tuesday.

&&

.PREV DISCUSSION... /Issued 348 PM CDT MON AUG 22 2016/

TONIGHT AND TUESDAY...Forecast Confidence...High

Great summer weather will continue through Tuesday under the western
periphery of high pressure. Temps will be a little milder tonight
due to higher low level winds. The better mixing as a result of the
winds will limit fog to even less than last night...which was mainly
confined to river valleys.

There will likely be a few more clouds tomorrow than today as the
high pushes farther east, along with somewhat breezier winds. The
clouds shouldn`t disrupt heating much, so looks like a mild day
with seasonable highs in the low 80s.

TUESDAY NIGHT THROUGH WEDNESDAY...Forecast Confidence Medium

All models have a 500 mb vorticity maxima that lifts into western WI
by 12Z Wednesday ahead of the main short wave trough crossing far
southern Canada. While the strongest forcing with the associated low-
level jet stays just to the south on the nose of the stronger winds,
enough lower level frontogenetic response pushes into the region
with a good contribution to overall lift from the differential CVA
to keep likely PoPs in the western CWA late Tuesday night,
overspreading the forecast area Wednesday ahead of the surface cold
front.

Instability on forecast soundings varies according to the speed of
the cold front passing through the region with the slower GFS
allowing CAPE values approaching 2000 Joules/kg in the southeast
ahead of the front. However the faster NAM still allows CAPE
approaching 1000 J/kg with enough effective shear to support
persistent updrafts. Could not rule out an isolated storm producing
gusty winds but limiting factors will be overnight
clouds/pcpn/outflows that may reduce the amount of destabilization,
as well as surface temperatures. Precipitable water values rise to
around 2 inches, but meso-beta element speeds will lower flooding
potential.

Will linger pcpn chances into Wednesday night, though they may be
lowered or removed in later forecasts as the slower GFS is the only
model depicting widespread pcpn over the CWA after 00Z Thursday,
though the ECMWF does brush the extreme south with light QPF
overnight. Lingering cloud cover will hold overnight lows up in the
60s.

THURSDAY AND THURSDAY NIGHT...Forecast Confidence High

Surface high under confluent mid-level flow will bring dry weather
to the region. Coldest pocket of 925-850mb temperatures remain north
but a thermal trough does push into the region overnight. Highs
Thursday will be able to reach the mid to upper 70s to around 80 in
the far southeast, with lows falling into the low to mid 50s inland
with readings around 60 lakeside.

LONG TERM...

FRIDAY THROUGH MONDAY...Forecast Confidence
Medium.

After a quiet Friday with high temperatures in the mid 70s,
precipitation chances return late Friday night into Saturday with
warm advection ahead of approaching 500 mb trough. 12Z ECMWF dampens
this wave more than the GFS as it crosses the western Great Lakes
keeping the influence of the surface high over most of eastern WI
and shunting the bulk of the pcpn to the north. The GFS has stronger
short wave energy passing through the area Saturday night into
Sunday but may be overly strong from convective feedback. Both the
GFS and ECMWF bring a vigorous short wave trough though the area
Sunday night through Monday. This keeps chance PoPs in the forecast
through the rest of the extended. Looking for at or slightly above
normal temperatures from Saturday through Monday.

AVIATION/00Z TAFS/...

VFR conditions will prevail through Tuesday under the western
periphery of high pressure. The high tonight will be a bit farther
east than last night, with a tightening pressure gradient ahead of
approaching low pressure. Only had fog in the river valleys last
night and it might be a stretch to repeat that tonight given
increasing low level winds.

Will likely see diurnal VFR cumulus Tuesday along with increasing
high level clouds.

MARINE...

Southerly winds will increase a bit Tuesday ahead of approaching low
pressure, but should remain below small craft advisory levels. Winds
may gust to advisory criteria for a time Wednesday as the low moves
by to the north. The highest waves will be in the northern marine
zones, with waves greater than 4 feet possible mainly north of Port
Washington on Wednesday. This will definitely be a period to keep
an eye on for a possible advisory.

&&

.MKX Watches/Warnings/Advisories...
WI...None.
LM...SMALL CRAFT ADVISORY from 10 AM Tuesday to 3 AM CDT Wednesday
     for LMZ643.

&&

$$

UPDATE...SPM
TONIGHT/Tuesday AND AVIATION/MARINE...DDV
Tuesday NIGHT THROUGH Monday...REM


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