Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 170441
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1141 PM CDT Sun Jul 16 2017

.AVIATION(06Z TAFS)...Small area of stratocumulus lingering over
northwest CWA last several hours. Latest GOES-16 showing sc slowly
diminishing and becoming more few-sct. Expect this trend to
continue next several hours. Temperatures falling quickly during
the evening, may result in some patchy late night fog in
suceptible areas, especially west where dewpoints remain in the
low 60s.

&&

.PREV DISCUSSION... (Issued 936 PM CDT Sun Jul 16 2017)

UPDATE...Drier air continues to surge southwest across southern
Wisconsin. A few stratocu linger over south central but should
continue to slowly thin and dissipate. Drier air and some boundary
layer mixing should prevent significant fog development, however
some late night fog is possible in more susceptible areas.
Overnight lows look in good shape.

MARINE...North to northeast winds will continue to gradually
subside overnight, dropping to 5 to 15 knots after midnight as
high pressure ridge settles over the western Great Lakes. Wl let
Small Craft Advisory expire as planned across northern zones at
03Z, and for now planning on letting southern set expire at 06Z.
Wilmette buoy and south Lake Michigan buoy continue to measure
wave heights of 5 ft but expect wave heights south of North Point
Light to Winthrop Harbor to fall to an average of 3 feet after
midnight.

BEACHES...Waves have fallen/will shortly fall below the 3 to 5
foot range and winds have also diminished. Therefore the swim
risk is no longer high, so will allow the Beach Hazards Statement
to expire at 03z. Waves will continue to diminish into tomorrow,
and remain at or below through the day.

PREV DISCUSSION... (Issued 612 PM CDT Sun Jul 16 2017)

AVIATION(00Z TAFS)...Sct-bkn stratocu continues to diminish
across southern WI last several hours, succumbing to drier air
feeding in from the northeast. Few-sct cu may stick around for
1-3 more hours over parts of south central WI until the drier air
overspreads the area. Drier air and boundary layer mixing should
prevent significant late night fog. Some patchy fog may occur over
south central areas due to slightly higher lingering low level
moisture.

PREV DISCUSSION... (Issued 304 PM CDT Sun Jul 16 2017)

SHORT TERM...

Tonight and Monday...Forecast Confidence is High.

Clouds will scatter out this evening with the loss of daytime
heating. Light winds and dry air will allow for a clear and
pleasant night to try and see if you can spot the aurora boreolis
(northern lights). There is a decent chance of seeing them between
10 pm and 1 am, potentially until 4 am. Here is a good source of
information: www.swpc.noaa.gov/products/aurora-3-day-forecast

High pressure will drift overhead on Monday. There will be a
little push of low level moisture into southeast WI in the
morning which should lead to scattered clouds over the area.
These are expected to diminish in the afternoon. Plan on light
easterly winds and highs reaching the upper 70s to around 80
inland and the lower/mid 70s near the lakeshore.

Monday night and Tuesday...Forecast Confidence...High

An upper ridge across southern Wisconsin Monday night drops across
Illinois and the eastern Great Lakes Tuesday.

850 mb temperatures rise to around 19 Celsius later Tuesday with
850 mb dewpoints increasing to around 15 Celsius, as a 30 knot
850 mb pushes northeast across Iowa toward west central and
southwest Wisconsin.

Receding high pressure over the Great Lakes gives way to a light
south flow across most of southern Wisconsin, with a lake breeze
continuing over the far east. GFS dew points rise inland into the
lower to mid 70s, but is probably a little overdone.

Zero to 1 km mixed layer CAPE rises to around 1500 Joules/kg (a
little more towards madison and west with a weakening cap. Lapse
ares are around 6.8 Celsius/km with weak weak shear of 10 knots
in the surface to 1 km layer.

LONG TERM...

Tuesday night night through Friday...Forecast Confidence...Medium

A zonal upper flow sets up through Wednesday and a bit more
northwest by Friday, as a broad trough forms near and then just
east of the Hudson Bay area. Several jet max`s will move across
the U.S. Canadian border area. The best chances are Tuesday night
and again Friday, but 3 rounds are possible during this period.
Some of the storms could produce moderate to heavy rain.

Very warm and more humid air sets up for Wednesday and Thursday.
Zero to 1 km CAPE rises to 2500 Joules/kg most areas, but near
4000 Joules/kg west of Madison. Low level shear is weak, with zero
to 3 km shear around 22 knots.

Saturday and Sunday...Forecast Confidence...Medium

A rather strong shortwave moves across southern Canada just north
of the Dakota`s and Minnesota Saturday and across the western
great lakes Sunday. The GFS is a little slower and farther north.
Both models bring another round of thunderstorms, with more heavy
rainfall.

AVIATION(18Z TAFS)...

Low clouds are hanging around southern WI longer than expected
today. Look for ceilings to gradually rise through the afternoon.
Clouds will also start to scatter out as we lose daytime heating
late this afternoon. VFR conditions tonight and Monday.

MARINE...

Gusty north to northeast winds will build high waves through the
evening hours. A small craft advisory is in effect. Plan on
lighter winds and waves through much of next week.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 1 AM CDT Monday for LMZ645-646.

&&

$$

Aviation...MBK


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