Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 200240
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
940 PM CDT MON SEP 19 2016

.UPDATE...Showers and storms continue to weaken as instability
gradient further weakens and sags southward. Light winds and
clearing skies has allowed areas of fog to rapidly develop over
central WI into northwest CWA this evening. Expect showers to
diminish and end in the far south shortly after 05z followed by
gradual clearing, however mid/high clouds may hang on in the far
southeast through 09-10z or so. Drier air still expected to sag
south overnight, but remain just above the sfc while high humidity
and dewpoints linger at the sfc. Hence wl introduce fog mention
over most of the area and mention potential for dense fog in
Hazardous Weather Outlook.

&&

.AVIATION/06Z TAFS/...Patchy dense fog developing rapidly where
surface winds have become nearly calm and skies have cleared. Will
need to introduce some fog into most TAF sites for the late night
as expect clearing trend to continue and showers and storms to end
after 05z or so. KMSN may drop to IFR or lower for a time, but
confidence low due to influx of drier air in the low levels from
the north.

&&

.MARINE...Scattered showers and storms will continue to diminish
during the overnight, with areas south of Wind Point experiencing
the last showers and isolated storms through 06-07z or so. Inland
areas of late night fog may drift over some shore areas late
tonight as well.

&&

.PREV DISCUSSION... /Issued 345 PM CDT MON SEP 19 2016/

SHORT TERM...

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

Thunderstorms continue to develop this afternoon and are expected to
move across southern Wisconsin late afternoon into the evening.
Still looks like a favorable setup for severe thunderstorms, so
Severe Thunderstorm Watch has been issued into early evening for
everywhere except the northern forecast area counties.

Showers/storms will wind down late this evening in the southeast,
with dry weather overnight as high pressure quickly moves in. Could
see a little fog develop later tonight, likely mainly confined to
the Wisconsin River valley.

It should be a very nice day Tuesday, with mostly sunny skies
expected under high pressure. Highs will be above normal once again.

TUESDAY NIGHT THROUGH THURSDAY...Forecast confidence medium.

A trough of low pressure and associated low to mid level warm
advection and frontogenesis will develop newd from NE to central WI
from Tue nt-Thu. The nose of the low level jet will focus across
central WI much of this time where numerous showers and tstorms
including heavy rainfall is expected. Did mention heavy rainfall
in the forecast north of Madison but the tendency for MCSs to move
to the right of the mean wind could certainly result in the heavy
rainfall developing farther swd during this period. Fairly large CAPE
values will develop Wed afternoon into the evening which will
be the prime period for a strong MCS and heavy rainfall. A
shortwave trough will approach Wed nt and pass through the area
on Thu so good chances of showers and tstorms to continue.

LONG TERM...FRIDAY THROUGH MONDAY...Forecast confidence medium.

A front will then stall in the vicinity of srn WI into the weekend
with ridging aloft ahead of a sharp upper trough and associated
cold front moving east across the Great Plains. Thus tstorm
chances will continue with above normal temps and humidity. The
cold front is expected to pass Mon night.

AVIATION/00Z TAFS/...

Thunderstorms are expected this afternoon and early evening as a
shortwave moves through the forecast area. Some of the storms could
be severe.

Will likely see some lower visibilities with the storms this
afternoon and evening. Fog development tonight will likely be
confined to low lying areas such as the Wisconsin River valley.
Otherwise, VFR conditions are expected through Tuesday as high
pressure quickly builds in behind the trough.

MARINE...

Southwest winds will ease this afternoon, becoming lighter and
westerly in the evening. Thus the 6 pm Small Craft Advisory
expiration time still looks good.

Winds will be lighter Tuesday under high pressure.

&&

.MKX Watches/Warnings/Advisories...
WI...None.
LM...None.
&&

$$

UPDATE...MBK
TONIGHT/Tuesday AND AVIATION/MARINE...DDV
Tuesday NIGHT THROUGH Monday...Gehring



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