Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 141518
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
918 AM CST Tue Nov 14 2017

.UPDATE...With improvement noted in visibilities, Dense Fog
Advisory was allowed to expire naturally at 9 am.

PC

&&

.MARINE...6 PM startup for Small Craft Advisory still looks good
at the moment. Southerly winds are evolving on back side of high.
So far gusts are into the teens. Will continue to monitor the ramp
up in speeds for a potential earlier start time.

PC

&&

.PREV DISCUSSION... (Issued 523 AM CST Tue Nov 14 2017)

UPDATE...

The dense fog advisory will continue across the southeast through
9 am. The fog has spread into Sheboygan and Fond du Lac counties
as skies cleared there. Will be adding them to the advisory
shortly.  Winds will be increasing by mid morning, so this should
quickly lift the fog out of the area.

AVIATION(12Z TAFS)...

Morning fog will bring a mix of IFR and MVFR CIGS/VSBYS to
southern WI. Any dense fog should be limited to the southeast,
where winds are lighter and skies are clear. The fog will lift by
mid morning, with VFR conditions expected for the southeast WI
TAF sites through much of the day. MVFR CIGS will gradually spread
from west to east today, thus KMSN should be MVFR through much of
the TAF period.

Eventually the MVFR CIGS will push into KMKE/KUES/KENW, likely by
early this evening. This is associated with a trough of low
pressure approaching from the west. Southerly winds will increase
today, then shift to the northwest Wednesday morning. Rain showers
are expected with the trough as it moves through.

PREV DISCUSSION... (Issued 326 AM CST Tue Nov 14 2017)

SHORT TERM...

Today...Forecast Confidence Is High.

Surface high pressure will slide off to the east today, as a
trough of low pressure approaches from the west. Clear skies and
light winds across parts of south central and southeast Wisconsin
has resulted in some patchy dense fog. Winds above the decoupled
layer are blowing pretty good, and this is likely keeping the
dense fog from becoming too widespread. Looks like it`s favoring
stratus more than dense fog. But, if trends dictate, we may have
to issue a Dense Fog Advisory for a few hours this morning, if
those winds can`t hold back the other influences to the dense fog
development.

Warm and moist air advection ahead of the trough, in an
increasing southerly flow, could bring some light rain showers to
mainly south central Wisconsin, especially during the afternoon.
In the absence of good low level convergence, since the trough is
so far to the west today, much of the model qpf looks too
aggressive in their eastward extent this afternoon. There is a
weak mid level short wave pushing in that should help to initiate
some of the elevated light showers.

Tonight Through Thursday Night...Forecast Confidence Is Medium.

More focused warm air and moisture advection arrive for mainly
later tonight, with decent low to mid level frontogenesis response
fields pushing east through the region late tonight into Wednesday
morning with the cold front. There is strong differential
cyclonic vorticity advection with a passing 500 mb shortwave
trough as well Wednesday morning. These features will bring a
round of rain to the area, mainly later tonight into Wednesday
morning. A few rumbles of thunder may occur in the far
southeastern portions of the area.

Models are showing a secondary 500 mb shortwave trough with strong
differential cyclonic vorticity advection pushing east southeast
across northern Wisconsin Wednesday afternoon and early evening.
The Canadian is furthest south and clips the area during this
time. For now, will keep dry forecast going as most of the effects
from this feature should remain to the north. Mild temperatures
Wednesday morning should drop behind the cold front during the
afternoon, with cold air advection on gusty northwest winds.

Northwest flow at 500 mb then becomes westerly Wednesday night
into Thursday night. Cooler temperatures are expected during this
period, as high pressure slides east southeast through the region.

Warm air advection then develops later Thursday night, ahead of
the next system moving into the region from the southwest.
Moisture may take its time moving into the region, so continued
with just chance PoPs in the western counties for now.

LONG TERM...

Friday Through Monday...Forecast Confidence Is Medium.

The GFS has slowed the low track through the region Friday into
Friday night, but remains about 6 to 12 hours faster than the
ECMWF and Canadian models. The GFS is also the furthest north with
the low track, taking it east northeast across southern Wisconsin
on Friday. The Canadian takes the low east northeast across
southeast Wisconsin Friday night, with the ECMWF keeping the low
track across far northern Illinois during this time. All models
have an amplified 500 mb shortwave trough moving east through the
region, trailing the surface low.

The surface low continues to show a cyclogenesis trend to the
east of the area Friday night into Saturday, with gusty south
winds shifting northwest behind the low and cold front. There does
not appear to be much of any middle level frontogenesis response
bands that develop after the colder air moves into the region.
Will continue to mention the high PoPs for rain for Friday
afternoon and evening. Chances lower with the colder and drier air
for later Friday night into Saturday morning.

Main issue should be the gusty northwest winds later Friday night
into Saturday night, with the strong cold air advection and tight
pressure gradient expected. Saturday would see the best shot at
Wind Advisory level gusts.

Quiet weather is then shown in the models for Sunday into Monday
at this time. Below normal temperatures should return behind the
low for this period.

AVIATION(09Z TAFS)...

Morning fog will bring a mix of IFR and MVFR CIGS/VSBYS to
southern WI. Any dense fog should be limited to the southeast,
where winds are lighter and skies are clear. The fog will lift by
mid morning, with VFR conditions expected for the southeast WI
TAF sites through much of the day. MVFR CIGS will gradually spread
from west to east today, thus KMSN should be MVFR through much of
the TAF period.

Eventually the MVFR CIGS will push into KMKE/KUES/KENW, likely by
early this evening. This is associated with a trough of low
pressure approaching from the west. Southerly winds will increase
today, then shift to the northwest Wednesday morning. Rain showers
are expected with the trough as it moves through.

MARINE...

Southerly winds will increase today, with Small Craft Advisory
conditions likely being met by 6 pm this evening. These southerly
winds are ahead of an approaching trough of low pressure. Expect
the winds to diminish for a brief time Wednesday morning, as they
veer to the northwest then increase again in the wake of the
trough passage. The Small Craft Advisory will continue through 8
am Thursday.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory from 6 PM this evening to 8 AM CST Thursday
     for LMZ643>646.

&&

$$
Today/Tonight and Aviation/Marine...Davis
Wednesday THROUGH Monday...Wood



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