Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 172350
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
550 PM CST Fri Nov 17 2017

.UPDATE...

A cluster of thunderstorms currently in Waukesha/Dodge/Washington
counties is moving to the northeast and should exit to Lake
Michigan within the next hour of so. Behind this heaviest area of
precip, light scattered rain showers have begun to blossom across
much of the CWA thanks to some low level warm air advection. WAA
will gradually diminish as the gradient slackens, weakening the
forcing for ascent and precip chances. Moreover, this weakening
flow combined with very most low levels will result in fog,
potentially dense in some locations.

Thoughts for snow potential tomorrow morning remains the same as
the previous discussion.

&&

.AVIATION(00Z TAFS)...

A cluster of thunderstorms currently in Waukesha/Dodge/Washington
counties is moving to the northeast, likely missing MKE. Behind
this heaviest precip, light scattered rain showers have begun to
blossom across much of southeastern Wisconsin, and will continue
to do so for the next few hours.

Winds will drop off quite a bit later this evening, resulting in
fog. Uncertainty remains as to just how low the visbys will go.
However, IFR cigs are likely across the southeastern Wisconsin
through the night, potentially dipping to LIFR for a few hours,
especially in the west.

A cold front will push through the area in the early morning,
swinging winds around to the northeast. This will force an
additional round of precipitation along with cooler temperatures,
resulting in a chance for a quick shot at some wet, slushy snow.
Any accumulations will likely be less than 1 inch and should melt
quickly given warm ground temperatures along with air
temperatures a few degrees above freezing.

&&

.PREV DISCUSSION... (Issued 257 PM CST Fri Nov 17 2017)

SHORT TERM...This Evening through Saturday Afternoon...

Mesoscale models are showing the developing band of rain
approaching far northwest Illinois gradually spreading east
northeast and becoming more widespread across the forecast area
into early this evening. This looks to be driven by an approaching
500 mb vorticity maximum. This will also be aided by focused warm
air and moisture advection. There may be a rumble of thunder or
two in the eastern counties as well into early this evening, so
added slight chances for thunder there. The rain should continue
into the evening.

There should then be a relative lull in the rain overnight, as the
cold front pushes through the area. An area of 850 mb to 700 mb
frontogenesis response then pushes into the southeastern half of
the forecast area Saturday morning. In addition, the main 500 mb
shortwave trough also pushes into the area. Thus, there will be
plenty of upward vertical motion and moisture available.

The forecast soundings are showing potential for a period of snow
to occur, as the saturated air column gets mostly below freezing.
The dendrite snow crystal growth zone also gets tapped during
this period. Thus, there could be a quick 1/2 to 1 inch or so of
slushy snow accumulation Saturday morning, before it changes back
to rain. This may impact travelers and hunters during this period.

There remains some uncertainty as to where exactly this band may
set up, with the mesoscale models showing the southeast half of
the area most affected. However, some of the far southeast may be
too warm for snow. For now, will message the potential for the
snow to occur with the slushy accumulations Saturday morning.
Gusty northwest winds are expected after the front moves through
Saturday, which will make for a raw day for hunters.

LONG TERM...Saturday Evening through Next Friday...

Expansive surface high pressure will push east across much of the
nation`s midsection Sunday and Monday. Winds will become
southwesterly by Monday, setting the stage for a fairly nice day
with temperatures in the mid to upper 40s and partly to mostly
sunny skies. Another cold front will pass through the area
Tuesday, and while this frontal passage looks to generally be dry,
it will knock temperatures back into the low 30s for Tuesday and
Wednesday.

Dry conditions then look to continue for Thanksgiving Day and the
following Friday, with highs in the upper 30s/low 40s and lows in
the mid to upper 20s.

AVIATION(21Z TAFS)...

Rain showers will continue to move through the area this
afternoon. One area should become more widespread as it moves east
northeast into and across the area. There may be a rumble of
thunder into early this evening in eastern portions of the area.
Gusty south winds are expected to continue into the evening,
before weakening. Rain is then expected into the middle to late
evening hours, tapering off from west to east by or soon after
midnight.

The cold front will move east through the area later tonight,
exiting the southeast counties between 09Z and 12Z Saturday. Gusty
northwest winds are then expected to develop soon after the
frontal passage, lingering through Saturday and into Saturday
night.

A band of snow should affect portions of the area Saturday
morning. The best shot should be across the southeast half of the
area, which would include Sheboygan, Janesville, Milwaukee,
Waukesha, Racine and Kenosha.

A quick 1/2 to 1 inch of slushy accumulation is possible where
the snow can linger. Road temperatures suggest that pavement areas
may remain wet, but a quick burst of snow could still bring the
above mentioned slushy accumulation. There remains some
uncertainty on where exactly the band would set up, so stay tuned
for later forecast updates.

MARINE...

Small Craft Advisory continues this afternoon and tonight for the
nearshore waters. Areas near Sheboygan may see a few southerly
gusts approaching gale level this afternoon, before winds decrease
for a time later tonight.

A cold front will pass through the area shortly after midnight,
with winds becoming northwesterly and increasing substantially by
morning. A Gale Warning is in effect starting mid morning on
Saturday, continuing into Saturday night.

Beyond this weekend, fairly quiet weather is expected. Small
Craft Advisory conditions may again be met around Tuesday with
another frontal passage.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 4 AM CST Saturday for LMZ643>646.

     Gale Warning from 9 AM Saturday to midnight CST Saturday night
     for LMZ643>646.

&&

$$

Update...BSH
Tonight/Saturday and Aviation/Marine...Wood
Saturday Night through Friday...Boxell



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