Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000
FXUS63 KMKX 200249
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
849 PM CST Thu Jan 19 2017

.UPDATE...
The band of rain is lifting across the area as expected. The forecast
is on track. There is some concern with temperatures hovering
around 32 in Washington and Sheboygan counties. But, I think
there is just enough of an edge above freezing that we shouldn`t
have any serious concerns with ice. Dewpoints are right at the air
temp, so evaporative cooling isn`t a concern. Those temps may
even edge up a degree or two tonight as the warmer airmass
continues to lift north into the region. The main concern this
evening has been the fog. Mitchell Airport went down hard, as did
other locations north of there. As expected, the rain is helping
to scour out the fog a bit. But, once the rain diminishes later
tonight, that fog/vsby could go really low again and spread west
across south central Wisconsin. The morning commute may be a slow
one again.

&&

.AVIATION/06Z TAFS/...

IFR conditions will likely prevail through the TAF period. Fog is
the main concern tonight through Friday morning. So far, the dense
fog has been limited to southeast Wisconsin. The rain moving
through will cause the fog to lift at times, then likely go back
down with significantly restricted visibilities when the rain lets
up. Expect variability. Around sunrise, the rain will be lifting
north and winds will be light. At that point, the fog could be
spreading west into south central areas with much of southern
Wisconsin under dense fog. Drizzle will likely continue as well.
We don`t really see conditions improving until Saturday.

&&

.MARINE...
Dense fog advisory runs through Friday morning. Winds and waves
are expected to remain below small craft advisory levels through
early next week.

&&

.PREV DISCUSSION... /Issued 152 PM CST Thu Jan 19 2017/

SHORT TERM...

TONIGHT AND FRIDAY...Forecast Confidence...High

Surge of moisture this afternoon into this evening will push
precipitable water values up to nearly an inch. Kept high pops going
based on enough forcing with a trough that will lift through the
forecast area tonight into Friday. Rain is quickly approaching the
southwest this afternoon and will move in by late afternoon. The
rain will eventually wind down in the northeast tomorrow morning.
Went with mention of drizzle and fog through the remainder of the
day tomorrow based on model soundings saturated in the lowest 4-5
kft along with some weak lift.

Could see some dense fog again tonight into Friday based on light
winds and saturated low levels. Best chance for this will be after
the widespread rainfall comes to an end.

Temps will remain above normal tonight/tomorrow. Stuck close to raw
model temps based on expected precip, clouds, and fog.

Friday night through SUNDAY...Forecast confidence is medium.

The shortwave trough near the lake superior region lifts north as
a southern stream trough moves across texas and into the upper
ohio valley, as yet another shortwave exits Texas and crosses the
Lower Mississippi valley Sunday.

Forecast soundings show the mid levels of the atmosphere cools,
but the boundary layer is still warm enough for any precipitation
to be liquid.

700 mb upward motion increases Saturday morning before lifting
north Saturday night.

A surface low moves north across Iowa and into eastern Minnesota,
while drawing warmer air into our area on southerly winds. While
we`ll see a chance for rain showers in southern Wisconsin, the
better rain chances remain to our west over Minnesota and Iowa and
closer to the better dynamic and thermodynamic support. Thermal
advection boosts 925 temperatures to around 5 to 7 degrees Celsius
on Saturday, supporting mild highs in the upper 40s/lower 50s
given moist profiles. Slightly cooler air will spill in behind
the departing low on Sunday, but we should still make it well into
the 40s for highs. Skies will be mostly cloudy given plenty of
low-level moisture through the period, with some decrease Sunday.

LONG TERM...

MONDAY THROUGH Thursday...Forecast confidence is medium.

An upper ridge briefly builds across southern Wisconsin and the
Mississippi Valley MOnday night before a trough Moves across the
Central and southern Rockies into the plains. The trough moves
into southern Wisconsin Tuesday night before reaching the Lake
Huron area Wednesday.

The surface low moves across the southern Wisconsin area Tuesday
night and Wednesday morning. Some rain/snow mix is possibly toward
central Wisconsin with mainly rain south. Again the boundary layer
is relatively warm even towards central Wisconsin, by later
Wednesday thickness cools and precipitation would likely trend
toward snow. The 12Z ECMWF continues a more southern track, with
more snow in the south.

AVIATION/00Z TAFS/...

Rain will arrive from the south late this afternoon into early
evening. The rain will taper off later tonight into Friday morning.

Visibilities have improved this afternoon, through a few obs are
still reporting dense fog. With light winds remaining, will likely
see more fog tonight into Friday, possibly becoming dense again for
a time after the rain ends.

Low clouds are expected to hang around through Friday.

MARINE...

Dense fog is still holding on in many marine areas, so may need to
extend the advisory into the evening. The arrival of the rainfall
this evening should help to improve conditions for a time. Dense fog
may return behind the rainfall later tonight into Friday.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...DENSE FOG ADVISORY until noon CST Friday for WIZ051-052-059-060-
     065-066-071-072.

LM...DENSE FOG ADVISORY until 10 AM CST Friday for LMZ643>646.

&&

$$

UPDATE...Davis
TONIGHT/Friday AND AVIATION/MARINE...DDV
Friday NIGHT THROUGH Thursday...Hentz


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