Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 032131
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
331 PM CST Sat Dec 3 2016

.SHORT TERM...

TONIGHT and SUNDAY...Forecast confidence is high.

Overcast skies and dry weather expected through midnight. A midlevel
trough will approach the region later tonight becoming negatively
tilted and passing through the region on Sunday. QPF is a tad higher
with todays model runs. Have issued a winter weather advisory since
it looks like a solid 2 to 4 inches across the area. This is the
first accumulating snowfall of the season and often catches
travelers off guard. Ensemble probabilities show there is a small
chance for getting around 5 inches.

There is good synoptic lift and soundings show decent omega in the
dendrite growth zone for about a 6 hour period from late morning to
late afternoon. There is broad, weak warm air advection and weak
frontogensis across southern WI. There is strong upper level
divergence from a 140 knt upper jet during the morning then it
weakens as the jet moves east during the afternoon. Models are in
good agreement with 1000-500mb thicknesses and model consensus
during the peak of the event is 12:1. Wet bulb temperatures around
the freezing mark supports all snow for this event despite highs of
34-35 degrees. Road temperatures today were in the mid 30s so using
this as a rough estimate for pavement temps tomorrow think snowfall
rates will be high enough to overcome warm roads and accumulate on
pavement.

SUNDAY NIGHT... Forecast confidence is medium.

Dry air will work its way into the mid levels early Sun evening.
This will cut off the snow quickly due to the loss of ice crystals,
but lingering low level moisture could lead to drizzle. Temps are
expected to drop below freezing by mid evening. Any lingering
drizzle could become freezing drizzle. Not enough confidence in low
level moisture hanging around with the fairly strong push of dry air
aloft, so no mention of freezing drizzle in wx fcst right now.

.LONG TERM...

MONDAY AND TUESDAY... Forecast confidence is high.

A closed upper low over northern Mexico will make its way over to
the Tennessee area by Tue morning. Meanwhile, a large upper trough
over south central Canada will dip down through the Upper Midwest
and drop much colder air into southern Wisconsin by Tue evening. The
cold front could bring a few flurries.

The TN surface low could cause some light rain/snow to brush
southeast WI Mon night/Tue morning. The ECMWF has trended farther
east with this feature now, but the NAM still suggests light precip
in southeast WI. Snow ratios would be low and sfc temps would be
rising just above freezing with the increasing clouds, so no snow
accum.

We will see breaks in clouds during this period, but they won`t be
long-lived. High temperatures Mon and Tue will be in the upper 30s
to around 40, so the snow on Sunday will have a good chance to melt.

WEDNESDAY THROUGH FRIDAY... Forecast confidence is medium.

Brisk west winds and cold temperatures will be the main story for
the latter half of the week. Models are now in good agreement on the
location of a closed upper low over sliding across Ontario Canada.
We could see flurries off and on through this period.

SATURDAY... Forecast confidence is low.

The GFS and ECMWF bring a surface low through the Midwest Saturday
night. The GFS is farther north with the low and has a more
amplified upper trough, so it brings accumulating snow through
southern WI. The ECMWF keeps most of the snow to the south of the WI
border. This is our next system to watch.

&&

.AVIATION/00Z TAFS/...

A period of VFR conditions is expected late this afternoon then some
lower cloud bases may move back into the region. Upstream
observations show 2500 to 3500 ft ceilings with some breaks in the
clouds. Think this will slowly spread across southern WI.

On Sunday morning ceilings will quickly drop to IFR as snow moves
into the region. Visibility will probably drop to IFR with the snow.
2-4 inches of snow is expected by Sunday evening, with the highest
amounts occuring from Madison and southwest. Road temperatures today
were in the mid 30s so using this as a rough estimate for pavement
temperatures tomorrow we think there snowfall rates will be high
enough to overcome these warm temperatures and it will accumulate on
pavement. Snow will end late afternoon in south-central and during
the evening in the southeast. VFR conditions are expected later
Sunday night.

&&

.MARINE...

Light winds will prevail tonight. Then south winds will pick up on
Sunday. Southwest to west winds will approach small craft advisory
levels sunday night. There is a chance for sustained gusty winds and
high waves at times starting Teusday night.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY from 7 AM to 6 PM CST Sunday for WIZ051-
     052-058>060-064>066-069>072.

     WINTER WEATHER ADVISORY from 3 AM to 6 PM CST Sunday for WIZ046-
     047-056-057-062-063-067-068.

LM...None.
&&

$$

TONIGHT/Sunday AND AVIATION/MARINE...Marquardt
Sunday NIGHT THROUGH Saturday...MRC



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