Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 301537 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
937 AM CST Wed Nov 30 2016

.UPDATE...

Light rain/snow is still expected to push in from the west this
afternoon, as low pressure slowly moves through the state.
Indications based on latest models and upstream conditions are
that the precip will stay very light, with very little rain
accumulation expected and no snow accumulation due to the
borderline temps for snow.

Clouds have moved into all but the eastern forecast area this
morning. Milder temps in the east still seem reasonable given the
longer period of sunshine. Overcast conditions should reach the
lake by late morning.

&&

.AVIATION/18Z TAFS/...

MVFR ceilings have moved into all but the eastern forecast area
this morning and will reach lake Michigan by late morning. Low
clouds are expected to stick around through Thursday, possibly
dipping down to IFR at times.

Light precip will move through this afternoon and overnight,
winding down Thursday morning. A mix of rain/snow today should
transition to mainly snow tonight, before possibly becoming mixy
again Thursday morning. Precip will be very light through this
event, with little to no snow accumulation expected.

&&

.MARINE...

Low pressure will slowly move across the Great Lakes today
through tomorrow. The core of this low should stay mainly north of
the area, with southwesterly winds gradually shifting to westerly
tonight. Winds may approach small craft advisory levels for a time
tonight into tomorrow, mainly south of Milwaukee. Will monitor
incoming short range forecast information over the next few hours
and readdress as needed. With offshore winds expected, the highest
waves should be confined to the open waters.

&&

.PREV DISCUSSION... /Issued 315 AM CST Wed Nov 30 2016/

TODAY AND TONIGHT...Forecast Confidence Is Medium.

The stacked low pressure system over Minnesota will continue to
weaken, but also drift across the Great Lakes by tonight. A trough
will rotate around the low as it moves in, bringing more clouds
and the chance for some light precipitation to southern Wisconsin.
Temperatures will be near wintry precip thresholds later this
afternoon and tonight. The precip will probably hold off in
Madison until mid afternoon, and Milwaukee closer to 6 pm this
evening.

The lack of forcing will keep precip intensity light, and thus we
should favor more liquid than snow through the afternoon. Plus,
pavement temps will be above freezing this afternoon, so no
concerns about slippery pavement. Cooling sfc temps and overall
column temps should result in the precip transitioning over to all
light snow later tonight, but by then it should be diminishing.
Little or no snow accum expected.

THURSDAY THROUGH FRIDAY NIGHT...Forecast Confidence Is Medium.

Models are in decent agreement with the last 500 mb vorticity
maximum rotating through the area Thursday morning and early
afternoon, within cyclonic flow. Kept low end PoPs for Thursday
morning to account for this feature.

Otherwise, the area remains in 500 mb cyclonic flow into Thursday
night, before more westerly flow develops for Friday into Friday
night. Area forecast soundings and low level relative humidity
products show fairly persistent stratus clouds lingering across
the area Thursday into Friday night. Bumped up the cloud cover
during this period as a result.

A rather tight pressure gradient Thursday will gradually relax
Thursday night into Friday night across the area. Temperatures
should be near seasonal normals during this period.

SATURDAY THROUGH TUESDAY...Forecast Confidence Is Medium.

ECMWF/GFS are in decent agreement with a potent 500 mb shortwave
trough sliding east northeast through the region Sunday into
Sunday evening. The ECMWF is a little slower than the GFS with
this feature. Both models show some weak warm air advection in
the low levels just ahead of the shortwave trough, with generally
light QPF values. Continued with chance PoPs for Sunday, tapering
off Sunday night. A transition from light snow to light rain is
forecast at this time for Sunday, as daytime heating ensues.
Temperatures look to remain near seasonal normals.

ECMWF/GFS then are showing some kind of cyclogenesis for Monday
into Tuesday over the northern Plains into south central parts of
Canada. Both of these low tracks keep southern Wisconsin in the
warm sector airmass Monday into Monday night, with a cold frontal
passage Tuesday or Tuesday night. ECMWF is more aggressive with
the 500 mb vorticity maximum clipping the area Tuesday, with the
GFS further to the northwest. For now, continued with consensus
blended PoPs and temperatures for Monday into Tuesday, given the
uncertainty this far out in the forecast period.

AVIATION/12Z TAFS/...

MVFR CIGS will overspread southern Wisconsin this morning.
Moisture is wrapping around a weakening upper level low over
Minnesota. That low will drift east today and tonight, and bring
a chance of light precipitation along with it. The precip should
reach KMSN by about 21z this afternoon, and 00z Thu for
KMKE/KUES/KENW.

It should initially be all rain, but then gradually become mixed
with then change over to all light snow by later tonight. By the
time it changes over to all light snow, it should be diminishing
or ending, so little in the way of accumulation is expected. CIGS
may also drop to IFR levels tonight, but it may be straddling the
MVFR/IFR threshold.

MARINE...

A broad area of low pressure will drift across the Great Lakes
today through Thursday, with the center of the low staying north
of the area. This will result in southwest winds gradually
shifting to westerly tonight. Those winds could approach Small
Craft Advisory levels for a time this evening, mainly south of
Milwaukee. But, given the offshore trajectory, the highest waves
will be out in the open waters.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.

&&

$$

UPDATE...DDV/Gagan
TODAY/TONIGHT AND AVIATION/MARINE...Davis
Thursday THROUGH Tuesday...Wood



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