Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 041639
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1039 AM CST Sun Dec 4 2016

.UPDATE...

Trough axis is currently located over western MN and IA and
strong upper divergence from a 150kt jet is over southern WI.
Light snow will continue through the day until the trough axis
departs the east this evening bringing an end to the precipitation.
There is a band of heavier snow across eastern IA and northwest IL
associated with mid level frontogensis. Visibilities in this band
are 1/4 to 3/4 mile and and 3 to 6 inches has fallen in that area.
The NAM and GFS have been consistently showing this frontogensis
moving into far southern WI and sliding east. Latest model runs are
a tad higher with QPF in this area so could see up to 5 inches near
the state line in south-central WI, otherwise still looks like 2
inches near the lake with 3-4 inches elsewhere.

&&

.AVIATION/18Z TAFS/...

1000-2000 ft ceilings and 3/4 to 1 mile visibilities will dominate
this morning with the snow but at times they will be lower. Then a
band of heavier snow will move in across far southern and southeast
WI this afternoon. It will probably stay south of Madison. In this
band visibility will likely be in the 1/4 to 1/2 range with ceilings
likely 200-600ft. Snow will end late this evening and visibilities
will improve. Ceilings will take longer to improve but may reach VFR
around midnight.

&&

.MARINE...

A vigorous low pressure wave and surge of warm, moist air will bring
a mix of rain and snow to the near shore area today into the early
evening.  Look for the mixture to begin late this morning. Southwest
winds will turn to the south to southeast and increase today as low
pressure passes through the western Gt Lakes.  West winds in the
wake of the low pressure trof will approach Small Craft Advisory
levels tonight, but for now thinking most gusts to remain below 23
knots.

&&

.PREV DISCUSSION... /Issued 332 AM CST Sun Dec 4 2016/

TODAY AND TONIGHT...Forecast confidence - Medium to High.

Forecast concern remains first accumulating snowfall of the season
expected today.  Upstream sharpening mid-level trof and surge of
warm, moist air currently causing widespread mostly -sn across IA
into srn MN and has recently began spreading into parts of western
and SW WI.  Patchy -sn has developed over south central WI as warm,
moist air beginning to move in at mid-levels.  Mid-level trof
expected to move eastward across southern WI today with further
sharpening in the mid-levels.  Trof takes on slight negative tilt as
it passes this afternoon.  Strengthening tied to upper level jet and
surge of strong warm air advection around 300H late this morning and
aftn.

NAM also indicating a period of some mid-level frontogenetical
forcing across the far south around 18Z.  Short term guidance in
very good agreement and consistency from run to run so still looks
good for first accumulating snow of the season.  Bumped up QPF
amounts slightly to between 0.30 and 0.45.  With snow ratios of 11-
12 to 1, snow amounts of 2.5 to 5 inches looking likely with highest
amounts west of Madison.  Sfc winds will turn SSE which will carry
slightly warmer air over the shore areas.  This will result in a mix
of rain and snow by the lakeshore and cut down slightly on snowfall
in these areas.

Postponed start of Winter Weather Advisory in eastern areas until
15Z, otherwise rest of advisory looks good.  May be able to cancel
advisory early across parts of the west this afternoon.

MONDAY...Forecast Confidence...High

High pressure will move through briefly on Monday. May actually
see breaks in the clouds in the morning, though clouds will likely
be on the increase by afternoon ahead of the next approaching
trough. Some uncertainty with temps, as the fresh snow cover will
keep temps from warming up as much as they could given milder 925
mb temps. Stuck close to consensus blend of models, which seems to
fall nicely in between milder ECMWF and colder GFS/NAM solutions.

TUESDAY THROUGH SATURDAY...Forecast Confidence...Medium

Tuesday is looking mainly dry, though may see a few snowflakes or
flurries as a wave rotates through. Temps look like they`ll be a
degree or two above normal, but some uncertainty again due to the
extent of snow cover.

Looks dry Wednesday between systems. Have small pops for some snow
then Thu, though models still struggling with the mid-week
pattern.

High pressure is expected Friday, with models diverging again
after that. The ECMWF holds on to the high for Saturday, while the
GFS and Canadian solutions bring a wave and snow chances.

Though precip chances aren`t particularly clear Wed-Sat, models
are in decent agreement that the coldest air of the season thus
far will arrive for the second half of the week.

AVIATION/12Z TAFS/...

Light snow beginning to spread into south central Wi.  Snow will
continue to spread east through the morning.  Lowest cigs and vsbys
along with highest rates are expected from mid-morning through late-
afternoon, from 15z to 22z or so.  Vsbys in falling snow may drop to
below 1 mile for 1 to 2 hours.  Little to no blowing snow expected
due to the wetness of the snow and lack of significant wind gusts.
Snow will taper off during the afternoon and early evening from west
to east.

MARINE...

A vigorous low pressure wave and surge of warm, moist air will bring
a mix of rain and snow to the near shore area today into the early
evening.  Look for the mixture to begin late this morning. Southwest
winds will turn to the south to southeast and increase today as low
pressure passes through the western Gt Lakes.  West winds in the
wake of the low pressure trof will approach Small Craft Advisory
levels tonight, but for now thinking most gusts to remain below 23
knots.

MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY from 9 AM this morning to 6 PM CST this
     evening for WIZ052-059-060-065-066-070>072.

     WINTER WEATHER ADVISORY until 6 PM CST this evening for WIZ046-
     047-056-057-062-063-067-068.

     WINTER WEATHER ADVISORY from 7 AM this morning to 6 PM CST this
     evening for WIZ051-058-064-069.

LM...None.

$$

TODAY/TONIGHT AND AVIATION/MARINE...MBK

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY until 6 PM CST this evening for WIZ046-
     047-051-052-056>060-062>072.

LM...None.
&&

$$

UPDATE...Marquardt
TODAY/TONIGHT AND AVIATION/MARINE...MBK
Monday THROUGH Saturday...DDV



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