Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 080912

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
315 AM CDT FRI DEC 8 2017

.TODAY...Forecast Confidence is High.

An area of 925-850mb frontogenesis is producing light snow/flurries
over central WI early this morning. The better forcing is going to
peel off to the east as the front slides south. Clouds and
reflectivity returns with the front over west central WI are
weakening so only expecting flurries as it tracks through southern
WI. Expect some lower clouds in its wake over east central and
southeast WI this morning. There may be a period of mostly clear
skies by midday.

TONIGHT...Forecast Confidence is High.

Light snow will spread southward into WI by mid evening. This is a
little later than previous forecasts. There is strong upper forcing
for this quick shot of snow, with strong potential vorticity
advection, mid level q-vector convergence, upper jet divergence, and
warm air advection aloft. The surface forcing is on the weaker side
and there is some dry air in the low levels to overcome before it

Given the better upper dynamics, time-height cross sections of
models show that the stronger omega is above the dendritic growth
zone. While there will still be dendrites, it appears that the snow
might be a little finer rather than fluffy. The snow ratio will
still be on the mid-high side, around 17:1. QPF is lower and thus
forecast snowfall amounts are now lower, in the 1 to 2 inch range.
The higher amounts will still be toward Sheboygan.

Temperatures during the snowfall will be in the mid/upper 20s where
salt will be effective. Once the snow tapers off after midnight,
temps will be on their way down and northwest winds on the way up.
Blowing snow near the ground could cause some slick spots on
untreated roads.

.SATURDAY THROUGH SUNDAY - Forecast Confidence...Medium to High.

Will continue a small chance for light snow Saturday morning across
the far east due to lingering mid-level deformation and nearness of
upper trof.   Otherwise, gradual clearing can be expected on
Saturday.  Blustery north winds gusting of 25 to 30 knots will
likely cause some drifting snow in open areas.  However held off on
introducing any blowing snow due to expected lower snow amounts.

Otherwise, dry conditions are expected for much of the weekend.
Several weak passing mid-level waves caught in fast northwest flow
will bring periods of clouds to the area.  Possible some flurries
may get shaken out of the mostly mid-level clouds, but low level
moisture remains limited.  Hence wl hold off on introducing any
flurries.  Despite the clouds, southwest breezes may allow temps to
break the 30 mark on Sunday.


SUNDAY NIGHT THROUGH THURSDAY - Forecast Confidence...Low to

North to northwest steering winds will remain dominant through this
period.  These winds will carry several fasting moving clipper
systems across the upper midwest and western Great Lakes during this
period.  First of these clipper systems is expected to move from
south central Canada into the region late Sunday night and Monday.
Although confidence is high on this system moving through early next
week, the Medium range guidance in disagreement on track of this
system during this period.  ECMWF showing more run to run
discontinuity with a more southern track across MN/IA while GFS and
GEM taking northerly track across northern and central WI.  More
southern ECMWF track would bring more widespread snow to southern WI
Monday morning with the focus shifted farther north with other
Medium range guidance.  WPC using a blend of all guidance in
carrying low across southern WI, which is in agreement with some of
the GFS ensemble members.  Even if surface low remains north of the
area, warm air advection and isentropic omega ahead of the system
worthy of carrying some pops for now.  More northerly track may also
bring a mixed ptype on Monday.

Another fast moving system will threaten the area with more -sn on
Wednesday.  The main focus for this period will be the continued
very cold conditions.  The coldest air of the season may plunge into
the area behind the Monday clipper.  925H temps tumble to -12 to -
15C on Tuesday.  With increasing snow pack, temperatures may fall
below zero Tuesay night before clouds begin to increase.


.AVIATION(09Z TAFS)...Radar is showing light returns across central
WI. This weak front will slip south through mid morning and could
bring a few flurries and lower clouds. The better chance of MVFR
ceilings will be right behind the front toward Sheboygan and
possibly Milwaukee. Elsewhere should remain VFR with a clearing
trend besides some high clouds.

Snow will spread into southern WI this evening and temperatures will
be in the mid/upper 20s during it. Timing is trending a little
slower due to dry air in the low levels. Snowfall amounts of 1 to 2
inches are expected, with lowest amounts southwest of Madison and
highest toward lake Michigan (not due to lake effect).
Snow ratios around 17:1 are expected, which is on the average to dry
side. Winds will increase out of the northwest as the snow tapers
off after midnight. This could cause some blowing snow across



The gusty southwest winds will diminish through late morning as a
weak front drops into the area. The current small craft advisory is
in effect until noon now rather than 4 pm.

Look for snow to spread into southern WI from the north during the
evening hours. This will taper off after midnight as northwest winds
start increasing. Another small craft advisory will be needed for
gusty northwest winds early Saturday morning through Saturday
evening. A few gale force gusts are possible.



LM...Small Craft Advisory until Noon Today for LMZ643>646.


SATURDAY THROUGH THURSDAY...MBK is the U.S. government's official web portal to all federal, state and local government web resources and services.