Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 160838
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
238 AM CST Mon Jan 16 2017

.TODAY AND TONIGHT...Forecast Confidence is Medium.

A closed upper low, now evident in moisture channel imagery near and
northeast of the Texas pan handle, will lift to near Kansas City
this afternoon, before emerging over the lower Missouri valley this
evening. The upper wave will escort a weak surface low, as it tracks
northeast towards northern Illinois this evening. One band of
precipitation will push into southern Wisconsin this morning.  The
low levels are initially dry, so some of the initial precipitation
will not reach the ground.

The main area of more moderate precipitation arrives late morning
southwest and afternoon over most of the rest of the area.

The primary concern is precipitation types and amounts, with
freezing rain of biggest concern.

A consensus of forecast models keep the surface low track to our
south. This would also keep the low-level jet and best thermal
advection out of our area, resulting in only weak warm advection
over southern Wisconsin by Monday afternoon. This favors light
sleet/snow at onset, with a transition to freezing rain, with mainly
rain from near madison to north of milwaukee, southward as the
warmer air arrives both aloft and at the surface this afternoon. All
forecast models suggest that the precipitation will be ongoing into
the evening.

Things become a bit tricky when assessing the predominant
precipitation types Monday afternoon and evening. Warm air
associated with this system should sufficiently boost temperatures
aloft above freezing for a transition towards partially to fully
melted hydrometeors (in the form of sleet and/or rain/freezing
rain), with warm layer temperatures tilting more towards full
melting especially south. Surface and especially pavement
temperatures will lag the warmth aloft by a bit, with some areas
(especially north and west of Madison) perhaps failing to rise above
freezing. Applying Top Down Methodology to area forecast soundings
would suggest freezing rain as the most likely precipitation type in
our northwest, followed by a mix of rain and freezing rain across
central areas, and mostly rain in the far south and southeast.

Some concern for a more prolonged icing event in our northwest,
where subfreezing surface temperatures and sufficient QPF could
produce 0.1 to 0.2 inches of ice accretion. This could be just
enough to bring down some weak tree branches if realized. However
temperatures are borderline, which could end up reducing ice totals.
In general, our forecast suggests light icing up to 0.1 inches is
possible along and northwest of a Janesville, to Waukesha, to West
Bend line. The greater risk for 0.1 to 0.2 inches of ice would be
along and northwest of a Darlington, to Madison, to Sheboygan line,
with around 0.20 inches northwest areas towards the Dells.

A Winter Weather Advisory is in effect for all areas where a light
glaze of icing or more is expected. Sleet and snow accumulations
within the advisory area will be limited. It`s important to keep in
mind that only a small amount of freezing rain can create travel
headaches on cold and untreated road surfaces.

.TUESDAY - Confidence...Medium
Potent mid level wave vcnty ne IL will shift off to the east early
and be replaced by another one pivoting into nrn IL during the
afternoon. The surface low will be across nrn IL at the outset and
shift to the eastern Lakes by days end. Precip will be winding down
from west to east but spotty light rain/drizzle or even some flakes
may linger into the erly eve in the se due to the secondary wave and
low level trough. However just a weak cool pool so so probably can
get by with liquid for predominant precip type. Some of the earlier
models were showing a bit more cold air upstairs but this is now
less pronounced.

.WEDNESDAY AND THURSDAY - Confidence...Medium
Mid level ridging will be dominant with a mild west then southerly
flow setting up which pushes 850 temps well into positive territory
celsius. So expecting temps getting close to 40 Wednesday and in the
40s for Thursday.

.FRIDAY THROUGH SUNDAY - Confidence...Medium
Mild pattern expected to persist. Mid level flow becomes more active
from the southwest with various solutions on how energy in the flow
will evolve and induce areas of cyclogenesis. However despite these
differences there appears consensus that we will remain above normal
on our temps and precip will be in the form of rain.

&&

.AVIATION/12Z TAFS/...An initial band of mixed precipitation should
push northeast into southern Wisconsin this morning. Milwaukee,
Waukesha and Kenosha should see a few hours of mixed precipitation
that could start as light snow and light sleet, before mixing with
freezing rain. The low levels will initially be dry, so expect not
all the precipitation will reach the ground. Expect the main surge
of precipitation to occur late morning and afternoon, and through
the evening. Expect much of this precipitation to be freezing rain
and then mainly rain in the far south and southeast near lake
Michigan.

Madison should see mixed precipitation Monday morning transitions to
a longer period of freezing rain/rain Monday afternoon and night, as
will areas to the north and west of there. Ice accumulations of
around 0.10 inches are possible at Madison Monday through Monday
night, along with a dusting of snow Monday morning.

Should see ceilings gradually drop to IFR later this morning then to
LIFR this afternoon and tonight.

&&

.MARINE...Light southeast winds today, ahead of approaching low
pressure. Tightening pressure gradient ahead of the low will
result in east southeast wind gusts approaching Small Craft
Advisory levels late Today and into tonight.

Gusty west winds in the wake of the low will again approach Small
Craft Advisory levels later Tuesday and Tuesday evening.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY until noon CST today for WIZ066-071-072.

     WINTER WEATHER ADVISORY until 6 PM CST this evening for
     WIZ062>065-067>070.

     WINTER WEATHER ADVISORY from 10 AM this morning to 6 AM CST
     Tuesday for WIZ046-047-051-052-056>060.

LM...None.
&&

$$
TODAY/TONIGHT AND AVIATION/MARINE...Hentz
Tuesday THROUGH Sunday...Collar


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