Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 240231
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
831 PM CST Thu Feb 23 2017

.UPDATE...
Things are progressing about as expected. We have had a mix of
sleet/snow/rain just to the west and north of Milwaukee. An
impressive enhanced area of precip, with nearly 60dBZ echoes, was
moving through Dane county early to mid evening, headed
northeast. Ground reports indicate huge snowflakes. Large and
somewhat wet snowflakes are amazing reflectors of radar energy.
There will be a little break behind this area, with a few waves
of more precip through the night. The new NAM is not offering any
major surprises, or shifts in the current forecast thinking. If
anything, there might be a shift a tad north with the low and
warmer temps, but not enough to really justify any movements at
this point. The RAOB data was a tight fit to the 6hr model runs,
but the details between these sparsely located obs is critical, so
a fair amount of estimating is going on with respect to the low
level temps.

Southern Wisconsin is sitting within the very complex zone of the
storm where we transition from snow to the north and rain south.
Be prepared rapidly changing conditions overnight, especially
north of a line from Milwaukee to Spring Green.

&&

.AVIATION/06Z TAFS/...

IFR conditions should dominate through the period. Strong low
pressure will track from northern Missouri to southeast Lower
Michigan during the period. KMKE/KENW/KUES should remain all rain
with a few waves of precipitation moving through tonight Friday.
Look for strong and gusty northeast winds as well.

KMSN will remain in the zone of transition between rain to the
south and snow well north. KMSN will see rain/snow/sleet at times
with a potential for a long duration freezing rain threat through
most of the day on Friday.

&&

.MARINE...
Northeast winds ahead of the low pressure and northwest winds behind
the low will be gusty tonight into Saturday evening. No changes were
made with the headlines. Winds could approach gale force for a time
again Saturday.

&&

.PREV DISCUSSION... /Issued 358 PM CST Thu Feb 23 2017/

SHORT TERM...

TONIGHT AND FRIDAY..Forecast Confidence...Medium to High

Strong low pressure will approach from the southwest tonight, then
slide by just to the south on Friday. Widespread precipitation is
expected, ranging from rain in the southeast, to snow and freezing
rain northwest.

Models made a southward shift today, so went colder for tonight and
Friday. This has resulted in higher snow and ice accumulations. Snow
totals of 2-5 inches and ice accumulations of .10 to .30 inches in
the northwest half of the forecast are has prompted the issuance of
a Winter Weather Advisory from midnight tonight through Saturday
night.

Snow and ice will likely cause hazardous driving conditions,
though it may take some time for the milder road temps to cool down
given the recent warm weather. Bigger concern is for icing combined
with gusty winds possibly bringing down tree limbs and power lines.

Biggest forecast challenge for this system is nailing the precip
type. If saturation ends up deeper, then more ice aloft could spell
sleet instead of freezing rain for time. Also, blend of temps aloft
are somewhat weighted by warmer NAM. If colder solutions verify,
this could result in a bit more snow vs freezing rain. These details
will be closely monitored real time as this system continues to
approach.

FRIDAY night AND SATURDAY - Confidence...Medium
Precip will be ongoing at the outset and the transition to snow
will be occuring southeast. Snow amounts will be mainly in the 1
to 3 inch range as the upper low moves across.

As the low pulls away on Saturday any lingering snow will end in
the morning. But it will be chilly with blustery northwest winds
with many areas hitting 30 tops.

SUNDAY...Forecast Confidence...Medium

Models continue to show a weak mid level wave riding through with
a chance of little light snow.

LONG TERM...

MONDAY...Forecast Confidence...Medium

Looks like there is consensus for a dry day with weak ridging
between departed weak system and organizing system in the Plains.

Tuesday THROUGH Thursday...Forecast Confidence...Low

The ECMWF and DGEX is the faster solution on this low with precip
Tuesday. Meanwhile the GFS is much slower. Too much model
variation to get a good handle on precip timing and type.

AVIATION/00Z TAFS/...

Still looks like quite a mess of precip tonight into Saturday as
strong low pressure moves through the region. Rain, snow, sleet, and
freezing rain are all possible with this system. The best chance for
the wintry precip will be along and north of a line from Mineral
Point to Madison to Port Washington, where forecast snow and ice
accumulations have prompted a Winter Weather Advisory. Tough call on
how fast pavement temperatures will cool down, with the bigger
concern being tree limbs and power lines coming down with the icing
and wind.

Southeast areas will remain mainly rain tonight and Friday,
eventually changing to snow Friday night into Sat morning. Only an
inch or so of snow is expected in these areas.

With models taking a fairly significant jump southward today, will
have to closely monitor trends this evening and tonight to watch for
any additional southward movement.

Low clouds are likely through the duration of this system. Lowest
visibilities are expected with the snowfall in the northwest,
possibly dropping to 1/2 mile to 1 miles at times.

MARINE...

Northeast winds ahead of the low pressure and northwest winds behind
the low will be gusty tonight into Saturday evening. No changes were
made with the headlines. Winds could approach gale force for a time
again Saturday.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from midnight tonight to 6 AM CST
     Saturday for WIZ046-047-051-052-056>060-062-063.

LM...Small Craft Advisory until midnight CST tonight for LMZ643>646.

     Gale Warning from midnight tonight to 6 AM CST Friday for
     LMZ643>646.

&&

$$

UPDATE...Davis
TONIGHT/Friday AND AVIATION/MARINE...DDV
Friday NIGHT THROUGH Thursday...Hentz



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