Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 242354
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
554 PM CST Fri Feb 24 2017

.UPDATE...

Updated for 00Z TAFS.


&&

.AVIATION/00Z TAFS/...

Freezing drizzle now affecting much of the area will expand
southeast into the Milwaukee, Racine, and Kenosha areas over the
next 2 to 3 hours as temperatures cool. Precipitation will then
transition to snow from west to east overnight. This change should
start in the Madison area around 8-9 PM, and in the Milwaukee
area around Midnight. Around 1 to 2 inches of snow accumulation is
expected, with the greater amounts west of Madison.

Prevailing IFR category ceilings are expected, with visibilities
down around 2 to 4 SM on average. We could see briefly lower
visibilities when the snow begins. Light snow showers will taper
off from west to east Saturday morning.

Northerly winds will ease this evening, before picking up again
later tonight into tomorrow. Gusts of 20 to 25 knots are expected.


&&

.PREV DISCUSSION... /Issued 321 PM CST Fri Feb 24 2017/

SHORT TERM...

TONIGHT AND SATURDAY...Forecast confidence is medium.

Ongoing drizzle across southern WI due to shallow saturated air
warmer than -8C (the snow growth zone), and weak lift as low
pressure tracks through northern IL and southern MI.

Temperatures are hovering just below freezing across much of south
central WI this afternoon. Expect temps to drop below freezing in
portions of southeast WI through late afternoon as the sun goes
down. I expanded the winter weather advisory to include all but
Milwaukee, Racine, and Kenosha counties. Light ice accumulations due
to freezing drizzle on untreated roads could cause slippery driving
conditions during the afternoon commute.

It should take a little longer for far southeast WI to drop
below freezing, so we should have a shorter time period of
freezing drizzle than inland areas. I opted to leave these counties
out of the advisory.

Deeper saturation and stronger forcing within a band of 850-600mb
frontogenesis will slide eastward across WI overnight. This will
allow for ice crystals in the column and therefore accumulating
snow. This band is currently over southeast MN and it is expected to
reach south central WI around midnight. Expect 1 to 2 inches by
Saturday morning. Light snow showers will taper off from west to
east Sat morning.

Saturday Night and Sunday...Forecast Confidence...High

Models continue to show a weak mid level trough moving across
Wisconsin. A chance of light snow, mainly north areas.
Surface/850 low tracks to our north with a weak trough in the low
levels across southern Wisconsin. 925 temperatures will bounce
back to freezing so some moderation in temperatures.

MONDAY...Forecast Confidence...High

Still looks dry as weak surface high moves off to the east. A bit
of a return flow sets up but low level flow is weak.

LONG TERM...

MONDAY NIGHT THROUGH WEDNESDAY...Forecast Confidence...Medium

Next low is still forecast to move across Wisconsin Tuesday and
Tuesday night as it strengthens. At this time it still looks like
mixed precipitation for us with the GFS trending colder. Colder
air on the back side of the low Wednesday.

THURSDAY and FRIDAY...Forecast Confidence...Low

The GFS takes a strong low across the lake superior area Thursday,
while the ECMWF has only weak troughing across Wisconsin.

Both the GFS and ECMWF bring a weak high across Friday.

AVIATION/00Z TAFS/...

Drizzle and freezing drizzle is expected through the evening hours,
depending on surface temperatures. Freezing drizzle will expand east
from late afternoon into the early evening, then change over to snow
from west to east from late evening into the overnight hours. 1 to 2
inches snow accumulation expected.

Mainly IFR category ceilings with visibilities down to 2 to 4SM
are expected through the night. Gusty northeast winds today will
back north this evening and northwest overnight. Look for light snow
showers to taper off from west to east Saturday morning.

MARINE...

Gale Warning will expire at 6 pm. Small Craft Advisory then in
place into saturday evening as the strong low over the eastern
great lakes moves off to the east, and brisk northwest winds
persist.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 6 AM CST Saturday for WIZ046-047-
     051-052-056>060-062>065-067>070.

LM...Small Craft Advisory until 9 PM CST Saturday for LMZ644>646.

     Gale Warning until 6 PM CST this evening for LMZ643.

&&

$$

UPDATE...SPM
TONIGHT/Saturday AND AVIATION/MARINE...MRC
Saturday NIGHT THROUGH Friday...Hentz


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