Small Craft Advisory 10, NWS Milwaukee, WI

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1117 PM CST Sat Jan 26 2019

.UPDATE...Expanded late night Wind Chill Advisory to rest of CWA.
Thinking winds will stay up 3 to 6 kts in the west through late
tonight. With clearing skies, temperatures will start to plunge,
increasing the liklihood of -20 or colder wind chills.

&&

.AVIATION(06Z TAFS)...Clouds and lingering flurries exiting
southeast WI, with shrinking area of stratus in the far west.
Hence expect VFR conditions for most of the late night and Sunday
morning with thickening clouds Sunday afternoon. Snow will spread
across the area in the evening, resulting in rapidly dropping
ceilings and vsbys.

&&

.PREV DISCUSSION... (Issued 922 PM CST Sat Jan 26 2019)

UPDATE...Scattered flurries expected for the rest of the late
evening as weak low level cold air advection moves through
southern WI. Still expect lingering clouds to clear overnight
allowing temps to rapidly fall off. With high pressure ridge axis
remaining to the west, NW winds of 3 to 6 kts will continue in the
eastern areas, contributing to Wind Chills lowering to 20 to 25
below. Added Marquette, Green Lake and Columbia counties to
ongoing Wind Chill Advisory, and was on the fence with Dane.
However winds are expected to drop to 3 kts or calm later tonight,
so negligible winds. Lowered temps most areas, but should not get
as cold as last night due to low level mixing.

MARINE...The threat for heavy freezing spray will continue across
the northern part of the open waters, in areas not ice-covered. A
tightening pressure gradient overnight will result in increasing
northwest winds over the nearshore and open waters later tonight
into Sunday morning, with a few gusts around 30 kts. The strongest
winds are expected Sunday night into Monday, when strong low
pressure passes across the region. Gale Watch will remain in
effect, and likely be upgraded to a Gale Warning on Sunday.

PREV DISCUSSION... (Issued 539 PM CST Sat Jan 26 2019)

UPDATE...Powdery, light snow will taper off from northwest to
southeast through the evening, leaving behind snowfall up to
around 1", with the highest amounts in the south. The surge of low
level warm air advection and mid-level short wave will be pushing
off to the east, ending the light snow. Water vapor imagery
showing the mid-level circulation around KLSE, so extended -sn for
several more hours this evening. Wind Chill Advisory dependent on
late night clearing, so wl be watching that closely as the -sn
wanes.

AVIATION(00Z TAFS)...Pockets of lower ceilings and vsbys
associated with powdery -sn will continue the next 1-3 hours, then
taper off during the late evening in southeast WI. VFR conditions
are expected to return later tonight.

PREV DISCUSSION... (Issued 409 PM CST Sat Jan 26 2019)

SHORT TERM...

Tonight through Sunday...Forecast confidence High.

Very light snow will exit southern Wisconsin early evening. It is
associated with a mid level short wave and warm air advection. Up to
half inch is possible.

Skies will clear later this evening. Winds will be light out of the
northwest as high pressure slides into Minnesota. Went with a wind
chill advisory for eastern Wisconsin where winds around 5-10 knots
combined with lows of -5 to -10 will create wind chill values of -15
to -25. Coldest values will be toward central Wisconsin closer to
the core of colder air. These lows are in the middle range of
guidance and will clearing skies may even by lower. Lights winds
toward western Wisconsin should help keep WC values from tanking as
much.

High pressure will slide across northern Illinois on Sunday so winds
will be light. Highs in the single digits yield day time wind chill
values around -5. Clouds will be in the increase from west to east
ahead of the next system.

LONG TERM...

Multiple, substantial weather impacts expected over the next week.

Sunday night and Monday...Forecast confidence is high.

A Winter Storm Warning has been issued for all of southern
Wisconsin.

The forecast for a major winter snow remains on track. Guidance
continues to exhibit good agreement with the overall low track,
though there are subtle, important differences. The NAM/GFS
continue to have the furthest north track of the low (cutting
across southern WI), while the ECMWF is further south (cutting
across northern IL). Looking at the ensembles, the SREF and GEFS
means have a low track a little further south along the WI/IL
state line while the ECMWF ensembles continue to hone in on
northern IL.

The low track will be a critical component of this system for two
reasons. the first is the ENE fetch of winds to the north of the
low that will provide a 3-6 window of lake enhancement. Second,
coincident and south of the low, a dry slot is expected which
will shorten snowfall duration, introduce a risk for freezing
drizzle and result in lower snowfall amounts. Given that the
ensemble means are favoring a slightly farther south track (along
the WI/IL state line - possibly even further south if you buy the
ECMWF ensemble mean), the forecast snow totals were shifted a bit
further south with this forecast.

A strong low level jet will nose into the region beginning Sunday
evening. Isentropic upglide quickly ramps up and snow will
steadily enter the region from west to east. QPF amounts during
the evening and overnight hours are robust. As always, snow
ratios are tricky, and they will vary considerably given strong
warm advection with this system. In general, have trended ratios
toward the 10:1 to 12:1 range coincidence with the low level jet,
increasing toward 18:1 the further north of the low you go.
Snowfall rates of 1 inch per hour are possible from late evening
through the overnight hours. This will result in substantial
impacts to the Monday morning commute.

Snow on Monday will be dependent on the exact low track.
Additional snowfall north and northwest of the low is expected.
Given the southward lean of the ensemble means, snowfall
expectations were altered most during the Monday morning time
frame. As the low exits, snowfall rates will gradually lessen
through the morning into the afternoon hours, ending from west to
east in the afternoon. End timing will likely need to be tweaked
further.

Overall, expect a broad 5-10 inches of snow across southern
Wisconsin. Where the heaviest band sets up north of the low, 7 to
12 inches is expected. Given a 3-6 hour period of ENE flow,
locally higher amounts for locations along Lake Michigan.

Monday night through Thursday...Forecast confidence is high.

Arctic pressure moves in and extremely cold conditions will
settle over the region. Tuesday night and Wednesday night look to
be the coldest, with lows in the -20 to -25 range (a few degrees
colder in the valley toward SW WI. Highs Tuesday will struggle to
reach above zero, with below zero highs expected area wide on
Wednesday. Wind chills less than -40 are expected both Tuesday and
Wednesday night. With wind chills between -20 and -30 Tuesday and
-30 to -40 on Wednesday. Wednesday will by far be the coldest day
 we have observed in nearly 20 years.

Friday onward...Forecast confidence is medium.

Temperatures will begin to moderate as the brunt of the upper
trough shifts east, approaching near average highs by next
weekend.

AVIATION(21Z TAFS)... Snow showers will exit southern Wisconsin
early this evening. Expect totals accumulations from today of
about one half inch. Visibility could be 1SM at times within snow
showers with ceilings of 800 to 1500ft. Skies will clear later
this evening and winds will be light through Sunday. Lower
ceilings will move in west to east Sunday evening with the onset
of snow.

MARINE...
Nearshore Waters...

West to northwest winds will increase somewhat tonight. May see more
heavy freezing spray tonight into Sunday morning, and at times
through the week, with very cold temperatures remaining over the
region.

Winds will likely reach Small Craft Advisory levels late Sunday
night into Monday night and gales are possible. Winds will likely
remain gusty through much of next week.

Open Waters...

Heavy Freezing Spray Warning continues until 6 PM CST Sunday across
the north half. Winds may remain high enough to maintain it for
the rest of next week.

May see more heavy freezing spray tonight into Sunday morning
over the south half, and at times next week, with very cold
temperatures remaining over the region.

Southeast winds will increase Sunday night and gales are possible.
winds will become northwest on tuesday with gales possible. West
gales may continue later in the week, especially for the south half.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Warning from 6 PM Sunday to 6 PM CST Monday for
     WIZ046-047-056-057-062-063-067>069.

     Wind Chill Advisory until 9 AM CST Sunday for WIZ046-047-051-052-
     056>060-062>072.

     Winter Storm Warning from 9 PM Sunday to 6 PM CST Monday for
     WIZ051-052-058>060-064>066-070>072.

LM...Gale Watch from late Sunday night through Monday evening for
     LMZ080-261-362-364-366-563-565-567-643>646-669-671-673-675-
     777-779-868-870-872-874-876-878.

     Heavy Freezing Spray Warning until 6 PM CST Sunday for LMZ261-
     362-364-366-563-565-567-868.

&&

Update...MBK
Tonight/Sunday and Aviation/Marine...MBK
Sunday Night through Saturday...Gagan

Hazardous Weather Outlook...UPDATED
National Weather Service Milwaukee/Sullivan WI
1029 PM CST Sat Jan 26 2019

WIZ046-047-051-052-056>060-062>072-280430-
Marquette-Green Lake-Fond Du Lac-Sheboygan-Sauk-Columbia-Dodge-
Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee-
Lafayette-Green-Rock-Walworth-Racine-Kenosha-
1029 PM CST Sat Jan 26 2019

This Hazardous Weather Outlook is for portions of east central
Wisconsin, south central Wisconsin and southeast Wisconsin.

.DAY ONE...Tonight

Expect wind chills between 20 and 25 below zero later tonight into
Sunday morning. A Wind Chill Advisory is in effect until 9 am
Sunday morning.

.DAYS TWO THROUGH SEVEN...Sunday through Saturday

A Winter Storm Warning has been issued for all of southern
Wisconsin for Sunday night through Monday. Accumulations are
expected to range from 6 to 12 inches, highest north of
Milwaukee, lower southwest of Madison. Gusty winds will cause
blowing and drifting snow at times, especially in the wake of the
storm Monday afternoon and evening.

Extremely cold air will build into the area starting Monday night.
Wind chills are expected to be less than 35 degrees below zero at
times from Tuesday through Thursday night.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time, but snow reports
are extremely helpful.

LMZ643>646-280430-
Sheboygan to Port Washington WI-
Port Washington to North Point Light WI-
North Point Light to Wind Point WI-
Wind Point WI to Winthrop Harbor IL-
1029 PM CST Sat Jan 26 2019

This Hazardous Weather Outlook is for the nearshore waters from
Sheboygan Wisconsin to Winthrop Harbor Illinois.

.DAY ONE...Tonight

Freezing Spray is possible where the lake is not ice covered.

.DAYS TWO THROUGH SEVEN...Sunday through Saturday

Freezing spray will remain a concern where the lake is not covered
through the coming week, as very cold air moves through the
region.

A Gale Watch is in effect Sunday night through Monday evening as
southwest winds shift to the northwest and gust to around 35
knots.

A prolonged period of gusty west to northwest winds is then
expected from Tuesday through most of the remainder of the week.

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-280430-
Lake Michigan Michigan City IN to St. Joseph MI 5 NM offshore to
mid-line of lake.-
Lake Michigan from Seul Choix Point to Rock Island Passage 5NM
offshore to Mid Lake-
Lake Michigan South of a line from Seul Choix Point to the
Mackinac Bridge and North of a line from Charlevoix MI to South
Fox Island 5NM offshore-
Lake Michigan from Charlevoix to Point Betsie MI 5NM Offshore to
mid lake-
Lake Michigan from Point Betsie to Manistee MI 5NM offshore to
Mid Lake-
Lake Michigan from Rock Island Passage to Sturgeon Bay WI 5NM
offshore to mid lake-
Lake Michigan from Sturgeon Bay to Two Rivers WI 5NM offshore to
Mid Lake-
Lake Michigan from Two Rivers to Sheboygan WI 5NM offshore to Mid
Lake-
Lake Michigan from Sheboygan to Port Washington WI 5NM offshore
to Mid Lake-
Lake Michigan from Port Washington to North Point Light WI 5NM
offshore to Mid Lake-
Lake Michigan from North Point Light to Wind Point WI 5NM
offshore to Mid Lake-
Lake Michigan from Wind Point WI to Winthrop Harbor IL 5NM
offshore to Mid Lake-
Lake Michigan from Winthrop Harbor to Wilmette Harbor IL 5NM
offshore to Mid Lake-
Lake Michigan from Wilmette Harbor to Michigan City in 5NM
offshore to Mid Lake-
Lake Michigan from Pentwater to Manistee MI 5NM offshore to Mid
Lake-
Lake Michigan from Whitehall to Pentwater MI 5NM offshore to Mid
Lake-
Lake Michigan from Grand Haven to Whitehall MI 5NM offshore to
Mid Lake-
Lake Michigan from Holland to Grand Haven MI 5NM offshore to Mid
Lake-
Lake Michigan from South Haven to Holland MI 5NM offshore to Mid
lake-
Lake Michigan from St Joseph to South Haven MI 5NM offshore to
Mid Lake-
1029 PM CST Sat Jan 26 2019

This Hazardous Weather Outlook is for the open waters of Lake
Michigan.

.DAY ONE...Tonight

The combination of gusty winds and very cold temperatures will
result in areas of heavy freezing spray over the north half of
the lake. A Heavy Freezing Spray Warning is in effect there
through Sunday for the north half of Lake Michigan.

.DAYS TWO THROUGH SEVEN...Sunday through Saturday

A Gale Watch is in effect Sunday night through Monday evening for
wind gusts between 35 and 40 knots.

Heavy freezing spray will remain a considerable concern through
the coming week, as very cold temperatures and gusty winds remain
in place across Lake Michigan.

www.weather.gov/mkx

MBK