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000
FXUS63 KMKX 231147 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
547 AM CST Sat Feb 23 2019

.UPDATE...

Adjusted forecast for this morning somewhat to go with more
freezing rain across northern parts of the area, and less snow.
This was based on current trends, with mainly freezing rain or a
wintry mix being reported at automated sites. Thus, more ice
accumulations were added to the northern and northeastern parts of
the area this morning. Values are still up to 0.10 inches in these
area. Highest amounts will still be southwest of Madison. Will
continue to watch surface temperatures and dewpoints, especially
in the southeast, to see if freezing rain will occur in those
areas.

&&

.AVIATION(12Z TAFS)...

Should see a period of mainly light freezing rain at Madison until
around 9 AM CST this morning, then becoming rain. Waukesha should
see about a 2 hour period of freezing rain between 7 AM and 9 AM
CST, before becoming all rain. Milwaukee and Kenosha will see all
rain this morning. If temperatures stay above freezing on gusty
east winds, Waukesha would see mainly rain too. Some uncertainty
here with if the temperatures will continue to warm, and their
effects on precipitation types.

Ice accumulations are possible with any freezing rain, highest
southwest of Madison.

Rain is expected across the entire area by early this afternoon,
with a lull possible. More rain is expected this evening, while
winds weaken, which may allow for fog to form. This will also
bring a period of low level wind shear later this evening into the
overnight hours, with 2000 foot level winds southwest around 40
to 45 knots.

The rain will mix with and change to light snow later tonight,
with gusty west to northwest winds. Any snow accumulations will be
under an inch. May hear a rumble of thunder later this afternoon
into early evening. IFR category ceiling and visibility values
are expected today into tonight.

&&

.PREV DISCUSSION... (Issued 411 AM CST Sat Feb 23 2019)

SHORT TERM...
Today And Tonight...Forecast Confidence Is Medium.

Removed Racine and Kenosha Counties from the Winter Weather
Advisory with temperatures hanging just above freezing in these
locations, and kept the rest of the area as is.

First round of strong upward vertical motion will continue to push
into the area this morning, associated with focused 850 mb warm
air advection and the low level jet nose. Some dry air with
easterly flow in the low levels was working to delay the onset of
the precipitation. Now seeing some ground truth in the western
counties, and this should spread east across the area into this
morning.

Main issue into this morning will be the surface temperatures and
dew points, and their affect on precipitation types. Most models
were too cold with their initializations for temperatures and dew
points early this morning. Used a more realistic blend of Adjusted
LAV and NBM, which gave a steady to slowly rising trend this
morning. Some uncertainty with how far east the freezing rain risk
will get, as temperatures in the east are currently at or above
freezing.

Think Racine and Kenosha Counties will remain above freezing, so
removed them from the Winter Weather Advisory. Kept the rest of
the advisory as is for this morning. There is the potential for
less freezing rain and more rain falling in the rest of the
southeastern counties, if temperatures remain above freezing with
the gusty east winds. Will continue to monitor trends and may
remove more counties from the advisory if temperatures stay just
warm enough.

The best areas for freezing rain will be in the southwestern
counties, where colder surface temperatures and dew points exist.
Ice accumulations here will be in the 0.10 to 0.20 inch range,
with lighter amounts to the east and north. Some light snow/sleet
should occur over the northern counties, before mixing with and
changing to rain by later this morning as temperatures warm just
above freezing. Any accumulations will be light.

Period of light rain is expected this afternoon, with a lull
possible, before the next area of strong upward vertical motion
moves into the area. Strong cyclogenesis with the low passing
northeast through the area, along with a negatively tilted 500 mb
shortwave trough, will drive an area of moderate rain this
evening. Amounts of 0.50 to 1 inch are expected, highest in the
western parts of the area. There may be some rumbles of thunder
later this afternoon into this evening, with tall, skinny and weak
elevated CAPE.

Lighter winds into later tonight may allow for some fog to
develop. Strong cold air advection later tonight should bring a
changeover to light snow from west to east. Amounts will be rather
light. Gusty west northwest winds then will develop toward dawn
early Sunday morning.

LONG TERM...

Sunday...Forecast Confidence is High.
Powerful low pressure should be located over northern Lake
Michigan by daybreak Sunday. Wrap around moisture will clip
southern Wisconsin with a changeover back to light mix/snow in
progress. Minor accumulation of less than an inch is expected, but
could lead to a few slick spots for those traveling during the
morning hours. Flurries may linger into the afternoon toward
central Wisconsin, but most precip should quickly wind down by
midday.

The biggest story will be windy conditions. West/northwest winds
will quickly ramp up Sunday morning. Will let day shift hoist the
advisory to keep any confusion with ongoing headlines to a
minimum. Be assured, though, that sustained west/northwest winds
around 30 mph (give or take) and wind gusts to 50 mph are
expected. Cannot rule out the need for a short fused high wind
warning. A distinct 55kt low level jet spreads over the region
during the day and if we can mix enough, we can tap into that
flow, with a risk of gusts to high wind warning levels. Bottom
line, Sunday will be very windy.

Sunday night onward...Forecast Confidence in Medium.
Surface low moves further away Sunday night and the pressure
gradient will eventually relax. Strong cold advection will send
temperatures well into the single digits, if not a few degrees
below zero toward Lone Rock and the Dells.

Overall, the coming workweek looks cold. Temperatures will be well
below average (a good 10 to 15 degrees on average). Overnight
lows will be in the single digits to mid teens. Daytime highs will
be in the teens Monday and Tuesday, moderating just slightly
Wednesday and Thursday to the 20s.

The upper pattern shifts from southwesterly to zonal. This will
not end the passage of waves every few days, but it will limit
moisture availability. The 00z suite of guidance has a few waves
moving through, though timing in this fast flow is not well agreed
upon. Have maintained light snow chances from time to time, but
at this point any light snow looks to be more of an occasional
nuisance with a dusting here and there. The 00z GFS continues to
be a lone wolf on Friday into Saturday merging energy from both
the northern and southern streams. This is not well agreed upon
and we have ample time to watch any potential system for next
weekend.

AVIATION(06Z TAFS)...
Should see a period of light freezing rain and snow at Madison,
then just freezing rain for an hour or two, until around 9 AM CST
this morning. Waukesha and Milwaukee should see a 1 to 2 hour
period of freezing rain between 6 AM and 8 AM CST, before becoming
all rain. Kenosha will see all rain this morning. If temperatures
stay above freezing on gusty east winds, Waukesha and Milwaukee
would see mainly rain. Some uncertainty here with the temperatures
and their effects on precipitation types.

Ice accumulations are possible with any freezing rain, highest
southwest of Madison. Light snow may fall for a few hours in
northern parts of the area until middle to late morning.

Rain is expected by this afternoon, with a lull possible. More
rain is expected this evening, while winds weaken, which may
allow for fog to form. The rain will mix with and change to light
snow later tonight, with gusty west to northwest winds. Any snow
accumulations will be under an inch. May hear a rumble of thunder
later this afternoon into early evening. Winds should weaken this
evening, which may allow for fog to form. IFR category ceilings
and visibility values are expected today into tonight.

MARINE...
Very strong low pressure is expected to impact the area this
weekend. Winds will initially be easterly this morning,
increasing from the southeast on this afternoon/evening as the
low pressure approaches. Once that low lifts through the lake late
Saturday night, winds will increase considerably from the west
for Sunday. Gales are are expected prior to daybreak Sunday, with
a period of storm force gusts looking increasingly likely from the
mid morning hours Sunday into early Sunday evening. Gales are
expected to dissipate by Monday morning.

Waves will also be very impressive with this system, with 16-20
foot waves (a few as high as 23 feet) expected over the
southeastern portion of Lake Michigan. Over the north half of the
lake, waves of 12 to 16 feet will be common (occasionally to
20ft).

Once this system moves through, high pressure builds into the
region and relatively quiet conditions are expected.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until noon CST today for WIZ046-047-056-
     057-062-063-067>069.

     Winter Weather Advisory until noon CST today for WIZ051-052-
     058>060-064>066-070.

LM...Storm Watch from Sunday morning through Sunday evening for
     LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-
     868-870-872-874-876-878.

     Gale Warning from 3 AM Sunday to 6 AM CST Monday for LMZ080-261-
     362-364-366-563-565-567-643>646-669-671-673-675-777-779-868-
     870-872-874-876-878.

&&

$$

Update...Wood
Today/Tonight and Aviation...Wood
Sunday THROUGH Friday and Marine...Gagan