NWS-Milwaukee/Sullivan Forecast Discussion

 

						FXUS63 KMKX 181813 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1213 PM CST Sat Jan 18 2020

.UPDATE...

Snow showers ended temporarily for southern WI. Winds are
increasing out of the west as the low moves into northern Lake
Michigan. The arctic front is just moving into western WI now and
features light snow showers, blustery winds, and falling
temperatures. That will make its way across southern WI this
afternoon. Highest winds will arrive behind it, so late afternoon
into the evening. The colder temp profile will be within the
dendritic growth zone through much of the evening, so we extended
the scattered snow showers and flurries.

&&

.AVIATION(18Z TAFS)...

Ceilings will generally be MVFR between 1500 and 2500 ft across
all of southern WI this afternoon. Ceilings will probably rise
above 2000 ft by the evening, but there is still uncertainty.
There is a lull in the snow showers while winds start increasing
out of the west. The real gusty winds will arrive with the arctic
front which will track across southern WI through late afternoon.
Light snow showers are expected along and behind this front
through the evening, with flurries possibly lingering overnight.
MVFR ceilings should persist through Sunday morning and then lift
to VFR.

&&

.PREV DISCUSSION... (Issued 944 AM CST Sat Jan 18 2020)

UPDATE...

The latest round of snow showers added another inch to the snow
totals this morning. Scattered snow showers will persist through
late morning across southern WI but we will see a diminishing
trend in intensity. Winds are on track to ramp up out of the west
around the noon hour, give or take an hour. The arctic front will
arrive during the mid afternoon. It is currently over the Twin
Cities and Rochester and still features light snow. We should see
scattered light snow showers behind the front this afternoon and
evening, and then possible flurries until the drier air eventually
moves in Sunday morning.

We will need a Wind Chill Advisory for tonight, but will issue
that this afternoon to get a better idea of which counties to
include and not include (portions of eastern WI).

MARINE...

The gale warning for the north third expired at 9 am. Gusty west
winds developing this afternoon should remain just below gale
force for that area. There is a brief lull in the gales over the
south 2/3 right now as the low moves overhead, but west gales will
ensue around midday and really ramp up late this afternoon as the
arctic front arrives. Heavy freezing spray will result.

PREV DISCUSSION... (Issued 535 AM CST Sat Jan 18 2020)

UPDATE...

Some light freezing drizzle and light snow will linger over the
area for the next hour or so. The next batch of snow is moving
east northeast toward the area. This is associated with a potent
500 mb shortwave trough moving through the region. A period of
light to moderate snow is expected between 12Z and 17Z or so this
morning.

There are indications from the mesoscale models that a period of
moderate snow, perhaps with convective snow, will occur with this
feature. There is some weak middle level instability in the RAP
forecast soundings across the area.

Thus, a quick 1 to 2 inches of additional snowfall may occur
through the morning hours. Some light ice accumulations may also
occur on top of the snow that has already fallen. Thus, travel
impacts will continue into this morning.

The Lakeshore Flood Advisory will continue until 9 AM CST this
morning for Sheboygan and Ozaukee Counties. Gusty southeast winds
should gradually weaken and become south this morning, which will
result in reduced wave action on shoreline areas. Localized
flooding near the shoreline, and erosion, remains possible until
middle morning.

AVIATION(12Z TAFS)...

First wave of wintry mix of light freezing rain, freezing drizzle
and snow with IFR/LIFR ceilings and visibility values are moving
east of the area. A period of light freezing drizzle and light
snow then is then expected to linger over the area for the next
hour or two.

A period of snow is then expected to move east northeast through
the area between 6 AM and 11 AM this morning, with a quick 1 to 2
inches possible. Ceilings and visibility values should be
IFR/LIFR category once again, with 1/2 mile visibility and 1/2
inch per hour snowfall rates possible within heavier snow showers.
The snow should move east of the area around noon.

Gusty southeast winds should weaken and become south to southwest
during the morning. Winds will become gusty out of the west by
midday and continue this afternoon and tonight. Some blowing and
drifting snow is expected this afternoon and tonight, though
visibility values should remain MVFR category or greater. Low
clouds may linger this afternoon and tonight, with a few flurries
possible.

PREV DISCUSSION... (Issued 506 AM CST Sat Jan 18 2020)

SHORT TERM...

Today And Tonight...Forecast Confidence Is High.

First batch of mixed precipitation with focused warm air
advection is exiting south central Wisconsin and will linger in
southeast and east central areas for another couple of hours. Loss
of ice crystals is allowing for a wintry mix of light freezing
rain, freezing drizzle and snow to occur.

There will be a couple of hours of light freezing drizzle and
light snow after this first main area of precipitation moves out
of the area. There will then be a period of light to moderate snow
moving east northeast through the area this morning, between 12Z
and 16Z or so. This is associated with a potent 500 mb shortwave
trough moving through the area.

There are indications from the mesoscale models that a period of
moderate snow, perhaps with convective snow, will occur with this
feature. There is some weak middle level instability in the RAP
forecast soundings across the area, with a few cloud flashes seen
upstream in northwest/north central Missouri. Thus, a quick 1 to 2
inches of additional snowfall may occur through the morning
hours. Some light ice accumulations to 0.10 inches may also occur
on top of the snow that has already fallen. Thus, travel impacts
will continue this morning.

Gusty west winds will develop by midday and continue this
afternoon into tonight. Any additional snow this morning should
blow around and lead to blowing and drifting snow into tonight.
The Winter Weather Advisory will continue as is through today, and
it could be cancelled early later on if the blowing and drifting
snow does not cause significant impacts this afternoon.

Low clouds may linger into tonight, with low level moisture
trapped below inversion. Strong cold air advection later this
afternoon into tonight will bring colder temperatures back into
the area. Used colder CONSRaw for temperatures later tonight.

Combination of winds and cold will bring wind chills near or
below 20 below zero in southwestern parts of the area later
tonight into Sunday morning. Will hold off on a Wind Chill
Advisory for now, and let later shifts evaluate need for a
headline.

Sunday through Monday night...Forecast confidence high.

A weak west to east trough will shift swd through the region on
Sunday. Sct flurries will be expected with stratocumulus clouds in
the dendrite zone. Brisk nwly sfc winds will continue with very
cold temps and wind chills for the morning. A Wind Chill Advisory
may be needed for south central WI.

Another shortwave trough will track from srn Canada to the middle
MS River Valley for Sun nt-Mon. Believe this will help maintain
some stratocumulus and flurries. The winds will be much weaker as
the arctic high tracks from the middle MO River Valley to the Ohio
River Valley.

LONG TERM...Tuesday through Friday...Forecast confidence low to
medium.

Swly winds and warm advection will develop on Tue and increase
into Wed due to the departure of the arctic high. A split jet
stream flow will become established across the country for middle
to late week. The models will have difficulties resolving the
interactions of shortwave troughs in both streams. Chances for
rain and snow are forecast for much of this period with milder
temps for Wed into the late week.

AVIATION(09Z TAFS)...

First wave of wintry mix of light freezing rain, freezing drizzle
and snow with IFR/LIFR ceilings and visibility values will affect
eastern parts of the area for another couple of hours. A period
of light freezing drizzle and light snow then is then expected to
spread east over the area until around 6 AM this morning.

A period of snow is then expected over the area between 6 AM and
10 AM this morning, with a quick 1 to 2 inches possible. Ceilings
and visibility values should be IFR/LIFR category once again, with
1/2 mile visibility and 1/2 inch per hour snowfall rates possible
within heavier snow showers. The snow should move east of the
area around noon.

Gusty southeast winds should weaken and become south to southwest
during the morning. Winds will become gusty out of the west by
midday and continue this afternoon and tonight. Some blowing and
drifting snow is expected this afternoon and tonight, though
visibility values should remain MVFR category or greater. Low
clouds may linger this afternoon and tonight, with a few flurries
possible.

MARINE...

For the southern 2/3 of Lake Michigan, including the nearshore
waters, southeast gales early this morning will gradually weaken,
before veering west and increasing to gales to 40 knots by early
this afternoon. These winds will linger tonight, before gradually
weakening Sunday. The Gale Warning remains in effect through
tonight for this part of Lake Michigan. High waves will build over
the eastern parts of the lake as well.

In addition, the combination of strong winds and cold temperatures
moving into the region will bring heavy freezing spray tonight
into Sunday morning. Thus, a Heavy Freezing Spray Warning is in
effect for this period.

For the northern 1/3 of Lake Michigan, southeast gales early this
morning will weaken by middle morning. Thus, the Gale Warning
remains in effect until 9 AM CST this morning. As low pressure
moves nearby today, winds will continue to weaken, before becoming
northwest by later this evening and north later tonight into
Sunday. Gusts will remain below gale force during this time.

Strong high pressure moving from the northern Plains into the Ohio
River Valley Sunday night into Tuesday should bring lighter winds
to Lake Michigan.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 6 PM CST this evening for WIZ046-
     047-051-052-056>060-062>072.

LM...Heavy Freezing Spray Warning from 6 PM this evening to noon CST
     Sunday for LMZ080-366-565-567-643>646-669-671-673-675-777-
     779-868-870-872-874-876-878.

     Gale Warning until 6 AM CST Sunday for LMZ080-366-565-567-669-
     671-673-675-777-779-868-870-872-874-876-878.

     Gale Warning until 3 AM CST Sunday for LMZ643>646.

&&

$$

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