Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 102350
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
550 PM CST Sun Dec 10 2017

.UPDATE...

Stratocumulus have again taken hold. These may scatter out this
evening as mid level clouds push in.

&&

.AVIATION(00Z TAFS)...

MVFR CIGS are expected into the evening before scattering out as
mid clouds move in. A period of warm air advection and light snow
will bring MVFR CIGS back to the area after midnight. Those lower
CIGS will spread quickly southeast across southern Wisconsin
late tonight, then remain there through the day on Monday. The
light snow is still expected to reach KMSN by around 09-10z
Monday and KMKE a few hours later. We should see a lull in the
precipitation by mid morning, with more light snow expected by
early afternoon, then ending by Monday evening. Amounts are still
in the 1 to 2 inch range. There is a minor threat for a period of
freezing drizzle in the morning on Monday after the first band of
light snow moves through, but amounts look too light for there to
be much impact.


&&

.PREV DISCUSSION... (Issued 235 PM CST Sun Dec 10 2017)

DISCUSSION...

Tonight and Monday...Forecast confidence is high.

Our cold northwest flow continues. A potent mid level short wave
will track southeast in the that flow, moving from central North
Dakota late this evening, to central/south central Illinois by
sunset on Monday. Ahead of this wave, moderate warm air advection
will reach our northwest forecast area around Sauk county between
midnight and 3 am, moving quickly east/southeast from there.
Precipitable water values increase from less than .25" to just
over .50" by sunrise on Monday. Look for an area of light snow to
overspread the area with the arrival of this warmer and more moist
air. The column will be cold enough to keep it all snow.

We could see the snow end for a time during the morning as the WAA
pushes off to the east and we lose some column moisture and lift.
The next round of light snow will be associated with the short
wave passing by to the west and south in the afternoon. During
that potential quiet period in the morning, we could see some
light freezing drizzle. It is iffy to begin with and amounts would
be very light, so minimal impact is anticipated.

Some of the guidance has shifted the narrow band of snow expected
with the short wave farther south than the overnight guidance had.
But, it`s a split decision. The concern with these short wave
generated snows is the potential for a narrow, focused band of
higher accums. Tough to place precisely, not to mention the final
total. For now, we`ll keep the general 1 to 2 inch potential, but
wouldn`t be surprised if we get some 3 inch reports in a narrow
east/west oriented corridor...if it sets up.

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

Any lingering precip will exit quickly by Monday evening, then
cold air plows into the region behind a departing cold front.
Highs on Tuesday will likely stay down in the upper teens with
dry high pressure overnight. Lows in the single digits are likely
for Tuesday night.

Wednesday and Thursday...Forecast confidence is medium.

The cold northwest flow persists and yet another short wave is
expected to take a similar track southeast across the region. This
one doesn`t look as potent and the moisture is more limited, but
we could see some light snow from time to time during this period.
Very little accumulation is expected at this time.

Friday and the weekend...Forecast confidence is medium.

The long range guidance is in pretty good agreement that low
pressure will track north of the area...from North Dakota Friday
afternoon, to eastern Lake Superior by Saturday night. There`s a
chance of snow with the warm air advection ahead of the low and
also with the trough/cold front Saturday night. Temps will begin
to warm with this system passing to the north, which brings more
of a wintry mix concern for late in the week.

AVIATION(21Z TAFS)...

VFR CIGS are expected through the evening. A period of warm air
advection and light snow will bring MVFR CIGS back to the area
after 06z Monday. Those lower CIGS will spread quickly southeast
across southern Wisconsin later tonight, then remain there through
the day on Monday. The light snow is still expected to reach KMSN
by around 09-10z Monday and KMKE a few hours later. We should see
a lull in the activity by mid morning, with more light snow
expected by early afternoon, then ending by Monday evening.
Amounts are still in the 1 to 2 inch range. There is a minor
threat for a period of freezing drizzle in the morning on Monday,
but amounts look too light for there to be much impact.

MARINE...

Increasing northwest winds in the wake of a passing cold front
will likely bring small craft advisory conditions to the
nearshore waters from Monday evening into Tuesday night. A few
gale force gusts are possible later Monday night.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

Update...Hentz
Tonight/Monday and Aviation/Marine...Davis
Monday Night through Sunday...DDV


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