Area Forecast Discussion
Issued by NWS Cleveland, OH

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000
FXUS61 KCLE 110245
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
945 PM EST Sun Dec 10 2017

.SYNOPSIS...
A series of clippers will cross the area through mid week. One will
cross the Great Lakes tonight with another following for Monday
night. High pressure will attempt to build across the lower Ohio
Valley late Wednesday, but a third clipper will cross the Great
Lakes Thursday into Friday.

&&

.NEAR TERM /THROUGH MONDAY/...
Finally getting enough convergence along and ahead of the
trough axis to generate snow showers over the central portion
of Lake Erie. As winds turn to the west and northwest they will
push toward the shore with a quick inch or two of snow likely
from the east side of Cleveland into NW PA. Highest amounts
still look to be over NW PA, mainly across Erie County. Still
looks like the best chances of snow will be from now through
around 4 am then gradually decreasing in coverage.

Previous Discussion...
Erie Co PA will stay under a Winter Weather Advisory tonight with
little change expected in snow accumulations.

Tonight`s clipper is expected to bring a trough across the lake and
bring winds around to the northwest toward/slightly after midnight.
This will bring the lake effect bands ashore mid to late evening and
press them inland. There will be a bit of shear at this point and
expect the band to largely break up into scattered snow showers
across interior sections of the the snowbelt. Far northeast Erie Co.
PA will have the longest possible duration of snow and believe 3 to
locally 5 inches will fall. Rest of the snowbelt would be in the 1
to locally 3 inch range and those outside of the snowbelt a
trace/coating. Fairly quickly after about 09Z, drier air begins to
affect the dendritic growth layer and best lift exits, therefore
lingering snow showers will be much lighter by Monday morning. It is
just a quick shot of snow. Lows in the mid 20s.

Monday will be a quick transition day. Brief ridging ahead of a
stronger clipper for Monday night/Tuesday will clear out the
remaining lake effect out east. By light warm advective snow may be
beginning to affect northwest OH. Expecting no more than a half
inch before 7pm. Highs will again be near 30/lower 30s.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
A cold and snowy stretch of weather remains on track through
midweek. A Winter Storm Watch for lake effect snow remains in effect
for portions of the snowbelt from Monday evening through Wednesday
afternoon.

A 140 knot upper level jet rounding the west coast ridge will dive
south into the Plains on Monday with low pressure developing over
the midwest. This low will move east across the central Great Lakes
and deepen on Monday night as the initial shortwave gets absorbed by
a stronger piece of energy diving south from the Arctic. The upper
trough sets up across the eastern Great Lakes, setting the stage for
an intrusion of very cold air and prolonged northwest flow.

A Winter Storm Watch remains in effect for a portion of the primary
snowbelt from Monday night through Wednesday. The first round of
snow will develop on Monday night as isentropic ascent increases
ahead of the approaching surface low. The better lift is focused
across the northern counties and have highest pops and accums
focused north of a line from Toledo to Youngstown. Accumulations
will range from little if any towards Findlay with 1 to 3 inches
across the snowbelt. As the surface low passes across Lake Erie, the
flow will shift to the northwest pulling a cold front across the
area. Convergence on the back side of the low will result in lake
enhanced snowfall into Tuesday, transitioning to more of a pure lake
effect event by later Tuesday into Wednesday. The arriving airmass
will be very cool with 850mb temperatures of -16 to -18C. The
thermal profile will be favorable for lake effect snow but models
already showing a deep layer of dry air being wrapped into the
system from the west as early Tuesday afternoon. Lake effect snow
will favor the upslope areas, especially as we start to dry out. The
drier air may have a limiting effect on snowfall rates/totals in the
western portions of the watch while the Pennsylvania portion will be
focused downstream of Lake Huron. A little far out to resolve if the
trajectory will favor a dominant band off Lake Huron which could
result in higher amounts. Otherwise expecting a multi-band event
given the northwest wind direction. Forecast accumulations remain
lower near the lakeshore.

Temperatures behind the front will fall through the day on Tuesday
with wind chills on Tuesday nigh near zero in some locations. Highs
on Wednesday will only recover to near the 20 degree mark.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
A clipper type low should be near Lake Erie Thu evening then move
off to the east into Fri causing the more widespread threat for snow
to transition to mostly a lake effect threat for the snowbelt. The
lake effect should try and taper off Sat as high pressure moves east
into VA causing winds to back more toward the south. However, there
is a threat for some light warm advection snow near Lake Erie Sat
into Sat night.

Another low races east across the lakes late Sat night and Sunday
pulling a cold front across the region Sunday. The low and cold
front will combine to produce a decent chance for light snow over
most of the area.

Below normal temps Fri will moderate closer to normal for Sat and
Sun.

&&

.AVIATION /00Z Monday THROUGH Friday/...
The next trough will move toward the region this evening. The
expectation is that lake effect snow will develop southwestward
toward the middle of Lake Erie. As the trough moves across the
region it will grab the bands of snow and bring them onshore
between Cleveland and Erie. This will likely occur between 03Z
and 09Z then gradually dissipate. Expect IFR conditions while
the snow is occurring. Otherwise VFR conditions for the area
ahead of the trough. As the trough approaches and in its wake
all locations should see some MVFR conditions for a few hours.
We then will see clouds lift through Monday morning with VFR
conditions returning for a few hours. This will be short lived
as ceilings begin to lower from west to east through the
afternoon. MVFR conditions return with areas of snow developing
late afternoon into the evening.

Southwest winds this evening will become northwest in the wake
of the trough. Gusts 15 to 20 knots will be possible closer to
the lakeshore with the northwest winds. As the next storm
system approaches on Monday winds will become southerly for all
locations.

OUTLOOK...Non-VFR likely Monday night into Tuesday morning area
wide and continuing across northeast OH/northwest PA through
Wednesday night. Areas of non-VFR Thursday and Friday as well.

&&

.MARINE...
Water levels on the western basin have fallen to just above the
critical mark for safe navigation. Winds are forecast to decrease
this evening and slowly veer to the northwest which should allow
water levels to come back up.

A Small Craft Advisory remains in effect until 4 AM for the eastern
two thirds of Lake Erie with southwest of 15 to 30 knots, shifting
to the northwest and decreasing overnight. A ridge will build over
the lake on Monday with winds of 15 knots or less, backing to the
southwest. An area of low pressure will cross the lake on Monday
night, pulling an arctic front south across the area with strong
northwest winds developing behind the front on Tuesday. If a compact
trough sets up across Lake Ontario as models are showing, then a
window of gale force winds may be possible on the east half of the
lake Tuesday afternoon and night. Small Crafts will be needed
elsewhere and will continue on the east half of the lake through
Wednesday.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Winter Storm Watch from Monday evening through Wednesday
     afternoon for OHZ013-014.
PA...Winter Storm Watch from Monday evening through Wednesday
     afternoon for PAZ002-003.
     Winter Weather Advisory until 7 AM EST Monday for PAZ001-002.
MARINE...Small Craft Advisory until 4 AM EST Monday for LEZ145>149.

&&

$$
SYNOPSIS...Oudeman
NEAR TERM...Mullen/Oudeman
SHORT TERM...KEC
LONG TERM...Adams
AVIATION...Mullen
MARINE...KEC



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