Area Forecast Discussion
Issued by NWS Cleveland, OH

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000
FXUS61 KCLE 100345
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
1045 PM EST Fri Dec 9 2016

.SYNOPSIS...
Cold northwesterly winds will continue to flow across Lake Erie
and produce Lake Effect Snow for the snowbelt tonight. As high
pressure begins to ridge into southern Ohio tonight into Saturday
it will nudge the snow showers up the lakeshore into NW PA. The
area of high pressure will be short lived with the next storm
system moving from the southern Plains into the central Great
Lakes Sunday into Sunday night.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Despite some movement and disruption of the heavy band over the
last 2 hours, the heaviest snowfall remains where it has been most
of the day from northeast Cuyahoga County eastward into southern
Lake/Northern Geauga and Ashtabula Counties. Surface winds clearly
show this area of convergence with southwesterly winds on land while
observations along the lakeshore are out of the northwest. The
surface trough is expected to strengthen along the eastern
lakeshore overnight with a gradual trend for bands to shift
northeast late tonight into Saturday. Models do show some drying
near 700mb spreading in from the west overnight but also show
some large scale ascent towards morning ahead of an approaching
shortwave. Overall expect to see bands strengthen as they shift
north into Lake County in the morning and eventually along the
Erie Pa lakeshore Saturday afternoon. If bands do set up in Erie
County as expected on Saturday, then the Warning may need to be
extended through Saturday evening.

Previous discussion...Hi-res guidance has been generally poor
with handling the dominant bands coming onshore between Euclid and
Willoughby and in Ashtabula county. The southwest band has moved
little despite hi-res guidance trending the band southward into
eastern Cuyahoga through the afternoon. Snowfall reports have been
exceptional with this band, with 1-2" per hour rates with thunder
snow being reported. Have upped snowfall amounts through 7 PM
considerably from Euclid/Willoughby southeast to
Chesterland/Chardon. This also prompted an upgrade to a Lake
Effect Snow Warning for Cuyahoga and Trumbull counties, given
reports quickly approaching criteria and additional snowfall
expected. Expect this band to continue for the next few hours and
move very little, perhaps only diminishing in organization and
intensity a little bit.

Still expecting snow to increase further southwest into Cuyahoga,
including downtown Cleveland, through 7 PM and after. Models
continue to show favorable trajectories from Lake Michigan bands,
and organization of these bands further west along the lake. Latest
radar trends are possibly showing a main band organizing along the
western basin. Overall, expecting two main bands oriented mainly
west/east impacting northern Cuyahoga inland and northwest Ashtabula
inland to NW PA. Current thinking is that the further southwest band
will become more disorganized towards 04-06Z, with the further
northeast band staying more organized a bit longer. Trended pops and
snowfall amounts around this idea, which is fairly similar to
previous forecast. General snowfall amounts overnight are forecasted
in the 3 to 5 inch range in NW PA and Cuyahoga/Lake/Geauga, but
wouldn`t be surprised to see higher/lower amounts where the bands
persist/miss, and overall variable accumulations.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY NIGHT/...
Dominant lake band will be reorienting along the lakeshore and
lifting northeast during the day Saturday as 925mb flow backs
southwest into the afternoon hours. The band should still be rather
impressive with thermodynamically favorable environment, impressive
lapse rates, ample boundary layer moisture and modest shear/flow.
Trended the band up along the lakeshore through the day, with pops
diminishing from southwest to northeast. Snow amounts during the day
Saturday not changed too much from previous forecast, with general 2
to 5 inch amounts, with possible higher amounts in NW PA where bands
persist with 1"+ per hour rates.

The last of the lake effect will shift east early Saturday night as
ridging increases and the flow becomes southwest. An expansive area
of warm advection will be underway across the midwest as a lead
short wave tracks east in a relatively fast jet aloft. High clouds
will already be increasing across northwest Ohio by sunset Saturday
evening and some light snow will develop later Saturday night from
west to east as the low level jet increases across the midwest.

The system will probably be rather complex by Sunday. Heights aloft
will be trying to rise. The initial surge of warm advection snow
might try to taper off but will not bet the house on it since the
low level jet will continue to increase and eventually some gulf
moisture will begin to sneak in from the southwest. We will likely
see a general 1 to 3 inch snowfall from late Saturday night into
Sunday afternoon, perhaps locally 4 inches across northwest or north
central Ohio.

The next surge of precipitation will develop in advance of the main
trough by Sunday evening. Surface temperatures and precipitation
type will be problematic as we continue to warm through the column.
Snow will likely mix with and change to rain in much of the area
Sunday night as the surface low tracks across the Great Lakes and
the south flow continues. A little sleet and a period of freezing
rain is possible during the transition. Do not have a good estimate
on the timing and duration of the snow and potential freezing rain.
I could even see thunder Sunday night ahead of the cold front.

A winter storm watch will likely be needed for the time period from
late Saturday night into Sunday night for at least part of the area.
Highs on Sunday will probably approach freezing, then temperatures
will rise Sunday night.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Models not in good agreement on the timing of the next systems
overall...but the trend is definitely the same.  Setting up for the
coldest temps of the new season as an arctic front blasts through on
Wednesday.   ECMWF a little faster with the front than the GFS but
either way by daybreak Thursday 850mb temps plunge to -20c and by
Thursday evening -24c.   Expect highs in the teens and lows in the
single digits on Thursday.  Best chance of snow with the system will
be in the snowbelt.  The cold lingers through the end of the work
week.   ECMWF builds high over the area on Friday while the GFS
about a day slower...so superblended Friday.

&&

.AVIATION /00Z Saturday THROUGH Wednesday/...
Lake effect still going strong in the northeast portions near the
lake with intense band just north of Cleveland into northeast
Ohio. Main band is slowly lifting north through the night and
should be oriented west to east across the lakeshore area. A band
will slip into the CLE terminal area for a few hours this evening.
Another band will develop into Erie, especially toward morning.
Rest of the terminals will see improving conditions as flow shifts
around to the southwest tomorrow and this should bring an end to
the lake effect snow for the time being. Winds will be strongest
10 to 20 knots near the lake and around 10 knots elsewhere.

OUTLOOK...Lake effect shsn mainly for Eri Saturday into Saturday
night. Widespread light to moderate synoptic snow Sunday into
Monday for the entire forecast area.  Lake effect snow will
continue in the snowbelt east of CLE into Tuesday.

&&

.MARINE...
Have let the small craft advisory expire on the Western Basin as the
winds have diminished to 10 to 20 knots.   Conditions will remain
choppy with 2 to 4 foot waves.   Small craft will continue over the
Eastern 2/3 or the lake with a west flow of 15 to 20 knots.  SCA
ends late Saturday as high pressure moves quickly across the lower
lakes and the winds turn to the south.   Small craft likely needed
again on Monday as another system moves across the Great Lakes.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Lake Effect Snow Warning until 4 PM EST Saturday for
     OHZ012>014-089.
     Lake Effect Snow Warning until 10 AM EST Saturday for OHZ011.
     Lake Effect Snow Warning until 7 AM EST Saturday for OHZ023.
PA...Lake Effect Snow Warning until 4 PM EST Saturday for
     PAZ001>003.
MARINE...Small Craft Advisory until 4 PM EST Saturday for LEZ146>149.

&&

$$
SYNOPSIS...Greenawalt
NEAR TERM...KEC/Greenawalt
SHORT TERM...Greenawalt/Kosarik
LONG TERM...DJB
AVIATION...Lombardy
MARINE...DJB


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