Area Forecast Discussion
Issued by NWS Cleveland, OH

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541
FXUS61 KCLE 100859
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
359 AM EST Sun Dec 10 2017

.SYNOPSIS...
An upper level trough will remain across the eastern United States
for much of the week. At the surface, a cold front will move
east of the area today. A secondary trough will slide south
across the Eastern Great Lakes tonight, followed by an area of
low pressure crossing the Great Lakes region Monday night into
Tuesday.

&&

.NEAR TERM /THROUGH MONDAY/...
Lake effect snow has begun across the Snowbelt in a more or less
disorganized fashion. Some embedded bands of heavier snow can
be seen on radar across portions of Lake, Geauga, and Ashtabula
Counties. Look for generally 1 to 3 inches of additional snow
across northeast Ohio through the morning hours. Snow will fill
in over the next couple hours across northwest PA and similar
totals can be expected through midday today.

As we head into this afternoon the flow will become southwest
and a lake-effect snow band will organize, but is expected to
remain largely just off shore initially. However, if there is
even a 10 or 20 degree difference in the forecast wind direction
portions of northeast Erie County PA could be affected by this
band this afternoon. This is something we will have to watch
closely.

This band will crash back on shore tonight as an upper level
short-wave and surface trough pass by and veers winds back
around to the west. This is expected to produce generally
another 2 to 4 inches across Erie County, but it will all
depend on just how quickly this band moves inland. This band may
reach as far west as the Cleveland area with amounts of around 1
to 3 inches possible in the Primary Snowbelt in northeast Ohio. Locally
higher totals will be possible in favored upslope areas, especially
if the bands moves on the slower side. The Winter Weather
Advisory continues through tonight for Erie County PA.

The lake-effect snow will taper off Monday as a weak ridge of
high pressure at the surface nudges north into the area and
backs winds to the southwest and eventually south. Temperatures
will rise to near 30 degrees this afternoon, falling back into
the lower and middle 20s tonight. Temperatures Monday afternoon
will be slightly warmer than what we see today.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
The short term begins Monday night with both the NAM and GFS showing
low pressure moving through the central lakes reaching sern
Ontario/Lake Ontario region by 12z Tuesday. This system will spread
a general synoptic snow across the area with the most (~ 2-4 inches)
falling north/northeast. As the low moves east of the area Tuesday
it will drag a Canadian/Arctic cold front through (late Monday night
and early Tuesday). This cold northwest flow will begin an
extended period of lake effect snow that will last into
Wednesday. BUFKIT shows extreme instability to the lake, good
dendrite growth, deep lift and ample moisture for lake effect
snow. There are negatives, however. Much of the time winds will
be from around 300 degrees which is a short fetch across the
lake. Also boundary layer wind speeds will be around 40kts so
latency will be compromised. At this time would expect a
multiband setup with help needed from shoreline convergence and
orographic lift. Tuesday and Tuesday night have a combined 6 to
8 inches in grids. Wednesday another 1 to 3 mostly in the
morning as dry air will be moving in. All told expect up
to/around a foot inland nwrn PA and 6 to 10 northern Geauga.

Will issue a winter storm watch for lake effect snow from Monday
night through Wednesday afternoon for Geauga, inland Ashtabula,
inland Erie, and Crawford counties. Given the onshore flow direction
expected believe the heaviest amounts will be away from the
lakeshore unlike the previous event.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
Thursday into Friday models have another clipper system dropping
down in the northwest flow across the western to the central lakes.
Models are a bit different with the ECMWF keeping much of the precip
north of the region while the GFS brings it across the area. For now
seems reasonable to have clouds and a chance of snow showers given
the pattern. Saturday models back in agreement showing low pressure
moving east MN/WI region with large scale warm advection into the OH
Valley. For now models are mostly dry so will have a dry day.

&&

.AVIATION /06Z Sunday THROUGH Thursday/...
Lake effect snow is developing and will impact sites mainly east
of KCLE. Expect IFR conditions in these snow bands. Some low
end VFR is possible across northwest Ohio overnight, otherwise
widespread MVFR is expected. A trend of lifting ceilings will
occur across all inland sites later today. However, lake effect
snow will be close to the lakeshore from KCLE to KERI with KERI
being impacted through the day. A band of potentially heavy lake
effect snow will move back onshore tonight impacting KCLE and
KERI.

OUTLOOK...Non-VFR likely Monday night, and Tuesday night area
wide. Non-VFR continuing across northeast OH/northwest PA for
most of the time through Wednesday night.

&&

.MARINE...
Will continue small craft advisory as is. Expect winds to increase
this afternoon to 15 to 25 knots as low pressure moves east through
the central lakes. Winds will slowly diminish overnight turning more
northwest. Winds and waves will increase again late Monday night in
the wake of deepening low pressure. Tuesday winds will increase
from the northwest to 30 knots and diminish slowly Tuesday
night and Wednesday and likely requiring a small craft advisory
from late Monday night through Wednesday night.

&&

.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...Mottice
NEAR TERM...Mottice
SHORT TERM...TK
LONG TERM...TK
AVIATION...Mottice
MARINE...TK



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