Area Forecast Discussion
Issued by NWS Cleveland, OH

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FXUS61 KCLE 140556
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
1256 AM EST Thu Dec 14 2017

.SYNOPSIS...
An Alberta Clipper storm system will move southeast across the
area tonight. The low will then move east of the area Thursday.
A weak ridge of high pressure will build east across the area
from the west Thursday afternoon into Thursday night. A cold
front is expected to move east across the area Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Let the advisory across the west end as snow tapers of
quickly.

Original discussion...
Messy forecast in place for the next 36 hours. An Alberta
Clipper storm system is progged to move southeast across the
forecast area tonight. The system is moving at a fairly good
clip at this time but as it rounds the base of the upper level
trough, the system will slow in forward motion tonight. An upper
level positive vorticity maximum will coincide with the low
pressure system and enhance upward vertical motion. A fair
amount of moisture is associated with the storm system as it
moves into the region. The first round of snow that moved across
the area produced some good snow bursts with larger flakes. This
is in line with the best dendritic snow growth area moving into
the forecast area at this time and is expected to hang around
through much of the night. Best forcing appears it will lie
along an axis from the eastern Lake Erie islands to between
Cleveland and Erie, PA to Youngstown. Latest radar shows first
swath moving into the eastern portions of the forecast area now
and all indications are that the snow will expand again over the
west and fill back in and continue through the night as low
moves into the region. Decided to up QPF amounts a tad and this
will take snow accumulations up to around 6 inches over the
eastern third of the forecast area. So, will hoist the winter
storm warning for this area overnight and will take it to 1 PM
tomorrow. Snow should start to taper off in the morning in the
east. Over the rest of the area will see winter weather advisory
criteria of 3 to 5 inches of snow overnight but 2 to 4 inches
across the extreme southern tier. Snow accumulations based on
temperatures in the upper teens in the east and 20s over the
rest of the area. Cold air temperatures will produce light
fluffy snow so it should accumulate at a faster rate. Winds will
aid in blowing of the snow so measuring will likely be a bit
difficult tomorrow morning.

Snow pulls out to the east and transitions into a lake effect
snow as flow becomes northwest and multibands develop. Expecting
light accumulations tomorrow as bands gradually shift back
northeast up the lake bringing an end to the lake effect. Flow
will shift to a mean southwest direction in advance of the next
cold front that will approach the area.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Friday will start off dry as a ridge of high pressure slides off to
the east. As we head into Friday afternoon a clipper will move east
across the northern Great Lakes. This will keep the brunt of the
snow north of the area, but it looks like some snow should be able
to affect northern areas as the cold front sags into the area. Not
expecting much in the way of accumulation through Friday evening,
maybe an inch or so with be best chances across the Snowbelt.

Winds turn around to the west-northwest Friday night behind the cold
front and this will trigger lake-effect snow. There may be enough
snow to trigger an advisory or possibly even a warning across
northwest PA.

Snow will begin to taper off Saturday as winds turn back around to
the south in response to a weak surface ridge moving through. Dry
weather is expected Saturday night through the first part of Sunday
as an upper level ridge moves overhead. This will help to warm
temperatures up into the lower 30s Saturday and perhaps near 40
degrees in spots by Sunday.

Models differ considerably the second half of Sunday as a weak area
of low pressure tries to move in from the southwest. There will be a
chance of rain showers (possibly mixed with snow) if this is able to
hold together and make it to our area.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Have made wholesale changes again today as the guidance continues to
show little run to run continuity.  The area may experience some
light warm air advection precip Sunday night into Monday.  The ECMWF
brings a weak low across the area on Monday.  Meanwhile the GFS
shows weak ridging.  The model differences continue Tuesday and
Wednesday as well so confidence is very very low today. Both models
show a cold frontal passage toward the end of the period.  As a
result of the timing differences will continue to broad brush the
forecast with precip chances just about every period. Temps will get
back close to normal so we could have precip type issues during the
daylight hours but mainly snow at night.  No big events are expected
at this time. Will keep some lake effect in for Wednesday downwind
of the lake otherwise will try to dry things out.

&&

.AVIATION /06Z Thursday THROUGH Monday/...
Low pressure was located just to the south of Cleveland and
will continue to move eastward through the overnight. The
trailing cold front as of 0530Z was located from Sandusky to
Mount Vernon. All the IFR snowfall was generally located from
the Central Highlands to western PA. Expect this area of snow to
quickly move eastward through 12Z with MVFR ceilings in its
wake. Will have to monitor for some lake effect snow in the wake
of the low but confidence in this developing is low. Ceilings
will improve through the day with all locations becoming low
end VFR by evening.

Winds are south to southeast ahead of the low but quickly snap
around to the north and northwest in its wake. Ther have been
some stronger wind gusts across from Findlay to Mansfield but
believe these gusts to 35 knots will quickly move eastward and
should only impact KCAK through about 08z. Winds will decrease
through the afternoon then gradually shift to the west.

OUTLOOK...MVFR possible Friday and Friday night across the area
and again Sunday night into Monday in wintry precipitation.

&&

.MARINE...
Southerly winds around 10 to 15 knots will continue into this
evening. Winds pick back up on the back side of a surface low
tonight as they turn out of the north. Small Craft Advisory
conditions will be marginal, but have gone ahead and issued Small
Craft Advisories for the western and central parts of the lake from
tonight into tomorrow morning. Winds should be up around 20 to 25
knots across the Western Basin. Across the central part of the lake
winds will be around 20 knots with waves near 4 feet. SCA will need
to be considered for the eastern end of the lake, but will defer to
later shifts. Winds will gradually diminish Thursday as high
pressure nudges into the Ohio Valley. Southwest winds will be on the
increase Friday. Winds turn to the west-northwest Friday night and
further intensify. Small Craft Advisories will be needed.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Winter Storm Warning until 1 PM EST this afternoon for
     OHZ011>014-022-023-033-089.
     Winter Weather Advisory until 10 AM EST this morning for
     OHZ010-020-021-029>032.
PA...Winter Storm Warning until 1 PM EST this afternoon for
     PAZ001>003.
MARINE...Small Craft Advisory until 7 AM EST this morning for
     LEZ142>144.
     Small Craft Advisory until 1 PM EST this afternoon for
     LEZ145>147.

&&

$$
SYNOPSIS...Lombardy
NEAR TERM...Greenawalt/Lombardy/Mullen
SHORT TERM...Mottice
LONG TERM...Kubina
AVIATION...Mullen
MARINE...Mottice



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