Area Forecast Discussion
Issued by NWS Cleveland, OH

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198
FXUS61 KCLE 022307
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
607 PM EST Fri Dec 2 2016

.SYNOPSIS...
Low pressure across the eastern Great Lakes will shift to the east
coast tonight allowing high pressure to begin building in from the
southwest. The high will move over the local area Saturday night
and move to the east coast on Sunday. A weak warm front will lift
north across the area Sunday night with another high briefly
building in on Monday.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
No major changes to the previous forecast. As the winds have
turned to the northwest a couple of lake-effect bands have now
shifted inland and continue to slowly dissipate across northeast
Ohio. Additional lake-effect showers will develop over the next
couple of hours across the Snow Belt, with northwest PA seeing the
brunt of the precipitation. With a combination of warm air
advection and a lowering inversion, we will only see up to about 3
inches in the higher terrain of northwest PA with a rain/snow mix
possible along the lake shore.

Original discussion...The surface trough has inched it`s way
south across most of Lake Erie and appears to be located just
north of the lakeshore. The northwest winds behind this trough are
pushing the lake effect bands inland where they should weaken and
die. More activity will develop in the northwest flow tonight with
the brunt of the activity over NW PA where there could possibly be
a brief Lake Huron connection. With that said temps aloft are not
very cold and BUFKIT shows a lowering inversion the second half of
the night. We will also be seeing warm air advection at 850 mb
from the northwest overnight. Expect temps at 850 mb to moderate a
couple of degrees overnight. Also seeing some directional shear in
the lower 5000 feet which is especially detrimental in NW flow
regimes. So although some lake effect is expected...accums will be
no more than 2 or 3 inches even on the higher terrain. Closer to
the lake rain or mixed precip are possible. Have trimmed back the
precip mention to the west and south of the snowbelt. Places like
CLE will see no more than a burst of snow or two and no
accumulation. Earlier forecast had the clouds diminishing in the
west but given the amount of low level moisture and an inversion
at 4k feet or less it will be tough to get more than a few breaks
overnight. This means guidance temps which are expecting clearing
are probably too low. Have only had reports of snow on grassy
surfaces this afternoon but that will change after sundown.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY NIGHT/...
The lake effect will continue through Saturday night but will
really begin to taper the precip off from west to east on
Saturday as the inversion lowers. By 00z Sunday the snow showers
should be confined mainly to NW PA. After daybreak Saturday accums
will be localized with no more than another inch or two any given
location. The surface ridge will move through early Sunday and we
should be able to squeak out a dry morning. A warm front will
lift across the area later in the day and bring with another
period of precip. Temps and low level thicknesses may remain cold
enough for most of the precip to start as snow or mixed precip.
The precip could stay mostly snow in the north but the models warm
the southern half of the area enough for a change to rain.
Fortunately QPF amounts will be less than a tenth of an inch with
the precip generally lasting for a period of 6 to 9 hours most
areas. Another high will scoot east across the area on Monday
keeping the area dry. Big model differences begin to take shape at
the every end of the short term period. Lot`s of uncertainty about
precip early Tuesday and will let later shifts take a look at
that. Have used a blend of guidance for temps.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Potentially big changes coming up in the extended periods.  Another
deep digging upper level trough will rotate south into the western
United States and then push east across the rest of the country.
This feature has the potential to bring some of the coldest air of
the season to the forecast area by the middle to latter part of next
week.  The big caution is the timing of the arrival of the cold air
mass.  The European model suggests a deep diving panhandle hook low
pressure system will move east across the Ohio Valley allowing the
arctic air to plunge southeast into the area Thursday night.
Whereas, the GFS model suggests surface low pressure will develop
and then strengthen over the delta region of the Gulf of Mexico by
Tuesday afternoon and track northeast across the Ohio Valley.  This
track will allow the arctic air to arrive Wednesday night.  The
thinking is to come up with a solution some where in the middle of
the two models until a better agreement in timing is achieved.

Temperatures at 850 MB are expected to drop to between -16 C and -18
C by Thursday evening.  This will set-up extreme instability over
the lake.  Not only that, wrap around moisture will slide south
across the area from the surface trough Thursday night.  The
combination of the arctic air and available moisture in concert with
the lake moisture, there is the possibility for another significant
lake effect snow event in the northeast snowbelt if all of these
ingredients come together. A big caution is if the air mass remains
as cold as the models suggest and does not modify considerably with
time over the lakes. And, this all depends on where the winds setup
for lake effect bands to develop. There has been some consistency in
the models over the last few days that the event can occur.

For the entire area, the question remains as to how cold it will get
during the peak of the cold air mass.  Highs may not get out of the
20s by Friday and overnight lows in the teens Friday and Saturday
mornings.

&&

.AVIATION /00Z Saturday THROUGH Wednesday/...
Marginal lake effect conditions will continue thru saturday but any
rain or snow showers should mostly just affect eri, especially
after 06z tonight. Mix of vfr and mvfr cigs should lower some
late tonight into sat morning but should still stay mostly mvfr
except may higher end ifr at yng. A little improvement in cigs by
late sat afternoon.

OUTLOOK...Mostly mvfr cigs much of the time thru wed with areas of
rain and snow.

&&

.MARINE...
Small craft advisory will remain in effect through the evening in
the west and through tomorrow morning over the rest of the lake.
Winds will remain between 15 and 25 knots on the lake through the
night and this will keep the waves up as well.  Winds finally start
to diminish Saturday and continue through Sunday as high pressure
builds across the area. Generally light flow is expected across the
lake Monday and then begins to increase out of the southeast by
Tuesday well in advance of the next storm system. As low pressure
moves northeast across the area, winds diminish again on Wednesday.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...Small Craft Advisory until 10 AM EST Saturday for LEZ145>149.
     Small Craft Advisory until 10 PM EST this evening for
     LEZ142>144.

&&

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



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