Area Forecast Discussion
Issued by NWS Cleveland, OH

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818
FXUS61 KCLE 090239
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
939 PM EST Fri Dec 8 2017

.SYNOPSIS...
Low pressure developing over northern Minnesota will move east and
pull a cold front across the southern Great lakes on Saturday. A
ridge will expand into the Ohio Valley on Sunday. Another low
pressure system will track from near Chicago across Lake Erie on
Monday night, pulling another shot of arctic air across the
region on Tuesday.

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
Only minor changes have been made to reflect current trends.

Previous Discussion...
Dry air and mostly clear skies will be in place across the area
this evening. Cirrus streaming up the east side of the upper
trough will depart to the east with time. Winds will relax some
this evening but not enough to reach MOS guidance lows again for
a second day in a row. Went with a blend of raw models and MAV
guidance which was a few degrees warmer with lows ranging from
the upper teens inland to near 20 along the lakeshore.

A deep upper trough remains in place across eastern North America
with a piece of energy seen on water vapor diving south across
Minnesota. At the surface, low pressure developing across
northern Minnesota will move across southern Lake Michigan, then
slide east across the central and eastern Great Lakes Saturday
into Saturday night. Snow is expected to spread east across the
area Saturday into Saturday night as lift ramps up ahead of the
deepening trough. Dry air in the low levels will be slow to
overcome and have delayed the onset of precipitation. Expecting
most areas to see some snow with areas outside of the snowbelt
receiving around an inch or snow. Eastern areas will be a few
degrees warmer on Saturday with some filtered sun in the morning
and a slower onset of precipitation.

A low level trough will develop over Lake Erie with increasing
convergence as the surface low passes north of the lake.
Moisture off the lake will enhance snow showers which will
eventually come onshore Saturday night as the trough pulls away
and the flow shifts onshore. Steep low level lapse rates and
moisture through nearly 13000 feet will combine with favorable
lift as the trough swings through to result in a healthy window
of snow showers. The duration will be fairly short but expecting
good intensity with snowfall across the snowbelt ranging from
an inch along the lakeshore to 3 to 5 inches of snow across the
favored upslope area. The duration will be short lived as drier
air will be starting to overspread the lake by 09-10Z with snow
decreasing from west to east late Saturday night. Will have to
monitor for any areas of convergence as the flow starts to back
late Saturday night but this occurs during the window of lower
moisture so not thinking any heavy bands will develop. Winter
Weather Advisories may be needed for a portion of the snowbelt
for Saturday night into early Sunday.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Weak ridging at the surface should set up on Sun over the Oh Valley
with winds backing from west to southwest. This should cause the
lake effect snow bands to shift northeast to mainly just be
affecting Erie co PA. Since lake effect conditions are only
marginal, will keep accumulation mostly to 2 inches or less.

A dissipating surface trough is expected to drop southeast into the
snowbelt early Sun night which should shift winds more toward the
west and help provide a focus to increase the snow bands while also
pushing them further inland across the snowbelt.

The next clipper and reinforcing shot of arctic air is on track to
drop southeast thru the region Mon and Mon night. This will lead to
another batch of fairly widespread snow that will transition back to
mainly just lake effect on Tue. Winds on Tue will come around more
toward the north so the lake effect bands will be affecting the CLE,
CAK and YNG areas more this time. Temps a little below normal on Mon
will return to well below normal for Tue as the arctic air spreads
in.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Cold and snowy pattern will continue through the long term period
next week. Upper trough will remain entrenched across the Great
Lakes region through at least Friday, with below normal
temperatures. Some sort of lake effect will be prevalent through
most of the period across far NE OH and NW PA, but the extent/exact
characteristics of the snow are still a few days out from being
resolved. Several shortwaves/surface lows will swing through the
region in a northwest flow regime, which will bring periodic snow
chances to areas outside of the primary snowbelt as well. However
many timing/track differences remain between the models, so only
chance pops warranted at this point from the Wednesday through
Friday time frame. Highs will generally be in the upper 20s/low 30s
through the period, with lows in the teens/20s. However the coldest
period looks to be Tuesday night through Wednesday as a stronger
shot of Arctic air pushes across the Great Lakes, with a bit of a
moderating trend Thursday through Friday.

&&

.AVIATION /00Z Saturday THROUGH Wednesday/...
VFR conditions expected through Saturday morning. Ceilings will
lower late morning through the afternoon as a weakening area of
low pressure moves into the area. Areas of snow will develop
ahead of the low with IFR conditions spreading from west to east
across the region.

Southwest winds at 10 to 15 knots expected into Saturday. Winds
become westerly by late in the day and eventually to the
northwest by Saturday night.

OUTLOOK...Non-VFR persisting downwind of Lake Erie into Sunday
morning. Another clipper storm system will likely cause non-
VFR conditions in snow Monday into Tuesday.

&&

.MARINE...
Winds have decreased enough to allow the small craft advisory to
be cancelled for the remainder of the night. However in the
wake of the clipper on Saturday a small craft advisory will
likely be needed and then prevail most of the time thru next
Wednesday. When SCA level winds are occurring from the WSW there
may be near low water conditions on the west end of the lake.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.

&&

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



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