Area Forecast Discussion
Issued by NWS Cleveland, OH

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000
FXUS61 KCLE 181539
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
1139 AM EDT Fri Aug 18 2017

.SYNOPSIS...
A cold front will cross the area this morning. High pressure will
slide across the Ohio Valley this afternoon into tonight. Weak low
pressure associated with a strong short wave will drop across the
lower Great Lakes and Ohio Valley on Saturday. High pressure will
build across the Great Lakes Sunday, then move east of the area on
Monday.

&&

.NEAR TERM /THROUGH SATURDAY/...
Update...Low level moisture continues to rotate ese out of MI
into nwrn Ohio this afternoon. Low level cu also expanding ahead
of this with the late morning sunshine. Have increased clouds in
grids across northwest and north central Ohio through the
afternoon. Still came out of "partly sunny" in text forecast but
there should be a few breaks ahead of some thinning later this
afternoon and evening. No other big changes.

Original "Near term" discussion...
The front is still to the west and will cross the area this
morning. Cannot totally rule out a shower, especially across
northeast OH and northwest PA where there is deeper moisture,
but will only mention a slight chance for northwest PA. There is
a somewhat better opportunity for a shower there as in addition
to the front, a weak trough will cross eastern Lake Erie and NW
PA later today. Stratus will develop across parts of northeast
OH and northwest PA this morning and stratocumulus will follow
the front this morning so it will become mostly cloudy to partly
cloudy in most areas for a while, then skies will slowly clear
as drier air and mixing increases this afternoon. It will start
out humid this morning but as mixing increases today, the drier
air will filter in.

Highs temperatures are tricky. It will start out warm this morning
but cold advection will increase. Loaded the model H8 temperatures
adiabatically and it gave mostly lower 80s for highs. A few spots
could sneak into the mid 80s.

Skies should be clear/mostly clear for a while tonight and dew
points will finally be down. Lows will not get as cool as they could
since clouds will increase ahead of a fairly strong short wave
diving across the lower Great Lakes for Saturday. The boundary
layer will be dry and stable but with enough upward motion, there
will be showers. The models generate some CAPE, especially the
NAM, and will include the mention of thunder. The better chance for
thunder might be farther south where the air mass remains more
unstable but given the track of the vort center, will include the
mention of thunder. Will keep the pops in the 40-50 percent range
given the uncertainties on the system but folks with outdoor plans on
Saturday may face a period of showers. Forecast temperatures will be
in the mid/upper 70s with the clouds/shower threat except around 80
northwest OH where the sun may come back out in the afternoon.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
Other than a lingering shower across the east early Saturday night,
the weather will be quiet with high pressure building overhead for
the remainder of the weekend and through Monday. Temperatures will
recover several degrees for Sunday. Kept temperatures in the 80s and
under the 90 degree mark for the I-75 corridor for Monday with a
mostly sunny/partially eclipsed sky.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
Differences for the Tuesday system do not translate in to too many
changes to the sensible weather forecast. Have increased precip
chances to 60 percent, but shifted them in time to straddle 00Z Wed
with the broader trough lagging some from yesterdays runs. After
highs in the mid 80s Tuesday, the passage of the cold front and the
arrival of Canadian high pressure southward across the Great Lakes
puts us back into the 70s for highs Wednesday and Thursday. Will
likely suffer from lake generated/enhanced cloud cover going into
mid week.  A second push of colder air Thursday and the possibility
of some moisture with the trough may be enough to produce some
showers from northern OH into nw PA.

&&

.AVIATION /12Z Friday THROUGH Tuesday/...
Patchy IFR stratus was occurring across northeast OH and
northwest PA ahead of a weak cold front. Cannot rule out a
shower as the front crosses the area this morning but kept the
TAF forecasts dry given the isolated nature of any shower
development. MVFR stratocumulus will likely develop behind the
front for a while this morning into early afternoon. Winds will
become gusty from the West today. Skies will clear for a while
by early tonight (Friday night). Another weak low pressure
system will approach by Saturday morning and showers may develop
at KTOL and KFDY before 12Z Saturday.

OUTLOOK...Areas of Non-VFR possible in showers Saturday and
again on Tuesday.

&&

.MARINE...
Hoisted a small craft advisory for Avon Point eastward for midday
through this evening. West-southwest flow will pick up and shift
more westerly late in the afternoon. Waves are expected to build by
or shortly after midday to 3 to 6 feet. This is as low pressure
pulls away from the northern lakes and into Canada and high pressure
builds across the lower Ohio Valley.  The east end of the lake will
be choppy again Saturday before high pressure can build more firmly
over the lake.  It may be close to small craft advisory conditions
for a time Saturday. By Tuesday southwest flow can be expected on
the lake as the next system approaches.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Beach Hazards Statement through late tonight for OHZ011-012-
     089.
PA...Beach Hazards Statement through late tonight for PAZ001.
MARINE...Small Craft Advisory until 4 AM EDT Saturday for LEZ146>149.

&&

$$
SYNOPSIS...Kosarik
NEAR TERM...TK/Kosarik
SHORT TERM...Oudeman
LONG TERM...Oudeman
AVIATION...Kosarik
MARINE...Oudeman



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