Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Cleveland Ohio
128 am EDT Sat Aug 30 2014
as the surface high over New York moves east it will allow an area
of low pressure over the northern plains to move into the Great
Lakes. As it approaches the local area we will see an increase in
clouds and storm activity starting from west to east late
Saturday. Another low pressure system will move over the lakes
region Monday night.
Near term /until 6 am this morning/...
added a threat of showers to the western portion of the forecast
area as per the radar. It should decrease. Elsewhere partly cloudy
should be OK. Made minor adjustments to some of the lows.
Short term /6 am this morning through Monday night/...
a disturbance from the west will approach the region on Saturday.
The best chance for convection will be in the afternoon...but
could see some stray storms in the far west before noon. Focus
for the greatest coverage will be over the western half of the
forecast area where moisture and instability will be greater. The
models are suggesting some moisture will become available in the
far eastern counties as it wraps around the backside of the surface
high..but not convinced this will be enough when combined with a
weak cap to generate storms for the first half of the day. There
is some suggestion that there will be a dry slot between the two
systems keeping plenty of sunshine and dry conditions over the
eastern 2/3rds of the County Warning Area. Temperatures will be able to climb into
the middle/upper 80s across the region...well above the upper 70
normals for this time of year. This combined with high dew points
will make heat index values in the upper 80s to near 90. The jet
dynamics become favorable later in the afternoon and gradually
improves east into the evening hours with increased forcing and
plentiful moisture. With the upper trough passing over the area
Sunday we will see a lowering of probability of precipitation from northwest with reduced
forcing. The rain chances will linger for the better part of the
day over the southeast counties...where the main threat will be
the heavy rain with precipitable water values around 1.8". Probability of precipitation Sunday night will
drop and there will be a period without storms through the first
half of Labor Day. The second upper trough will move into the area
from the plains Monday night. In advance of this system we could
see some scattered storms.
Long term /Tuesday through Friday/...
jet stream continues to track zonally across the northern tier
states taking a system across the Great Lakes Tuesday. This front
will make little southern progress likely dissipating over the Ohio
Valley. Surface high pressure weakly in control Wednesday and
Thursday. Another system will be on deck for Friday. Overall decent
model agreement...but with the zonal flow timing may be off this far
out. Centered precipitation chances around frontal zones. Temperatures will
run near normal.
Aviation /06z Saturday through Wednesday/...
upper level ridge still in place over the forecast area at this
time. A lone shower moved north but remained just east of the
Toledo and Findlay taf sites. Expecting a possibility for showers
and thunderstorms this afternoon over the western portions of the
region. Latest hrrr model is showing a threat for an isolated
shower to move northeast along the Lake Shore from Cleveland to
Erie early this afternoon. But will leave things dry at Erie at
this point since it will be so widely scattered if it occurs.
Otherwise dry for the rest of the taf sites. Winds will be on the
increase later tonight from the south as well. Earlier forecast
mentioned some wind shear. Latest guidance now suggests winds will
gradually increase from 10 knots at the surface to 40 knots at
2000 feet so not expecting wind shear at this time.
Outlook...non VFR likely in showers and thunderstorms Saturday
through Tuesday at times.
thunderstorms and a choppy lake Saturday night/Sunday are the main
concerns for the marine forecast. As high pressure shifts east
tonight winds on the lake will become southerly for Saturday...and
then south-southwest for Saturday night. There is a little bit of
wind forecast for Saturday night into Sunday...with speeds of 10 to
20 knots on the lake. This will result in a choppy lake...with the
possibility of needing a Small Craft Advisory. Thunderstorm chances
are focused primarily on Saturday evening and Saturday
night...clearing out on Sunday. A cold front never really crosses
the lake this weekend...but instead weakens overhead. Lighter
southwest flow continues Sunday and Monday. A cold front that should
cross the lake arrives for Tuesday.