Scientific Forecaster Discussion
fxus61 kcle 290139
Area forecast discussion
National Weather Service Cleveland Ohio
939 PM EDT Wed Jun 28 2017
high pressure will continue to move east of the area and off the
East Coast tonight. This will allow a low to cut northeast
across the central Great Lakes bringing a weak warm front
northeast across the area Thursday. A boundary will be present
Thursday and Friday, which will become the focus of convection.
Near term /through Thursday night/...
a few sprinkles continue to move across Lake Erie toward western
New York. Since there should not be more than a couple drops under
them we will not mention them in the forecast. Attention has
been drawn to the convection moving across Lake Michigan.
However it should weaken as it drifts eastward into some drier
air. The sprinkles and eventually the blow off from the central
Great Lakes convection will keep a few more clouds over the area
than expected. Since there is a bit more cloud cover we have
nudged highs up a degree or two.
a difficult forecast with greater than normal uncertainty is in
store for the near term. Dry weather will continue through
tonight and into Thursday morning as a ridge of high pressure
moves off the eastern Seaboard. A weak warm front will lift
northeast across the area Thursday morning as a surface low cuts
northeast across the Great Lakes. It appears there will be
minimal forcing along this front, so not expecting anything in
the way of precipitation along it as it moves through.
By the afternoon this front will be well north of the area.
However, a differential heating boundary will develop and this
will be the primary focus for convection. There is still
uncertainty in just how strong this boundary will be, but it
should be strong enough to get at least a couple storms to fire
across Northwest Ohio during the late afternoon and evening
hours. Isolated storms may also be able to develop in the
higher terrain of northwest Pennsylvania as we see increasing
instability developing throughout the afternoon. Some cams
(convective-allowing models) do not show any storms developing
at all, however, with the amount of instability present combined
with the boundary mentioned above and sufficient shear, this
Storms should increase in coverage after dark, especially
within a County or two of the Lakeshore, as moisture continues
to be advected northward into the area.
Environmental parameters suggest a few severe storms will be
possible from Thursday afternoon into Thursday night. MLCAPE on
the order of 1500 j/kg (eastern areas) to 2500 j/kg (northwest
ohio), combined with 30 to 40 knots of 0-6km bulk shear and
steep low-level lapse rates suggests the primary threats with
any storm that develops will be damaging winds and large hail.
If a storm can become rooted along the differential heating
boundary in Northwest Ohio, then an isolated weak tornado cannot
be ruled out. Storms will begin to weaken/dissipate after
midnight or so.
Short term /Friday through Saturday night/...
broad upper level trough will swing east across the forecast area
through this forecast period. A weak shortwave trough will move
east across the region Friday setting up a narrow low level jet
streak across Lake Erie Friday into Friday night. This will put
the local forecast area in the right rear quad of the jet as
well. Abundant moisture appears to be surging into the local
area Friday along with a weak area of low pressure and a warm
frontal boundary stretched west to east across the lower Great
Lakes. All of these features working together in concert will
bring another round of showers and thunderstorms to the forecast
area Friday. Warm air advection south of the warm front will
help boost temperatures back into the 80s due to the low level
jet in place. Breezy conditions will take place as well at
between 10 and 20 knots.
The whole weather package will shift east Friday night into Saturday
allowing a ridge of high pressure at the surface to build in from
the west Saturday through Sunday. This feature will try to make an
attempt to bring drier weather to the local area. However, with
upper level trough in place, can't rule out a possibility for a
slight chance for showers and thunderstorms by Sunday. Slightly
cooler air pushes southeast in the wake of the surface low
pressure system. Although, temperatures will still remain in the
upper 70s east to lower 80s elsewhere across the area Saturday
Due to the warm air advection Friday night, will likely see balmy
temperatures in the lower 70s for lows.
Long term /Sunday through Wednesday/...
near normal temperatures expected through the long term period,
Sunday night through Wednesday, as a stationary front remains
settled over the region. There will likely be some temperature
variations depending on the boundary location, but it's way too
early for specifics, so will opt for consensus blend for temps.
Pops will increase during this period, especially Tuesday as
long range models peg low pressure tracking across the region.
Will opt for no higher than chance pops at this point.
Aviation /00z Thursday through Monday/...
VFR conditions will continue through Thursday morning. Middle
and high level cloud cover will vary in thickness through the
morning. We should then see cumulus develop and increase in
coverage through the afternoon. Lots of uncertainty on
thunderstorm chances during the afternoon with some convergence
near or over the lake mid to late afternoon. For now have only
introduced a vicinity thunder chance at kcle. The better chances
for thunder develop during the evening as a cold front moves
into the area. MVFR/IFR conditions will likely develop with this
Outlook...non-VFR conditions possible in thunderstorms Friday
afternoon/evening into Friday night, then again on Saturday.
southwesterly winds will quickly increase Thursday morning into
the afternoon hours. With the southwest flow the higher waves
should generally tend to stay out in the open waters, but winds
will approach Small Craft Advisory criteria. Will hold off on
issuing for now and pass it off to the next shift. Winds will
begin to calm down a bit Thursday night, but storms chances will
be increasing through the late evening and overnight hours.
Winds will be around 15 to 25 knots on the lake Friday out of the
southwest and then quickly diminish as a cold frontal boundary
slides southeast across the lake Friday night. Generally light and
variable flow is expected Saturday increasing to 15 to 25 knots
again Sunday from the southwest as a surface high pressure ridge
builds east into the region.