Scientific Forecaster Discussion
fxus61 kcle 211037
Area forecast discussion
National Weather Service Cleveland Ohio
637 am EDT Mon Aug 21 2017
high pressure over the region will continue to move east of the area
today. Low pressure will move northeast across the Great Lakes
Tuesday, forcing a cold front across the region Tuesday evening.
High pressure will build east across the region Wednesday through
the first half of the weekend.
Near term /through Tuesday/...
no major changes with this update. Still a lot of clouds
upstream that may hamper viewing of the eclipse this afternoon.
Made some minor adjustments to hourly temperatures to cover
warmer than expected overnight lows.
Nearly zonal flow will persist across the country today as a
weak shortwave trough moves east across the region. This feature
along with some limited moisture and day time heating will
support increasing cape through the afternoon. Can't rule out
the possibility for scattered showers and thunderstorms this
So, the threat for showers and thunderstorms could mess up viewing
of the long awaited solar eclipse this afternoon. I am thinking it
will be a 50/50 shot at actually having a good view of the moon/sun
The convective activity will begin to wane later this
evening after sunset as shortwave pulls out to the east. The next
threat for showers and thunderstorms will increase through the day
Tuesday when the next cold front approaches the area. There are
some indications that a pre-frontal trough will develop ahead of the
cold front and could become the leading focusing mechanism to
produce the convection. This could mess up the timing of the
precipitation for a severe weather threat by stabilizing the
atmosphere through the morning and preventing any day time heating
from becoming dramatic.
Now, if the GFS is correct with the later timing of the front and
pre-frontal trough, then, we should see some heating in the east to
aid in destabilization. Cape values will be approaching 2000 j/kg
mainly in the east during the afternoon. The Storm Prediction
Center already has the eastern two thirds of the area in a slight
risk for severe thunderstorms for tomorrow. Will hold off on
mentioning any severe threat in the forecast at this time due to the
issues mentioned above. Would rather use that terminology when
threat is imminent.
Otherwise, temperatures will be on the warm side again today. Highs
will be between 86 and 88 degrees across the area except 82 to 84 in
the east. The other issue is we will see dewpoint temperatures
begin to climb into the upper 60s to lower 70s later today and stay
there overnight. This will make for another muggy and sticky night.
Highs on Tuesday will be slightly cooler as pre-frontal convection
develops in the west. If we get sun in the east, then I think
temperatures will be warmer than currently forecast.
Short term /Tuesday night through Thursday night/...
as is often the case this time of year, not sure exactly where the
front will be located come Tuesday evening. The prefrontal trough
will certainly be well east of the area but the front could be
hanging back or perhaps the 850 mb front might not have crossed all
of northeast Ohio and northwest PA. Will keep a chance of
showers/storms over the eastern half of the forecast area, mainly
High pressure is progged to build in quickly on Wednesday. 800 mb temps
are progged to drop to about +9c but the inversion is progged to be
low with plenty of subsidence. Not expecting any lake effect precip,
probably some clouds though, mainly early. It will be
noticeably cooler and less humid with highs in the 70s.
Most of the models suggest a trailing short wave will drop through
the trough aloft come Wednesday night into Thursday. Will have a
small chance of showers, mainly in the snowbelt, both primary and
secondary, given the shift to a north wind. Some areas may not get
out of the 60s on Thursday.
Long term /Friday through Sunday/...
high pressure should build across the area late in the week.
Unseasonably cool temperatures will continue Friday, again with some
sections of extreme northeast Ohio and northwest PA not getting out of
the 60s. The anticyclonic flow should discourage any precip although
there may be some lake effect clouds on Friday. Saturday should be
The high will begin to shift east of the area on Sunday. With an
east flow in the boundary layer, we will likely not warm up too
quickly. High clouds may begin to spread in from the west. Highs in
Aviation /06z Monday through Friday/...
area of showers and thunderstorms moving east out Indiana
expected to weaken as they move east but will be in the vicinity
of Toledo and Findlay. Otherwise, there is the possibility for
some widely scattered thunderstorm activity across the area
today. Will mention thunderstorms in the vicinity across much of the area for today. Expecting
mainly middle and high clouds through the rest of the day into
tonight with the exception of the cumulus clouds that develop in
association with the showers and thunderstorms. Winds should
shift around to a south to southwest direction for today and
become light and variable again tonight.
Outlook...non-VFR likely in scattered showers and thunderstorms
Tuesday and Tuesday night.
high pressure will drift off to the east today with a light south
flow on Lake Erie. A few thunderstorms will continue to develop
today into early tonight and mariners will have to be alert for
thunderstorm wind gusts and wind shifts in the vicinity of the
A strong cold front will Cross Lake Erie later Tuesday. The
southwest flow will increase tonight and Tuesday morning ahead of
the front. Thunderstorms will be likely Tuesday. A Small Craft
Advisory may be needed up the east Lakeshore on Tuesday east of
Cleveland, especially from around Ashtabula and Erie, PA eastward.
Winds should begin to diminish on Wednesday but with colder air
aloft and efficient mixing, the Lake May remain stirred up on
Wednesday. High pressure and lighter winds are expected late in the