Area Forecast Discussion
Issued by NWS Cleveland, OH

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FXUS61 KCLE 210744
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
344 AM EDT Mon Aug 21 2017

.SYNOPSIS...
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/...
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 afternoon.

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
combo.

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 OH and northwest PA. Will keep a chance of
showers/storms over the eastern half of the forecast area, mainly
before midnight.

High pressure is progged to build in quickly on Wednesday. H8 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 OH 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
sunny/mostly sunny.

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
the 70s.
&&

.AVIATION /06Z Monday THROUGH Friday/...
A small area of convection moved quickly along the shore of Lake
Erie and will arrive near Erie in the next hour or so. Another
area moving east out of Indiana is expected to weaken before it
arrives in Findlay. Otherwise, there is the possibility for some
widely scattered thunderstorm activity across the area today.
Will leave TAFs dry through the day since there is a low
probability that any site will see the activity. May need to
adjust with the 12Z TAFs later this morning. Expecting mainly
middle and high clouds through the rest of the day into tonight.
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
on Tuesday and Tuesday night.

&&

.MARINE...
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
storms.

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
week.
&&

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

&&

$$
SYNOPSIS...Lombardy
NEAR TERM...Lombardy
SHORT TERM...Kosarik
LONG TERM...Kosarik
AVIATION...Lombardy
MARINE...Kosarik


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