Area Forecast Discussion
Issued by NWS Cleveland, OH

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FXUS61 KCLE 202328
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
728 PM EDT Sun Aug 20 2017

.SYNOPSIS...
High pressure over the region tonight will move east of the area on
Monday. Low pressure will move northeast across the Great Lakes
Tuesday, bringing a cold front across the region Tuesday night.
High pressure will build east across the region Wednesday
through the first half of the weekend.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
Lower confidence forecast tonight through Monday night as several
upstream MCS` will impact the weather across the region. Return flow
will continue to feed into the region as high pressure is now
centered east of the forecast area. Low level moisture increase
reflected in visible satellite picture as expansive cu field
blankets much of western Ohio this afternoon. Some signs of isolated
convection beginning on latest radar scans, as 1000-2000 j/kg SBCAPE
creeps up into the southern part of the forecast area. Although
forcing is minimal, with upstream MCV approaching the area from the
west, will opt for a few hours of slight chance pops through the
evening hours. Will terminate pops around 03Z time frame, however
some guidance suggests convection may sustain a bit longer.
Nevertheless, any shower activity is expected to be very isolated
and concentrated from near Marion to Canton.

Forecast picture becomes a little more obscure late in the overnight
into Monday. Upstream MCV will cross IN and move into OH during the
overnight. Models are developing convection off of the trailing
flank of this MCV somewhere in northern IN. Currently forecasting
this activity to remain upstream, however cloud debris from this
convection could move into the area through the morning hours. The
debris clouds should diminish into the afternoon hours, with diurnal
cu developing across the area. Pops will slowly increase during the
afternoon on Monday, with slight chance pops for most locations.
Atmosphere will become very unstable, with models suggesting up to
2500-3000 j/kg by late afternoon. Forcing remains conditional,as
upstream MCS remnants may track towards the area during the
afternoon. If this comes to fruition, a low end severe risk is
possible, with low/mid level flow beginning to increase a bit, with
20-30 kts of low level shear. Most likely, if any convection forms
it would most likely be after 21Z, but it is still very low
confidence with uncertainty in the upstream evolution tonight/Monday
morning. No major changes to high temps tomorrow, with uncertainties
in cloud cover/precip.

Main cold front/upper trough will move toward the region Monday
night. Kept slight chance/low chance pops around through the night,
but the bulk of precip activity will remain west of the area until
12Z Tuesday.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Tuesday begins with models showing low pressure moving into
southeast Ontario from the central lakes. A trailing cold front
will extend southwest across the lakes to west of Chicago.
Moisture will be moving into the area from the southwest ahead
of this boundary and will continue with chance pops most places
through the morning and likely pops northwest. The front will
moves across the area through the afternoon and early evening
bringing showers and thunderstorms to most. Have boosted pops to
categorical for all areas through the afternoon with precip
ending from the northwest through the evening hours. Wednesday
begins dry however models show wrap around moisture dropping
across the area through the afternoon. With 850mb temps down
around +9C moving over the warm lake as well as general
instability provided by daytime heating below colder air aloft
will have 20% pops in place for the area and chance pops for
showers se of the lake. Will drop lake effect pops to 20%
Wednesday night and Thursday as high pressure builds in. Tuesday
temps near normal. Wednesday and Thursday will be below with
highs in the low to mid 70s.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Little change in the extended with a large area of high pressure
remaining the dominate weather feature.   By Wednesday evening large
area of Canadian high pressure centered over the Northern Lakes. The
high moves slowly across the lakes and moves off the New England
Coast late Sunday.   Expect mostly sunny conditions, highs mainly in
the 70s and lows mainly in the 50s.    Model timing on the next
system still a little in doubt.  ECMWF brings the next wave of
convection Sunday night while the GFS holds off until Monday.  For
now will just go low chance pops in the West Sunday night.

&&

.AVIATION /00Z Monday THROUGH Friday/...
Lot`s of mid and high level clouds floating across the area. As
predicted earlier by the guidance a few storms have popped up
over the southwest end of the area. These could impact FDY and
possibly MFD so will go with a brief mention those two sites.
The activity should diminish after the sun sets. More precip
could impact the area toward daybreak and again late tomorrow
afternoon. This activity depends on what happens upstream
overnight so confidence is low. Will go with a vicinity mention
tomorrow morning at FDY and TOL but will keep the afternoon dry
for now. There should be a lot of mid and high level clouds on
Monday. Light and variable flow is expected overnight. The
clouds should keep fog from becoming widespread but some patchy
MVFR fog is again possible. Southwest flow under 10 knots is
expected on Monday with onshore winds again developing at ERI.

OUTLOOK...Non-VFR likely in scattered showers/tstms on Tuesday
and Tuesday night.

&&

.MARINE...
Marine wx looks fairly tranquil tonight through dawn Tuesday
and again Thursday through Friday with high pressure affecting
the region. Monday night into Tuesday morning models show low
pressure moving through the central Great Lakes toward
southeastern Ontario. This will increase the pressure gradient
across Lake Erie causing southwest winds to increase to 15 to 25
knots Tuesday. The associated cold front will drop across the
lake Tuesday afternoon and evening turning winds northwest. Wind
speeds will drop a bit to 15 to 20 knots however northwest flow
will keep waves up on the lake. Wednesday high pressure will
build from the west slowly relaxing the gradient however waves
will remain up through much of the day before dropping off
Wednesday night. Expect a small craft advisory will be needed
from Tuesday morning into Wednesday night.

&&

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

&&

$$
SYNOPSIS...Greenawalt
NEAR TERM...Greenawalt
SHORT TERM...TK
LONG TERM...DJB
AVIATION...Kubina
MARINE...TK



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