Area Forecast Discussion
Issued by NWS Cleveland, OH

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943
FXUS61 KCLE 200120
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
920 PM EDT Wed Jul 19 2017

.SYNOPSIS...
A front near Lake Erie will waver back and forth across the area
until finally moving off to the southeast on Monday. High pressure
will spread east over the region for Tuesday and Wednesday.

&&

.NEAR TERM /THROUGH THURSDAY NIGHT/...
Tonight will be sultry with dew points in the upper 60s to lower 70s
across the forecast area. As diurnal heating starts to wane the
isolated convection that developed in the NW has mostly dissipated.
Expect fog to develop overnight, but the one saving grace is the
debris clouds from an approaching MCS should prevent it from getting
too widespread or dense.

MCS will develop across the upper Midwest tonight and reach lower
Michigan by daybreak. Still some doubt as to the exact track of the
MCS and whether it could make it into the CWA before weakening. Put
chance pops in the morning.

By the afternoon, the frontal boundary will be slowly pushing thru
the area. This will be the focus for redevelopment of thunderstorms
tomorrow afternoon and evening. SPC continues to have the area under
a slight risk of severe thunderstorms as capes of 3,000-4,000 J/kg
expected over the area tomorrow afternoon. But there is little shear
or upper level support. Convection should mostly push south of the
area late Thu night.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Lot`s of uncertainty remains during the period.  Overall have made
only minor changes to the short term given this uncertainty.
Biggest changes will be to the Friday forecast.  It now appears most
of the day could be dry...especially at the eastern end of the
area...as the surface frontal boundary sinks the south of the area.
With this in mind later shifts will have to keep an eye on things to
the northwest as convective complexes are likely Thursday night.
This activity could eventually make it`s way to the area on Friday
blowing the dry forecast.  At a minimum there should be debris
clouds over the area which will limit heating during the day.  At
the same time mid levels of the atmosphere will again be warm and
the area could be capped.  Better chances for storms will occur
Friday night into Saturday as the front is expected to move back
north.  Will leave the likely wording in the forecast as is.
Unsettled weather will continue Saturday night as well as an area of
low pressure passes to the north.  The cold front trailing this low
will kick off one last round of storms Sunday before things begin to
dry out.

Temps are up in the air during the period and depend a lot on much
sunshine occurs each day.  As it stands haven`t strayed too much
from guidance.

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
The GFS remains somewhat deeper with the trough aloft keeping a
closed low across the Great Lakes Sunday night into Monday. The
other models have an open trough. The surface high is progged to
build in slowly from the northwest on Monday and regardless of the
model, we cannot rule out a leftover shower or thunderstorm,
especially if there is a distinct surface trough or secondary cold
front that may move through. The air mass will be cooler and drier.

The surface high should be firmly in control by Tuesday as it drifts
across the Ohio Valley toward the southeast states mid week. The
northwest flow aloft will persist and it will probably take until
Thursday until the next front approaches. We should have a couple of
days mid week with temperatures a bit below normal and low dew
points.

&&

.AVIATION /00Z Thursday THROUGH Monday/...
Isolated evening shra/tsra should dissipate next hour or so. High
dewpoints and light winds should combine to allow fog to form but
debris clouds moving in from upstream convection should prevent
conditions from dropping below MVFR for most sites.

Models show dissipating MCS dropping se across lwr MI in the morning
toward the area. For now will mention vcsh for some of this reaching
the area. Better threat will be after 18z when airmass heats back up
and triggers new convection.

OUTLOOK...Non-VFR possible Thursday night through Sunday in early
morning fog/mist or scattered thunderstorms.

&&

.MARINE...
Mainly southwest winds under 10 knots will continue till a weak cold
front settles across the area early Friday. Onshore flow may develop
in the nearshore waters again tomorrow afternoon.  North to
northeast flow is expect behind the front but speeds should remain
under 10 knots.  The front will come back north late Friday and
Friday night.  Not sure if the front will actually make it over the
lake causing the flow to become southeast or if the front remain
along the shoreline with mainly east winds.  Either way showers and
thunderstorms are a good bet.   Low pressure will pass to the north
Saturday night into Sunday with the front pushing south of the area
for good on Sunday.  Southwest flow will become west to northwest
behind the front and will continue through Monday as high pressure
builds in from the northwest.

&&

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

&&

$$
SYNOPSIS...DJB/Adams
NEAR TERM...DJB/Adams
SHORT TERM...DJB/Kubina
LONG TERM...Kosarik/Kubina
AVIATION...Adams
MARINE...Kubina



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