Area Forecast Discussion
Issued by NWS Cleveland, OH

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000
FXUS61 KCLE 212229
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
629 PM EDT THU JUL 21 2016

.SYNOPSIS...
High pressure along the east coast will drift south through
Friday. This will allow a weak cold front to sag southward across
the central Great Lakes Friday night. A stronger cold front will
arrive Sunday night into Monday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Early this evening...The main focus remains the ongoing MCS which
continues to work its way across far western Lake Erie and
northwest Ohio. The strongest convection is shifting south-
southeast into an airmass with higher precipitable water values and
stronger instability. The eastward progressing portion of the MCS
moving across the lake and northern Ohio has been rapidly
weakening due to the weaker instability in place with the 22Z EMC
RAP Mesoanalysis indicating surface-based CAPE values down to
1000 J/kg or less. In addition, a sharp gradient in precipitable
water values is present with values around 1.25 to 1.50 inches now
across much of the area, compared to around 2 inches across far
northwest Ohio and northern Indiana.

For the remainder of the evening, expect the line of convection to
continue to weaken/dissipate. It`s very possible that the rain may
not even make it into the Cleveland area given the latest trends.
The forecast was adjusted to lower PoPs across the eastern CWA,
but additional downward adjustments to PoPs will likely be needed
across the rest of the area for the late evening hours.

Overnight...many of the high resolution mesoscale models indicate
scattered showers and thunderstorms redeveloping as a forming MCS
over Wisconsin drops southeast and into the area. Best timing
appears to be after 3 or 4 AM, and have maintained at least a
chance of showers and thunderstorms in the forecast late. There is
a small potential for a few of the storms to be strong as models
show surface-based CAPE values rising to 1500-2000 J/kg, but still
considerable uncertainty given the unfavorable timing.

Considerable debris cloudiness and a southerly flow will result
in a mild night, with lows in the upper 60s to lower 70s.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/...
Issued a heat advisory for Friday and Saturday. Concern is how
much convective debris remains across the area from overnight
storms. Also could see development on friday so again...any
convection/cloud cover would prevent heat index from reaching 100.
However am anticipating a good amount of sun and with 850mb temps
in the lower 20s we should get into the 90s. Dewpoints also in the
lower/mid 70s so many places should reach an index of 100. Friday
capes still above 2000 j/kg although most unstable air remains
well to the west. Still...will have chance pops in place as we
should see afternoon/evg storms develop. The cold front dropping
across the lake Friday evening now appears to be slowing into the
area and will pass through early Saturday. Am concerned about the
possibility for convection south half during the day along and
ahead of the front. Will have chance pops in place south. Sunday
the front returns from the west/southwest ahead of an approaching
cold front. The GFS develops convection across the top of the
upper ridge to our northwest so again it would be possible to see
some of this drop into the area so will have chance pops
continuing.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Chance for some lingering showers across the sern portion of the
forecast area Monday morning as the weak front/trough moves east. A
little bit of a break in the heat after that...as another large area
of high pressure will moves East across the the Great Lakes.  The
high shifts east of the lake Tuesday and reaches the East coast
Wednesday.   After that models diverge...GFS moves low across the
Northern lakes Friday dragging a cold front across the area.  ECMWF
on the other hand moves it across the lower lakes.   Either way
chance pops by Thursday night.

&&

.AVIATION /18Z Thursday THROUGH Tuesday/...
Line of TSRA moving across lower Michigan will intensify this
afternoon and evening. SPC has upgraded northern lakeshore to
slight risk.  Best chance would be the western third to half.
Models continue to show weak front moving across the area late
tonight into tomorrow morning.

OUTLOOK...Areas of non vfr from shra/tsra possible Fri into Mon.

&&

.MARINE...
Severe potential tonight as line of strong TSRA moving across SE
lower Michigan moves into Western basin of Lake Erie late this
afternoon. Potential for 50-60 kt gusts with stronger storms.  Still
doubts as to how far east the storms will hold together...but best
chances would be west of Mentor.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Heat Advisory from 11 AM Friday to 9 PM EDT Saturday for
     OHZ003-006>011-017>021-027>031-036>038-047.
PA...None.
MARINE...None.

&&

$$
SYNOPSIS...TK
NEAR TERM...JAQ
SHORT TERM...TK
LONG TERM...DJB
AVIATION...DJB
MARINE...DJB



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