Area Forecast Discussion
Issued by NWS Cleveland, OH

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FXUS61 KCLE 211358

Area Forecast Discussion
National Weather Service Cleveland OH
958 AM EDT THU JUL 21 2016

High pressure over West Virginia early this morning will drift
eastward off the East Coast today. This will allow a warm front
to lift northeastward across the region through this evening. A
weak cold front will sag southward across the central Great Lakes
Friday night. A stronger cold front looks to arrive Sunday night
into Monday.


Update...Main concern for today is the thunderstorm complex to our
northwest dropping southeast into the area late this afternoon and
early evening. Updated pops higher into the chance category to
reflect the possibility of this occurring. There is also a threat
for severe weather with the storms. Will continue to watch this
complex and may need to raise pops further. Preliminary timing of
current convection is 22z in nwrn Ohio and adjusted pop/wx grids
accordingly across the area based on this timing however this
first area of convection could diminish with another forming which
would alter timing significantly to later in the evening. also
adjusted temps and dewpoints and resultant apparent temps. still
do not reach advisory criteria today for heat but for friday we do
so may need heat headlines for tomorrow west half.

original...High level cloud cover and some afternoon cumulus are
expected today but it will only become partly cloudy. It will be a
couple degrees warmer across the region with highs ranging from
the mid 80s across NW PA with near to slightly above 90 degrees
elsewhere. Heat index values will likely reach the mid to upper
90s across NW OH. Since this is just below heat advisory criteria
we will hold off on the headlines.


Warm front will be north of the area tonight with warm and humid
conditions expected. This boundary and a ripple of jet energy in
the flow over southern Ontario should be enough to generate
thunderstorms over the upper Great Lakes this afternoon and
evening. The uncertainty is how for south and east these
thunderstorms will be able to reach as the outflow rounds the east
side of the large area of high pressure over the central US.
Current thinking is that some of the convection will be able to
maintain itself as it moves across Lake Erie after midnight.
There is going to be plenty of moisture to feed the convection
but the middle level warm air may be able to limit the coverage.
There remains a conditional probability of severe thunderstorms
for the area. The main concern late tonight will be strong winds.
The outflow boundary from this convection will likely be located
somewhere over northern OH and NW PA on Friday and is expected to
play a role in new development. Again the middle level warmth may
be able to limit the coverage. Any of the storms that can
regenerate on Friday have the potential to produce large hail and
strong winds. A weak cold front will sag southward across the
region friday night into early saturday but it will not provide
much relief from the heat.

It will feel uncomfortable Friday into Saturday with dewpoints in
the upper 60s to lower 70s. Convective debris cloudiness will be
an issue on Friday but how much it can limit afternoon heating is
uncertain. A heat advisory may be needed for portions of Northern
Ohio from Cleveland westward to Toledo. Will let later shifts take
another look at this potential. Highs Friday and Saturday will
range from the upper 80s to mid 90s.


An upper trough crossing the lakes will help to try and trigger sct
tsra sun into sun night with maybe enough leftover moisture in these
on mon for a continued threat there. Well above normal temps on sun
with highs into the lower 90s in many areas will moderate down a
little closer to normal for mon thru wed. Some increased moisture
starts to return by wed so there could be some isolated
convection developing with daytime heating.


.AVIATION /12Z Thursday THROUGH Monday/...
Any patches of fog will dissipate by 13z to 14z.

VFR will prevail until later tonight when shra/tsra are supposed to
drop se into the area. This far out will just use vcsh due to the
uncertainty of these type of systems driven largely by just
convective processes. Some of the storms could be on the strong to
severe side.

With increased dewpoints and possible rainfall more fog is likely to
form late tonight.

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


SW winds should increase to 10 to 20 knots for tonight thru fri
then diminish and become north late fri night into sat as a weak
cold front drifts south across the lake. The position of the weak
front is in question sun thru mon so given the weakness of the
features expect light and changeable winds.




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