Area Forecast Discussion
Issued by NWS Cleveland, OH

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970
FXUS61 KCLE 281015
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
615 AM EDT Wed Jun 28 2017

.SYNOPSIS...
High pressure Over the Upper Ohio Valley will slide SE and move
off the East Coast this evening. This will allow a warm front to
lift NE across the area Thursday. The front will stall and
linger over the local area into Friday and become the focus of
convection.

&&

.NEAR TERM /THROUGH THURSDAY/...
No significant changes to forecast.

Original discussion...
High pressure centered over the Upper Ohio Valley will keep the area
dry through the forecast period.   The high will slide SE today
setting up a SWLY flow and a warming trend for the forecast area.
Temps will warm into the mid to upper 70s in the East and near 80 in
the West.

The high pressure will move off the East Coast today.   This will
allow a warm front to lift NE across the area on Thursday.  Models
still not in good agreement on the exact timing of the front.
Front expected to stall across the forecast area but still some
doubt as to exactly where front will stall out.

Expect thunderstorms to develop Thursday afternoon and evening.
SPC has western 2/3 of the forecast area in a Slight Risk for
Severe and the remainder of the area under Marginal Risk. Capes
rise to 1200 j/kg in the East and around 2000 J/KG in the West.
Marginal shear as the 925MB winds increase to around 35 knots.
Plus since the front will be lying west to east could see some
training of thunderstorms which could produce some localized
flooding potential.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
The trough that has been developing over the high plains will move
east to the Great Lakes as we head into the weekend. A strong low
level jet combined with a brisk jet aloft lingering over the Great
Lakes will lead to a series of thunderstorm complexes crossing the
Great Lakes Thursday/Thursday night into Saturday. This complicates
the forecast since thunderstorm development will occur on outflow
boundaries and mesoscale features and not necessarily the synoptic
pattern.

With the 850 mb jet over the lower Great Lakes Thursday night, will
have "likely" pops near Lake Erie with lesser pops father south.

Not sure how much convection may occur on Friday. The low level jet
is progged to lighten and the front remains well to the west but the
GFS is progging sfc capes near 4k with small/moderate amounts of
shear. Will have chance pops over most of the area with "likely"
pops near Toledo and NW PA. The thermal fields on most of the models
are chaotic looking Friday, indicative of the convection the model
thinks may be occurring. Highs could get very warm, around 90, if
the showers/storms hold off, or be in the lower 80s if there were
enough clouds and showers. Will split the difference and forecast
highs generally in the mid 80s.

There remains uncertainty on the timing of the front for Saturday.
The ECMWF continues to develop a stronger surface wave on the front
as it crosses the Great Lakes Friday night into Saturday. This may
be convective feedback. Given the time of year and the positively
tilted trough aloft, will not be in a hurry to push the front
through and continue to forecast chance or likely thunderstorms,
with the higher pops toward the OH PA border. Highs Saturday near
guidance, generally in the lower 80s.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
A flat trough is progged to linger into early next week before
heights start to rise as the ridge builds in the middle of the
country. This will typically lead to thunderstorms from the upper
midwest and Mississippi Valley into the lower Great Lakes and ohio
Valley. We may get lucky and have a dry Monday but will have to have
showers and thunderstorms in the forecast after that. Temperatures
will likely be near normal.

&&

.AVIATION /06Z Wednesday THROUGH Sunday/...
VFR conditions will continue through the forecast period with
high pressure over the Upper Ohio Valley. The only weather to
contend with will be a cirrus shield that will overspread the
area this morning.

OUTLOOK...Non- VFR conditions possible in thunderstorms
Thursday into Friday.

&&

.MARINE...
A SW flow on the lake this morning will gradually back to
the south later today. South to southwest winds will pick up on
Thursday as the low level jet slides across the eastern Great
Lakes. Wind speeds will likely stay just below small craft
advisory criteria and waves will be larger in the open waters
and on the Canadian side of the lake. Those that stay near the
south shore will find conditions remain rather quiet but those
heading out into the open water will find the going get rougher
Thursday.

The south to southwest flow should calm down a bit Thursday
night into Friday but there will be an increasing chance for
thunderstorms as a cold front approaches. The front is rather
slow moving and will cross the lake on Saturday. Winds will
veer more southwest to west by Saturday night and Sunday. Winds and
waves will likely approach small craft criteria on the east half of
the lake on Sunday.

&&

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

&&

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



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