Area Forecast Discussion
Issued by NWS Wilmington, OH-- Highlight Changed Discussion --
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FXUS61 KILN 200739
Area Forecast Discussion
National Weather Service Wilmington OH
339 AM EDT WED JUL 20 2016
High pressure will extend across the Ohio Valley and mid-Atlantic
states today, with warm and generally dry conditions expected. As a
large ridge builds over the central part of the country, heat and
humidity will continue to increase through the weekend, with the
warmest conditions expected on Friday and Saturday.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A large ridge of high pressure aloft has become well established
over the central plains. At the surface, high pressure currently
extends from the mid-Atlantic through the Ohio Valley, and will
grow as it shifts gradually southward over the next day or two.
Near-surface flow over the ILN forecast area remains quite weak,
and this will remain the case through the day today, with only
light southeasterly winds expected. The air mass has changed only
very slightly from yesterday, allowing for a slightly-adjusted
persistence forecast for max temperatures today, with no
significant change in surface dewpoints either.
The only significant challenge for the forecast today is for any
convective potential. First and foremost, the cluster of storms
currently over southwestern Indiana has continued to defy model
projections by maintaining a slow easterly progression. This
cluster split off from an earlier MCS, which had been propagating
southeast along the 925mb theta-e gradient. The storms, as they
currently exist and propagate, are expected to soon outrun their
favorable environment. There is a notable dewpoint gradient from
southwest Indiana to southeast Indiana, and less favorable thermal
conditions just off the surface will also mean that any elevated
instability feeding the storms will become weaker with eastward
extent. SPC mesoanalysis indicates about 1000 J/kg of MUCAPE where
the storms are currently located, but this diminishes to well
under 500 J/kg at the border of the IND/ILN forecast areas. If
they were to survive, at their current rate, it would take until
7AM for the storms to move into the ILN CWA.
Though a few models suggest a chance for some precipitation in the
western half of the forecast area this afternoon -- and a very,
very isolated shower/storm or two may well occur -- the vast
majority of locations should remain dry. The forecast will do the
same as of now.
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
The short term forecast discussion will be updated soon.
Previous discussion >
Surface high pressure across the area on Wednesday will push to
the east on Thursday. There is northwest flow aloft, however any
disturbances are weak and generally east or west of the area. With
no clear preciptiation signal, decided to go with a dry forecast
at this time.
Wednesday will be the cooler of the two days. As the high shifts
to the east southerly flow will increase on Thursday and warmer
air will move into the area. Heat index values will approach 100
across southwest portions of the forecast area on Thursday,
however have values just under the 100 degree mark (heat advisory
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
With an upper ridge established across the CONUS, a hot and
mainly dry period is expected.
For Friday, a few afternoon thunderstorms may be triggered in an
unstable airmass by a short wave rounding the crest of the upper
ridge. Isolated thunderstorms may still occur Saturday under weaker
forcing but persistent instability.
On Sunday, greater short wave energy entering the northern plains is
forecast to develop a surface low that will drag cold front toward
the ILN area. A better chance for thunderstorms will exist in
increasing moisture and forcing ahead of the front. The chance for
convection will continue Monday as the front makes its way across
the area. Look for drier conditions Tuesday under weak high pressure
behind the front.
Temperatures will be hot. Highs in the 90s are forecast Friday
through Sunday, with heat indices reaching heat headline criteria
over 100. Somewhat cooler readings in the mid and upper 80s are
expected Monday and Tuesday due to modest cold advection.
.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
Surface high pressure centered over the eastern Great Lakes this
morning will continue to extended southwest into the mid and upper
Ohio Valley through tonight. Some cirrus can be expected from time
to time in the northwest flow aloft along with some scattered
diurnal cumulus clouds. Winds will be calm or light easterly this
morning, light and variable this afternoon, then back to a light
east or southeast wind tonight.
OUTLOOK...Thunderstorms possible Sunday.