Area Forecast Discussion
Issued by NWS Wilmington, OH-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KILN 241437
Area Forecast Discussion
National Weather Service Wilmington OH
1037 AM EDT WED AUG 24 2016
With upper level ridging over the southeastern states, warm and
moist air will begin to flow into the region today. Embedded waves
in the mid-level flow will bring chances for showers and storms
today and Thursday, in the northern Ohio Valley and southern Great
Lakes. High pressure over the Great Lakes will bring drier
conditions for Friday and Saturday, before chances for storms
increase slightly on Sunday and into the new week.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --Cluster of storms along the Illinois-Indiana border late this
morning should weaken as they head east across the instability
gradient. However increasing moisture along with daytime
heating...albeit somewhat limited due to cloud cover...will allow
for destabilization across the forecast area with CAPE over 1000
J/kg. In addition...precipitable water will increase to around 2
Short wave in eastern Iowa will continue east northeast...so main
forcing will pass north of the area. However...additional storms
along the tail end of this system will move into the region during
the afternoon. There could be sufficient instability for some
stronger storms into the northwest counties. These stronger storms
may produce gusty winds and locally heavy rainfall.
Forecast highs look reasonable at this point.
-- End Changed Discussion --
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
The thermodynamic environment over the Ohio Valley will continue
to modify from Wednesday into Thursday, with a steady stream of
theta-e advection to the north of the upper ridge. 850mb
temperatures are forecast to gain another 3C-4C by 18Z Thursday,
and forecasts for surface temperatures have responded in kind --
no doubt, also helped by the slightly drier forecast, as will be
discussed later. Interestingly, SREF plumes do not seem to be
totally picking up on the warmer forecasts, and the new max temp
grid for Thursday is way at the high end of the SREF spread (but
in line with raw GFS/NAM projections). This allows for lower 90s
in the southern third of the ILN CWA, with upper 80s elsewhere.
The zone of quick WSW winds aloft will remain in place just
northwest of the forecast area on Thursday, and will actually
become even better established. Still, the forcing along with this
feature (and a weak shortwave) will remain focused too far north
for a direct impact to the middle Ohio Valley, and if anything,
models have been a little more explicit in keeping drier
conditions in place for Thursday. Though this shift means a
lesser chance of convective debris affecting the area on Thursday
morning, it`s still a possibility. That would really be the only
limiting factor for instability, with SREF means (running on
boundary layer temps that may actually be too low) indicating
MLCAPE values of up to 2500 J/kg. Overall, the kinematic and
forcing pattern looks quite similar to Wednesday, but with greater
instability, and a little bit stronger shear as well. That will
mean that if storms are able to propagate this far south and east,
the threat for some strong storms will exist, with a primary
threat of wind damage. Coverage is really the big question mark,
and PoPs remain quite conservative. Until this comes into better
view, it seems premature to add the threat to the HWO.
As the dampening upper level wave moves east into Quebec, a very
weak surface front will make some progress into the ILN forecast
area on Friday, though it may never clear through the area before
stalling (or washing out). The weak forcing warrants nothing more
than a 20-percent chance during diurnal timing in the southern
third of the forecast area, with only the northern half of the
forecast area seeing a notable drop in temperatures from Thursday
to Friday (and even that will only be by about 5 degrees).
A slightly drier air mass, courtesy of a large area of high
pressure, will settle in over the Great Lakes region on Saturday.
Dry and mostly sunny conditions are expected, allowing for
temperatures to increase by a degree or two from Friday, despite
light wind flow and a fairly neutral advection pattern.
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
For Sunday, moisture and energy spilling southeastward from Great
Lakes low pressure will provide a chance of thunderstorms.
Additional thunderstorms will be possible Monday when the low is
forecast to drag a cold front across Ohio. A few thunderstorms may
persist on Tuesday as the boundary sags gradually south to
With a large and slow moving high in the upper atmosphere centered
from the Central Appalachians to the Mid-Atlantic coast, and with
mainly warm advection in the lower levels, a return to mid-summer
heat is indicated. High temperatures ranging from the mid 80s to the
low 90s will couple with dew points near 70 to make outdoor
activities uncomfortable at best.
.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
A mid level ridge over the lower Gulf Coast states will slowly
build northward through the TAF period. At the same time, embedded
disturbances will rotate eastward through the Great Lakes. Return
moist flow, along with the proximity of the disturbances, will
bring at least a chance of showers and thunderstorms to the
terminals today. Chances do not appear high at this time, but it
looks like all terminals will see enough of a threat for a VCTS/CB
to be employed. Southeast to south surface flow will become south
later this morning around 10 to 12 knots with some local gusts in
the 15 to 20 knot range by afternoon.
For tonight, the latest high resolution/convection allowing
models indicate that the threat for showers/storms overnight will
likely be closer to the lower Great Lakes, or mainly north or
northwest of the terminals. As a result, have just VFR conditions
at this time.
OUTLOOK...Thunderstorms possible from Thursday into Thursday
night, mainly near the northern terminals.