Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 282342

Area Forecast Discussion
National Weather Service Wilmington OH
742 PM EDT SAT MAY 28 2016

The Ohio Valley region remains in between low pressure in the
upper Mississippi Valley and high pressure off the mid-Atlantic
coast. This will support a chance of showers and thunderstorms at
times through Sunday. After a cold front moves through on Sunday
evening, drier conditions are expected for Monday and Tuesday,
with surface high pressure moving into the area. Chances for
precipitation will increase again later in the week.


Both at the surface and aloft, low pressure is located over the
upper Mississippi Valley, and high pressure is centered just east
of the mid-Atlantic coast. With little-to-no impact from TD2
expected with regards to the overall pattern over the Ohio Valley,
nothing significant has changed for the ILN forecast area, in a
regime of weak forcing and very slightly confluent flow in the
boundary layer.

With no significant capping today, showers and thunderstorms have
been able to develop, though the weak forcing and near-zero wind
shear have kept this activity very disorganized. Signals from
various high-res models (HRRR / NSSL-WRF / WRF-NMM) are all very
similar, focusing the period of scattered thunderstorms through
the peak of the diurnal cycle -- and allowing for much drier
conditions by evening. Without any other clear signals for storm
focus in either model or observational data sets, the current
forecast (30-50 percent chance of storms) will remain in place
through evening, before switching to dry conditions overnight.

The air mass has changed only slightly from yesterday (outside of
the storms), but is generally a little more moist. Based on
current dewpoints, and looking at last night`s low temperatures, a
min temp forecast in the middle to upper 60s appears reasonable.


Sunday is expected to begin with generally dry conditions, with
very little overall adjustment to the weather pattern. That will
change later in the day, as the troughing over the upper midwest
moves northeast, and begins to flatten the east coast ridging into
more of a zonal pattern across the Ohio Valley by Monday. As this
process occurs, and as the axis of the trough (weak as it may be
this far south) moves through, a weak cold front will also move
ESE across MI/IN/OH. Neither the air mass change or wind shift
with this front will be particularly strong, so the amount of
forcing it will provide is definitely worth questioning.
Otherwise, ahead of the front, the pattern will remain weakly
forced -- probably similar to today (Saturday), with a chance for
disorganized storms (generally on the weaker end of the scale) to
develop as diurnal heating kicks in. Any chances for stronger
storms will probably be limited to areas closer to the front,
which based on timing would probably only really include the
northwestern section of the ILN forecast area. Shear is not going
to improve from current conditions -- 0-6km values of around 20
knots, and much less closer to the ground. Though instability will
not be lacking (MLCAPE forecast to be 1200-1800 J/kg on Sunday
afternoon), the forcing and shear are too weak to support a
significant severe threat, with too low of confidence to even
mention in the HWO at this point in the forecast process.

Max temps for Sunday were increased slightly ahead of the front,
especially in the southeastern CWA, where temperatures today are
pushing well into the mid 80s. Expected clouds and possible
convection will keep temperatures a little lower in the northwest.
The slightly drier air moving in behind the front on Sunday night
will allow for min temps in the lower 60s.


In the wake of a weak cold front, high pressure will settle across
the region for the Monday/Tuesday time frame. Above normal readings
will continue with highs in the lower to mid 80s and lows in the
lower 60s.

A mid level trough will be the main weather feature from mid to late
week as it slowly progresses from the northern/central Plains to the
Great Lakes. We should squeeze out one more dry day Wednesday, with
increasing chances for showers/storms late Wednesday night into
Thursday as associated surface cold front moves into the region
from the west. By Friday, the front will slip south of the Ohio
River, with drier conditions moving in behind. Temperatures will
cool some due to clouds/precipitation and then eventually some CAA
in the wake of the front.

For the upcoming weekend, models continue to forecast a long wave
trough developing over the western Great Lakes and extending
southward into the mid/lower Mississippi River Valley. There are
some indications that a weak impulse rotating through the eastern
part of this trough axis may bring a chance of showers and storms
across our eastern/southern zones on Saturday where mid to upper
level lift and deeper moisture will exist. The lower heights and
cooler 850 mb temperatures will result in temperatures going below
normal, with highs in the lower to mid 70s and lows in the 55 to
60 degree range.


Scattered convection continues to pop up late this afternoon.
Based on radar coverage attm included a tempo of MVFR TSRA at
KCMH and KLCK for the first hour of the TAF period. It is looking
like the rest of the TAF sites will remain dry this evening as
pcpn is expect to disipate with the loss of daytime heating.

Clouds from the convection to the west should provide a cirrus
canopy overnight. By 09Z, models are bringing an increase on H8
moisture as upper level vorticity works into the region on the SW
flow aloft. Brought a VFR cig into the wrn TAFS with this feature
and gradually spread it over the ern TAFS by 12Z.

By 12Z, upper level energy and some moisture from TS Bonnie
reaches the ern portions of the fa. There could be some scattered
showers during the morning due to this feature.

The clouds cover and showers should help deter convective
development for a good part of the day, but by 21Z a consensus of
the models bring a line of thunderstorms into the wrn TAFS.
Covered this with VCTS since it is towards the end of the TAF

OUTLOOK...Showers and thunderstorms are possible Thursday.




NEAR TERM...Hatzos
LONG TERM...Hickman
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