Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
408 PM EDT Friday Aug 1 2014
a trough of low pressure will serve as a focus for showers and
thunderstorms through Saturday. High pressure will build in early
next week. A weak boundary will move to the Ohio River late Tuesday
and into Wednesday...bringing the next threat for showers and
Near term /until 6 am Saturday morning/...
a weak inverted trough will be located across the region today.
Moisture will pool northwest and southeast of the boundary and
spark showers and thunderstorms over West Virginia and northern
Indiana. The few showers north of Columbus will wane fairly
quickly this afternoon and move north and away from the forecast
area. Rest of the region will see an increased threat continue
into tonight. Models are not agreeing on any one particular spot
getting showers tonight...but all have something somewhere over
County Warning Area and I cannot discern where to keep a chance of
showers/thunderstorms out of tonight. Therefore...entire County Warning Area has
at least a low chance of precipitation overnight.
Lows will be in the lower 60s for most of the region. Cloud cover
and increased moisture should inhibit readings from dropping past
Short term /6 am Saturday morning through Saturday night/...
middle level trough with subtle short waves moving through it will
weaken and shift east during the period. The associated inverted
trough at the surface will persist through Saturday and then move
With heating and destabilization on Saturday showers and storms
will increase again with coverage greater than today. Appears
that activity may pass east across the region Saturday evening.
Guidance was close on temperatures...continued with a blend which
put highs within a few degrees of 80 and lows around 60.
Long term /Sunday through Friday/...
at 12z Sunday morning...pattern is still dominated by oceanic
ridging in the Atlantic and persistent southwestern Continental U.S. Ridge...with
still a modest longwave trough between the two oriented in a
positive tilt fashion from the Ozarks through the middle Ohio Valley
into southeastern Canada. A shortwave trough shifting eastward across the
Ohio Valley will help push the axis of the trough eastward into
PA/WV during the day on Sunday...and it seems recent GFS runs
which were lagging the wave back slower over Ohio have trended
toward recent European model (ecmwf) guidance. Thus...will only carry a small storm
chance in the Scioto valley of central/scntl Ohio Sunday before
drying things out Sunday night for all.
Modest height rises on Monday as the area will be between some
energy moving through the base of longwave trough to our south and
the next short wave approaching through the western Great Lakes. Maintaining a dry
forecast Monday/Monday night as weak high pressure shifts through the
area. This is about the highest confidence dry day in the extended.
Tue/Wed...has been a signal for quite some time of slightly lowering
heights in this timeframe which allows a very weak front to sag into
Ohio/ind particularly Tuesday night in Wednesday. Continue to keep Tuesday dry for
most except for areas north of I-70 which may get an afternoon
storm...but unlikely. Better chances Tuesday night/Wednesday as the front
sags slowly south through the area though again forcing/wind fields
are anemic...and little appreciable precipitable water above normal. Modest at
Building uncertainty later Wednesday into thurs/Fri. New 01.12z
European model (ecmwf) indicates weak ripple along the front and potential mesoscale convective system action
Wednesday night through the County Warning Area while previous solutions were a little
more progressive. With models showing upstream energy digging into
the cntl Continental U.S. Hard to imagine front will make much southward progress
with heights aloft starting to turn around/rise by Thursday so played
for a slower front that never really gets south of the area...thus
rain chances from Wednesday into Friday. Still looks like low-middle 80s by
day...low-mid 60s by night...with dewpoints in the low-middle 60s. Typical
early August weather for the area.
Aviation /20z Friday through Wednesday/...
at the surface...a weak surface inverted trough will propagate into
the region from the southeast this afternoon through Saturday. At
the same time...weak upper level energy will rotate slowly southeast
into the forecast area.
For this afternoon into tonight...trying to pinpoint subtle
convergent boundaries and weak forcing will make it difficult to
go with any tempo groups at this issuance. So have either employed
thunderstorms in the vicinity or vcsh...allowing short term trends (radar and convection
allowing models) dictate any necessary amendments. Given that
there should be some cloud cover overnight...have kept potential
mist/fog in the MVFR...local...IFR range.
On Saturday...with upper level energy moving into the area...along
with weak surface trough...and daytime heating...we should see the
greatest coverage for showers and thunderstorms. Have introduced
some predominate light showers between 14z and 16z along with
thunderstorms in the vicinity/cumulonimbus descriptors. It should be noted that conditions will
likely drop into the MVFR/IFR category with any thunderstorm.
Outlook...thunderstorms possible Tuesday and Wednesday.