Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
411 PM EDT Wednesday Jul 30 2014
a persistent trough will remain across the region into early next
week. This will provide near to below normal temperatures across
the Ohio Valley. Afternoon shower and thunderstorm activity will
remain possible through this time...generally ending by the evening
Near term /until 6 am Thursday morning/...
area of convection firing along a west-east convergent boundary will
make a slow progression east-southeast as the upper level trough moves east
and stretches the tail end of the convective line west towards
Indianapolis. Bulk of the forcing for these storms is east of I-71
between cmh and iln and will continue to move east.
Activity will see a significant decrease with nightfall and the
downward motion from the back side of the upper wave moving
through. Expect maybe a stray storm to make it into the evening
hours before dissipating.
Temperatures will drop to the upper 50s with clearing skies tonight.
Short term /6 am Thursday morning through Thursday night/...
similar pattern is in the offing for tomorrow but there should be
a lack of middle level shortwaves rotating through the region.
Therefore...kept the chance of precipitation out of the forecast
at this time but would not argue that an isolated shower is not out of the
Highs will rise a few degrees more tomorrow...upper 70s north
lower 80s south and overnight lows will also rise a similar amount
and only drop to around 60 or in the lower 60s.
Long term /Friday through Wednesday/...
at 12z Friday /01.12z/ -- deep eastern Continental U.S. Longwave trough remains
intact in a highly amplified northern hemisphere flow pattern
consisting of a strong Atlantic ridge...the eastern Continental U.S.
Trough...strong western Continental U.S. Ridge...and deep closed low over Pacific
waters south of Alaska. According to 30.12z GFS/European model (ecmwf)
deterministic runs...a trio of midlevel vorticity maximums
rotating down the west side of the deep closed low near Hudson Bay
and rising heights in the Atlantic Ocean will force the l/west trough
axis in the eastern Continental U.S. To retrograde/refocus back to the west over
the Ohio Valley Fri/Sat...with midlevel flow backing with time. In
fact by Saturday...a deeper southwesterly middle/upper flow field will
overspread the Ohio Valley as the trough axis reforms to the west.
These forcing mechanisms will act to recarve/sharpen the trough
during this time period...inducing subtle synoptic scale lift and
the organizing trough begins to shift east across the area on Sat
evening. While lower level wind fields will remain very weak /not
much surface reflection of these synoptic scale processes/ there
will be modest moisture and temperature rises that occur Friday/Sat
which will continue to Foster an unsettled/unstable
atmosphere...with best coverage of diurnally-enhanced
showers/storms on Saturday as a weak inverted trough tries to
develop across the area from weak low pressure in TN/KY.
Uncertainty on how fast the trough axis shifts east...seeing two
ideas in the data...one in which the axis lingers over Ohio/Kentucky
through Sunday and a more progressive solution /30.12z European model (ecmwf)/ which
shunts the axis east into PA on Sunday. The latter would yield a
drier Sunday - the former still some lingering diurnal
showers/storms. Playing continuity from previous forecast and input
from HPC will keep lower rain chances in on Sunday...mainly in cntl
Running with a dry Sun night/Mon/Mon night in wake of this feature
pushing east of the area and nondescript/weak flow pattern absent of
any waves. Tues/Wed...glancing blow from energy moving through southeastern
Canada may push weak frontal zone into Ohio/ind these days with
small chance of storms along the front Tuesday afternoon into Wednesday amidst
very weak height falls. Again...small rain chances but most areas
likely remaining dry...and warmer...as negative height/temperature
anomalies will finally have been pushed east/northeast on flattening
overall hemispheric flow.
Aviation /20z Wednesday through Monday/...
a large scale upper level trough will remain from eastern Canada
the Great Lakes and New England region...and then into the Ohio
Valley through the taf period. An embedded disturbance rotating
southeast through this trough will combine with daytime heating to
produce numerous showers and thunderstorms this afternoon...mainly
from the central Ohio tafs of kcmh/klck to Kiln. This disturbance
will move east of the area by early this evening. Subsidence in
the wake of this feature and loss of heating will allow precipitation to
shift east and also wane.
For the overnight hours into Thursday...a stronger embedded
disturbance will rotate east/southeast across the Great Lakes.
This should stay north of our forecast area and thus have little
effect except maybe a few middle clouds. Winds will become light to
calm overnight and with some clearing we should see some MVFR to
locally IFR mist at some of the taf sites. Kluk may see more river
fog and have allowed for visibilities to drop below Airport minimums.
On Thursday...area will be in a lull in terms of embedded
disturbance activity so some diurnal cumulus is expected to form
after mist/fog Burns off during the first part of the morning.
Outlook...thunderstorms possible Friday through Sunday.