Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
643 am EDT Wednesday Jul 1 2015
high pressure will settle over the region today. An area of low
pressure will move into the Ohio Valley on Thursday into
Friday...with chances for showers and thunderstorms gradually
increasing going into the weekend. Temperatures will remain slightly
below normal for the next several days.
Near term /until 6 PM this evening/...
a rare dry day is expected for the iln forecast area today. A weak
front is currently crossing the region...moving slowly southward.
A gradually strengthening and expanding area of high pressure will
move into place across the southern Great Lakes region by
evening...with an extension of the high already entering the Ohio
Valley by earlier in the day. This will lead to generally light
winds...and dry conditions...as any convergence or upper support
for convective development will be south of the region.
The relatively cool air mass will support high temperatures about
five degrees below normal.
Short term /6 PM this evening through Friday night/...
although the brief reprieve from active weather will almost
certainly not last through the end of the week...the degree of
impact for the iln forecast area remains somewhat in question...as
the latitudinal position of the storm track coming out of the
middle Mississippi Valley is still being handled inconsistently by
the array of model solutions.
Ahead of a surface low...and powered by speedy northwesterly flow
aloft...an initial round of convection is expected to move through
the lower Ohio Valley on Wednesday and Wednesday night. By early
Thursday morning...the semi-stalled frontal boundary will begin to
pivot a little further into the Ohio Valley...eventually spreading
a chance of precipitation into the southern sections of the iln
forecast area. There are no signs of significant forcing outside
of this frontal zone...so probability of precipitation will be kept highest closer to the
front...mainly in the southern half of the forecast area.
However...how this front shifts with time (and especially the
track of surface low centers along it) remains something that is
being modeled differently on a nearly run-to-run basis. On the
north side of the boundary...instability will be generally fairly
weak...so any severe threat appears likely to remain confined to
south of the forecast area.
Although temperatures for Thursday and Friday were lowered
slightly from previous forecasts...the position on the north side
of the frontal boundary and possible precipitation will mean that
these numbers could still be on the high side of what ends up
Long term /Saturday through Tuesday/...
upper trough residing over eastern Continental U.S. Will keep unsettled weather
pattern over the region. Lack of strong forcing should result in
scattered to isolated convection until a cold front brings a better
chance for thunderstorms on Tuesday.
Main concern Friday and Saturday will be scattered thunderstorms
that may develop mainly in southern locations in the vicinity of a
stalled boundary. A better chance for thunderstorms is forecast for
Sunday when a rather large surge of moisture is shown to arrive
on a southerly low level flow. Expect a relative lull in convection
Monday when models indicate weak high pressure. Cold front could
bring another round of thunderstorms to most locations on Tuesday.
With lower than average 500 mb heights and the presence of clouds
and precipitation coupled with a lack of strong warm advection...expect
temperatures to be a bit below normal. Highs are forecast to be
around 80 each day...compared to normal highs in the middle 80s.
Aviation /12z Wednesday through Sunday/...
varying ceilings and visibilities will continue at the taf
sites...Sans kday...between 12z and 15z as fog/stratus exits
across the region. Conditions should improve to all VFR by 15z.
For later today...weak front should become quasi stationary near
the Ohio River while high pressure builds into the Great Lakes.
With the lack of strong forcing...am only expecting maybe a pop
up shower/storm in this location with just scattered to locally
broken cumulus clouds elsewhere. Winds will increase from the
northwest to around 10 knots.
For tonight...models continue to advertise a possible mesoscale
convective complex to dive southeast into the middle Ohio Valley.
Some return flow in response to this system may increase probability of precipitation a
little near the kcvg/kluk terminals between 06z and 12z.
Outlook...thunderstorms possible Thursday through Sunday.