Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
749 PM EDT Thursday Aug 28 2014
high pressure will move off to the east allowing a weak warm front
to lift across the region late Friday into Friday night.
Increasing moisture along with series of upper air disturbance
will result in a chance of showers and thunderstorms through much
of the Holiday weekend.
Near term /until 6 am Friday morning/...
high pressure centered over Michigan will drift east overnight.
Cumulus will dissipate with loss of heating. But some middle clouds
may spread in from the west. Relatively dry air mass will allow
lows to fall to or slightly below normal except in the tri-state.
Short term /6 am Friday morning through Saturday night/...
given current sky conditions and models showing significant 700 mb-500 mb
moisture over the region...it appears the higher humidity air in
the middle levels of the atmosphere are not conducive to producing
cloud cover in and of itself. A lifting mechanism needs to
condense this moisture and it is apparently not happening with the
axis of the upper ridge extending northwest from eastern Kentucky.
Adjusted sky cover downwards a good bit later tonight.
Temperatures over southwest County Warning Area were a bit warmer than would be
expected with a generally clear sky and light east wind. Did not
adjust downward enough with first evening update but believe the
second evening update will show a decrease over metropolitan cincy and
northern Kentucky counties.
Long term /Sunday through Thursday/...
models are in fairly similarly agreement through Tuesday morning.
Thereafter...there are some big differences. Have taken a blend
of the 12z European model (ecmwf)/GFS through Tuesday...with a heavier weight toward
wpc guidance given the Stark differences in the operational models
by middle to late next week.
On Sunday...shortwave will move northeast through the remainder of the
middle and upper Ohio Valley while shortwave over the Great Lakes moves
northeast along the St. Lawrence River valley. Showers and embedded
thunderstorms are expected to be ongoing Sunday morning...with a
gradual decrease in probability of precipitation through the day. Temperatures will be held
down by clouds and precipitation...with lower 80s expected.
For Sunday night into Monday...another shortwave is forecast to skim by
to our southeast while stronger energy and a cold front push east
into the western Great Lakes. Moist south to southwest flow will
continue. We will be in a relative lull...but with instability and
moisture will hold on to a 30 pop region wide.
For Monday night into Tuesday...this is where the models are in
agreement for the last time. Shortwave energy is forecast to push
east/northeast across the northern Great Lakes into southeast
Canada. This should nudge aforementioned cold front into the area on
Tuesday. Will maintain a chance of showers and thunderstorms.
For Tuesday into Thursday...models disagree on the strength and
timing of shortwave coming out of the Pacific northwest into either the northern plains
or south central Canada. The European model (ecmwf) is more north and muted with this
energy. This solution hangs the frontal boundary over the region and
eventually pushes it back northeast as a warm front on Thursday as
middle level ridge to our south tries to establish itself once again.
The GFS is stronger and much farther south with the shortwave energy
which results in a cold frontal push through the region Wednesday
into Thursday followed by high pressure in its wake. Have sided more
with the GFS at this time which is more in line with wpc guidance.
However...given such big differences...adjustments will have to be
made with later forecasts in hopes the models come more into
High temperatures through the period will be close to seasonal
normals with lows averaging near or slightly above normal.
Aviation /00z Friday through Tuesday/...
VFR conditions will be found over the region with some high clouds
passing over the region during the day Friday. East to southeast
winds will be under 10kts. The higher clouds will skirt from
northern Illinois to lower Michigan and see its southern extent
touch the Ohio Valley as it crosses further northeast.
Outlook...scattered thunderstorms possible on Saturday through