Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
145 PM EDT Wednesday Sep 2 2015
a departing upper level low will move southeast and away from the
Ohio Valley today. A somewhat nebulous high pressure area at the
surface will linger in the region through the end of the week.
Upper level ridging in the central portion of the country will
bring continued warm and humid conditions to the Ohio Valley
through the weekend.
Near term /until 6 PM this evening/...
scattered thunderstorms have developed across central Ohio this
morning in the wake of a departing upper level low but in an area
of weak low level convergence. Hi res models suggest these storms
will sag slowly southeast through the rest of this morning. As we
get into this afternoon and begin to destabilize...some
additional isolated thunderstorm development will be possible.
However...will keep probability of precipitation pretty low as forcing is somewhat
questionable as we will be on the back side of the upper low and
low level convergence remains fairly weak and across our north.
Highs will again be in the middle to upper 80s.
Short term /6 PM this evening through Saturday night/...
northwest flow aloft will then be found in the region as strong
ridging aloft in the central U.S. Strengthens through the end of
Temperatures will remain above normal in the upper 80s and
approach 90 in many spots...with dewpoints around 70. A
disturbance aloft will increase cloud cover Thursday night but is
not expected to be strong enough to continue any convection beyond
the early evening hours.
Friday and Saturday will be under similar conditions with the
remnants of the Thursday night disturbance undercutting the 500 mb
ridge in the central portion of the country...retrograding to the
southwest. Continued diurnally driven convection will occur with
warm and humid conditions through the period.
Long term /Sunday through Tuesday/...
while some of the specifics regarding the extended forecast remain
uncertain...the large scale pattern supporting above-normal
temperatures shows no signs of change through the weekend...with
only a slight trend toward the middle-level ridge breaking down going
into the first half of next week.
On Friday morning...the axis of a fairly strong ridge will extend
from the Texas coast north-northeast through the northern Great Lakes. At the
surface..the pressure pattern will be fairly nebulous...with weak
high pressure over the northeastern states. This will keep the Ohio
Valley in a regime of weak and moist low-level easterly flow through
the weekend. This is certainly a pattern that supports warm
conditions...and maximum temperatures in the upper 80s to around 90 are
expected. Gefs 850mb/700mb temperature and 500mb height anomalies
are not extreme...ranging from around 0.5 to 1.5 Standard deviations
above normal through the forecast period. This lends support to a
forecast for above normal temperatures...but not at the high end of
the climatological record.
With very little appreciable forcing...any chances for precipitation
will be limited. Between the GFS and European model (ecmwf)...the GFS has been a
little more willing to convect...but quantitative precipitation forecast output is not significant
in either case. A dry forecast will be maintained for most of the
forecast period...though slight chance probability of precipitation were kept in for Friday.
On Monday and Tuesday...there are signs that the ridge will begin to
flatten...though the extent and quickness that this occurs is not in
good agreement. As a shortwave moves across the north-central Continental U.S.
Going into Tuesday...eventually a cold front will develop and move
toward the Ohio Valley. How far this process gets is much too early
to forecast...but there is enough confidence to show a slight
decrease in temperatures and as light increase in probability of precipitation for
Aviation /18z Wednesday through Monday/...
isolated to scattered showers and thunderstorms have been pushing
very slowly southward across south central Ohio this afternoon.
Several outflow boundaries from these storms are evident on radar
and we are seeing some very isolated showers/storms popping up
along them. Meanwhile...the cumulus field has become a bit more healthy
looking elsewhere across the region so will go ahead and cover
the isolated thunderstorm threat with a thunderstorms in the vicinity at all the taf
Cumulus and any thunderstorm activity should dissipate this evening as
we lose the diurnal enhancement. This will allow for MVFR to IFR
br/fog development once again later tonight into Thursday
morning...especially at the more climatologically favorable
locations of kluk/klck and Kiln. In northwest flow aloft...short
wave energy will drop down toward the area through the day on
Thursday. This will lead to a chance of showers and thunderstorms
toward the end of the taf period...with the best chance being at
the northern taf sites.
Outlook...no significant weather expected.