Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
408 PM EDT Tuesday Jul 26 2016
a stalled frontal boundary along or south of the Ohio River will
continue to be the focus of thunderstorm activity through
Wednesday night. On Thursday, an upper level wave will cross
northeast and into south central Ohio, sparking more widespread
activity. This upper level feature will cross east overnight and a
trailing surface low on Friday will mark a slight decrease from
this activity starting Friday night as high pressure builds north
of the region.
Near term /until 6 am Wednesday morning/...
widespread showers over southeastern County Warning Area and a trailing chance of
more stratiform rain with significantly less coverage to the
north and west of it will continue to decrease this afternoon.
This decreasing trend should persist into the evening and
overnight hours, but given high pwat values being continually
pumped into the region, we cannot in good conscience remove pops
entirely from the overnight period for the southeastern half of
the County Warning Area. The high pwat values will remain over the surface
boundary laid out along the Ohio River, and zonal 500 mb flow that
will permit weak vorticity maxima to potentially continue ongoing
convection or less likely help spark new isolated storms
Temperature guidance has been consistent overnight with relatively
steady mins within a degree or two of 70.
Short term /6 am Wednesday morning through Thursday night/...
Wednesday will see any ongoing convection from overnight storms
decrease early given an expected unsupportive diurnal trend. There
may however be lingering showers along and especially south of the
Ohio River given the continued stalled surface boundary and
continued influx of moist air from the low and mid atmospheric
All of the models are showing a marked decrease in coverage during
the day Wednesday with the highest potential laying out over
northern Kentucky. Overnight Wednesday may see an increase in
storms but the feature initiating any overnight convection appears
muddled and highly dependent on a more distinct surface feature
which does not seem a likely scenario at this moment in time.
Thursday will see a marked increase as most of the models are
keying off of a vort Max streaming NE ahead of an upper level S/W
and combining with daytime insolation.
Have increased pops Thursday and really ramped them up in the
southeast where all indications show continued storms - similar
to what is occurring at this moment in time. Given this, have
lowered Max temps in the southeast to just lower 80s, and could be
even lower depending on where and how long rainfall occurs.
Outside of the Max temps being lower in the southeast on Thursday,
numerical guidance were all within a degree or two of each other
for the climatological stations for any given period. It did not
appear to be a large change from what was already in the
Storms for any period along and south of the Ohio River will have
a potential to include very heavy rainfall and an increased threat
for flooding given the continued feed of moisture to the region in
question. Strong winds will remain a lesser yet still viable
threat, and large hail chances appear minimal through this time.
Long term /Friday through Tuesday/...
the long term will start with a series of upper level
disturbances moving across the area along with a front stalled
out. This will help to keep the chance of rain in the forecast
almost through the entire extended until Tuesday when weak mid-
level ridging moves into the region.
Looking more into the details, Friday will open up with a shortwave
moving across the region and the leftover frontal boundary from
earlier in the week still across the area. Upper level lift is
sufficient with weak positive vorticity advection moving across and moisture values remain
above average for this time of year with pwats forecasted to be
around 1.70". Instability is also present with ml cape values around
500 j/kg. As the shortwave exits Friday pops will slowly taper off
due to weak subsidence behind the wave.
Saturday through Sunday another weak shortwave trough will remain in
close proximity to the area with a surface front located across the
County Warning Area. This will help to bring the chance of rain right back to the
area. Given the weak upper level trough quickly pulling east the
cold front stalling across the area seems likely. Given the chance
of showers and thunderstorms during the day have kept high
temperatures near climo. Monday into Tuesday as the shortwave trough
exits weak mid-level ridging will then build overhead as mid-level
high pressure builds over the central United States. There still
remains timing differences on when the high will build and how far
it will build east. For now have just trended pops down.
Aviation /20z Tuesday through Sunday/...
thunderstorms and rain have developed over cvg/luk near a stalled frontal boundary.
Expect those 2 locations to be affected by the thunderstorms and rain for the first
couple of hours of the period with MVFR/IFR vsbys. After that
thunderstorms and rain will be scattered across srn Ohio and nrn KY, so transitioned to
a thunderstorms in the vicinity.
Up at Kiln, a MVFR cigs on the nrn edge of the convection has
worked in. As the convection works NE, it could brush iln. Only
went with thunderstorms in the vicinity for a few hours to cover the threat. Day could get
nicked by a VFR shower, but expect cmh/lck to remain dry.
Model trend is for the convection to weaken and dissipate with the
loss of daytime heating, so have the tafs dry overnight. With
lingering dewpoints in the 70s at the srn tafs, kept the mention
of some fog overnight.
Scattered convection should pop up again tomorrow, so have thunderstorms in the vicinity
in the cvg 30 hour taf.
Outlook...thunderstorms possible Thursday afternoon through