Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
732 PM EDT sun Aug 30 2015
a warm and humid pattern is becoming locked in across the Ohio
Valley through the upcoming week...with little threat for
meaningful rainfall beyond isolated to scattered showers and
storms focused in the peak heating of the afternoon waning by
early to middle evening. Temperatures into the middle and upper 80s
are expected into next weekend. The better chances of isolated to
scattered storms appear to be focused on Monday and Tuesday across
central Ohio...before the threat appears to diminish somewhat
toward the middle and end of the work week.
Near term /until 6 am Monday morning/...
isolated showers/storms have developed amidst robust instability
/MLCAPE from 1500 to 1750 j/kg owing to surface dew points in the
upper 60s to around 70/ and very weak shear. Kiln vwp and
objective analysis indicates effective shear around 10-15kts
meaning these updrafts will behave in very pulsey fashion through
the remainder of the day into the early evening. While an isolated
wind gust to 50 miles per hour is a possibility /given dcape approaching
1000 j/kg/ this would only occur with the most intense
cores...which will be tough to come by given the weak flow/weak
lapse rate environment.
Expect activity to continue to be loosely focused due to the
absence of surface boundaries...and various weak vorticity maximum
wobbling through the weak flow underneath broad longwave ridging.
Main threats outside of a localized strong wind gusts will be very
localized heavy rain with the slow moving storms...or any brief
cell mergers which prolong the duration of intense rain. With precipitable water
only around 1.40" - rainfall efficiency is not overly high and dry
air entrainment should lead to storm collapse/cold pool
propagation with time. Lows tonight in the middle 60s and perhaps
some fog later in the night...likely confined to the fog prone
river valleys and low lying areas. Rain chances slowly wane
through the evening.
Potent upper trough shown nicely in GOES water vapor loops
ejecting through Georgia this afternoon will shear/accelerate
northeast through the middle-appalachian region overnight and may
brush south-central Ohio/northeast Kentucky with some light rain
potential later tonight - so lingered the threats a little later
Short term /6 am Monday morning through Tuesday night/...
complex...positively tilted weakness in the middle/upper level
height field within a broad/strong longwave trough will continue
to plague the region through Tuesday. There are numerous small
scale vorticity maximums forming within and retrograding
southwestward within this height weakness...and despite the
sheared/weak appearance of these features there/S enough forcing
to keep at least a small /isold/sct/ threat for diurnally enhanced
showers and storms across the Ohio Valley both days. This will be
augmented by seasonally warm/moist airmass with dew points in the
middle/upper 60s and temperatures in the middle/upper 80s. With such
weak flow...storms will be slow moving and won't move much beyond
their initiation...which admittedly could be over a large area
given a lack of boundaries in the lowest 3km of the surface. So
will continue to run with 20-30% rain chances mainly near the middle
level shear zone/height weakness which orients across wcntl/cntl
Ohio primarily and into adjacent areas of southern Ohio and southeastern Indiana.
Expect most areas will remain dry...but Don/T expect radar to be
echo-free either afternoon/early evening. No real weather hazards with
these storms /localized wind gusts to 40 miles per hour or so/ and isolated
heavy rain totals given the slow/wayward motions.
Expect activity to have a diurnal maximum/minimum so kept rain chances
out of the forecast during the nighttime hours. Temperatures seem
pretty straightforward both days...middle/upper 80s by day and
middle/upper 60s by night.
Long term /Wednesday through Sunday/...
numerical model solutions generally similar with mainly dry and warm
weather through the long term forecast period.
Weak middle level shortwave to top ridge axis and move through the Ohio
Valley early Wednesday. Have included slight chance probability of precipitation in the east
early Wednesday and then dry the area out as the short wave shifts east. Warm
temperatures to continue with highs on Wednesday in the middle/upper 80s.
Middle/upper level ridge axis over the nations middle section building east
into Great Lakes/Ohio Valley by next weekend. This ridge will act to
inhibit widespread thunderstorm activity due to a lack of enhanced
forcing. Can not rule out diurnally driven isolated convection but due
to limited coverage and probability...at this time have opted to
keep the forecast dry from Thursday through next weekend.
Above normal temperatures to continue with highs generally in the
middle and upper 80s. A few spots will likely hit 90 over the south and
Aviation /00z Monday through Friday/...
storm coverage and intensity is now on a downward trend...which is
expected to continue through the rest of the evening. An isolated
shower or storm near the Dayton and Columbus taf sites will remain
possible for another couple hours...and it would be impossible to
completely rule out a shower or two during the overnight hours.
The moist air mass will be supportive of some MVFR (to possibly
ifr) visibility restrictions near morning.
Storm chances for Monday appear a little less than they were
today...though still enough to support a vcsh in the tafs. Winds
will be very light through the rest of the period...and generally
out of the southwest.
Outlook...no significant weather expected.