Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
741 PM EDT Tuesday Sep 2 2014
a weakening cold front will move into the region
tonight...dissipating over the Ohio Valley by Wednesday morning.
An area of high pressure will build in behind the front...with
drier conditions expected through Wednesday night. A rise in
moisture will begin again on Thursday and Friday...with chances
for storms increasing through Saturday.
Near term /until 6 am Wednesday morning/...
a weak and ill-defined cold front is currently moving into the iln
forecast area. Msas pressures and current surface wind analysis do
not do much to indicate the location of the front...but the
instability gradient is a little more well-defined. Rap/NAM
Theta-E projections show a marked boundary over the forecast
area...with lower values already entering Northwest Ohio and most
It is only in the area where the greater and deeper moisture
content still remains that convection of any consequence will be
able to develop. The most intense storms are developing over the
lmk/jkl forecast areas...but radar trends indicate an gradual
increase in the strength of the storms over southern Indiana.
These storms will likely track across the southern third of the
iln forecast area...moving into an environment of 1000-1500 j/kg
mixed layer cape...and deep layer shear of around 40 knots. The
weak forcing and current storm morphology seem posed to keep the
severe threat low (one or two strong storms will be
possible)...but the orientation and atmospheric moisture content
suggest there may be a heavy rain threat along west-southwest-to-ENE axes.
Likely probability of precipitation have been used in the southern County Warning Area this evening. Slight
chance probability of precipitation were included through the entirety of the forecast
area...with several light showers near Interstate 70...and a few
other echoes showing up in northern Indiana. Though the greatest
deep moisture will be moving away...surface dewpoints will only
drop slightly...and patchy fog near sunrise will be possible
under clearing skies and light winds.
Short term /6 am Wednesday morning through Thursday night/...
weak high pressure will move into the County Warning Area on Wednesday. This high
is not the cleanest of highs...with moisture passing through at
various levels. In fact...the NAM and Storm Prediction Center-WRF both show the
development of a few showers...which seems unlikely given the weak
ridging over the area and loose surface pressure pattern.
The switch to southerly flow will begin on Wednesday night (and
especially on thursday). Most of the models are indicating northern
stream convection getting very close to the northwestern County Warning Area early
on Thursday...decaying as it runs into the departing surface high.
A 20-pop will be kept in the area to account for this potential.
Otherwise...conditions should remain dry for another day...at
least until late Thursday night.
Although dewpoints on Wednesday and Thursday will be a little
lower than Tuesday...temperatures under clearer skies will be
warmer...with lower-to-mid 80s on Wednesday and middle-to-upper 80s
Long term /Friday through Tuesday/...
a cold front will approach and move through the area Friday into
Friday night. In advance of this feature expect warm conditions
across the area on Friday with high temperatures in the upper 80s to
around 90. Showers and thunderstorms will move into the area on
Friday and become more widespread Friday night.
An upper level disturbance will move through on Saturday allowing
for additional showers and thunderstorms. Precipitation is expected
to taper off Saturday night. Cooler conditions will be in place on
Saturday with precipitation across the area.
Cooler and dry conditions will be in place for Sunday and Monday
with high temperatures in the 70s. Southerly flow will allow for
slightly warmer conditions on Tuesday with high temperatures in the
Aviation /00z Wednesday through Sunday/...
skies will clear early in the taf period with winds becoming
light. Appears to be a good situation for fog development. Have
continued with visibility restrictions at all sites. Expect to
fall to LIFR at the usually more fog prone terminals. Visibilities
will quickly improve after 12z. May see few to scattered cumulus
during the day with light southerly winds.
Outlook...thunderstorms possible Friday into Saturday.