Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
923 PM EDT Tuesday Jul 22 2014
an approaching cold front will continue to keep southwest winds
and humid air over the Ohio Valley ahead of it. This front will
push through the region Wednesday and spark a round of showers
and thunderstorms. A large area of high pressure will build behind
it and provide dry and cool weather through the end of the work week.
Near term /until 6 am Wednesday morning/...
diurnal cumulus have dissipated across the area with skies currently
mostly clear. We should see an increase in high and middle level
clouds as we head into the overnight hours as a cold front
approaches from the northwest. A narrow line of showers and
thunderstorms currently along the front stretching from southern
Wisconsin into lower Michigan will continue to work its way
southeast toward our area overnight. The hrrr continues to suggest
that some of this could make it down into our northwest forecast area through
the early morning hours...while the arw and nmm weaken and
dissipate the storms as they move into our area. Will continue with
some lower chance probability of precipitation across the northwest to account for the
possibility...but with decreasing instabilities...do expect a
general weakening trend to any thunderstorms that do make it into
our forecast area.
Short term /6 am Wednesday morning through Thursday night/...
cold front is being prognosticated with a continuously faster solution
with each model run. In the northwest County Warning Area at 12z it is well southeast of
the I-71 corridor by 18z. Precipitation in the cold pool behind the wind
shift will be hard pressed to see damaging winds with any
convective elements and the swody2 outlook appears to whittle away
at the severe prospects with each discussion. At this moment...I
would expect a rainy period with thunder but the lack of distinct
strong cores/updrafts necessary for wind/hail. Elevated
instability will make for occasional downpours and winds when
these elevated cores collapse...but the expected high moisture and
cold nature of the air in the boundary layer would limit any very
strong winds from occurring.
Highs were prognosticated to be a bit warmer than I would expect in the
southeast with a grungy day of cloud cover. Lowered readings a bit
to top out at 90 degrees as a maximum and think that this would be
an early afternoon high with strong advection from a sunny pocket
over Kentucky being pulled into my northern Kentucky and southeastern Ohio counties. Northwest County Warning Area
will be thoroughly grunged and not reach past the 70s.
After precipitation ends tomorrow night...high pressure will push in
drier and cooler air to the Ohio Valley and this will remain in
place through the end of the work week.
Long term /Friday through Tuesday/...
surface high pressure will be centered across the Ohio Valley on
Friday. This high will quickly slide southeast of our region and
weaken as an upper level disturbance embedded in northwesterly
flow approaches our region. Models have accelerated the arrival of
this disturbance...yet still vary by several hours on their
forecast arrival of precipitation on Saturday. Added low chance
probability of precipitation early Saturday morning with probability of precipitation ramping up into the day
Saturday based on the faster trend. Kept only chance probability of precipitation on
Saturday due to timing and coverage uncertainties for
precipitation on Saturday. Temperatures under the high on Friday
will remain a few degrees below normal. Once the high shifts to
our southeast...a rebound to near normal temperatures can be
expected for Saturday.
On Sunday...a unseasonably deep trough is expected to dig
southeastward across the middle west and into the Ohio Valley. Low
pressure downstream of this trough will drag a cold front across our
area. The CMC and GFS are in fairly good agreement on bringing
enhanced chances for precipitation to our area on Sunday ahead of
this front...with the cold front crossing our area at some point
late Sunday. Best chances for precipitation appear to be during the
day Sunday in the warm sector...with cooler air moving into the
region by Monday. The trough is forecast to remain in the region
through the early parts of next week. Models vary on how much
moisture lingers behind the front. Am forecasting mainly low chance
diurnally driven showers and isolated thunderstorms in the cold
sector. This high amplitude trough will bring another round of well
below normal temperatures to the Ohio Valley early next week...with
current indications being that highs may only reach the lower 70s on
Monday and possibly again on Tuesday.
Aviation /01z Wednesday through Sunday/...
diurnal cumulus will continue to dissipate through middle evening..leaving
mainly clear skies heading into the overnight hours. A cold front
will drop down from the northwest late tonight and push across the
taf sites later Wednesday morning into early afternoon. Convection
currently associated with the front is still well off to our
northwest. This will sag southeast toward our area tonight with
some of the hi res convective models suggesting some of it will
hold together as it works into our northwest late tonight.
However...instability will be decreasing through the overnight
hours...so would expect to see a weakening/dissipating trend if it
does make it all the way down into our area. Will therefore allow
for some increasing middle/high level clouds late tonight and then
generally cover the initial thunderstorm threat with just a thunderstorms in the vicinity.
More widespread thunderstorm activity should then fire up along
the front as we destabilize heading into Wednesday afternoon. The
best chance for this will be just southeast of the I-71 corridor
and generally southeast of the taf sites. As a result...will just
have a p6sm -shra and thunderstorms in the vicinity into early to middle afternoon for the taf
sites along the I-71 corridor.
Outlook...thunderstorms possible Saturday and Sunday.