Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
347 am EDT Sat Aug 30 2014
a series of upper level disturbances will move east across the
region through early next week...resulting in a continued chance
Near term /through today/...
weak low level convergent boundary has lifted off to our north
early this morning. This has allowed for very isolated
shower/thunderstorm activity to come to an end across our forecast area for
the time being. In a continued warm air advection/isentropic lift pattern...precipitation
chances will increase through this afternoon as we destabilize.
However...precipitation coverage will primarily hinge on how fast we begin
to see the influence of the combination of some short wave energy
moving across the lower Great Lakes along with some additional
energy lifting up from the southwest. There is some model
uncertainty as to how fast this will happen today but most of the
convective allowing models are suggesting at least some isolated
to scattered activity working into our western areas later this
afternoon. Will therefore go ahead and allow for chance probability of precipitation to
spread in from the west later today. Increasing clouds from the
west may help moderate temperatures somewhat and will range highs
from the middle 80s west to around 90 in the east.
Short term /tonight through Monday/...
the middle/upper level trough moving out of the middle Mississippi
Valley will weaken as it progresses east across the upper Ohio
Valley tonight through Sunday. As it does...the flow aloft will
transition into more of a zonal flow pattern with a series of upper
level short waves moving east across our area tonight through
Sunday. This will lead to an increasing chance of showers and
thunderstorms tonight...especially across southern and
southeastern portions of our forecast area...where a developing 925-850 jet
will nose in from the south later tonight. Fairly high precipitation
chances will continue into Sunday as moist southwesterly low level
flow persists. It looks like we may get into a bit of a lull
Sunday night into Monday morning as better short wave energy
pushes off to the east. As we destabilize through the day on
Monday...some isolated thunderstorm activity will again be
possible...especially during the afternoon hours. Clouds and precipitation
should help keep highs generally down in the lower 80s for
Sunday...with temperatures then warming back up into the middle 80s
Long term /Monday night through Friday/...
have used a blend of the 00z European model (ecmwf) and the 12z European model (ecmwf) for the long
term forecast. Each model run was similar to each other with timing
and placement of upcoming synoptic systems. Also..the GFS seem too
fast in pushing a warm front back northward middle week based on middle to
upper level flow.
For Monday night into Tuesday night...a cold front will slowly
sag southeast into the region...eventually stalling out somewhere
over the central or southern County warning forecast area by Wednesday morning. Best upper level
dynamics pass by to the north on Tuesday afternoon and evening.
However...enough heating and frontal convergence call for at least
40 to 50 probability of precipitation.
On Wednesday...frontal boundary as mentioned is expected to stall
over the area while middle level flow begins to buckle a little. Will
continue with a low chance for showers/storms...mainly central and southern
sections through Wednesday afternoon/early evening.
Looks like middle level ridge to our south will try to build northward
Thursday into Friday ahead out ahead of the next shortwave and cold front
to move into the region by the weekend. Have kept Thursday dry in
the moist return flow although there is a very small chance for a
pop up shower or storm. Have gone with 20 and 30 probability of precipitation on Friday
ahead of the approaching cold front.
Temperatures through the period will be near or above seasonal
normals for early September.
Aviation /07z Saturday through Wednesday/...
current satellite imagery shows a band of scattered to broken middle and
hi clouds extending southwestward across Ohio and are associated with
a warm front. These clouds are moving north and should be north of most
of the taf sites by 08z leading to clear skies. Expect VFR conds
except for some MVFR to locally IFR along the Ohio River and
occasionally impacting kluk.
Reviewing some of the latest numerical guidance has showed that
the precipitation will not be as widespread during the daylight hours as
earlier thought. This has allowed for the reduction from tempo ts
to thunderstorms in the vicinity. Also since low level moisture will be further north have added
thunderstorms in the vicinity to the kcmh and klck. Not much change needed for the
remainder of the forecast at this time. The better chances for
storm development will occur as the surface low pressure center
treks towards Ohio/in/KY Sunday morning.
Surface winds have been increase and are now forecast to be SW 5
to 15kt with gusts to 20kt during the daytime hours.
Outlook...scattered thunderstorms possible through Wednesday.