Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
134 am EDT Sat Aug 30 2014
a weak warm front will lift across the region tonight. A series
of upper level disturbances will then move through the region over
the next several days...resulting in a chance of showers and
thunderstorms through much of the Holiday weekend.
Near term /until 6 am this morning/...
isolated grouping of showers running north-northeast from kday will cross into
Hardin County before exiting the area. It will continue to weaken
as it moves north...noted by a decrease in overall coverage in the
past hour or two and lack of lightning which it did produce closer
towards the Dayton metropolitan area.
Being in the warm sector...bumped min temperatures up tonight by about 2
degree or so across the board.
Short term /6 am this morning through Sunday night/...
trough in the Central Plains will weaken as it moves into the
Great Lakes over the weekend. But this will suppress the southeast
US ridge and allow energy to lift out of the Gulf and move across
the Ohio Valley.
For Saturday better upper support will only be spreading into the
western counties. So chance for showers and thunderstorms will
primarily be confined to that area. Stronger forcing area wide
will overspread the entire region Saturday night and continue into
Sunday. Have stayed with high likely probability of precipitation for now given
uncertainties with placement of convection. Precipitable water
will be over 150 percent so there could be some respectable
rainfall totals. As stronger forcing moves off to the east later
Sunday...coverage of showers and thunderstorms will diminish.
While this may eventually result in a lull...the chance of
precipitation will linger through Sunday night with somewhat
higher probabilities in the east.
Precipitation and substantial lower cloud cover on Sunday should
keep temperatures from warming very much. Have used a MOS blend
leaning towards the cooler guidance. Otherwise warm and humid
conditions will prevail with forecast at or slightly warmer than
warmer MOS numbers.
Long term /Monday 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.
On Monday...our area will be in a relative lull in terms of precipitation
chances. Weekend system will have exited off to the east while a
cold front slowly approaches from the west. Diurnal heating with a
continued humid airmass may pop a shower or storm...particularly
during the peak heating of the day.
For Monday night into Tuesday night...aforementioned 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 /05z 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.