Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
1047 am EDT sun Sep 21 2014
a cold front will move southeast through the Ohio Valley today...as
an area of upper level low pressure crosses the Great Lakes. Behind
the front...cooler and drier conditions will build into the region
for Monday. An area of high pressure will persist over the Ohio
Valley through the week...with dry conditions expected through the
weekend...and a gradual warming trend.
Near term /until 6 PM this evening/...
NE-SW oriented cold front is traveling across the iln area. Only
isolated showers remain in eastern counties. Isolated showers
associated with an upper low may move back in from the northwest
this afternoon. Otherwise expect partly cloudy skies.
Temperatures have started out warm but diurnal warming will be
countered by cold advection behind the front...and highs will
be only a few degrees above current readings in the lower 70s.
Models indicate sustained winds close to 20 knots this
afternoon...with gust to 30 knots. Have increased forecast winds
Short term /6 PM this evening through Wednesday/...
by evening...the surface cold front is expected to be through the
iln County Warning Area. However...the axis of the 500mb trough will be rotating
through the Great Lakes. There is a significant increase in model
relative humidity in the low levels tonight...and it is likely that a
stratocumulus deck will envelop the iln County Warning Area from north to south.
The WRF-nmm / WRF-arw models are in agreement with CMC/GFS
guidance in allowing for some light showers to develop in the
northern half of the County Warning Area this evening. Slight chance probability of precipitation have
been maintained in the forecast for this...though there was some
consideration to increase probability of precipitation (keeping quantitative precipitation forecast light) in the far
north. Though cold advection tonight will be notable...the clouds
may actually keep temperatures from plummeting too far.
After the clouds dissipate (perhaps not all that quickly) on
Monday morning...a very tranquil weather pattern will begin to set
up for the rest of the week. A sprawling area of very dry high
pressure will get caught under a middle-level ridge...between the
quick upper flow in Canada and the very stagnant tropical
conditions well to the south. The air mass will also start out
rather cool...with 850mb temperatures of below 5 degrees celsius on
Monday morning. Although the trend through the week should be for
a gradual warming trend...as the center of the high very slowly
moves east of the Ohio Valley...it appears that Monday night /
Tuesday morning will likely be the coolest. Under clear skies and
light winds...min temperatures look to be in the lower 40s...about 10-15
degrees below normal. Record lows at the climate sites are well
into the 30s and should be easily safe...but outlying locations
may drop into the upper 30s.
With no change to the pattern heading into Tuesday and
Wednesday...the forecast is fairly straightforward...with slight
increases in temperatures each day and sunny skies expected.
Long term /Wednesday night through Saturday/...
middle/upper level ridge will remain in place across the region
through the end of the week. This will result in dry conditions and
fairly seasonable temperatures through the long term period. As the
airmass slowly modifies...high temperatures will gradually warm each
day...from the low to middle 70s middle week into the upper 70s to around
80 degrees by the weekend.
Aviation /15z Sunday through Thursday/...
cold front will move southeast through the forecast area late
this morning and early this afternoon. Radar shows a band of
widely scattered showers ahead of the front extending across
southern Indiana northeastward towards cmh. The band is moving to
the east and weakening. These showers are expected to move through
the terminals by 12z thus will not be included in the 12z tafs.
Behind these showers leading back to the front will be band of low
level moisture generating ceilings between fl015 and fl025. Ahead of the
front surface winds will be SW 10 to 15 with a few gust to 20kt.
After frontal passage winds will turn to the west and gradually northwest at 15 to
20kt with gust 25 to 30kt. MVFR clouds associated with the front
are expected to clear the area by noon leaving scattered SC between
040-050. Low level moisture associated with an upper level trough
will move into the forecast area late afternoon and produce ceilings between
fl040 and 050. These clouds could produce a few sprinkles north of
I-70 and have not been included in the forecast. As the upper level trough
moves to the east of the area late tonight and early Monday morning
skies should clear. During the night winds will be northwest and lose
Outlook...for Monday through Thursday...VFR.