Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
649 PM EST Sat Dec 21 2013
a nearly stationary frontal boundary will continue to be the focus
for heavy rainfall through tonight. Low pressure approaching the
region will push the front across our area as a cold front
tonight...bringing with it a chance for severe weather. Cooler
conditions are expected behind the front to start the week.
Near term /until 6 am Sunday morning/...
sharp surface front is beginning to lift northward with heavier
precipitation ending across the southern two thirds of the area
this afternoon. This trend is expected to continue through the
remainder of the daytime and into the early evening as the
majority of the County Warning Area sets up in the warm sector. Current thinking
is that the northwestern zones will continue to see steady
precipitation for the next several hours...with intermittent
lighter rain for the remainder of the zones. Flooding will
continue to be a threat across the area with earlier snow
melt...departing and ongoing areas of rainfall...and forecasted
additional heavy rain overnight. Will therefore continue the Flood
Watch through the overnight time period for all zones.
A surface low developing along the frontal boundary will lift
northeastward from Texas/Arkansas and arrive in the Ohio Valley tonight.
Ahead of the is low...warm/moist air will continue to be drawn
north into the Ohio Valley with dewpoints reaching the lower 60s
south of the frontal boundary and precipitable waters nearing or breaking record
values for December. This moisture surge ahead of the low will
allow for high rain rates with any precipitation occurring this
evening and tonight as the low tracks across the region.
Out ahead of this low...a qlcs/squall line type of feature that is
developing across the lower Mississippi Valley will track
northeastward...affecting most locations in the warm
sector...which will include the southern two thirds of the iln
County Warning Area. Wind shear will be supportive of damaging wind gusts and
isolated tornadoes late this evening as this line approaches from
the southwest...with the timing of the highest threat for severe
in the iln County Warning Area being between 10 PM and 3 am. Heavy rainfall and
flooding will be a threat throughout the night as a large swath of
moderate to heavy rain will accompany the qlcs and areas north of
the qlcs. This will likely worsen existing flood issues and create
new flooding issues across the area.
In addition to the potential for significant flooding tonight and
the window of opportunity for severe weather late this
evening...sustained southerly winds will increase to 20 to 25 miles per hour
with gusts up to 35 miles per hour ahead of the main line of convection
By the end of the overnight period...rain is expected to taper off
in the western zones...with the main band of precipitation
associated with the cold front beginning to exit our eastern
Short term /6 am Sunday morning through Monday night/...
the low will continue to track northeastward and away from the iln
County Warning Area on Sunday. Cold advection will develop and bring in cooler air
throughout the remainder of the short term period.
Showers will be possible Sunday evening through Monday across the
area as an upper trough digs southeastward toward the Great Lakes
with a weak trough helping to produce mainly rain across the
southeastern zones and snow showers across the northwestern zones.
Eventually...any lingering showers will be all snow as sufficient
cold air moves into the region. At this time...little to no snow
accumulation is expected from snow showers that may occur during
this time period.
Long term /Tuesday through Saturday/...
given short term concerns...not much time spent on this timeframe.
This period characterized by longwave ridging near/off the West
Coast of the United States which supports troughing in the northeast
Continental U.S.. this is a below-normal temperature regime for the Ohio
Valley...and have derived maximum/min temperatures first from an European model (ecmwf)/ensemble
MOS and adjusted from there to meet deterministic thoughts on
advection. Really no significant weather systems in this
regime...the only appreciable chance at precipitation comes with a
weak system on Tuesday and Thursday...but these are minor threats at
best as being depicted in the 21.12z European model (ecmwf)/GFS models at this time.
Suppose there is a potential for a lake-induced snow shower threat
in the cold advection behind either system...but those mesoscale
process are not well defined at this time range this far from the
Aviation /00z Sunday through Thursday/...
MVFR to occasionally IFR conditions were occurring this evening
associated with a low pressure system and attendant warm front and
cold front. Showers associated with this system continued to sweep
across the taf sites from the SW to NE this evening. Expect showers
to continue through tonight in this very moist regime and end from
the west Sunday morning. Winds will generally remain out of the south
with gusts over 20 knots tonight as the front moves closer and the
pressure gradient tightens. Possibility exists of a squall line of
thunderstorms with the cold front. Included thunderstorms in all
taf sites except kcmh and klck after 02z to 04z for several hours.
Less likely to see thunder as far north as kcmh and klck but will
monitor conditions. Conditions should improve to MVFR on Sunday
with winds shifting to the west later Sunday afternoon. Possibility
of wrap around showers after low pressure system exits region
Sunday but since that is toward the end of the taf period any
forecast of showers was left out.
Outlook...MVFR ceilings expected to linger Sunday night into
Ohio...Flood Watch through Sunday morning for ohz026-034-035-042>046-
Kentucky...Flood Watch through Sunday morning for kyz089>100.
In...Flood Watch through Sunday morning for inz050-058-059-066-