Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 220536

Area Forecast Discussion
National Weather Service Wilmington OH
136 AM EDT Thu Mar 22 2018

Low pressure is moving east tonight, allowing high pressure and
a drier airmass to build into the region Thursday and Friday.
Low pressure will bring a mix of rain and snow to the region
for Saturday. High pressure and dry air are forecast to return
Sunday and Monday.


Surface analysis suggests a surface trough is currently over the
ILN CWA, extending from ESE-to-WNW, with a slight veering of
winds behind the southward-moving axis. Precipitation has
largely ended across the ILN CWA, with surface observations
showing that clouds remaining over the area are generally in the
mid-levels. The only exception, for the next hour or two, is the
chance for some light flurries or freezing drizzle in southern
Ohio / northeastern Kentucky, where a few pockets of low-level
moisture still exist. RAP projections (mainly at 900mb and
below) and a few light radar returns suggest this is the case,
and also suggest that it will come to an end soon.

A Special Weather Statement is in effect to highlight the
potential for refreezing tonight, as any wet roads will become
prone to becoming icy as temperatures fall into the 20s. The
main change for this evening forecast update was to drop
temperatures overnight, especially where the heaviest snow fell
earlier -- mainly in the western half of the ILN forecast area.
Temperatures were lowered by several degrees, especially as
clearing is beginning to work into the region from the west. In
fact, current HRRR/RAP runs suggest temperatures may fall even
lower than even in this updated forecast -- possibly well into
the teens. That is not out of the question given the
aforementioned conditions.

Previous discussion >
Surface analysis shows low pressure to the east and high
pressure to the west. ILN area is under a chilly northerly flow
between these systems. Moisture and forcing associated with the
low are diminishing and snow is ending. Still will see light
snow for a few more hours especially in eastern locations, but
little to no additional accumulation is expected. Clouds will
linger this evening until clearing from the west arrives
overnight with the high moving in. Temperatures will fall below
guidance to the lower 20s, with these cold readings aided by
snow cover.


Surface high pressure developing under a northwest upper flow
will extend across the area Thursday and Thursday night. This
will provide dry weather conditions and mostly clear skies
through the period.

Sunshine and modest warm advection will allow high temperatures
in the low to mid 40s, still close to 10 degrees below normal.


In a northwest flow aloft, our region will be between weak systems
to our northeast and southwest on Friday. Surface high pressure will
remain in place, and with sunshine, temperatures will warm into the

Focus then turns to a low pressure system forecast to pass southeast
through the lower Ohio Valley and the Tennessee Valley Friday night
into Saturday night. Strong ascent in the form of a moist low level
jet will spread precipitation east/northeast into the region Friday
night into Saturday. There is an increasing signal for an
accumulating snow event, perhaps significant, for locations along
and north of the Ohio River. Many factors will play in how much snow
will fall such as surface temperatures, thermal profiles, time of
day, exact track of the low, and whether some locations along and
north of the Ohio never mix with or change over to rain. We
currently have a mix developing north of the Ohio with rain/snow
changing to rain south of the Ohio. However, strong lift/dynamic
cooling, along with a prolonged easterly flow in the low levels, may
keep sounding profiles saturated near or below the 0 degree isotherm
for points along and north of the Ohio River. Also, the strong
vertical motion will likely occur in the favorable dendritic growth
zone which will result in aggregate snowflakes. These types of
snowflakes can result in heavy snow with rapid accumulation. So,
until confidence increases in ptype and duration, have initially
went with conservative in amounts, with the caveats mentioned above
that could result in a heavier, more significant snow. This has been
placed in the HWO.

By Saturday night, the low pressure system will be pulling away to
the southeast, allowing surface high pressure to build back into the
region for Sunday. After lows between 25 and 30, highs will warm
back into the 40s on Sunday.

High pressure at the surface and aloft will remain over the region
on Monday. Temperatures will continue to moderate with highs in the
upper 40s to the lower 50s.

For the remainder of the extended, an increasing moist, southwesterly
flow will develop around the mid level ridge axis passing to the
east. This will bring clouds and the potential for showers as we
head into Tuesday. A frontal boundary will try to make inroads into
the area by mid week, keeping the threat for rain in the forecast.
Temperatures will continue to warm with 50s and perhaps 60s possible
by next Wednesday.


Clearing line has pushed east of the western TAF sites and will
continue to work slowly east through the rest of this morning.
Until then though, some mid level clouds will persist at
KCMH/KLCK for the next several hours. We could see some sct cu
development late this morning into early afternoon, especially
across the eastern TAFs where there will be a little better
lingering low level moisture. Any cu should dissipate toward
evening with mainly clear skies overnight. VFR conditions are
expected through the TAF period.

OUTLOOK...MVFR/IFR ceilings and visibilities are possible
Saturday and Saturday night. MVFR ceilings are possible again on




NEAR TERM...Coniglio/Hatzos
SHORT TERM...Coniglio
LONG TERM...Hickman
AVIATION...JGL is the U.S. government's official web portal to all federal, state and local government web resources and services.