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Area forecast discussion 
National Weather Service Wilmington Ohio
952 PM EST Tuesday Nov 25 2014

Synopsis...
high pressure will continue to extend into the region into
Wednesday. A clipper will pass just south of the area Wednesday
night. High pressure will slowly build in late in the week.

&&

Near term /until 6 am Wednesday morning/...
forecast area will be under the influence of surface high pressure
overnight as coastal storm organizes off the Carolina coast.
Latest rap and NAM-WRF suggest that increasing divergence aloft
from the right rear quadrant of a strong upper level jet combined with middle
level deformation will spread precipitation northward on the back side of
this low across the southern and central Appalachians. This precipitation shield
should remain just east/southeast of our far southeast zones by morning.
Much of the area will be mostly cloudy due to increasing middle level
cloudiness. The northern and northwestern zones will be cloudy as low level
moisture remains trapped underneath a subsidence inversion with
high pressure overhead. All in all...the forecast will remain
dry...and with persistent clouds...temperatures will not fall that
much from current readings. Lows will range from the middle 20s northwest to
the lower 30s southeast.

&&

Short term /6 am Wednesday morning through Thursday night/...
high pressure will get pinched off between large low pressure
system on the East Coast and an approaching clipper. Synoptic
models suggest that precipitation from the former could affect
far southeast counties. However high resolution runs keep it
further away from the forecast area. Have opted to continue with a
dry forecast for Wednesday. Could be a good deal of cloud cover
though as there is some potential for low clouds to redevelop
across parts of the area and then high clouds from both low
pressure systems.

Clipper will dive into southern Illinois by Wednesday evening and
then make the turn east near the Kentucky-Tennessee border. Cannot
rule out some light snow occurring along and south of the Ohio
River. But probability continues to look rather low.

In the wake of the clipper a second short wave on a more northerly
track will pass across the Great Lakes. Any precipitation with
this will stay north of the forecast area. But surface winds will
briefly become favorable off Lake Michigan. So there will be a
chance of snow showers in the northern counties. High pressure
will finally start to build in Thursday night with clouds
diminishing.

For the most part used a MOS blend for tempera Tuesday with the
exception of Wednesday night when warmer numbers were favored.

&&

Long term /Friday through Tuesday/...
surface high pressure will be centered over the Ohio Valley and
southeastern states on Friday morning. The upper-level pattern will
feature west-northwest flow across a large portion of the
country...with gradual height rises over the iln forecast area. An
area of weak isentropic lift will pass through the southern Great
Lakes as warm advection begins aloft. For now...any precipitation
(likely to fall as snow) appears that it will remain across northern
Indiana and Northern Ohio.

Although warm advection will occur at the surface heading into
Saturday...model soundings suggest that an inversion and relatively
thick layer of moisture will keep things from becoming well mixed
below 5000 feet. Even as most of the column will remain quite
dry...cloudy conditions with low ceilings appear fairly likely...and
there is even widespread model agreement in light precipitation
beginning by Saturday evening (somewhat unusual for what looks like
a drizzly profile). With warm advection and plentiful cloud
cover...min temperatures for Saturday night / Sunday morning were
increased by several degrees from the previous forecast.

Chances for precipitation will increase heading into Sunday...as
frontogenesis occurs over the Ohio Valley...with a strengthening
temperature gradient. A surface front is eventually forecast to
develop...and move very slowly southeast through the County Warning Area heading
into Monday. Temperature forecasts are somewhat uncertain...given
the sharp gradient...but above-normal temperatures are likely south
of the front on Sunday. A brief period of cooler conditions can be
expected on Monday...with occasional showers and a possible mix with
snow on Monday night. Overall model agreement on the precipitation
patterns with this front are fairly strong...with a slight trend
toward precipitation getting further south a little more quickly on
Monday into Monday night.

By Tuesday...strong surface high pressure is expected to move into
the northeastern states...allowing for a quick return to southerly
flow over much of the eastern part of the country. This should allow
for another period of mild (above normal) temperatures on Tuesday
and especially on Wednesday.

&&

Aviation /03z Wednesday through Sunday/...
surface high pressure will extend across the forecast area tonight
as a coastal low organizes off the Carolina coast. Difficult cloud
forecast as models suggest that low level moisture becomes trapped
underneath a subsidence inversion. This is more so at kday...then
likely extends to the southern/eastern taf sites late tonight into
Wednesday. As a result...have MVFR ceilings at kday starting out
around 2200 feet but then dropping to 1600 feet. For the other
sites...it is a little more tricky but thick cloud heights between
2000 feet and 2500 feet will redevelop between 09z and 12z
Wednesday. There is an outside chance that ceilings here could dip
below 2000 feet but do not have the confidence to place this in
the tafs at this time. Also...MOS guidance is trying to develop
mist/fog overnight. This seems to be overdone if lower clouds
develop along with middle/high clouds overhead from eastern system.
Will leave out for now and monitor.

On Wednesday...as a Nor'easter moves northeast from the middle
Atlantic coast to the New England coast...a weak clipper system
will dive southeast into the lower Ohio Valley by Wednesday
evening. Our area will be stuck between these two features with
light to calm winds and low level moisture remaining trapped. Have
continued with MVFR ceilings. Precipitation associated with the
clipper system is forecast to remain near or just south of the
kcvg and kluk terminals.

Outlook...MVFR ceilings possible Wednesday night into Thursday
night and again Saturday. MVFR/IFR ceilings and MVFR visibilities
possible Saturday night into Sunday.

&&

Iln watches/warnings/advisories...
Ohio...none.
Kentucky...none.
In...none.

&&

$$
Synopsis...
near term...Hickman
short term...
long term...hatzos
aviation...Hickman

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