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Area forecast discussion 
National Weather Service Jackson Kentucky
730 am EST Sat Dec 27 2014

Update...
issued at 730 am EST Sat Dec 27 2014

Band of rain showers has been moving across the commonwealth early
this morning. Hrrr has been consistent with the idea of this band
weakening and dissipating as it moves eastward. However...recent runs
has shown a slower trend overall with indications that some of the
shower activity could hold together long enough to provide US with
some rain...mainly across our Blue Grass counties. This trend seems
to be supported by the fact that the band has been fairly persistent
thus far. Therefore introduced probability of precipitation across our north for the middle
morning time frame while maintaining a gradual weakening trend. Also
included a wider swath of sprinkles for some areas that may not see
any rain this morning. Otherwise forecast appears on track.

&&

Short term...(today through sunday)
issued at 337 am EST Sat Dec 27 2014

Models are in good agreement through the short term...though they
were late in picking up on potential shower activity currently moving
east of our area. Hrrr is picking up on additional shower activity
far to our west...over the western end of the commonwealth and does
bring that eastward towards our area. But activity supposedly weakens
and dissipates by the time it reaches our County Warning Area around middle morning.
Other operational models tend to support this scenario though will
have to watch this carefully through the morning in case models wind
up handling this poorly as well and probability of precipitation need to be ramped up more
quickly through the day.

Middle/upper level ridge...centered over Cuba is retreating eastward
with approach of short wave energy and trough lifting out of the
western Great Basin...southwest Continental U.S.. at the surface...high pressure
centered over the central Atlantic coastal region is also beginning
to retreat eastward. Continued movement of middle/upper level trough
out of the western Continental U.S. Will induce a series of surface lows...the first
developing over the eastern plains and moving through the Great
Lakes by late today. This first low will drag a surface cold frontal
boundary into the Ohio Valley tonight...reaching our County Warning Area by Sunday
morning. A second low will develop much further south over the
southern Mississippi Valley region and track northeast along the
front as the surface boundary pushes across the Appalachians Sunday
morning. This will keep our weather wet through to the end of the
short term.

For sensible weather...weak impulse responsible for sprinkles and
very isolated shower activity over our area early this morning is
exiting to our east...with corresponding activity exiting as well.
Middle and high level clouds will continue to thicken and lower with
time...though we could see a few breaks at times through the day.
Could see some additional sprinkles across portions of our area by
middle morning to noon as the second area of activity to our far west
weakens while moving eastward. Our main event...rain associated with
the approaching cold frontal system will begin to overspread our area
from the west late this afternoon. Rain will increase through the
overnight and linger through the day Sunday as the aforementioned
second wave of low pressure rides up into the southern Appalachians.
Increased probability of precipitation for tonight and Sunday following the lead of guidance.
Temperatures continue to moderate with a relatively limited diurnal
range over the next 18 to 24 hours due to increased cloud cover. Also
preferred to go with a non diurnal temperature trend through the day Sunday
as colder air filters in behind the surface cold front.

Long term...(sunday night through friday)
issued at 337 am EST Sat Dec 27 2014

Frontal boundary and waves of low pressure will slowly push east of
the County Warning Area moving into the long term period. Slowly lessen probability of precipitation
overnight Sunday into Monday as better lift moves east of the region.
After this there is a upper level disturbance that moves across the
region going into Tuesday this will bring some cloud cover to the
region. Other than that not expecting much in the way of precipitation as
high pressure continues builds east Wednesday with skies clearing out
through the day. Cooler air will filter into the region giving way to
highs in the low to middle 30s for highs on Wednesday. Continued
clearing skies and building high pressure will give way to good
radiational cooling Wednesday night with lows in the upper teens to
lower 20s across the region. More uncertainty in the models exist as
we move into the longer range portion of the long term. High pressure
is expected to slowly move east as we move into Thursday. Right now
Thursday looks dry...however a low pressure system is expect to
develop across the Southern Plains Thursday/Friday as upper level low
ejects out of The Four Corners region. Moisture will slowly spread
north and east toward the Ohio Valley as we move into Friday. Timing
on the precipitation differ at this point with European model (ecmwf) most progressive. Given
the uncertainty did stick reasonably close to the model blend and
trying to keep some consistency/collaboration. This does give way to
slight probability of precipitation Thursday night and chance probability of precipitation Friday. Given cooler temperatures
onset of probability of precipitation would be a snow or rain/snow mix Thursday night into
early Friday. However right now confidence remains low given model
divergence during this period.

&&

Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 730 am EST Sat Dec 27 2014

Showers associated with an approaching cold frontal system will
develop across the region today...dropping flight conditions into
MVFR territory from west to east late this afternoon and this
evening. Conditions worsen overnight as rain picks up and lingers
through the remainder of the forecast. Winds will run less than 10
kts through the period...generally from the south/southwest.

&&

Jkl watches/warnings/advisories...none.

&&

$$

Update...ray
short term...ray
long term...dj
aviation...ray

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