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Area forecast discussion 
National Weather Service Jackson Kentucky
1246 PM EST Thursday Dec 25 2014

Update...
issued at 1246 PM EST Thursday Dec 25 2014

Will be updating the forecast package to hang onto clouds just a bit
longer as pesky low SC deck gradually dissipates through the late
afternoon and early evening time frame. Otherwise just minor tweaks
to the hourly grids to account for latest observations.

Update issued at 938 am EST Thursday Dec 25 2014

Updated grids for latest hourly observation and trends. This resulted in very
minor changes to the forecast. Overall forecast is in excellent shape
this Christmas morning. Still picking up on some patchy drizzle in
the observation and on radar. Cloud top temperatures suggest there is some flurry
activity out there as well...mainly in the higher elevations. No
update to the zones planned at this time.

Update issued at 745 am EST Thursday Dec 25 2014

Hourly grids have been freshened up based on recent radar and
observation trends. This led to holding onto chances for drizzle a
bit longer in many areas. Flurries will also be possible initially
above 2000 feet. However...the moisture will become more shallow this
morning and eventually stratocu should be left behind. This stratocu
should begin to scatter out by early to middle afternoon in western
locations.

&&

Short term...(today through friday)
issued at 325 am EST Thursday Dec 25 2014

A deep closed upper level low and surface system continues to depart to
our north and northeast with the trailing upper level trough now
working across parts of the Great Lakes...Ohio Valley and Appalachians.
Meanwhile to the west...a ridge extended from the Pacific to the
southwest of Baja California into the southern and Central Plains region. Also
at the surface...a ridge of high pressure extended north from the western
Gulf of Mexico north into the MS valley region. Some showers...likely
mixed with or all rain above 2000 feet are working from the Kentucky
Cumberland mountains east into the western Virginia Mountains. Additional
isolated showers or patches of drizzle have developed further to the
west nearer to the I 75 corridor as the upper level trough axis works
through the area and core of the coldest 850 mb air and slightly
steeper lapse rates move in. Currently across the high terrain the to
of Black Mountain at near 4100 feet is 30 degrees while The Flatwoods
mesonet site in Pike County near 2800 feet is 34 degrees. Lower
elevation temperatures are generally in the upper 30s to lower 40s.

The primary weather concern for the short term period is the light
precipitation through around dawn as the trough works through and then the
low level moisture subsequently becomes more shallow and a period of
stratocu follows. Above 2000 feet snow or a rain and snow mix is
anticipated as cloud top temperatures near the returns to our west are
generally -11c to -14c or supportive of the presence of ice in these
clouds. Also in these areas above 2000 feet min T should reach 32 or
lower. Lower elevation locations will bottom out in the middle to upper
30s. There are areas with warmer temperatures and any light precipitation falling
from them would be more of a drizzle. Some recent short term guidance
such as the hrrr and rap guidance supports one last uptick in
coverage of this light precipitation as it works across the region over the
next 3 to 5 hours...ending not long after sunrise. Accordingly...a
pre first period was used in the zone forecast product and the severe weather potential statement highlighted the
small chance for snow showers initially for the 4 Virginia border counties.

Otherwise...behind the departing trough...high pressure will build
into and then across the area before shifting to the east of the area
on Friday. This will lead to gradually clearing skies from west to
east today and dry weather for tonight and Friday. This pattern will
favor a Ridge/Valley temperature split for tonight with the deeper
valley locations and typical cold spots reaching the middle 20s. A very
dry air mass projected for Friday will warm well into the 50s across
the lower elevations with a few locations near the Virginia border may
reach 60 or above on a down slope component.

Long term...(friday night through wednesday)
issued at 232 am EST Thursday Dec 25 2014

Confidence is high through the weekend as models remain in good
agreement. The period will start off dry as high pressure holds into
Saturday. Friday night will feature another night of Good
Ridge/valley splits...especially in the east. We will then see a
decent recovery on Saturday as highs soar to around 60 with the help
of sunshine. A shortwave trough will push into the Ohio River valley
late Saturday night into Sunday. This will bring increasing clouds
late Saturday/Saturday night. Rain will also spread into the area
Saturday night and continue into Sunday. Forecast becomes
increasingly uncertain beyond Sunday as there is some question as to
how long precipitation chances linger. The latest 00z European model (ecmwf) has sped
up the system with precipitation exiting by early Monday morning.
However...12z GFS continues to hold precipitation over our southeast
counties into Monday night. For this reason...will maintain some
probability of precipitation in the forecast into Monday night. However...the highest probability of precipitation
will be confined to the part of the forecast where there is better
confidence Saturday night and Sunday. Models remain too warm to
support anything but rain through Monday night.

After Monday night...models have come into better agreement on a
less active period of weather. Middle/upper level flow turns more
zonal. Even the idea of a middle week storm per the last two runs of
the European model (ecmwf) is now missing on the latest run. Thus...going to cut back
on probability of precipitation through Thursday of next week. It does look like a system
may finally take shape late Thursday into Friday...but this is just
beyond the current forecast period. The trend is certainly towards
quieter weather next week...so will have to see if the models
maintain the system for late in the week. The weather should trend
towards normal values next week as cooler air slowly works into the
area as precipitation ends Monday and Monday night.

&&

Aviation...(for the 18z tafs through 18z Friday afternoon)
issued at 1246 PM EST Thursday Dec 25 2014

Wind flow at the surface and aloft continues to back to the southwest.
Low MVFR stratocu deck will only gradually dissipate through the
first 6 hours or so of the forecast. Otherwise we finally clear out
with light winds...generally from the south...southwest through the
remainder of the forecast period.

&&

Jkl watches/warnings/advisories...none.

&&

$$

Update...ray
short term...jp
long term...kas
aviation...ray

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