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Area forecast discussion...updated 
National Weather Service Jackson Kentucky
134 PM EST Sat Dec 20 2014

issued at 134 PM EST Sat Dec 20 2014

Freshened up the hourly temperatures and dew points according to the
latest trends in observations. Otherwise...the forecast remains on track.

Update issued at 1109 am EST Sat Dec 20 2014

Radar echoes are winding down quickly now as forcing exits off to the
east. Any remaining flurries should be done before 1 PM. Freshened up
the forecast to reflect these latest trends. A nice band of clearing
is currently located across central Tennessee and expands southwest
through the upper half of Mississippi. The Cumberland Valley remains
on the fringe of this clearing and the latest satellite trends do
not show this clearing expanding any more to the northeast
necessarily. As such...have a general thinning of the cloud cover
into the evening hours from southwest to northeast per the latest
model guidance and inherited forecast. Temperatures are currently
running a few to several degrees cooler up north. As such...lowered
the highs a bit...generally ranging from the middle 30 north of the low 40s in the south.

Update issued at 632 am EST Sat Dec 20 2014

Made a quick update to the grids and the zone forecast text product
to account for isolated light snow showers that have been occurring
in our northwest counties that past hour or so. Snow showers have
been occurring generally along and north of I-64 and should continue
off and on through around 15z before exiting that portion of the
forecast area. A light dusting of snow will be possible where these
snow showers occur. There have also been reports of light snow in
Pikeville during the past hour. The new zones have already been sent.
The hazardous weather outlook will also be updated to deal with the
snow up north.


Short term...(today through sunday)
issued at 306 am EST Sat Dec 20 2014

The latest runs of most of the forecast models have picked up on the
fact that little if any precipitation is reaching the ground across
central and eastern Kentucky so far this morning. Surface observation from
around the state of Kentucky have been showing no measurable precipitation
across the area for the past few hours. An upper level disturbance
has been producing widespread cloud cover across the area
tonight...but no much more than that thus far. With this system
quickly pulling off to the east across the Ohio Valley...and with not
much in the way of low level moisture in place...the current thinking
is that little if any precipitation will occur at any point during
the remainder of the overnight period or during the day today. That
being said...have lowered precipitation chances from now through
early this afternoon by quite a bit...and have the entire area precipitation
free by 18z. The only reason even low slight chance probability of precipitation were left in
the forecast is the fact that a number of precipitation type echoes are
still showing up on radar imagery from around the area. Also...the
model soundings are still showing a very small chance that some
measurable precipitation could reach the ground over the next several hours.
Will go with this thinking for now...but may need to update the
forecast before the end of the shift if things do not pan out as planned.

Temperatures will continue to run slightly below normal today due to
extensive cloud cover and northerly winds. Temperatures on Sunday are
expected to be slightly warmer than east to southeasterly
flow sets up downslope warming across the area and clouds thins out
behind the departed upper low. Highs on Sunday could top out in the
middle to upper 40s for most locations...with a few readings at or
slightly above 50 north of the Tennessee border and along and south
of the hal Rogers Parkway. A weak ridge of high pressure aloft will
be the weather maker across the region to end the weekend.

Long term...(sunday night through friday)
issued at 306 am EST Sat Dec 20 2014

Active pattern still expected through Christmas week. In
fact...first system will be pushing northeast along The Spine of the
Appalachians to start the new work week. NAM remains the most
aggressive with the northwest extension of precipitation. Still not
convinced we will overcome the downsloping southeast flow.
Thus...have cut back on probability of precipitation into the slight chance category. GFS
seems to be catching onto the downsloping the best...although this
may be due to the fact it does not contain as many shallow layers as
the NAM does. Regardless...the pattern does not support much
precipitation and it should be a fast mover with chances mainly
during the morning hours. Any precipitation will remain all rain as
milder conditions spread northward with the system. By Monday
afternoon into Tuesday...southeast flow only strengthens through
this period...likely keeping the area dry. Much milder air will also
spread northward. This will set up a few very mild days for middle to
late December with highs in the 50s on Monday and around 60 by
Tuesday. Guidance is higher with temperatures into Tuesday...but
opted to stay just under these numbers as middle/high clouds could keep
temperatures down slightly.

By Tuesday night...a northern stream wave is expected to phase with
the southern stream with an area of low pressure developing across
the lower Mississippi River valley. This system will quickly push
northward into the Great Lakes by midday it quickly
deepens. Latest 00z European model (ecmwf) has slowed everything down a bit into the
day have trended towards a slightly slower evolution
with the forecast. Regardless...this system will send a very strong
cold front across eastern Kentucky late Tuesday night through
Wednesday. Strong forcing will yield widespread showers as the front
pushes east. The strong dynamics alone could support some thunder
late Tuesday night into Wednesday morning...but opted to leave it
out for one more forecast cycle and see if models might show more
support in the next few runs. Going to be quite windy as well
Wednesday into Wednesday night as this system deepens. Some wind
gusts up to 35 or 40 miles per hour may be possible. Stayed above guidance for
lows Tuesday night (around 50) as we should stay well mixed ahead of
such a strong front. Highs Wednesday will likely occur early as the
front will bring crashing temperatures through the day Wednesday. A
second wave will push east through the afternoon and
evening...keeping precipitation going. The cold air will bring a
transition over snow as we head through Wednesday afternoon and
evening. While temperatures should stay above freezing through early
evening...if snowfall rates can get good enough...we could see a
light coating by late in the day in some areas. Isolated to
scattered snow showers will linger into Wednesday night...although
models are showing a faster exit of the the window for
snow accumulations will not be all that big. Thus...any accumulation
will remain light...likely under an inch...except for perhaps the
higher ridges where an earlier transition will be possible.

By Christmas...ridging spreads back into the area...setting up a
quiet Christmas day. Temperatures will be cooler with highs only
into the low 40s. Our next weather system will take shape by
Friday...but the track is expected to remain well northwest of
Kentucky at this time...which will keep precipitation Friday night
into Saturday with an advancing cold front all in the form of rain.
This will also mean milder weather returns from Friday into
Saturday...before a return to colder weather by next Sunday.


Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 134 PM EST Sat Dec 20 2014

Expect mainly VFR conditions to reign across most locations through
the period. The only exception will be near the I-64 corridor...where
some MVFR ceilings will linger early this afternoon...before lifting.
Cloud decks will range from 5-7k feet above ground level through this
evening...before scattering out from southwest to northeast through
the night. Winds will remain less than 5 kts through the period as


Jkl watches/warnings/advisories...


short term...Arkansas
long term...kas

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