Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Jackson Kentucky
758 am EDT Thursday Oct 30 2014
issued at 640 am EDT Thursday Oct 30 2014
Updated sky grids to reflect current Sat and ob data. These clouds
are expected to slide south and east then diminish in the late
morning hours. Also updated temperatures to reflect latest trends and observation.
Otherwise forecast is on track.
Short term...(today through friday)
issued at 350 am EDT Thursday Oct 30 2014
This morning observation and Sat continue to indicate a cloud deck dropping
south across primarily northern portions of the County Warning Area. This is
expected to generally skirt the northern and eastern portions of the
County Warning Area through the late morning hours. Otherwise high pressure builds
into the region ahead of next system with mostly sunny skies expected
much of the day Thursday. Would expect some clouds to begin to build
east across far western areas by later Thursday with approaching
system. Clouds will continue to trend up overnight Thursday with
chances of precipitation increasing across the northwest by early morning Friday.
Models continue to be in good agreement with strong upper level
cutoff low dropping south across the region. This will bring increased
chances of precipitation through the day Friday from northwest to southeast. Given the
strength of the disturbance early afternoon into late afternoon we
will be fairly unstable so a isolated chance of thunder was kept in
the forecast. Otherwise temperatures will drop through the afternoon
on Friday with best chances of precipitation generally across northern and
eastern portions of the County Warning Area. Precipitation chances will be lesser across SW
with better dynamics across the east.
Long term...(friday night through wednesday)
issued at 350 am EDT Thursday Oct 30 2014
A complex forecast is on tap through the first half of the weekend
with the expected first snow and potentially the first hard freeze
of the fall. While models are in overall decent agreement...still
some slight differences on the strength of the trough and associated
low pressure area as it drops through the area early in the weekend.
While it should not have much impact on the forecast...it could
change the overall precipitation amounts if the system is stronger.
For now...opting to go with a more compromised solution with
As it stands now... the initial shortwave trough will be on the way
out by late Friday evening...with perhaps a brief lull in
precipitation possible. However...as the deformation axis moves
overhead later in the night...precipitation should pick back up.
Thus...plan to go with fairly high probability of precipitation through the night...trailing
off towards the southwest. With cold advection already into full
gear at the start of the forecast period....we should see a quick
changeover in the high terrain near the Virginia border. As the
night wears on...we should see more of the rain transition to
snow...eventually even the valleys by daybreak Saturday.
However...with the warm ground...not really anticipating much if any
accumulation. The exception will be in the high terrain where
temperatures falling into the middle 20s will allow for better snowfall
accumulations. Plan to go with amounts over 4 inches for areas on
Black Mountain...trailing off to around a half inch on ridges above
1000 feet...and eventually down to a tenth or less in the valleys.
It is possible a heavier burst of snow could put down a bit more
snow in any given location...but for the most part...snow will have
a tough time accumulating on the warm ground.
With the deep trough over the area...clouds and some precipitation
will linger through Saturday...making it look more like winter than
fall across the area. Highs will struggle to rebound from readings
in th low 30s early in the day. In fact...many ridge locations may
not get back to 40. Fortunately...the slight warming in the boundary
layer should be enough to change any snow in the morning back over
to rain...with the exception again being the highest elevations in
the southeast. Lots of question still surrounding how fast we will
clear out as we head into Saturday night. Latest model guidance has
beefed up cloud cover quite a bit. This combined with light
northwest winds...may limit any frost potential Saturday night and
keep US from having a hard freeze. The best chances for the hard
freeze would be towards the I-75 corridor where the best chance at
clearing will reside.
The better chances for a hard freeze will come Sunday night as skies
should finally be clear areawide. With dewpoints in the 20s...we
should see lows settle into the middle 20s in the valleys...with
readings around 30 on the ridges. Plan to mention the potential for
a hard freeze both Saturday and Sunday nights in the severe weather potential statement and Special Weather Statement.
Also plan to include information about the expected snow in the Special Weather Statement.
Strong ridging will cross the area early in the upcoming
week...before another front creeps into the Ohio River valley
towards middle week. This will allow for milder weather to return and
eventually chances for rain by Tuesday night. Still some differences
on timing in the models...so while confidence is fairly good we will
see some rain towards midweek...exactly when is the question.
Aviation...(for the 12z tafs through 12z Friday morning)
issued at 758 am EDT Thursday Oct 30 2014
LIFR or worse fog will burn off through 14z in the deeper river
valleys...with VFR conditions prevailing thereafter. Also expect
stratocu deck at around 4k feet above ground level to gradually dissipate across
locations along and north of the mountain Parkway. Clouds will increase
and lower between 06 and 12z out ahead of the next approaching