Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 071121
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
621 AM EST Sat Dec 7 2013
...Updated Aviation Discussion...
.SHORT TERM (Now through Sunday)...
Issued at 315 AM EST Sat Dec 7 2013
...Light wintry mix possible early Sunday morning...
Skies will tend to clear from north to south this morning as
Canadian high pressure builds east across Iowa. By dawn, mostly
clear skies are expected across southern Indiana. Although low
clouds will erode by late morning across our southern counties, some
high clouds streaming in from the southwest may keep skies overall
partly cloudy this afternoon near the Tennessee Border.
Cold temperatures expected this afternoon, especially over the
southern Indiana snowpack. Highs will range from the mid 20s north
to the lower 30s near Tennessee. Winds will continue from the north
at around 10 mph.
In response to lift associated with the right entrance region of a
jet along the Ohio River, weak low pressure is forecast to develop
late Saturday evening along the western Gulf coast. by Sunday
morning, an inverted surface trough is forecast to move north across
Tennessee into south central Kentucky. This surface feature will
become the focus of some mixed wintry precipitation.
As opposed to Friday`s storm, precipitation here will develop within
a warm air advection regime, and temperatures will tend to rise
through the event as southwesterly flow aloft rides over cold air at the
surface. The GFS forecasts very light QPF amounts, with not much
precipitation at all northwest of the Bluegrass Parkway. The more
robust NAM develops precipitation just after midnight south of
Bowling Green, and bring light amounts as far north as southern
Indiana shortly after dawn.
Forecast soundings show a potential for light freezing rain and
sleet, with perhaps an initial bit of snow across north central
Kentucky and southern Indiana, assuming precipitation gets that far
north. Eventually, by mid-day Sunday, any freezing rain will turn to
rain as temperatures warm into the mid 30s generally south of
Due to uncertainty about the amount of precipitation, and the timing
of any potential switchover to rain, will issue a Special Weather
Statement highlight the potential for light icy accumulations early
.LONG TERM (Sunday night through Friday)...
Issued at 300 AM EST Sat Dec 7 2013
The next winter weather system mentioned above will be departing
Sunday night, though the new ECMWF keeps up a cold precip over the
southeast third of our forecast area through the night. We should
get at least a brief respite from precip, before yet another wave
moves in within the flow aloft late Monday night into Tuesday. The
NAM/GFS and to a lesser extent the GEM all have precip over the
Appalachians with a secondary band forming along the Ohio River.
Given this model consensus, will start edging pops up along the
river. Will keep under 20 percent though given much drier dewpoints
The rest of the period should be dry, though Wednesday and Wednesday
night those models bring a front through with hints of QPF just to
our north. Sometimes we can squeeze out a few flurries from this
type of system, but will leave forecast dry for now.
Given that we do not have a great change in airmass during this
period, below normal readings will continue through the long term
.AVIATION (12Z TAF Update)...
Updated at 620 AM EST Sat Dec 7 2013
Low MVFR ceilings at SDF and LEX will clear rapidly by 13z and
around 14z respectively. Ceilings will lift later at BWG, likely
waiting until late morning.
Skies will likely become mostly clear this afternoon and evening at
LEX and SDF, while high clouds will keep BWG partly cloudy. North
winds will continue around 10 mph today, backing towards the
northeast at 5 to 10 mph towards Sunday morning.
Clouds will lower early Sunday morning as a surface trough moves
north towards Tennessee. A light wintry mix including freezing rain
and sleet will likely develop at BWG after 06z Sunday morning. Mixed
precipitation may develop at LEX right near the TAF period ending
time of 12z Sunday. Precipitation may just miss SDF to the
southeast, and thus will not put any specific mixed precipitation in
for SDF just yet. However it is possible that a light wintry mix may
develop towards 12z at SDF.
Ceiling will stay VFR until any precipitation starts, the lower to