Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 250536
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1236 AM EST Thu Dec 25 2014
...Updated Aviation Discussion...
Issued at 750 PM EST Wed Dec 24 2014
Wind gusts have subsided to around 25 mph max so cancelled the wind
advisory a little early. Scattered rain showers will continue over
the region through midnight with precipitation likely ending as
isolated rain showers or light drizzle around or after midnight.
The chance for a few snowflakes looks slim to none given moisture
profiles and downstream obs. It appears the boundary layer will
remain too warm for any ice crystals aloft to reach the ground this
Issued at 445 PM EST Wed Dec 24 2014
Just made some minor grid edits to lower hourly POPs over much of
the area as the main rains behind the cold front are moving east
through the Bluegrass as of 430pm. This rain should be clear of the
Bluegrass by around 7pm. We could still see some stronger wind
gusts in excess of 40mph this evening east of I-65 in the Wind
Advisory area, however, believe that peak winds have been reached as
the front passed through a few hours ago. Winds peaked in the 40-50
mph range in the Bluegrass and Lake Cumberland regions with one tree
reported down near Winchester and multiple power outages throughout
the Lexington Metro area including Bluegrass field.
.SHORT TERM (Now through Thursday Night)...
Issued at 257 PM EST Wed Dec 24 2014
The surface cold front has already passed through the region, and
its upper trof will cruise overhead tonight. We could still see
some patchy light rain ahead of the upper trof passage, and maybe a
snowflake or two north of Interstate 64. Brisk winds late this
afternoon will gradually relax this evening. Low temperatures will
be in the middle 30s.
High pressure sliding up from Louisiana to the Carolinas will
provide us with dry conditions for Christmas Day and night. Clouds
will hang around Christmas morning, but we should see some sun in
the afternoon and mostly clear skies tomorrow night. Highs on the
holiday will be in the middle 40s, with lows Thursday night in the
.LONG TERM (Friday through Wednesday)...
Issued at 300 PM EST Wed Dec 24 2014
The synoptic pattern at the start of the long term period will
feature an amplified regime, with troughing over the western CONUS
and a downstream ridge over the Ohio Valley. This ridge will
flatten out through the period, with several shortwaves to contend
with as they eject out of the western trough.
Friday will be the pick day of the extended period, as an expansive
surface ridge moves to the east of the region. This will set the
stage for decent southwesterly return flow, and warming temperatures
aloft. Given the decent surface mixing (although not very deep),
will bump temperatures up a bit towards the latest MET guidance,
which puts highs in the low to mid 50s, perhaps pushing into the
upper 50s in some locations.
An area of low pressure will deepen out to the west Saturday into
Sunday, which will help push a cold front through the region this
upcoming weekend. Isentropic ascent will increase ahead of this
feature, which should lead to some pre-frontal showers beginning
early Saturday. The actual front should push through sometime late
Saturday night into Sunday. Temperatures behind the front will
cool, but it does not look like they will cool substantially enough
to bring any wintry precip concerns into the region on Sunday.
Forecast confidence decreases substantially Sunday night into next
week, as guidance is struggling with the evolution of the western
trough and pieces of energy ejecting out of it. The 12Z solutions,
including the GFS/ECMWF and GEFS all support the flow remaining less
amplified over the Ohio Valley, which pushes the cold front all the
way through the region, drying us out from Sunday night onward.
However, dprog/dt of the GFS/ECMWF show that the operational models
are all over the place with the amplification of the pattern and how
that will affect a southern stream shortwave ejecting out of the
western trough. Therefore, will lower pops for Sunday night through
Monday night, but will not remove them completely given the guidance
variability. Given the forecast temperatures, will also leave
rain/snow mention in for Sunday night, but do not think we will see
much in the way of wintry precip (or any precip at all if the cold
front pushes as far east as the 12Z guidance suite suggests).
Will have to watch when/how the western trough will finally eject
out into our region, as it looks like another potentially
significant storm could result as this wave slides into the eastern
CONUS towards the end of the period and into late next week. Timing
and details are way too murky for now, but this storm could threaten
the New Year holiday, so stay tuned!
.AVIATION (06Z TAF Update)...
Issued at 1235 AM EST Thu Dec 25 2014
Still have some light rain showers out there, mainly over the SDF
and LEX terminals for the next few hours. MVFR cigs should rule at
all sites this period, though do see a few breaks in the clouds.
High pressure over the northwest Gulf of Mexico should travel up the
Appalachians this period, forcing winds to shift from westerly now
to more southerly by this evening. Expect the MVFR cigs to break up
during the afternoon hours, as drier air filters in.