Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 171858
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
258 PM EDT Fri Oct 17 2014
.SHORT TERM (Now through Saturday Night)...
Issued at 252 PM EDT Fri Oct 17 2014
The synoptic pattern this afternoon features a low-amplitude trough
across the Great Lakes region, which extends into the Ohio Valley.
A PV anomaly rotating through this trough will be the focus of the
short term period.
The aforementioned trough will swing through the region on
Saturday. An associated surface front is currently located across
western IN and western KY, which will swing through the region late
this evening. Along and behind this front, clouds will be on the
increase overnight, mainly across the northern half of the FA. The
increasing cloudiness should help hold temperatures up just a bit
across the north, with lows in the lower 50s expected. Elsewhere,
lows will likely fall into the upper 40s.
A secondary surface front will push through on Saturday. Cooler
air will filter in behind this front, making for a much chillier
day. Temperatures will struggle in the 50s and lower 60s as cold
air advection commences over the region. This front coupled with
ascent from the upper-level PV anomaly may be enough to spark a few
sprinkles. However, after examining forecast cross-sections, am not
impressed with moisture depth and/or ascent within the moist layer.
Therefore, will limit potential for measurable POPs (20%) to mainly
the Northern Bluegrass. These slight chances might be able to be
removed completely from the forecast in the next update as trends
dictate. Think the most likely scenario will be a few passing
sprinkles and maybe an isolated light shower, but most will
certainly remain dry.
A surface ridge will build into the Ohio Valley Saturday night,
which will allow winds to go calm and skies to go mostly clear.
This setup will make for good radiational cooling conditions, which
should allow temperatures to fall into the mid and upper 30s.
Patchy frost is looking likely at this time, but widespread frost is
a bit more up in the air as it will depend on just where the center
of the surface ridge ends up and how light winds go. Either way,
headlines may be needed for tomorrow night, so stay tuned.
.LONG TERM (Sunday through Friday)...
Issued at 251 PM EDT Fri Oct 17 2014
The long term period will begin with a surface high centered over
the Ohio Valley Sunday. This will bring clear skies, but
temperatures will be on the cool side. After morning lows in the
30s, temperatures will top out in the upper 50s to lower 60s.
The high will begin to shift eastward Sunday night and an upper
level trough will start to drop in to the upper midwest. This trough
will deepen across the northeastern CONUS through midweek,
eventually becoming a cutoff low. A cold front associated with this
system will approach and move through the area Monday into Monday
night. Though Sunday night looks to remain dry, showers ahead of
this front will move in during the day Monday and continue into
Monday night. Models are coming in a bit higher with pops than with
previous runs. However, it looks like the GFS in particular may be a
bit overdone, so will lean more towards the ECMWF for pops. Temps
look to be a few degrees warmer on Monday with highs in the lower to
A few showers may linger across east central KY Tuesday morning as
the upper low shifts slowly off to the east. Skies should begin to
clear Tuesday night as high pressure builds in. Dry conditions are
then expected for the remainder of the long term. High temperatures
will be below normal Tuesday through Thursday, topping out in the
upper 50s to lower 60s. Lows will be in the upper 30s to lower 40s.
The coldest morning still looks to be Thursday morning with lows
mainly in the upper 30s. There is the potential for frost,
particularly in sheltered locations.
.AVIATION (18Z TAF Update)...
Updated at 108 PM EDT Fri Oct 17 2014
VFR conditions will prevail through this afternoon and tonight,
before potentially MVFR cigs move in towards Saturday morning.
Clear to partly cloudy skies will prevail this afternoon, as WSW
winds continue to remain gusty out ahead of a surface cold front.
This front will push through tonight into Saturday, bringing
increasing cloudiness. High-end MVFR cigs look likely with this
system, with perhaps even a few sprinkles or light showers at KLEX
and KSDF. Will leave precip mention out for now given the expected
low coverage, but will continue with MVFR cig mention. Behind the
front, winds will be out of the NNW.