Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 210010
Area Forecast Discussion
National Weather Service Louisville KY
810 PM EDT Thu Oct 20 2016
Issued at 810 PM EDT Thu Oct 20 2016
Cold front is now pushing east of I-65, and will continue as upper
trough axis begins to slide through overnight. Widespread showers
and storms are exiting our eastern border at this time, so will
remove thunder wording for the rest of the night. Still expect good
coverage of very light showers or drizzle overnight so Pops will
remain sizable for otherwise low expected QPF totals. Can`t rule out
a rumble of thunder or two as mid level lapse rates really steepen,
but not enough confidence to keep mention at this time.
Temps will drop into the upper 40s and low 50s as we move through
the overnight with steady NW winds between 10 and 20 mph. A few
gusts around 25 mph are also possible.
Issued at 520 PM EDT Thu Oct 20 2016
Have a solid line of convection running from Danville southwest to
Scottsville. Temperatures ahead of this line are in the 70s, and we
had just enough instability for some hail to form in a stronger
tower. Will continue to monitor radar and issue special weather
statements and/or severe warnings for hail along this line as
needed. Any new cells behind this line should just remain elevated,
but with colder air moving in aloft cannot rule out some small hail
in the cells that form here either. Have updated the gridded
forecast to handle current trends.
.SHORT TERM (Now through Friday Night)...
Issued at 230 PM EDT Thu Oct 20 2016
...Much Cooler Starting Tonight...
Weak surface gradient over the region now, as the frontal boundary
is roughly over the region. That gradient will tighten up quickly
behind the boundary later this afternoon, with temperatures dropping
quickly behind it. Instability aloft may allow for some elevated
showers as the upper trough axis swings through overnight. Still
cannot rule out some lingering light rain showers in our east Friday
morning, but that should taper off in the afternoon. Friday will be
a raw day, especially when compared to our record heat this week.
Winds will gust out of the northwest and temperatures will not rise
too much...likely staying in the 50s for most locations north of the
Friday night, model consensus places the center of the surface high
over eastern AR/western TN with a ridge axis extending north to
northeast. That could mean our normally colder spots in the
northeast could be spared from frost because of a gentle northwest
breeze overnight. Points west of a Louisville to Liberty, KY line
would have a better chance though. For now have gone with lows
in the upper 30s to around 40. Frosty tool gave patchy frost pretty
much areawide based on this temperature forecast.
.LONG TERM (Saturday through Thursday)...
Issued at 240 PM EDT Thu Oct 20 2016
The high will move into the Deep South Saturday and stay there for
the weekend. That pattern will mean a westerly Saturday and then a
southwesterly flow Sunday. After that, a dry reinforcing cool front
will move through on Monday followed by high pressure moving by to
our north Tuesday. The next rain chance will come Wednesday night
and Thursday, as guidance has another front dropping into the
Midwest. Confidence in timing is average for a Day 7 event, given
some spread between models in the handling of this shortwave
Temperatures Saturday will be similar to Friday`s, but with a little
less wind. The rest of the period looks to be closer to normal.
Sunday the southerly component to the wind should warm us up and
then the front Monday will not bring much of a change in airmass.
.AVIATION (00Z TAF Update)...
Issued at 709 PM EDT Thu Oct 20 2016
Surface low ahead of an amplified trough is currently between SDF
and LEX. These features will continue to push east tonight, with
convection just now leaving LEX.
Main concerns this evening and overnight will be low ceilings and
gusty NW winds behind the passing cold front. Will start out the TAF
sites on either side of the low MVFR or IFR threshold, with steady
NW winds between 10 and 20 mph for much of the night. A few gusts up
around 25 mph are also possible. Low ceilings should persist the
whole night, with gradual improvement through the late morning and
early afternoon hours. We should be dry by Friday, but do expect
some pockets of light rain or drizzle could be around at times