Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 011134
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
734 AM EDT Wed Oct 1 2014
...Updated Aviation Discussion...
.SHORT TERM (Now through Thursday)...
Issued at 244 AM EDT Wed Oct 1 2014
High pressure ridging along the eastern seaboard will continue our
warm, dry weather today and tonight. May have to deal with some
patchy fog and low clouds early this morning. Despite the very
consistent MaxT`s of the past few days, decided to keep northern and
central parts of the CWA a degree or two cooler today given the
possibility of more morning cloudiness than we`ve been seeing
lately. Kept southern KY about the same, though, since less morning
cloud cover is expected there.
On Thursday low pressure will advance from Oklahoma to Iowa, with
showers and thunderstorms out ahead of it. A few afternoon cells
could pop in the LMK CWA west of Interstate 65 thanks to a feed of
moisture riding northward up the Mississippi Valley, but most
locations will probably stay dry during the day.
It will be interesting to see how warm we get on Thursday, with some
guidance suggesting 90 degrees, which would be the first 90s in the
area since September 5. Being ahead of the approaching cold front
suggests warm temperatures, and often it`s a good idea to go warmer
than guidance ahead of a front. However, southerly surface flow
won`t really be all that strong and we`ll have increasing cloud
cover through the day. Clouds can have a pretty significant cooling
effect in the afternoon by the time we reach October. So, would
rather stick with middle and upper 80s for now. Record highs for
October 2 are in the lower 90s.
.LONG TERM (Thursday night through Tuesday)...
Issued at 315 AM EDT Wed Oct 1 2014
The synoptic pattern at the start of the long term period will
feature a deep upper trough across the central CONUS. This trough
will be the focus of the long term period, as it will push into the
Ohio Valley Friday bringing a good chance for rain along with
much cooler temperatures.
A strong cold front will be across portions of eastern IA and MO at
the start of the period Thursday evening. This front will slide
east into the Ohio Valley by late Friday morning. Out ahead of it,
numerous showers and thunderstorms will develop and push
into the region. This setup appears to favor some strong to severe
convection across portions of the Mississippi Valley Thursday
afternoon/evening, but the convection will weaken as it loses
surface-based instability during the overnight hours into Friday
morning as it pushes through the LMK CWA. Therefore, while a few
bouts of gusty winds may be possible in some of the stronger cores,
think a building low-level nocturnal inversion will likely keep
storm winds elevated. PWATs will climb to around 1.75 inches, which
means some locally heavy rainfall will be possible. Given the
progressive nature of this system and the antecedent dry conditions,
no widespread flooding issues are expected. Have slowed this system
down just a bit with this forecast package, as guidance typically
brings fronts associated with deepening surface cyclones in
amplified flow through too fast. Therefore, will have to watch for
the potential for some storm redevelopment/intensification early
Friday afternoon across the eastern CWA as both the NAM/GFS suggest
the atmosphere may try to recover ahead of the front. Think the
morning convection will likely scour out the airmass, limiting
afternoon development along the front, but this is something we will
continue to monitor.
The passage of this front will usher in a much cooler airmass.
Highs on Saturday will struggle in the 50s to perhaps lower 60s!
Given WNW winds around 15 mph with higher gusts, it will certainly
feel quite chilly compared to where we`ve been the past several
This cool airmass will continue into Saturday night, when we could
even see some isolated frost in some of the cold spots as lows fall
into the low 40s/upper 30s. The one thing working against frost
potential is that it appears the center of the surface high will
pass into the Southeast, keeping the Ohio Valley within a surface
pressure gradient and causing winds to stay up a bit. Therefore, at
this time it doesn`t look as if we will be quite cool enough nor
will winds be quite light enough for a widespread event, but it is
certainly something we will continue to monitor.
Otherwise, Sunday into early next week will feature slowly
de-amplifying flow which will mean a slow moderation in temperatures
(getting back into the upper 60s/70s) through the middle of next
week. A quick-hitting system may bring another shot of some showers
Monday into Tuesday, but amounts appear as if they will be quite
light at this time.
.AVIATION (12Z TAF Update)...
Issued at 715 AM EDT Wed Oct 1 2014
Low clouds and patchy fog have developed as expected across central
Kentucky early this morning. They have already socked in LEX.
Visibilities will fall to low end MVFR briefly at BWG as well. SDF
is a much bigger question mark, as they will be right on the edge
of the cloud deck. The low ceilings are just too close for
comfort, though, and will need to be included in the SDF TAF.
Fog will slowly burn off and ceilings will slowly lift this
morning. After that, the TAF period will be smooth sailing with VFR
conditions and light winds.