Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 030032
Area Forecast Discussion
National Weather Service Louisville KY
732 PM EST TUE FEB 2 2016
...Mesoscale Forecast Update...
Issued at 730 PM EST Tue Feb 02 2016
Large area of light to moderate rain looks like it will continue to
move eastward across the forecast area. A more prominant line of
thunderstorms is closer to the front and marching eastward across
western KY and southwest IN. There is a narrow window of instability
ahead of this line, but the chance for tornadoes getting into our
eastern forecast area looks pretty slim. Thus will be cancelling
part of the watch box with an update. The threat is still fairly
small in our southwest forecast area, especially given that PAH is
not seeing any upstream reports of severe weather. Still will allow
this line a few more hours to mature and possibly develop some
Issued at 530 PM EST Tue Feb 02 2016
A QLCS has formed over portions of western TN and west-central KY
early this evening, along the eastern edge of the surface-based
instability gradient. Overall thinking is that this activity will
continue to struggle as it moves northeast, as mid/upper 50s
dewpoint inflow into this system is likely not lending to any
surface-based parcels. Can`t rule out some isolated warnings with
this line, but don`t expect anything major from this activity.
Guidance continues to suggest storms will fill in along the cold
front across western KY and TN over the next few hours. This
process is already occurring, but thus far there are no warnings for
this activity. Given this initial QLCS moving through now, we have
some doubts as to how severe this second line will become as it
moves through. Not ready to downplay the threat too much yet, but
something we are monitoring. The flood threat has become a bit more
of a concern though, especially across south-central KY where a few
rounds of storms are possible and where the heaviest snow fell.
.SHORT TERM (Now through Wednesday Night)...
Issued at 320 PM EST Tue Feb 2 2016
...Windy This Afternoon and Evening...
...Strong to Severe Thunderstorms Possible this Evening into
Environment and Forecast Analysis
Late this afternoon, several lines of SW to NE moving convection
have developed along and ahead of the front. The most notable line
was over western TN and western KY with a few stronger cells
developing within that line. These lines of pre-frontal convection
make the severe scenario a bit complicated for this evening. First
of all, there is the concern that parts of atmosphere over western
KY and into west central KY/southwest IN may have destabilized
enough in a decent wind environment for some of these cells to
become strong to severe as they enter our far western forecast area
(Logan County, KY to Dubois County, IN) so will be watching these
cells in the pre-frontal convection closely over the next few hours.
These pre-frontal lines of showers and storms may also work to eat
up some of our instability, however robbing the atmosphere of fuel
for the main line of convection still set to develop this evening.
Although convection doesn`t look all that impressive along the front
as of 345pm, a shortwave moving NE out of the southern Plains is
still expected to enhance convection during the late
afternoon/evening hours. The line of convection along the front
should have the best sfc moisture and decent ribbon of sfc based
instability to work with. Some of the high-res models don`t look
too impressive though with convection along the front. The pre-
frontal line of convection will likely be enhanced as the shortwave
arrives also. Whatever does develop along the front should merge
with the initial pre-frontal line of convection west of I-65 and
continue east across our forecast area through the evening and
overnight hours. A good 60-70 kt LLJ will get going along and east
of I-65 parallel to the mean flow which should yield a good moderate
to heavy rainfall setup for a good portion of our forecast area.
Damaging winds and isld tornadoes are still a threat mainly west of
I-65. These would be threats in cellular structures as well as
linear structures. As the front/convection merge with the pre-
frontal line of convection along or just west of I-65, damaging
winds will still be a threat, the tornado threat will lessen, and
flash flooding will become more of a threat. With flash flood
guidance between 1.5-2 inches east of I-65 and rainfall amounts
coming up on the latest high-res guidance to 2-3 inches in pockets,
will definitely need to watch minor flooding issues this evening and
through the overnight hours.
Will keep the current Wind Advy in place through tonight. The
highest wind gusts (lower 40 mph range) have been observed over
south central KY this afternoon. While clouds and rain showers over
southern Indiana and north central KY have limited wind gusts so
far, still think a good wind threat of 40-45 mph exists outside of
Remaining showers should linger over east central KY Wed morning
before ending. Temps on Wed won`t go much of any where lingering in
the mid 40s to mid 50s across the area.
.LONG TERM (Thursday through Tuesday)...
Issued at 245 PM EST Tue Feb 2 2016
Thursday - Saturday...
Dry conditions are expected Thursday and through the end of the week
as we remain largely under sfc high pressure and a split flow
pattern aloft. Temps will be the coldest on Thurs with highs in the
upper 30s/lower 40s and lows Thu night in the lower 20s. Temps will
moderate for Fri/Sat though with highs back in the upper 40s/lower
50s by Sat.
Sunday - Tuesday...
As a ridge axis amplifies just west of the Rockies, a deep trough
will become carved out over the Midwest for the beginning of next
week. This will lead to colder temps and a more active pattern.
With many embedded disturbances expected in the upper trough, light
rain or snow chances will be possible beginning Sun night and
continuing through Tues.
.AVIATION (00Z TAF Update)...
Updated at 655 PM EST Tue Feb 2 2016
Well...a complicated set up TAFs with 2 distinct lines of shra/tsra.
The prefrontal line has fizzled along and east of I 65 as it outran
the instability axis. This has produced mainly vfr and some mvfr
cigs and vsbys.
The second line is the actual front from just west of EVV to MKL is
along the instability axis but the sun has set and the storms have
some wind but the svr threat appears to be minimal as most of the
boundary layer is still stable. This 2nd line will bring about an
hour of borderline IFR cigs and vsbys and most importantly very
heavy rain as there is a cornucopia of moisture in the atmosphere.
Gradient winds will continue to be strong before and after 2nd line,
with 12 gust 22 throughout the night and into Wednesday.
KY...Wind Advisory until 7 AM EST /6 AM CST/ Wednesday for KYZ023>043-
IN...Wind Advisory until 7 AM EST /6 AM CST/ Wednesday for INZ076>079-