Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 160228
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1028 PM EDT Mon Sep 15 2014
Issued 1028 PM EDT Mon Sep 15 2014
The widespread rain from earlier has decreased to just spotty light
rain showers. This should continue to be the case for the remainder
of the night.
Issued at 737 PM EDT Mon Sep 15 2014
Showers continue to move southeastward out of Indiana, generally
north of a Paoli-Louisville-Richmond line. Will continue with
likely/categorical PoPs for this area through the evening hours.
Coverage should taper off as the night wears on, with just some
patchy light rain or sprinkles expected after midnight. Clouds will
gradually thicken and lower, especially after midnight as a weak
cold front crosses the region.
Issued at 518 PM EDT Mon Sep 15 2014
Most of the models have done a pretty terrible job forecasting the
rain crossing southern Indiana at this hour. The HRRR and RR seem
to have a handle on it now, and they move it largely intact from
southeastern Indiana into the northern Blue Grass. This fits with
current mesoanalysis showing increased deep moisture convergence in
that region. The convection has been weakening as it approaches,
but PoPs still need to be increased dramatically north through east
of Louisville for at least some light rain with embedded moderate
rain and even a rumble or two of thunder over the next few hours.
.SHORT TERM (Now through Tuesday Night)...
Issued at 255 PM EDT Mon Sep 15 2014
The synoptic pattern this afternoon features a broad trough across
the eastern 2/3rds of the CONUS. This trough will amplify slightly
through the short term period as a strong shortwave slides through
the southern Great Lakes region tonight.
Latest water vapor imagery depicts the aforementioned shortwave
sliding through western IL as of this writing. In response, a
low-level jet of around 30 knots has helped to maintain elevated
convection across portions of IL and IN early this afternoon. The
near-term forecast challenge will be whether or not this activity
makes it into our Indiana counties. Given its current orientation,
the WSW LLJ should continue to foster development on it`s southwest
flank which should keep it going over the next couple of hours.
However, as we get towards 21Z and after, the 850mb flow will veer
enough that favorable inflow into this activity will be lost, thus
likely causing it to weaken. Have introduced thunder wording into
southern IN counties for a bit early this evening, but think this
convection will likely be in a weakening state as it approaches the
region given the loss of favorable elevated inflow.
The cold front associated with this system remains well back across
portions of MO and NW IL. It will push through the region Tuesday
morning. Out ahead of it, guidance continues to suggest some light
showers will be possible tonight. Given the main upper-level
forcing is passing well north of the region, this front will only
have low-level ascent to produce any QPF. In addition, moisture
within this region of ascent is very shallow (around 200mb deep).
Therefore, really don`t think many will see measurable precip. The
most likely scenario will be some patchy drizzle, with perhaps a few
locations reporting a hundredth or two in some light shower
Any precip will come to an end by mid-morning Tuesday, but cloud
cover will likely linger into the late morning north and afternoon
across the south. Have trended temps down a bit for Tuesday to
account for this expected cloud cover through at least the first
part of the day, which puts highs in the upper 60s and lower 70s.
A surface ridge will build into the region Tuesday night as skies go
mainly clear. This will make for good radiational cooling
conditions, which will allow temps to dip into the mid 40s across
southern IN, and upper 40s/lower 50s across KY.
.LONG TERM (Wednesday through Monday)...
Issued at 300 PM EDT Mon Sep 15 2014
High pressure will be centered over northern IN/OH Wednesday
morning. An upper disturbance will cross within the northwest flow
aloft during the day, but with no surface reflection. Thus just
expect some mid/high clouds to keep afternoon highs below normal.
Another disturbance passing by to our north Thursday will allow a
reinforcing high pressure centered over SE Canada to ridge over the
east central U.S., keeping our temperatures below normal and weather
dry to Friday.
The next shot for rain looks to come as a more organized surface low
crosses the northern Great Lakes Sunday and drags a cold front
through here. Timing of this system is fairly uniform among the
GFS/00Z Euro/Navy NOGAPS ensemble. Also looks like we may get an
influx of tropical moisture ahead of the front, so will keep
highlighting the best chance for rain on Sunday/Sunday night. Then
will go dry for Monday for all but our southeast forecast area, as
another cool shot of air builds in from Canada.
Temperatures will warm up ahead of this front, likely into at least
the low 80s Saturday and perhaps even around 80 over southern KY
.AVIATION (00Z TAF Update)...
Issued at 714 PM EDT Mon Sep 15 2014
A weak cold front along a CLE-IND-SGF line this evening will push to
the southeast, crossing central Kentucky between midnight and dawn.
This system will usher is scattered showers, as well as lowering
ceilings. Cigs should go sub 2k` after 06Z and will likely remain
there into the early daylight hours before slowly lifting over the
course of the day Tuesday. Winds will remain below 10 knots through