521
FXUS63 KLMK 161739
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
139 PM EDT Wed Oct 16 2013
...Updated Aviation Discussion...
...Forecast Update...
Issued at 1155 AM EDT Wed Oct 16 2013
A cold front located across central Kentucky as of 1530Z will slowly
push southeast through the region this afternoon/evening. A
disturbance located across western TN/KY looks to push northeast up
the front this afternoon providing better coverage of rain showers
from roughly BWG to LEX and points south and east through this
afternoon. Therefore increased POPs to 60 percent this afternoon
for these areas.
Generally adjusted temps downward for this afternoon. With
plentiful low level clouds and scattered to numerous rain showers,
temps will remain in the lower 60s for the most part. Some
locations behind the front may not even make it out of the upper 50s.
.SHORT TERM (Now through Thursday)...
Issued at 315 AM EDT Wed Oct 16 2013
Cold front is actually showing up quite nicely as a radar fine line
from near IND to near PAH. Clusters of mainly light rain showers are
ongoing ahead of the front, with even a few pockets of moderate rain
based on radar presentation over southern Indiana. Still it is
mainly a low-QPF event with most locations on track for no more than
a tenth or two.
Look for scattered showers to move across the area as the front
continues its eastward push. Best chances for rain will be this
morning north and west of a line from roughly Bowling Green to
Frankfort, but will linger much longer into the afternoon farther
east as the front slows and a wave rides ENE along the front.
Will keep scattered showers going through the night south of the
Parkways as the front will be hung up and could oscillate back to
the north in response to any wave moving along it. A sharper
northern stream disturbance will life ENE from Iowa into Michigan on
Thursday, and even with most of the forcing remaining to our north,
will still support slight chance POPs Thursday morning across the
northern half of the area. Drying trend will take hold Thursday
afternoon with the upper trof axis to our east and the surface front
finally pushing well to our east.
Temps feature plenty of bust potential given the expected fropa.
Expect very minimal recovery in daytime temps today, and will hope
our max temp forecast is high enough to capture the temp at
daybreak, especially east of I-65. Mid/upper 60s will do it for most
locations. Tonight's mins are highly dependent on frontal position,
so confidence is quite limited in the south and east. Could see
quite a range, as mid-40s in Indiana may not be cool enough, while
mid-50s near Lake Cumberland might be too cool if the front waves
back north. Thursday will be well below normal, with the best
recovery expected west of I-65 where we break back out of the clouds
first. Cooler NAM MOS still seems the way to go, with mid 60s near
BWG while the Bluegrass will be lucky to crack 60.
.LONG TERM (Thursday night through Tuesday)...
Issued at 305 AM EDT Wed Oct 16 2013
The long-term period will begin with our latest shortwave trough
exiting to our east, with surface high pressure building into the
Ohio Valley. Cloud cover associated with this departing system
should diminish fairly early in the overnight hours. Combine this
with light winds and temperatures should drop into the upper 30s and
lower 40s, with typically cooler valleys dipping into the middle
30s. Friday looks fairly sunny, but will be on the chilly side as
highs top out in the low to middle 60s.
From Saturday through Tuesday a large polar low will slowly spin
across Ontario Canada. This will send two shortwave troughs and
associated surface cold fronts our way. The first will be Saturday
and the second appears to be Monday night or Tuesday. The amount of
available moisture with either front remains the big question. There
seems to be good agreement that the Saturday system will produce
some light rain showers north of the Ohio River, with locations
further south remaining dry. Believe some of this will make it into
our southern Indiana counties, although the latest GFS has backed
off a bit. Will just run an isolated rain shower chance. Precip
would occur during the morning hours before exiting the forecast
area Saturday afternoon. Saturday will be another chilly, below
normal day, as temperatures start out in the low to middle 40s and
top out in the lower 60s. Under the influence of surface high
pressure, Sunday and Monday will be dry as we wait for the next
frontal boundary. Highs will range from the low to middle 60s, with
overnight lows in the lower 40s (upper 30s in cooler valleys).
Models differ with the Monday night/Tuesday system, which is
centered around just how amplified the shortwave trough will get and
the amount of available moisture. The latest GFS ramps up the
moisture ahead of the Tuesday front, while the ECMWF moves the front
through Monday night and keeps deeper moisture shunted further
south. The ECMWF produces precip to our north where the better
forcing should be located. When looking back at how models handled
our frontal passage for today, when it was in the forecast day 6-7
time frame, they were overachieving on the strength and QPF. With
this in mind, will keep continuity with the previous forecast of dry
conditions and wait for a better consensus among these operational
models as well as their ensemble members, which are demonstrating
quite a bit of spread.
&&
.AVIATION (18Z TAF Update)...
Issued at 135 PM EDT Wed Oct 16 2013
A cold front has passed through SDF/BWG as of 1730Z and will
continue to move ESE toward LEX this afternoon/evening. Expect a
wind shift at LEX around 2Z as the front makes very slow progress
eastward this afternoon.
On and off showers associated with this front will continue at the
TAF sites...mainly BWG/LEX through the next 24-30 hrs. BWG/LEX will
be closest to the front and so will have better rain chances as two
notable waves this afternoon and tomorrow morning (after sunrise)
travel up the front enhancing the precip field.
While SDF should stay VFR for most of the TAF period, BWG/LEX will
be primarily MVFR with notable IFR conditions in periods of more
steady rain showers. Will not include IFR conditions at BWG/LEX
during the burst of rain showers tomorrow morning yet, but may need
to add if it looks like cigs will be in the lower cat.
Winds will be out of the WSW ahead of the front and then WNW behind
the front.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
Update.........AMS
Short Term.....RAS
Long Term......MJP
Aviation.......AMS