Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 200517
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
117 AM EDT Wed Aug 20 2014

...Updated Aviation Discussion...

...Mesoscale Forecast Update...
Issued at 1215 AM EDT Wed Aug 20 2014

A strong thunderstorm continues to traverse central KY early this
morning.  This cell contains numerous lightning strikes and very
heavy rainfall.  This cell continues to show up-ticks in updraft
cores and the latest was strong enough to prompt a t-storm warning.
1 inch hail and/or damaging winds are expected.  Numerous tree
branches/limbs have been reported down near Leitchfield with pea
size hail.  This cell looks to be on the southwest side of a small
MCV that has developed over central KY.  Will need to keep a close
eye on this complex as it moves east through central KY over the
next few hours.  Furthermore, additional weak storms are developing
over northern KY and southern IN early this morning in an
environment with plentiful elevated instability and modest wind
shear.

...Forecast Update...
Issued at 815 PM EDT Tue Aug 19 2014

Convection over central Indiana is struggling to get organized, and
storms over western Kentucky pretty much fizzled over the Pennyrile
region as they ran into a lot more convective inhibition. Mid-level
wave still has yet to cross the area, and might get some help from a
modest 20 kt southwesterly low-level jet that is expected to
develop. Overall trend is to lower POPs overnight, now tapering from
a 40 POP over southern Indiana to 20 POP south of the Western
Kentucky and Bluegrass Parkways. However, even that seems generous,
and the window for any strong/severe storms may be closing as well.

At this time will start to nudge POPs downward, and continue to
monitor trends another hour or so before trying to tone down the HWO
too much.

.SHORT TERM (Now through Wednesday Night)...
Issued at 334 PM EDT Tue Aug 19 2014

Somewhat of a complicated and low confidence forecast in the near
term.  Currently, partly to mostly sunny skies were noted across the
forecast area.  Temperatures ranged from the lower to middle 80s in
the Bluegrass and central locations to the upper 80s over the far
southwestern areas near Bowling Green.  Insolation is near its
maximum and highs for the day will likely occur very shortly.

Satellite and regional radar composites show a band of convection
working in from the west.  This is ahead of a mid-level wave
rotating around a large closed 500 hPa center well to our north. A
remnant MCV can be seen in the satellite imagery out near St. Louis
and will work eastward into Indiana this afternoon.  As the
afternoon wears on, expect convective inhibition to decrease out
ahead of the approaching MCV.  This should result in a marked uptick
in convective activity to our west which will spread eastward.  The
activity will likely decrease in intensity somewhat as it outruns
the instability axis to the west and also starts to feel the
influence of the loss of daytime heating.

With this said, feel that high PoPs are justified out west of
Interstate 65 later this afternoon and evening.  This afternoon`s
convection is likely to be strong to severe with damaging winds and
large hail being the primary severe weather threats.  However,
expect wind damage to become the primary threat as the line moves on
off to the east this evening/tonight.  Will carry PoPs into the
east, but slightly later than in previous forecasts.  Generally
expect convection to be largely diminished after midnight.
Temperatures this evening will cool back into the upper 70s to the
lower 80s...with overnight lows cooling back into the lower 70s.
We`ll also be on close watch for the reformation of fog tonight.
Overall, current indications suggest it will not be as widespread as
this morning...but it could be locally dense in some locations.

For Wednesday/Wednesday night, expect another day of diurnally
driven convection with an enhancement during the late
afternoon/evening hours as another mid-level wave approaches the
region.  Convection on Wednesday still looks to be generally
scattered in nature, so plan on continuing scattered coverage at
this time.  Instability will be on the increase during the afternoon
hours, so some strong to severe convection can not be ruled out once
again.  Mid-level shear is only forecast to be around 30-35kts, so
organized convection looks likely with multicelluar clusters moving
through the region posing a threat of wind damage.  Still plan on
cutting temperatures a bit as most model guidance is still
exhibiting a warm bias.  Highs on Wednesday will warm into the
middle 80s in the NE with middle-upper 80s in the central sections
and around 90 across the south/southwestern sections.

.LONG TERM (Thursday through Tuesday)...
Issued at 311 PM EDT Tue Aug 19 2014

...Hot weather expected through early next week...

A warm front will be pushing north across the region at the
beginning of the long term. Aloft a strong ridge will build in from
the south and remain in place through Sunday morning. It will then
begin to break down a bit Monday into Tuesday as a weak front
approaches from the northwest.

Thursday into Thursday night we will see another round of storms as
the front continues its push northward. Most of the area could see
storms but the best chance will be across southern Indiana and
north/east central KY. Some of the storms could be strong to
marginally severe across this area. There is some uncertainty still
in how strong the storms will be given previous multiple rounds of
storms and uncertainty in the position of the warm front. If they do
develop, gusty winds and hail would be the main concerns.

As the ridge builds in through this weekend the areas with the
storms chances will continue to push northeast leaving areas in the
southwest dry. By the end of the weekend into early next week, rain
chances decrease, so will keep the forecast dry Sunday night into
Monday.

The bigger story for the end of the week into early next week will
be the heat. As the ridge builds in temperatures will be on the
rise. From Friday through Monday high temperatures will range from
the lower to mid 90s, with the potential for upper 90s if the dry
conditions can persist over the southwest. Combined with dewpoints
in the upper 60s to lower 70s, heat index values will rise into the
upper 90s to lower 100s each afternoon.

&&

.AVIATION (06Z TAF Update)...
Issued at 110 AM EDT Wed Aug 20 2014

The main TAF concerns will be any light br this morning and
convection timing.  First of all, the convection in the area early
this morning looks to impact perhaps the LEX TAF with a rain shower
over the next few hours before moving out of the region.  Will need
to keep an eye on the convective complex over central Indiana as it
slowly makes progress southward toward SDF/LEX this morning.  It is
weakening and most short range models do not have it making it into
these TAF sites early this morning so will not include in the
SDF/LEX TAFs at this point although will watch closely.

The next concern is light br formation around sunrise. Went ahead
and backed off of vsbys some with this TAF issuance as the mixy
atmosphere with a 20 kt LLJ expected during the pre-dawn hours
should limit fog density.  Will hold BWG/LEX at MVFR conditions
around sunrise and SDF at VFR.

This evening another convective complex is expected to develop to
our northwest and dive south/southeast into the area.  Ahead of this
complex of storms, additional cells may form over central KY.  Felt
confident enough to include VCTS at the TAF sites for this issuance
as models have been persistent with this round of convection.
However, timing may need to be adjusted throughout the day today.

Winds will remain out of the SSW through the TAF period generally 7
kts or less except in t-storms.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&

$$

Mesoscale......AMS
Update.........RAS
Short Term.....MJ
Long Term......EER
Aviation.......AMS




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