Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 301713
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
113 PM EDT Sat May 30 2015

...Updated Aviation Discussion...

...Forecast Update...
Updated 920 AM EDT Sat May 30 2015

Mid-morning surface analysis reveals low pressure over southeast
Missouri and latest visible and water vapor imagery loop shows a
nice curl to the cloud features to our southwest. Mostly sunny to
sunny skies this morning across central KY into southern IN have
allowed readings to jump into the mid/upper 70s and with the trend
in any weather/precip holding to the afternoon, raised high
temperatures on average 2-5 degrees.

Early look at the 12z data shows the surface low strengthening some
as it tracks to our northwest late this afternoon and evening.
Instability on the order of 1500 to 2000 J/kg is expected to develop
by afternoon. Shear parameters will be marginal, around 25 to 35 kts
of effective shear. Soundings reveal weak mid-level lapse rates but
the fair amount of destabilization and approaching surface low, a
few strong/severe storms look possible this afternoon and early
evening. The main area would be along/west of I-65, overall lining
up with the latest SPC updated slight risk outlook.

Trended highest POPs to the 21-00z timeframe, limiting to slight
chances through early afternoon. Otherwise, no major changes to the
POPs/weather at this time.

.SHORT TERM (Now through Sunday)...
Issued at 325 AM EDT Sat May 30 2015

Sfc low pressure will strengthen and move northeast along an
advancing cold front today and tonight with the front moving through
our region tonight.  Aloft the upper level trough will follow the
sfc features mainly moving through the Ohio Valley Sun/Sun night.

Today ahead of the front, we`ll sit in a moist unstable warm
sector.  The latest short range/hi-res models indicate that some
inhibition from a lingering mid level inversion may limit morning
convection and a decent trigger for convection may not arrive until
this afternoon.  Thus, have limited POPs for this morning to 20-40%
with the best area of seeing any showers/storms being west of I-65.
By late morning or early afternoon, think that we should start to
see some weak convection start to pop as we reach convective temps
and/or perhaps a weak leading shortwave helps spur convection.

The best chance for showers/storms will arrive this evening and last
through the overnight hours as the sfc low traverses
southern/central IN.  Models indicate that the most solid precip
chances will exist along and north of the low over southern IN and
perhaps portions of northern KY (depending on exact track of the
low).  South of the low over most of central KY, think that
convection will remain more scattered in nature.  Overall, this
system isn`t a real strong one and as a result, think that severe wx
chances are fairly low.  Some of the higher-res models suggest an
MCV could form near the low pressure and provide a bit more
forcing.  This could result in a few storms with gusty winds up to
40-50 mph.

The cold front should pass through early Sun morning ending the main
precipitation chances and leaving low clouds and perhaps a few
lingering showers.

Temperatures today will be similar to the last few days with highs
in the lower 80s for most areas.  Tonight/Sunday temps will be a bit
trickier as notably cooler air spills in behind the cold front.
Tonight`s lows should range from the upper 50s/lower 60s west of
I-65 to low to mid 60s along and east of I-65.  Sunday high
temperatures should be limited to the mid to upper 60s over southern
Indiana with 70s elsewhere over central KY.

.LONG TERM (Sunday night through Friday)...
Issued at 306 AM EDT Sat May 30 2015

In the long term period, the latest model guidance continues to
maintain a similar themes from the 29/12Z package.  An upper level
system and associated weak surface low will move through the region
at the beginning of the forecast period.  As this wave passes
through, cooler and drier air looks to infiltrate the region for
much of the early part of the work week.  Highs Monday will likely
only top out in the upper 60s to the lower 70s.  Lows Monday night
look to cool into the lower 50s for most, though some of traditional
colder spots will likely drop into the upper 40s.  A moderation in
temperatures is likely on Tuesday with highs warming into the middle
70s, with highs on Wednesday pushing into the lower 80s.

By mid-late week, the model solutions continue to diverge a bit with
their upper level solutions.  In general terms, the 30/00Z runs are
in slightly better agreement overall.  The models both develop a cut
off low aloft over the southern US and the pattern suggests the
potential for some tropical development (similar to Ana from a few
weeks back).  Moisture and warmer air will continue to filter in
from the south during the period and some isolated-scattered
diurnally driven convection should develop by Thursday and Friday
afternoon.  The best chance of showers/storms look to generally be
along and east of I-65 as slightly more ridging will likely be in
place out to our west.  For now, plan on keeping iso-scattered PoPs
in the forecast for Thu-Fri.  Temperatures for Thu-Fri will be warm
with highs in the lower-middle 80s with overnight lows in mid-upper
60s.

&&

.AVIATION (18Z TAF Update)...
Updated 110 PM EDT Sat May 30 2015

Scattered to numerous showers with some embedded thunder will pass
over SDF/BWG/LEX through early this evening. Some of this activity
could be strong, with heavy rainfall and gusty winds the main
threat, reducing conditions to MVFR briefly. Tried to reflect
greatest expected coverage and confidence with tempo group.

Otherwise, front will pass through later this evening, and winds
will become southwesterly. Showers may linger through about 06z,
after which wrap around stratus deck will begin to pass over.
Upstream observations show this in the 1500 to 2000 ft, and forecast
soundings support this approach as well. It`s possible though the
clouds could brush just northwest of the TAF sites, especially at
LEX. But for now brought in a period of fuel-alternate MVFR ceilings
by 12z Sunday.

Forecast Confidence
======================
Ceilings:   Medium
Visibility: High
Winds:      High
T-storm:    Medium

&&

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

$$

Update.........ZT
Short Term.....AMS
Long Term......MJ
Aviation.......ZT




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