000
FXUS63 KLMK 230508
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
107 AM EDT THU MAY 23 2013

...Updated Aviation Discussion...

.Short Term (Tonight through Thursday night)...
Issued at 310 PM EDT Wed May 22 2013

Deep moisture continues to feed north through the Ohio Valley today,
as the surface cold front extends southward from low pressure over
Wisconsin through Illinois into southeast Missouri. A series of
impulses aloft will round the base of the upper trough and swing NE
through the Ohio Valley through tonight, getting sheared out as they
move through. Extensive mid-level cloud cover has kept us stable,
but showers and a few thunderstorms have blossomed over the last
hour.

Main challenge in the first few hours is severe potential, which is
looking more and more limited due to the failure to destabilize.
Will keep with the likely POP until just before sunset, but it will
be mainly showers and a few garden-variety thunderstorms.

The surface front that will move through tonight is fairly diffuse,
so we still expect decent low-level moisture to remain in place. The
main upper trough will swing through Thursday afternoon, triggering
showers and low-topped thunderstorms. With the cold pool aloft, a
few of the stronger storms over the north and east could drop some
small hail. Will taper POPs from 50 over southeast Indiana and the
Bluegrass to 30 along the Tennessee border.

After a mild and initially muggy night tonight, Thursday will begin
a period of below-normal temps. Highs will reach the lower/mid 70s,
with unseasonably chilly Thursday night mins in the upper 40s on
Thursday night.


.Long Term (Friday - Wednesday)...
Issued at 300 PM EDT Wed May 22 2013

Distinctly cooler air with low dewpoints will build in behind the
departed cold front for Friday and continue into the weekend. Even
with clearing skies, Friday will stay quite cool, with northerly
winds and highs ranging from the middle 60s to right around 70
degrees. Temperatures will slowly moderate to low and mid 70s by
Sunday, as ridging aloft edges back over the Lower Ohio Valley.
Expect lows generally in the low to mid 40s Saturday morning.

By late Saturday, ridging will take hold across the southern Plains,
with northwest flow aloft developing across the Ohio Valley. A warm
front will move northward, with moisture beginning to pool late
Sunday along and north of this boundary. Guidance suggests a
weakening area of showers and perhaps storms approaching the
forecast area from the northwest late Saturday, but believe we will
be too dry in the lower levels for any thing to survive, other than
clouds. So, temperatures Sunday morning should be several degrees
warmer with the added cloud cover closer to dawn. For Sunday, the
warm front is forecast to stretch along a line from northern
Missouri southeastward into Kentucky, and slowly shifting north
during the remainder of the extended forecast period. However, there
remains a lot of model spread with the placement of this boundary,
which makes temperatures and rain chances difficult a forecast.

Still expect isolated to scattered convection to periodically
develop along this boundary and propagate in waves southeastward.
Using an ensemble approach, it appears convection should develop
upstream and propagate southeast into our area late Sunday into
Monday morning, and another round late Monday into Tuesday morning
before rain chances shift north with the warm front.

Heights and temps aloft increase nicely through next week, with warm
southerly surface winds expected as the warm front slides north.
High temperatures ranging from the middle 70s to around 80 degrees
Monday will give way to generally middle 80s by Wednesday.

&&

.Aviation (06Z TAF Issuance)...
Issued at 115 AM EDT Thu May 23 2013

A surface trough will move southeast of the Ohio River and move
across SDF around 06 to 07z early Thursday morning. A thin line of
scattered showers may hold together and bring brief rain at or
around SDF in this time frame. This line of showers is expected to
weaken and not affect LEX or BWG during the pre-dawn hours.

Mostly clear skies will continue through the middle morning hours at
LEX and BWG. Patchy light fog may develop at LEX and BWG in the 09
to 12z time frame with brief MVFR visibilities. At SDF, with the
passage of these scattered showers, brief broken ceilings will stay
mostly above the MVFR threshold.

Partly cloudy and dry conditions are expected through the early
afternoon hours on Thursday. Skies will likely become broken to
overcast at some point during the afternoon. However cloud bases
will stay above the MVFR threshold. Scattered showers are expected
Thursday afternoon with perhaps around 30% coverage. Will place VCSH
in the TAFs for a few hours.

Winds will stay from the southwest around 5kt through around dawn,
then veer to the west by mid to late morning as they increase to
around 5 to 10kt. By early afternoon, west winds will increase to 12
to 16kt with some gusts up to 20kt. Winds will rapidly shift to the
northwest at around 10 to 15 mph by early evening as a cold front
moves through.

&&

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


Short Term.......RAS
Long Term........MP
Aviation.........JSD