000
FXUS63 KLMK 230138
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
937 PM EDT WED MAY 22 2013

.Forecast Update...
Issued at 930 PM EDT Wed May 22 2013

Most showers have exited our eastern forecast area, with just a few
isolated showers remaining which will continue to move east and
slowly dissipate. Skies have become mostly clear over western and
into central Kentucky at this time behind the departing showers.
Meanwhile, a few heavier showers have popped up over central Indiana
and eastern Illinois, but the trajectory of these suggest they will
remain north of our forecast area. The exception is a shower over
Orange County, Indiana at this time which may move into Washington
County but should not be long-lived.

Otherwise, it should remain dry overnight. Residual lower-level
moisture may result in areas of clouds later tonight, so will go
with a generic partly cloudy in the forecast. Patchy fog is still
expected by and before daybreak Thursday morning given favorable
conditions for some fog development in at least some areas,
including river valleys and cooler low-lying regions. Overnight lows
appear on track, although did adjust downward a degree or two in
some locations.

No major changes made to forecast on Thursday. Lower clouds
associated with mid-level trough should advect east and southeast
into the region accompanied by scattered showers during the day.

.Forecast Update...
Issued at 755 PM EDT Wed May 22 2013

Scattered showers and isolated thunderstorms continue over central
Kentucky east of Interstate 65 at this time. Storms are showing a
weakening trend which will continue this evening as precipitation
slides east the rest of the evening. Satellite imagery shows
clearing skies to the west of the rain over the western half of
Kentucky at this time. Looks like the rest of the night will be
partly cloudy at worst after the main moisture axis gets pushed
east. Still looks like some patchy fog overnight given the clearing,
residual low-level moisture, and the scattered rains this afternoon
and evening.

.Forecast Update...
Issued at 615 PM EDT Wed May 22 2013

A few bands of convection have been steadily progressing northeast
through the forecast area late this afternoon, and will continue to
do so this evening. The showers and storms will begin to wane this
evening as diurnal heating ends and low-level lapse rates decrease.
Storms earlier resulted in a couple reports of penny size hail and a
few trees down in Barren County in south central Kentucky.
Otherwise, storms have been below severe limits and will remain that
way early this evening as they progress across east-central
Kentucky. Nevertheless, brief heavy rain, pea size hail, and gusty
surface winds are still possible for the next hour or so with the
strongest cells.

The last band of scattered showers and storms should represent the
end of precipitation chances for the rest of the night, with partly
cloudy skies. Given abundant low-level moisture, partial clearing,
and areas of rain this afternoon and early evening, patchy fog is
expected overnight and early Thursday morning.

&&

.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 (00Z TAF Issuance)...
Issued at 715 PM EDT Wed May 22 2013

Scattered showers and storms continue early this evening over east
half of forecast area, including around LEX. These will move east
out of area this evening, while SDF and BWG should remain rain free
the rest of the night now that most cells have pushed east of these
sites. After rain passes, conditions will be partly cloudy with good
visibility (VFR). Late tonight (after about 09z), patchy fog is
expected given residual low-level moisture, partial clearing, and
surface temperatures cooling to near dewpoint. For now, will place
visibilities in MVFR category.

On Thursday, upper trough will pass through bringing broken to
overcast lower clouds. They should be right on the edge of VFR and
MVFR, and have gone MVFR at SDF and LEX, and VFR at BWG for clouds.
Isolated to scattered showers and perhaps a low-top thunderstorm is
expected in the afternoon especially over northern half of forecast
area. Thus, will carry VCSH at SDF and LEX for now.

&&

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


Update...........TWF
Short Term.......RAS
Long Term........MJP
Aviation.........TWF