Special Weather Statement, NWS Louisville, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
959 PM EDT FRI MAY 04 2012

.Forecast Update...
Issued at 959 PM EDT May 4 2012

Convection appeared to reach a relative minimum earlier this
evening, however erosion of the mixed layer and an increasing
low-level jet impinging on the region has led to the rapid
redevelopment of convection across southern Indiana in the last hour
or so.  Currently, there are two areas of convection that we're
concerned with. The first is over our northern sections of our
southern Indiana counties.  This activity will move eastward into
far SE Indiana and possible skirt our counties in northern KY over
the next few hours.  Large hail and damaging winds will be possible
with this activity along with torrential rains and a fair amount of
lightning.  While ILN and JKL have issued flash flood watches, our
northeastern sections have not received all that much precipitation
over the last 24 hours.  Based on the latest FFG guidance we can
stand to take another round of storms with just some isolated hydro
issues.  So for now, will hold off on a flood watch, but continue to
monitor closely.

Second area of thunderstorms has re-ignited over far southwest
Indiana on the nose of a SW to NE oriented low-level jet axis.
Previous convection from late this afternoon and evening has laid
out a residual boundary from near Dubois Co Indiana SE through
Bullitt and down into Boyle and Lincoln counties.  Strong theta-e
axis was noted in the objective analysis along this boundary.  So
the current thinking is that this convection to the NW of KEVV will
slide more east-southeastward over the next few hours and affect SW
Indiana and portions of northwest/north-central KY.

For now, have gone ahead and increased PoPs upwards for the
overnight period along with cloud cover.  Will run likely Pops
across our far NE sections to capture the first wave and run high
chance PoPs across our northwest and western sections to capture the
activity to our west.

Updated forecast and products will be available shortly.

Update issued at 715 PM EDT May 4 2012

Very focused cluster of storms now moving east into the Bluegrass,
and exiting the LMK CWA. Northern half of the CWA is now worked
over, while the southern half remains under a fairly strong
mid-level cap. With the loss of daytime heating, we will be hard
pressed to sustain any convection into the Ohio Valley for the next
few hours.

Forecast confidence for the rest of the night is quite low as the
models do not have a good handle on ongoing storms. Convection
firing over Indiana and Ohio where there is less capping may congeal
into an MCS and dive south overnight, so cannot pull POPs completely
out of the forecast. Will go with a high-end chance POP after
midnight, mainly in the north and northeast sections of the CWA.

Update out shortly to include the cancellation of WW 238.

.Short Term (Tonight through Saturday night)...
Issued at 320 PM EDT May 4 2012

Main concern is in the near term, as a bowing line of thunderstorms
over SW Indiana approaches the area. Expect severe winds and
excessive lightning, mainly in the I-64 corridor for the next few
hours, and the short-term will key on that. Environment south of WW
238 is fairly capped, and POPs heading into early evening will be
limited to 20-30 in those areas. Routine forecast products will be
taking a back seat to statements and warnings, especially as this
activity traverses the Louisville Metro roughly between 5 and 6 PM.

Still taking models with a grain of salt as they have not locked on
with what is going on now. That said, still carrying low-end likely
POPs for tonight as the front drops southward to near the Ohio
River. SVR threat should be diminishing rapidly around sunset.

General trend in POP on Saturday will be downward, but it is
too difficult to time any impulses in the flow aloft. With a front
hung up across Kentucky and still a juicy atmosphere, will not drop
POPs below 20-30, and that will be late in the day. Actually taper
down to a dry forecast Saturday night.

.Long Term (Sunday through Friday)...
Issued at 310 PM EDT May 4 2012

With a weak sfc front situated over the area Sunday, isolated
showers/t-storms will be possible Sunday and Sunday evening.
However, an upper ridge will become established over the area on
Sunday limiting convective development.  A cap is apparent for Sun
afternoon on GFS soundings.

By late Sun night/early Monday morning, pre-frontal convection ahead
of an approaching cold front will enter our western forecast area.
Latest models indicate that we would be warm sectored on Monday with
convection likely in a warm moist unstable environment.  The cold
front looks to pass through the region Monday night with perhaps the
strongest convection accompanying the front or just ahead of the
front where the best dynamics are available.  It's a little tough to
nail down timing at this point, but strong to possibly severe storms
look possible Monday afternoon/night.

Sunday/Monday temperatures will be warm in the low to mid 80s for
highs and mid to upper 60s for lows.

Following the cold front, the rest of the week will be cooler
(slightly below normal).  Some lingering showers will stick around
with waves in the upper trough behind the cold front.  A rumble of
thunder may still be possible early Tues.  Models vary on how
quickly the upper trough will move east into the New England
states.  Most models follow a more progressive soln like the 12Z
GFS.  However, the ECMWF and a few ensemble members indicate a
slower solution so will keep POPs in through Wed.  May need to
remove them if models lock onto a more progressive soln.
Temperatures will be in the upper 60s to mid 70s for highs
Tues-Fri.  Thurs-Fri look dry at this point with upper ridging over
the area.

&&

.Aviation (00Z TAF Issuance)...
Updated at 710 PM EDT May 4 2012

Afternoon convection remained very focused as it rolled through SDF,
and is now passing just south of LEX, with only peripheral impacts
on those terminals. Expect the next few hours to be quiet with
mainly mid-level debris clouds, as the atmosphere has been worked
over. Later on in the overnight period and into Saturday morning we
could see convection drop in from the north as a cold front moves
south to the Ohio River.  Low-confidence forecast as there are too
many weak impulses aloft to pin down the timing of any convection,
but will carry VCTS for a few hours in the morning for SDF and LEX.
By afternoon the boundary will be far enough south of the river to
get N/NE winds in SDF and LEX, and scatter out the low cloud deck.

For BWG the boundary will not get there, so will keep the convection
out of the forecast. Light winds and plenty of low-level moisture
will support MVFR fog around daybreak. Forecast confidence is higher
in BWG than the other two sites.

&&

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

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LOUISVILLE KY
1107 PM EDT FRI MAY 4 2012

INZ076>079-083-084-089>092-KYZ023>043-045>049-053>057-061>067-
070>078-081-082-052330-
ORANGE IN-WASHINGTON IN-SCOTT IN-JEFFERSON IN-DUBOIS IN-
CRAWFORD IN-PERRY IN-HARRISON IN-FLOYD IN-CLARK IN-HANCOCK KY-
BRECKINRIDGE KY-MEADE KY-OHIO KY-GRAYSON KY-HARDIN KY-BULLITT KY-
JEFFERSON KY-OLDHAM KY-TRIMBLE KY-HENRY KY-SHELBY KY-FRANKLIN KY-
SCOTT KY-HARRISON KY-SPENCER KY-ANDERSON KY-WOODFORD KY-
FAYETTE KY-BOURBON KY-NICHOLAS KY-NELSON KY-WASHINGTON KY-
MERCER KY-JESSAMINE KY-CLARK KY-LARUE KY-MARION KY-BOYLE KY-
GARRARD KY-MADISON KY-BUTLER KY-EDMONSON KY-HART KY-GREEN KY-
TAYLOR KY-CASEY KY-LINCOLN KY-LOGAN KY-WARREN KY-SIMPSON KY-
ALLEN KY-BARREN KY-MONROE KY-METCALFE KY-ADAIR KY-RUSSELL KY-
CUMBERLAND KY-CLINTON KY-
1107 PM EDT FRI MAY 4 2012 /1007 PM CDT FRI MAY 4 2012/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL
INDIANA AND CENTRAL KENTUCKY.

.DAY ONE...OVERNIGHT.

SCATTERED THUNDERSTORMS WILL TRANSVERSE PORTIONS OF THE OUTLOOK AREA
OVERNIGHT.  THE BEST CHANCES OF THUNDERSTORMS WILL GENERALLY BE
NORTH OF THE WESTERN KENTUCKY AND BLUEGRASS PARKWAYS.  ANY STORM
WILL BE CAPABLE OF PRODUCING TORRENTIAL RAINFALL...GUSTY
WINDS...FREQUENT LIGHTNING AND HAIL.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

ISOLATED TO SCATTERED THUNDERSTORMS WILL CONTINUE TO BE POSSIBLE
SATURDAY THROUGH TUESDAY WITH UPPER DISTURBANCES AND SURFACE
FRONTS PASSING THROUGH THE REGION. THE BEST CHANCE FOR STRONG TO
POSSIBLY SEVERE STORMS WILL BE MONDAY AND MONDAY NIGHT AHEAD OF
AND ALONG A COLD FRONT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED OVERNIGHT.

MJ

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LOUISVILLE KY
1152 PM EDT FRI MAY 4 2012

INZ084-089-KYZ025-050430-
CRAWFORD-MEADE-PERRY-
1052 PM CDT FRI MAY 4 2012

...STRONG THUNDERSTORM WITH DANGEROUS LIGHTNING...HEAVY RAIN...PENNY
SIZE HAIL...AND 50 MPH WINDS...

AT 1052 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
A STRONG THUNDERSTORM 12 MILES SOUTHWEST OF ENGLISH...AND MOVING EAST
AT 25 MPH.

FREQUENT CLOUD TO GROUND LIGHTNING...HEAVY RAIN WITH RAINFALL RATES
OF AROUND ONE INCH PER HOUR REDUCING VISIBILITIES TO LESS THAN ONE
MILE...PENNY SIZE HAIL...AND STRONG GUSTY WINDS OF AROUND 45 TO 50
MPH...ARE EXPECTED WITH THIS STORM.

* THIS STORM WILL ALSO IMPACT...
  ORIOLE...
  MOUNT PLEASANT AND SULPHUR SPRINGS...
  DEUCHARS AND MAGNET...
  ALTON AND ROBERTA...

THIS STORM WILL AFFECT INTERSTATE 64 IN INDIANA BETWEEN MILE MARKERS
79 AND 92.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

FREQUENT LIGHTNING IS OCCURRING WITH THIS STORM. MOVE INDOORS IF
POSSIBLE. STAY AWAY FROM WINDOWS AND DOORS...AND AVOID USING THE
TELEPHONE UNLESS IT IS AN EMERGENCY.

IF YOU ARE IN THE PATH OF THIS STORM...SEEK SHELTER INDOORS AND STAY
AWAY FROM WINDOWS. STAY TUNED TO NOAA ALL HAZARDS RADIO...
WEATHER.GOV/LOUISVILLE ON THE INTERNET...OR LOCAL MEDIA FOR LATER
UPDATES AND POSSIBLE WARNINGS.

&&

LAT...LON 3828 8664 3824 8628 3819 8631 3819 8632
      3818 8631 3818 8632 3817 8632 3803 8641
      3816 8673
TIME...MOT...LOC 0353Z 289DEG 24KT 3819 8658

RS