Special Weather Statement, NWS Louisville, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
700 PM EDT SAT MAR 17 2012

.Update...
Issued at 653 PM EDT Mar 17 2012

Regional radar mosaics show an area of thunderstorms generally
oriented along and west of I-65.  These storms are moving slowly to
the east-northeast at 15 to 20 MPH.  Atmosphere currently is in a
weakly sheared but highly buoyant state. Axis of mixed layer CAPE is
running about 1500-2000 J/kg generally along and east of the current
thunderstorm activity while a more stable atmosphere is located to
our southwest.  Think that the atmosphere to our southwest is being
more controlled by a warmer elevated mixed layer complimented by
much weaker mid-level lapse rates.  Over the next couple of hours,
we expect convection to slowly rumble off to the east with the
highest coverage out in the I-65 corridor.

Activity will likely remain quite strong, but the lack of strong
lapse rates seems to be keeping the updraft speeds in check which is
limiting the possibility of large hail.  However, any of these
storms will be capable of producing isolated gusty winds and large
hail this evening.  I would think that we should see some weakening
and decrease of areal coverage of the storms once we approach
sunset.  However, this may only be a temporary break as we have a
mid-level wave out to the west that will be moving in overnight.
This feature may produce additional convection tonight.  However,
activity may not be as widespread depending on how much convective
overturning we see this evening with the current activity.

.Short Term (Tonight through Sunday Night)...
Updated at 250 PM EDT Mar 17 2012

Temperatures this afternoon have risen into the mid to upper 70s
across the region with dewpoints in the low 60s. Instability has
been on this rise as well with LAPS analysis showing LI's of -6
across the western portion of the forecast area to -4 across the
eastern portion. It is even more unstable to the west of the
forecast area where a line of showers and thunderstorms has
developed. The latest radar scans show additional isolated showers
and thunderstorms popping up across the forecast area. The main line
of storms will continue to move northeast through the afternoon and
early evening across central Kentucky and southern Indiana. If the
storms are able to become strong enough they will be capable of
producing hail and possibly some strong winds, though hail will be
the main threat. This activity should wane this evening with the
loss of daytime heating.

Another shortwave will cross the area overnight. Models do indicate
that this will spark additional showers and thunderstorms late
tonight, so will continue to mention scattered precip through
tomorrow morning. Rain chances will diminish tomorrow afternoon as
the
ridge aloft begins to amplify. Sunday night looks to be the start of
a couple of days of dry weather.

Temperatures will continue to be warm. Lows Sunday and Monday
morning will be in the upper 50s to lower 60s. Highs tomorrow will
be in the lower 80s.

.Long Term (Monday - Saturday)...
Updated at 245 PM EDT Mar 17 2012

First half of the week will have an amplified upper pattern, with a
deep trof working into the Rockies and a strong ridge extending up
through the Great Lakes. Precip will be suppressed Mon-Tue as the
ridge amplifies over the Ohio Valley. Expect near-record heat both
Monday and Tuesday.

Current records and forecast temps for Mon/Tues:

               Mon(3/19)      Tues(3/20)
               Record/Forecast:
Louisville     83(1907)/84    85(1894)/83
Lexington      79(1945)/81    81(1894)/81
Bowling Green  86(1907)/84    85(1921)/82
Frankfort      81(1948)/82    82(1921)/83

By Wednesday the trof will move into the Plains, and the upper ridge
will retreat just far enough east to open us up for afternoon
thunderstorms again, with the highest POPs west of Interstate 65.
Unseasonable warmth will persist yet another day, but clouds and
maybe precip will limit temps to the mid/upper 70s.

Thu-Fri the models begin to diverge, as a closed upper low develops
and makes its way east into the Tennessee Valley by Friday night.
ECMWF is about 12 hrs faster than the latest GFS with this system.
Whenever this happens expect widespread precip under the difluent
upper flow ahead of the closed low. However, still not enough
confidence in the timing to go with a likely POP, so will carry a
high-end chance POP both Thursday and Friday. Temps will trend quite
a bit cooler, especially once we get under the upper low, but will
still be above normal. Clouds and moist southerly flow will keep min
temps well above climo, generally in the 50s.

Upper low finally edges to our east on Saturday, allowing us to dry
out from west to east. Tapered down to just a slight chance in the
east, with temps only slightly above normal. It is worth noting that
this is still a low-confidence forecast, as closed upper lows are
not always handled well by the models, and if anything the models
are too fast.

&&

.Aviation (00Z TAF Issuance)...
Updated at 655 PM EDT Mar 17 2012

Scattered convection will continue through the evening hours and
affect primarily KBWG and KSDF this evening.  Most concentrated area
of convection is generally along and just west of I-65 between KSDF
and KBWG.  KBWG should see a decent amount of convection over the
next few hours as convection to the west of the terminal moves
east.  Current thinking is that convection should generally be east
of KBWG by 18/01-02Z.

Additional convection is just southwest of KSDF and is moving
northeast.  Current thinking is that convection will be likely at
KSDF through 18/01-02Z as well.

Further east at KLEX, convection is not all that widespread and more
scattered in nature.   However, the atmosphere is unstable and
scattered convection will certainly be possible through the evening
hours.  Not really sure how much of the convection out over the I-65
corridor will make it over into the KLEX terminal.  For now, plan on
keeping VCTS in the TAFs and monitor through the evening.

&&

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

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LOUISVILLE KY
716 PM EDT SAT MAR 17 2012

INZ076>079-083-084-089>092-KYZ023>043-045>049-053>057-061>067-
070>078-081-082-182000-
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-
716 PM EDT SAT MAR 17 2012 /616 PM CDT SAT MAR 17 2012/

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

.DAY ONE...THIS EVENING AND OVERNIGHT.

SCATTERED THUNDERSTORMS WILL CONTINUE THROUGH TONIGHT AS AN UPPER
LEVEL DISTURBANCE CROSSES THE REGION. HAIL AND HEAVY RAIN WILL BE
THE MAIN THREATS FROM THE STORMS...THOUGH STRONG WINDS WILL BE
POSSIBLE AS WELL. ALL THUNDERSTORMS PRODUCE LIGHTNING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

SCATTERED THUNDERSTORMS WILL CONTINUE ON SUNDAY. ALL THUNDERSTORMS
PRODUCE LIGHTNING AND BRIEF HEAVY RAINFALL.

SCATTERED THUNDERSTORMS WILL BE POSSIBLE WEDNESDAY THROUGH FRIDAY
AS AN UPPER-LEVEL LOW PRESSURE SYSTEM MOVES INTO THE TENNESSEE
VALLEY. THE CHANCES AND TIMING OF ANY STRONG TO SEVERE STORMS WILL
DEPEND ON THE STRENGTH AND TRACK OF THE UPPER LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ENCOURAGED TO REPORT ANY HAIL...DAMAGING WINDS...OR
FLOODING THROUGH SUNDAY.

EER/RAS/MJ