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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KJKL 151059
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
659 AM EDT SAT JUN 15 2013

.UPDATE...
-- Changed Discussion --
ISSUED AT 634 AM EDT SAT JUN 15 2013

VALLEY FOG HAD DEVELOPED ACROSS MANY AREAS WITHIN THE CWA...AS WAS
BECOMING EVIDENT ON IR IMAGERY. AS A RESULT...ADDED IN PATCHY TO
AREAS OF VALLEY FOG FOR THE WEATHER THROUGH 13Z. LATEST TRENDS AT WFO
JKL ARE SHOWING THE FOG BEGINNING TO LIFT AND MIX OUT AS THE SUN IS
RISING...SO DO NOT EXPECT FOG TO LINGER MORE THAN A FEW MORE HOURS.
-- End Changed Discussion --

&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 408 AM EDT SAT JUN 15 2013

FORECAST WILL START OFF WITH CONTINUED STRONG HIGH PRESSURE OVER THE
OHIO VALLEY...ALLOWING SUBSIDENCE AND RESULTING CLEAR SKIES TO
PERSIST. HOWEVER...AS THE DAY CONTINUES...THE HIGH WILL QUICKLY
BEGIN PUSHING OFF TO THE SE. THIS WILL PUT MUCH OF KY IN A SW TO W
FLOW...AS WAS MENTIONED IN PREVIOUS DISCUSSIONS...WILL ALLOW TEMPS
TO REACH THE LOW 80S ACROSS MUCH OF THE REGION. STRONG 500MB TROUGH
OVER SOUTH CENTRAL CANADA AND EXITING RIDGING TO THE SOUTH WILL PUT
MUCH OF THE OHIO VALLEY IN A MORE ZONAL PATTERN FOR SATURDAY EVENING
THROUGH THE REMAINDER OF THE FORECAST PERIOD. A SHORTWAVE DEVELOPING
ACROSS THE CENTRAL PLAINS SATURDAY EVENING WILL FOLLOW THIS ZONAL
FLOW AND REACH THE OHIO VALLEY BY LATE SATURDAY NIGHT. THIS
SHORTWAVE...COUPLED WITH INCREASED ENERGY FROM THE 500MB TROUGH NOW
POISED JUST NORTH OF THE GREAT LAKES...WILL BRING THE POTENTIAL FOR
CONVECTION TO THE NORTHERN COUNTIES LATE SATURDAY NIGHT INTO SUNDAY
MORNING...INCREASING AND MOVING SOUTHWARD DURING THE DAY SUNDAY.

WITH A SW TO W JET DEVELOPING IN THE LOW/MID LEVELS...AND A MORE
SRLY FLOW AT THE SURFACE...EXPECT SOME STRONG SHEER IN THE LOW
LEVELS SUNDAY MORNING. HOWEVER...BY AFTERNOON...DURING PEAK
CONVECTION...WINDS WILL BECOME MORE WRLY THROUGH THE SOUNDING
PROFILE. SO WHILE CONVECTION IS POSSIBLE...EXPECT MORE OF A
MULTI-CELL TYPE SITUATION WITH LESS POTENTIAL FOR ROTATION/SUPERCELL
DEVELOPMENT. THAT BEING SAID...INSTABILITY PARAMETERS ARE ALSO
SUPPORTIVE OF CONVECTIVE DEVELOPMENT...WITH ECMWF PREDICTED LAPSE
RATES REACHING 6.5 OVER EASTERN KY DURING THE AFTERNOON. AS A RESULT
OF THESE HIGHER LAPSE RATES BEING CENTERED OVER EASTERN KY...AS
WELL AS A GOOD AREA OF QVECTOR CONVERGENCE TO SUPPORT LIFT...WENT
AHEAD AND BUMPED UP POPS EARLIER IN THE DAY FOR THE EASTERN
MOUNTAINS.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 408 AM EDT SAT JUN 15 2013

THERE IS REASONABLE AGREEMENT BETWEEN THE GFS AND ECMWF TO START THE
PERIOD...BUT IT DOES NOT LAST. A WEAKENING COLD FRONT SHOULD BE
APPROACHING FROM THE NORTHWEST SUNDAY NIGHT. SOUTH TO SOUTHWEST FLOW
AHEAD OF THE FRONT WILL BRING INCREASING MOISTURE ON ISENTROPIC
LIFT...RESULTING IN A POSSIBILITY OF SHOWERS/STORMS. THE COLD FRONT
WILL STALL WITHOUT PASSING THROUGH...LEAVING US IN AN ENVIRONMENT
CONDUCIVE TO SCATTERED SHOWERS/STORMS WITH DIURNAL DESTABILIZATION
AND/OR SMALL DISTURBANCES PASSING BY. MODEL DIFFERENCES BECOME
APPARENT TO OUR WEST ON MONDAY...AS THE OPERATIONAL GFS SIGNIFICANTLY
DEEPENS A SURFACE LOW HEADING EAST FROM OKLAHOMA...WHILE THE ECMWF
DOES NOT DEEPEN IT. THIS LOW MOVES EAST THROUGH KY MONDAY NIGHT AND
TUESDAY. THE LOW IS ASSOCIATED WITH A SHORTWAVE TROUGH WHICH BOTH
THE GFS AND ECMWF DO DEPICT. THE GFS ENSEMBLE MEAN OFFERS A
COMPROMISE WITH A WEAKER SURFACE LOW THAN THE OPERATIONAL MODEL...
WHICH SEEMS REASONABLE. OUR BEST CHANCE OF RAIN IS MONDAY NIGHT WITH
THE APPROACH OF THIS SYSTEM.

WILL EXPECT PRECIP TO BE GONE BY TUESDAY NIGHT AS THE SYSTEM
DEPARTS TO THE EAST. SURFACE HIGH PRESSURE WILL DRIFT SE FROM THE
GREAT LAKES ON NW FLOW ALOFT TUESDAY NIGHT THROUGH WEDNESDAY
NIGHT...PROVIDING THE LOCAL AREA WITH A SOMEWHAT DRIER AND COOLER
AIR MASS AND FAIR WEATHER. AS THE HIGH PASSES TO OUR E...LOW LEVEL
FLOW AROUND IT WILL START TO BRING BACK A WARMER AND GRADUALLY MORE
HUMID AIR MASS THURSDAY AND FRIDAY. WILL NOT RULE OUT DEEP
CONVECTION THURSDAY OR FRIDAY...BUT THINK THAT THE PROBABILITY IS
TOO LOW TO INCLUDE IT IN THE FORECAST AT THIS POINT. PRECIP WOULD BE
MORE LIKELY OVER THE HIGHER APPALACHIAN TERRAIN TO OUR S AND E...AND
ALSO TO OUR NW IN ASSOCIATION WITH ANOTHER SYNOPTIC SCALE STORM
SYSTEM.

&&

.AVIATION...
-- Changed Discussion --
(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 658 AM EDT SAT JUN 15 2013

A HIGH PRESSURE RIDGE WILL PROVIDE MAINLY VFR CONDITIONS OVER THE
NEXT 24 HOURS. AS THE RIDGE BEGINS TO SHIFT SOUTHEASTWARD...A
SHORTWAVE WILL CONTINUE TO MOVE TOWARDS THE OHIO VALLEY. AS IT
DOES...EXPECT A SLIGHT INCREASE IN CLOUD COVER BY THE END OF THE TAF
PERIOD. MOST OF THE PRECIP/CIG CONCERN WILL REMAIN OVER THE NORTHEAST
SECTIONS OF THE STATE...WITH NO IMPACT EXPECTED FOR THE TAF SITES.
-- End Changed Discussion --

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...JMW
SHORT TERM...JMW
LONG TERM...HAL
AVIATION...JMW