Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 021756
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
156 PM EDT TUE SEP 2 2014

.UPDATE...
ISSUED AT 948 AM EDT TUE SEP 2 2014

THE FORECAST FOR THIS AFTERNOON HAS BECOME COMPLICATED BY THE
REMNANTS OF AN MCS OVER THE OHIO VALLEY AND THE OUTFLOW BOUNDARY
WHICH IS CURRENTLY MOVING INTO THE BLUEGRASS. CURRENT THINKING IS
THAT THE OUTFLOW BOUNDARY WILL GENERALLY WEAKEN AS IT CONTINUES
MOVING TO THE SOUTHEAST. THIS SHOULD BE TEMPORARY AND WILL THEN BE
THE FOCUS OF DEVELOPMENT LATER IN THE AFTERNOON. SO PRETTY MUCH GOING
WITH TWO PRONGS. THE FIRST BEING REDEVELOPMENT WITH THE OUTFLOW
BOUNDARY AND THE SECOND BEING THE PREFRONTAL ACTIVITY. THE SEVERE
THREAT TODAY WILL BE EFFECTED BY HOW MUCH DEBRIS CLOUD IS ABLE TO
MOVE INTO THE AREA. THE LOW LEVEL INSTABILITY WILL BE EFFECTED BY
EFFECTED BY THE CLOUDS. THE LATEST NAM BUFFER HAS REALLY BACKED OFF
FROM YESTERDAY WITH HALF THE CAPE THAN WHAT WAS FORECAST YESTERDAY.
ALSO MISSING IS THE DRY AIR POCKETS ALOFT WHICH WOULD HAVE BEEN
HELPFUL FOR WET MICROBURSTS TO OCCUR. CAN NOT RULE OUT SEVERE
THUNDERSTORMS...HOWEVER THE CHANCES HAVE GONE DOWN. MOST LIKELY WILL
STILL SEE A COUPLE OF SEVERE STORMS WITH THIS SYSTEM. UPDATED THE
FORECAST TO REFLECT THE CURRENT CONDITIONS AND MODEL TRENDS.

UPDATE ISSUED AT 649 AM EDT TUE SEP 2 2014

NO SIGNIFICANT CHANGES MADE THIS MORNING. LINE OF SHOWERS AND STORMS
EXTENDS FROM CINCINNATI SOUTHWEST TO THE NORTHWEST SIDE OF
LOUISVILLE. THIS LINE CONTINUES TO SLOWLY WEAKEN AS IT MOVES EAST. IF
IT WERE TO HOLD TOGETHER...LOOKS LIKE IT MAY WORK INTO THE BLUEGRASS
COUNTIES AFTER 13Z. HOWEVER...GIVEN THE TREND THIS SEEMS UNLIKELY AND
AT BEST PERHAPS AN ISOLATED SHOWER CAN HOLD TOGETHER. MAIN CONCERN
CONTINUES TO BE LATER TODAY...PRIMARILY AFTER 2 PM AS OUTFLOW FROM
THIS MORNINGS CONVECTION REDEVELOPS SHOWERS AND STORMS. NOT SURE THE
COVERAGE WILL BE ALL THAT GREAT AFTER LOOKING AT THE LATEST HRRR AND
NEW 06Z MAV GUIDANCE. BOTH OF THESE MODELS HAVE BACKED OFF
SIGNIFICANTLY ON THE CHANCES OF RAIN TODAY. HOWEVER...GOING TO STAY
THE COURSE AS THE TROUGH IS STILL FAIRLY DEFINED AND OUTFLOW HAS
ALREADY DEFINED A BOUNDARY FOR NEW CONVECTION TO DEVELOP.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 330 AM EDT TUE SEP 2 2014

PRESENTLY...A SHORTWAVE TROUGH IS PUSHING INTO THE OHIO RIVER VALLEY
REGION. AN MCS DEVELOPED YESTERDAY EVENING HEAD OF THIS TROUGH AND
IS NOW MARCHING EASTWARD INTO CENTRAL/SOUTHERN INDIANA...STRETCHING
BACK TO THE SOUTHWEST ACROSS SOUTHERN ILLINOIS. IR SATELLITE HAS
SHOWN SOME WARMING WITH THE CLOUD TOPS OVER THE PAST HOUR OR
TWO...INDICATING THAT THIS MCS MAY ALREADY BE ON THE DECLINE. IN
FACT...THE HRRR SUPPORTS THE IDEA OF A DYING MCS AS IT TRIES TO PUSH
INTO CENTRAL KENTUCKY TOWARDS DAYBREAK. CANNOT RULE OUT A FEW SHOWERS
PUSHING INTO THE BLUEGRASS SHORTLY AFTER 8 AM...BUT ANTICIPATE MORE
OF THE ACTION WITH THE SHORTWAVE TROUGH WILL COME LATER THIS
AFTERNOON AS WE GENERATE SOME INSTABILITY. WITH THIS IN MIND...PLAN
TO BACK OFF THE POPS THROUGH MIDDAY WITH JUST SOME ISOLATED SHOWERS
FOR AREAS NORTH OF I-64. OUTFLOW FROM THE DYING MCS WILL BE PUSHING
ACROSS EASTERN KENTUCKY EARLY THIS AFTERNOON...AND COULD KICK START
THE CONVECTION AS IT ENCOUNTERS SOME DECENT INSTABILITY. THE FORCING
ALOFT SHOULD ALLOW FOR FAIRLY GOOD SHOWER AND THUNDERSTORM COVERAGE
BY MID TO LATE AFTERNOON. WITH BULK SHEAR VALUES OF 30-40KTS THIS
AFTERNOON...A SEVERE THREAT WOULD EXIST AS THUNDERSTORMS COULD PUT
OUT SOME DAMAGING WIND GUSTS. THE SHEAR PROFILES WEAKEN BY MID
EVENING AND THE LOSS OF DAYTIME INSTABILITY SHOULD YIELD WEAKENING
STORMS AFTER 6 PM. HOWEVER...A FEW GUSTY WINDS MAY STILL BE POSSIBLE
THROUGH 8 OR 9 PM.

THE SHORTWAVE TROUGH WILL STALL A COLD FRONT ACROSS SOUTHERN
KENTUCKY BY LATE THIS EVENING. GIVEN THE PRESENCE OF THIS
BOUNDARY...AND PLENTY OF MOISTURE...IT MAY BE POSSIBLE TO SEE
ISOLATED SHOWERS THROUGH THE NIGHT ACROSS THE SOUTHERN HALF OF
KENTUCKY. THIS BOUNDARY WILL LINGER AROUND INTO WEDNESDAY AND WITH
INSTABILITY AGAIN RAMPING UP DURING THE AFTERNOON...WE COULD BE
LOOKING AT A FEW MORE ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS. HOWEVER...BY WEDNESDAY...VERY LITTLE SHEAR IS
PRESENT...SO WE SHOULD SEE MORE ORDINARY THUNDERSTORMS WITH NO SEVERE
THREAT.

TEMPERATURES OVER THE NEXT 2 DAYS SHOULD BE FAIRLY SIMILAR TO WHAT WE
HAVE SEEN LATELY WITH HIGHS INTO THE LOW TO MID 80S. SAME CAN BE SAID
FOR LOWS TONIGHT WITH READINGS GENERALLY AROUND 70.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 418 AM EDT TUE SEP 2 2014

THE FRONTAL BOUNDARY REFERENCED IN THE SHORT TERM WILL BE DISSOLVING
EARLY IN THE LONG TERM PERIOD...BUT THERE SHOULD STILL BE DRY AIR IN
PLACE WEDNESDAY NIGHT...ESPECIALLY ALOFT. IF ANY CONVECTIVE PRECIP
CAN DEVELOP OFF OF LOW LEVEL MOISTURE ON WEDNESDAY AFTERNOON...IT
SHOULD DIE OUT BY NIGHT AS HEATING IS LOST AND SUPPORT ALOFT WILL
LIKELY BE LACKING.

DEEPER MOISTURE WILL MAKE A COMEBACK LATE IN THE WEEK AND MAY FUEL
A RESURGENCE OF SHOWERS AND THUNDERSTORMS...BUT A SUBTROPICAL RIDGE
ALOFT OVER THE SE CONUS WILL HELP TO KEEP COVERAGE LIMITED FOR A
WHILE. THE RIDGE WILL WEAKEN AND GET SUPPRESSED BY A BROAD TROUGH
DROPPING SE INTO THE NE CONUS DURING THE WEEKEND. THIS WILL ALLOW A
COLD FRONT TO MOVE INTO OUR REGION FROM THE NW. THE SCENARIO WILL
ALLOW AN INCREASE IN PRECIP COVERAGE...WITH A PEAK EXPECTED ON
SATURDAY. EVEN THOUGH THE FRONT SHOULD PASS BY SUNDAY...THE MODELS
STILL LEAVE SOME QUESTION AS TO HOW EFFECTIVE THE FRONT WILL BE AT
BRINGING IN A DRIER AIR MASS. HAVE HELD ONTO LOW POPS IN THE
AFTERNOON AND EVENING ON SUNDAY AND MONDAY...ESPECIALLY IN OUR SE
COUNTIES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 156 PM EDT TUE SEP 2 2014

EASTERN KENTUCKY IS PRIMED FOR THUNDERSTORMS AS MOIST AND UNSTABLE
CONDITIONS ARE PREVALENT ACROSS THE AREA. THERE IS AN OLD OUTFLOW
BOUNDARY BISECTING THE AREA WHICH WE ARE WATCHING AS A FOCAL POINT
FOR CONVECTIVE INITIATION AND THERE IS ALSO A FRONT WHICH IS MOVING
TOWARD THE AREA FROM THE NORTHWEST WITH LOTS OF PREFRONTAL CONVECTION
OUT AHEAD OF IT. MAINLY VFR CONDITIONS ARE EXPECTED AT THE TAF SITES
THIS AFTERNOON AND EVENING EXCEPT FOR IN THE VICINITY OF THE
THUNDERSTORMS AND RAIN SHOWERS. PUT SOME TEMPO CONDITIONS IN THE TAF
AS THE BEST ESTIMATE AS TO WHEN THUNDERSTORMS ARE MOST LIKELY AFFECT
THEM. EXPECT SOME VLIFR TO FORM AT THE TAF STATIONS AS WELL AS THE
VALLEYS LATER THIS EVENING AS THE CONVECTION MOVES OFF TO THE SOUTH
AND EAST.

&&

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

$$

UPDATE...JJ
SHORT TERM...KAS
LONG TERM...HAL
AVIATION...JJ





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