Area Forecast Discussion
Issued by NWS Jackson, KY

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750
FXUS63 KJKL 062005
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
405 PM EDT FRI MAY 6 2016

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 358 PM EDT FRI MAY 6 2016

THE RECENT OMEGA BLOCKY PATTERN WILL BEGIN TO BREAK DOWN TO START
THE WEEKEND AS THE UPPER LOW NOW OVER THE MID ATLANTIC STATES
WILL DRIFT NORTH AND THEN OFF THE EASTERN SEABOARD. THIS UPPER LOW
WILL EVENTUALLY BEGIN TO MERGE WITH AN UPPER LEVEL LOW MOVING
SOUTHEAST FROM THE HUDSON BAY REGION INTO THE JAMES BAY AREA
THROUGHOUT THE PERIOD. A SHORTWAVE TROUGH AROUND THE UPPER LOW AND
INTO THE GREAT LAKES REGION LATE TONIGHT AND ON SATURDAY AND THEN
ACROSS THE UPPER OH VALLEY REGION AND INTO THE NORTHEAST SATURDAY
NIGHT. IN ADVANCE OF THIS SHORTWAVE TROUGH...A SFC LOW WILL TRACK
ACROSS ONTARIO AND INTO EASTERN QUEBEC AND THE ST LAWRENCE VALLEY
BY THE END OF THE PERIOD. A TRAILING COLD FRONT WILL PUSH SOUTH
INTO THE OHIO VALLEY REGION LATE SATURDAY SAGGING AS FAR SOUTH AS
THE JKL CWA BY THE END OF THE PERIOD AS IT BEGINS TO STALL IN
RESPONSE TO RISING HEIGHTS ACROSS THE SOUTHEAST.

CU SHOULD DISSIPATE AROUND OR SHORTLY AFTER SUNSET AND ALLOW FOR
VALLEY LOCATIONS TO DECOUPLE RATHER QUICKLY. THIS SHOULD SET THE
STAGE FOR VALLEY LOCATIONS COOLING WELL INTO THE 40S AND VALLEY
FOG TO FORM. THIS FOG COULD BECOME DENSE PENDING TIMING OF
ANTICIPATED INCREASE IN CLOUDS LATE. THE CLOUDS ARE EXPECTED AS AN
AREA OF ISENTROPIC LIFT ASSOCIATED WITH A WEAK MID LEVEL WAVE
BEGINS TO WORK IN DURING THE SECOND HALF OF TONIGHT AND INTO THE
DAY ON SATURDAY. CLOUDS SHOULD INCREASE LATE TONIGHT AND A FEW
SPRINKLES OR ISOLATED SHOWERS CANNOT BE RULED OUT TOWARD DAWN IN
THE WESTERN PART OF THE AREA...AND DURING THE MORNING HOURS ACROSS
THE REMAINDER OF THE AREA. DAYTIME HEATING AND INCREASING MOISTURE
AHEAD OF THE APPROACHING COLD FRONT COULD LEAD TO MLCAPE OF 1000
J/KG OR MORE ACROSS THE NORTH AND EASTERN PART OF THE AREA BY
EARLY EVENING WITH OTHER INSTABILITY INDICES GENERALLY MARGINALLY
UNSTABLE. MID LEVEL FLOW WILL ALSO INCREASE AHEAD OF THE
FRONT...AND MIXING COULD LEAD TO GUSTS AS HIGH AS THE 25 TO 30 MPH
RANGE ON SATURDAY AFTERNOON. CONFIDENCE IN THE EVOLUTION AND
TIMING OF CONVECTION IS NOT EXTREMELY HIGH...BUT THE BEST CHANCE
OF CONVECTION IN MOST LOCATIONS SHOULD BE AROUND SUNSET...IF NOT
AFTER WHEN UPPER LEVEL FORCING IS BEST. A FEW OF THE STORMS COULD
BECOME STRONG TO PERHAPS LOCALLY SEVERE MAINLY IN NORTHERN
LOCATIONS ALONG AND NORTH OF THE MTN PARKWAY.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 336 PM EDT FRI MAY 6 2016

A COLD FRONT IS EXPECTED TO BE SLOWLY SINKING SOUTHWARD THROUGH THE
AREA AS THE PERIOD STARTS...AND SHOWERS MAY BE ONGOING IN SOME
LOCATIONS. THE FRONT IS EXPECTED TO STALL NEAR OUR SOUTHERN
BORDER...AND THEN REVERSE AND HEAD BACK NORTH AS A WARM FRONT IN
RESPONSE TO A LARGE AREA OF LOW PRESSURE OVER THE CENTRAL PLAINS.
THE WARM FRONT SHOULD PASS THROUGH THE JKL FORECAST AREA ON SUNDAY
NIGHT AND MONDAY MORNING. THE PROXIMITY OF THE FRONT WILL KEEP THE
THREAT OF PRECIP ALIVE...BUT THE BETTER UPPER LEVEL SUPPORT AND
BETTER FLOW OFF THE GULF OF MEXICO WILL BE MUCH FURTHER TO OUR WEST
ON SUNDAY AND MONDAY. THE ENTIRE REGIME WILL SHIFT EASTWARD...AND WE
WILL SEE A HIGHER POP IN OUR AREA ON TUESDAY/TUESDAY NIGHT AS A
WEAKENED PIECE OF THE CENTRAL PLAINS SYSTEM MOVES BY TO OUR NORTH.
THERE ARE SOME MODEL DIFFERENCES WHICH BECOME MORE APPARENT AT THIS
POINT...WITH THE 00Z ECMWF SHOWING SOME DEGREE OF PHASING WITH AN
UPPER TROUGH DROPPING THROUGH NEW ENGLAND...AND THE GFS MUCH MORE
RESERVED. THERE ARE ALSO DIFFERENCES HANDLING AN UPPER LEVEL SYSTEM
MOVING ACROSS THE NORTH CENTRAL CONUS. AT THE SURFACE...THE RESULT
HAS THE 00Z ECMWF DROPPING THE FRONT BACK SOUTH THROUGH THE AREA ON
WEDNESDAY DUE TO A GREATER INFLUENCE FROM THE FIRST SYSTEM PHASING
WITH THE NORTHEAST CONUS TROUGH. MEANWHILE... THE GFS DOES NOT HAVE
ANOTHER COLD FRONTAL PASSAGE UNTIL THURSDAY...AND THIS IS A WEAK
FRONT IN ASSOCIATION WITH THE WAVE MOVING ACROSS THE NORTHERN CONUS.
THE 00Z ECMWF ALSO HAS A COLD FROPA DUE TO THE NORTHERN SYSTEM...BUT
IT IS SLOWER AND DOES NOT OCCUR UNTIL THURSDAY NIGHT AND FRIDAY.
WITH SUCH INCONSISTENCY...THERE IS NOT GOOD CONFIDENCE IN THE
OUTCOME AFTER TUESDAY...AND A BROADBRUSHED BLEND IS USED.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 212 PM EDT FRI MAY 6 2016

CU AND ISOLATED TO SCATTERED SHOWERS HAVE DEVELOPED ACROSS THE
EASTERN PARTS OF THE REGION GENERALLY SOUTH AND EAST OF JKL AND
NEAR SJS UNDER THE INFLUENCE OF A DEPARTING UPPER LEVEL LOW. VCSH
HAS BEEN INCLUDED FOR SJS AND JKL FOR THE NEXT FEW HOURS. BRIEF
MVFR IS POSSIBLE IN LOCATIONS THAT RECEIVE A DIRECT HIT FROM A
SHOWER. OTHERWISE...NORTHERLY WINDS AT NEAR 10KT WITH SOME GUSTS
AS HIGH AS 20KT ARE EXPECTED THROUGH SUNSET AT THE TAF SITES WITH
CU OR STRATOCU IN THE VFR RANGE. WINDS SHOULD THEN SLACKEN...ALTHOUGH
THEY COULD BECOME GUSTY LATE IN THE PERIOD...AROUND 15Z...MAINLY
AT SYM...LOZ...AND SME. VALLEY FOG SHOULD AGAIN FORM AND MAY
LIMIT VIS TO IFR RANGE BETWEEN 4Z AND 13Z IN SOME AREAS...BUT IS
NOT EXPECTED AT THE TAF SITES. A DISTURBANCE WILL BRING INCREASE
MID LEVEL CLOUDS AFTER 8Z AND CIGS DOWN NEAR 5KFT WILL BE POSSIBLE
ALONG WITH A STRAY SHOWER. FOR THE MOST PART THOUGH...VFR SHOULD
PREVAIL THROUGH THE PERIOD.

&&

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

$$

SHORT TERM...JP
LONG TERM...HAL
AVIATION...JP



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