Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 200725
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
325 AM EDT SAT SEP 20 2014

.UPDATE...
ISSUED AT 140 AM EDT SAT SEP 20 2014

HOURLY GRIDS HAVE BEEN FRESHENED UP BASED ON RECENT OBSERVATIONS AND
TRENDS. THIS LED TO SLIGHTLY COLDER MIN T IN A COUPLE OF SPOTS ACROSS
THE NORTH...WITH THE MAIN CHANGE BEING MORE FOG IN THE GRIDS FOR
VALLEY LOCATIONS OUTSIDE OF THE HIGHEST TERRAIN WHERE THE PRESSURE
GRADIENT WAS WEAKER. WE HAVE RECEIVED A SPOTTER REPORT OF DENSE FOG
NEAR THE RED RIVER IN POWELL COUNTY AND 11-3.9 SAT IMAGERY SUPPORTS
VALLEY FOG AT PRESENT IN PARTS OF THE LIKING...BIG SANDY...KENTUCKY
AND RED RIVER VALLEYS. SOME OF THE FOG SHOULD AGAIN BE DENSE
GENERALLY ALONG THE LARGER CREEKS AND STREAMS AND ESPECIALLY RIVERS
AND LARGER LAKES. THE PRESSURE GRADIENT IS EXPECTED TO RELAX A BIT
OVERNIGHT ACROSS THE SOUTHEAST PART OF THE CWA SO OUTSIDE OF WHERE
SOME CLOUDS DEVELOP IN THE WARM SECTOR...VALLEY FOG SHOULD ALSO
DEVELOP THERE TOWARD DAWN.

SOME OF THE GUIDANCE INDICATES THE POTENTIAL FOR A FEW STRAY SHOWERS
AS A WEAK DISTURBANCE APPROACHES...MAINLY ACROSS THE WESTERN AND
NORTHWESTERN PARTS OF THE CWA LATER TONIGHT INTO EARLY ON SATURDAY.
CONFIDENCE IN THIS IS NOT ALL THAT HIGH...BUT IT DOES HAVE SUPPORT
FROM THE NAM...SOME OF THE RECENT HRRR RUNS AND SOME PRIOR BUT NOT
THE MOST RECENT RAP RUN. WE WILL CONTINUE TO EVALUATE THIS POTENTIAL
FOR THE SCHEDULED MORNING FORECAST RELEASE.

UPDATE ISSUED AT 1027 PM EDT FRI SEP 19 2014

USED OBSERVED TEMPERATURES AND DEW POINTS TO ADJUST HOURLY GRIDS FOR
TONIGHT...BLENDING TOWARD THE PREEXISTING FORECAST BY MORNING. NO
SUBSTANTIVE CHANGES TO THE OVERALL FORECAST WERE MADE.

UPDATE ISSUED AT 729 PM EDT FRI SEP 19 2014

HAVE UPDATED TO ALLOW FOR A FASTER DROP IN VALLEY TEMPS THIS
EVENING. ALSO...REDUCED SKY COVER FOR MOST AREAS THIS EVENING.
MESOSCALE MODELS ARE PERSISTENT IN SHOWING CLOUDS DEVELOPING NEAR OUR
WESTERN BORDER LATE TONIGHT INTO SATURDAY MORNING...A WELL AS SOME
SHOWERS. HAVE ACCOUNTED FOR A FEW CLOUDS...BUT KEPT THE FORECAST IN
THE JKL FORECAST AREA DRY AT THIS POINT.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 307 PM EDT FRI SEP 19 2014

A LARGE DOME OF HIGH PRESSURE WILL REMAIN ANCHORED OVER THE EAST
COAST INTO THE WEEKEND...PROVIDING A DRY START TO THE WEEKEND. STILL
A REMOTE CHANCE OF AN ISOLATED SHOWER ACROSS PIKE COUNTY LATER THIS
EVENING...BUT CHANCES SEEM TO BE DIMINISHING WITH EVERY HOUR THAT
PASSES. THE CU JUST DOES NOT LOOK ALL THAT IMPRESSIVE.
REGARDLESS...UNTIL INSTABILITY WANES THIS EVENING CANNOT RULE OUT A
BRIEF POP UP SHOWER. SKIES WILL CLEAR OUT AGAIN TONIGHT. WITH
DEW POINTS CLIMBING HIGHER TODAY...AND CLEARING SKIES...ANOTHER NIGHT
OF FOG CAN BE EXPECTED ACROSS THE AREA. SHOULD BE A FAIRLY TYPICAL
FOG FOR THIS TIME OF YEAR. HIGHS WILL CLIMB TO THE HIGHEST READINGS
OF THE WEEK ON SATURDAY AS TEMPERATURES CLIMB INTO THE LOW 80S DURING
THE AFTERNOON. CLOUDS WILL BE ON THE INCREASE SATURDAY NIGHT AS A
COLD FRONT PUSHES SOUTH INTO THE OHIO RIVER VALLEY. PRECIPITATION
ASSOCIATED WITH THIS BOUNDARY COULD MAKE IT INTO AREAS NORTH OF 1-64
PRIOR TO 12Z SUNDAY...BUT IT APPEARS THE MAIN PRECIPITATION WITH THE
FRONT SHOULD COME COME LATER ON SUNDAY. WITH CLOUDS AND SURFACE
MOISTURE INCREASING SATURDAY NIGHT...A MILDER NIGHT IS ON TAP WITH
LOWS ONLY INTO THE 60S.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 324 AM EDT SAT SEP 20 2014

A QUICK MOVING COLD FRONT WILL BE EXITING THE REGION AS OF 0Z MONDAY.
MODELS CONTINUE TO COME INTO A BETTER AGREEMENT FOR THE ENDING TIME
OF PRECIP ASSOCIATED WITH THE FRONT...WITH THE NW EXPECTED TO CLEAR
OUT BY 0Z...AND FINALLY THE SE JUST AFTER 6Z MONDAY. LATEST FORECAST
SOUNDINGS ARE STILL ONLY SUPPORTING MARGINAL INSTABILITY FOR THE
PRECIP ACCOMPANYING THIS FRONT...QUICKLY DISSIPATING AS WE LOSE
DAYTIME HEATING...AND ONCE THE FRONTAL BOUNDARY HAS PASSED. AS
SUCH...THUNDER WAS MENTIONED IN PREVIOUS FORECAST PAST 0Z...AND HAS
ALSO BEEN INCLUDED BY SURROUNDING OFFICES THROUGH THE FIRST PART OF
THE EVENING. DID NOT FEEL CONFIDENT ENOUGH TO YANK MENTION OF THUNDER
COMPLETELY AT 0Z...SO KEPT MENTION OF SLIGHT CHANCE THUNDER WITH
CHANCE POPS THROUGH 3Z...WHICH CONSEQUENTLY IS ABOUT THE SAME TIME
CHANCE POPS EXIT THE REGION ANYWAYS. THERE IS SOME CONCERN THAT THE
COMBINATION OF STRONG SUBSIDENCE BEHIND THE FRONT...IN ADDITION TO
THE LINGERING MOISTURE ACROSS THE REGION...WILL LEAD TO A WIDESPREAD
FOG EVENT BY LATE SUNDAY NIGHT...OR PERHAPS A LOW STRATUS EVENT. THE
EXTENT OF EITHER OF THESE IS STILL SOMEWHAT UNCERTAIN. DECIDED TO
INCREASE CLOUDS SLIGHTLY OVERNIGHT SUNDAY NIGHT/MONDAY MORNING...BUT
DID NOT MENTION FOG AT THIS TIME.

AS THE FRONT QUICKLY DEPARTS SUNDAY EVENING/NIGHT...KY WILL FIND
ITSELF ON THE BACKSIDE OF THE UPPER LEVEL TROUGHING PATTERN...WITH
STRONG NW FLOW BRINGING MUCH COOLER CANADIAN AIR INTO THE REGION. AS
HIGH PRESSURE TAKES HOLD...DRY AND SUNNY SKIES WILL PREVAIL DURING
THE DAY MONDAY...BUT HIGH TEMPERATURES WILL STRUGGLE TO MAKE IT TO
THE 70 DEGREE MARK. AIRMASS MODIFICATION...NAMELY THE LESSENING OF
STRONG PRESSURE GRADIENT/NW FLOW AS THE UPPER LEVEL RIDGE TAKES FULL
CONTROL...WILL SLOWLY ALLOW TEMPS TO RISE THROUGHOUT THE REMAINDER
OF THE EXTENDED FORECAST PERIOD. HOWEVER WE LIKELY WON/T SEE TEMPS
HIT ABOVE THE 80 DEGREE MARK AGAIN UNTIL AT LEAST NEXT WEEKEND.
MEANWHILE...WITH SUCH STRONG SUBSIDENCE IN CONTROL...THERE WILL BE
LITTLE CONCERN FOR CLOUDS...LET ALONE PRECIP CHANCES. ALL IN ALL IT
LOOKS TO BE A GORGEOUS AUTUMN-LIKE WEEK AHEAD.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 150 AM EDT SAT SEP 20 2014

ASIDE FROM VALLEY FOG DEVELOPING...AND THEN LIFTING AND DISSIPATING
THROUGH 13Z TO 14Z...VFR CONDITIONS WITH LIGHT WINDS WILL PREVAIL
DURING THE PERIOD. A COLD FRONT AND ASSOCIATED INCREASE IN CLOUDS IS
EXPECTED LATE IN THE PERIOD. THE FOG IS AGAIN EXPECTED TO FOLLOW ITS
TYPICAL LATE SUMMER/EARLY AUTUMN PATTERN OF DEVELOPING FIRST IN DEEP
VALLEYS AND THEN GROWING IN BREADTH AND DEPTH...WITH THE POTENTIAL TO
BEGIN TO REACH SOME RIDGES AND OPEN TERRAIN BY DAWN...SUCH AS MVFR AT
SJS IF WINDS SLACKEN AND POSSIBLY MVFR AT SME WHERE THE CURRENT
DEWPOINT DEPRESSION IS LOW BUT THERE ARE SCT CLOUDS AS WELL. THE
LARGER RECENT OBSERVED DEWPOINT DEPRESSION OF 7 AT LOZ POINTS TOWARD
ANY FOG THAT DEVELOPS BEING IN THE VFR RANGE.


&&

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

$$

UPDATE...JP
SHORT TERM...KAS
LONG TERM...JMW
AVIATION...JP






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