Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 261325
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
925 AM EDT SUN JUL 26 2015

.UPDATE...
ISSUED AT 925 AM EDT SUN JUL 26 2015

UPDATED TO LOWER SKY COVER TODAY WITH JUST A FEW HIGH CLOUDS
DRIFTING ACROSS THE AREA. GIVEN THE LACK OF INSTABILITY THIS
EVENING...HAVE OPTED TO REMOVE THUNDER CHANCES. LATEST HI RES
MODELS SHOW A DYING AREA OF SHOWERS MOVING IN WELL AFTER SUNSET
THIS EVENING. THIS SUPPORTS THE REMOVAL OF DAYTIME POPS AND
THUNDER. THIS WILL SET THE STAGE FOR ANOTHER MILD DAY WITH HIGHS
AGAIN PUSHING THE UPPER 80S IN PLACES.

UPDATE ISSUED AT 705 AM EDT SUN JUL 26 2015

CONDITIONS REMAIN CALM ACROSS THE CWA WITH HIGH PRESSURE OVERHEAD.
FOG IS OBSERVED ACROSS THE CWA...LOCALLY DENSE IN SOME LOCATIONS.
AS THE SUN BEGINS TO RISE OVER THE NEXT COUPLE OF HOURS...EXPECT
THE FOG TO BEGIN BURNING OFF. A BOUNDARY TO OUR NORTH HAS PRODUCED
SHOWERS AND CLOUD COVER OVER NORTH CENTRAL OH AND INDIANA EARLIER
IN THE OVERNIGHT PERIOD. NOW...MOST OF THESE SHOWERS HAVE
DISSIPATED...BUT THE CLOUD COVER IS CONTINUING TO SHIFT TO THE
SE. THESE CLOUDS WILL MOVE ACROSS THE CWA THROUGHOUT THE
DAY...INCREASING WITH DAYTIME HEATING...BUT SHOULD REMAIN VFR IN
NATURE. OVERALL...NO MAJOR CHANGES WERE NEEDED FOR THIS UPDATE.
LOADED THE LATEST OBSERVATIONAL DATA FOR TEMPS...DEW POINTS...AND
WINDS INTO THE ONGOING FORECAST TO MAKE SURE THE NEAR TERM GRIDS
REFLECTED THE CURRENT CONDITIONS.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 339 AM EDT SUN JUL 26 2015

HIGH PRESSURE REMAINS IN CONTROL DURING THIS EARLY MORNING...WITH
CALM CONDITIONS PROMOTING FOG ONCE MORE IN THE VALLEY LOCATIONS.
EXPECT THIS TO BURN OFF THROUGH THE MORNING AS THE SUN BEGINS TO
RISE. FOCUS THEN SHIFTS TO A WEAK BOUNDARY CURRENTLY NORTH OF THE
OHIO RIVER OVER NORTH CENTRAL INDIANA AND OHIO. LATEST GFS IS
SHOWING THIS BOUNDARY SINKING SLIGHTLY FARTHER SOUTH DURING THE DAY
TODAY...BUT REMAINING NORTH OF THE OHIO RIVER. THE QUESTION WITH
THIS BOUNDARY WILL BE PRECIPITATION CHANCES...PARTICULARLY IF THEY
WILL MAKE IT ACROSS THE OHIO RIVER AND INTO OUR CWA.
UNFORTUNATELY...EVERY MODEL HAS A DIFFERENT OPINION ON THIS...BUT
THE ONE THING THAT IS AGREED UPON IS THAT WHATEVER DOES OCCUR WILL
BE LIGHT AND BRIEF IN NATURE. ENDED UP JUST INCLUDING SLIGHT POPS
ACROSS THE NORTHERN CWA STARTING IN THE AFTERNOON AND CONTINUING
INTO THE EVENING. BY NIGHTFALL...THE BOUNDARY WILL SHIFT SOUTHWARD
INTO OUR CWA BUT WILL LOSE CONSIDERABLE STRENGTH AS IT DOES SO.
THIS...COUPLED WITH LOSS OF DAYTIME INSTABILITY...WILL KEEP ANY POPS
IN THE SLIGHT CHANCE CATEGORY THROUGH THE NIGHT...IF THEY EXIST AT
ALL.

WHAT IS LEFT OF THE BOUNDARY WILL STRETCH FROM WESTERN KY SE TO THE
SOUTHERN ATLANTIC SEABOARD DURING THE DAY TOMORROW...LEAVING MUCH OF
EASTERN KY UNDER HIGH PRESSURE BY THE AFTERNOON. DESPITE
THIS...HIGHER POPS THAN TODAY ARE EXPECTED ACROSS OUR AREA. THE
REASON FOR THIS LIES IN THE UPPER LEVELS...WHERE A SHORTWAVE WILL
BEGIN STRENGTHENING INTO AN UPPER LEVEL TROUGH OVER THE EASTERN
SEABOARD. ALL MODELS ARE SURPRISINGLY IN GOOD AGREEMENT THAT THIS
FEATURE WILL PULL ENOUGH MID AND UPPER LEVEL MOISTURE INTO THE
REGION THAT POPS WILL BE POSSIBLE SUNDAY NIGHT AND THROUGH THE DAY
MONDAY...ESPECIALLY ACROSS THE HIGHER APPALACHIAN TERRAIN. THIS WILL
INCLUDE SOUTHEAST KY AND POINTS TO OUR EAST. EITHER WAY...PWAT
VALUES ARE QUITE LOW...AND THERE IS LITTLE HELP FROM THE LLVL WINDS
AS FAR AS PRODUCING ANY DECENT SHEER OR LIFT...SO NOT EXPECTING
ANYTHING STRONG OUT OF THIS SYSTEM.

AS FAR AS TEMPERATURES DURING THE SHORT TERM...THE APPROACHING
BOUNDARY WILL BE TOO WEAK TO SWAY TEMPERATURES MUCH. CONTINUED
SUNSHINE TODAY WILL BOOST TEMPS BACK INTO THE UPPER 80S...AND THE
SLIGHT INFLUX IN MOISTURE WILL UNFORTUNATELY LEAD TO HIGHER HUMIDITY
VALUES. CLOUDS WILL LIKELY HELP INSULATE OVERNIGHT...WITH EARLY
MORNING LOWS EXPECTED TO STAY AROUND 70 DEGREES. THEN FOR
MONDAY...SCATTERED CLOUDS AND SHOWERS WILL LIKELY PLAY A ROLE IN
TEMPERATURES THROUGHOUT THE DAY...BUT OVERALL DON/T EXPECT THERE TO
BE ENOUGH IMPACT TO SUBSTANTIALLY LOWER TEMPS FROM WHAT THEY REACHED
TODAY.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 441 AM EDT SUN JUL 26 2015

EARLY IN THE PERIOD...UPPER LEVEL RIDGING WILL BUILD IN FROM THE
WEST...WHILE SURFACE HIGH PRESSURE RESIDES JUST TO OUR NORTHEAST.
THE NAM AND GFS HAVE BEEN CONSISTENT IN ALLOWING LOW LEVEL DRYING
TO NUDGE INTO OUR REGION IN ASSOCIATION WITH THE SURFACE HIGH...
RESULTING IN DRY WEATHER THROUGH WEDNESDAY. THE ECMWF MAINTAINS A
MORE HUMID AIR MASS AND GENERATES PRECIP IN OUR AREA UNDER THE
PERIPHERY OF THE UPPER RIDGE. HAVE OPTED TO LEAN CLOSER TO THE
AMERICAN MODELS...THINKING THAT THEY ARE BETTER HANDLING THE
SMALLER SCALE INTRUSION OF LOW LEVEL DRIER AIR...AND THAT RISING
GEOPOTENTIAL HEIGHTS WILL ALSO HELP TO INHIBIT DEEP CONVECTION.

ALL THREE MODELS SHOW THE UPPER RIDGE FLATTENING AND RETROGRADING
TO THE WEST AT MIDWEEK AS THE TROUGH CURRENTLY IN THE PACIFIC
NORTHWEST RIDES OVER THE RIDGE AND THROUGH SOUTHEAST CANADA AND
THE NORTHEAST CONUS. THIS WILL ALLOW ANOTHER COLD FRONT TO MOVE
SOUTHEAST THROUGH THE AREA WEDNESDAY NIGHT AND THURSDAY. EVEN THE
GFS SHOWS ENOUGH MOISTURE INCREASE TO ALLOW FOR A POTENTIAL OF
SHOWERS/THUNDERSTORMS WITH THE FRONT. THE MODELS HAVE TRENDED A
BIT FASTER WITH THE SYSTEM SINCE YESTERDAY...AND THIS HAS BEEN
TAKEN INTO ACCOUNT FOR THE POP.

BEHIND THE MIDWEEK FRONT...A DRIER AIR MASS IS SHOWN FOR LATE IN
THE WEEK...WHICH IF IT MATERIALIZES WILL ALLOW FOR SOME COOL
NIGHTS AND SUNNY/WARM DAYS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 715 AM EDT SUN JUL 26 2015

HIGH PRESSURE ACROSS THE REGION OVERNIGHT HAS LED TO CALM
CONDITIONS...ALONG WITH THE DEVELOPMENT OF FOG ACROSS MUCH OF THE
CWA. THIS FOG HAS AFFECTED THE TAF SITES TO VARYING DEGREES...BUT
SHOULD CONTINUE TO BURN OFF OVER THE NEXT HOUR OR TWO. FOR THE
REMAINDER OF TODAY...A WEAK FRONTAL BOUNDARY TO OUR NORTH WILL
SLOWLY SINK SOUTH TOWARDS THE OHIO RIVER. AS IT DOES...TAF SITES
MAY SEE AN INCREASE IN UPPER LEVEL CLOUDS...AND POSSIBLY MID
LEVEL CLOUDS DURING THE AFTERNOON. SOME PRECIP IS POSSIBLE OVER
FAR NORTHERN KY THIS AFTERNOON /CLOSEST TO KSYM/...HOWEVER THE
UNCERTAINTY OF THIS RAIN IS STILL HIGH ENOUGH THAT ANY MENTION WAS
LEFT OUT OF THE KSYM TAF. THE FRONTAL ZONE WILL CONTINUE TO
WEAKEN AS IT MOVES SOUTH THROUGH KY OVERNIGHT AND INTO TOMORROW
MORNING. QUESTIONS STILL REMAIN ABOUT HOW CLOUD COVER MAY AFFECT
FOG DEVELOPMENT. GIVEN THE AMOUNT OF MOISTURE IN THE
REGION...DON/T THINK IT WILL PREVENT FOG ALL TOGETHER...SO DID
MENTION SOME MVFR CONDITIONS AT SITES SUCH AS KLOZ AND KSME WHICH
WILL BE THE LAST TO EXPERIENCE THE AFFECTS OF THE FRONT. SOME
SLIGHT CHANCES OF SHOWERS AND THUNDERSTORMS ARE ALSO POSSIBLE
TOWARDS THE TAIL END OF THE FORECAST PERIOD...BUT GIVEN THE
UNCERTAINTY ON TIMING AND LOCATION THAT LATE IN THE
PERIOD...CONFIDENCE WAS NOT HIGH ENOUGH TO INCLUDE IN TAFS AT
THIS TIME.


&&

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

$$

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



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