Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 180816
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
416 AM EDT THU SEP 18 2014

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 400 AM EDT THU SEP 18 2014

A MID LEVEL DISTURBANCE CONTINUES TO NEAR THE LOWER OH VALLEY REGION
THIS MORNING. THIS DISTURBANCE HAS BROUGHT SOME MID LEVEL MOISTURE
AND BANDS OF MID LEVEL CLOUDS TO THE COMMONWEALTH. THESE BANDS OF
CLOUDS DO HAVE SOME THIN SPOTS AND HOLES IN THEM. THE MOST WIDESPREAD
MID LEVEL CLOUDS ARE NEAR THE INTERSTATE 75 CORRIDOR. IN FACT...SOME
WEAK RETURNS ARE WORKING ACROSS THE SW PART OF THE CWA NEARER TO THE
TN BORDER. NO MEASURABLE RAIN HAS BEEN OBSERVED SO FAR WITH THIS. IN
THE VERY NEAR TERM WE HAVE OPTED TO JUST INCLUDE SPRINKLES ACROSS THE
SOUTHERN COUNTIES FROM MCCREARY EAST INTO HARLAN COUNTY. THE ARRIVAL
OF THE MID LEVEL CLOUDS HAS AT LEAST TEMPORARILY LED TO IMPROVED VIS
IN THE FOG IN MOST AREAS PER RECENT OBSERVATIONS OTHER THAN KI35 AND
KPBX AND SOME OF THE BIG SANDY REGION WHERE THE FOG HAS BEEN LOCALLY
DENSE. THE MID CLOUDS MOVING OVERHEAD SHOULD LEAD TO IMPROVEMENTS
THERE AS WELL OTHER THAN IN BREAKS OR HOLES IN THE CLOUDS THROUGH
DAWN.

BEHIND THE MID LEVEL DISTURBANCE TO WORK ACROSS THE REGION THIS
MORNING...THE MID LEVEL MOISTURE NEAR 700 MB SHOULD ALSO DECREASE BUT
THE LAYER BETWEEN 850 MB AND 750 MB SHOULD STILL REMAIN RATHER MOIST.
SOME SHALLOW DIURNALLY DRIVEN CU WILL BE POSSIBLE IN THIS LAYER FROM
MID DAY INTO THE AFTERNOON...AS DRIER AIR IS EXPECTED TO MOVE IN...
ESPECIALLY ALOFT...BEHIND THE DISTURBANCE. 500 MB HEIGHTS ARE
EXPECTED TO RISE AS HIGH PRESSURE ALOFT BUILDS INTO THE LOWER OH
VALLEY FROM THE CENTRAL AND SOUTHERN PLAINS REGIONS. A SUBSIDENCE
INVERSION BETWEEN 800 MB AND 700 MB SHOULD RESULT AND IS EXPECTED TO
REMAIN THROUGH THE END OF THE SHORT TERM PERIOD.

AT THE SFC...A LARGE AREA OF HIGH PRESSURE CURRENTLY CENTERED OVER
ONTARIO WILL BUILD INTO THE OH VALLEY AND NORTHEASTERN STATES THROUGH
EARLY THIS EVENING. THE HIGH IS EXPECTED TO REACH THE NEW ENGLAND
COAST BY THE END OF THE PERIOD. FOG SHOULD DEVELOP TONIGHT...ESPECIALLY
IN VALLEY LOCATIONS UNDER LIGHT WINDS AND MOSTLY CLEAR TO CLEAR SKIES.

AN INVERTED SFC TROUGH IS EXPECTED TO DEVELOP NORTH INTO EASTERN KY
LATE TONIGHT AND INTO THE DAY ON FRIDAY. THE INVERTED TROUGH SHOULD
WEAKEN AND GRADUALLY SHIFT WEST BY THE END OF THE PERIOD. THIS
INVERTED TROUGH SHOULD DRAW ENOUGH MOISTURE WEST ACROSS THE
APPALACHIANS FOR SOME MOSTLY RATHER SHALLOW CU DEVELOPMENT BELOW THE
SUBSIDENCE INVERSION ON FRI FROM MIDDAY INTO THE EVENING. SOME OF
THIS COULD BECOME DEEP ENOUGH FOR A FEW SPRINKLES OR EVEN A STRAY
SHOWER OR TWO NEAR THE VA BORDER. FOR NOW...WE HAVE CONTINUED WITH A
DRY FORECAST AS MOS GUIDANCE GENERALLY HAS 10 PERCENT OR LOWER POPS.
HOWEVER...SEVERAL OF THE 0Z MODELS DO HAVE SOME LIGHT PRECIPITATION
NEAR THE VA BORDER ON FRI AFTERNOON. THE MODEL BLENDS ALSO HAVE SLIGHT
CHANCE POPS IN THAT AREA AS WELL FOR FRI...SO THIS SCENARIO WILL
NEED TO CONTINUE TO BE MONITORED.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 328 AM EDT THU SEP 18 2014

A SHORTWAVE AND INVERTED TROUGH OVER THE APPALACHIANS SHOULD BE
TRANSITIONING EASTWARD AND OUT OF THE REGION BY 0Z SATURDAY. MORE
ZONAL FLOW AND HIGH PRESSURE AT THE SURFACE WILL TAKE HOLD FOR THE
DAY SATURDAY. MEANWHILE...THE LONGWAVE PATTERN IS PLANNED TO DEEPEN
ACROSS SOUTH CENTRAL CANADA AND THE NORTH CENTRAL CONUS...EVENTUALLY
MAKING ITS WAY EASTWARD INTO THE OHIO RIVER VALLEY SUNDAY AND
MONDAY. THIS WILL RESULT IN A COLD FRONT TRAVERSING KY DURING THE
DAY SUNDAY. THE FRONT SHOULD EVENTUALLY PASS THROUGH THE JKL
FORECAST AREA...BUT MODELS ARE STILL NOT LOCKED IN ON SIMILAR
TIMING. A MODEL BLEND WOULD SUGGEST SUNDAY AFTERNOON/EVENING...AND
WILL CENTER THE HIGHEST POPS AT THAT TIME. AS WITH THE UNCERTAIN
START TIMES...THE EXIT OF THIS FRONT IS ALSO STILL SOMEWHAT
UNDETERMINED. WILL LEAN MORE TOWARDS A BLEND OF EXTENDED MODELS AT
THIS TIME UNTIL BETTER COHERENCY TAKES PLACE IN LATER MODEL RUNS.

SOUTHERLY WINDS JUST AHEAD OF THIS FRONTAL PASSAGE...AS WELL AS
INCOMING CLOUD COVER...WILL KEEP TEMPS A LITTLE ABOVE SEASONAL FOR
SATURDAY THROUGH SUNDAY NIGHT. KEPT WITH ONLY MENTIONING SLIGHT
CHANCE THUNDER FOR DURING THE DAY SUNDAY. JUST NOT PICKING UP ON A
LOT OF INSTABILITY ACROSS THE REGION...IN ADDITION TO THE FACT THAT
THE FRONTAL BOUNDARY SHOULD BE WEAKENING/SHEARING OUT AS IT REACHES
OUR AREA. 18Z SUNDAY SOUNDINGS SEEM TO SHOW THE BEST INSTABILITY
POTENTIAL /THOUGH STILL MARGINAL/...BUT WINDS ARE NEARLY
UNIDIRECTIONAL FROM THE WEST...SO DON/T EXPECT ANYTHING THAT
DEVELOPS TO STAY SUSTAINED FOR ANY LONG PERIOD OF TIME.

BEHIND THIS EXITING TROUGH WILL COME STRONG UPPER LEVEL RIDGING AND
SURFACE SUBSIDENCE. THIS WILL KEEP MUCH OF THE CENTRAL CONUS DRY
THROUGH THE REMAINDER OF THE EXTENDED /MONDAY FORWARD/. THE DEPTH OF
THIS RIDGE WILL ALSO WORK TO PULL STRONG NORTHERLY/CANADIAN AIR IN
THE LOW...MID...AND UPPER LEVELS ACROSS KENTUCKY. TEMPERATURES WILL
BE COLDEST ON TUESDAY...WHEN SOME OF THE BEST/STRONGEST NORTHERLY
AIR IS TAPPED INTO. BUT OVERALL...HIGHS SHOULD ONLY REACH THE UPPER
60S AND LOW 70S FOR THE REMAINDER OF THE EXTENDED. WITH STRONG
RADIATIONAL COOLING EXPECTED OVERNIGHT UNDER MOSTLY CLEAR
SKIES...EARLY MORNING LOWS WILL STAY IN THE UPPER 40S/LOW 50S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 155 AM EDT THU SEP 18 2014

A WEAK DISTURBANCE IS MOVING SOUTHEAST TOWARD THE LOWER OH VALLEY
REGION. THIS FEATURE IS BRINGING SOME MID LEVEL MOISTURE AND CLOUDS TO
THE COMMONWEALTH AND SOME OF IT IS WORKING INTO THE CWA ATTM. THIS
CLOUD COVER SHOULD GENERALLY TEND TO MODERATE OR LIMIT FOG DEVELOPMENT
OVERNIGHT. FOG HAS DEVELOPED...ESPECIALLY ACROSS THE SOUTHEAST PART
OF THE CWA NEAR SJS. PENDING ANY PARTIAL CLEARING THERE MAY BE MORE
COVERAGE CLOSE TO DAWN...BUT RECENT TRENDS POINT TOWARD THIS ACROSS
THE FAR NORTH AND THE NEXT COUPLE OF HOURS IN THE SOUTHEAST. UNCERTAINTY
REMAINS IN THE FOG OVERNIGHT...BUT GUIDANCE HAS GENERALLY TRENDED
TOWARD LESS FOG AT JKL AND LOZ. THIS TREND SHOULD ALSO HOLD FOR SME
AND SJS AS THE CLOUDS SHOULD RESTRICT OR LIMIT FOG DEVELOPMENT UNLESS
BREAKS OR PARTIAL CLEARING DEVELOPS. DENSITY AND COVERAGE OF FOG WILL
DEPEND ON EXACTLY HOW MUCH CLOUD COVER WE REALIZE. FOR THE TAF SITES
WE HAVE OPTED TO GO AS OPTIMISTIC...IF NOT A BIT MORE OPTIMISTIC THAN
MODEL GUIDANCE WOULD SUGGEST. THIS BROUGHT VIS DOWN TO NO WORSE THAN
IFR AT THE TAF SITES GENERALLY DURING THE 8Z TO 14Z PERIOD. WINDS
WILL BE LIGHT THROUGH THE PERIOD.


&&

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

$$

SHORT TERM...JP
LONG TERM...JMW
AVIATION...JP





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