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[Printable]
919
FXUS63 KJKL 180728
AFDJKL

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

.UPDATE...
ISSUED AT 145 AM EDT THU SEP 18 2014

SCT TO BKN MAINLY MID LEVEL CLOUDS ASSOCIATED WITH AN APPROACHING
DISTURBANCE CONTINUE TO WORK EAST ACROSS THE COMMONWEALTH. MODEL 700
MB MOISTURE PLAN VIEW DATA SUGGESTS THAT THIS WILL CONTINUE TO WORK
EAST ACROSS THE REGION DURING THE REMAINDER OF THE OVERNIGHT HOURS
AND INTO EARLY ON THURSDAY WITH HIGHER CHANCES FOR BROKEN OR
OVERCAST MID LEVEL CLOUDS ACROSS THE CENTRAL AND SOUTHERN PARTS OF
THE CWA AND MORE OF A CHANCES FOR SCATTERED MID CLOUDS OR SCATTERING
OUT TOWARD DAWN IN THE FAR NORTH. MEANWHILE...FOG HAS DEVELOPED
ESPECIALLY IN THE VALLEY LOCATIONS...BUT WITH MID CLOUDS WORKING IN...
IT EITHER SHOULD NOT BECOME DENSE OR IF IT DOES SO IT MAY BECOME LESS
DENSE TOWARD DAWN OR DURING PERIODS WHEN THE MID CLOUDS ARE WORKING
OVERHEAD. THERE REMAINS UNCERTAINTY WITH THE DETAILS OF THE FOG AND
ALSO THE HOURLY TEMPERATURE CURVE AS WELL. AT THIS POINT...HOURLY
GRIDS HAVE BEEN UPDATED BASED ON RECENT SAT AND OBSERVATION TRENDS
AND BLENDED INTO THE PREVIOUS FORECAST TOWARD DAWN.

UPDATE ISSUED AT 1025 PM EDT WED SEP 17 2014

FORECAST APPEARS ON TRACK THIS EVENING. MOISTURE ASSOCIATED WITH
WEAKENING DISTURBANCE IS TRACKING TOWARDS OUR AREA AS EXPECTED.
RESULT WILL BE SCT TO AT TIMES BKN SKY COVER...MAKING DETAILS OF
HOURLY TEMPERATURE FORECAST AND FOG DEVELOPMENT ALL THAT MORE
CHALLENGING THROUGH THE REMAINDER OF THE OVERNIGHT PERIOD. TWEAKED
AND BLENDED GRIDS TOWARDS HOURLY OBS AND TRENDS. ATTM...NO OTHER
CHANGES TO THE FORECAST PACKAGE ARE NECESSARY.

UPDATE ISSUED AT 835 PM EDT WED SEP 17 2014

A WEAK DISTURBANCE ALOFT IS MOVING SOUTHEAST OUT OF THE UPPER
MIDWEST. SOME LIGHT TO MODERATE SHOWER ACTIVITY OVER SOUTHERN IL/IN
IS DISSIPATING AS THE DISTURBANCE WEAKENS. HOWEVER...THIS FEATURE
WILL STILL BE STRONG ENOUGH TO BRING IN SOME ADDITIONAL MID LEVEL
CLOUDINESS TO OUR AREA FOR A PERIOD OF TIME OVERNIGHT. QUESTION IS
WILL CLOUD COVER BE WIDESPREAD ENOUGH TO MITIGATE FORMATION OF FOG.
TEMPERATURES ARE DROPPING AT A DECENT RATE AS OUR CU FILED
DISSIPATES. SFC DEW POINTS HAVE ALREADY REBOUNDED AS WELL. THOUGHTS
ARE WE WILL SEE SOME PATCHY FOG DEVELOPING THROUGH THE EVENING TIME
FRAME. BUT DENSITIES AND COVERAGE MAY BE LIMITED AS CLOUDS ROLL
THROUGH GENERALLY BETWEEN 05Z AND 10Z. APPEARS THERE MAY BE SOME
PARTIAL CLEARING AS WE APPROACH SUNRISE WHERE FOG COULD THICKEN UP
AND SPREAD FOR THOSE COUPLE OF HOURS AROUND DAWN. MUCH DEPENDS ON
EXACTLY HOW MUCH CLOUD COVER WE REALIZE. WITH DEW POINTS RECOVERING
SO QUICKLY AND TEMPERATURES DROPPING FASTER THAN EXPECTED...FELT IT
WOULD BE GOOD TO INTRODUCE THE DEVELOPMENT OF SOME PATCHY FOG THROUGH
THE EVENING HOURS...AND EARLY MORNING THURSDAY. THEREAFTER EXPANDED
FOG THROUGH THE PREDAWN HOURS. MAY SOME TWEAKS TO OVERNIGHT LOWS
BASED ON HOURLY TRENDS. THIS RESULTED IN A DROP OF A FEW DEGREES...
MAINLY IN OUR NORTH.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 335 PM EDT WED SEP 17 2014

18Z SFC ANALYSIS SHOWS WEAK HIGH PRESSURE IN PLACE OVER EAST
KENTUCKY WITH A WAVY FRONT TO THE SOUTH OF THE STATE. ALONG THE
WESTERN EXTENT OF THIS BOUNDARY...A WAVE HAS DEVELOPED AND IS
RUNNING SOUTHEAST OVER THIS FRONT COMING OUT OF SOUTHEAST MISSOURI.
LOCALLY THE CLOUDS ARE BREAKING UP THROUGH THE SOUTHWEST PORTIONS OF
THE CWA...WHILE HOLDING ON A BIT LONGER OVER THE NORTHEAST.
TEMPERATURES VARY MAINLY ACCORDING TO THE AMOUNT OF AFTERNOON
SUNSHINE...FROM THE MID 60S NORTHEAST TO THE LOWER 70S IN THE SOUTH.
DEW POINTS ARE GENERALLY IN THE LOW AND MID 50S THROUGH THE AREA WITH
LIGHT AND VARIABLE WINDS IN PLACE.

THE MODELS ARE IN GOOD AGREEMENT ALOFT AS THEY WEAKEN THE LARGE
NORTHEAST TROUGH THAT HAS BEEN IN PLACE FOR NEARLY A WEEK NOW. A
FEW WEAK SHORT WAVES WILL PASS THROUGH THE OHIO VALLEY DURING THIS
FILLING PROCESS. ANY MODEL DIFFERENCES THAT CROP UP WILL HAVE
RELEVANCE ONLY AFTER THE SHORT TERM PART OF THE FORECAST.
ACCORDINGLY...HAVE FOLLOWED A GENERAL MODEL BLEND AND FOCUSED ON THE
LOWER LEVEL MOISTURE OVER THE NEXT 36 TO 42 HOURS AS DEPICTED IN THE
HIGHER RESOLUTION NAM12 AND ALSO...INITIALLY...THE HRRR.

SENSIBLE WEATHER WILL FEATURE THE SFC REFLECTION...OF THE MID LEVEL
WAVE...PASSING JUST TO THE SOUTH OF THE AREA THIS EVENING WITH
MAINLY JUST AN INCREASE IN CLOUDS NOTED FOR EAST KENTUCKY. THESE
CLOUDS WILL CLEAR OUT...AS WELL...AFTER MIDNIGHT SETTING THE STAGE
FOR A NIGHT OF GOOD RADIATIONAL COOLING THAT SHOULD RESULT IN SOME
UPPER 40S IN THE NORTHERN VALLEYS BY DAWN ALONG WITH AREAS OF
FOG...LOCALLY DENSE TOWARD SUNRISE. IN THE WAKE OF THE SFC WAVE...
THURSDAY WILL SEE A RESURGENT HIGH BUILD INTO EAST KENTUCKY FROM THE
NORTH WHILE THE CLOUDS MOVE OFF TO THE SOUTH. ANY CAA WITH THIS WILL
BE COUNTERACTED BY THE AMPLE SUNSHINE TO YIELD COMFORTABLE
TEMPERATURES SIMILAR TO THOSE OF TODAY...ONCE THE FOG CLEARS.
ANOTHER GOOD NIGHT OF RADIATIONAL COOLING FOLLOWS THURSDAY NIGHT WITH
PATCHY VALLEY FOG...OR WORSE...ANTICIPATED BY DAWN WHILE TEMPS WILL
FLIRT WITH THE UPPER 40S AGAIN IN THOSE VALLEYS. BOTH TONIGHT AND
THURSDAY NIGHT...SLIGHTLY MILDER READINGS CAN BE EXPECTED ON THE
RIDGES.

THE CONSSHORT WAS USED AS A STARTING POINT FOR THE T/TD/WIND GRIDS
THROUGH THE FIRST 24 HOURS BEFORE THE SUPER BLEND WAS LOADED IN
THEREAFTER. DID AGAIN NUDGE THE LOWS TONIGHT...AND THURSDAY NIGHT...
FOR RIDGE AND VALLEY DIFFERENCES. AS FOR POPS...ENDED UP WITH SINGLE
DIGITS THROUGH THE FORECAST...IN-LINE WITH GUIDANCE.

.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.
&&

$$

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








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