Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 010705 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
305 AM EDT SAT AUG 1 2015

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 305 AM EDT SAT AUG 1 2015

06Z SFC ANALYSIS SHOWS THAT HIGH PRESSURE REMAINS IN CONTROL OF
EAST KENTUCKY/S WEATHER THIS EARLY MORNING. THIS HIGH HAS KEPT
CLOUD COVER TO A MINIMUM AND IS SUPPORTING A DECENT RIDGE TO
VALLEY TEMPERATURE SPLIT ON THE ORDER OF 5 TO 10 DEGREES. AT THE
SAME TIME DEWPOINTS ARE RUNNING IN THE LOWER 60S. AS TEMPERATURES
CONTINUE TO RADIATE LOWER FOR THE REST OF THE NIGHT THE DEWPOINTS
WILL ALSO CREEP DOWN...BUT IN THE DEEPER VALLEYS PROBABLY NOT FAST
ENOUGH TO PREVENT THE DEVELOPMENT OF FOG...ESPECIALLY NEAR RIVERS
AND BODIES OF WATER. WINDS WILL BE LIGHT THROUGH DAWN PERHAPS
CONTRIBUTING TO THE LOCALLY DENSE FOG IN THE MORE SHELTERED RIVER
VALLEY SPOTS.

THE MODELS ARE IN GOOD AGREEMENT ALOFT WITH THE LONGWAVE PATTERN
AS THEY ALL DEPICT A SLOWLY DEEPENING...LARGE TROUGH THROUGH THE
NORTHEAST PORTION OF THE CONTINENT STRETCHING SOUTH THROUGH THE
OHIO VALLEY OVER THE WEEKEND. THE NORTHWEST FLOW ASSOCIATED WITH
THIS WILL BRING MINOR SHORTWAVES OVER KENTUCKY DURING THE PERIOD
BUT NOT MUCH IN THE WAY OF MESOSCALE AMPLIFICATION UNTIL PERHAPS
SUNDAY AFTERNOON WHEN A HEALTHIER ONE PASSES BY TO THE NORTH. THE
NAM CONTINUES TO BE ON THE STRONGER SIDE OF THE MODEL SPECTRUM
WITH THE LARGER TROUGH AND THIS WAVE LATE IN THE PERIOD.
ACCORDINGLY...HAVE GONE WITH MORE OF A MODEL BLEND FAVORING A MIX
OF THE ECMWF AND GFS OUTSIDE OF THE NEAR TERM WHERE THE HRRR AND
NAM12 ARE REASONABLE.

SENSIBLE WEATHER WILL FEATURE A VERY PLEASANT MID SUMMER WEEKEND
AS THE AFTERNOON WARMTH IS KEPT COMFORTABLE BY RELATIVELY LOW
HUMIDITIES WROUGHT BY A MIDDAY AND AFTERNOON MIX DOWN OF DRIER
AIR FROM THE MID LEVELS. THIS WILL KEEP CLOUD COVER TO A MINIMUM
THROUGH THE PERIOD AND ALSO LEAD TO ANOTHER NIGHT OF GOOD
RADIATIONAL COOLING FOR SUNDAY MORNING. SIMILARLY...PATCHY FOG
WILL LIKELY BE LIMITED TO THE DEEPER RIVER VALLEY LOCATIONS BOTH
THIS MORNING AND SUNDAY MORNING...THOUGH LOCALLY DENSE POCKETS
WILL BE POSSIBLE AS WELL.

AGAIN USED THE SHORTBLEND MODEL AS A STARTING POINT FOR THE
T/TD/WIND GRIDS THROUGH THE DAY FOLLOWED BY THE SUPERBLEND INTO
SUNDAY. DID MAKE SOME SIGNIFICANT ADJUSTMENTS TO TEMPERATURES
THIS MORNING AND TONIGHT WITH RESPECT TO RIDGE AND VALLEY
DIFFERENCES ONCE...AND AS...THE INVERSION IS IN PLACE. AS FOR
POPS...KEPT THEM LOW AND IN LINE WITH THE DRIER MET GUIDANCE.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 344 PM EDT FRI JUL 31 2015

THE PERIOD IS EXPECTED TO BEGIN WITH A RIDGE EXTENDING FROM THE
SOUTHERN PLAINS INTO THE CENTRAL ROCKIES AND A TROUGH TROUGH OVER
MUCH OF THE EASTERN CONUS EXTENDING SOUTH FROM A CLOSED LOW OVER
THE SOUTHERN HUDSON BAY REGION. AT THAT POINT...A FEW SHORTWAVES
WILL BE MOVING INTO THE TROUGH ACROSS THE GREAT LAKES REGION. A
FEW SHORTWAVES WILL ALSO BE WORKING AROUND THE RIDGE ACROSS THE
WESTERN CONUS TO START THE PERIOD...WITH ANOTHER FURTHER NORTH
MOVING INTO SOUTHWESTERN CANADA. AT THE SFC...HIGH PRESSURE IS
EXPECTED TO BE CENTERED OVER THE CENTRAL APPALACHIANS AT THAT
POINT...WITH SFC LOW PRESSURE ALSO CENTERED OVER THE SOUTHERN
HUDSON BAY REGION AND A COLD FRONT EXTENDING SOUTH INTO THE
NORTHERN GREAT LAKES AND NORTHERN PLAINS...BEFORE BECOMING
STATIONARY AND EXTENDING NORTHWEST INTO THE NORTHERN ROCKIES.

THE CLOSED LOW INITIALLY NEAR SOUTHERN HUDSON BAY SHOULD MEANDER
SOUTH AND SOUTHEAST INTO ONTARIO AND QUEBEC AND OPEN UP A BIT
THROUGH THE EARLY TO MIDDLE PART OF NEXT WEEK. A SHORTWAVE OR TWO
ROTATING AROUND THIS LOW SHOULD WORK INTO THE NORTHERN GREAT LAKES
TO END THE WEEKEND AND ROTATE THROUGH THE GREAT LAKES AND INTO
THE NORTHEASTERN STATES THROUGH TUESDAY. THEN A SHORTWAVE WORKING
AROUND THE RIDGE SHOULD APPROACH THE MS RIVER VALLEY. THE MODELS
ARE NOT IN AGREEMENT WITH THE EVOLUTION AND TIMING OF THE
SHORTWAVE ENTERING SOUTHWEST CANADA EARLY IN THE PERIOD WORKING
INTO SOUTHWEST CANADA THE CORRESPONDING SFC AREA OF LOW PRESSURE
SHOULD TRACK INTO QUEBEC WITH THE TRAILING COLD FRONT GRADUALLY
DROPPING SOUTH OF THE GREAT LAKES DURING THE MONDAY INTO TUESDAY
PERIOD...BEFORE STALLING OUT AND BECOMING NEARLY STATIONARY NEAR
THE OHIO RIVER. THE SHORTWAVE MOVING INTO THE MS VALLEY AROUND
MIDWEEK SHOULD LEAD TO A SFC WAVE OR WAVES DEVELOPING ALONG THIS
BOUNDARY AND MOVING THROUGH THE OHIO VALLEY REGION. THE FRONTAL
ZONE ITSELF COULD ALSO PASS THROUGH THE AREA LATE IN THE PERIOD.
OVERALL...THE EXPECTED SFC AND UPPER AIR PATTERN WILL LEAVE THE
REGION SUSCEPTIBLE TO AT LEAST DIURNALLY DRIVEN CONVECTION AND
POSSIBLE MCS OR NOCTURNAL ACTIVITY. THE NORTHERN AND EASTERN PARTS
OF THE AREA MAY BE IMPACTED EARLY IN THE WEEK...POSSIBLY AS EARLY
AS THE START OF THE WORK WEEK.

AS FOR POPS...SUNDAY IS EXPECTED TO BRING A DRY END TO THE WEEKEND.
ISOLATED TO SCATTERED CONVECTION CANNOT BE RULED OUT AT ANY POINT
FROM MONDAY TO POSSIBLY AS LATE AS FRIDAY. THE TRACK AND TIMING OF
THE SHORTWAVE THAT ENTERS SW CANADA EARLY IN THE PERIOD WILL PLAY
A KEY ROLE IN THE DURATION OF THE THREAT FOR CONVECTION. WITH THE
MODELS RELATIVELY IN GOOD AGREEMENT THROUGH ABOUT THURSDAY WITH
THE SFC AND UPPER AIR PATTERN AND THE SHORTWAVE EXPECTED TO NEAR
AT MIDWEEK...CHANCES FOR CONVECTION APPEAR GREATEST FROM WED INTO
THU.

TEMPERATURES SHOULD MODERATE TO A FEW DEGREES ABOVE NORMAL DURING
THE MONDAY INTO WEDNESDAY PERIOD...BEFORE THE COLD FRONT GRADUALLY
SLIPS SOUTH.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 230 AM EDT SAT AUG 1 2015

HIGH PRESSURE WILL KEEP VFR CONDITIONS IN THE TAF FORECAST FOR
MOST OF THE SITES THROUGH THE PERIOD. THE EXCEPTION MAY BE AT SME
LATE THIS NIGHT AS THEIR DEWPOINT DEPRESSION IS CURRENTLY THE
SMALLEST. ACCORDINGLY...HAVE ADDED A PERIOD OF MVFR FOG TO THAT
SITE WHILE LEAVING THE REST CLEAN. OUTSIDE OF THE FORMAL TAF
SITES...PATCHY FOG WILL BE FOUND IN THE LOWER ELEVATIONS TOWARDS
DAWN...BECOMING LOCALLY DENSE FOR A BRIEF TIME. ANY FOG WILL
CLEAR OUT BY MID MORNING WITH VFR CONDITIONS CONTINUING INTO
SATURDAY NIGHT AT THE AIRPORTS. WINDS THROUGH THE PERIOD WILL BE
LIGHT AND VARIABLE.

&&

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

$$

SHORT TERM...GREIF
LONG TERM...JP
AVIATION...GREIF


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