Area Forecast Discussion
Issued by NWS Jackson, KY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KJKL 200813
AFDJKL

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

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 355 AM EDT SAT SEP 20 2014

EARLY THIS MORNING...AN UPPER LEVEL RIDGE OF HIGH PRESSURE CENTERED
OVER THE SOUTHERN ROCKIES TO SOUTHERN PLAINS REGION WITH RIDGING EAST
INTO THE LOWER OH VALLEY WAS IN PLACE. ACROSS THE SOUTHEASTERN US...
A BROAD UPPER LEVEL LOW WAS PRESENT. MEANWHILE A SERIES OF SHORTWAVES
WERE IN THE NORTHERN STREAM WITH A WEAK LEAD SHORTWAVE NEAR THE MID
MS VALLEY REGION WITH ANOTHER SHORTWAVE NEARING THE NORTHERN GREAT
LAKES EXTENDING FROM WESTERN ONTARIO INTO THE UPPER MIDWEST AND DOWN
INTO THE CENTRAL PLAINS REGION. FURTHER NORTHWEST ANOTHER SHORTWAVE
IS MOVING ACROSS THE CANADIAN PLAINS.

THROUGH THE SHORT TERM PERIOD...THE LEAD WEAK SHORTWAVE WILL WORK
ACROSS THE AREA THROUGH EARLY TO MID AFTERNOON AS HEIGHTS BEGIN TO
FALL IN THE OH VALLEY REGION WHILE THE UPPER LEVEL RIDGE BUILDING
NORTH ACROSS THE ROCKIES AND INTO THE INTERIOR NORTHWESTERN US.
DOWNSTREAM ACROSS THE GREAT LAKES AND EASTERN US...A TROUGH OF LOW
PRESSURE WILL BEGIN TO BE CARVED OUT BY THE TWO MAIN SHORTWAVES AND
SOUTHEASTERN CONUS TROUGH BEGINNING TO MERGE INTO IT. THE ASSOCIATED
SFC LOW WILL TRACK WELL NORTH OF KY...BUT THE TRAILING COLD FRONT
WILL WORK INTO THE LOWER OH VALLEY REGION TONIGHT AND THEN MOVE
ACROSS THE COMMONWEALTH THROUGH THE END OF THE PERIOD...WHEN IT
SHOULD BE CLOSE TO EXITING INTO VA.

SCATTERED TO BROKEN CLOUDS IN THE 4 TO 7KFT RANGE HAVE DEVELOPED
OVERNIGHT IN THE WARM SECTOR. OUTSIDE OF THESE CLOUDS VALLEY FOG IS
LIKELY STILL PRESENT AND MAY BE DENSE AT LEAST IN SOME SPOTS ALONG THE
RIVERS AND LARGER STREAMS AND LAKES. DEWPOINT DEPRESSIONS ARE LARGER
NEARER TO THE VA BORDER WHERE A DOWNSLOPE FLOW HAS BEEN PRESENT WITH
SPEEDS OF 10 MPH OR MORE ACROSS THE HIGH TERRAIN AND OBSERVATIONS
SUPPORT ANY FOG BEING MUCH MORE LOCALIZED THERE. THIS FOG SHOULD
GRADUALLY BEGIN TO LIFT THROUGH SUNRISE AND THEN DISSIPATE BY A
COUPLE OF HOURS AFTER SUNRISE. IN ADDITION...WHERE CLOUDS FORM THIS
FOG WILL TEND TO DISSIPATE AS WELL.

THE MODEL GUIDANCE BRINGS THE WEAK MID LEVEL DISTURBANCE TOWARD THE
AREA FOR THE REMAINDER OF THE NIGHT AND INTO THE EARLY AFTERNOON.
THE 0Z NAM AND SOME OF THE NEAR TERM GUIDANCE SUCH AS THE HRRR ALSO
DEVELOP SOME CONVECTION THIS MORNING THROUGH EARLY AFTERNOON MAINLY
ACROSS THE WESTERN HALF OF THE CWA. MOS GUIDANCE ACROSS THESE
LOCATIONS DOES NOT HAVE A SLIGHT CHANCE POPS AND MODEL CONSENSUS
BLENDS GENERALLY STAYED BELOW SLIGHT AS WELL. HOWEVER...WE OPTED TO
GO WITH SLIGHT CHANCE IN THESE WESTERN LOCATIONS FOR TODAY...WHICH
WAS IN BETTER AGREEMENT WITH SURROUNDING WFOS.

THE MAIN PRECIPITATION CHANCE DURING THE SHORT TERM PERIOD AND THE
ENTIRE FORECAST PERIOD FOR THAT MATTER WILL COME AS THE TROUGH
BEGINS TO TAKE SHAPE LATE TONIGHT INTO THE DAY ON SUNDAY AND THE COLD
FRONT ENTERS EASTERN KY. THIS COLD FRONT AND THE APPROACHING TROUGH
IS EXPECTED TO BRING A BAND OF SCATTERED OR BETTER COVERAGE OF
CONVECTION AS IT WILL BE MOVING ACROSS EASTERN KY DURING THE DAYTIME.
ISOLATED TO SCATTERED CONVECTION MAY REACH THE NORTHERN PART OF THE
CWA TOWARD DAWN...BUT THE BEST CHANCE FOR CONVECTION WILL BE CLOSER
TO THE COLD FRONT GENERALLY DURING THE AFTERNOON HOURS. THUNDERSTORMS
WILL BE CAPABLE OF BRIEF HEAVY RAIN AND POSSIBLY SOME GUSTY
WINDS...PENDING THE DEGREE OF INSTABILITY.

.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.
&&

$$

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





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.