Area Forecast Discussion
Issued by NWS Jackson, KY

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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 201419
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
1019 AM EDT SAT SEP 20 2014

.UPDATE...
ISSUED AT 1019 AM EDT SAT SEP 20 2014

BASED ON THE EXPANSION OF THE MID LEVEL AC HAVE OPTED TO GO AHEAD AND
EXPAND THE ISOLATED SHOWERS TO MOST OF EASTERN KENTUCKY. THE MID
LEVEL AC HAS A FEW VERTICAL TOWERS ALREADY SEEN FROM THE OFFICE. WITH
SOME WEAK INSTABILITY COMBINED WITH THE MID LEVEL INSTABILITY...WE
SHOULD SEE A FEW SHOWERS POP UP THIS AFTERNOON. EVERYTHING SHOULD
REMAIN FAIRLY ISOLATED AND THUNDER DOES NOT LOOK LIKE A THREAT AS
INSTABILITY IS NOT STRONG ENOUGH TO SUPPORT IT. OTHERWISE...NO OTHER
CHANGES PLANNED AT THIS TIME.

UPDATE ISSUED AT 740 AM EDT SAT SEP 20 2014

HOURLY GRIDS HAVE BEEN FRESHENED UP BASED ON RECENT OBSERVATIONS AND
SATELLITE TRENDS. THIS LED TO SOME MINOR ADJUSTMENTS TO HOURLY
TEMPS AND DEWPOINTS TO START THE PERIOD. ANY LINGERING VALLEY FOG
SHOULD BE LIFTING AND DISSIPATING SHORTLY...IF IT HAS NOT ALREADY
DONE SO. WX GRIDS WERE UPDATED ACCORDINGLY AND AN UPDATED ZFP AND HWO
WILL FOLLOW SHORTLY.

CONFIDENCE IN THE EVOLUTION AND PLACEMENT OF ANY SHOWERS
LATER TODAY REMAINS LOWER THAN AVERAGE. THE NAM HAS BEEN THE MOST
INSISTENT ON ISOLATED SHOWER CHANCES FOR TODAY WHILE THE RECENT HRRR
RUNS POINT TOWARD THE POTENTIAL FOR A STRAY SHOWER JUST ABOUT
ANYWHERE IN THE CWA THIS MORNING INTO THE AFTERNOON...BUT ALSO HAD
ACTIVITY EARLIER IN THE MODEL RUN...BETWEEN 8Z AND PRESENT WHICH DID
NOT MATERIALIZE. THE CURRENT FORECAST HAS THE SLIGHT CHANCES ACROSS
THE WEST OR NORTHWEST IN LINE WITH THE HIGHEST 3Z SREF POPS.

&&

.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 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 748 AM EDT SAT SEP 20 2014

ASIDE FROM ANY LINGERING VALLEY FOG LIFTING AND DISSIPATING THROUGH
13Z TO 14Z...VFR CONDITIONS WITH LIGHT WINDS WILL PREVAIL DURING THE
PERIOD. A COLD FRONT AND APPROACHING UPPER LEVEL SYSTEM WILL BRING
AN INCREASE IN CLOUDS LATER IN THE PERIOD...AND ISOLATED SHOWERS OR
PERHAPS A THUNDERSTORM COULD AFFECT AREAS NORTH OF A SME TO LOZ TO
JKL TO SJS LINE VERY LATE IN THE PERIOD. A FEW VALLEY LOCATIONS MAY
AGAIN EXPERIENCE FOG BETWEEN 3Z AND 12Z WITH VIS RESTRICTIONS DOWN TO
IFR OR MVFR...BUT THIS SHOULD NOT AFFECT THE TAF SITES.


&&

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

$$

UPDATE...KAS
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.