Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 220039 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
839 PM EDT MON JUL 21 2014

.UPDATE...
ISSUED AT 838 PM EDT MON JUL 21 2014

THE FORECAST REMAINS ON TRACK. ISOLATED CONVECTION IS STILL DOTTING
THE AREA...ESPECIALLY ALONG THE SOUTHEAST TERRAIN. EXPECT A GRADUAL
WEAKENING TREND THROUGH MIDNIGHT. DID DIAL BACK THE POPS A BIT
FURTHER NORTH SOONER GIVEN THE TREND OF DIMINISHING CU.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 415 PM EDT MON JUL 21 2014

AN UPPER LEVEL RIDGE WAS CENTERED OVER THE SOUTHERN ROCKIES AND
SOUTHERN PLAINS REGION...WITH THE RIDGING EXTENDING TOWARD THE MID MS
AND LOWER OH VALLEY REGION. ANOTHER RIDGE WAS CENTERED OFF THE
SOUTHEASTERN U.S. COAST. AN UPPER LEVEL TROUGH/WEAK UPPER LEVEL LOW
WAS OVER THE SOUTHEASTERN STATES. MEANWHILE A TROUGH WAS DEPARTING
THE NORTHEASTERN U.S. A COUPLE OF SHORTWAVES ARE WORKING ALONG THE
US/CANADIAN BORDER/NORTHERN ROCKIES REGION WHILE ANOTHER SHORTWAVE IS
ROTATING AROUND AN UPPER LEVEL LOW OVER THE HUDSON BAY REGION. A WARM
AND RATHER MOIST AIR MASS IS IN PLACE ACROSS THE
REGION...HOWEVER...MID LEVEL DRY AIR AND LIMITED UPPER LEVEL SUPPORT
IS LIMITING COVERAGE THUS FAR.

THROUGH THE PERIOD...THE UPPER LEVEL LOW IS EXPECTED TO MEANDER TO
THE MS DELTA REGION. MEANWHILE THE UPPER LEVEL RIDGE WILL AMPLIFY
ACROSS THE ROCKIES AND INTO PARTS OF CANADA WHILE A TROUGH BEGINS TO
DEVELOP OVER THE EASTERN CANADA AND THE GREAT LAKES AS THE SHORTWAVES
MOVE TOWARD THE WESTERN GREAT LAKES AND MERGE WITH A SHORTWAVE
ROTATING FROM CENTRAL CANADA INTO EASTERN CANADA. AS THIS OCCURS...
A SFC LOW WILL TRACK FROM THE DAKOTAS TO NORTHERN QUEBEC. THE
TRAILING COLD FRONT WILL APPROACH THE OH VALLEY LATE IN THE PERIOD.

SOME OF THE NEAR TERM MODELS STILL INDICATE AT LEAST SOME ISOLATED
SHRA/TSRA COULD DEVELOP THROUGH THIS EVENING. THE CURRENT CU FIELD IS
NOT ALL THAT IMPRESSIVE AND COVERAGE MAY BE MORE LIMITED THAN THAT.
POPS WERE LOWERED FOR LATE THIS AFTERNOON/EVENING COMPARED TO THE
PREVIOUS FORECAST WITH 30 PERCENT ACROSS THE HIGH TERRAIN AND JUST
ISOLATED OVER THE REGION OF THE AREA. A WEAK DISTURBANCE ROTATING
AROUND THE SOUTHEAST UPPER LOW COULD LEAD TO THE THREAT OF CONVECTION
FOR A LITTLE WHILE AFTER 0Z NEAR THE VA BORDER. OTHERWISE...OVERNIGHT...
WITH A WEAK PRESSURE GRADIENT IN PLACE AND SKIES MOSTLY CLEAR TO
PARTLY CLOUDY ALONG WITH THE MID TO UPPER 60S DEWPOINTS EXPECTED...FOG
SHOULD AGAIN FORM. THE FOG MAY AGAIN BECOME DENSE IN THE RIVER VALLEY
LOCATIONS.

TUESDAY INTO TUESDAY NIGHT...THE RIDGE SHOULD EXTEND EAST INTO THE
OHIO VALLEY...BUT THE SOUTHERN OR SOUTHEASTERN COUNTIES WILL BE
CLOSER TO THE NORTHEASTERN EDGE OF THE SOUTHEASTERN U.S. UPPER LOW.
THERE SHOULD AGAIN BE CONSIDERABLE CU FORMATION ON TUE...BUT SOME MID
LEVEL WARM AIR MAY LINGER...AND AGAIN LIMIT CONVECTION. THE DIFFERENTIAL
HEATING OVER THE HIGH TERRAIN OR PERHAPS ON THE OUT EDGE OF SOME
OF THE CLOUD COVER OVER THE SOUTHEAST COULD BE A TRIGGER FOR
CONVECTION. IN ADDITION...A WEAK DISTURBANCE MAY ROTATE AROUND THE
UPPER LOW TOWARD THE APPALACHIANS. THE MODEL CONSENSUS IS FOR HIGHER
CHANCES AND BETTER COVERAGE FOR CONVECTION OVER THE SOUTH AND
SOUTHEAST. WINDS SHOULD AGAIN BE RATHER LIGHT ON TUE NIGHT AND WITH
A MOIST AIR MASS IN PLACE...PATCHY POSSIBLY DENSE RIVER VALLEY FOG
IS AGAIN ANTICIPATED.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 335 PM EDT MON JUL 21 2014

THE MID TERM WILL FOCUS AROUND A SURFACE COLD FRONT MOVING FROM NW
TO SE ACROSS THE REGION. WINDS FLOWING SOUTHERLY UP UNTIL THIS POINT
WILL BEGIN TO SWITCH TO A MORE WRLY DIRECTION JUST AHEAD OF THE
FRONTAL PASSAGE. STILL...MOIST AND UNSTABLE AIR ACROSS THE
REGION...AS WELL AS THE INCOMING LIFTING SOURCE WILL BE ENOUGH TO
PRODUCE WIDESPREAD SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE
REGION DURING THE DAYTIME HOURS WEDNESDAY. WITH CAPES WELL ABOVE
2000 J/KG AFTER 12Z...AND GOOD MID LEVEL DRY AIR...COULD BE A GOOD
SCENARIO FOR SOME DECENT CONVECTION. MODELS ARE ALL IN FAIRLY GOOD
AGREEMENT ABOUT THE ONSET OF PRECIP BETWEEN 15 AND 18Z IN THE
NORTHERN COUNTIES...WITH SOME DIURNAL SCATTERED CONVECTION POPPING
UP ACROSS EASTERN KY AFTER 12Z AHEAD OF THE MAIN LINE. AS THE FRONT
SLOWLY TRAVERSES KY...EXPECT PRECIP TO LINGER INTO THE OVERNIGHT
HOURS WEDNESDAY NIGHT AND INTO THE DAY THURSDAY. LOSS OF MID LEVEL
DRY AIR OVERNIGHT WEDNESDAY NIGHT WILL CUT DOWN ON SOME OF THE BEST
CONVECTION AND HAIL POTENTIAL...BUT EXPECT IT TO RETURN AGAIN BY
THURSDAY AND CONTINUE INTO THE OVERNIGHT HOURS THURSDAY NIGHT. BY
FRIDAY...THE FRONT WILL FINALLY EXIT TO OUR SE. THOUGH SOME UPSLOPE
CONVECTION MAY LINGER IN THE FAR SE...OVERALL DRIER AIR SHOULD
FILTER IN AND CUT OFF ANY REMAINING PRECIP CHANCES DURING THE DAY
FRIDAY.

TEMPS WEDNESDAY LEADING INTO THE FRONTAL PASSAGE WILL BE QUITE WARM
AND HUMID...WITH HIGHS TIPPING 90 DEGREES IN SOME LOCATIONS ACROSS
EASTERN KY. BY THURSDAY HOWEVER...COOLER AIR WILL BEGIN FILTERING IN
THANKS TO A SURFACE HIGH PRESSURE TO OUR NORTH...WITH HIGHS ONLY
EXPECTED TO REACH AROUND 80.

FOR THE REMAINDER OF THE EXTENDED...A STRONG RIDGE OVER THE SW
CONUS...AND A TROUGH OVER THE EASTERN CONUS WILL BE THE MAIN PLAYERS
IN OUR WEATHER. ALTHOUGH THE TROUGH WILL WORK TO BECOME LESS
AMPLIFIED BY LATE THE PERIOD...EXPECT SEVERAL SHORTWAVES TO RIDE
ALONG THE TROUGH AND BRING PRECIP CHANCES TO THE OHIO RIVER VALLEY
REGION. THE FIRST OF THESE WILL BRING SHOWERS AND THUNDERSTORMS TO
EASTERN KY BY SATURDAY AFTERNOON/NIGHT. CHANCES SHOULD THEN CONTINUE
THROUGH THE REMAINDER OF THE PERIOD. TEMPS WILL SLOWLY RISE BACK
INTO THE MID 80S WITH HIGHER HUMIDITY VALUES BY THE WEEKEND...THEN
WILL COOL SLIGHTLY AS ANOTHER COLD FRONT ACCOMPANIES THE PRECIP
CHANCES SUNDAY NIGHT/MONDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 838 PM EDT MON JUL 21 2014

ISOLATED CONVECTION WILL WIND DOWN ACROSS SOUTHEASTERN KENTUCKY
THROUGH 04Z. THIS ACTIVITY WILL STEER CLEAR OF THE TAF SITES. FOG
WILL BECOME A CONCERN OVERNIGHT...HOWEVER GIVEN THE SMALLER AMOUNT OF
CONVECTIVE COVERAGE AND HIGHER DEW POINT DEPRESSIONS HEADING INTO
NIGHTFALL...WILL KEEP MVFR CONDITIONS FOR ALL TAF SITES EXCEPT
SJS AFTER 04Z. LIFR OR WORSE FOG STILL LOOKS LIKE A GOOD POSSIBILITY
FOR THAT LOCATION...GIVEN THE LOW LEVEL WIND FETCH. ONCE THE FOG
BURNS OFF BY AROUND 13Z...SOME ISOLATED TO SCATTERED CONVECTION WILL
DEVELOP TUESDAY AFTERNOON...WARRANTING VCTS AT ALL SITES.

&&

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

&&

$$

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






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