Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 291512 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
1112 AM EDT MON JUN 29 2015

.UPDATE...
ISSUED AT 1112 AM EDT MON JUN 29 2015

THE FORECAST REMAINS ON TRACK TODAY. THE FIRST SHORT WAVE
TROUGH...WITH THE MAJORITY OF ITS ASSOCIATED FORCING NORTH OF THE
OHIO RIVER...IS ON ITS WAY OUT. WE NOW AWAIT THE NEXT WAVE TO
COME IN FROM THE NORTHWEST...WHICH COMBINED WITH HEATING AND SOME
SURFACE CONVERGENCE WILL ALLOW FOR ANOTHER ROUND OF SCATTERED
CONVECTION. AN ISOLATED SEVERE STORM IS STILL A POSSIBILITY...
DEPENDING ON HOW MUCH INSTABILITY CAN BUILD IN THIS AFTERNOON.
UPDATES HAVE BEEN SENT.

UPDATE ISSUED AT 745 AM EDT MON JUN 29 2015

FORECAST WAS NOT IN TOO BAD OF SHAPE. BROUGHT THE GRIDS IN LINE
WITH LATEST RADAR TRENDS AND HOURLY OBS. SOUTHERN END OF BAND OF
SHOWERS IS STRUGGLING TO HOLD TOGETHER...BUT THERE HAS BEEN SOME
REDEVELOPMENT OVER THE PAST HOUR. BASED ON RADAR MOSAIC...HIGHEST
POPS IN THE NORTH AND ESPECIALLY I-64 CORRIDOR LOOKS RIGHT ON
TARGET FOR THE START OF THE MORNING. WITH ADDITIONAL SHORTWAVE
ENERGY DROPPING INTO THE BASE OF OUR OVERHEAD TROUGH...STILL
EXPECTING REDEVELOPMENT OF SHOWERS AND THUNDERSTORMS LATER THIS
AFTERNOON...LINGERING INTO THE EARLY EVENING.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 417 AM EDT MON JUN 29 2015

HIGH AMPLITUDE PATTERN ALOFT WILL MEAN EASTERN CONUS TROUGH WILL
DOMINATE OUR WEATHER THROUGH THE SHORT TERM. BAND OF SHOWERS AND
THUNDERSTORMS ASSOCIATED WITH A SFC FRONTAL SYSTEM CONTINUES TO
MOVE EASTWARD ACROSS THE COMMONWEALTH THIS MORNING. MODELS...AND
ESPECIALLY THE HRRR SUGGEST THAT THIS ACTIVITY WILL GRADUALLY
WEAKEN AS IT MOVES INTO OUR AREA AROUND DAWN...DUE TO UPPER LEVEL
SUPPORT SHEARING OUT. HOWEVER...ADDITIONAL SHORTWAVE ENERGY ALOFT
ROUNDING THE BASE OF AN EASTERN CONUS TROUGH SHOULD HELP
REGENERATE ACTIVITY THROUGH THE AFTERNOON.

SHEAR AND INSTABILITY APPEAR SUFFICIENT FOR THE THREAT OF SOME
STRONG TO SEVERE THUNDERSTORMS...MAINLY THROUGH THE AFTERNOON AND
EARLY EVENING. BUT THERE ARE SOME LIMITING FACTORS FOR EXAMPLE...
CLOUD COVER...LESS THAN IMPRESSIVE MID LEVEL LAPSE RATES...AND
FORCING...THE STRONGEST OF WHICH MAY REMAIN FURTHER NORTH AND
WEST OF OUR AREA. THEREFORE SEVERE THREAT MAY BE MORE ISOLD IN
NATURE WITH RESPECT TO COVERAGE. JUST THE SAME WITH SPC PLACING
OUR AREA IN A SLIGHT RISK TODAY WILL CONTINUE TO ADVERTISE THE
POTENTIAL.

WITH THE APPROACH OF THE SFC TROUGH TO OUR WEST AND MID LEVEL
CLOUD COVER CURRENTLY MOVING INTO OUR AREA EXPECT TEMPERATURES TO
BEGIN TO REBOUND ACROSS MUCH OF THE AREA BETWEEN NOW AND SUNRISE.

.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 351 AM EDT MON JUN 29 2015

UPPER LEVEL MODELS CONTINUE TO SUPPORT A LONGWAVE TROUGH ACROSS MUCH
OF THE EASTERN CONUS TO START OFF THE PERIOD...KEEPING THE OHIO
RIVER VALLEY IN NW FLOW REGIME FROM TUESDAY NIGHT THROUGH FRIDAY.
THE AXIS OF THE TROUGH WILL THEN SHIFT DIRECTLY OVER KY AS ANOTHER
SHORTWAVE DIGS SOUTHWARD FROM CANADA TO START OFF THE WEEKEND.
FINALLY...THE UPPER LEVEL LONGWAVE PATTERN WILL SLOWLY DAMPEN AS WE
HEAD INTO THE END OF THE EXTENDED PERIOD SUNDAY INTO MONDAY.
HOWEVER...BY THE WEEKEND MODELS SHOW QUITE A BIT OF
DISCONTINUITY...SO THE EXACT TIMING AND MAGNITUDE OF THE UPPER LEVEL
TROUGH WILL BE SOMEWHAT LOW CONFIDENCE.

WITH THE GENERAL NW FLOW...EXPECT SHORTWAVES TO CONTINUE TO TRAVEL
SE AND INTO THE OHIO RIVER VALLEY. THIS WILL RESULT IN SEVERAL
SURFACE LOW PRESSURE CENTERS AND FRONTAL BOUNDARIES PASSING THROUGH
THE REGION...CREATING THE ENERGY AND LIFT TO PRODUCE SHOWERS AND
THUNDERSTORMS. AS HAS BEEN THE CASE OVER THE LAST FEW WEEKS...EXPECT
MOST WIDESPREAD ACTIVITY TO BE RIGHT ALONG AND JUST AHEAD OF THE
FRONTAL BOUNDARY...PEAKING IN SEVERITY DURING THE AFTERNOON AND
EARLY EVENING HOURS IN CONJUNCTION WITH THE PEAK HEATING.

THE FIRST OF THESE BOUNDARIES WILL BE EXITING TUESDAY NIGHT AS THE
NEXT BOUNDARY TO OUR NORTH MAKES A SHIFT SOUTHWARD. THIS SECOND
BOUNDARY IS EXPECTED TO MAKE IT INTO THE REGION WEDNESDAY
NIGHT...AND ACCORDING TO THE LATEST 00Z RUN OF THE GFS40...SHOULD
BECOME STALLED OUT ACROSS THE REGION THROUGH THE DAY FRIDAY AS THE
UPPER LEVEL TROUGH BACK-BUILDS ACROSS THE OHIO RIVER VALLEY. ALONG
THIS BOUNDARY...EXPECT SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS...WITH ANY UPPER LEVEL WAVES OF ENERGY ENHANCING
CHANCES FOR A MCS TO PASS THROUGH THE REGION. THE FRONTAL BOUNDARY
WILL FINALLY SHIFT SE OF THE STATE BY FRIDAY EVENING...ASSUMING
MODEL TIMING PANS OUT. UNFORTUNATELY...ANOTHER WEAK FRONTAL BOUNDARY
WILL HAVE FORMED TO OUR NORTH...AND WE WILL STILL BE IN VERY CLOSE
PROXIMITY TO THE EXITING FRONT. UNDER SW FLOW BY THIS POINT...AND
STILL IN AN UPPER LEVEL LOW PRESSURE TROUGHING PATTERN...EXPECT LESS
ORGANIZED SCATTERED CONVECTION TO CONTINUE INTO THE WEEKEND...WITH
BEST CHANCES STILL EXPECTED OVER THE SE CWA CLOSER TO THE EXITING
FRONT.

BY SUNDAY...MODEL CONFIDENCE IN CONVECTION STARTS TO DECLINE AS
THERE IS LITTLE AGREEMENT IN THE PATTERN ALOFT. IF THE GFS IS
CORRECT...THE UPPER LEVEL TROUGH WILL BEGIN DAMPENING/WEAKENING...
BUT CONTINUED WARM SW FLOW AND A PASSING SHORTWAVE COULD BE THE
SPARK FOR YET MORE SHOWERS AND THUNDERSTORMS DURING THE
AFTERNOON/EVENING HOURS. BOTH THE ECMWF AND THE GFS DO SUPPORT A
LARGE UPPER LEVEL CLOSED LOW PUSHING SOUTH FROM NW CANADA TO CENTRAL
CANADA BY LATE IN THE WEEKEND. THIS ENERGY WILL TRANSLATE TO THE
SURFACE WITH A STRONG LOW PRESSURE SYSTEM DEVELOPING ACROSS
SOUTHCENTRAL CANADA...PULLING A STRONG FRONTAL BOUNDARY WHICH WILL
SWEEP ACROSS MUCH OF THE CENTRAL AND EVENTUALLY EASTERN CONUS. EXACT
TIMING IS STILL OBVIOUSLY IN LOW CONFIDENCE...BUT IF THIS PANS OUT
ANOTHER GOOD CHANCE OF WIDESPREAD SHOWERS AND THUNDERSTORMS WILL
IMPACT THE REGION AHEAD OF THE FRONTAL ZONE AS WE END THE EXTENDED
PERIOD MONDAY.

WITH A NW FLOW REGIME...COOLER AIR WILL BE PULLED IN FROM CANADA TO
START OUT THE EXTENDED PERIOD. THEN AS THE TROUGH BACK-BUILDS AND
GENERALLY SW FLOW TAKES HOLD DURING A PORTION OF THE PERIOD...WE
WILL ACTUALLY CONTINUE TO PULL COOLER AIR IN FROM THE NORTH...AS
WINDS BECOME MORE NW JUST TO OUR WEST. THIS...IN CONJUNCTION WITH
CLOUD COVER AND POTENTIAL RAIN...WILL KEEP TEMPERATURES MODERATED
THROUGH MUCH OF THE EXTENDED...AT LEAST INTO THE WEEKEND. EXPECT
HIGHS IN THE UPPER 70S TO LOW 80S. BY MONDAY...ENERGY WILL BE
REDIRECTED TOWARDS THE INCOMING UPPER LEVEL HIGH...CAUSING A BREAK
IN THE UPPER LEVEL WIND FLOW ACROSS THE REGION. THIS WILL ALLOW FOR
A BETTER PULL OF TRUE SW WIND FLOW IN THE MID AND LOW LEVELS...WHICH
COMBINED WITH ANY SUNSHINE...WILL BOOST TEMPS BACK UP INTO THE MID
AND MAYBE EVEN UPPER 80S FOR THE DAY. WITH PARTLY TO MOSTLY CLOUDY
SKIES EXPECTED TO STICK AROUND DURING THE NIGHT...EXPECT
TEMPERATURES TO REMAIN MODERATED AS WELL...STAYING AROUND THE MID
AND UPPER 60S FOR EARLY MORNING LOWS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 745 AM EDT MON JUN 29 2015

IN GENERAL EXPECTING VFR CONDITIONS THROUGH THE BULK OF THE FORECAST
PERIOD. A BAND OF SCATTERED SHOWERS...WITH A FEW EMBEDDED
THUNDERSTORMS ASSOCIATED WITH AN APPROACHING COLD FRONTAL SYSTEM
WILL CONTINUE TO OVERSPREAD THE REGION FROM WEST TO EAST THIS
MORNING. SCATTERED THUNDERSTORMS ARE THEN EXPECTED TO REDEVELOP
DURING THE AFTERNOON...LINGERING INTO THE EARLY EVENING AS ANOTHER
DISTURBANCE PASSES THROUGH THE AREA. THE PRECIPITATION MAY BRING
TEMPORARY LOCALIZED IFR CONDITIONS...ESPECIALLY IN AFTERNOON
THUNDERSTORMS. SOME OF THE THUNDERSTORMS MAY CONTAIN MARGINALLY
LARGE HAIL AND STRONG WINDS. OTHERWISE...LIGHT SOUTHERLY WINDS
WILL GRADUALLY VEER TO THE SOUTHWEST AND INCREASE TO AROUND 10
KTS...WITH HIGHER GUSTS TO AROUND 20 KTS IN THE AFTERNOON.


&&

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

$$

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



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