Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 211935
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
335 PM EDT MON JUL 21 2014

.UPDATE...
ISSUED AT 1035 AM EDT MON JUL 21 2014

HOURLY GRIDS HAVE BEEN UPDATED BASED ON RECENT OBSERVATION...SATELLITE
AND RADAR TRENDS. 12Z RAOBS FORM ILN...OHX...AND RNK ALL HAVE A RATHER
WARMER MID LEVEL TEMPS NEAR 600 MB. 12Z NAM AND ITS FORECAST
SOUNDINGS ARE SIGNIFICANTLY WARM AND MOIST THAT PARCELS AND THUS
CU MIGHT BE ABLE TO RISE PAST THIS WARM AIR FOR SOME ISOLATED
SHRA/TSRA. HOWEVER...THIS SCENARIO POINTS MORE TOWARDS A CONSIDERABLE
AMOUNT OF CU DEVELOPING 15Z TO 19Z...WHICH COULD EVENTUALLY JUST MIX
OUT BY EVENING.

THE 12Z NAM HAS THE ONLY VERY LIMITED CONVECTION DEVELOPING IN THE
HIGHEST TERRAIN. RECENT HRRR RUN AND RECENT RAP RUNS ALSO HAVE VERY
LIMITED COVERAGE OF CONVECTION LATER ON. THE 9Z SREF HAS THE HIGHEST
PROBABILITIES ACROSS THE VA BORDER COUNTIES. WITH THE CURRENT WARM
MID LEVEL AIR EXPECTED TO LARGELY PERSIST...CONVECTIVE COVERAGE MAY
END UP LOWER THAN THE CURRENT FORECAST OR POSSIBLY NIL OUTSIDE OF THE
TN AND VA BORDER COUNTIES FROM WHITLEY EAST AND NORTHEAST TO PIKE.
ATTM...WE WILL GO WITH PERSISTENCE FOR AFTERNOON POPS AND CONTINUE TO
EVALUATE CONVECTIVE TRENDS.

OVERALL...TODAY WILL CONTINUE THE WARMING TRENDS WITH RATHER HUMID
CONDITIONS.

UPDATE ISSUED AT 637 AM EDT MON JUL 21 2014

THE FEW SPRINKLES OVER THE AREA HAS DISSIPATED THIS MORNING SO HAVE
TAKEN THEM OUT AND ADJUSTED FOR THE CURRENT OBSERVATIONS. DENSE FOG
STILL APPEARS TO BE LINGERING IN SOME SPOTS SO WILL LEAVE IT IN THE
FORECAST THROUGH THE MID MORNING HOURS. HAVE LOADED THE LATEST OBS
AND UPDATED THE ZFP TO TAKE OUT SPRINKLES AND UPDATE THIS MORNINGS
LOWS.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 342 AM EDT MON JUL 21 2014

A VERY WARM...MOIST...AND UNSTABLE SHORT TERM PERIOD LOOKS TO BE THE
SCENARIO FOR EASTERN KENTUCKY. CONDITIONS ACROSS THE AREA AS OF 07Z
FEATURE SOME FOG DEVELOPMENT IN THE DEEPER VALLEYS. THIS IS MAINLY
WHERE SKIES HAVE CLEARED OUT FROM THE CLOUD COVER ASSOCIATED WITH
THE PREVIOUS EVENINGS CONVECTION. WHERE THIS HAS OCCURRED...MAY NEED
SOME HEADLINE ISSUED FOR THE DENSE FOG DEVELOPMENT. CLOUD COVER SHOULD
REMAIN PRETTY PERSISTENT INTO THE MORNING OVER THE EAST. LOWS ONLY
DROPPING INTO THE MID 60S THIS MORNING ALONG WITH MID 60 DEW POINTS
WILL MAKE FOR A RATHER UNCOMFORTABLE MORNING. EVEN NOW...WITH THIS
JUICY AIR MASS...A FEW WEAK SHOWERS ARE STILL DEVELOPING MAINLY OVER
THE EAST.

THE DEVELOPMENT OF THIS SCENARIO LIES WITH A PINCHED OFF UPPER LOW
THAT WILL BECOME CUT OFF FROM THE UPPER LEVEL FLOW OVER THE NORTHERN
CONUS. THE MODELS CONTINUE TO SHOW THIS FEATURE ENHANCING CONVECTION
ACROSS THE SOUTHEAST BUT ALSO INTO THE APPALACHIAN REGION. THIS ALONG
WITH THE UPPER LEVEL RIDGE OVER THE SOUTHEAST SLIDING EAST INTO THE
BAHAMAS ALLOWS FOR AN INCREASED SOUTHERLY RETURN FLOW INTO THE
SOUTHEASTERN CONUS AND INTO THE APPALACHIANS. THIS PATTERN CONTINUES
TO LEAVE EASTERN KENTUCKY UNDER VERY WEAK FLOW.

THAT SAID...LOOKING AT THE LOWER LEVELS...BOTH THE GFS AND NAM AGREE
WITH QUITE A BIT OF INSTABILITY AVAILABLE WITH CAPE VALUES REACHING
2500 J/KG BOTH THIS AFTERNOON AND TUESDAY AFTERNOON...THIS WITH PWATS
IN THE 1.50 TO 1.75 INCH RANGE BOTH DAYS AND WEAK FLOW WILL LEAD TO
SOME CONCERNS WITH SLOW MOVING STORMS PRODUCING HEAVY RAIN. THE ONE
SAVING GRACE HERE IS THE UPPER DISTURBANCE IS STILL CENTERED OVER THE
GULF COAST STATES BUT SOME ENERGY FROM THE LOW ON THE NORTHERN FRINGE
LOOKS TO MAKE IT INTO THE CENTRAL APPALACHIAN CHAIN AND INTO SOUTHEASTERN
KENTUCKY. THIS UNCERTAINTY WITH A GOOD TRIGGER HERE KEEPS FROM GOING
LIKELY POPS BUT STILL WILL KEEP SLIGHT CHANCE TO CHANCE FROM WEST TO
EAST AND GOING WITH AERIAL COVERAGE BOTH DAYS AS WITH THE TYPE OF
MOIST AND UNSTABLE AIR MASS IN PLACE...NOT MUCH SUPPORT IS NEEDED FOR
STORM DEVELOPMENT. MAY NEED TO MENTION SOME THREAT OF SLOW MOVING
STORMS IN THE HWO...MAINLY FOR TUESDAY WITH THE BETTER SUPPORT MAKING IT
INTO THE AREA.

.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 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 637 AM EDT MON JUL 21 2014

EXPECT THE LINGERING FOG TO LIFT BY 14 AND 15Z. A WEAK DISTURBANCE
OVERHEAD ALONG WITH SIGNIFICANT INSTABILITY WILL ALLOW FOR SHOWERS
AND THUNDERSTORMS TO DEVELOP AGAIN INTO THE AFTERNOON AND INTO THE
EVENING. COVERAGE AT THIS POINT APPEARS TO BE IN QUESTION AND SHOWING
SOME CONFIDENCE IN THUNDERSTORMS APPEARING AT THE TAF SITES IS NOT
POSSIBLE. WILL LEAVE THUNDERSTORMS OUT OF THE TAFS BUT MENTION THE
PRESENCE IN THE AFD. WINDS WILL BE LIGHT AND VARIABLE THROUGH THE
PERIOD. FOG WILL DEVELOP AGAIN TONIGHT AND WILL BE DENSE IN SOME
AREAS...ESPECIALLY AREAS THAT RECEIVE RAINFALL. WILL NEED TO PUT
BELOW IFR VISIBILITY VALUES IN THE TAFS.


&&

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

$$

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






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