Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 220234
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
1034 PM EDT MON APR 21 2014

.UPDATE...
ISSUED AT 1034 PM EDT MON APR 21 2014

SCATTERED SHOWERS CONTINUE TO SPECKLE WEST AND CENTRAL KY AS THEY
SLOWLY MOVE IN OUR DIRECTION. HOWEVER...AS OF NOW...THE LOW LEVEL
INVERSION HAS BEEN TOO MUCH TO OVERCOME FOR ANY THUNDER TO DEVELOP.
MADE A FEW CHANGES TO THE ONGOING FORECAST BASED ON CURRENT
CONDITIONS. FIRST...WITH THE LACK OF THUNDER ACROSS THE AREA WITH
THIS SYSTEM...AND BASED ON THE LATEST FORECAST SOUNDINGS...DECIDED TO
TAKE OUT ANY MENTION OF ISOLATED TSRA UNTIL LATE TONIGHT. AT THIS
POINT...ANY ONGOING SHOWERS COULD WORK TO COOL THE LLVLS...AND
ALLEVIATE THE LOW LEVEL INVERSION...MAKING IT EASIER FOR STORMS TO
DEVELOP. THE CLOSER PROXIMITY TO THE WEAK BOUNDARY THAT WILL BE
MOVING THROUGH LATE TONIGHT AND TOMORROW MORNING WILL ALSO HELP TO
SPARK ANY THUNDERSTORM DEVELOPMENT.

ALSO...SINCE PRECIP IS ONGOING...DECIDED TO CHANGE THE WEATHER GRIDS
FROM PROBABILITY TO COVERAGE...WITH SCATTERED SHOWERS EXPECTED TO
IMPACT EASTERN KY OVER THE NEXT FEW HOURS. OVERALL THE TIMING FOR
THE PRECIPITATION THROUGH TOMORROW STILL SEEMS TO BE WELL ON TRACK.
THOUGH WILL BE CURIOUS AS TO IF THIS SPOTTY SHOWER PATTERN WILL
ORGANIZE INTO A MORE WIDESPREAD EVENT...OR IF POPS WILL NEED TO BE
ADJUSTED DOWN LATER IN THE NIGHT. HOPEFULLY AS THE BOUNDARY NEARS AND
RH VALUES INCREASE...WE WILL SEE SOME INCREASE IN THE PRECIP
ACTIVITY AS WELL. LATEST MODEL GUIDANCE HAS THE BEST MOISTURE MOVING
INTO EASTERN KY BETWEEN 9 AND 12Z. REGARDLESS...BASED ON CURRENT
CONDITIONS...AND FORECASTED QPF...ULTIMATELY DECIDED TO TAKE OUT ANY
MENTION OF MODERATE RAINFALL. THOUGH THERE COULD BE A FEW HEAVIER
ISOLATED CELLS...OVERALL EXPECT THIS TO BE A SMALL AMOUNTING EVENT.
THIS MAY NEED TO BE LOOKED AT AGAIN DURING THE OVERNIGHT PACKAGE.

UPDATE ISSUED AT 736 PM EDT MON APR 21 2014

FORECAST SEEMS TO BE FAIRLY WELL ON TRACK SO FAR. WILL CONTINUE TO
MONITOR THE INCOMING FRONT AND RESULTING RAIN/TSRA CHANCES ACROSS THE
REGION AS IT GETS CLOSER...IN CASE ANY UPDATES NEED TO BE MADE AS A
RESULT. OTHERWISE...LOADED IN THE LATEST OBSERVATIONAL DATA FOR
TEMPS...WINDS...AND DEW POINTS...TO MAKE SURE ONGOING FORECAST LINED
UP WITH ONGOING CONDITIONS OVER THE NEXT FEW HOURS.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 353 PM EDT MON APR 21 2014

HIGH PRESSURE WILL CONTINUE TO SLIDE OFF TO THE EAST AS MID AND HIGH
LEVEL CLOUDS CONTINUE TO SHIFT TO THE EAST. WARM TEMPS HAVE REALLY
DRIED OUT SOME OF THE VALLEYS THIS AFTERNOON...ESPECIALLY IN THE EAST
WITH RH DROPPING INTO THE LOWER 20S AND UPPER TEENS. ALSO...WE HAVE
HAD A BIT MORE MIXING AS SOME ISOLATED RIDGE TOPS HAVE REACHED 15
MPH. GIVEN THE FACT THAT WE HAVE HAD OUR DEWS NOT RESPONDING WELL TO
THE SOUTHERLY FLOW AND THE MOS SEEMINGLY AGREEING WITH THE LOWER
DEWS...HAVE LOWERED THEM THROUGH THE SHORT TERM AND EVEN LOWERED THE
QPF EXPECTED FROM THE ONCOMING FRONT TONIGHT. THE BEST CHANCE OF
PRECIP WILL ARRIVE BY 06Z TONIGHT IN THE WESTERN LOCATIONS. THOUGH
THE ACTIVITY WILL ARRIVE OVERNIGHT...SOME INSTABILITY WILL BE PRESENT
FOR SOME THUNDER TONIGHT SO HAVE PUT A SLIGHT CHANCE OF THUNDERSTORMS
THROUGH TONIGHT AND INTO TUESDAY MORNING. A FEW ISOLATED LOCATIONS
MAY GET MORE THAN A COUPLE TENTHS OF RAINFALL BUT THE OVERALL DRY
PATTERN WILL LIMIT THIS.

THE AIRMASS BEHIND THIS SYSTEM WILL BE QUITE COOLER FOR THIS TIME OF
YEAR WITH THE TEMPS OVER THE BLUEGRASS DROPPING INTO THE 30S. THE DRY
CONDITIONS WILL STILL A FACTOR AS WELL WITH THE DEWS DROPPING INTO
THE 30S AS WELL. THE OVERALL FORECAST CHALLENGE WILL BE BASED UPON
THE IMPACT OF THE SHOWERS AND FEW THUNDERSTORMS ASSOCIATED WITH THE
PASSING FRONT AS THE SOAKING PROVIDED WILL FACTOR IN HOW LOW RH WILL
DROP INTO THE DAY ON WEDNESDAY. ALSO THIS WILL SET THE STAGE FOR SOME
PATCHY FROST BY WEDNESDAY MORNING IN THE DEEPER VALLEYS THROUGH THE
LOCATIONS WILL BE QUITE ISOLATED.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 420 PM EDT MON APR 21 2014

FORECAST MODELS ARE IN RATHER GOOD AGREEMENT BEFORE THE START OF
THE WEEKEND. TRANSIENT RIDGING WILL BUILD ACROSS OUR REGION THROUGH
THURSDAY BEFORE A LEAD SHORTWAVE TROUGH WILL APPROACH AND MOVE
ACROSS THE OH VALLEY LATE THU INTO THU NIGHT. AT THE SAME TIME...THE
MAIN TROUGH/UPPER LEVEL LOW WILL DROP ACROSS THE NORTHERN PLAINS AND
DAKOTAS AND THEN INTO THE GREAT LAKES ON THU NIGHT AND THEN INTO
EASTERN CANADA TO START THE WEEKEND. AT THE SFC...A SFC LOW SHOULD
TRACK FROM THE CENTRAL PLAINS TO THE WESTERN GREAT LAKES FROM WED
NIGHT THROUGH THU NIGHT. THIS LOW AND THE LEAD SHORTWAVE TROUGH WILL
SEND A COLD FRONT ACROSS THE AREA ON THU NIGHT INTO EARLY ON FRIDAY.
MODELS THEN HANDLE THIS TROUGH MOVING THROUGH EASTERN CANADA INTO
THE NORTHEASTERN US AND THE EVENTUAL PATTERN LATE IN THE PERIOD BOTH
IN TIMING AND AMPLIFICATION. THEREFORE...FROM THE WEEKEND INTO EARLY
NEXT WEEK...CONFIDENCE IN THE DETAILS IS BELOW AVERAGE.

SENSIBLE WEATHER WILL FEATURE DRY AND MILD CONDITIONS ON WEDNESDAY
AND THURSDAY. WE WILL LIKELY CONTINUE TO EXPERIENCE LOW RELATIVE
HUMIDITY VALUES EACH AFTERNOON...ESPECIALLY ON WED. THEN A STRUNG
OUT COLD FRONT IS THEN PROGGED TO PASS QUICKLY THROUGH OUR AREA LATE
THURSDAY NIGHT INTO FRIDAY MORNING. MODEL GENERATED QPF IS LEAN...AS
IS INSTABILITY...AND ONLY EXPECT SCATTERED TO NUMEROUS SHOWERS WITH
60 PERCENT POPS AND ONLY AN ISOLATED THUNDERSTORM OR TWO AS THE
FRONT PASSES. AS MENTIONED ABOVE...FORECAST MODELS THEN PAINT
DIFFERENT SCENARIOS OVER THE WEEKEND...ESPECIALLY WHEN LOOKING AT
TEMPERATURES AND PRECIPITATION CHANCES AS THE WEEKEND PROGRESSES
INTO EARLY NEXT WEEK. AT THIS POINT...THE CR DATA GRID LOAD BLENDING
MODEL DATA AND THE PREVIOUS FORECAST CONTINUED TO BE REASONABLE
UNTIL THERE IS MORE MODEL AGREEMENT IN THE PATTERN. THIS BLEND
RESULTS IN A DRY FORECAST FOR SATURDAY INTO SATURDAY NIGHT WITH A
RETURN TO CHANCES FOR SHOWERS SUNDAY INTO MONDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 734 PM EDT MON APR 21 2014

EXPECT VFR CONDITIONS TO PERSIST OVER EASTERN KENTUCKY THROUGH 03Z
TONIGHT. A COLD FRONT WILL APPROACH FROM THE WEST TONIGHT WITH
SOUTHWEST TO WEST WINDS EXPECTED. SHOWERS AND A FEW THUNDERSTORMS
WILL ALSO DROP CEILINGS ACROSS THE TAF SITES AROUND 10Z TOMORROW
MORNING. EXPECT REDUCED VISIBILITY AND LOWER CEILINGS INTO IFR RANGES
WITH THE SHOWERS FROM 10Z THROUGH THE EARLY AFTERNOON OVER EASTERN
KENTUCKY. OBVIOUSLY...THE INTENSITY OF THE STORM...AS WELL IS ITS
LOCATION IN PROXIMITY TO THE AIRPORT...WILL DRIVE THE PREVAILING
WIND...VIS...AND CIG CONDITIONS...SO UPDATES MAY NEED TO BE MADE AS
STORMS DEVELOP AND APPROACH ANY AIRPORTS. DRY AIR WILL THEN BEGIN TO
FILTER IN TOMORROW AFTERNOON...WITH SHOWERS COMING TO AN END AND CIGS
RISING TO VFR AGAIN FOR THE REMAINDER OF THE FORECAST PERIOD.


&&

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

$$

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





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