Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 121916
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
316 PM EDT SAT JUL 12 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 315 PM EDT SAT JUL 12 2014

ISOLATED CONVECTION MAINLY TIED TO TERRAIN IS EXPECTED TO REMAIN TO
OUR SOUTH AND SOUTHEAST OVER SW VA AND THE HIGHER TERRAIN OF TN AND
NC FOR THE REMAINDER OF THIS AFTERNOON. THE AREA OF SHOWERS AND
THUNDERSTORMS OVER WESTERN INDIANA AND WESTERN KY IS AHEAD OF A NEARLY
STATIONARY WARM FRONTAL BOUNDARY THAT REPRESENTS THE LEADING EDGE OF
70 PLUS DEWPOINT TEMPERATURES OVER IL AND MO. SATELLITE...RADAR AND
LIGHTNING TRENDS ALL SHOW CONTINUING WEAKENING OF CONVECTION OVER
INDIANA...BUT THERE HAS BEEN SOME DEVELOPMENT INTO WESTERN KY. THE
SHORT RANGE RAP AND HRRR CONTINUE TO SHOW OVERALL DECAY OF CONVECTION
TO OUR WEST...AND ONLY IMPACT IN OUR AREA WILL BE SOME INCREASE IN
HIGH LEVEL CLOUDS.

WITH VERY DRY LOW LEVEL AIR IN PLACE IN EASTERN KY THIS
AFTERNOON...NOTE DEWPOINT AS LOW AS 48 AT QUICKSAND MESONET...THERE
WILL BE EVEN LESS FOG TONIGHT AS THERE WAS LAST NIGHT. GUIDANCE NOT
HANDLING THE DRY AIR VERY WELL...AND EXPECT THERE TO BE ABOUT A 5
DEGREE RIDGE VALLEY TEMPERATURE SPLIT FOR TONIGHT.

ON SUNDAY INSTABILITY WILL INCREASE AHEAD OF AN APPROACHING COLD
FRONT WITH MUCAPE IN EXCESS OF 4000 J/KG DEVELOPING IN A CORRIDOR
NORTH OF THE OH RIVER ACROSS SOUTHERN IN AND OH. BEST SHEAR WILL ALSO
BE NORTH OF THE OH RIVER SUNDAY AFTERNOON AND CURRENT THINKING IS
THAT THUNDERSTORMS WILL DEVELOP ACROSS OH AND INDIANA AND THEN
PROGRESS INTO NORTHERN PARTS OF THE FORECAST AREA LATE SUNDAY
AFTERNOON OR SUNDAY NIGHT. AT THE SAME TIME SOME ISOLATED TO
SCATTERED CONVECTION MAY DEVELOP OVER THE SOUTHEAST MOUNTAINS SUNDAY
AFTERNOON. THIS WOULD ALSO BE IN A CORRIDOR OF SLIGHTLY GREATER
INSTABILITY AND ALSO PARTIALLY TIED TO THE HIGHER TERRAIN. THE MODELS
HAVE BEEN CONSISTENT AT HINTING AT THIS POSSIBILITY IN THE SE
FORECAST AREA. CONSIDERING ALL THIS WILL BRING CHANCE PROBABILITY OF
SHOWERS AND THUNDERSTORMS TO THE SOUTHEAST AND NORTHERN PARTS OF THE
FORECAST AREA FIRST ON SUNDAY...WITH THE CENTRAL AND SOUTHWEST PARTS
OF THE FORECAST AREA THE LAST TO SEE THE RAIN CHANCES.

THE CONVECTION THAT DEVELOPS TO OUR NORTH ON SUNDAY HAS SEVERE
POTENTIAL...BUT AS IT MOVES INTO OUR AREA SUNDAY NIGHT AWAY FROM
BEST SUPPORT...THE SEVERE THREAT WILL DECREASE. THE DAY 2 SEVERE
WEATHER OUTLOOK WITH ONLY OUR FAR NW COUNTIES HAVING A SLIGHT RISK OF
SEVERE WEATHER THROUGH 12Z MONDAY CONTINUES TO LOOK GOOD. WITH PW
INCREASING THROUGH SUNDAY NIGHT TO 1.7 TO POSSIBLY GREATER THAN 2
INCHES SOME HEAVY RAINERS ARE DEFINITELY A POSSIBILITY SUNDAY NIGHT. MUCH
OF THE AREA HAS BEEN PLACED IN THE DAY 2 EXCESSIVE RAINFALL OUTLOOK
VALID 00Z MONDAY TO 00Z TUESDAY. FLASH FLOOD GUIDANCE IS FAIRLY HIGH
HOWEVER...AND PART OF THE AREA IS CURRENTLY IN D1 DROUGHT. INITIALLY...
AT LEAST FOR SUNDAY NIGHT...WHICH IS THE FIRST HALF OF THIS OUTLOOK
PERIOD THE FLASH FLOOD THREAT LOOKS BE ISOLATED AT WORST.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 315 PM EDT SAT JUL 12 2014

THE GFS IS SHOWING SOME DECENT CONTINUITY THROUGH THE LAST FEW
CYCLES BUT STILL APPEARS OUTSIDE THE RANGE OF OTHER SOLUTIONS AND
TOO PROGRESSIVE...ESPECIALLY CONSIDERING THE EXPECTED AMPLITUDE OF
THE MID AND UPPER LEVEL PATTERNS. THE ECMWF...WHICH HAS BEEN MORE
CONSISTENT IS ADVERTISING A SLOWER SYSTEM THAT PUNCHES FURTHER SOUTH
THAN OTHER MODELS AND IS ON THE SLOWER SIDE OF THE ENVELOPE OF
SOLUTIONS THROUGH THE MID TERM. JUST THE SAME MODELS ROUGHLY AGREE
ON THE OVERALL SCENARIO OF THE LARGE SCALE PATTERN. THE MAIN...AND
MOST SIGNIFICANT DIFFERENCES CROP UP RESOLVING SURFACE FEATURES AND
THE TIMING OF SFC SYSTEMS THROUGH OUR AREA. ATTM TENDENCY IS TO LEAN
TOWARDS THE ECMWF SOLUTION THROUGH THE MID RANGE AFTER USING A
CONSENSUS SOLUTION TO INITIALIZE THE EXTENDED PORTION OF THE
FORECAST PACKAGE. WILL STICK TO A BLENDED APPROACH FOR THE END OF
THE FORECAST WINDOW AS ADDITIONAL ENERGY EMERGES FROM THE PACIFIC
NW/CANADA CAUSING THE PATTERN TO BECOME LESS AMPLIFIED...BUT ALSO
ALLOWING FOR THE MEAN STORM TRACK TO RETURN NORTHWARD CLOSER TO OUR
NECK OF THE WOODS.

HEIGHTS FALL DROP STEADILY THROUGH THE FIRST HALF OF THE PERIOD AS A
SPLITTING UPPER LEVEL LOW DROPS A SIGNIFICANT PORTION OF ITS ENERGY
INTO THE THE UPPER MIDWEST AND GREAT LAKES...RESULTING IN A LARGE
DEEP TROUGH ACROSS THE ENTIRE EASTERN CONUS BY MID WEEK. SURFACE
FRONTAL ZONE WILL DROP SOUTHWARD ALONG THE OHIO RIVER BY LATE SUNDAY
OR SUNDAY NIGHT. A SECOND STRONGER...FASTER FRONTAL BOUNDARY WILL
FOLLOW QUICKLY BEHIND THE FIRST SLIDING THROUGH OUR AREA AS SOON AS
MONDAY NIGHT...OR AS LATE AS TUESDAY AFTERNOON DEPENDING ON WHICH
MODEL YOU LOOK AT. IT STILL SEEMS LIKE THE GFS IS HAVING TROUBLE
RESOLVING THE TIMING OR PASSAGE OF THESE TWO FRONTAL BOUNDARIES...
WITH A TENDENCY TO MERGE EACH DISTINCT BOUNDARY INTO A SINGLE FINAL
SYSTEM THAT MOVES THROUGH EASTERN KENTUCKY TOO QUICKLY.

WE ARE STILL LOOKING AT THE POTENTIAL FOR SOME SEVERE WEATHER THOUGH
THE TIME OF DAY AND EXACT AMOUNT OF SUNLIGHT WILL BE SOMETHING THAT
WILL NEED TO BE FACTORED IN. AS IS TYPICAL...THE NAM IS CONSIDERABLY
MORE UNSTABLE IN THE BOUNDARY LAYER BECAUSE OF ITS WET BIAS. THE NAM
IS ALSO SHOWING HIGHER BULK SHEAR VALUES THROUGH THE EARLY MONDAY
MORNING TO MONDAY AFTERNOON TIME FRAME. PWATS AND LIFT THROUGH THE
COLUMN ARE MUCH MORE IMPRESSIVE AS WELL WHEN COMPARED TO THE GFS.
EXPECT THE TRUTH WILL LIE SOMEWHERE IN THE MIDDLE THOUGH THAT MAY BE
A BAD ASSUMPTION GIVEN THE GFS MIGHT BE HAVING TROUBLE
DISTINGUISHING SURFACE AND BOUNDARY LAYER DETAILS. FREEZING LEVELS
REMAIN HIGH. SO WHILE SOME HEAVY RAIN CAN NOT BE RULED OUT...STORM
MOTION IS HIGH ENOUGH THAT HYDRO PROBLEMS SHOULD NOT BECOME TOO MUCH
OF A PROBLEM...AT LEAST BASED ON CURRENT GUIDANCE. BIGGEST THREAT
FOR SEVERE WEATHER WILL GENERALLY LIE ACROSS OUR BLUE GRASS COUNTIES
SUNDAY...BUT THEN EXPAND SOUTHEASTWARD TO ENCOMPASS OUR ENTIRE
FORECAST AREA BY MONDAY.

WE ARE STILL LOOKING AT UNSEASONABLE COLD WEATHER FOR THE PEAK OF
SUMMER HEATING THROUGH THE MIDDLE OF UPCOMING WEEK. ECMWF H850 TEMPS
DROP TO AROUND 8C AND THE GFS HAS TRENDED TOWARDS THE ECMWF. ECMWF
MOS GUIDANCE IS QUITE COOL WITH AFTERNOON HIGHS IN THE LOWER TO MID
70S AND LOWS SOLIDLY IN THE 50S FROM TUESDAY THROUGH FRIDAY. WHILE
THERE IS SOME MODERATION TOWARDS THE END OF THE WEEK...THERE IS A
GOOD POTENTIAL FOR SOME RECORD COLD MORNING LOWS AND EVEN A FEW
RECORD LOW MAXES. GFS MOS IS CONSIDERABLY WARMER BUT HAS SHOWN SIGNS
OF COOLING. PAST EXPERIENCE HAS TAUGHT THAT A BLEND OF GUIDANCE
MAKES A BEST FIRST GUESS...AFTER A TWEAK TOWARDS THE TYPICALLY MORE
ACCURATE ECMWF MOS.

ADDITIONAL ENERGY MOVING OUT OF THE NORTHWEST AND INTO THE BASE OF
THE BY THEN LIFTING EASTERN CONUS TROUGH WILL BRING A THREAT OF RAIN
BACK INTO THE FORECAST AREA AT THE END OF THE WEEK AND INTO THE
WEEKEND.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 116 PM EDT SAT JUL 12 2014

SCATTERED CUMULUS AROUND 5K TO 6K FEET WITH LIGHT WINDS CAN BE
EXPECTED THIS AFTERNOON AS HIGH PRESSURE CONTINUES TO CONTROL THE
LOCAL WEATHER. ISOLATED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
REMAIN JUST OUTSIDE OF THE FORECAST AREA THIS AFTERNOON IN THE HIGHER
TERRAIN OF SW VA...TN AND NC. THERE WAS LESS FOG THIS MORNING THAN
YESTERDAY MORNING AND EXPECT THAT TREND TO CONTINUE. AS SUCH WILL
LEAVE FOG OUT OF TAFS FOR THIS FORECAST. VFR CONDITIONS WILL PREVAIL
AGAIN ON SUNDAY...BUT SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE BY
SUNDAY NIGHT AHEAD OF A COLD FRONT DROPPING SOUTH ACROSS OH AND
INDIANA.

.JKL WATCHES/WARNINGS/ADVISORIES...


&&

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

$$

SHORT TERM...SBH
LONG TERM...RAY
AVIATION...SBH





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