Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 080710 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
210 AM EST MON FEB 8 2016

.UPDATE...
ISSUED AT 210 AM EST MON FEB 8 2016

MOST OF THE EASTERN VALLEYS ARE STARTING TO CLIMB SLIGHTLY FROM
THERE MIDNIGHT LOWS...ALTHOUGH A FEW SPOTS REMAIN IN THE UPPER
20S...AS THICKER CLOUD COVER HAS BEEN INTERMITTENT THUS FAR. THIS
SHOULD CHANGE THROUGH THE REST OF THE NIGHT...AS ECHOES ARE
FILLING IN OUT WEST...WITH SOME MEASURABLE PRECIPITATION STARTING.
HAVE USED A BLEND OF THE HRRR/RAP TO TIME POPS IN...WITH THE
HIGHER PROBABILITIES LIKELY BEING MORE CONFINED TO THE FAR WEST
THROUGH 12Z...AND THEN THE NORTHERN PORTION OF THE AREA...AS THE
BAND LIFTS OFF TO THE NORTHEAST AND DIMINISHES. THIS WILL BODE
BETTER FOR THE FAR EASTERN VALLEYS...WHERE MEASURABLE QPF LOOKS
LESS LIKELY WHILE TEMPERATURES ARE STILL NEAR OR BELOW FREEZING.
WILL BE KEEPING A SHARP EYE ON THE PRECIPITATION AND TEMPERATURE
TRENDS OVER THE NEXT FEW HOURS. UPDATES HAVE BEEN SENT.

UPDATE ISSUED AT 840 PM EST SUN FEB 7 2016

EASTERN VALLEYS HAVE ALREADY REACHED THE LOWER 30S AND STILL
LIKELY HAVE SOME TO FALL IN THE NEXT 2 TO 4 HOURS. WITH THIS IN
MIND...HAVE UPDATED THE FORECAST TO INCLUDE SOME FREEZING RAIN FOR
THE COLDER EASTERN VALLEYS THAT ARE A BIT MORE SHELTERED AND WON`T
LIKELY RECOVER IN TIME BEFORE PRECIPITATION SPREADS IN. STILL
LOOKING LIKE PRIMARILY RAIN AS WE KEEP A SHALLOW LAYER OF WARM AIR
JUST OFF THE VALLEY FLOORS. COULD STILL SEE SOME SNOW MIX IN ON
THE RIDGES...BUT SHOULD BE INCONSEQUENTIAL AS TEMPERATURES WILL
REMAIN ABOVE FREEZING AND LIMIT ANY ACCUMULATIONS.

UPDATE ISSUED AT 656 PM EST SUN FEB 7 2016

VALLEYS ARE DROPPING QUICKLY THIS EVENING WITH THE QUICKSAND
MESONET STATION ALREADY SITTING IN THE LOWER 40S. CLEARLY GUIDANCE
IS NOT CAPTURING THIS TEMPERATURE FALL THIS EVENING...SO HAVE
LOWERED TEMPERATURES INTO THE VALLEYS THROUGH THE REST OF THE
EVENING...GENERALLY DOWN TO 30 TO 32. WE MAY NEED TO GO FURTHER
YET...BUT THIS WILL BE DETERMINED BY HOW FAST CLOUDS CAN MOVE IN
LATER THIS EVENING. LATEST HI RES MODELS CONTINUING TO SHOW MOST
OF WHAT MOVES IN LATE TONIGHT BEING IN THE FORM OF RAIN. THE
QUESTION REMAINS HOW FAST VALLEYS COME BACK UP AND THUS IF WE CAN
AVOID A FREEZING RAIN IN A FEW OF OUR COLDER VALLEYS. HIGHER
TERRAIN IS STILL ON TRACK FOR SNOW...BUT INITIAL DRY AIR MAY CUT
INTO PRECIPITATION AMOUNTS LATE TONIGHT. THUS...PROBABLY LOOKING
FOR UNDER AN INCH IN THE HIGHER TERRAIN FROM ANYTHING THAT FALLS
LATE TONIGHT INTO TOMORROW MORNING. UPDATES HAVE BEEN SENT.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 514 PM EST SUN FEB 7 2016

A HIGHLY AMPLIFIED PATTERN IS DEVELOPING AS A STRONG UPPER TROUGH
DROPS SOUTHEAST OVER THE EASTERN CONUS. A VERY LARGE LOW PRESSURE
SYSTEM WILL MOVE SLOWLY SOUTHEAST OVER THE GREAT LAKES DURING THE
PERIOD. ITS ASSOCIATED COLD FRONT WILL PASS THROUGH THE JKL
FORECAST AREA MONDAY MORNING. MODELS AGREE ON PRECIP DEVELOPING
AND MOVING INTO THE AREA FROM THE NW LATE TONIGHT...AND
TEMPORARILY EXITING TO THE EAST ON MONDAY MORNING. LOW LEVEL TEMPS
ARE MARGINAL FOR RAIN VS SNOW...AND A MIX IS FORECAST FOR MOST
AREAS. HOWEVER...HIGHER ELEVATIONS NEAR THE VA BORDER WILL BE
BELOW FREEZING AND SEE ALL SNOW. WITH ACCUMULATIONS EXPECTED TO
START THERE ON MONDAY...HAVE ISSUED OUR WINTER WEATHER ADVISORIES
AT THIS POINT. THERE IS CONCERN THAT DECOUPLED VALLEYS WILL FALL
BELOW FREEZING AND NOT RECOVER BEFORE PRECIP BEGINS...AND THAT
WARMER AIR JUST ABOVE THE VALLEYS WILL RESULT IN FREEZING RAIN AT
THE SURFACE. THE PROBABILITY OF EVERYTHING COMING TOGETHER FOR
THIS IS FAIRLY LOW...AND DID NOT INCLUDE IT IN THE FORECAST AT
THIS TIME.

PRECIP SHOULD MOVE BACK IN FROM WEST TO EAST DURING THE DAY
MONDAY. FORECAST SOUNDING SHOW SIGNIFICANT COOLING ALOFT AS THIS
ROUND OF PRECIP DEVELOPS...WITH STEEP LAPSE RATES RESULTING IN A
DEEP LAYER. CONVECTIVE CURRENTS MAY EXTEND BEYOND THE -20C
LEVEL...AND A FEW LIGHTNING STRIKES CAN NOT BE RULED OUT.

TEMPERATURES WILL FALL BELOW FREEZING IN ALL AREAS MONDAY
EVENING. WITH SNOW SHOWERS CONTINUING AT TIMES...THE ADVISORY
EXPANDS TO COVER THE WHOLE FORECAST AREA AT THAT POINT.
ACCUMULATIONS IN ANY GIVEN PERIOD ARE NOT FORECAST TO BE ALL THAT
GREAT..BUT THE PROLONGED NATURE OF THE EVENT WILL EVENTUALLY LEAD
TO ADVISORY LEVEL SNOWFALL.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 514 PM EST SUN FEB 7 2016

MODELS REMAIN IN GOOD AGREEMENT...WITH DEEP AND BROAD CYCLONIC FLOW
SETTING UP ACROSS MUCH OF THE EASTERN CONUS FOR A GOOD PORTION OF
THE WEEK. THIS FLOW WILL AID IN BRINGING COLD AIR IN FROM TO NW DOWN
INTO THE TN AND OH VALLEYS THROUGH THE WEEK. NOW THIS BROAD CYCLONIC
FLOW MEANS THAT WE ARE LOOKING AT A PROLONGED PERIOD OF SNOW SHOWERS
WITH EMBEDDED ENHANCEMENTS FROM TIME TO TIME. THIS IN LIES BIGGEST
CHALLENGE THAT REMAINS THIS AFTERNOON FOR THE PERIOD WILL BE WHERE
AND WHEN DO THE PIECES OF ENERGY MOVE THROUGH THE FLOW. THESE WILL
PROVIDE ADDITIONAL ENHANCEMENTS TO THE SNOW SHOWERS THROUGH THE
START OF THE PERIOD. THAT SAID...THE SNOW SQUALL PARAMETER WOULD
SUGGEST SOME SQUALLS ARE POSSIBLE TUESDAY AFTERNOON...AND THIS SEEMS
REASONABLE BASED ON SOUNDINGS WITH LAPSE RATES ABOVE 6 C/KM IN BOTH
THE LOW AND MID LEVELS. THEREFORE WILL KEEP LIKELY POPS IN THE FOR A
GOOD PORTION OF TUESDAY. THESE SNOW SQUALLS COULD LEAD TO LOCALLY
HIGHER AMOUNTS OF SNOW DEPENDING ON WHERE THEY OCCUR AND IF THEY
REPEAT OVER THE SAME AREAS. EXPECT HIGHER SNOW RATIOS AND FLUFF
FACTOR FOR MUCH OF THE PERIOD...GIVEN THE COLD AIR IN PLACE THROUGH
THE ENTIRE COLUMN AND THE AT TIMES CONVECTIVE NATURE OF THE SNOW.

THE DEEPER THOUGH AXIS IS PROGGED TO FINALLY SWING EAST AS WE MOVE
INTO THURSDAY...AND WILL HELP CUTOFF THE BARRAGE OF SNOW SHOWERS
SEEN IN THE FIRST PART OF THE WEEK. THERE IS POTENTIAL FOR ANOTHER
WEAK DISTURBANCE BY FRIDAY...HOWEVER RIGHT NOW KEEPING MOST THE
PRECIP ACROSS THE SE PORTIONS OF THE CWA BASED ON THE MODEL BLEND
WITH FAIR AMOUNT OF UNCERTAINTY. MODELS CONTINUE TO STRUGGLE WITH
PHASING OF THE TROUGH THAT MOVES EAST WITH A CLOSED LOW UPPER LOW
DIVING SOUTH OUT OF CENTRAL CANADA. THE GFS IS MUCH MORE PROGRESSIVE
BUILDING A RIDGE INTO THE MIDDLE OF THE CENTRAL US...WHICH HAMPERS A
DEEPER TROUGH SETTING UP FURTHER SOUTH IN THE NE US.  THESE
DIFFERENCES WILL HAVE GREATEST IMPLICATIONS OF TEMPERATURES TOWARD
THE END OF THE FORECAST PERIOD. OVERALL WILL LEAN TOWARD THE COLDER
END SINCE GFS HAS CONTINUED TO TREND COLDER OVER THE PAST 4 RUNS
BASED ON THE 850MB TEMPS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 210 AM EST MON FEB 8 2016

AN APPROACHING COLD FRONT WILL BRING MAINLY RAIN TO THE AREA FROM
WEST TO EAST THROUGH DAWN. THE RAIN BAND WILL SHIFT OFF TO THE
NORTHEAST AND DISSIPATE THROUGH 15Z...BEFORE ADDITIONAL SHOWER
ACTIVITY DEVELOPS FOR THE AFTERNOON AS A POTENT UPPER LEVEL
DISTURBANCE ROTATES THROUGH THE REGION. CEILINGS AND/OR VISIBILITIES
WILL DROP DOWN TO MVFR WITHIN THE MORE SUSTAINED RAIN INITIALLY.
CEILINGS AND VISIBILITIES WILL LIKELY RAISE UP TOWARDS
15Z...BEFORE GRADUALLY DROPPING DOWN TO MVFR ONCE AGAIN IN THE
AFTERNOON. THERE MAY EVEN BE A RUMBLE OF THUNDER AT TIMES.
INCOMING COLDER AIR WILL THEN CHANGE ANY RAIN SHOWERS TO SNOW
SHOWERS TOWARDS DUSK...WITH MVFR TO IFR CONDITIONS AT TIMES
EXPECTED THROUGH THE END OF THE PERIOD.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM EST
TUESDAY FOR KYZ044-050>052-058>060-068-069-079-080-083>086-111-
114-116.

WINTER WEATHER ADVISORY FROM 7 AM THIS MORNING TO 6 AM EST
WEDNESDAY FOR KYZ088-118-120.

WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM EST
WEDNESDAY FOR KYZ104-106>110-112-113-115-117-119.

WINTER WEATHER ADVISORY FROM 7 AM THIS MORNING TO 6 PM EST
TUESDAY FOR KYZ087.

&&

$$

UPDATE...GEOGERIAN
SHORT TERM...HAL
LONG TERM...DJ
AVIATION...GEOGERIAN


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