Area Forecast Discussion
Issued by NWS Jackson, KY

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978 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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