Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 072214 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 514 PM EST SUN FEB 7 2016 .SHORT TERM...
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(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.
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&& .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON) ISSUED AT 1236 PM EST SUN FEB 7 2016 VFR WILL LAST WELL INTO THE NIGHT. AFTER ABOUT 06Z...A RAIN/SNOW MIXTURE AND MVFR CONDITIONS AND WILL BEGIN TO MOVE IN FROM THE NORTHWEST...REACHING THE VA BORDER BY ABOUT 11Z. CONDITIONS WILL LIKELY FALL TO IFR FOR A TIME AS THE PRECIPITATION MOVES THROUGH. A BREAK IN THE PRECIPITATION IS LIKELY ON MONDAY MORNING...BUT RAIN AND SNOW SHOWERS SHOULD REDEVELOP FROM WEST TO EAST DURING THE LATE MORNING AND EARLY AFTERNOON. THERE COULD EVEN BE A FEW LIGHTNING STRIKES WITH THE SECOND ROUND OF PRECIP. && .JKL WATCHES/WARNINGS/ADVISORIES...
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WINTER WEATHER ADVISORY FROM 6 PM MONDAY 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 MONDAY TO 6 AM EST WEDNESDAY FOR KYZ088-118-120. WINTER WEATHER ADVISORY FROM 6 PM MONDAY TO 6 AM EST WEDNESDAY FOR KYZ104-106>110-112-113-115-117-119. WINTER WEATHER ADVISORY FROM 7 AM MONDAY TO 6 PM EST TUESDAY FOR KYZ087.
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&& $$ SHORT TERM...HAL LONG TERM...DJ AVIATION...HAL

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