Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 031350 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 850 AM EST TUE MAR 3 2015 .UPDATE... ISSUED AT 850 AM EST TUE MAR 3 2015 QUICK UPDATE TO BRING GRIDS IN LINE WITH HOURLY OBS AND RADAR TRENDS. HAD SOME SPRINKLES THIS MORNING BUT NOTHING SIGNIFICANT WITH RESPECT TO LIGHT FREEZING DZ...RA. TEMPS ARE RISING ABOVE FREEZING NOW. WILL LET CURRENT SPS FOR PATCHY FREEZING DRIZZLE ACROSS PORTIONS OF THE AREA EXPIRE AT 9 AM. ALSO FRESHENED UP THE ZONES. OTHERWISE...NO OTHER CHANGES TO THE FORECAST PACKAGE. && .SHORT TERM...(TODAY THROUGH WEDNESDAY) ISSUED AT 358 AM EST TUE MAR 3 2015 A COMPLICATED WEATHER PATTERN SHAPING UP FOR EASTERN KENTUCKY THROUGH THE MIDDLE OF THE WEEK. THE FIRST FORECAST CONCERN WILL BE THE POTENTIAL FOR FREEZING DRIZZLE OR FREEZING RAIN EARLY THIS MORNING NORTH OF THE MOUNTAIN PARKWAY. THERE IS A SMALL CHANCE THAT SOME LIGHT PRECIPITATION WILL FALL INTO A LAYER OF SUBFREEZING AIR THAT IS CURRENTLY IN PLACE ACROSS THE NORTHERN HALF OF THE FORECAST AREA. THE ISSUE WITH THIS WILL BE WHETHER OR NOT THE PRECIP IS ABLE TO REACH THE GROUND BEFORE TEMPERATURES RISE ABOVE FREEZING. THIS SITUATION WILL CONTINUE TO BE MONITORED CLOSELY OVER THE NEXT SEVERAL HOURS. IF SOME FREEZING PRECIP DOES DEVELOP...AN SPECIAL WEATHER STATEMENT WILL BE ISSUED TO DEAL WITH IT. THE SECOND CONCERN IN THE FIRST 36 HOURS OF THE FORECAST WILL BE HEAVY RAIN AND THE POTENTIAL FOR FLOODING ACROSS THE AREA. AT THIS TIME...THE FORECAST MODELS HAVE MOVED THE AXIS OF HEAVIEST PRECIPITATION TODAY SLIGHTLY NORTH OF WHERE IT WAS IN PREVIOUS RUNS. THE POP AND QPF FORECAST FOR TODAY WAS MODIFIED AS A RESULT TO ACCOUNT FOR THIS CHANGE. IT STILL APPEARS HIGHLY LIKELY THAT EASTERN KENTUCKY WILL EXPERIENCE A PERIOD OF MODERATE TO HEAVY RAIN BEGINNING LATE THIS AFTERNOON AND LASTING THROUGH THE END OF THE DAY ON WEDNESDAY. THERE MAY EVEN BE ENOUGH VERTICAL MOTION AND WIND ENERGY ALOFT TO FIRE OFF A FEW THUNDERSTORMS THIS AFTERNOON AND EARLY EVENING. AT THIS TIME...IT STILL APPEARS THAT 2 TO 3 INCHES OF RAIN WILL FALL ACROSS ALL OF EASTERN KENTUCKY. DUE TO RECENTLY MELTED SNOW...THE GROUND IS ALREADY COMPLETELY SATURATED ACROSS THE ENTIRE AREA...SO IT WILL NOT TAKE MUCH RAIN TO BEGIN CAUSING PROBLEMS. BASED ON CURRENT HYRDO FORECASTS...IT APPEARS THAT THE CUMBERLAND RIVER BASIN MAY EXPERIENCE THE MOST SIGNIFICANT FLOODING ISSUES. THERE WILL ALSO BE POINTS ALONG THE KENTUCKY BASIN THAT MAY SEE SIGNIFICANT FLOODING...SUCH AS AT RAVENNA. THE TEMPERATURES TODAY ARE STILL EXPECTED TO RISE ABOVE NORMAL ACROSS THE AREA...WITH HIGHS TOPPING OUT IN THE LOW TO MID 50S FOR THE ENTIRE AREA. A FEW LOCATIONS IN OUR FAR SOUTHWEST MAY EVEN APPROACH 60 IN THE STRONG SOUTHERLY FLOW THAT IS ON TAP FOR TODAY. THE END OF THE SHORT TERM PERIOD IS WHERE OUR SECOND AND PERHAPS MORE SERIOUS FORECAST CONCERN LIES. ONCE THE PREVIOUSLY MENTIONED COLD FRONT MOVES THROUGH THE AREA...VERY COLD AIR WILL FILTER INTO THE AREA BEHIND IT...AS WINDS SHIFT TO THE NORTH AND NORTHWEST. WITH A STRONG FEED OF GULF MOISTURE STILL ON TRACK TO OVERRIDE THE SLUGGISH COLD FRONT...SIGNIFICANT AMOUNTS OF PRECIPITATION ARE EXPECTED TO OCCUR. PRECIPITATION WILL GRADUALLY TRANSITION FROM RAIN TO A MIX OF RAIN...SLEET...AND SNOW ALONG AND NORTH OF THE I634 CORRIDOR WEDNESDAY AFTERNOON. THIS MIX OF PRECIPITATION IS FORECAST TO MOVE STEADILY EASTWARD ACROSS THE AREA BEHIND THE DEPARTING FRONT. AS MORE AND MORE COLD AIR MOVES IN...THE PRECIP WILL CHANGE OVER FROM A MESSY WINTRY MIX TO ALL SNOW BY AROUND 0Z THURSDAY. SOME LIGHT SNOW AND SLEET ACCUMULATIONS MAY OCCUR LATE WEDNESDAY IN OUR FAR NORTHWEST. THE CHALLENGE WITH THIS PART OF THE FORECAST WILL BE DETERMINING HOW STRONG THE WARM NOSE ALOFT WILL BE AT THE START OF THE EVENT. AT THIS TIME...THE NAM12 BY FAR HAS THE MOST WELL DEFINED LAYER OF WARM AIR AMONGST THE MODELS...WHICH WOULD LEAD TO MORE SLEET IN OUR NORTHER AND LESS SNOW. THE GFS AND ECMWF MODELS...ON THE OTHER HAND...ARE BOTH SHOWING A MUCH LESS WELL DEFINED WARM NOSE ALOFT AND THEREFORE MORE SNOW. FOR NOW HAVE DECIDED TO USE A BLEND OF THE TWO SOLUTIONS...GOING WITH A MIX OF SNOW AND SLEET TO START THE EVENT AND LEANING MORE TOWARD THE SNOWFALL AMOUNTS THE WWD FORECAST IS CURRENTLY PREDICTING. .LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY) ISSUED AT 557 AM EST TUE MAR 3 2015 APPEARS INCREASINGLY LIKELY THAT WE WILL BE DIVING HEADLONG INTO A TRANSITION FROM A HEAVY RAIN INTO A SIGNIFICANT WINTER WEATHER EVENT BY THE BEGINNING OF THE EXTENDED. GFS...ECMWF SOLUTIONS CONTINUE TO SHOW FAIRLY GOOD AGREEMENT WITH THIS SCENARIO. HOWEVER...THE NAM CONTINUES TO TREND FURTHER TO THE NORTHWEST WITH THE MOST SIGNIFICANT FEATURES IN OUR SENSIBLE WEATHER. WITH THE NAM OUTSIDE ITS WINDOW OF BEST PERFORMANCE...GENERAL PREFERRED TO REMAINED CLOSER TO THE OFFICIAL FORECAST AND A CONSENSUS OF THE GFS AND ECMWF. ENOUGH UNCERTAINTY REMAINS IN THE MODEL SOLUTIONS TO WARRANT STAYING WITH THE CURRENT SUITE OF WATCH PRODUCTS THROUGH THE FIRST PORTIONS OF THE EXTENDED. A VERY TIGHT BAROCLINIC ZONE STRETCHING WSW TO ENE ACROSS THE OHIO VALLEY WILL GRADUALLY SHIFT SOUTHEAST INTO TENNESSEE VALLEY THROUGH THURSDAY. WEATHER ALONG THE BAROCLINIC ZONE WILL REMAIN OF ACTIVE AS SEVERAL WAVES OF LOW PRESSURE TRACK THROUGH THE TN VALLEY REGION. COLDER ARCTIC AIR FILTERING INTO OUR AREA ON THE NORTHERN SIDE OF THIS ZONE WILL CHANGE RAIN OVER TO SNOW WEDNESDAY NIGHT. THERMAL PROFILES SUGGEST THAT THERE WILL BE A PERIOD OF MIXED PRECIPITATION DURING THE CHANGOVER...GENERALLY SLEET IN THE NORTH BUT SLEET OR POSSIBLY EVEN SOME FREEZING RAIN IN THE SOUTH. OVERALL MODEL TRENDS SEEM TO BE SLIGHTLY SLOWER WITH THE ONSLAUGHT OF COLD ARCTIC AIR INTO OUR FORECAST AREA LATE WEDNESDAY INTO WEDNESDAY NIGHT. BUT SIGNIFICANT SNOW/SLEET ACCUMULATIONS STILL APPEAR POSSIBLE...WITH THE HIGHEST AMOUNTS LIKELY NEAR THE I-64 CORRIDOR AND LESSER AMOUNTS ACROSS OUR SOUTHEAST. HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT BEGINNING LATE THURSDAY NIGHT AND REMAIN OVER THE AREA THROUGH LATE SUNDAY. TEMPS FRIDAY MORNING WILL LIKELY DIP INTO THE SINGLE DIGITS...WITH A FEW SPOTS IN OUR NORTH POSSIBLY DROPPING BELOW 0 DEGREES...WELL BELOW NORMAL FOR MARCH AND NEAR RECORD LOWS. THE COLD SNAP APPEARS TO BE FAIRLY SHORT LIVED AS TEMPERATURES START MODERATING BACK TOWARDS SEASONABLE LEVELS BY THE WEEKEND...THOUGH THEY WILL GENERALLY REMAIN BELOW NORMAL. SOME LIGHT PRECIPITATION WILL BE POSSIBLE EARLY NEXT WEEK AS A WEAK FRONTAL BOUNDARY DROPS SOUTHWARD OUT OF CANADA AND THE GREAT LAKES. BUT WEATHER WITH THIS FEATURE HAS BEEN TRENDING DRIER WITH TIME. FOR NOW MAINTAINED A SLIGHT POP SUNDAY NIGHT INTO MONDAY BUT FEEL THIS MAY BE OVERDONE. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT) ISSUED AT 358 AM EST TUE MAR 3 2015 VFR CONDITIONS WILL PREVAIL AT THE TAF SITES THROUGH AROUND 10Z. CLOUD BASES WILL CONTINUE TO GRADUALLY LOWER THROUGH THE REMAINDER OF THE OVERNIGHT AND PREDAWN HOURS AS A WARM FRONT APPROACHES FROM THE SOUTHWEST. CIGS AT 10 OR 11Z AT JKL...LOZ...AND SME SHOULD RANGE BETWEEN 2.5 AND 3K AS MULTIPLE LAYERS OF LOW LEVEL CLOUDS MOVE IN. CIGS WILL STEADILY LOWER THROUGHOUT THE MORNING...AND WE WILL LIKELY SEE IFR CIGS AT THE TAF SITES BY 14 TO 16Z THIS MORNING. PRECIPITATION IN THE FORM OF DRIZZLE OR LIGHT WILL BEGIN AFFECTING THE TAF SITES BY AROUND 9Z THIS MORNING. THERE IS A SMALL CHANCE FOR SOME FREEZING RAIN OR FREEZING DRIZZLE AT SJS AND SYM BETWEEN 9 AND 13Z AS PRECIP OVERRIDES A LAYER OF NEAR FREEZING AIR NORTH OF THE MOUNTAIN PARKWAY. THE PRECIP SHOULD CHANGE OVER TO ALL RAIN BY 14Z. CONDITIONS WILL WORSEN DURING THE TRANSITION...WITH IFR TO LIFR CONDITIONS THROUGH THE REMAINDER OF THE TAF PERIOD. THERE IS ALSO A CHANCE OF THUNDER THIS AFTERNOON AND EVENING...AS A STRONG COLD MOVING ACROSS THE AREA INTERACTS WITH WARM MOIST AIR OFF THE GULF OF MEXICO. && .JKL WATCHES/WARNINGS/ADVISORIES... FLOOD WATCH FROM 7 PM EST THIS EVENING THROUGH THURSDAY EVENING FOR KYZ044-050>052-058>060-068-069-079-080-083>088-104-106>120. WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY AFTERNOON FOR KYZ044-050>052-058>060-068-069-079-080-083>088-104- 106>120. && $$ UPDATE...RAY SHORT TERM...AR LONG TERM...RAY AVIATION...AR

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