Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 300211 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 1011 PM EDT WED OCT 29 2014 .UPDATE...
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ISSUED AT 1011 PM EDT WED OCT 29 2014 CURRENT TRENDS ACROSS THE REGION FEATURE THE CLOUD COVER UP NORTH SLOW TO MOVE SOUTH INTO THE AREA. HIGH PRESSURE CENTERED OVER THE CENTRAL PLAINS WITH A RIDGE AXIS NUDGING INTO THE TN VALLEY STILL SEEMS TO BE KEEPING SOME GRADIENT OVER THE AREA. AS SUCH THE CLOUD COVER HAS BEEN SLOW TO MOVE SOUTH DISSIPATING AS THIS OCCURS. THE WEAKENING GRADIENT STILL LOOKS TO OCCUR OVERNIGHT SO HAVE KEPT THE CLOUDS FROM MOVING SOUTH TO LATER IN THE NIGHT AND KEPT THE CLOUD COVER MAINLY IN THE NORTHEAST AND EAST. CONDITIONS THROUGH THE NIGHT STILL FAVOR SOME FROST AND FOG SO HAVE KEPT BOTH IN THE WEATHER GRIDS. HOWEVER...THIS FORECAST MAY CHANGE THROUGH THE NIGHT IF EXTENSIVE CLOUD COVER DOES MAKE IT FURTHER SOUTH THAN ANTICIPATED. WITH THIS...THE SLOW APPROACH OF THE CLOUD COVER HAS AFFECTED THE VALLEY TEMPS AND HAVE ADJUSTED THEM ACCORDINGLY AS SOME EXTREME VALLEYS HAVE DROPPED OFF EARLY TONIGHT. WITH THESE CHANGES TO TEMPS AND CLOUD COVER...HAVE SENT A NEW ZFP. UPDATE ISSUED AT 701 PM EDT WED OCT 29 2014 MAIN FORECAST CONCERN FOR TONIGHT WILL BE THE CLOUD COVER NORTH INTO OHIO AS IT SLOWLY PUSHES SOUTH. HOW MUCH CLOUD COVER THAT MOVES SOUTH INTO EASTERN KENTUCKY OVERNIGHT WILL DICTATE HOW MUCH FOG WE WILL GET AS WELL AS ANY FROST. ONCE THE LEADING EDGE OF THE MOISTURE BANKS AGAINST THE MOUNTAIN RANGES TO THE EAST...THIS CLOUD COVER WILL FILTER FURTHER SOUTH IN A LOW LEVEL STRATUS LAYER. FOR NOW...THE GOING FORECAST LOOKS ON TRACK AND WILL LEAVE THE CLOUD COVER AS IS BASED ON CURRENT TRENDS. IT IS WORTH MENTIONING THAT THE MODELS DO NOT HAVE THIS WIDE SPREAD CLOUD COVER IN THEIR SOLUTIONS...THOUGH HISTORICALLY...THE MODELS DO HAVE TROUBLE IDENTIFYING THIS SCENARIO. FOR NOW HAVE UPDATED THE GRIDS WITH THE NEWEST OBSERVATIONS AND A NEW ZFP WILL NOT BE NEEDED.
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&& .SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT) ISSUED AT 315 PM EDT WED OCT 29 2014 SHORT TERM IS BASICALLY A TRANSITION PERIOD LEADING UP TO THIS WEEKENDS MAJOR STORM SYSTEM. GENERAL WEST TO NORTHWEST STEERING FLOW WILL GUIDE SFC HIGH PRESSURE ACROSS OUR AREA OVERNIGHT. LOW PRESSURE AND ASSOCIATED STRONG COLD FRONTAL SYSTEM WILL APPROACH THE FORECAST AREA QUICKLY THURSDAY NIGHT INTO EARLY FRIDAY MORNING. FOR SENSIBLE WEATHER...SFC HIGH PRESSURE AND WEAK MID LEVEL SHORT WAVE RIDGING WILL KEEP OUR WEATHER DRY BUT WILL NOT BE STRONG ENOUGH TO PREVENT A TEMPORARY INCREASE IN CLOUD COVER OVERNIGHT AS A LARGE AREA OF SC ROTATES INTO THE OHIO VALLEY REGION. SKIES CLEAR BACK OUT THURSDAY TO PROVIDE OUR AREA WITH ONE MORE DAY OF SEASONABLE AUTUMN LIKE WEATHER BEFORE BIG CHANGES OCCUR. WE WILL SEE THE THREAT OF RAIN SHOWERS INCREASE TOWARDS DAWN ON FRIDAY...MAINLY FOR OUR WESTERN MOST COUNTIES. FOR TEMPS...WEST TO NORTHWEST FLOW WILL TEND TO KEEP OUR TEMPERATURES ON THE COOL SIDE OF NORMS. SAW NO REASON TO DEVIATE FROM BLENDED MODEL GUIDANCE. SO JUST NUDGED INHERITED TEMPS TOWARDS MODEL CONSENSUS. .LONG TERM...(FRIDAY THROUGH WEDNESDAY) ISSUED AT 400 PM EDT WED OCT 29 2014 PERIOD WILL START OFF WITH A STRONG CLOSED LOW MOVING SOUTH THROUGH CANADA...ACROSS THE UPPER GREAT LAKES...AND NOSE-DIVING INTO THE OHIO RIVER VALLEY REGION FRIDAY EVENING AND OVERNIGHT. THIS LOW IS CONTINUING TO SHOW A STRENGTHENING TREND OVER THE LAST FEW RUNS OF THE GFS...NAM...AND ECMWF. THIS WILL BE THE MAIN SYSTEM TO AFFECT THE WEATHER INTO THE WEEKEND...BUT SHOULD BE FAIRLY PROGRESSIVE. THE LOW WILL ROTATE EASTWARD THROUGH THE REGION ALONG A TROUGH AXIS...AND EXIT BY SATURDAY EVENING...WITH HEIGHTS EXPECTED TO RISE THROUGHOUT THE REST OF THE EXTENDED PERIOD. MODELS ARE ALL IN FAIRLY GOOD AGREEMENT WITH THIS SYSTEM...AND CONTINUE TO BE SO THROUGH THE REMAINDER OF THE EXTENDED AS WELL. THIS HAS LED TO HIGHER CONFIDENCE FOR THIS FORECAST. CONCERNING THE STRONG LOW MOVING INTO THE REGION...THIS COULD BRING DRASTIC CHANGES TO THE WEATHER PATTERN ACROSS EASTERN KY. LATEST FORECAST SOUNDINGS ARE STILL TRENDING COLDER...SHOWING A VERY STRONG JET STREAK OF NRLY CANADIAN WINDS BEING PULLED INTO THE REGION. THIS CAA SHOULD DROP TEMPS BELOW FREEZING ACCORDING TO BOTH THE NAM AND GFS BY 06 SATURDAY THROUGH MID MORNING SATURDAY. HIGHEST ELEVATIONS /I.E. BLACK MOUNTAIN...COULD LOWER BELOW FREEZING BY 3Z/. MEANWHILE...TIME HEIGHTS ARE ALSO SHOWING A GOOD AREA OF OMEGA AND LIFT AROUND THE SAME TIME PERIOD...INDICATIVE OF SOME GOOD SNOW POTENTIAL. ORIGINALLY...IT SEEMED AS THOUGH ANY ACCUMULATION WOULD BE CONFINED TO THE HIGHEST ELEVATIONS /WHERE THE BEST UPSLOPE LIFT AND COLDEST TEMPS WOULD OCCUR/. HOWEVER...BASED ON THE CURRENT TRENDS...TEMPS SHOULD DROP BELOW FREEZING ACROSS MUCH OF THE CWA...SO SOME SNOW ACCUMULATIONS ARE POSSIBLE EVEN IN THE WESTERN CWA. HIGHEST AMOUNTS ARE STILL EXPECTED IN THE UPSLOPE REGIONS. THE CLINCHER WILL BE THE CHANGE OVER. IT APPEARS AS THOUGH MODELS ARE IN FAIR AGREEMENT THAT THE PRECIP ASSOCIATED WITH THIS SYSTEM AND COLD FRONTAL PASSAGE WILL ENTER INTO THE REGION QUITE QUICKLY...AS EARLY AS 15Z FRIDAY. AT THIS POINT...TEMPS WILL STILL BE ABOVE FREEZING...WITH PRECIP EXPECTED TO FALL IN THE FORM OF RAIN. AS THE SYSTEM CONTINUES TO AFFECT EASTERN KY...AND TEMPS FALL OVERNIGHT...TEMPS WILL FALL TO BELOW FREEZING...AND INSTABILITY SHOWS SIGNS OF INCREASING. IN FACT...AS INSTABILITY HEIGHTENS FRIDAY EVENING...IT IS POSSIBLE TO HEAR A FEW RUMBLES OF THUNDER IN THE HEAVIEST SHOWERS JUST BEFORE TEMPS DROP OFF OVERNIGHT AND THE RAIN CHANGES TO SNOW. TEMPS WILL QUICKLY JUMP BACK ABOVE FREEZING DURING THE DAY SATURDAY...MELTING THE SNOW THAT HAS FALLEN. BY THIS POINT...DRY AIR SHOULD BE WORKING INTO THE REGION AS THE UPPER LEVEL LOW PULLS EAST OF EASTERN KY AND UPPER LEVEL HEIGHTS BEGIN TO INCREASE. SNOW WILL CHANGE BACK TO RAIN...AND THEN SLOWLY TAPER OFF DURING THE DAY SATURDAY. SOME LINGERING SHOWERS MAY STILL BE POSSIBLE HOWEVER IN THE FAR EAST AS WRAP AROUND MOISTURE CONTINUES TO FLOW BACK INTO THE REGION. THIS MOISTURE SHOULD FINALLY DEPART BY LATE SATURDAY NIGHT. HIGH PRESSURE SHOULD THEN TAKE HOLD OVER THE REGION INTO THE BEGINNING OF NEXT WEEK...WITH TEMPERATURES EXPECTED TO SLOWLY REBOUND. YET ANOTHER COLD FRONT IS EXPECTED TO IMPACT THE REGION BY LATE IN THE PERIOD TUESDAY INTO WEDNESDAY...BRINGING ANOTHER SHOT OF PRECIP ACROSS THE CWA. LUCKILY...THIS SYSTEM LOOKS NO WHERE NEAR AS POTENT AS THE ONE EXPECTED FOR THIS WEEKEND. AS FAR AS SNOW TOTALS AND TEMPERATURE EXPECTATIONS FOR THIS WEEKEND...UPSLOPE FLOW WILL KEEP HIGHEST SNOW AMOUNTS IN THE HIGHEST ELEVATIONS...BUT IT IS POSSIBLE FOR MANY LOCATIONS TO EXPERIENCE SOME ACCUMULATING SNOW. THE KEY WILL BE THE GROUND TEMPERATURE AS WELL...AS TO HOW MUCH OF THE SNOW STICKS AND HOW MUCH MELTS. STORM TOTAL SNOWFALL IS SHOWING BETWEEN 2.5 AND 3.0 INCHES OF SNOW IN THE HIGHEST TERRAIN...WITH BETWEEN 0.2 AND 1.0 INCHES ELSEWHERE ACROSS THE CWA. AS TEMPS RISE ABOVE FREEZING SATURDAY AND PRECIP BEGINS TO FALL AS RAIN...WHAT HAS ACCUMULATED WILL LIKELY QUICKLY MELT. EVEN AFTER THE PRECIP HAS PASSED...TEMPS SHOULD CONTINUE TO DROP AT OR BELOW FREEZING THROUGH THE BEGINNING OF THE WEEK. AS A RESULT...HAVE ADDED THE MENTION OF FROST FOR SATURDAY NIGHT/SUNDAY MORNING. BY THE END OF THIS WEEKEND...THE GROWING SEASON SHOULD BE DONE FOR THE YEAR. DAYTIME TEMPS BOTH SATURDAY AND SUNDAY SHOULD GENERALLY BE IN THE 40S /COLDEST SATURDAY/...WITH BUILDING HEIGHTS ALLOWING FOR REBOUNDING TEMPS INTO THE BEGINNING OF THE WEEK. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING) ISSUED AT 701 PM EDT WED OCT 29 2014 FORECAST CHALLENGE CONCERNS AN AREA OF MOISTURE THAT APPEARS TO DROP SOUTHEAST INTO OUR AREA OVERNIGHT. MOISTURE IS AT ABOUT THE 3K FT AGL LEVEL AND WOULD AGREE WITH UPSTREAM OBS AS A LARGE AREA OF SC IS ROTATING SOUTHWARD INTO THE OHIO VALLEY. QUESTION IS HOW FAR SOUTH WILL THIS AREA OF CLOUD COVER EXTEND. THIS APPEARS TO BRING AT LEAST MVFR CIGS TO SYM AND SJS. WHERE SKIES ARE CLEARER...LOZ AND SME...FOG WILL DEVELOP AND WILL DROP VIS FOR THESE LOCATIONS IN THE TAFS. VFR CONDITIONS WILL THEN RETURN INTO THE DAY ON THURSDAY. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...SHALLENBERGER SHORT TERM...RAY LONG TERM...JMW AVIATION...RAY/SHALLENBERGER

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