Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 290600 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 200 AM EDT SUN MAR 29 2015 .UPDATE... ISSUED AT 200 AM EDT SUN MAR 29 2015 FORECAST IS GENERALLY ON TRACK. DID TWEAK OVERNIGHT LOWS UP JUST SLIGHTLY AS THE DROP OFF THROUGH THE EVENING AND EARLY THIS MORNING HAS NOT BEEN QUITE WHAT WAS EXPECTED. OTHERWISE BROUGHT HOURLY GRIDS IN LINE WITH LATEST OBS. UPDATE ISSUED AT 1045 PM EDT SAT MAR 28 2015 THE INVERSION IS STARTING TO SHOW UP ACROSS THE AREA WITH THE WINDS GOING LIGHT. THIS MEANS THAT TEMPS WILL FALL QUICKER IN THE VALLEYS THAN THE RIDGES THROUGH THE NEXT COUPLE OF HOURS. RECORDS WILL LIKELY FALL ACROSS THE AREA THIS NIGHT AND JKL IS ALREADY POISED TO SET ONE AFTER MIDNIGHT WITH THE TEMP CURRENTLY BELOW 32 DEGREES...AT 29. THE RECORD LOW OF 32 ON THE 29TH WAS INITIALLY SET IN 1991 AND TIED EACH OF THE PAST TWO YEARS. HAVE FINE TUNED THE TEMPS AND DEWPOINTS FOR THE REST OF THE NIGHT PER THE LATEST OBS AND TRENDS. THE UPDATED GRIDS HAVE BEEN SENT TO THE NDFD AND WEB SERVERS. UPDATE ISSUED AT 815 PM EDT SAT MAR 28 2015 23Z SFC ANALYSIS SHOWS HIGH PRESSURE SETTLING INTO THE OHIO VALLEY. WITH CLEAR SKIES...A DRY AIR MASS...AND WINDS GOING LIGHT...A GOOD NIGHT FOR RADIATIONAL COOLING IS UNDERWAY. EXPECT THE VALLEYS TO DECOUPLE SHORTLY AND THEIR TEMPERATURES TO START TO DROP DRAMATICALLY. CURRENTLY READINGS ARE GENERALLY IN THE LOW TO MID 30S ACROSS EASTERN KENTUCKY WHILE DEWPOINTS RANGE FROM THE SINGLE DIGITS NORTH AND ON THE RIDGES TO THE MID TEENS IN THE SOUTH AND IN SOME VALLEYS. HAVE UPDATED THE FORECAST TO CLEAR THE SKY COVER AND ALLOW FOR EVEN COLDER TEMPERATURES IN THE VALLEYS WHERE LOWS MAY BE CLOSER TO 10 DEGREES THAN 20 BY MORNING. THE UPDATED GRIDS HAVE BEEN SENT TO THE NDFD AND WEB SERVERS ALONG WITH AN UPDATED SET OF ZONES. && .SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT) ISSUED AT 317 PM EDT SAT MAR 28 2015 THE CENTER OF HIGH PRESSURE...CURRENTLY JUST SOUTH OF LAKE MICHIGAN...WILL CONTINUE TO TRACK TO THE SE THIS EVENING AND OVERNIGHT...REACHING EASTERN KY BY 6Z TONIGHT...AND EXITING TO THE SOUTH CAROLINA COAST BY 18Z TOMORROW. THE INFLUENCE OF THIS HIGH PRESSURE WILL BE IN PLACE TODAY THROUGH TOMORROW...WITH DRY AND COLD AIR BEING PULLED IN FROM THE NW. SOME FAIR WEATHER CU HAVE DEVELOPED ACROSS EASTERN KY...BUT WILL QUICKLY DIE OUT THIS EVENING WITH LOSS OF DAYTIME HEATING. THE SAME IS TRUE FOR ANY ONGOING WIND GUSTS. THE BIGGER CONCERN WILL BE TONIGHT AND TOMORROW UNDER THE INFLUENCE OF SUCH A DRY AIRMASS. WITH A HIGH PRESSURE SURFACE INVERSION DEVELOPING OVERNIGHT...LIGHT TO CALM WINDS AS THE HIGH PRESSURE PASSES NEARLY OVERNIGHT...WITH CREATE A SCENARIO FOR MAXIMUM LOSS OF DAYTIME RADIATIONAL HEATING. TEMPERATURES WILL DROP DOWN TO AROUND 20 DEGREES...WITH MANY OF THE VALLEYS FALLING FURTHER INTO THE MID TEENS. THIS IS A COUPLE DEGREE FURTHER DROP FROM THE PREVIOUS FORECAST. THESE TEMPS WILL LIKELY BREAK SEVERAL MIN TEMP RECORDS ACROSS THE CWA. THEN FOR TOMORROW...TEMPERATURES WILL RECOVER INTO THE LOW AND MID 50S AS SKIES REMAIN SUNNY AND WINDS SHIFT TO THE SOUTH BEHIND THE EXITING HIGH PRESSURE. HOWEVER...DRY AIR INFLUENCE WILL STILL BE IN PLACE...WITH DEW POINTS TAKING MUCH LONGER TO RECOVER. BY AFTERNOON...WE COULD BE EXPERIENCING SOME CRITICAL RH VALUES DOWN IN THE LOW TO MID TEENS ACROSS A GOOD PORTION OF THE CWA. MEANWHILE...A SURFACE LOW PRESSURE SYSTEM...POISED TO BE LOCATED JUST NORTH OF LAKE SUPERIOR AROUND 18Z TOMORROW...WILL CONTINUE TO SHIFT EASTWARD...PULLING A COLD FRONT ACROSS KY BETWEEN AROUND 3Z AND 12Z SUNDAY NIGHT/MONDAY MORNING. GIVEN THE FAST MOVING NATURE OF THIS SYSTEM...AND THE AMOUNT OF DRY AIR IN PLACE...EXPECT MINIMAL IMPACTS FOR ASSOCIATED POPS AND QPF. TEMPERATURES WILL REMAIN WARM ENOUGH FOR ANY PRECIP TO FALL AS LIGHT RAIN...BUT GENERALLY ONLY BETWEEN 0.1 AND 0.2 INCHES ARE EXPECTED BEFORE TAPERING OFF DURING THE MORNING HOURS MONDAY. .LONG TERM...(MONDAY THROUGH SATURDAY) ISSUED AT 245 PM EDT SAT MAR 28 2015 THE FORECAST PERIOD WILL BE ACTIVE WITH SEVERAL SHORT WAVES MOVING FAIRLY QUICKLY THROUGH ZONAL FLOW...WITH RAIN CHANCES INCREASING DURING THE LATTER HALF OF THE WEEK. THE ZONAL FLOW WILL RESULT IN MILD TEMPERATURES...AND AS INSTABILITY INCREASES LATER IN THE WEEK THUNDERSTORMS WILL ALSO BECOME POSSIBLE. THERE IS GOOD MODEL AGREEMENT TO START THE PERIOD...BUT SIGNIFICANT DIFFERENCES DEVELOP BY LATE IN THE WEEK. AT THE START OF THE PERIOD SURFACE HIGH PRESSURE WILL BE NOSING EAST FROM THE MID MS VALLEY...WHILE A SHORT WAVE AND ASSOCIATED SURFACE LOW MOVE INTO THE NORTHERN PLAINS. THIS LOW WILL TRACK INTO THE GREAT LAKES ON TUESDAY...BRINGING A WARM FRONT ACROSS THE AREA THAT WILL THEN BE QUICKLY FOLLOWED BY A COLD FRONT. HOWEVER...MOISTURE LOOKS TO BE LIMITED AND THE MODEL BLEND KEEPS THE FORECAST DRY FOR TUESDAY...WITH ONLY A SLIGHT CHANCE OF RAIN TUESDAY NIGHT. WILL FOLLOW NEIGHBORING WFOS TO N...E AND W...AND LOWER PROBABILTIES SLIGHTLY FOR TUESDAY NIGHT...THUS RESULTING IN NO MENTION OF RAIN FOR TUESDAY NIGHT. ANOTHER SHORT WAVE AND SURFACE LOW LOOK TO TRACK ACROSS ONTARIO ON THURSDAY...WITH ASSOCIATED FRONTS MOVING ACROSS OUR AREA AND BRINGING BETTER RAIN CHANCES. THE TRAILING COLD FRONT WITH THIS SYSTEM LOOKS TO STALL SOMEWHERE FROM THE GREAT LAKES OR OH VALLEY INTO THE SOUTHERN PLAINS...WITH LOW PRESSURE DEVELOPING OVER THE SOUTHERN PLAINS THURSDAY NIGHT. IT IS AT THIS POINT THAT THE MODELS BEGIN TO SHOW SIGNIFICANT DIFFERENCES. THE ECMWF IS VERY AGGRESSIVE WITH PHASING THE NORTHERN AND SOUTHERN STREAMS AS WE MOVE TOWARDS THE WEEKEND...WITH THE SOUTHERN PLAINS SURFACE LOW DEEPENING RAPIDLY AS IT MOVES TOWARDS THE GREAT LAKES ON FRIDAY. THE GFS IS MUCH WEAKER ALOFT AND AT THE SURFACE...WITH THE SURFACE LOW TRACKING MORE EASTWARD IN FLATTER FLOW. BOTH SCENARIOS RESULT IN SHOWER AND THUNDERSTORM CHANCES FOR OUR REGION...BUT THE ECMWF SOLUTION WOULD RESULT IN A SEVERE WEATHER THREAT AS WELL. THIS WILL NEED TO BE WATCHED AS WPC NOTES THE CANADIAN AND GFS ARE BEGINNING TO TREND TOWARDS MORE AMPLIFIED SOLUTIONS...BUT WPC AND WE ARE NOT YET COMMITTED TO THE FULLY PHASED ECMWF SOLUTION. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT) ISSUED AT 200 AM EDT SUN MAR 29 2015 SURFACE HIGH PRESSURE CENTERED OVER PORTSMOUTH OHIO WILL KEEP OUR SKIES CLEAR AND WINDS LIGHT THROUGH TOMORROW MORNING. AS THIS HIGH PRESSURE MOVE EASTWARD SOUTHERLY GRADIENT FLOW WILL INCREASE THROUGH THE DAY SUNDAY AHEAD OF APPROACHING COLD FRONTAL SYSTEM. WINDS SHOULD INCREASE TO AROUND 10KTS AND BECOME GUSTY LATER IN THE DAY. CLOUDS WILL INCREASE AND SCATTERED SHOWERS WILL BEGIN TO DEVELOP SUNDAY EVENING...GENERALLY FROM AROUND 03Z AND AFTER. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...RAY SHORT TERM...JMW LONG TERM...SBH AVIATION...RAY

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