Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 291911 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 211 PM EST THU JAN 29 2015 .UPDATE... ISSUED AT 1225 PM EST THU JAN 29 2015 MADE MULTIPLE UPDATES BASED ON OBS AND NEW 12Z NAM. THIS INCLUDES RAISING TEMPS FOR TODAY AND ADJUSTING TEMPS FOR TONIGHT INTO FRIDAY. HAVE ALSO ADJUSTED SKY COVER TO ACCOUNT FOR TEMPORARY CLEARING TAKING PLACE TODAY. TIMED POPS BASED ON NEW 12Z NAM TO INCLUDE THE BREAK IN PRECIP THAT IS CURRENTLY OCCURRING. ADJUSTED SNOW POTENTIAL BASED ON -10C MOISTURE AVAILABILITY ALOFT FOR TONIGHT. UPDATE ISSUED AT 1113 AM EST THU JAN 29 2015 WITH PRECIP ON THE WAY OUT AND NO MORE OBSERVED TEMPS AT OR BELOW FREEZING IN VALLEYS AND READINGS CONTINUING TO WARM...HAVE ALLOWED THE WSW TO EXPIRE. HAVE ISSUED ANOTHER SPS UNTIL EARLY AFTERNOON FOR ANY LINGERING PREVIOUSLY EXISTING ICE. UPDATE ISSUED AT 1013 AM EST THU JAN 29 2015 WITH REPORTS OF MANY ACCIDENTS...ISSUED A FREEZING RAIN ADVISORY FOR LOCATIONS WHERE VALLEYS TEMPS ARE BELOW FREEZING AND PRECIP IS STILL OCCURRING. TEMPS ARE WARMING...SO THE ADVISORY ONLY RUNS FOR ABOUT ANOTHER HOUR. WILL EVALUATE TEMPS IN A WHILE TO SEE IF IT CAN EXPIRE. UPDATE ISSUED AT 844 AM EST THU JAN 29 2015 PRECIP SHIELD HAS MADE IT INTO OUR WESTERN FORECAST AREA. TEMPERATURES HAVE RESPONDED WELL WHERE MEASURABLE PRECIPITATION IS FALLING...HOWEVER SOME VALLEYS IN THE EAST STILL LINGER IN THE MID 20S. LOOKING AT RADAR TRENDS...THE MEASURABLE PRECIPITATION SEEMS TO BE HAVING A HARDER TIME COMING EAST WITH SOME DOWNSLOPE FLOW IN PLACE...AND READINGS HAVE BEEN EDGING UP EVEN IN THE COLDER SPOTS PRIOR TO THE PRECIP ARRIVING. HAVE BEEFED UP POPS TO CATEGORICAL ACROSS THE BOARD...AND WILL CONTINUE TO MENTION A CHANCE OF FREEZING RAIN...AS SOME SPOTTY SLICK SPOTS STILL LOOK POSSIBLE. UPDATES HAVE BEEN SENT. && .SHORT TERM...(TODAY THROUGH FRIDAY) ISSUED AT 400 AM EST THU JAN 29 2015 LATEST SURFACE MAP FEATURES HIGH PRESSURE ALONG THE EASTERN CONUS...WITH LOW PRESSURE MOVING INTO THE GREAT LAKES AND OHIO VALLEY REGIONS. ALOFT...A SHORT WAVE TROUGH IS ROTATING TOWARDS THE OHIO VALLEY...WITH ANOTHER TROUGH DROPPING SOUTHEAST INTO THE NORTHERN PLAINS...AND YET ONE MORE MOVING IN ACROSS SOUTH CENTRAL CANADA. MAINLY MID AND HIGH LEVEL CLOUDS HAVE BEEN STREAMING IN ACROSS EASTERN KENTUCKY. THE SOUTHERLY WIND FLOW OUT AHEAD OF THE APPROACHING SURFACE LOW HAS ALLOWED FOR A NICE RIDGE/VALLEY SPLIT ACROSS THE AREA...WITH MORE SHELTERED VALLEYS HOLDING IN THE LOW AND MID 20S...WHILE RIDGE TOPS ARE IN THE LOW TO MID 30S. THE MODELS ARE IN GOOD AGREEMENT THROUGH THE SHORT TERM...TAKING THE LOW PRESSURE SYSTEM EAST ACROSS THE OHIO VALLEY DURING THE DAY...AND ALLOWING THE ASSOCIATED SURFACE COLD FRONT TO MOVE THROUGH THE AREA THIS AFTERNOON INTO EARLY THIS EVENING. MEANWHILE...THE MORE NORTHERN SHORT WAVES WILL CONTINUE TO DROP SOUTHEAST IN SUCCESSION...HELPING TO ESTABLISH A DEEP TROUGH ACROSS THE EAST BY FRIDAY. THE CURRENT RADAR SHOWS A BAND OF LIGHT RAIN FROM SOUTH CENTRAL INDIANA DOWN THROUGH WESTERN KENTUCKY. THE LATEST HRRR SHOWS THIS ACTIVITY MAKING IT TO OUR DOORSTEP BY DAWN OR SHORTLY THEREAFTER... ALTHOUGH THERE IS GOOD AGREEMENT THAT THE MAJORITY OF THE MEASURABLE PRECIPITATION WILL STAY JUST NORTH...WITH MORE SPOTTIER ACTIVITY TO CONTEND WITH ACROSS OUR AREA THROUGH 14Z. AFTER 14Z...PRECIPITATION LOOKS TO BLOSSOM AS THE BETTER FORCING ARRIVES. HAVE BEEN CONCERNED WITH THE COLD VALLEY READINGS ACROSS OUR AREA...HOWEVER IT LOOKS AS THOUGH THAT BY THE TIME THE BETTER PRECIPITATION DOES MOVE IN...THAT MOST LOCATIONS WILL BE ABOVE FREEZING. AS SUCH...WILL ISSUE A SPECIAL WEATHER STATEMENT COVERING THE SPOTTIER PRECIPITATION AT ONSET...AS MAINLY INTERIOR LOCATIONS WILL STILL LIKELY BE BELOW FREEZING. WILL CONTINUE TO MONITOR TRENDS VERY CLOSELY OVER THE NEXT FEW HOURS SINCE ANY RAMP UP IN THE PRECIPITATION WILL MEAN AN ICY COMMUTE POTENTIALLY. ONCE THE FIRST BATCH OF PRECIP MOVES THROUGH LATER THIS MORNING INTO EARLY THIS AFTERNOON...THERE WILL LIKELY BE A LULL IN THE ACTIVITY...BEFORE THE COLDER AIR ARRIVES ON NORTHWEST WINDS AND THE TROUGH AXIS MOVES THROUGH TONIGHT. THIS WILL ALLOW FOR SOME LIGHT SNOW ACROSS THE AREA. SNOW SHOWERS WILL LIKELY LINGER IN THE EAST THROUGH FRIDAY MORNING...BEFORE TAPERING OFF. ANY LIGHT ACCUMULATIONS WILL FAVOR THE HIGHER TERRAIN IN THE FAR SOUTHEAST. .LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY) ISSUED AT 446 AM EST THU JAN 29 2015 HIGH PRESSURE WILL TAKE HOLD OF SENSIBLE WEATHER TO BEGIN THIS PERIOD. WHILE LOW PRESSURE THAT IS AFFECTING THE REGION TODAY DEVELOPS INTO ANOTHER STRONG COASTAL LOW ACROSS THE NORTHEAST US. THIS HIGH PRESSURE COUPLED WITH DECREASING CLOUDS WILL ALLOW FOR DECOUPLING AND LOWS DROPPING DOWN INTO THE MID TO UPPER TEENS AREA WIDE. THIS HIGH PRESSURE WILL ALLOW MOSTLY SUNNY SKIES EARLY IN THE DAY FOR YOUR SATURDAY WITH INCREASING CLOUDS IN THE AFTERNOON. WINDS WILL ALSO BECOME MORE SOUTHWEST BRINGING HIGHS ON SATURDAY INTO THE UPPER 30S TO LOWER 40S. NOW THE BIGGER CONCERN CONTINUES TO BE LATE WEEKEND STORM AND CONFIDENCE REMAINS LOW IN REGARDS TO THIS SYSTEM. THE SETUP IS WE HAVE A DEVELOPING UPPER LEVEL CLOSED LOW ACROSS THE NORTHERN BAJA PENINSULA AND ASSOCIATED DEVELOPING SURFACE LOW SATURDAY MORNING. MEANWHILE A UPPER LEVEL WAVE RIDES OVER RIDGING ACROSS THE NORTHWEST US. THEN THIS IS WHERE THE MODELS CONTINUE TO STRUGGLE IS IN THE PHASING PROCESS THAT OCCURS SATURDAY NIGHT IN THE UPPER LEVELS. EARLIER THE 18Z/28 GFS AND 12Z/28 ECMWF HAD A MORE OPEN WAVE WHICH TRANSLATED TO A WEAKER SURFACE LOW. THIS WAS NEW BASED ON THE PREVIOUS RUNS SEEN OVER THE PAST COUPLE OF DAYS. THE LATEST 00Z/29 RUN OF THE GFS DEVELOPS A STRONGER LOW WITH A BIT OF A DEEPER TROUGH SETTING UP. THE 00Z/29 ECMWF DOES HAVE SIMILARITIES...HOWEVER THE SURFACE LOW PRESSURE IS NOT AS DEEP. ONE THING THAT REMAINS WITH BOTH MODELS 00Z RUNS IS BOTH HAVE A GOOD AMT OF QPF RESPECTIVELY. ANOTHER QUESTION THAT REMAINS IS HOW MUCH COLD AIR STAYS IN PLACE WITH THIS SYSTEM ON SUNDAY AND THIS WILL DEPEND HEAVILY ON THE EVENTUAL TRACK OF THIS SURFACE LOW. THAT SAID HAVE LEANED TOWARD A BIT COLDER THROUGH THE DAY ON SUNDAY. THINKING STILL MUCH OF SUNDAY WOULD LEAD TO MIXING ACROSS MUCH OF THE CWA WITH MORE IN THE WAY OF SNOW ACROSS THE BLUEGRASS WHERE TEMPS REMAIN COOLER...HOWEVER CONFIDENCE IN THIS SYSTEM REMAINS LOW GIVEN THE DRASTIC RUN TO RUN CHANGES SEEN IN THE DETERMINISTIC MODELS. ALSO KEEPING IN MIND THAT THE ENSEMBLE MEAN HAS BEEN QUITE ERRATIC AND GIVEN THAT THE 12 PERTURBATIONS IN OUR SYSTEM ARE ERRATIC EXPLAINS THE LACK OF CONTINUITY. ALL THIS SAID STILL THINK THERE IS A REASONABLE SHOT OF MEASURABLE SNOW SUNDAY INTO MONDAY. ANOTHER PIECE TO THE PUZZLE TO KEEP IN MIND IS THAT A MORE NORTHERLY TRACK SHOWN IN EARLIER RUNS COULD ALLOW FOR MORE SOUTHERLY FLOW AND WARMER AIR AND LEAD TO LESSENING SNOWFALL TOTALS. ALTHOUGH BEHIND THIS SYSTEM EXPECT COLD AIR TO FILTER INTO ALL OF THE CWA SUNDAY NIGHT INTO MONDAY. ALSO WOULD EXPECT GENERALLY FALLING TEMPERATURES DURING THE DAY ON MONDAY. AFTER THIS THE AFOREMENTIONED LOW PRESSURE IS THEN FORECAST TO TRACK NE AND CONTINUE TO DEEPEN ALONG NE ATLANTIC COAST. HIGH PRESSURE WILL BUILD EAST MONDAY NIGHT AND EXPECT ANOTHER COLD NIGHT WITH GENERALLY LOW TO MID TEENS ACROSS THE REGION. THESE TEMPS MAY HAVE TO BE ADJUSTED FURTHER DEPENDING UPON IF WE RECEIVE MEASURABLE SNOW. THIS HIGH PRESSURE WILL ADVANCE EAST OF THE REGION MOVING INTO THE DAY ON TUESDAY BRINGING RETURN FLOW AND WELCOMING REBOUND IN TEMPERATURE...WITH HIGHS IN THE MID TO UPPER 30S. THAT SAID WEDNESDAY REMAINS UNCERTAIN WITH YET ANOTHER SYSTEM DEVELOPING AND AT THIS POINT STUCK CLOSE TO THE BLEND. DID INTRODUCE MAINLY SLIGHT POPS DURING THAT PORTION OF THE PERIOD. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON) ISSUED AT 211 PM EST THU JAN 29 2015 VFR PREVAILED AT THE START OF THE PERIOD...BUT LOW VFR CEILINGS WERE PROGRESSING SE ACROSS THE REGION AFTER A PERIOD OF CLEARING. THE CEILINGS ON THE WAY IN WILL GET PROGRESSIVELY LOWER WITH TIME. BY 00Z MVFR CAN BE EXPECTED AREA WIDE...WITH IFR BEGINNING TO SHOW UP. SCATTERED LIGHT RAIN SHOWERS WILL ALSO DEVELOP DURING THE AFTERNOON. MOST AREAS WILL DEGRADE TO IFR TONIGHT...AND REMAINING RAIN SHOWERS WILL CHANGE TO SNOW SHOWERS. THE SNOW SHOWERS WILL TAPER OFF AND CEILINGS WILL START TO BREAK UP DURING THE DAY ON FRIDAY. WINDS WILL GUST IN THE NEIGHBORHOOD OF 15-20 KTS THROUGH THE PERIOD...INITIALLY FROM THE SW AND THEN SHIFTING TO THE WEST TONIGHT. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL SHORT TERM...GEOGERIAN LONG TERM...DJ AVIATION...HAL

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