Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 231138 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 638 AM EST TUE DEC 23 2014 .UPDATE...
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ISSUED AT 638 AM EST TUE DEC 23 2014 NO UPDATE PLANNED THIS MORNING. SCATTERED SHOWERS CONTINUE TO SLIDE NORTH ACROSS THE WESTERN HALF OF THE AREA. LATEST HRRR IS FLUCTUATING A BIT NOW ON THE EXPECTED ARRIVAL OF MORE WIDESPREAD RAIN LATER THIS AFTERNOON...BUT STILL BRINGS MOST OF IT INTO THE AREA BY EARLY EVENING. WON`T MAKE ANY CHANGES AT THIS TIME AND SEE IF THE NEXT FEW RUNS LOCK ONTO BETTER TIMING.
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&& .SHORT TERM...(TODAY THROUGH WEDNESDAY) ISSUED AT 315 AM EST TUE DEC 23 2014 A CUT OFF LOW CONTINUES TO SPIN ACROSS THE CENTRAL PLAINS THIS MORNING WITH BROAD SOUTHWEST FLOW ACROSS THE OHIO RIVER VALLEY. LOW LEVEL FLOW REMAINS SOUTHEAST ACROSS EASTERN KENTUCKY. A LULL IN PRECIPITATION IS OCCURRING PRESENTLY ACROSS THE AREA AS THE LATEST WAVE RESPONSIBLE FOR SOME RAIN EARLIER TONIGHT HAS EXITED TO THE NORTH. HOWEVER...MORE SHOWERS ARE SPREADING NORTH OUT OF CENTRAL TENNESSEE AND WILL PROVIDE SOME RAIN INTO SOUTHERN KENTUCKY OVER THE NEXT FEW HOURS. THE BEST CHANCES FOR RAIN THROUGH MIDDAY WILL REMAIN ACROSS THE WESTERN HALF OF THE AREA. ANOTHER WILL EMERGE FROM THE UPPER LEVEL TROUGH AND PUSH NORTH ACROSS THE TENNESSEE VALLEY THIS AFTERNOON AND EVENING...BRINGING WIDESPREAD SHOWERS BACK TO THE AREA. THE SHOWALTER INDEX REMAINS NEGATIVE THROUGH THE NEXT 24 TO 36 HOURS ACROSS MOST OF THE AREA. THUS...ANY ENHANCED AREAS OF LIFT WILL PROVIDE THE POSSIBILITY OF SOME THUNDER. THE THUNDER THREAT SHOULD REMAIN ALL ELEVATED LATER TODAY AND TONIGHT. GIVEN THE TREMENDOUS LIFT ARRIVING LATE IN THE DAY AND THE WIDESPREAD COVERAGE DEPICTED IN THE HRRR...HAVE OPTED FOR CATEGORICAL POPS LATE IN THE DAY INTO TONIGHT. AS THIS INITIAL WAVE EXITS TO THE NORTH...WE MAY SEE ANOTHER LULL THROUGH A PORTION OF TONIGHT. HOWEVER...ANOTHER STRONG WAVE WILL PUSH NORTH LATE TONIGHT WITH AN AREA OF LOW PRESSURE TRACKING NORTHWARD ACROSS CENTRAL KENTUCKY. THIS WILL BRING ANOTHER ROUND OF WIDESPREAD SHOWERS AND EMBEDDED THUNDERSTORMS TO THE AREA. AS THE LOW PRESSURE SYSTEM STRENGTHENS AND HEADS INTO MICHIGAN ON WEDNESDAY...IT WILL SEND A STRONG COLD FRONT TO THE EAST ACROSS KENTUCKY. AGAIN...GOOD CONVERGENCE AND LIFT ALONG THE FRONT SHOULD PROVIDE ANOTHER PERIOD OF WIDESPREAD SHOWERS. THIS FRONT WILL ALSO PRODUCE THE BEST CHANCE OF THUNDER THROUGH THE FORECAST PERIOD AS IT CROSSES THE AREA IN THE AFTERNOON AND EVENING HOURS. THIS TIME AROUND...WE MAY BE ABLE TO GENERATE ENOUGH SURFACE BASED INSTABILITY TO POSSIBLY MIX DOWN SOME OF THE STRONGER WINDS AS THE SHOWERS ALONG THE FRONT PUSH EAST. THIS COULD YIELD WINDS 45+ KNOTS. EVEN WITHOUT THE INSTABILITY...SYNOPTIC WINDS WILL TURN QUITE GUSTY JUST BEHIND THE FRONT WITH WIND GUSTS REACHING AS HIGH AS 40 MPH AT TIMES. AS THE FRONT PUSHES EAST...WE SHOULD FINALLY SEE PRECIPITATION COME TO AN END FROM WEST TO EAST THROUGH THE EVENING HOURS WEDNESDAY AS A DRY SLOT OVERSPREADS THE AREA. TEMPERATURES WILL REMAIN ON THE MILD SIDE THROUGH WEDNESDAY WITH HIGHS WELL INTO THE 60S BOTH DAYS AND LOWS TONIGHT ONLY IN THE 50S. .LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY) ISSUED AT 425 AM EST TUE DEC 23 2014 THE PERIOD WILL BEGIN WITH A DEEP CLOSED LOW AND ASSOCIATED SFC SYSTEM CENTERED OVER THE GREAT LAKES REGION WITH A TROUGH EXTENDING SOUTH INTO THE MS VALLEY. RIDGING IS EXPECTED TO BE OFF THE SOUTHEAST US COAST WITH RIDGING ALSO OVER NORTHERN MEXICO AND INTO THE SOUTHERN AND CENTRAL ROCKIES. A TROUGH IS EXPECTED TO BE WORKING ACROSS THE NORTHWESTERN CONUS AT THAT POINT AS WELL. FROM THU INTO THE START OF THE WEEKEND...THE DEEP LOW INITIALLY OVER THE GREAT LAKES WILL TRACK NORTH ACROSS ONTARIO AND QUEBEC AND INTO THE MARITIMES WITH THE TRAILING TROUGH AXIS MOVING ACROSS THE AREA EARLY IN THE PERIOD ON WED NIGHT INTO EARLY ON THU. RIDGING SHOULD THEN WORK ACROSS THE EASTERN CONUS FROM LATER ON CHRISTMAS DAY INTO FRIDAY. MEANWHILE THE COLD FRONT TRAILING FROM THE SYSTEM MOVING THROUGH THE GREAT LAKES INITIALLY SHOULD HAVE EXITED INTO WV OR SHOULD EXIT INTO WV VERY EARLY IN THE PERIOD. A DRY SLOT SHOULD WORK ACROSS THE AREA EARLY IN THE PERIOD PER RECENT MODEL CONSENSUS FOLLOWED BY SOMEWHAT DEEPER WRAPAROUND MOISTURE LATER ON WED NIGHT. SFC HIGH PRESSURE WILL BUILD IN BEHIND THE DEPARTING LOW PRESSURE SYSTEM FOR THU NIGHT INTO FRI NIGHT. FROM WED INTO FRIDAY...A TROUGH WILL HAVE DEVELOPED AND WORKED ACROSS THE WESTERN CONUS AND SHOULD BE MOVING INTO THE PLAINS BY THE START OF THE WEEKEND. AT THAT POINT...THE MOST RECENT GFS AND ECMWF RUNS BEGIN TO DIFFER IN TIMING OF INDIVIDUAL WAVES BUT THERE IS A GENERAL THEME OF LOWERING HEIGHTS ACROSS THE EASTERN SEABOARD AND SOUTHEAST FROM THE WEEKEND INTO EARLY NEXT WEEK WITH A TROUGH OVER THE WESTERN INTO THE CENTRAL CONUS BECOMING INCREASINGLY BROAD WITH TIME. THE GENERAL CONSENSUS IS FOR A COLD FRONT TO ENTER THE LOWER OH AND APPALACHIAN REGION FROM FRI NIGHT INTO SATURDAY AND THEN SHIFT SOUTH OF THE REGION AS EARLY AS SAT AFTERNOON OR EVENING PER THE GFS AND AS LATE SAT NIGHT INTO SUN PER THE ECMWF. THE UPPER LEVEL TROUGH AND WRAPAROUND MOISTURE SHOULD LEAD TO SHOWER AND DRIZZLE CHANCES FROM WED NIGHT INTO MIDDAY ON THURSDAY. SOME SNOW COULD MIX IN AS WELL. LOCATIONS BELOW 2000 OR 2500 FEET ELEVATION SHOULD REMAIN ABOVE FREEZING ON WED NIGHT. BEHIND THE DEPARTING SYSTEM AND IN ADVANCE OF A SFC HIGH...THE LOW LEVEL FLOW WILL BECOME TOO SOUTHWEST FOR IDEAL UPSLOPE FLOW BUT LOW LEVEL LAPSE RATES WILL SUPPORT THE CHANCES FOR SHOWERS AND OR DRIZZLE. IN ADDITION...MODEL FORECAST SOUNDINGS INDICATE THAT ICE CRYSTALS COULD BE LOST AT TIMES LEADING TO LIGHT PRECIP POSSIBLY FALLING FROM CLOUDS WHERE ICE IS NOT PRESENT...LEADING TO JUST RAIN OR DRIZZLE AT TIMES. THERE MAY BE TIMES WHERE ICE IS PRESENT SO SOME FLURRIES OR LIGHT SNOW WOULD ALSO BE POSSIBLE...BUT CHANCES FOR THIS ARE BEST ON THE RIDGES. A BIT OF FREEZING DRIZZLE ALSO CANNOT BE RULED OUT LATE WED NIGHT INTO EARLY ON THURSDAY FOR ELEVATIONS ABOVE 2000 OR 2500 FEET ELEVATION. THE PRESSURE GRADIENT WILL REMAIN RATHER STEEP WELL INTO WED NIGHT...SO WIND GUSTS AS HIGH AS 35 TO 40 MPH WILL BE POSSIBLE. A SLIGHTLY STRONGER GUST CANNOT BE RULED OUT ABOVE 2500 FEET. AS THE MOISTURE BECOMES INCREASINGLY SHALLOW AS CHRISTMAS DAY PROGRESSES ANY LINGERING DRIZZLE SHOULD DISSIPATE WITH SOME PARTIAL CLEARING...ESPECIALLY IN WESTERN SECTIONS. HIGH PRESSURE SHOULD LEAD TO DRY WEATHER FOR THU EVENING INTO MOST OF FRIDAY NIGHT. BOTH OF SCENARIOS FROM THE 0Z GFS AND 0Z ECMWF RUNS POINT TOWARD MAINLY RAIN...POSSIBLY MIXING WITH OR CHANGING TO SNOW ON SAT INTO SAT NIGHT. CURRENT MODEL RUNS HAVE A WAVE DEVELOPING ON SAT INTO SAT NIGHT ALONG THE BOUNDARY THAT WILL HAVE PASSED TO OUR SOUTH WITH AN INVERTED TROUGH EXTENDING TO ITS NORTH IN RESPONSE TO A SHORTWAVE WORKING FROM HE SOUTHERN ROCKIES ACROSS THE SOUTHERN PLAINS AND INTO THE SOUTHEASTERN CONUS FROM SAT NIGHT INTO SUN NIGHT. THE MODELS TRACK THE SFC WAVE ACROSS THE SOUTHEASTERN STATES DURING THAT TIME. IF DEEP ENOUGH MOISTURE LINGERS AS THIS SYSTEM DEPARTS ON SUN NIGHT INTO EARLY ON MONDAY...SOME SNOW MIGHT MIX IN. OVERALL..TEMPERATURES THROUGH THE PERIOD WILL REMAIN NEAR NORMAL TO ABOVE NORMAL AS THE CORE OF THE COLDER AIRMASSES REMAINS MAINLY BOTTLED UP OVER CANADA AND NEARER TO THE US/CANADIAN BORDER. THE BIGGEST DEPARTURES SHOULD OCCUR FROM FRI INTO SATURDAY. SOME MODEL GUIDANCE SUGGESTS THAT AT LEAST A GLANCING BLOW OF COLDER AIR MAY AFFECT THE AREA AROUND THE MIDDLE OF NEXT WEEK...BUT THERE HAS BEEN PLENTY OF MODEL DIFFERENCES FROM RUN TO RUN AND MODEL TO MODEL DURING THAT TIME PERIOD. && .AVIATION...
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(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING) ISSUED AT 638 AM EST TUE DEC 23 2014 A MIX OF VFR/MVFR CONDITIONS WILL BE SEEN OVER THE NEXT 12 TO 24 HOURS AS A NUMBER OF WEAK DISTURBANCES PUSH NORTH AHEAD OF AN UPPER LEVEL TROUGH ADVANCING FROM THE WEST. SCATTERED SHOWERS WILL REMAIN POSSIBLE THROUGH THE DAY TODAY...WITH THE BEST CHANCES FOR MORE WIDESPREAD RAIN COMING LATER THIS EVENING. A DAMP NIGHT IS ON TAP FOR TONIGHT AS MORE RAIN CONTINUES TO SPREAD NORTHWARD ACROSS THE AREA. THIS WILL KEEP CIGS LOCKED AT MVFR LEVELS PERHAPS GETTING CLOSE TO IFR. SOME REDUCED VISIBILITIES WILL ALSO BE LIKELY WITH THE HEAVIER RAIN SHOWERS.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...KAS SHORT TERM...KAS LONG TERM...JP AVIATION...KAS

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