Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 230302 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 1002 PM EST THU JAN 22 2015 .UPDATE...
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ISSUED AT 1002 PM EST THU JAN 22 2015 HIGH CLOUDS HAVE ENCOMPASSED MOST OF THE CWA WHILE LOWER CLOUDS ARE CONTINUING TO SHIFT NORTH OF THE REGION. AS SUCH...TEMPERATURES ARE CONTINUING TO FALL ACROSS THE REGION WITHOUT THE INFLUENCE OF A LOWER OR THICKER CLOUD DECK. BASED ON THE CURRENT TRENDS...WENT AHEAD AND LOWERED OVERNIGHT LOWS A FEW DEGREES IN THE HIGH TERRAIN AND SOME LOCATIONS ACROSS THE NORTH. MODELS ARE STILL SUPPORTING THE IDEA OF SOUTHERLY WINDS DEVELOPING JUST ALOFT BETWEEN 3 AND 6Z. AS SUCH...HIGH TERRAIN TEMPERATURES MAY CONTINUE TO DROP OFF FOR THE NEXT COUPLE OF HOURS...REACHING THEIR LOWS EARLY ON...BEFORE ACTUALLY RISING LATER TONIGHT AS THEY TAP INTO THESE WARMER WINDS. STILL EXPECTING LOW CLOUDS TO EVENTUALLY MAKE THEIR WAY BACK INTO THE SOUTHERN CWA LATE IN THE NIGHT...WHICH WILL STEADY OUT TEMPERATURES INTO THE MORNING IN THIS AREA AS WELL. CURRENTLY...ANY RETURNS FOR PRECIP ARE STILL CONTAINED WELL TO OUR SOUTH...SO POPS SEEM TO BE ON TRACK FOR THE REMAINDER OF THE NIGHT. AM A BIT CURIOUS THOUGH...AS OF NOW THE CURRENT FORECAST HAS SOME OF THE HIGHER TERRAIN SEEING SNOW AT THE ONSET OF THE PRECIP. HOWEVER...GIVEN THE WARM NOSE AND RISING TEMPS THROUGHOUT THE SECOND HALF OF THE NIGHT...WOULD BE CURIOUS IF TEMPS WILL ACTUALLY BE WARM ENOUGH TO SUPPORT MORE RAIN AT THE ONSET INSTEAD. THIS MAY BE SOMETHING TO WATCH AS POPS START TO MOVE NEARER TO THE REGION TOWARDS THE MORNING.
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&& .SHORT TERM...(THIS EVENING THROUGH SATURDAY) ISSUED AT 405 PM EST THU JAN 22 2015 THE MAIN FORECAST CHALLENGES FOR THE SHORT TERM PERIOD CENTER ON THE DEGREE OF CLEARING OF LOW CLOUDS TONIGHT AND AFFECTS ON MIN TEMPS AND THEN THE SYSTEM TRACKING ACROSS THE SOUTHEAST AND THEN TURNING UP THE EASTERN SEABOARD FROM FRIDAY INTO SATURDAY. A SHORTWAVE IS WORKING ACROSS THE OH VALLEY AND GREAT LAKES AND HAS MAINTAINED THE LOW LEVEL CLOUDS ACROSS THE NORTHERN AND SOUTHWESTERN PART OF THE CWA. MEANWHILE...THE SOUTHEASTERN COUNTIES HAVE SEEN THE LOW CLOUDS ERODE. MEANWHILE...A SHORTWAVE TROUGH EXTENDED FROM THE CENTRAL PLAINS INTO THE SOUTHERN ROCKIES WITH ASSOCIATED SFC LOW PRESSURE OVER THE WESTERN GULF OF MEXICO. ALSO AT THE SFC A RIDGE OF HIGH PRESSURE...BUT LACKING SIGNIFICANT COLD AND DRY AIR EXTENDED FROM THE PLAINS EAST INTO THE OHIO VALLEY. THE SHORTWAVE TROUGH WILL MOVE INTO THE SOUTHERN PLAINS AND MS VALLEY REGION TONIGHT AND INTO FRIDAY AND THEN TRACK ACROSS THE OH VALLEY AND SOUTHEAST FRIDAY NIGHT...BEFORE REACHING THE EASTERN SEABOARD BY THE END OF THE PERIOD. THIS TROUGH WILL GRADUALLY BE MERGING WITH A NORTHERN STREAM TROUGH TRACKING ACROSS SOUTHERN CANADA. THIS WILL CARVE OUT AN EASTERN TROUGH BY THE END OF THE PERIOD. MEANWHILE A SHORTWAVE WILL DROP INTO THE GREAT LAKES AND APPROACH THE OH VALLEY IN THIS NW FLOW AT THE END OF THE PERIOD. AN INVERTED TROUGH IS EXPECTED TO DEVELOP NORTH INTO THE REGION ON FRIDAY AS THE MAIN SHORTWAVE TROUGH AXIS APPROACH THE OH VALLEY. ISENTROPIC LIFT NORTH OF THE SYSTEM TRACKING ACROSS THE LAKES WILL BRING INCREASING MOISTURE ALOFT STARTING TONIGHT AND CONTINUING INTO FRIDAY. THIS WILL LEAD TO THE ATMOSPHERE MOISTENING UP FROM THE TOP DOWN. THERE WILL BE NO REAL COLD AIR IN PLACE NOR SFC HIGH NORTH OF THIS SYSTEM TO REINFORCE COLD AIR. THE TOP DOWN APPROACH AT PRECIP ONSET SUGGESTS THAT SOME SNOW COULD MIX WITH THE RAIN...MAINLY NEAR THE TN BORDER OR IN THE HIGHEST TERRAIN NEAR THE VA BORDER. HOWEVER...FROM MIDDAY FRIDAY THROUGH EARLY TO MID EVENING ON FRIDAY...ENOUGH WARM AIR WILL HAVE ADVECTED IN WITH THE INVERTED TROUGH FOR A CHILLY RAIN. AS THE SYSTEM REACHES THE CAROLINA COASTLINE AND CONTINUES TO DEEPEN SOMEWHAT COLDER AIR WILL ADVECT IN TO BEGIN CHANGING THE RAIN TO SNOW. OMEGA MAY ALSO BE SIGNIFICANT ENOUGH TO LEAD TO SOME DYNAMIC COOLING AS WELL IN THE WRAPAROUND DEFORMATION TYPE BAND THAT WILL WORK ACROSS EAST KY ON FRIDAY NIGHT INTO EARLY ON SATURDAY. THE GFS ON AVERAGE TENDS TO BE A BIT COLDER THAN THE NAM WITH THE COOLING LEADING TO BELOW NORMAL CONFIDENCE AT THIS TIME RANGE...BUT BOTH COOL OFF MOST OF THE AREA TO MARGINALLY COLD ENOUGH LEVELS FOR SNOW BEFORE THE PRECIP ENDS. HOWEVER...THE MODEL CONSENSUS IS FOR BETTER CHANCES FOR ACCUMULATIONS OUTSIDE OF THE HIGHEST RIDGES NEAR THE BA BORDER WILL BE ON THE RIDGES OF THE COAL FIELD REGION AS COMPARED TO THE DEEPER VALLEYS. THE ATMOSPHERE WILL COOL AND DRY OUT RATHER QUICKLY BEHIND THIS SYSTEM AND IN ADVANCE OF THE APPROACHING SYSTEM LATE IN THE PERIOD. THIS WILL LEAD TO HIGHEST POPS IN THE SOUTHEAST EARLY ON SATURDAY AND DRY WEATHER ACROSS THE FAR NW. THE EXTENT OF ANY CLEARING WILL DETERMINE LOW TEMPS TONIGHT AND IF AND WHERE CLEARING DOES OCCUR A RIDGE/VALLEY SPLIT WILL OCCUR. TEMPERATURES WILL ALSO BE TRICKY ON FRI PENDING ON HOW QUICK THE CLOUDS THICKEN. THE SOUTHERN PART OF THE AREA SHOULD EXPERIENCE THE PRECIP SHIELD ARRIVING FIRST AND THIS SHOULD LEAD TO HIGHS LIKELY BELOW MOS GUIDANCE. MIN T FRI NIGHT OUTSIDE OF THE HIGHEST TERRAIN WILL BE NEAR THE FREEZING MARK...LIKELY SLIGHTLY ABOVE IN SOME DEEPER VALLEYS. WITH SOME CLEARING BEHIND THE SYSTEM ON SATURDAY...TEMPERATURES SHOULD MODERATE TO THE UPPER 30S TO MID 40S. .LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY) ISSUED AT 401 PM EST THU JAN 22 2015 THE EXTENDED FORECAST PERIOD WILL BEGIN ON SATURDAY NIGHT WITH A POTENT SHORTWAVE EXITING THE EAST COAST. THE UPPER LEVEL FLOW KEEPS AN ACTIVE MERIDIONAL PATTERN THROUGH THE START OF THE EXTENDED WITH A DEEP TROUGH OVER THE EASTERN CONUS. FOR THE SUNDAY THROUGH MONDAY NIGHT PERIOD...A STRONG WAVE MOVES SOUTHEAST THROUGH THE OH VALLEY AND UPPER TN VALLEY. HEADING INTO MONDAY...A 140 KNOT JET STREAM PUSHES SOUTHEAST INTO THE SOUTHEASTERN CONUS BY MONDAY NIGHT AS THE LONGWAVE TROUGH OVER THE EASTERN CONUS DEEPENS FURTHER. THIS FEATURE FINALLY SHIFTS EAST BY THURSDAY AS RIDGING ATTEMPTS TO DEVELOP INTO THE AREA. THE MAIN FEATURE THROUGH THE EXTENDED WILL BE WITH A COLD FRONT MOVING THE AREA FROM THE UPPER PLAINS. SOME CONCERN WITH THESE CLIPPER TYPE SYSTEMS MAY BE AMOUNT OF MOISTURE AVAILABLE. FOR NOW...MODELS HINT AT SOME POSSIBLE RAINFALL AND SNOW ACCUMULATION AS WELL. DEVELOPED SURFACE HIGH PRESSURE OVER THE EAST COAST WILL KEEP THIS SYSTEM FROM EXITING QUICKLY AND WILL LIKELY KEEP PRECIP OVER EASTERN KENTUCKY A BIT LONGER THROUGH MONDAY NIGHT. THE ONE CONCERN HERE FOR SNOWFALL MONDAY AFTERNOON THROUGH MONDAY NIGHT WILL BE HOW FAST THE COLDER FILTERS INTO THE AREA...THE AVAILABLE MOISTURE...AND THE WIND DIRECTION BEHIND THE FRONT FOR POSSIBLE UPSLOPE SNOW SHOWERS THROUGH MONDAY NIGHT. FOR NOW...HAVE PUT SOME SNOWFALL INTO THE FORECAST BUT ONLY LIGHT ACCUMULATIONS. DRY CONDITIONS WILL THEN BE ON TAP FOR THE REST OF THE EXTENDED AS HIGH PRESSURE SETTLES INTO THE AREA FOR THE TUESDAY THROUGH WEDNESDAY NIGHT TIME FRAME. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING) ISSUED AT 631 PM EST THU JAN 22 2015 MVFR CIGS CONTINUE TO PLAGUE MUCH OF THE NORTHERN CWA...INCLUDING KJKL...KSJS...AND KSYM. WHILE THESE CLOUDS CONTINUE TO MAKE A MOVE NORTHWARD AND EVENTUALLY OUT OF THE FORECAST AREA...HIGH CLOUDS ARE CONTINUING TO FILL IN FROM THE SOUTH. EXPECT THE TAF SITES CURRENTLY SEEING MVFR CONDITIONS TO IMPROVE TO VFR AS WE HEAD INTO THE FIRST HALF OF THE NIGHT. HOWEVER BY TOMORROW MORNING...CLOUDS WILL BEGIN A LOWERING TREND ONCE MORE AS A LOW PRESSURE SYSTEM TRACKS ACROSS THE SE. THIS WILL ALLOW RAIN TO START SPREADING NORTHWARD INTO THE AREA AS WELL...THOUGH DON/T EXPECT WIDESPREAD IMPACTS UNTIL THE VERY END OR EVEN AFTER THE VALID FORECAST PERIOD /18Z TOMORROW/. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JMW SHORT TERM...JP LONG TERM...SHALLENBERGER AVIATION...JMW

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