Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 260554 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 1254 AM EST MON JAN 26 2015 .UPDATE... ISSUED AT 1137 PM EST SUN JAN 25 2015 GIVEN THE WELL ABOVE NORMAL TEMPERATURES EXPERIENCED TODAY /SOME LOCATIONS IN THE 50S/...WE JUST REALLY HAVEN/T SEEN A LARGE COOL DOWN ACROSS MUCH OF EASTERN KY THROUGH MOST OF THE EVENING. THIS IS ESPECIALLY TRUE IN AREAS THAT HAVE NOT YET RECEIVED RAIN...OR HAVE ONLY RECEIVED A SMALL AMOUNT. THIS BEING SAID...OTHER THAN ELEVATIONS ABOVE 3000 FT...DON/T EXPECT RAIN TO START CHANGING OVER QUITE AS FAST AS WHAT WAS IN THE PREVIOUS FORECAST. WORKED TO ADJUST THE LOW TEMPERATURE FOR OVERNIGHT...BASED ON THE LATEST MODEL GUIDANCE AND SOUNDINGS...AS WELL AS BASED ON THE ONGOING CONDITIONS WITH TEMPERATURES AND COOLING DOWNSTREAM...PREVIOUS SNOW PACK...ETC. WENT WITH A BLEND OF THE CURRENT FORECAST...THE LATEST HRRR /WHICH SEEMS TO HAVE THE BEST INITIALIZATION FOR THIS SYSTEM/...AND A LITTLE INFLUENCE FROM THE GFS...WHICH TRENDED CLOSER TO OVERALL THINKING FOR THE LOW. THEN...ADJUSTED INDIVIDUAL LOCATIONS TO GET THEM WITHIN BETTER TOLERANCE...INCLUDING BUMPING UP BLACK MOUNTAIN TO 29 DEGREES AND OTHER TERRAIN ABOVE 2500 FEET TO BETWEEN 30 AND 32 DEGREES. FURTHER MORE...GIVEN THE SLOW PROGRESS OF TEMPERATURES FALLING...WENT AHEAD AND PUSHED BACK THE TIMING OF THE LOW TEMPERATURE TO 13Z MONDAY. FROM HERE...USED A MIXTURE OF THE CONS-SHORT AND HAND EDITING TO ADJUST THE DIURNAL CURVE FOR THE REMAINDER OF THE NIGHT. ALL THINGS CONSIDERED...THE SLIGHT UPTICK IN TEMPERATURE FORECAST WILL RESULT IN A SEVERAL HOUR DIFFERENCE IN THE RAIN CHANGING OVER TO SNOW. THIS WILL KEEP ANY SNOW ACCUMULATIONS OUT OF THE FORECAST THROUGH 12Z /WITH THE EXCEPTION OF BLACK MOUNTAIN/...AND LESS SNOW ACCUMULATION IN FOR DURING THE DAY TOMORROW. BLACK MOUNTAIN IS CURRENTLY AT 32 DEGREES...SO THEY MAY START TO MIX WITH SNOW AT ANY TIME. HOWEVER...MOST OF THE REST OF THE AREA WILL LIKELY NOT SEE SNOW MIXING IN UNTIL NEAR DAWN...THEN SLOWLY TRANSITION TO ALL SNOW BETWEEN NOON AND 3PM. BY THIS POINT...MODEL SOUNDINGS ARE SHOWING A STRONG AMOUNT OF DRY AIR CUTTING OFF SOME OF THE BEST ACCUMULATION POTENTIAL DURING THE AFTERNOON. OVERALL...SNOW TOTALS WERE LOWERED ACROSS THE CWA. EXPECT ELEVATIONS ABOVE 3000 FEET TO PICK UP THE HIGHEST AMOUNTS...BETWEEN 1 AND 2 INCHES. SOME OF THE OTHER RIDGES ACROSS THE AREA COULD SEE BETWEEN A HALF AN ONE INCH...BUT A MAJORITY OF THE CWA WILL ONLY PICK UP A HALF INCH OR LESS. MOST OF THIS IS STILL EXPECTED TO FALL BETWEEN 12 AND 18Z WHEN THE BEST LIFT AND MOISTURE AND TEMPERATURES COMBINE...AND SURFACE TEMPERATURES FINALLY FALL ENOUGH TO ALLOW FOR ACCUMULATING SNOW. UPDATE ISSUED AT 706 PM EST SUN JAN 25 2015 FRESHENED UP THE GRIDS WITH THE LATEST OBSERVATIONAL DATA FOR TEMPS...DEW POINTS...AND WINDS. THIS RESULTED IN LITTLE OVERALL CHANGE FROM THE ONGOING FORECAST. BASED ON THE CURRENT RADAR RETURNS...AND THE PWAT VALUES OVERNIGHT BEING AROUND A HALF INCH OR LESS...WENT AHEAD AND REDUCED ANY MENTION OF MODERATE RAINFALL/SNOWFALL TO LIGHT. JUST NOT SEEING A WHOLE LOT OF EVIDENCE AT THIS POINT FOR MODERATE TO HEAVY INTENSITIES...THOUGH SNOW COULD HAVE SOME HEAVIER SPOTS AT TIMES TOMORROW MORNING. LATEST NAM12 FORECAST SOUNDINGS REALLY START TO LOSE MOISTURE IN THE UPPER LEVELS BETWEEN 6 AND 9 Z...WITH NOT MUCH LIFT EITHER...ALSO SUPPORTING LIGHTER INTENSITIES. OTHERWISE...FORECAST SEEMS TO BE IN PRETTY GOOD SHAPE OVER THE NEXT FEW HOURS. THE CENTER OF THE LOW IS CURRENTLY OVER SOUTH CENTRAL KY AND MOVING OUR DIRECTION...WITH THE NEXT ROUND OF LIGHT RAIN ABOUT TO SPREAD ACROSS THE CWA OVER THE NEXT 1 TO 2 HOURS. && .SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT) ISSUED AT 409 PM EST SUN JAN 25 2015 SURFACE ANALYSIS AS OF 20Z ACROSS THE REGION FEATURES A SMALL LOW PRESSURE SYSTEM OVER THE LOWER MIDWEST TRACKING EAST INTO THE OH VALLEY THIS EVENING. AHEAD OF THIS...SOME SHOWER ACTIVITY HAS BEGUN TO MOVE INTO THE AREA THIS AFTERNOON WITH MORE WIDESPREAD PRECIP BACK WEST INTO WESTERN KENTUCKY AND SOUTHERN INDIANA. PLENTY OF SOUTHWEST FLOW TODAY AND WAA INTO THE AREA HAS ALLOWED FOR TEMPS TO RISE INTO THE UPPER 40S AND EVEN LOWER 50S ACROSS EASTERN KENTUCKY TODAY. MODELS SHOWING THE COLD FRONT TO MOVE THROUGH LATER TONIGHT AFTER 00Z WILL HAVE THE COLDER AIR MOVING IN LATER. THIS ADVECTION WILL BEGIN IN EARNEST JUST AFTER 06Z AS THE FRONT MOVES THROUGH. EXPECTING A CHANGE OVER IN THE HIGHER ELEVATIONS WITH ALREADY TEMPS AT BLACK MOUNTAIN REACHING ITS HIGH FOR THE DAY IN THE UPPER 30S AND IS NOW BEGINNING TO DROP OFF AT THIS HOUR. MODEL PROFILES SHOW A BRIEF PERIOD OF GOOD OMEGA THROUGH THE LAST FEW HOURS OF THE EVENT AS THE FRONT MOVES THROUGH. WITH COLD ENOUGH AIR MOVING IN...THERE COULD BE SOME QUICK BURSTS OF SNOW IN THE HIGHER ELEVATIONS AND EVEN IN THE VALLEYS WHERE COLDER AIR HAS FINALLY MOVED IN. SPEAKING OF TEMPERATURES...LATE TONIGHT AND INTO THE DAY ON MONDAY...TEMPS WILL BE FALLING INTO THE MORNING HOURS BUT SOME SLIGHT RADIATIONAL HEATING DURING THE DAY BEFORE THE CORE OF THE AIR MASS MOVES IN MONDAY AFTERNOON AND INTO MONDAY NIGHT WILL RESULT IN TEMPS RISING A DEGREE OR TWO OR HOLDING STEADY THROUGH THE DAY TOMORROW. TEMPS OVER THE HIGHER TERRAIN SHOULD SLOWLY FALL THROUGH THE DAY. WINDS AFTER FRONTAL PASSAGE MONDAY MORNING WILL THEN SWITCH AROUND TO THE NORTHWEST FOR A FAVORABLE DIRECTION FOR SOME UPSLOPE SNOW SHOWERS THROUGH MONDAY AFTERNOON. MOISTURE DEPTH HANGS AROUND THROUGH MONDAY MORNING AND INTO THE AFTERNOON WITH SOME DECENT LIFT REMAINING ACCORDING TO THE NAM AND GFS SO SOME DECENT SNOW SHOWERS WILL HANG AROUND THROUGH THE DAY ON MONDAY BEFORE TAPERING OFF TO FLURRIES FROM WEST TO EAST INTO MONDAY NIGHT. THE CORE OF THE AIR MASS MOVING IN WILL CAUSE TEMPS TO PLUMMET INTO THE MID 20S MONDAY NIGHT AND WILL LIKELY ADD TO THE THREAT OF HAZARDOUS AND SLICK ROADS. THEREFORE...HAVE ISSUED AN SPS TO HIGHLIGHT THIS THREAT. .LONG TERM...(TUESDAY THROUGH SUNDAY) ISSUED AT 420 PM EST SUN JAN 25 2015 A RATHER AMPLIFIED PATTERN IS EXPECTED TO BEGIN THE PERIOD. MODELS REMAIN IN GENERALLY IN GOOD AGREEMENT FOR MOST OF THE PERIOD...WITH DIFFERENCES INCREASING TOWARD THE END OF THE PERIOD. AT THE START OF THE PERIOD A TROUGH IS EXPECTED TO BE IN PLACE FROM THE GREAT LAKES SOUTH INTO THE MID ATLANTIC SATES AND OFF THE SOUTHEASTERN US COAST...WITH A RIDGE OF HIGH PRESSURE FROM MEXICO NORTH INTO THE SOUTHERN PLAINS AND ROCKIES. AT THE SFC THE A DEEP SFC LOW/BLIZZARD WILL BE MOVING ALONG THE NORTHEAST US COAST TO START THE PERIOD WITH A RIDGE OF HIGH PRESSURE AT THE SFC EXTENDING FROM ONTARIO INTO THE GREAT LAKES AND MS VALLEY REGION. A SERIES OF SHORTWAVES IN NW FLOW BETWEEN THE TWO WILL DROP FROM THE GREAT LAKES AND THROUGH THE OH VALLEY AND APPALACHIANS TUESDAY INTO TUESDAY NIGHT. THIS WILL BRING CHANCES FOR SNOW SHOWERS AND REINFORCE A COLD AIRMASS WITH 850 MB TEMPS TO FALL TO THE -8C TO -10C RANGE BY LATE TUE AFTERNOON AND TUE EVENING. AS THE TROUGH AXIS LIFTS TO THE NORTH AND EAST AND THE SFC LOW MOVES FURTHER UP THE EASTERN SEABOARD...HIGH PRESSURE WILL GRADUALLY BUILD INTO THE LOWER OH VALLEY REGION AND APPALACHIANS TUE NIGHT INTO WED. THE INFLUENCE OF THE RIDGING WILL WANE BY LATE WED NIGHT AS A SHORTWAVE MOVING AROUND THE RIDGE OVER THE ROCKIES AND A NORTHERN STREAM TROUGH BEGIN TO JOIN FORCES AND APPROACH THE GREAT LAKES AND MS VALLEY REGION AS WELL AS THE LOWER OH VALLEY REGION. THE ASSOCIATED SFC LOW SHOULD TRACK WELL NORTH OF THE AREA JUST TO THE SOUTH OF THE SOUTHERN GREAT LAKES AND INTO THE MID ATLANTIC STATES FROM WED NIGHT INTO THU NIGHT. THIS SYSTEM WILL HAVE SOMEWHAT LIMITED MOISTURE...AND THIS SHOULD BE ANOTHER EVENT WHERE THE ATMOSPHERE MOISTENS FROM THE TOP DOWN. AT THE ONSET...SOME SNOW COULD MIX IN PENDING THE STRENGTH OF WARM AIR ADVECTION AND MOISTURE ADVECTION LATE WED NIGHT INTO THU MORNING. THE CLOUDS ALSO MAY NOT THICKEN QUICK ENOUGH TO PREVENT AT LEAST A MINOR RIDGE/VALLEY SPLIT FOR THE VALLEYS ON WED EVENING. AT THIS POINT...A LOW IN THE MID TO UPPER 20S OCCURRING AROUND 6Z ON THU IS EXPECTED. COLDER AIR WILL WRAP BACK INTO THE REGION BEHIND THIS SYSTEM AND POSSIBLY CHANGE ANY PRECIP BACK TO SNOW AS IT DEPARTS. HIGH PRESSURE SHOULD THEN BUILD IN TO BRING A DRY START TO THE WEEKEND. THE ECMWF LOWERS HEIGHTS MORE SIGNIFICANTLY ACROSS THE REGION AS WELL AS THE GREAT LAKES AND EASTERN SEABOARD AT THE END OF THE PERIOD AND IS THUS MUCH COLDER WITH THE AIRMASS. ANY SHORTWAVES AT THE END OF THE PERIOD SHOULD BE RATHER MOISTURE STARVED WITH THE MODEL CONSENSUS FAVORING ANYTHING THAT FALLS BEING SNOW. FOR TEMPS LATE IN THE PERIOD...OPTED TO GO A TAD COLDER THAN THE CONSENSUS BLEND...MORE IN LINE WITH ISC CONSENSUS AND GIVING A BIT MORE CREDIT TO THE PAST 2 ECMWF RUNS. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT) ISSUED AT 1253 AM EST MON JAN 26 2015 TONIGHT WILL BE TRICKY IN TERMS OF CIGS AS SITES HAVE BEEN AROUND OR MVFR CEILINGS THUS FAR TONIGHT. THE QUESTION THEN BECOMES HOW QUICKLY TO WE SEE IFR CONDITIONS OVERNIGHT AND MORNING HOURS. RIGHT NOW HAVE SITES GOING IFR BY 10 TO 11 Z BEFORE SITES IMPROVE TO MVFR THIS AFTERNOON. THE LOW PRESSURE THAT HAS BEEN POISED TO MOVE ACROSS THE REGION IS TRACKING OVER EASTERN KY THIS HOUR AND WILL CONTINUE TO MOVE EAST TONIGHT. THIS WILL CONTINUE TO BRING PERIODS OF RAIN AND EVENTUALLY A CHANGEOVER TO SNOW AS WE MOVE INTO THE EARLY MORNING HOURS. THIS WILL THEN TRANSITION TO MORE SNOW SHOWER ACTIVITY AS WE MOVE INTO THE AFTERNOON. THIS LOW PRESSURE WILL ALSO USHER IN STRONGER NW FLOW LATER TONIGHT INTO TOMORROW WITH GUSTY WINDS AROUND 20 KNOTS POSSIBLE OVERNIGHT INTO THE DAY TODAY. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JMW SHORT TERM...SHALLENBERGER LONG TERM...JP AVIATION...DJ

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