Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 221137 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 637 AM EST MON DEC 22 2014 .UPDATE... ISSUED AT 637 AM EST MON DEC 22 2014 DESPITE THE UNFAVORABLE CONDITIONS...A FEW SPRINKLES HAVE DEVELOPED FROM BREATHITT COUNTY NORTHEAST INTO JOHNSON COUNTY. JOHNSON COUNTY MESONET IS STILL AT 31 DEGREES...BUT PRECIPITATION IS PROBABLY NOT HEAVY ENOUGH (AS OBSERVED HERE AT THE OFFICE) TO CAUSE MUCH OF AN ISSUE AND ALL OF THIS SHOULD BE A VERY SHORT TERM ISSUE AS THIS WILL ALL BE PUSHING OUT IN THE NEXT HOUR. ALSO...THE MESONET HAS BEEN COMING UP AS THE CLOUDS SPREAD BACK IN. UPDATED TO THROW IN SOME SPRINKLES FOR THE AFFECTED AREAS OVER THE NEXT HOUR OR TWO. && .SHORT TERM...(TODAY THROUGH TUESDAY) ISSUED AT 315 AM EST MON DEC 22 2014 EASTERN KENTUCKY SITS BETWEEN TWO SYSTEM EARLY THIS MORNING WITH THE FIRST SYSTEM PUSHING NORTH ACROSS THE CAROLINAS...WHILE THE SECOND ONE DROPPING SOUTHEAST INTO THE CENTRAL PLAINS. MID LEVEL SUBSIDENCE...COMBINED WITH LOWER LEVEL DOWNSLOPING SOUTHEAST FLOW HAS KEPT EASTERN KENTUCKY DRY OVERNIGHT. THE SYSTEM OVER THE CAROLINAS WILL SPREAD ATTEMPT TO SPREAD SOME MOISTURE BACK TO THE NORTHWEST AS IT MOVES NORTH THIS MORNING...BUT GIVEN THE HOSTILE ENVIRONMENT...COMBINED WITH LARGE DEWPOINT DEPRESSIONS...ITS ENOUGH TO WARRANT A DRY FORECAST THROUGH THE DAY. WE SHOULD SEE A MIX OF SUN AND CLOUDS TODAY AS CLOUDS HAVE A TOUGH TIME HANGING ON THROUGH THE DAY. THIS WILL HELP BOOST TEMPERATURES UP INTO THE 50S TODAY. A MID LEVEL WAVE ROUNDING THE BASE OF THE MID LEVEL TROUGH WILL PUSH NORTHEAST ACROSS THE OHIO RIVER VALLEY TONIGHT. HOWEVER...SOUTHEAST WINDS WILL PERSIST INTO TONIGHT. THE BEST FORCING APPEARS WILL STAY TO OUR WEST AND NORTH TONIGHT. WITH OUR WESTERN COUNTIES ON THE FRINGES. THUS..WILL BRING A SMALL CHANCE INTO OUR WESTERN ZONES OVERNIGHT. WE MAY SEE A LULL THROUGH MUCH OF TUESDAY...BUT AS THE MID LEVEL TROUGH ADVANCES EAST...ANOTHER STRONGER WAVE IS EXPECTED TO PUSH NORTH ACROSS THE TENNESSEE VALLEY...LEADING OT INCREASING RAIN CHANCES BY LATE IN THE DAY. A TRICKY TEMPERATURE FORECAST FOR TUESDAY...BUT IF WE CAN STAY DRY ENOUGH THROUGH THE DAY...READINGS INTO THE 60S SEEM LIKELY...BUT AN EARLIER ONSET TO RAIN OR MORE CLOUD COVER...COULD LIMIT HOW WARM WE GET. PLAN TO LIMIT RAIN CHANCES ON TUESDAY IN THE EAST AS SOME WEAK DOWNSLOPING CONTINUES AND COULD HOLD OFF RAIN UNTIL TUESDAY NIGHT. .LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY) ISSUED AT 315 AM EST MON DEC 22 2014 THE FOCUS OF THE EXTENDED PERIOD WILL BE THE TUESDAY NIGHT THROUGH CHRISTMAS MORNING TIME FRAME. A POWERFUL STORM SYSTEM IS EXPECTED TO FORM OVER THE SOUTHERN MISSISSIPPI RIVER VALLEY TUESDAY NIGHT INTO WEDNESDAY...AS A STREAK IN THE POLAR JET PHASES WITH A SOUTHERN STREAM JET STREAK OVER THE LOUISIANA MISSISSIPPI REGION. THIS SOUTHERN STORM SYSTEM IS EXPECTED TO PUSH ACROSS THE TENNESSEE AND OHIO VALLEY REGIONS AS A LARGE TROUGH OF LOW PRESSURE ALOFT MAKES ITS WAY ACROSS THE NORTHERN PLAINS AND GREAT LAKES REGION. BOTH THE ECMWF AND GFS MODELS WERE IN GOOD AGREEMENT WITH THE TIMING OF THIS LARGE WEATHER SYSTEM...ALONG WITH THE EVOLUTION OF PRECIPITATION ASSOCIATED WITH IT AND THE EASTWARD PROGRESSION OF THE SYSTEM. TEMPERATURES WILL BE QUITE WARM TO BEGIN THE PERIOD...WITH READINGS IN 50S EXPECTED BOTH TUESDAY NIGHT AND WEDNESDAY. PRECIPITATION WILL START OUT AS PERSISTENT MODERATE TO AT TIMES LOCALLY HEAVY RAIN SHOWERS. THIS RAIN WILL LAST THROUGHOUT CHRISTMAS EVE DAY. ONCE THE UPPER LOW MOVES OFF TO THE EAST...WINDS WILL SHIFT TO THE WEST CHRISTMAS EVE NIGHT INTO EARLY CHRISTMAS DAY. THIS WILL ALLOW SOME COLDER AIR TO FILTER INTO THE BEHIND THE DEPARTING WEATHER SYSTEM. AS A RESULT...THE RAIN WILL GRADUALLY MIX WITH SNOW LATE WEDNESDAY NIGHT INTO EARLY THURSDAY MORNING. THE LATEST MODEL SOUNDINGS ARE SUGGESTING THAT ICE CRYSTAL GROWTH ALOFT WILL BE LACKING...THEREFORE MAKING FOR ONLY VERY MEAGER AMOUNTS OF SNOW OCCURRING ACROSS THE AREA. BASED ON THAT...AND THAT FACT THE GROUND WILL BE QUITE WARM...VERY LITTLE IF ANY SNOW ACCUMULATION IS EXPECTED. THE OTHER ISSUE OF NOTE WITH THIS SYSTEM WILL BE THE WIND. AS THE UPPER LOW PRESSES EASTWARD AND STRENGTHENS...THE SURFACE WINDS WILL RESPOND IN KIND ACROSS EASTERN KENTUCKY. WINDS WILL BEGIN TO PICK UP QUITE A BIT DURING THE AFTERNOON HOURS ON WEDNESDAY...WITH SOUTHERLY WINDS OF 10 TO 20 MPH POSSIBLE. THE WINDS COULD GUST AS HIGH AS 30 TO 40 MPH FROM TIME TO TIME...PARTICULARLY AS THE UPPER LOW AND ITS ATTENDANT SURFACE COLD FRONT MOVE PAST THE AREA. TEMPERATURES TO BEGIN THE PERIOD WILL BE WELL ABOVE NORMAL...WITH READINGS TOPPING OUT IN THE MID TO UPPER 50S ON WEDNESDAY AND NIGHT TIME LOWS IN THE MID 30S WEDNESDAY NIGHT. AFTER THAT...THINGS WILL RETURN TO NORMAL AS THE COLD AIR SETTLES OVER THE REGION. HIGHS EACH DAY FROM CHRISTMAS DAY THROUGH THE WEEKEND ARE EXPECTED TO AT OR SLIGHTLY BELOW NORMAL. THE EXCEPTIONS TO THIS COULD BE FRIDAY AND FRIDAY NIGHT...WHEN ANOTHER WEATHER SYSTEM TRAVERSES THE REGION. TEMPERATURES ON FRIDAY COULD WARM INTO THE LOWER 50S AS WINDS SHIFT TO THE SOUTH AHEAD OF THE APPROACHING WEATHER SYSTEM. THE PERIOD OF THE FORECAST...HOWEVER...IS WHERE THINGS GET A BIT OUT OF SORTS. THE ECMWF MODEL HAS A LARGE...ROBUST...AND VERY MOIST WEATHER SYSTEM MOVING ACROSS THE REGION DURING THE WEEKEND...WHILE THE GFS IS FORECASTING A MUCH WEAKER AN NEARLY PRECIPITATION FREE WEATHER SYSTEM DURING THIS SAME PERIOD OF TIME. FINALLY DECIDED TO INCLUDE A SLIGHT CHANCE OF RAIN FOR THE SATURDAY SUNDAY TIME FRAME TO ACCOUNT FOR THE FACT THAT BOTH MODELS ARE PRODUCING SOME SORT OF PRECIPITATION FOR EASTERN KENTUCKY...WHILE AT THE SAME TIME ACCOUNTING FOR THE ENORMOUS DIFFERENCES BETWEEN THE TWO MODELS. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING) ISSUED AT 637 AM EST MON DEC 22 2014 CLOUDS WILL HOLD OVER THE AREA THIS MORNING WITH SOME PATCHY MVFR CONDITIONS POSSIBLE. HOWEVER...FOR THE MOST PART VFR CONDITIONS SHOULD PREVAIL. DOWNSLOPING SOUTHEAST FLOW OFF THE HIGH TERRAIN ERODE ANY MVFR CIGS BY 9 AM WITH VFR CONDITIONS EXPECTED THROUGH THE REST OF THE DAY. THE CLOUDS MAY DISSIPATE FOR A TIME THIS AFTERNOON...BEFORE HIGH/MID CLOUDS INCREASE AGAIN AHEAD OF OUR NEXT WEATHER SYSTEM. THUS...PLAN TO STICK WITH VFR CONDITIONS THROUGH THE TAF FORECAST PERIOD. SOME QUESTION AS TO IF/WHEN SHOWERS MOVE INTO EAST KENTUCKY TONIGHT...WITH ANY SHOWERS MOST LIKELY IN OUR SOUTH CENTRAL INTO NORTHERN KENTUCKY. WILL INCLUDE A VCSH IN THE SYM AND SME TAFS TO ACCOUNT FOR SOME UNCERTAINTY. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...KAS SHORT TERM...KAS LONG TERM...AR AVIATION...KAS

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