Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 140420 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 1120 PM EST SAT FEB 13 2016 .UPDATE... ISSUED AT 1120 PM EST SAT FEB 13 2016 WITH THE 00Z MODEL RUNS COMING IN THIS EVENING...HAVE UPDATED THE FORECAST WITH THE LATEST DATA. WARMER AIR MOVING IN A BIT QUICKER SUNDAY NIGHT WILL CHANGE THE SNOW OVER TO RAIN A BIT QUICKER. SO HAVE UPDATED THE FORECAST TO INPUT A NONDIURNAL TREND INTO THE FORECAST SUNDAY NIGHT. THIS DOES IMPACT SNOW TOTALS A BIT BUT STILL EXPECTING THE 3 TO 5 INCHES OVER A GREATER THAN 12 HOUR PERIOD. HOWEVER...THE MOST RECENT RUNS OF THE GFS AND NAM HAVE HINTED AT A BAND DEVELOPING BETWEEN THE MOUNTAIN AND HAL ROGERS PARKWAYS. INTENSIFICATION OF THIS AREA MAY BE ENOUGH TO PUT DOWN A SIGNIFICANT AMOUNT OF SNOW BEFORE THE PRECIP CHANGES OVER TO RAIN. THE OTHER CONCEPT IS THE HIGHER TERRAIN TO THE SOUTHEAST WHERE TEMPS WILL BE LOW ENOUGH FOR A LATER CHANGE OVER TO SNOW BUT TAKING THE BANDED PRECIP LONGER TO DEVELOP THERE. THE UNCERTAINTY OF TWO FACTORS MAKE CONFIDENCE LOW ENOUGH TO CONTINUE WITH THE ADVISORY. A NEW ZFP HAS BEEN SENT OUT WITH THIS UPDATE. UPDATE ISSUED AT 700 PM EST SAT FEB 13 2016 ISSUED AN UPDATE TO FRESHEN UP THE HOURLY TEMPERATURES AND DEW POINTS AND ADJUST THE HOURLY TEMPERATURE TREND. TEMPS ARE A BIT SLOW TO DROP THIS EVENING BUT AS THE NEXT FEW HOURS PASS...MOST TEMPS WILL BEGIN TO DROP OFF A FEW DEGREES PER HOUR. THE UPDATED GRIDS HAVE BEEN SENT TO NDFD AND WEB SERVERS. && .SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT) ISSUED AT 342 PM EST SAT FEB 13 2016 AS HIGH PRESSURE MOVED INTO THE REGION FROM THE NW TODAY...MUCH OF EASTERN KY EXPERIENCED NW FLOW...ENHANCED IN THE MID AND UPPER LEVELS BY A STRONG UPPER LEVEL TROUGHING PATTERN. THIS NW FLOW ALLOWED MOISTURE FROM LAKE MICHIGAN TO FLOW AS FAR SOUTH AS EASTERN KY...AND RESULTED IN SCATTERED PATCHES OF SNOW FLURRIES THROUGHOUT THE DAY...ESPECIALLY ACROSS THE NORTHERN AND FAR EASTERN CWA. AS HIGH PRESSURE SETTLES IN CLOSER TO THE REGION THIS AFTERNOON...WINDS WILL CONTINUE TO LIGHTEN AND PREVENT BEST MOISTURE FROM PROTRUDING SO FAR SOUTHWARD INTO THE OHIO VALLEY...CUTTING OFF ANY FURTHER FLURRY ACTIVITY. OTHERWISE...WITH HIGH PRESSURE PASSING OVERHEAD OVERNIGHT...THE MAIN ELEMENT OF CONCERN WILL BE TEMPERATURES. STRONG NW TO SE FLOW IN THE MID AND UPPER LEVELS WILL CONTINUE TO PULL DRIER BUT MUCH COLDER ARCTIC AIR INTO THE REGION. WITH MOSTLY CLEAR TO PARTLY CLOUDY SKIES EXPECTED THROUGH THE FIRST PART OF THE NIGHT...STRONG SUBSIDENCE WILL FORM...AND MAXIMUM RADIATIONAL COOLING WILL ENSUE. IT IS LIKELY THAT MANY OF THE DEEPER VALLEYS WILL SEE SINGLE DIGIT TEMPERATURES BY DAWN ON SUNDAY...WHILE MOST OF THE RIDGES WILL BE LUCKY TO SEE THE TEENS. THIS COUPLED WITH LIGHT WINDS COULD RESULT IN WIND CHILLS AROUND 0 OR EVEN SEVERAL DEGREES BELOW IN SOME LOCATIONS. BEHIND THE EXITING HIGH PRESSURE ON SUNDAY...WINDS WILL BECOME MORE SOUTHERLY...WITH TEMPERATURES RISING BACK INTO THE MID 20S TO LOW 30S. MEANWHILE...AN UPPER LEVEL WAVE WILL BEGIN STRENGTHENING ACROSS THE UPPER MIDWEST...MOVING EASTWARD TOWARDS THE MISSISSIPPI RIVER VALLEY DURING THE DAY. VEERING SURFACE WINDS IN WAKE OF THE DEPARTING RIDGE WILL USHER IN WARMER AIR ALOFT LATER TONIGHT INTO SUNDAY. THIS WILL HELP DRAW A STREAM OF GULF MOISTURE NORTH AHEAD OF THIS UPPER DISTURBANCE. TOP-DOWN MOISTENING WILL LEAD TO INCREASING HIGH-MID CLOUD COVER FROM LATE TONIGHT THROUGH THE DAY SUNDAY...BEFORE LOW CLOUDS AND RESULTING SNOW COMMENCES SUNDAY AFTERNOON. AS TEMPERATURES FALL SEVERAL DEGREES SUNDAY NIGHT...WE CAN PRETTY MUCH ENSURE THAT ALL PRECIPITATION BETWEEN SUNDAY AFTERNOON AND MONDAY MORNING WILL FALL IN THE FORM OF SNOW. THE NAM CONTINUES TO BE THE MOST AGGRESSIVE ON TIMING...AND THE OUTLIER AS SUCH...SO TRENDED MORE TOWARDS A ECMWF AND GFS SOLUTION FOR BOTH TIMING AND SNOW RATIOS. GENERALLY AGREED WITH WPC QPF GUIDANCE...WHICH WHEN PAIRED WITH FORECASTED SNOW RATIOS...RESULTED IN TOTAL SNOWFALL ACROSS THE REGION BETWEEN SUNDAY AFTERNOON AND MONDAY MORNING IN THE 2.5 TO 4.5 RANGE. DUE TO THE ELONGATED NEARLY 24 HOUR TIME PERIOD OF SNOW...THIS ONLY FALLS INTO ADVISORY CRITERIA. AFTER SOME GOOD COLLABORATION WITH NEIGHBORING OFFICES...WE DECIDED TO HOIST OUR ADVISORY WITH A START TIME OF 18Z SUNDAY...AND ENDING 15Z MONDAY. .LONG TERM...(MONDAY THROUGH SATURDAY) ISSUED AT 350 PM EST SAT FEB 13 2016 WAVE RESPONSIBLE FOR THE SYSTEM ON MONDAY HAS JUST MOVED ONSHORE AND SHOULD BE SAMPLED BETTER BY OUR UPPER AIR NETWORK THIS EVENING FOR THE 00Z MODELS. IN THE MEANTIME...WE ARE STILL DEALING WITH SOME MODEL DISCREPANCIES...AND WILL STAY CLOSE TO A BLENDED APPROACH AS POSSIBLE TO HEDGE FROM THE VARIOUS SOLUTIONS. AS IT STANDS NOW...LOOKS LIKE A SNOW SHOULD TRANSITION OVER TO RAIN MONDAY MORNING AS A SOMEWHAT DEEP WEDGE OF WARM AIR SPREADS NORTHWARD MONDAY MORNING ACROSS EASTERN KENTUCKY. WHERE THE MODELS DIFFER, IS HOW WRAPPED UP THE SYSTEM GETS AND THUS HOW FAR NORTH THE WARM AIR CAN MAKE IT. FOR NOW...OPTING TO GO WITH THE RAIN FOR MUCH OF THE DAY MONDAY. IT DOES APPEAR AS MOISTURE PULLS OUT MONDAY NIGHT...WE MAY SEE SNOW MIX BACK IN OR COMPLETELY CHANGE BACK OVER. HOWEVER...MODELS ARE SUGGESTING A FASTER END TO THE PRECIPITATION MONDAY NIGHT...SO ANY ACCUMULATIONS MAY BE MORE LIMITED. THE BRIEF LULL WILL BE SHORT INTO TUESDAY AS ANOTHER CLIPPER DIVES SOUTH ACROSS THE AREA. RIGHT NOW...MODELS ARE FAVORING A MORE NORTHERN TRACK...WHICH WOULD KEEP ALL PRECIPITATION PRIMARILY RAIN AT THE ONSET TUESDAY AFTERNOON/EVENING. AS THE SYSTEM PASSES BY...COLD AIR WILL SPREAD BACK IN AND WE MAY SEE A CHANGEOVER TO SNOW WITH SOME VERY LIGHT ACCUMULATIONS POSSIBLE. MUCH LIKE THE PAST FEW SYSTEMS...LIGHT FLURRIES/SNOW SHOWERS COULD LINGER WELL INTO WEDNESDAY BEFORE DISSIPATING. FINALLY WE SHOULD DRY OUT HEADING INTO THURSDAY AND FRIDAY AS HEIGHTS START TO BUILD OVER THE REGION. THIS WILL YIELD A MORE SIGNIFICANT WARM UP AS WE HEAD INTO THE LATE WEEK PERIOD. ANOTHER SYSTEM MAY PUSH ACROSS THE AREA LATE FRIDAY. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING) ISSUED AT 700 PM EST SAT FEB 13 2016 EXPECT VFR CONDITIONS THROUGH TONIGHT AS HIGH PRESSURE SLOWLY MOVES THROUGH THE AREA TONIGHT. UPPER LEVEL CLOUD COVER WILL BE ON THE INCREASE AHEAD OF THE NEXT SYSTEM MOVING INTO EASTERN KENTUCKY. MID AND LOW LEVEL CLOUD COVER WILL BEGIN TO MOVE INTO THE AREA BY MIDDAY WITH MVFR AND BELOW CONDITIONS EXPECTED. SNOWFALL WILL DROP VIS DOWN TO 2 MILES AT MOST LOCATIONS. EXPECT IFR THROUGH THE END OF THE PERIOD. WINDS WILL BE LIGHT THROUGH MUCH OF THE PERIOD. && .JKL WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY FROM 1 PM SUNDAY TO 10 AM EST MONDAY FOR KYZ044-050>052-058>060-068-069-079-080-083>088-104-106>120. && $$ UPDATE...SHALLENBERGER SHORT TERM...JMW LONG TERM...KAS AVIATION...SHALLENBERGER

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