Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 272346 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 746 PM EDT FRI MAR 27 2015 .UPDATE... ISSUED AT 746 PM EDT FRI MAR 27 2015 TEMPERATURES ALREADY FALLING BELOW FREEZING ACROSS NORTHERN KENTUCKY WITH SNOW FLURRIES ONGOING ACROSS MUCH OF THE AREA. BASED ON UPSTREAM OBS AND RADARS...IT LOOKS LIKE FLURRIES WILL LAST FOR SOME TIME TONIGHT BEFORE FADING AWAY LATE AND INTO TOMORROW MORNING. UPDATE ISSUED AT 548 PM EDT FRI MAR 27 2015 LATEST RADAR AND OBSERVATION TRENDS SUGGEST MAINLY FLURRIES EXPECTED THROUGH THE REST OF THE EVENING. ALSO...BASED ON UPSLOPE FLOW AND UPSTREAM CLOUD COVER...OPTED TO CARRY THE FLURRIES THROUGH THE NIGHT. TEMPERATURES ARE COOLING OFF A BIT FASTER WITH THE SUN SETTING...SO HAVE ADJUSTED THE HOURLY TREND SOME. && .SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT) ISSUED AT 355 PM EDT FRI MAR 27 2015 THE AXIS OF AN UPPER LEVEL LONGWAVE TROUGH IS CURRENTLY MOVING ACROSS THE OHIO RIVER VALLEY. ALONG THIS TROUGH AXIS...SOME WEAK INSTABILITY HAS FORMED AND IS LEADING TO SOME LIGHT SCATTERED PRECIP ACROSS WESTERN AND CENTRAL KY...AS WELL AS POINTS TO THE NORTH AND SOUTH. AS THE TROUGH CONTINUES TO SHIFT EASTWARD...EXPECT THIS PRECIP TO MAKE IT INTO OUR CWA OVER THE NEXT FEW HOURS...AND THEN TAPER OFF IN THE EVENING AS THE TROUGH EXITS AND WE LOSE ANY DAYTIME HEATING INFLUENCE. A COUPLE THINGS TO NOTE WITH THIS SYSTEM. FIRST...RETURNS THUS FAR TODAY ARE QUITE LIGHT...AND THE BEST RETURNS /WHERE PRECIP IS LIKELY ACTUALLY HITTING THE GROUND/ ARE CURRENTLY OVER NORTHERN TN AND SHIFTING SEWRD. IF SOME OF THE MODELS HOLD TRUE...THE LONGWAVE TROUGH MAY HAVE DUG FAR ENOUGH SOUTHWARD THAT THE BEST PRECIP WILL DEVELOP AND MOVE JUST TO OUR SOUTH AND THEN EASTWARD...ONLY TOUCHING OUR FAR SOUTHERN COUNTIES. WENT AHEAD AND INCLUDED SLIGHT CHANCES ACROSS A GOOD CHUNK OF THE CWA THOUGH...JUST IN CASE SOME OF THE OTHER RETURNS ACTUALLY DO START PRODUCING SOMETHING AS THEY SHIFT EASTWARD INTO OUR REGION. THE SECOND THING TO NOTE IS THE PRECIPITATION TYPE. WITH SUCH A DEEP UPPER LEVEL TROUGH...TEMPERATURES NEAR THE SURFACE ARE ONLY AROUND 40 DEGREES...BUT ALOFT ARE COOLING OFF AT A MUCH FASTER RATE...THEREBY CREATING A STRONG LAPSE RATE. WHILE THE THREAT OF THUNDER IS PROBABLY NOT GOING TO HAPPEN AT THIS TIME...STILL AGREE WITH PREVIOUS FORECAST THINKING THAT IT WOULDN/T BE OUT OF THE QUESTION THAT SOME ICE PELLETS FROM ALOFT COULD MAKE IT TO THE SURFACE AND MIX WITH THE RAIN. AS SUCH...HAVE THE MENTION OF BOTH RAIN AND SNOW THROUGH THIS EVENING...BEFORE TEMPS FINALLY DROP ENOUGH THAT SOME LOCATIONS /MAINLY THE HIGH TERRAIN/ WILL SEE ALL SNOW FOR A BRIEF PERIOD OF TIME. STILL NOT EXPECTING THIS SNOW TO AMOUNT TO MUCH...ONLY PUT IN 0.1 INCHES IN THE HIGH TERRAIN WITH THIS FORECAST PACKAGE. AFTER DISCUSSION WITH ILN AND LMK...THERE IS SOME CONCERN ABOUT THE POTENTIAL CLOUD COVER OVERNIGHT. IF THIS LONGWAVE TROUGH SINKS ANY FARTHER SOUTH...WE COULD GET THE SHOT OF DRIER AIR TO OUR NE. HOWEVER...IT IS LIKELY THAT THIS DRIER AIR WILL MAKE IT INTO ILN AND IND...AND CLOUDS WILL SHIFT SOUTHWARD INTO OUR AREA INTO THE EVENING. WHILE MANY OF THESE CLOUDS ARE DIURNALLY DRIVEN AND WILL DISSIPATE OVERNIGHT...THERE IS ENOUGH CLOUDS THAT THIS PROCESS MAY TAKE SOME TIME. AND WITH INCOMING HIGH PRESSURE AND A SUBSIDENCE INVERSION DEVELOPING OVERNIGHT...THERE COULD BE SOME CLOUDS WHICH GET TRAPPED BELOW THE INVERSION AND LINGER THROUGHOUT MUCH OF THE NIGHT...AT LEAST UNTIL WE GET ENOUGH SUNLIGHT/HEAT IN THE MORNING TO QUICKLY MIX THEM OUT. AS A RESULT...HELD ON TO CLOUDS A BIT LONGER THROUGHOUT THE NIGHT COMPARED TO PREVIOUS FORECAST...THOUGH MOST LOCATIONS SHOULD BE CLEAR SHORTLY AFTER SUNRISE TOMORROW. REGARDLESS...THESE CLOUDS WILL DO LITTLE TO HAMPER THE STRONG PULL OF NW AIR INTO THE REGION...AS TEMPS ARE STILL EXPECTED TO DROP WELL INTO THE LOW TO MID 20S. FOR TOMORROW...HIGH PRESSURE AND DRY WEATHER WILL BE THE STORY AS WE CONTINUE UNDER DRY NW FLOW. IN FACT...IT WON/T BE OUT OF THE QUESTION FOR SOME OF THE HIGHER ELEVATIONS TO TAP INTO SOME IMPRESSIVELY LOW DEW POINTS BY 12Z TOMORROW WHILE THE LLVL INVERSION IS STILL IN PLACE. AS THE INVERSION LIFTS AND MIXES OUT...THESE DEW POINTS ARE LIKELY TO RECOVER SOME...BUT OVERALL THE THEME THROUGH THE DAY WILL BE DRY. RH VALUES IN THE UPPER TEENS AND LOW 20S ARE EXPECTED BY THE AFTERNOON. THIS DRY AIR WILL HAVE AN EFFECT ON THE TEMPERATURE FORECAST FOR OVERNIGHT. NW FLOW ALOFT...WEAK WINDS NEAR THE SURFACE WITH HIGH PRESSURE NEARLY OVERHEAD...AND CLEAR SKIES WILL ALL BE IN PLAY. WE COULD SEE RECORD LOW TEMPERATURES ACROSS MUCH OF THE REGION BY 12Z SUNDAY...UPPER TEENS TO LOW 20S. EXPECT COLDEST TEMPERATURES IN THE VALLEYS...WITH SOME LOCALLY COOLER SPOTS POSSIBLE. .LONG TERM...(SUNDAY THROUGH FRIDAY) ISSUED AT 314 PM EDT FRI MAR 27 2015 THERE IS GENERAL MODEL AGREEMENT ON THE OVERALL MEAN PATTERN NEXT WEEK...WITH FAIRLY FAST ZONAL FLOW...AND A SERIES OF SHORT WAVE DISTURBANCES AND ASSOCIATED SURFACE FRONTS BRINGING PERIODIC CHANCES OF RAIN SHOWERS. WITH THIS TYPE OF PATTERN IT IS NOT SURPRISING THERE ARE TIMING DIFFERENCES AMONG THE MODELS WITH THE SHORT WAVES THAT WILL BE AFFECTING THE AREA NEXT WEEK. AT THE START OF THE FORECAST PERIOD SURFACE HIGH PRESSURE WILL BE SHIFTING OFF TO THE SOUTHEAST...PROVIDING FOR A SOUTH TO SOUTHWEST LOW LEVEL FLOW OF WARMER AIR. THIS WILL ALLOW TEMPERATURES TO REBOUND INTO THE LOWER TO MIDDLE 50S SUNDAY AFTERNOON AFTER A VERY COLD START TO THE DAY SUNDAY MORNING. A SHORT WAVE TROUGH MOVING OUT OF THE MS VALLEY AND AN ASSOCIATED SURFACE COLD FRONT WILL BE MAKING THEIR WAY TOWARDS KY ON SUNDAY. THE 12Z GFS HAS COME IN FASTER WITH THIS SYSTEM...AND POINTS TOWARDS RAIN CHANCES FOR THE NORTHERN PART OF THE FORECAST AREA BY LATE SUNDAY AFTERNOON. HOWEVER...HAVE FOLLOWED A MODEL CONSENSUS WHICH WILL KEEP EVEN SLIGHT CHANCES OF RAIN OUT OF THE ENTIRE AREA UNTIL AFTER 6 PM ON SUNDAY. RAIN CHANCES WILL INCREASE FROM NW TO SE SUNDAY NIGHT...WITH RAIN SHOWERS BECOMING LIKELY ALMOST AREA WIDE SUNDAY NIGHT. RAIN CHANCES WILL THEN DECREASE FROM NW TO SE DURING THE DAY MONDAY. AFTER THE SUNDAY NIGHT INTO MONDAY SYSTEM...THE NEXT SHORT WAVE TO AFFECT THE AREA LOOKS TO BE DURING THE MIDDLE TO LATTER PART OF THE WEEK...FOLLOWED BY YET ANOTHER SYSTEM AS WE HEAD TOWARDS NEXT WEEKEND. THERE ARE AGAIN SIGNIFICANT TIMING DIFFERENCES...AND THUS QUESTIONS ON WHEN TO REINTRODUCE RAIN CHANCES BACK IN THE FORECAST. WILL FOLLOW A BLENDED MODEL APPROACH FOR THE MID TO LATE WEEK SYSTEMS...WHICH WILL YIELD SLIGHT RAIN CHANCES MOST AREAS WEDNESDAY...AND THEN CHANCE OR LIKELY PROBABILITIES FOR THURSDAY AND FRIDAY. WITH THE ZONAL FLOW A FAIRLY MILD WEEK WILL BE IN STORE FOR THE AREA...WITH HIGHS IN THE 60S FORECAST FOR TUESDAY THROUGH FRIDAY. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING) ISSUED AT 746 PM EDT FRI MAR 27 2015 MAINLY VFR CONDITIONS ARE EXPECTED OVER THE NEXT 24 TO 36 HOURS. A WEAK WEATHER DISTURBANCE WILL BRING SOME FLURRIES TO THE AREA TONIGHT...BUT CIGS ARE EXPECTED TO REMAIN MAINLY VFR. ITS POSSIBLE A BRIEF PERIOD OF MVFR CIGS COULD DEVELOP...BUT CONFIDENCE IN THIS IS NOT HIGH. STEADY NORTHWEST WINDS WILL CONTINUE OVERNIGHT BEFORE WEAKENING TOMORROW. CLOUDS WILL CLEAR OFF TOMORROW WITH AN EXTENDED PERIOD OF CLEAR SKIES EXPECTED INTO SATURDAY NIGHT. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...KAS SHORT TERM...JMW LONG TERM...SBH AVIATION...KAS

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