Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 181725 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 125 PM EDT SAT APR 18 2015 .UPDATE...
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ISSUED AT 125 PM EDT SAT APR 18 2015 NO MAJOR UPDATES TO THE FORECAST WERE NECESSARY THIS AFTERNOON. THE LATEST OBS DATA WAS INGESTED INTO THE FORECAST GRIDS TO ESTABLISH NEW TRENDS...BUT NOTHING MORE THAN THAT WAS REQUIRED AS THE FORECAST IS IN GOOD SHAPE. UPDATE ISSUED AT 1018 AM EDT SAT APR 18 2015 JUST UPDATED THE FORECAST GRIDS...ZONE FORECAST TEXT PRODUCT...AND HAZARDOUS WEATHER OUTLOOK TO REMOVE MENTION OF FOG. ALSO REMOVED ANY OUTDATED WORDING FROM THE ZONES. THE FORECAST IS OTHERWISE ON TRACK WITH NO OTHER CHANGES NEEDED. UPDATE ISSUED AT 800 AM EDT SAT APR 18 2015 HOURLY GRIDS HAVE BEEN UPDATED BASED ON RECENT OBSERVATIONS. NO MAJOR CHANGES WERE NEEDED AT THIS TIME. THE FOG IS STILL EXPECTED TO LIFT AND DISSIPATE AROUND 9 AM EDT.
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&& .SHORT TERM...(TODAY THROUGH SUNDAY) ISSUED AT 345 AM EDT SAT APR 18 2015 SHORTWAVE UPPER LEVEL RIDGING AND RIDGING EXTENDING DOWN TO NEAR THE SFC WAS THE DOMINANT FEATURE ACROSS THE LOWER OH VALLEY AND INTO THE CENTRAL APPALACHIAN REGION. WITH MAINLY JUST CIRRUS OVERHEAD...TEMPERATURES IN THE VALLEY LOCATIONS HAVE DROPPED OFF WELL INTO THE 50S. VALLEY FOG HAS BEGUN TO DEVELOP...ACROSS THE CUMBERLAND VALLEY PER SME AND EKQ OBS. IN OTHER LOCATIONS...RH FROM KY MESONET SITES AND THE SLOWING RATE OF TEMPERATURE DROP AS WELL AS IOB OBSERVATION POINT TOWARD VALLEY FOG ELSEWHERE AS WELL. THIS VALLEY FOG SHOULD CONTINUE TO DEVELOP OVER THE NEXT COUPLE OF HOURS. UPSTREAM OF THE REGION A CLOSED LOW CONTINUED TO SPIN OVER THE SOUTHERN CO/NORTHER NW REGION WITH MOISTURE STREAMING NORTH ACROSS MUCH OF THE SOUTHERN PLAINS INTO THE CENTRAL PLAINS REGION...ESPECIALLY FROM EAST TX NORTH INTO KS AND MO. THROUGH THE SHORT TERM PERIOD...THE CLOSED LOW IS EXPECTED TO MOVE EAST INTO THE CENTRAL PLAINS AND APPROACH THE MID MS VALLEY REGION. AS IT DOES SO...IT WILL BEGIN TO MERGE WITH A NORTHERN STREAM SYSTEM DROPPING SOUTHEAST. THIS NORTHERN STREAM SYSTEM WILL BE NEARING NW ONTARIO BY THE END OF THE PERIOD. WEAK SHORTWAVES IN THE SOUTH TO SOUTHWEST FLOW ALOFT SHOULD MOVE ACROSS THE TN AND OH VALLEY REGION FROM TONIGHT THROUGH THE END OF THE PERIOD. THE MOST SIGNIFICANT ONE HOWEVER...WILL ROTATE INTO THE REGION LATER TONIGHT AND INTO THE DAY ON SUNDAY. AT THE SAME TIME...SOMEWHAT COMPLEX AND BAGGY SFC LOW PRESSURE IS EXPECTED TO DEVELOP OVER THE LOWER MS VALLEY REGION BY THIS EVENING AND THEN TRACK NEARLY DUE NORTH TO NEAR THE CONFLUENCE OF THE OH AND MS RIVERS BY DAWN ON SUNDAY. THE SFC LOW SHOULD THEN TRACK NORTHER NORTH TO JUST SOUTH OR SOUTHEAST OF LAKE MICHIGAN BY THE END OF THE PERIOD. AS THE LOW TRACKS NORTH IT WILL SEND A WARM FRONT NORTH INTO EASTERN KY ON SUNDAY. LATE IN THE PERIOD...THE SW CORNER OF THE CWA MAY BE IN THE WARM SECTOR BETWEEN THE WARM FRONT AND A COLD FRONT NEARING THE MS VALLEY. THIS SYSTEM WILL TRANSPORT DECENT MOISTURE NORTH INTO THE REGION AND WITH SOME MID LEVEL SUPPORT AS WELL AS ISENTROPIC LIFT...MEASURABLE RAIN IS ANTICIPATED AREA WIDE... ESPECIALLY ON SUNDAY. THUNDERSTORMS AREA ALSO POSSIBLE... ESPECIALLY FROM LATE TONIGHT AND INTO THE DAY ON SUNDAY. IF DESTABILIZATION CAN OCCUR...ESPECIALLY ACROSS THE SOUTH OR SOUTHWEST...A STRONGER STORM OR TWO CANNOT BE RULED OUT. AS FOR THE NEAR TERM...THE VALLEY FOG SHOULD LIFT AND DISSIPATE BY ABOUT 14Z...OR 10 AM. THEN SUNSHINE THROUGH SOME HIGH CLOUDS IS ANTICIPATED. TEMPERATURES SHOULD WARM WELL INTO THE 70S AND REACH OR EXCEED 80 IN SEVERAL LOCATIONS. MOISTURE MAY INCREASE JUST ENOUGH NEAR THE TN BORDER EAST TO RIGHT ALONG THE VA BORDER WHERE MODELS INDICATE A SUBTLE CONVERGENCE ZONE FOR A STRAY SHOWER OR TWO LATE THIS AFTERNOON OR EVENING. THE CONSENSUS OF THE SHORT TERM AND HIGHER RESOLUTION MODELS SUCH AS THE NAM...HRRR AND THE RAP POINT TOWARD THIS POTENTIAL. HOWEVER...THE BULK OF THE SHOWERS SHOULD HOLD OFF UNTIL AFTER DARK...AND IN FACT AFTER MIDNIGHT OR LATER IN MOST LOCATIONS. INSTABILITY MAY INCREASE ENOUGH FOR A FEW EMBEDDED RUMBLES OF THUNDER ACROSS THE SOUTHWEST OVERNIGHT. THE PRESSURE GRADIENT WILL ALSO BE INCREASING AS THE NIGHT PROGRESSES AND INTO THE DAY ON SUNDAY. THIS SHOULD LEAD TO THE HIGHER ELEVATION EXPOSED LOCATIONS SUCH AS THE TOP OF BLACK MTN AND THE VALIDATES AREA OF PIKE COUNTY PICKING UP SUSTAINED WINDS OF 15 TO 20 MPH AFTER MIDNIGHT ON SUNDAY TOWARD DAWN. SOME GUSTS THERE IN THE 30 TO 40 MPH RANGE ARE CERTAINLY POSSIBLE. THE SOUTHEAST FLOW PATTERN WILL NEED TO BE WATCHED FOR POSSIBLE MTN WAVE GUSTS INTO HARLAN AND LETCHER COUNTIES JUST DOWNWIND OF BLACK AND PINE MOUNTAINS. THE FORECAST SOUNDINGS FROM THE NAM SEEM TO SHOW MIXING FOR SEVERAL THOUSAND FEET ABOVE THE TOP OF THE BLACK MTN AND HIGH KNOB REGION WHILE THE GFS SOUNDINGS HAVE THE TOP OF THE INVERSION NEAR 850 MB...SO THIS LEADS TO UNCERTAINTY IN ANY POSSIBLE MTN WAVE DEVELOPMENT LATE ON SAT NIGHT NEAR THE VA BORDER. OTHERWISE...A BAND OF SHOWERS IN ADVANCE OF THE WARM FRONT SHOULD LIFT NORTHEAST...WITH THE BULK OF THE SOUTHWEST PART OF THE CWA STANDING THE BEST CHANCE FOR MEASURABLE RAIN BEFORE DAWN ON SUNDAY. THE REMAINDER OF THE AREA SHOULD RECEIVE SHOWERS AND SOME EMBEDDED THUNDER FROM SUNDAY MORNING THROUGH MID AFTERNOON ON SUNDAY. AS ALREADY MENTIONED...SOME REDEVELOPMENT WOULD BE POSSIBLE MAINLY ACROSS THE SOUTHWEST LATE IN THE DAY. A STRONG STORM OR TWO CANNOT BE RULED OUT IN THAT AREA WITH STRONG WIND GUSTS AND POSSIBLY MARGINALLY SEVERE HAIL. SPC HAS HIGHLIGHTED THIS REGION FOR A MARGINAL RISK OF SEVERE THUNDERSTORMS WITH PROBABILITIES MUCH HIGHER FROM THE MID MS VALLEY SOUTH TO THE GULF COAST REGION. .LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY) ISSUED AT 315 AM EDT SAT APR 18 2015 FIRST ROUND OF SHOWERS AND THUNDERSTORMS WILL BE MOVING EAST OF THE REGION TO START THE PERIOD. A LULL IN THE PRECIP WILL BE POSSIBLE OVERNIGHT SUNDAY AS ANOTHER LOW PRESSURE DEVELOPS ACROSS THE MIDWEST. THIS WILL BE PRIMARILY DUE TO ANOTHER SPOKE OF ENERGY ROUNDING THE BASE OF A NORTHERN STREAM UPPER LEVEL CLOSED LOW. THIS WILL SWING A COLD FRONT ACROSS THE REGION MONDAY WITH INCREASED CHANCES OF SHOWERS AND THUNDERSTORMS ESPECIALLY IN THE AFTERNOON. THE MODEL SOUNDINGS ARE MEAGER WITH THE QPF AND MOISTURE IS SHALLOW WITH PWATS AROUND AOA 0.80 DURING THE DAY ON MONDAY. THEREFORE KEEP QPF AROUND A QUARTER OF A INCH IN THE AFTERNOON. MODELS ARE IN GOOD AGREEMENT WITH THE SETUP AND PROGRESSION OF THIS SYSTEM THIS FRONT WILL USHER IN COOLER AND DRIER AIR AS WE MOVE INTO THE EARLY PART OF NEXT WEEK. HIGH TEMPERATURES WILL TOP OUT IN THE LOWER 60S BY TUESDAY AND LOWS IN THE LOWER 40S AT TIMES. MODELS ARE A BIT MORE DIVERGENT AS WE MOVE INTO THE LONGER RANGE PORTION OF THE FORECAST. THE GFS WANTS TO BRING A WEAK WAVE ACROSS THE REGION AS WE MOVE INTO EARLY WEDNESDAY...WHILE THE ECMWF AND GEM ARE A BIT DRIER. THERE SEEMS TO ALSO BE A WEAKER FRONT DURING THIS PERIOD AS WELL...HOWEVER GIVEN THAT THE QPF IS QUITE LOW WILL LEAN TOWARD THE SLIGHT POPS GIVEN IN THE BLEND. THESE POPS PERSIST INTO THURSDAY AT THIS POINT AND THIS SEEMS REASONABLE GIVEN THE UNCERTAINTY ASSOCIATED WITH THE GUIDANCE IN THIS PERIOD. THEN WE TURN OUR EYES TO A MORE SUBSTANTIAL SYSTEM AS WE MOVE INTO FRIDAY TIME FRAME. THIS IS ASSOCIATED WITH A SHORTWAVE EJECTING OUT OF THE DESERT SOUTHWEST FRIDAY. DIFFLUENCE ALOFT WILL AID IN SPREADING OVERRUNNING PRECIP EAST INTO THE REGION LATE FRIDAY. THE GFS IS THE MOST PROGRESSIVE...BUT BOTH MODELS THE GFS AND ECMWF AT LEAST HAVE THE GENERAL SETUP AS WE MOVE INTO LATE NEXT WEEK. THIS DEVELOPING SYSTEM IS ALSO CORROBORATED BY THE 00Z GFS ENSEMBLE MEAN...WITH DECENT CONTINUITY BETWEEN THE OPERATIONAL RUN. RIGHT NOW WILL KEEP POPS IN THE SLIGHT TO CHANCE RANGE ON FRIDAY AS MOST THE BETTER DYNAMICS COME INTO PLAY AS WE MOVE INTO FRIDAY NIGHT AND SATURDAY WHICH ARE BEYOND THE SCOPE OF THIS FORECAST PERIOD. && .AVIATION...
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(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON) ISSUED AT 125 PM EDT SAT APR 18 2015 NOT TOO MUCH WILL BE GOING ON AT THE AIRPORTS UNTIL EARLY TONIGHT. BROKEN TO OVERCAST LAYER OF HIGH CIRRUS...WITH A FEW CUMULUS SCUD DRIFTING PAST BENEATH...WILL BE ALL THERE IS TO SPEAK OFF IN THE TAFS FOR NOW. THE FIRST MVFR CONDITIONS ARE NOT EXPECTED UNTIL BETWEEN 6 AND 7Z...WHEN SCATTERED RAIN SHOWERS...AND PERHAPS A FEW THUNDERSTORMS...BEGIN MOVING INTO THE AREA. THE RAIN COULD BECOME HEAVY AT TIMES AFTER 11Z...WITH PERHAPS A FEW STRONG STORMS POSSIBLE DURING THE DAY ON SUNDAY. CONDITIONS COULD WORSEN DRAMATICALLY DURING ANY THUNDERSTORMS...WITH IFR OR EVEN LIFR CONDITIONS POSSIBLE FOR BRIEF PERIODS.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...JP LONG TERM...DJ AVIATION...AR

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