Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 201911
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
311 PM EDT SAT SEP 20 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 311 PM EDT SAT SEP 20 2014

HIGH PRESSURE CONTINUES TO HOLD OVER THE EASTERN US THIS
AFTERNOON...PROVIDING A DRY AND MILD START TO THE WEEKEND.
HOWEVER...A POTENT SHORTWAVE TROUGH IS ALREADY DROPPING SOUTH INTO
THE WESTERN GREAT LAKES/NORTHERN PLAINS. MODELS ARE IN FAIRLY GOOD
AGREEMENT ON THE FORECAST THROUGH THE REMAINDER OF THE
WEEKEND...PROVIDING DECENT FORECAST CONFIDENCE.

THE SHORTWAVE TROUGH WILL CONTINUE TO DIVE SOUTHWARD TONIGHT THROUGH
SUNDAY. THIS WILL PUSH A SURFACE COLD FRONT SOUTHWARD INTO THE OHIO
RIVER VALLEY LATE TONIGHT. DECENT CONVERGENCE AND SOME UPPER LEVEL
SUPPORT WILL PRODUCE SHOWERS AND A FEW THUNDERSTORMS AS THIS BOUNDARY
SHIFTS SOUTH TONIGHT. INSTABILITY MAY WANE LATE TONIGHT...WITH
LIMITED THUNDER POTENTIAL. HOWEVER...THE MAIN FRONT IS EXPECTED TO
CROSS THE AREA DURING THE DAY TOMORROW...WITH INSTABILITY INCREASING
ALONG AND JUST AHEAD OF THE BOUNDARY. THIS WILL WARRANT INCREASING
COVERAGE THROUGH THE DAY AS THE FRONT SAGS SOUTHEASTWARD. THE FRONT
WILL BE ON THE EXIT BY EARLY SUNDAY EVENING...WITH SUBSTANTIALLY
DRIER AIR ADVECTING INTO THE AREA FROM EARLY TO LATE EVENING. IF
ENOUGH INSTABILITY CAN DEVELOP SUNDAY AFTERNOON...WE COULD SEE A
MARGINAL WIND THREAT DEVELOP WITH A FEW STORMS. HOWEVER...THIS
REMAINS VERY UNCERTAIN AT THIS TIME.

STAYED ABOVE GUIDANCE FOR LOWS TONIGHT GIVEN THE INCREASING WINDS AND
MOISTURE AHEAD OF THE APPROACHING FRONT. STAYED FAIRLY CLOSE TO
GUIDANCE FOR HIGHS TOMORROW AS CLOUDS AND SHOWERS MAY KEEP
TEMPERATURES FROM GETTING ALL THAT WARM TOMORROW. SHOULD SEE A MUCH
COLDER NIGHT SUNDAY NIGHT WITH THE COLD ADVECTION TAKING PLACE
THROUGH THE NIGHT. WHILE SOME CLEARING MAY BE POSSIBLE...CLOUDS MAY
FILL BACK IN OVERNIGHT AS A SECONDARY TROUGH DROPS SOUTH ACROSS
EASTERN KENTUCKY. THUS...THIS MAY LIMIT FOG POTENTIAL SUNDAY NIGHT.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 311 PM EDT SAT SEP 20 2014

THE MODELS ARE IN GOOD AGREEMENT WITH AN AMPLIFIED LONG WAVE PATTERN
TO AFFECT THE CONUS THROUGH THE PERIOD. AN UPPER LEVEL TROUGH WILL
START OFF MOVING IN ACROSS THE EASTERN CONUS...WITH RIDGING IN THE
PLAINS...AND DEEP TROUGHING IN THE EASTERN PACIFIC. SMALLER SCALE
FEATURES WITHIN THE BROADER FLOW ARE AS USUAL MORE DIFFICULT TO NAIL
DOWN THIS FAR OUT. THE GFS AND ECMWF HAVE SOME DISAGREEMENT WITH
REGARD TO THESE DETAILS...AND THIS DOES AFFECT THE OUTCOME OF THE
LONG WAVE TOWARDS NEXT WEEKEND. THE EASTERN PACIFIC TROUGH WILL SLAM
INTO THE WESTERN CONUS THROUGH THE END OF THE WORK WEEK...HELPING TO
AMPLIFY THE DOWNSTREAM RIDGE...WHICH WILL TAKE UP RESIDENCE ACROSS
THE MAJORITY OF THE MISSISSIPPI VALLEY. THERE WILL BE SOME WEAKNESS
ON THE UPSTREAM AND DOWNSTREAM SIDE OF THIS RIDGE AXIS.

THE MODELS DISAGREE ON THIS POINT...WITH THE ECMWF PUTTING MORE
EMPHASIS ON THE WEAKNESS OF THE RIDGE DOWNSTREAM...WHICH EVENTUALLY
BECOMES A CUTOFF LOW THAT WILL FORM ACROSS THE MID-ATLANTIC
REGION. THE GFS HAS MORE WEAKNESS ESTABLISHED UPSTREAM...WITH
TROUGHING DEVELOPING ACROSS THE PLAINS...KEEPING THE RIDGE MORE
ESTABLISHED IN THE EASTERN CONUS. GIVEN ALL OF THIS UNCERTAINTY...
WILL STICK CLOSE TO THE BLENDED GUIDANCE...ESPECIALLY SINCE THE
RESULTANT SURFACE FEATURES LOOK MORE BENIGN EITHER WAY FOR OUR
REGION FOR NOW.

FOR EASTERN KENTUCKY...VERY PLEASANT WEATHER WILL BE ON TAP FOR THE
PERIOD...AS SURFACE HIGH PRESSURE REMAINS ANCHORED OFF TO THE NORTH
AND NORTHEAST. TEMPERATURES WILL START OUT BELOW NORMAL THROUGH THE
MIDDLE OF NEXT WEEK...WITH HIGHS IN THE LOW TO MID 70S AND LOWS IN
THE 40S. READINGS WILL THEN GRADUALLY MODIFY THROUGH THE REST OF THE
PERIOD...WITH HIGHS NEARING THE 80 DEGREE MARK BY THE START OF THE
WEEKEND. LOWS WILL MAINLY BE IN THE 50S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 231 PM EDT SAT SEP 20 2014

VFR CONDITIONS WILL CONTINUE OVER THE NEXT 24 TO 36 HOURS. SOME
PATCHY VALLEY FOG WILL BE POSSIBLE AGAIN TONIGHT. A COLD FRONT WILL
DROP SOUTH INTO THE AREA TOMORROW MORNING WITH CLOUDS AND
PRECIPITATION CHANCES ON THE INCREASE. AT THIS TIME...IT APPEARS CIGS
SHOULD REMAIN AT OR ABOVE 3500 FEET.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...KAS
LONG TERM...GEOGERIAN
AVIATION...KAS





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