Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 300243 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
1043 PM EDT MON SEP 29 2014

.UPDATE...
ISSUED AT 1043 PM EDT MON SEP 29 2014

DENSE FOG CONTINUES TO LOOK LIKE A GOOD BET TONIGHT FOR AREAS MAINLY
SOUTH OF THE I-64 CORRIDOR...WHERE DEW POINTS REMAIN IN THE UPPER 50S
AND LOWER 60S...AND MANY OBSERVATIONS NEAR AND UPSTREAM REPORTING
WINDS OF 3KTS OR LESS CONTINUING TO AFFIRM WEAK ADVECTION AT BEST.
HAVE GONE AHEAD AND HOISTED A DENSE FOG ADVISORY FOR LATE TONIGHT
INTO EARLY TUESDAY MORNING. WILL ALSO ADJUST SOME OF THE LOW
TEMPERATURES UP A BIT BASED ON THE CURRENT TRENDS IN THE OBSERVATIONS
AND GIVEN THE EXPECTED FOG BLANKET LIKELY TO INHIBIT SOME OF THE
RADIATIONAL COOLING.

UPDATE ISSUED AT 841 PM EDT MON SEP 29 2014

CONVECTION HAS DWINDLED ACROSS EASTERN KENTUCKY WITH THE LOSS OF
HEATING AND AS AN UPPER TROUGH AXIS EXITS OFF TO THE SOUTHEAST. SKIES
ARE CLEARING NICELY ACROSS THE AREA. THERE IS NOTICEABLY DRIER AIR
JUST UPSTREAM...HOWEVER THE ADVECTION IS WEAK. DEW POINTS ARE STILL
IN THE LOWER 60S ACROSS MUCH OF EASTERN KENTUCKY...WITH MID 50S DEW
POINTS WORKING INTO THE I-64 CORRIDOR. GIVEN THESE TRENDS...HAVE
BEEFED UP THE FOG FOR TONIGHT. SO FAR THE LOW TEMPERATURES LOOK
REASONABLE...HOWEVER WE WILL TAKE A BETTER LOOK AT THESE IN THE NEXT
COUPLE OF HOURS.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 352 PM EDT MON SEP 29 2014

THE MODELS WERE IN GOOD AGREEMENT REGARDING THE LARGE SCALE WEATHER
PATTERN AND SENSIBLE WEATHER FOR THE FIRST 36 HOURS OF THE FORECAST.
THE CONSENSUS VIEW IS FOR A WEAK MID LEVEL LOW PRESSURE SYSTEM TO
MOVE OUT OF THE CENTRAL GREAT LAKES REGION TONIGHT AND MOVE ACROSS
THE EASTERN OHIO VALLEY. THE MOST EASTERN KENTUCKY SHOULD SEE FROM
THIS SYSTEM IS SCATTERED LOW AND MIDDLE LEVEL CLOUDS NORTH OF THE
MOUNTAIN PARKWAY THIS EVENING THROUGH THE EARLY OVERNIGHT HOURS. ONCE
THIS INITIAL DISTURBANCE PASSES BY...IT APPEARS LIKELY THAT A FAIRLY
WELL DEVELOPED RIDGE OF HIGH PRESSURE ALOFT WILL SETTLE OVER THE AREA
FOR A FEW DAYS. THIS RIDGE WILL BRING SLIGHTLY ABOVE NORMAL
TEMPERATURES TO THE AREA THROUGH TOMORROW NIGHT...WITH HIGHS TOPPING
OUT IN THE UPPER 70S AND LOWER 80S ON TUESDAY...AND LOWS IN THE 50S
TONIGHT AND TOMORROW NIGHT. WIDESPREAD VALLEY FOG WILL BE ON TAP
AGAIN THE NEXT COUPLE OF NIGHTS AS WELL...PARTICULARLY NEAR RIVERS
AND LAKES. ALL IN ALL THE FOLKS OF EASTERN KENTUCKY CAN EXPECT PARTLY
CLOUDY TO MOSTLY CLEAR SKIES THROUGH TOMORROW NIGHT ALONG WITH LIGHT
WINDS...ABOVE NORMAL TEMPERATURES...AND LATE NIGHT AND EARLY MORNING
FOG.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 352 PM EDT MON SEP 29 2014

SHORTWAVE UPPER LEVEL RIDGING IS EXPECTED TO BE THE DOMINANT WEATHER
FEATURE AT THE START OF THE PERIOD AS IT GRADUALLY SHIFTS FROM AN
AXIS OF THE MID SOUTH TO GREAT LAKES REGION TO THE EASTERN SEABOARD
FROM WEDNESDAY INTO THURSDAY NIGHT. AT THE SAME TIME...AN UPPER
LEVEL LOW/TROUGH WILL GRADUALLY DEPART THE NORTHEASTERN U.S. AND
MOVE ON OFF INTO THE ATLANTIC. AT THE SAME TIME...ANOTHER UPPER
LEVEL RIDGE IS EXPECTED TO SHIFT EAST FROM THE EASTERN PACIFIC INTO
THE WESTERN CONUS. IN BETWEEN...AN UPPER LEVEL TROUGH WILL GRADUALLY
MOVE FROM THE ROCKIES AND PLAINS STATES EAST AND APPROACH THE MS
VALLEY REGION AND UPPER MIDWEST REGION BY THU EVENING. THE RIDGE
ACROSS THE EASTERN SEABOARD SHOULD DEPART INTO THE ATLANTIC TO END
THE WEEK AND OVER THE WEEKEND...WITH UPPER LEVEL RIDGING REMAINING IN
PLACE ACROSS THE WESTERN CONUS. THIS WILL LEAD TO A RATHER DEEP
EARLY FALL TROUGH EXTENDING FROM EASTERN CANADA SOUTH INTO MUCH OF
THE CENTRAL AND EASTERN CONUS. AS THE UPPER TROUGH BEGINS TO MOVE
INTO THE EASTERN CONUS...THE ASSOCIATED SFC COLD FRONT WILL APPROACH
EASTERN KY ON THU NIGHT AND CROSS THE AREA ON FRIDAY. A SECONDARY
SFC TROUGH/COLD FRONT SHOULD MOVE ACROSS THE REGION ON SATURDAY INTO
SATURDAY EVENING AND USHER IN POSSIBLY THE COLDEST AIR MASS SO FAR
THIS FALL. MODELS ALSO BRING ANOTHER SHORTWAVE THROUGH THE TROUGH IN
NW FLOW LATE IN THE PERIOD.

THE DEPARTING UPPER LEVEL AND ASSOCIATED SFC HIGH WILL BRING MILD...
ABOVE NORMAL TEMPERATURES FOR WED INTO THU. TEMPERATURES SHOULD
REACH THE LOW...TO PERHAPS MID 80S IN SEVERAL LOCATIONS BOTH DAYS.
ACROSS THE SOUTHEAST PART OF THE CWA...A NON IDEAL DOWNSLOPING
COMPONENT TO THE WIND SHOULD LEAD TO SOME OF THE HIGHER READINGS IN
VALLEYS IMMEDIATELY DOWNWIND OF THE VA BORDER AT LOCATIONS SUCH AS
HARLAN...CUMBERLAND...WHITESBURG...JENKINS...AND ELKHORN CITY. THE
PATTERN FAVORS A MEDIUM TO LARGE RIDGE/VALLEY SPLIT ON WED NIGHT AS
WELL. SOME GUSTY WINDS ARE POSSIBLE ACROSS THE MOUNTAINS AS A RATHER
SHARP COLD FRONT APPROACHES ON THU NIGHT.

RETURN FLOW AHEAD OF THE BOUNDARY AND THE APPROACHING TROUGH SHOULD
BRING A BRIEF PERIOD OF RATHER DEEP MOISTURE TO THE REGION FROM LATE
THURSDAY NIGHT INTO EARLY ON FRIDAY. IN ADDITION...A SHORTWAVE
MOVING ACROSS THE ROCKIES AND PLAINS STATES EARLY IN THE PERIOD WILL
MOVE INTO THE TN AND OH VALLEY REGION ON TUE NIGHT AND BEGIN TO TAKE
ON A NEGATIVE TILT...LEADING TO BETTER FORCING AND CONFIDENCE IN
MEASURABLE PRECIP ACROSS THE REGION WITH THIS EVENT. THE ECMWF
REMAINS A BIT FASTER BRINGING THE SHORTWAVE TROUGH AND FRONT ACROSS
THE REGION LATE THU NIGHT AND FRIDAY. ELEVATED INSTABILITY SHOULD BE
SUFFICIENT FOR SOME ISOLATED THUNDER LATE THU NIGHT...DESPITE THE
RATHER UNFAVORABLE TIMING OF THIS TIME OF YEAR...WITH SUFFICIENT
INSTABILITY LINGER INTO FRI MORNING FOR A CONTINUED CHANCE OF
ISOLATED TO SCATTERED THUNDER. BEHIND THE BOUNDARY FROM MIDDAY FRI
TO FRI EVENING...WINDS COULD ALSO BE GUSTY...BUT THE GFS RUNS ARE A
BIT STRONGER WITH WINDS ALOFT AND MOMENTUM MIX DOWN POTENTIAL
COMPARED TO THE ECMWF RUNS. LIKELY POPS RESULTED FROM THE MODEL
BLEND...WITH THIS LIKELY BECOMING A CATEGORICAL EVENT AT SOME POINT
AS THE EVENT APPROACHES.

THERE ARE MODEL DIFFERENCES WITH THE MAIN TROUGH AS IT APPROACHES
MOVES ACROSS THE GREAT LAKES AND OHIO VALLEY FROM FRIDAY INTO
SATURDAY NIGHT...WITH RECENT ECMWF RUNS SLOWER AND DEEPER/LOWER WITH
HEIGHTS ACROSS THE GREAT LAKES AND OH VALLEY FROM FRI NIGHT INTO
SATURDAY NIGHT AND COLDER WITH THE AIR MASS BY AT LEAST 3 TO 5
DEGREES C FROM LATE FRI NIGHT INTO EARLY ON SUNDAY. THIS LEADS TO
THE DISPARITY IN GUIDANCE MAX T FOR SAT INTO SUNDAY OF AT LEAST 8 TO
13 DEGREES FROM COLDEST TO WARMEST AND MIN T DIFFERENCES ON THE
ORDER OF 5 DEGREES OR MORE. OVERNIGHT MINS...ESPECIALLY SAT NIGHT
MAY LARGELY DEPEND ON THE DEGREES OF CLEARING OR THE PRESENCE OF ANY
LOW AND MID CLOUDS AS SEVERAL WEAKER SHORTWAVES MOVE THROUGH THE
TROUGH. A STRONGER WAVE ON SUN NIGHT INTO MONDAY SHOULD BRING AT
LEAST MORE CLOUD COVER IF NOT THE CHANCE FOR SOME RAIN SHOWERS.
THE COLDER ECMWF SOLUTIONS WOULD SUPPORT MORE CLOUD COVER SAT
NIGHT...WHILE THE WARMER GFS IS ALSO MORE MOIST...SO CONFIDENCE IN
MIN T IS NOT HIGH. WITH CLOUD COVER ANTICIPATED...MIN T MAY BE MORE
ELEVATION/COLD AIR ADVECTION DEPENDENT...BARRING ANY SIGNIFICANT
CLEARING...THUS RIDGETOPS AND THE HIGHEST TERRAIN COULD END UP BEING
THE COLDEST ON SAT NIGHT AND SUN NIGHT.

GIVEN THAT THE MODELS CONTINUE TO HAVE A THEME OF THE GFS WARMER AND
THE ECMWF MUCH COLDER FROM SAT THROUGH THE END OF THE PERIOD...THE
MODEL BLEND SEEMED TO BE THE BEST COURSE OF ACTION AT THIS TIME. THE
BOTTOM LINE IS THE PERIOD BEGINS MILD AND THEN ENDS WITH BELOW
NORMAL TEMPERATURES.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 841 PM EDT MON SEP 29 2014

CLEARING SKIES AND NEARLY CALM WINDS WILL LIKELY RESULT IN AREAS OF
DENSE FOG ACROSS EASTERN KENTUCKY. HAVE ALLOWED FOR LIFR OR WORSE
CONDITIONS BUILDING IN AT ALL TAF SITES BETWEEN 06 AND 12Z. ONCE THE
FOG BURNS OFF BETWEEN 13 AND 14Z...VFR CONDITIONS WILL RETURN. WINDS
WILL REMAIN LIGHT THROUGH THE PERIOD AS WELL.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 10 AM EDT TUESDAY FOR KYZ058>060-068-
069-079-080-083>088-106>120.

&&

$$

UPDATE...GEOGERIAN
SHORT TERM...AR
LONG TERM...JP
AVIATION...GEOGERIAN





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