FXUS63 KJKL 290534
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
1234 AM EST SUN NOV 29 2009
.SHORT TERM.../THE REST OF TONIGHT/
HIGH PRESSURE IS GRADUALLY EXITING TO THE EAST...WITH A COLD FRONT
STARTING TO APPROACH THE REGION FROM THE WEST. CURRENT WV AND IR
IMAGERY REVEALS ONLY VERY THIN CIRRUS OR NO CIRRUS AS ALL ACROSS THE
SOUTHERN CWA BORDER WITH TN...WITH CLOUDS ASSOCIATED WITH A MID LEVEL
SHORTWAVE ACROSS THE GULF COAST REGION GENERALLY REMAINING SOUTH OF
THE CWA. A FEW CIRRUS IN ADVANCE OF THE COLD FRONT AND THE ASSOCIATED
SHORTWAVE HAVE REACHED AS CENTRAL KY...BUT THESE APPEAR THIN AND
PATCHY. A FEW MID LEVEL CLOUDS IN ADVANCE OF THE FRONT ARE OVER IL
AND IN. OBSERVATIONS AS OF 9 PM FROM VALLEY KY MESONET SITES...COOP
AND AWOS SITES INDICATE THAT SEVERAL VALLEY LOCATIONS ARE ALREADY IN
THE MID AND UPPER 30S...WITH DEWPOINTS IN THE LOW TO MID 30S.
TEMPERATURES ON NEARBY RIDGES REMAIN IN THE 50S OR NEAR 50
THOUGH...WITH VARYING TEMPERATURES IN THE MORE OPEN TERRAIN
LOCATIONS BORDERING THE BLUEGRASS AND ALONG AND WEST OF THE
INTERSTATE 75 CORRIDOR.
SINCE CURRENT TEMPERATURES IN THE MORE EASTERN VALLEY LOCATIONS ARE
APPROACHING THE PREVIOUSLY FORECAST TEMPERATURES...OPTED TO LOWER
THE RANGE FOR THOSE VALLEY LOCATIONS. 18Z COOP MOS DID NOT GO AS LOW
AS FORECAST FOR JKL SITES...BUT MOS DATA FROM TRI AND NORMALLY
COLDER NEARBY LOCATIONS IN NE KY AND SW VA INDICATE THAT A FEW UPPER
20S ARE POSSIBLE AND THIS WAS REASONABLE GIVEN THE CURRENT TRENDS.
ALTHOUGH THE PRESS GRADIENT WILL STRAIGHTEN A BIT OVERNIGHT AS THE
FRONT APPROACHES...WITH ALREADY DECOUPLED VALLEYS...IT IS DOUBTFUL
THAT ANY VALLEYS OTHER THAN SW TO NE ORIENTED ONES WILL MIX OUT. OPTED
TO GO WITH 28 TO 33 IN THE EASTERN VALLEYS (ESPECIALLY THE BIG SANDY
REGION) AND THEN PROGRESSIVELY SLIGHTLY WARMER FOR VALLEYS TO THE
WEST WHERE WINDS MAY HAVE A BETTER CHANCE OF MIXING OUT THE VALLEYS A
COUPLE OF HOURS PRIOR TO DAWN. EVEN THE EASTERN VALLEYS MAY EXPERIENCE
A LEVELING OUT OF TEMPERATURES BY 9Z. TIMEHEIGHT SECTIONS GENERALLY
INDICATE ONLY A CHANCE OF CIRRUS PRIOR TO 12Z AND THIS IS CONSISTENT
WITH SAT TRENDS. UPDATED ZPF AND GRIDS ARE ALREADY OUT FOR SLIGHT
DECREASES TO VALLEY WINDS...VALLEY MIN T AND SKY COVER.
THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS...
/TONIGHT THROUGH MONDAY NIGHT/
HIGH PRESSURE TO BRING QUIET WEATHER TONIGHT AND SUNDAY...BEFORE A
SHORTWAVE TO THE NORTH AND A COLD FRONT COMBINE WITH MOISTURE FROM
THE SOUTH TO BRING RAIN SHOWERS TO THE AREA SUNDAY NIGHT AND MONDAY.
TONIGHT WILL SEE A RIDGE/VALLEY TEMPERATURE SPLIT WITH CLOUDS ON THE
INCREASE TOWARD MORNING. SOUTHWESTERLY FLOW WILL BRING WARMER AIR
INTO THE REGION TOMORROW RESULTING IN HIGH TEMPERATURES FOR MANY
PLACES CLIMBING INTO THE LOWER 60S. PRECIPITATION SHOULD SLOWLY
SPREAD WEST TO EAST FROM MID AFTERNOON ON AND CONTINUE THROUGH THE
OVERNIGHT HOURS INTO THE EARLY HOURS OF MONDAY. PRECIPITATION FAIRLY
PROGRESSIVE SO RAINFALL TOTALS SHOULD END UP ON THE 0.25-0.50 INCHES
RANGE WITH A FEW LOCALLY HIGHER AMOUNTS POSSIBLE. MONDAY AFTERNOON
WILL BE COOL...WITH HIGHS JUST A FEW DEGREES OVER SUNDAY NIGHT LOWS
IN NORTHWESTERLY FLOW ALOFT BEHIND THE COLD FRONT. HIGH PRESSURE
BUILDING IN QUICKLY SHOULD MAKE FOR DECREASING CLOUDS AND COLDER
TEMPERATURES ON MONDAY NIGHT.
.LONG TERM.../TUESDAY THROUGH SATURDAY/
EAST KENTUCKY FINDS ITSELF BETWEEN WEATHER MAKING SYSTEMS AT THE
START OF THE FORECAST PERIOD AS EAST CONUS TROUGH SLIDES OFF TO THE
EASTERN COAST AND CLOSED LOW OVER THE SOUTHWEST BEGINS TO EJECT
EASTWARD. THIS EASTWARD EJECTION WILL BE IN RESPONSE TO RAMPED UP
100-110 KNOT SUBTROPICAL JET CORE TRAVERSING THE SOUTH CONUS.
MEANWHILE...THE POLAR JET BEGINS TO CARVE OUT ANOTHER TROUGH OVER
THE NORTHERN PLAINS...DRAGGING A TRULY POLAR AIR MASS WITH IT.
DIFFERENT DEGREES OF PHASING...STILL NOT CLEAR BETWEEN POLAR AND
SUBTROPICAL JET...SHOULD DEVELOP AND INTENSIFY A SURFACE LOW
SOMEWHERE AROUND THE WESTERN GULF COAST. THIS LOW WILL THEN RIDE TO
THE NORTHEAST TOWARD EAST KENTUCKY THEN UP THROUGH NEW ENGLAND BY
THURSDAY NIGHT. THE SYSTEM SWINGS A POWERFUL COLD FRONT THROUGH THE
AREA WEDNESDAY NIGHT BRINGING THE POLAR AIR MASS WITH IT.
THE RESULTANT SENSIBLE WEATHER WILL BE CHARACTERIZED BY INCREASING
CHANCES FOR PRECIPITATION...MOSTLY IN THE FORM OF RAIN...FROM SOUTH
TO NORTH ON WEDNESDAY AFTERNOON LASTING THROUGH THURSDAY. ISENTROPIC
LIFT OVER A WARM FRONT...WITH THE AID OF THE LEFT EXIT REGION OF A
100 KNOT H3 JET WILL HELP TO ENHANCE RAINFALL ON WEDNESDAY. HAVE
INCLUDED A PERIOD OF LIKELY POPS LATE WEDNESDAY INTO WEDNESDAY
EVENING AS SURFACE LOW TRAVERSES THE REGION. THERE IS...AND WILL BE
...CONTINUED MODEL DISAGREEMENT ON WHERE THE SURFACE LOW ACTUALLY
TRACKS. THIS FINAL TRACK OF THE LOW WILL BE KEY TO EXACTLY WHERE AND
WHEN A CHANGE OVER TO RAIN AND SNOW SHOWERS BEGINS. AT THIS POINT IT
LOOKS AS THOUGH WEDNESDAY NIGHT WILL SEE THE BEST CHANCE FOR SOME
SNOW SHOWERS WITH SOME LINGERING CHANCES INTO THURSDAY AFTERNOON. DO
NOT EXPECT ANY ACCUMULATION AT THIS POINT. OVERALL...MODELS HAVE
COME INTO BETTER AGREEMENT ON THE EVOLUTION OF THIS SYSTEM WITH
GENERAL AGREEMENT FROM ECMWF/GFS/CMC. HOWEVER INDIVIDUAL DETAILS DO
EXIST AND THE COLDEST GFS SOLUTION WOULD SUGGEST A LONGER PERIOD OF
SNOW WITH SOME POSSIBLE ACCUMULATION. THE WARMER ECMWF SOLUTION
SUGGESTS ONLY A BRIEF CHANGEOVER TO SNOW WITH MOSTLY FLURRIES AT THE
END. HAVE CONTINUED TO GO MIDDLE OF THE ROAD UNTIL EVENT NEARS. ONE
OTHER ITEM OF NOTE IS THAT A PERIOD OF FAIRLY STRONG DOWNSLOPE FLOW
OVER THE SOUTHEAST TERRAIN SHOULD LIMIT PRECIP HITTING THE GROUND ON
WEDNESDAY AND WEDNESDAY EVENING IN THE SOUTHEAST TERRAIN. HAVE
CONTINUED TO DEPICT THIS IN THE GRIDS.
AS FAR AS TEMPERATURES ARE CONCERNED...TUESDAY SHOULD BE A PLEASANT
DAY UNDER PARTLY CLOUDY TO MOSTLY SUNNY SKIES AND HIGHS RIGHT AROUND
50 DEGREES. TUESDAY NIGHT SHOULD GENERALLY BE IN THE MID 30S FOR
LOWS WITH A SUBTLE SPLIT BETWEEN RIDGES AND VALLEYS. WITH THE
APPROACH OF THE SYSTEM ON WEDNESDAY...TEMPERATURES SHOULD STRUGGLE A
BIT UNDER AMPLE CLOUD COVER AND INCREASING RAIN COVERAGE. AT THIS
POINT HIGHS IN THE UPPER 40S SEEM REASONABLE. THE SYSTEM DRAGS THE
POWERFUL COLD FRONT THROUGH ON WEDNESDAY NIGHT WITH GRADUALLY
FALLING TEMPERATURES IN THE LOW TO MID 30S. WILL SEE LITTLE IN THE
WAY OF RECOVERY ON THURSDAY AS STRONG COLD AIR ADVECTION COMBINES
WITH CONTINUED HEAVY SKY COVER. SURFACE HIGH PRESSURE BUILDS INTO
THE AREA OVER THE WEEKEND HIGHS IN THE LOWER 40S AND LOWS IN THE IN
THE UPPER 20S TO AROUND 30 DEGREES. ONCE AGAIN...IT IS IMPORTANT TO
UNDERSTAND THAT THESE TEMPERATURES ARE BASED ON A COMPROMISE BETWEEN
MODEL SURFACE LOW TRACKS. CHANGES IN THIS TRACK WILL HAVE A
SIGNIFICANT IMPACT ON TEMPERATURES AND COULD RESULT IN MORE OR LESS
SNOWFALL.
&&
.AVIATION.../06Z TO 06Z/...UPDATED
HIGH PRESSURE WILL CONTINUE TO BRING MOSTLY CLEAR SKIES TO THE TAF
SITES THROUGH 15Z TODAY. BETWEEN 15 AND 18Z...A SCATTERED LAYER OF
MIDDLE LEVEL CLOUDS WILL BEGIN TO MOVE INTO LOZ AND SME BENEATH A
BROKEN LAYER OF CIRRUS. AROUND 18Z A BROKEN LAYER OF MIDDLE LEVELS
WILL BE MOVING ACROSS ALL THREE TAF SITES. THE CLOUDS WILL CONTINUE
TO LOWER AND THICKEN WITH VFR CIGS OF 6K AT JKL...5K AT LOZ AND 4.5K
AT SME EXPECTED BY 23Z. NO PRECIPITATION IS EXPECTED TO AFFECT ANY OF
THE TAF SITES THROUGH 6Z MONDAY.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...MACZKO/JP
LONG TERM....SCHOETTMER
AVIATION...AR
