FXUS63 KJKL 300525
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
1225 AM EST MON NOV 30 2009
.SHORT TERM.../THE REST OF TONIGHT AND MONDAY/
A LINE OF SHOWERS IN ADVANCE OF A SHORTWAVE TROUGH AND ITS ASSOCIATED
COLD FRONT IS APPROACHING THE REGION FROM THE WEST AND NORTHWEST...WITH
SHOWERS ALREADY HAVING MOVED INTO THE BLUEGRASS COUNTIES. A WSW LLJ
IS ALSO TRANSPORTING ADDITIONAL MOISTURE INTO THE REGION AND RECENT
SHOWER DEVELOPMENT OVER WESTERN TN AND WESTERN KY WOULD SEEM TO
INDICATE THAT ISENTROPIC LIFT PROGGED BY BOTH THE NAM AND GFS IS
OCCURRING. ISENTROPIC LIFT FROM THE NAM ON THE 290K SFC IS BEST IN
THE WEST STARTING NOW AND RUNNING THROUGH 6Z OR 7Z IN THE WEST AND AS
LATE AS 9Z NEAR THE VA BORDER. IN ADDITION...THE CONVERGENCE ALONG
THE FRONT AND THE APPROACHING SHORTWAVE TROUGH SHOULD BRING
RELATIVELY DEEP LIFT...WITH A POSSIBLE BRIEF RIGHT ENTRANCE REGION OF
THE JET ENHANCEMENT AROUND 12Z ALSO POSSIBLE. SINCE THE LOWER LEVELS
ARE DRY AND WILL CONTINUE TO SLOWLY MOISTEN UP FROM THE TOP DOWN...
ESPECIALLY IN THE SOUTHWEST...TOTAL QPF THROUGH THE DAYTIME ON
MONDAY OF AROUND TWO TO THREE TENTHS...WITH PERHAPS A TENTH OR SO
MORE ACROSS THE HIGH TERRAIN ALONG THE VA BORDER APPEAR VERY
REASONABLE.
THE MAIN UPDATES WERE TO ADJUST THE HOURLY POPS BASED ON RECENT RADAR
IMAGERY AND FRESHEN UP THE HOURLY TEMPERATURE AND DEWPOINT CURVES
FROM RECENT OBSERVATIONS. OTHERWISE...THE CAT POPS APPEAR REASONABLE
GIVEN THE RECENT TRENDS. TEMPERATURES SHOULD RISE VERY LITTLE ON MON
AND COULD EVEN FALL A COUPLE OF DEGREES IN THE AFTERNOON WITH COLD
AIR ADVECTION REALLY KICKING IN...ESPECIALLY ALOFT.
THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS...
/TONIGHT THROUGH TUESDAY/
FORECAST IS PRETTY STRAIGHT FORWARD THIS CYCLE. MODELS ARE IN VERY
GOOD AGREEMENT THROUGH THE SHORT TERM PERIOD. A WELL DEFINED UPPER
LEVEL TROUGH AND ASSOCIATED COLD FRONTAL BOUNDARY WILL MOVE OUT OF
THE MID WEST AND THROUGH EASTERN KENTUCKY BY EARLY MONDAY. REGIONAL
RADAR MOSAIC IS SHOWING CONSIDERABLE SHOWER ACTIVITY BEING GENERATED
WITH THIS FEATURE...IN LINE WITH ADVERTISED MODEL SOLUTIONS. WITH
GOOD AGREEMENT...AND INITIALIZATION CONFIDENCE WAS HIGH ENOUGH TO
INCREASE POPS FOR LATE TONIGHT INTO EARLY MORNING MORNING.
THEREAFTER...SHORT WAVE RIDGING DEVELOPS...AND TRANSITS THE AREA FOR
THE LATTER PORTION OF THE PERIOD. THIS AND SFC HIGH PRESSURE WILL
KEEP OUR WEATHER DRY AND SEASONABLY COOL THROUGH TUESDAY.
.LONG TERM.../TUESDAY NIGHT THROUGH SUNDAY/
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 AIRMASS 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 AIRMASS 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
MID AND LOW CLOUDS HAVE MOVED INTO THE AREA IN ADVANCE OF A COLD
FRONT. SHOWERS HAVE BEEN OBSERVED ON RADAR FROM AROUND BIG SANDY TO
SOMERSET. CIGS HAVE LOWERED TO MVFR CIGS AT ALL TAF SITES AND WILL
CONTINUE TO LOWER WITH TIME...ESPECIALLY ONCE THE FRONT GETS CLOSER.
COLD FRONT CURRENTLY ANALYZED FROM JUST WEST OF CMH/SDF/BWG. THE COLD
FRONT WILL MOVE THROUGH EASTERN KENTUCKY BETWEEN ABOUT 8Z AND
13Z...WITH GUSTY WINDS GRADUALLY SHIFTING TO THE WEST AND NW BEHIND
IT. CIGS WILL FALL INTO THE IFR RANGE ALONG AND BEHIND THE
FRONT...WITH LIFR OR POSSIBLY BRIEF VLIFR ON RIDGETOP LOCATIONS. AN
END TO THE SHOWERS AND SCATTERING OUT OF THE LOW CLOUDS SHOULD BEGIN
ABOUT 16Z...WITH CIGS IMPROVING TO VFR WEST AND MVFR EAST BY THE END
OF THE PERIOD.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...RAY/JP
LONG TERM....SCHOETTMER
AVIATION...DUSTY
