FXUS63 KJKL 050749
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
249 AM EST SAT DEC 5 2009

.NEAR TERM.../THROUGH 12Z/

ALL THICKNESSES AND PARTIAL THICKNESSES AS WELL SFC WET BULB AND SFC
TEMPERATURES ARE ALL CURRENTLY SUPPORTIVE OF SNOW AND WITH A COLD
ADVECTION PATTERN TO CONTINUE WITH THE UPCOMING SYSTEM THE PRECIP
WILL FALL AS ALL SNOW. BASED ON THE LATEST RADAR TRENDS AND VWP
INDICATING SATURATION AS FAR NORTH AS JKL DOWN TO ABOUT 6KFT
MSL...AND AN APPROACHING RATHER VIGOROUS 500 MB TROUGH...SNOW SHOULD
DEVELOP WITHIN THE NEXT 1 TO 3 HRS...POSSIBLY PICKING UP CLOSER TO 9Z IN
A ZONE FROM ABOUT MCCREARY COUNTY NORTHEAST TOWARD MARTIN COUNTY
ALONG A 500 MB DEFORMATION ZONE DEPICTED BY THE 0Z NAM. MODELS ALSO
INDICATE AN AREA OF ENHANCED PETTERSON FRONTOGENESIS...ESPECIALLY AT
850 MB THROUGH 12Z...ORIGINATING NEAR THE ABOVE MENTIONED CORRIDOR
AND THEN GRADUALLY SHIFTING EAST IN ASSOCIATION WITH THE APPROACHING
UPPER WAVE AND REFLECTION OF THIS SYSTEM AT LOWER LEVELS. THE 21Z
SREF ALSO HAS INITIALLY HIGHER POPS NORTH OF THE VA BORDER
COUNTIES... THOUGH THE SNOW SHOULD PICK UP ALONG THE VA BORDER BY THE
9Z TO 12Z PERIOD IF IT DOES NOT BEFORE. THE LOWER LEVELS ARE
SATURATED OR NEARLY SATURATED ALONG THE VA BORDER PER RECENT
OBSERVATIONS FROM BLACK MTN...KLNP AND US 119 HIGHWAY ON PINE
MTN...WITH LAPS SOUNDINGS INDICATING A SATURATED COLUMN ALONG THE VA
BORDER AND NEARLY SATURATED TO THE NW. LIFT APPEARS TO BE LACKING A
BIT AT PRESENT...BUT SOME RADAR RETURNS ARE ADVANCING/DEVELOPING NE
TOWARD THAT REGION IN THE ADVISORY AND AS LIFT INCREASES IN ADVANCE
OF THE UPPER LOW AS MENTIONED ABOVE SNOW SHOULD BREAK OUT IN THE NEXT
3 HOURS.

.SHORT TERM.../TODAY THROUGH SUNDAY/...UPDATED

THE MAIN FOCUS FOR THE SHORT TERM FORECAST WILL BE TO DEAL WITH LIGHT
SNOW BEGINNING NOW AND LASTING THROUGH MUCH OF THE DAY ON SATURDAY.
CURRENT RADAR IMAGERY SHOWS SOME RETURNS IN THE 20-30 DBZ RANGE ACROSS
THE CWA...HOWEVER NOT REACHING THE GROUND JUST YET. RECENT RADAR
TRENDS COMBINED WITH VWP DO SUGGEST THAT COLUMN IS STEADILY
SATURATING DOWN AND EXPECT LIGHT SNOW TO BEGIN TO FALL IN MANY
LOCATIONS BY 3 AM. HAVE DECIDED TO EXTEND THE WINTER WEATHER
ADVISORY A LITTLE FURTHER WESTWARD TO ACCOUNT FOR H85-H5
FRONTOGENESIS DEPICTED BY 0Z NAM. WILL NOW INCLUDE WHITLEY...KNOX AND
CLAY COUNTIES TO THE WSW. THIS MATCHES 21Z SREF QPF BAND FURTHER
WEST. FEEL THAT THE 1 TO...LOCALLY 2...INCH LINE WILL BE POSSIBLE
ALONG A LINE FROM WHITLEY COUNTY NORTHWESTWARD TO MARTIN COUNTY AS A
RESULT. EXTENDED THE LIKELY POPS JUST A LITTLE BEST TO MATCH UP WITH
INCREASING SNOW TOTALS TO THE WEST A BIT.

H5 TROUGH AXIS SLIDES BY THE CWA AROUND 18Z TODAY...AND WITH
STEEPENING LAPSE RATES FROM MID LEVEL CAA...FEEL THAT SNOW GETS A BIT
SHOWERY. WITH HIGH PRESSURE BUILDING IN FROM THE WEST...THIS PERIOD
WILL NOT LAST LONG AS LOW LEVEL MOISTURE QUICKLY DIMINISHES AND
CLEARING COMMENCES. TOMORROW NIGHT IS SETTING UP TO BE QUITE CHILLY
AND HAVE LOWERED TEMPERATURES JUST A BIT. FEEL THAT SOME UPPER TEENS
ARE WARRANTED WITH OTHER LOCATIONS IN THE LOWER 20S. TEMPERATURES
THIS COLD WILL BE DEPENDENT ON AMPLE CLEARING. IF FRESH SNOW COVER
DOES NOT MELT OFF IT COULD HELP MORE LOCATIONS INTO THE UPPER TEENS.

TEMPERATURES RECOVER TO THE MID 40S ON SUNDAY WITH MOSTLY CLEAR SKIES
IN ORDER. SOME UPPER LEVEL CLOUDS WILL BEGIN TO ADVECT INTO THE
REGION ON SUNDAY AFTERNOON.

AN UPDATED LONG TERM DISCUSSION WILL FOLLOW SHORTLY.

.LONG TERM.../SUNDAY NIGHT THROUGH FRIDAY/

04/00Z AND 12Z MODELS OFFER NO BIG SURPRISES SYNOPTICALLY NEXT WEEK
AND FEW CHANGES HAVE BEEN MADE TO THE FORECAST DURING THE PERIOD.
04/00Z ECMWF IS THE PREFERRED MODEL WHERE ANY DIFFERENCES EXIST. THE
DEGREE OF COOLING BEHIND OUR MIDWEEK SYSTEM IS THE BIGGEST QUESTION
MARK... WITH THE GFS BEING 6 TO 7C DEGREES COOLER AT 850 MB THAN THE
ECMWF AT 12Z THURSDAY. THE FAST PROGRESSIVE FLOW SHOULD MEAN LESS
OVERALL INTRUSION OF COLDER AIR THIS FAR SOUTH... THUS THE PREFERENCE
FOR THE WARMER ECMWF.

AS FOR SENSIBLE WEATHER... A WEAK SYSTEM IS STILL ON TAP TO BRING A
THREAT FOR PRECIP TO OUR AREA ON MONDAY. ANTECEDENT CONDITIONS ARE
VERY DRY AND THERE IS NOT A LOT OF MOISTURE ASSOCIATED WITH THE
SYSTEM SO CONTINUED TO ONLY OFFER A SLIGHT CHANCE OF SHOWERS DURING
THE DAY. THICKNESSES UP NORTH INDICATE THE POTENTIAL FOR A LITTLE
SNOW TO MIX IN... IF ANYTHING OCCURS AT ALL. OTHERWISE... A BRIEF
LULL IN RAIN CHANCES MONDAY NIGHT WILL BE FOLLOWED BY CHANCE POPS ON
TUESDAY AS OUR NEXT... MUCH MORE ROBUST SYSTEM APPROACHES FROM THE
WEST. PROGS INDICATE A VERY POTENT LOW LEVEL JET WITH THIS SYSTEM...
WITH GUSTY SOUTH TO SOUTHEASTERLY WINDS AT THE SURFACE. IN FACT...
WINDS MAY BE THE BIGGEST THREAT WITH THIS SYSTEM. A RESULTING RAIN
SHADOW SHOULD MEAN A DELAYED ONSET TO THE PRECIP... HOWEVER...
DYNAMICS WILL LIKELY OVERCOME THIS AND WE INCREASED POPS INTO THE
LIKELY RANGE FOR TUESDAY NIGHT. PROGS INDICATE A SLIGHTLY MORE
PROGRESSIVE SYSTEM SO DROPPED POPS BEHIND THE FRONT ON WEDNESDAY BUT
THERE REMAINS A CHANCE OF RAIN SHOWERS THROUGH THE DAY WITH WRAP
AROUND MOISTURE AFFECTING THE AREA AS THE UPPER TROUGH PASSES BY TO
OUR NORTHWEST. ANY LINGERING RAIN WILL MIX WITH AND CHANGE TO SNOW
WEDNESDAY NIGHT... BUT ANY PRECIP SHOULD BE VERY LIGHT BY THAT TIME.
HIGH PRESSURE WILL THEN SLIDE ACROSS THE OHIO VALLEY LEAVING DRY
CONDITIONS THURSDAY AND THURSDAY NIGHT BUT PROGS ARE ADAMANT THAT
ANOTHER SYSTEM WILL THREATEN THE AREA BY FRIDAY IN THE PROGRESSIVE
FLOW ALOFT SO WILL BRING IN FRIDAY WITH A 20 PERCENT CHANCE OF
SHOWERS.

THE 04/12Z GFSX GUIDANCE TEMPS SEEM VERY REASONABLE WITH THE
EXPECTED PATTERN NEXT WEEK... EVEN FOR TEMPS ON THURSDAY WHERE THE
MOST UNCERTAINTY LIES. THE GUIDANCE AGREES WELL WITH THE INHERITED
FORECAST NUMBERS TOO SO MADE FEW CHANGES OVERALL.

&&

.AVIATION.../06Z TO 06Z/

TAF SITES WILL START OUT ALL VFR...HOWEVER EXPECT GRADUALLY LOWERING
CEILINGS FOR THE REST OF THE OVERNIGHT. HAVE ALL TAF SITES GOING TO
MVFR BY 09Z WITH LIGHT SNOW BEGINNING TO FALL. BASED ON LATEST VWP
AND RADAR TRENDS SNOW COULD BEGIN TO FALL AN HOUR OR SO BEFORE THIS.
HAVE INCLUDED A TEMPO GROUP AFTER 12Z TO WITH CIGS/VIS FLIRTING WITH
THE MVFR/IFR RANGE. AS THE UPPER LEVEL SYSTEM QUICKLY DEPARTS
THIS AFTERNOON...EXPECT GRADUALLY IMPROVING CIGS AND SNOW ENDING
AFTER 18Z. CONDITIONS SHOULD BE BACK TO VFR BY DUSK ON SATURDAY
EVENING. SURFACE WINDS SHOULD REMAIN LIGHT AND GENERALLY OUT OF THE
NORTH THROUGH THIS AFTERNOON...BEFORE VEERING TO SOUTHEASTERLY LATE
IN THE PERIOD.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR KYZ087-
088-110-113-115-117>120.

&&

$$

NEAR TERM...JP 
SHORT TERM...SCHOETTMER 
LONG TERM...ABE
AVIATION...SCHOETTMER