FXUS63 KJKL 081536
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
1036 AM EST TUE DEC 8 2009

.SHORT TERM.../TODAY THROUGH THURSDAY/...UPDATED

FORECAST APPEARS IN GOOD SHAPE TODAY WITH RAIN DEVELOPING FROM
NORTHWEST TO SOUTHEAST INTO THE AFTERNOON HOURS. NO CHANGES APPEAR
TO BE NEEDED AT THIS TIME.

STILL DIGESTING DATA ON THE UPCOMING HIGH WIND EVENT. A GOOD ANALOG
APPEARS TO BE THE FEB 11-12 2009 EVENT THAT BROUGHT WIDESPREAD
DAMAGING WINDS TO THE AREA. THERE ARE IMPORTANT DIFFERENCES THOUGH:

- THE FEB EVENT HAD MUCH LESS PREFRONTAL RAINFALL THAT WE ARE
EXPECTED WITH THE UPCOMING EVENT. AN INCH OR MORE OF RAIN WILL
SATURATE THE SOIL AND SET THAT STAGE FOR POSSIBLY A LOT OF TREE
DAMAGE.
 
- THE FEB EVENT FEATURED AN INTENSE SQUALL LINE MOVING ALONG WITH
THE FRONT DURING THE EARLY EVENING HOURS OF THE 11TH PRODUCING WINDS
AS HIGH AS 70 MPH. WE ARE STILL A BIT UNSURE ABOUT HOW ORGANIZED ANY
LOW-TOPPED CONVECTION WILL BE LATER TONIGHT THOUGH AS THE LATE
NIGHT/EARLY MORNING TIMING AND LACK OF INSTABILITY WITH ALL THE
PREFRONTAL RAIN SHOULD LIMIT ANY POTENTIAL SQUALL LINE/S INTENSITY.

- POST-FRONTAL WINDS APPROACHED 60 MPH ACROSS OUR NORTH WITH THE FEB
EVENT. WINDS THROUGH THE MIXED LAYER ARE SIMILAR BETWEEN THE TWO
EVENTS BUT THE PRESSURE GRADIENT IS PROGGED TO BE STRONGER LATE
MORNING TOMORROW THAN IT WAS WITH THE FEB EVENT.

OVERALL... CONFIDENCE IS INCREASING THAT WARNING LEVEL WINDS WILL BE
WITNESSED LATE TONIGHT INTO TOMORROW ACROSS MOST... IF NOT ALL OF
OUR FORECAST AREA. EVEN THE 08/12Z NAM IS ON BOARD AFTER BEING A
DISSENTING MODEL YESTERDAY. A HIGH WIND WARNING WILL LIKELY BE
POSTED THIS AFTERNOON AFTER CLOSE COORDINATION WITH OUR NEIGHBORING
OFFICES.

THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS...

A VERY ACTIVE PERIOD IS IN STORE WITH MODERATE TO LOCALLY HEAVY
RAIN...A WINDY WED AND TURNING SHARPLY COLDER LATE BY WED NIGHT.

AN UPPER LEVEL TROUGH IS MOVING THROUGH THE ROCKIES AND APPROACHING
THE FOUR CORNERS REGION. SOME SLIGHT RIDGING WAS OVER THE
SOUTHEASTERN STATES WITH A RIDGE AXIS FROM MEXICO EAST TO CUBA AND
FURTHER EAST. AN EMBEDDED SHORTWAVE IN THE SOUTHWEST TO WEST
SOUTHWEST FLOW ALOFT IS MOVING THROUGH HE SOUTHERN MS VALLEY REGION
AND APPROACHING THE AREA FROM THE SOUTHEAST. SOME SCATTERED TO
NUMEROUS SHOWERS HAVE DEVELOPED ALONG THE GULF COAST REGION AND ALSO
FURTHER NORTH OVER AR AND WERE SLOWLY ADVANCING NORTH TOWARD THE TN
VALLEY REGION. MEANWHILE...LOW CLOUDS REMAIN ENTRENCHED LOCALLY
BETWEEN SYSTEMS WITH HIGH CLOUDS ALREADY SPREADING IN ABOVE. 

THE SHORTWAVE TO OUR SOUTH WILL LEAD TO INCREASING ISENTROPIC LIFT
OVER THE TN VALLEY AND OH VALLEY TODAY...AND THIS WILL LEAD TO AN
INCREASE IN THE CLOUDS ABOVE THE LOW DECK WITH MID AND HIGH CLOUDS
MOVING IN RAPIDLY AROUND DAWN OR AT LEAST BY MID MORNING. THE
SHOWERS NOW TO OUR SOUTH WILL ALSO APPROACH BY LATE IN THE MORNING.
MODEL FORECAST ISENTROPIC LIFT APPEARS TO BE BETTER FOCUSED TOWARD
CENTRAL KY FOR MUCH OF TODAY OR GENERALLY FROM INTERSTATE 75 WEST.
SOME AREAS IN THE DOWNSLOPE SOUTHEAST REGION MAY EXPERIENCE LESS
QPF...WITH HIGHER QPF FROM ABOUT INTERSTATE 75 WEST. WITH THIS IN
MIND...OPTED TO CONTINUE WITH 100 POPS BY LATE IN THE DAY TODAY.
TEMPERATURES WILL BE SUPPRESSED TODAY WITH ALL OF THE CLOUDS IN
PRECIP WITH A GRADUAL CLIMB TO HIGHS IN THE LATE AFTERNOON/EARLY 
EVENING.

MEANWHILE...A LOW LEVEL JET WILL CONTINUE TO INCREASE INTO THE
EVENING AND OVERNIGHT HOURS AS THE SFC LOW ASSOCIATED WITH THE
SOUTHERN ROCKIES TROUGH REDEVELOPS TO THE LEE OF THE ROCKIES THIS
AFTERNOON AND THEN HEADS TOWARD THE SOUTHERN END OF LK MI BY 12Z
WED....DEEPENING RAPIDLY THROUGH THIS TIME. THE LLJ WILL AVERAGE 55
TO 70KT DURING THE 0Z TO 8Z OR 9Z TIME FRAME...WITH A SLIGHTLY ENHANCE
AREA EXPECTED TO EXTEND INTO THE REGION. THE NAM IS A BIT WEAKER AND
FURTHER WEST WITH THE AXIS...BUT BASED ON CONSISTENCY FROM RECENT
RUNS...WE TEND TO LEAN MORE TOWARD THE MORE POTENT GFS WITH THIS
CONSIDERING THE OVERALL STRENGTH OF THE SYSTEM. THIS STRONG JET
OVERRUNNING A WARM FRONT LIFTING TOWARD THE AREA THAT GRADUALLY
BECOMES MORE DIFFUSE AS THE COLD FRONT RACES EAST WILL LEAD TO A
LARGE AREA OF ISENTROPIC LIFT AND MODERATE TO STRONG ISENTROPIC LIFT
AT TIMES. AT THE SAME TIME...THE RIGHT ENTRANCE REGION OF A JET TO
THE NORTH AND NORTHEAST WILL BE EXITING AROUND 0Z...WITH A 140 TO
150+ KT 300 MB JET PUSHING INTO THE SOUTHEASTERN STATES OVERNIGHT
WITH THE AREA GRADUALLY GETTING INTO THE LEFT EXIT REGION OF THIS JET.
THIS COMBINED WITH THE NEGATIVE TILT OF THE UPPER TROUGH WILL LEAD TO
QUITE A BIT OF DIVERGENCE AS WELL. 

WITH PW FORECAST TO CLIMB TO THE 1.2 TO 1.3 INCH RANGE ABOUT 2Z TO
ABOUT 8Z WED OR ABOUT 250 TO 275 PERCENT OF NORMAL IS OBVIOUSLY A
CONCERN. OPTED TO GO WITH THREE QUARTERS OF AN INCH TO OVER ONE INCH
QPF 0Z TO 6Z WED OVER MUCH OF THE WESTERN CWA WITH ALL OF THIS
HAPPENING. IF ANY CONVECTION COULD FOCUS NORTH TO SOUTH...SOME
TRAINING COULD POSSIBLY OCCUR WITHIN THE ENHANCED AREA OF THE LLJ. WE
WILL CONTINUE TO MENTION THE POTENTIAL FOR LOCALLY HEAVY RAINFALL. AT
THIS POINT...THE SOUTHWEST CWA APPEARS TO POSSIBLY HAVE THE HIGHEST
THREAT OF THIS PER HPC QPFERD. WE ALSO WILL CONTINUE TO MENTION THE
POSSIBILITY OF THUNDER AS THE LLJ KICKS IN AND STEEPENS MID LEVEL
LAPSE RATES COMBINED WITH THE OVERALL JET DYNAMICS.

THE FOCUS FROM LATE TONIGHT THROUGH WED EVENING CONTINUES TO BE HOW
MUCH MOMENTUM OF THE 50 TO 60KT WINDS BETWEEN 900 MB AND 850 MB CAN
MIX DOWN. THE NEARLY UNIDIRECTIONAL DIRECTION SUGGESTED BY THE 0Z GFS
AND 12Z/7TH ECMWF WOULD SUGGEST A VERY HIGH PERCENTAGE OF THE 60KT
CAN MIX DOWN. CONFIDENCE REMAINS VERY HIGH AND IS INCREASING THAT FOR
AT LEAST A FEW HOURS BETWEEN 12Z AND 21Z ON WED...WIND GUSTS COULD
REACH THE 55 TO 60 MPH OVER A LOT OF THE AREA...IF THIS OCCURS...WINDS
OF THIS MAGNITUDE COULD LEAD TO POWER OUTAGES ON WED AND WITH FALLING
TEMPERATURES TO NEAR 20 ON AVERAGE ON WED NIGHT COULD BE A BAD
SITUATION IF DAMAGE FROM THE WIND WERE TO BE WIDESPREAD AND LEAD TO A
LOT OF POWER OUTAGES AND POSSIBLY PROLONGED POWER OUTAGES IN SOME
AREAS. WITH SUCH STRONG WINDS ALOFT...MODELS BRING IN THE COLDER AIR
A BIT FASTER THAN PREVIOUSLY FORECAST ON WED...SO TEMPS SHOULD BE IN
THE 30S ACROSS THE BOARD BY EARLY WED EVENING...WITH THE NORTHWEST
PERHAPS INTO THE UPPER 20S. THE COLDER AIR WILL CONTINUE TO PUSH IN
ON WED NIGHT AND WILL LEAD TO LOWS COLDER THAN PREVIOUSLY FORECAST
WITH TEMPS LIKELY FALLING QUICKER THAN THE COLDEST MOS GUIDANCE. A
LULL IN PRECIP CHANCES WILL OCCUR DURING THE POTENTIAL GUSTY PERIOD
WITHIN THE DRY SLOT AND THEN AS LAPSE RATES STEEPEN A BIT AND HEIGHTS
FALL DURING LATE WED AFTERNOON AND EVENING...SNOW SHOWERS AND
FLURRIES ARE ANTICIPATED. THERE COULD BE A PERIOD OF RAIN OR SNOW
SHOWERS LATE WED...BUT WEST FLOW SHOULD LEAD TO SOME ENHANCEMENTS AS
THE SHORTWAVE PASSES THROUGH AND TEMPS FALL QUICKLY. MODELS SHOW SOME
SATURATION WITHIN THE -10C TO -15C RANGE SO SOME HIGH RATIO SNOW
COULD FALL. A DUSTING MAY OCCUR...ESPECIALLY ON THE RIDGES...WITH THE
ESCARPMENT OF THE DANIEL BOONE FOREST ONE POSSIBLE AREA OF
ENHANCEMENT AND ACROSS SOME OF THE RIDGES OF THE EAST AND NORTHEAST.
AT THAT POINT OPTED FOR A BRIEF PERIOD OF SCT SNOW SHOWERS AROUND 0Z
TO 4Z OR SO SHIFTING ACROSS THE AREA...EXCEPT ACROSS THE SOUTHWEST.

AS FOR TEMPERATURES THERE WILL BE A NON DIURNAL CURVE TONIGHT THROUGH
WED. TEMPS WILL RISE TONIGHT WITH THE WARM SURGE AHEAD OF THE COLD
FRONT AND THEN FALL AFTER ABOUT 15Z ON WED. AGAIN...TEMPS SHOULD
REACH THE 30S IN ALL AREAS BY 23Z. LOWS ON WED NIGHT SHOULD BE BELOW
GUIDANCE WITH UPPER TEENS WEST AND ACROSS THE HIGHER TERRAIN AND
AROUND 20 TO THE LOWER 20S ELSEWHERE. WITH 8H TEMPS PROGGED TO BE
-10C TO -13C BY LATE THU WITH 8H TEMPS EVEN COLDER DURING THE FIRST
HALF OF THE DAY TEMPERATURES SHOULD STRUGGLE TO REACH 30 DEGREES ON
THU ACROSS THE BOARD.

.LONG TERM.../THURSDAY NIGHT THROUGH MONDAY/

MODELS ARE IN REASONABLE AGREEMENT THROUGH THE EXTENDED PORTION OF
THE FORECAST. MAIN DIFFERENCES ARE FOUND IN TIMING OF SHORT WAVE
DISTURBANCES IN WESTERLY FLOW ALOFT. IN GENERAL PREFERRED THE ECMWF
TIMING AS IT TYPICALLY PERFORMS BETTER THAN THE USUALLY FASTER GFS
SOLUTIONS AND APPEARS TO HAVE DISPLAYED BETTER RUN TO RUN CONTINUITY.
THIS IS ALSO MORE IN LINE WITH PREFERENCES FROM NATIONAL GUIDANCE.
THE END RESULT WAS A SLIGHTLY SLOWER SOLUTION TO OVERALL SPEED OF
SYSTEMS TRACKING THROUGH THE REGION WITH THE FIRST RUSHING THROUGH
OUR AREA LATE SATURDAY INTO EARLY SUNDAY MORNING. TIME HEIGHT
SECTIONS AND FORECAST SOUNDINGS INDICATE THAT THE ONSET OF ANY
PRECIPITATION SATURDAY MAY BEGIN AS SNOW...OR POSSIBLY AS SOME MIXED
PRECIPITATION. HOWEVER...THE BULK OF ANY WEATHER SHOULD HOLD OFF
UNTIL TEMPERATURES HAVE WARMED ENOUGH THAT FROZEN PRECIPITATION IS
LIKELY NOT A CONCERN AT THIS TIME. A SECOND DISTURBANCE WILL TAKE AIM
AT OUR AREA JUST BEYOND THE END OF THE EXTENDED FORECAST WINDOW. 

FOR TEMPS...MADE ADJUSTMENTS FOR LATEST THOUGHTS AND TRENDS. MOST
SIGNIFICANT CHANGE WAS MADE TO FRIDAY MORNING LOWS. VERY DRY AIR WILL
BE IN PLACE ACROSS THE AREA. SFC HIGH PRESSURE TRANSITING THE REGION
WILL TEND TO KEEP WINDS LIGHT TO CALM...AND SKIES CLEAR. THEREFORE
DROPPED MORNING LOWS AT LEAST A FEW DEGREES BELOW MOS GUIDANCE...OR
LOW TO MID TEENS. HOWEVER WOULD NOT BE SURPRISED IF THERE WERE SOME
SINGLE DIGITS...ESPECIALLY IN SOME OF OUR TYPICALLY COLDER
LOCATIONS. 

&&

.AVIATION.../12Z TO 12Z/

THE PATCHY LOW MVFR CLOUD DECK HAS FINALLY CLEARED OUT OF ALL BUT
AREAS ALONG THE VA/WV BORDER. MVFR MID CLOUDS ARE ADVANCING BACK IN
THE FROM THE SOUTH AND WEST IN ADVANCE OF A DEVELOPING POTENT STORM
SYSTEM THAT WILL ORGANIZE OVER THE PLAINS THIS AFTERNOON. THIS SYSTEM
WILL SPRINT ACROSS THE CONUS...REACHING THE MIDWEST IN LESS THAN 24
HOURS. RAIN WILL DEVELOP IN THE 15Z TO 19Z PERIOD WITH THE ATMOSPHERE
GRADUALLY SATURATING DOWN BY THE 22Z TO 02Z PERIOD. INSTABILITY WILL
INCREASE OVERNIGHT AND SOME THUNDERSTORMS ARE POSSIBLE. AT THIS
POINT...DROPPED CONDITIONS BACK TO MVFR AROUND 18Z ON AVERAGE AND
THEN INTO IFR FOR MOST OF THE NIGHT. THE HIGHER TERRAIN ALONG THE VA
BORDER WILL BE IN VLIFR OR LIFR. ACROSS THE WEST AND SOUTHWEST...SUCH
AS SME...BEHIND THE FRONT...MVFR COULD RETURN LATE IN THE PERIOD.
HANDLED THE THUNDER CHANCES WITH CB CLOUD GROUPS. WINDS WILL ALSO
BECOME GUSTY OUT OF THE SOUTH AND THEN SOUTHWEST 0Z TO 12Z. AN
ISOLATED GUST IN +SHRA OR TSRA OVER 40 MPH CANNOT BE RULED OUT IN THE
0Z TO 9Z PERIOD. WINDS WILL BECOME STRONGER LATE IN THE PERIOD.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WATCH FROM LATE TONIGHT THROUGH WEDNESDAY EVENING FOR 
KYZ044-050>052-058>060-068-069-079-080-083>088-104-106>120.

&&

$$

SHORT TERM...JP/ABE
LONG TERM....RAY
AVIATION...JP