FXUS63 KJKL 232332
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
632 PM EST WED DEC 23 2009

.SHORT TERM.../TONIGHT THROUGH FRIDAY/

19Z SFC ANALYSIS SHOWS THE LARGE AND CONSOLIDATING AREA OF LOW
PRESSURE OVER TEXAS. FROM THIS...A DEVELOPING WARM FRONT EXTENDED
INTO WESTERN KENTUCKY. PLENTY OF SHOWERS AND A FEW THUNDERSTORMS
ARE NOTED SOUTH OF THIS BOUNDARY THROUGH THE LOWER MISSISSIPPI
VALLEY. HIGH CLOUDS FROM THIS SYSTEM HAVE HAD A TOUGH TIME ADVANCING
TOO FAR INTO EAST KENTUCKY AND THIS HAS RESULTED IN ANOTHER GOOD DAY
OF MELTING FOR OUR SNOWBOUND AREAS. TEMPERATURES ACROSS THE CWA ARE
STRIATED MAINLY BASED ON THE SNOW AREAS IN THE UPPER 30S AND LOWER
40S VERSUS THE SNOW FREE LOCATIONS...PARTICULARLY THE CUMBERLAND
VALLEY...SEEING THE LOWER TO MID 50S. WITH THE SNOW MELT ADDING TO
THE BOUNDARY LAYER MOISTURE DEWPOINTS ARE GENERALLY IN THE MID AND
UPPER 30S.

THE MODELS CONTINUE TO HAVE DIFFERENCES ALOFT WITH THE EVOLUTION OF
THE IMPENDING...LARGE AND DOMINANT...UPPER LOW DEVELOPING OVER THE
MIDDLE OF THE COUNTRY BY FRIDAY MORNING AND PROGGED TO SLOWLY
DRIFT NORTH INTO THE WEEKEND. THIS DEVELOPMENT WILL SHUNT THE
RIDGING THE OHIO VALLEY IS CURRENTLY ENJOYING EAST BY MIDDAY THURSDAY
LEAVING THE AREA ON THE FRINGE OF THE EMERGING MEGA LOW. TWIN SHORT
WAVES...AND PARTICULARLY THE SOUTHEAST ONE...THAT MERGE TO FORM THIS
LOW ARE HANDLED SLIGHTLY DIFFERENT BY EACH MODEL AS EARLY AS THURSDAY
MORNING. THE NEW ECMWF IS THE SLOWEST AND FURTHEST SOUTH WITH THE
TEXAS WAVE AT 12Z THURSDAY AND THESE DIFFERENCES ARE MAGNIFIED BY
EVENING WITH THE ECMWF BRINGING ITS TROUGH FURTHER SOUTHEAST THAN THE
NAM OR GFS. HOWEVER... ALL SEEMS BACK ON TRACK BY FRIDAY MORNING AS
THE ECMWF MAKES THE SECOND WAVE DROPPING THROUGH THE HIGH PLAINS THE
MAIN CENTER LEAVING THE GFS FURTHEST TO THE EAST AND NAM IN BETWEEN.
THEY ALL MELD BETTER INTO THE ANTICIPATED GIANT LOW BY 00Z SATURDAY
WITH THE ECMWF THE DEEPEST WHILE PLACING ITS CENTER CLOSER TO THE
NAM/S IN NORTHEAST MISSOURI VERSUS THE ILLINOIS EXTENT OF THE GFS.
GIVEN THE COMPLEX AND DYNAMIC SCENARIO UNFOLDING...AND TRENDS AWAY
FROM THE GFS...HAVE CHOSEN TO FOLLOW A BLEND OF THE NAM AND ECMWF
ALOFT...AND FOR WX SPECIFICS...THROUGH FRIDAY.

SENSIBLE WEATHER WILL FEATURE CLOUDS OVERSPREADING EAST KENTUCKY
THIS EVENING FROM THE SFC LOW DEEPENING TO OUR SOUTHWEST. HOWEVER...
THESE CLOUDS WILL LIKELY NOT BE THICK ENOUGH...NOR THE NOCTURNAL WAA
STRONG ENOUGH...TO PREVENT A NUMBER OF LOCATIONS...VALLEYS AND POINTS
NORTH OF THE MOUNTAIN PARKWAY...FROM FALLING TO BELOW FREEZING
TONIGHT. NORMALLY THIS WOULD NOT BE A PROBLEM...BUT LATE TONIGHT
THERE REMAINS A POSSIBILITY OF A STRAY SHOWER BAND DRIFTING INTO OUR
WESTERN TERRITORIES CAUSING THE RISK OF FREEZING RAIN TO REAR ITS
UGLY HEAD. THIS RISK IS TRULY MARGINAL...THOUGH...AS ANY SHOWER WILL
BE BRIEF AND QUITE LIGHT. JUST THAT SAME IT WILL BE MENTIONED IN THE
ZONES WHERE IT IS A POTENTIAL AS WELL AS HIGHLIGHTED IN THE HWO.

THE SFC LOW...AND MORE SPECIFICALLY ITS EASTWARD ARCING FRONT...WILL
INCH INTO THE CWA LATER THURSDAY WITH INCREASING CHANCES OF MODERATE
RAINS FROM WEST TO EAST WITH TIME. THIS BAND...FOLLOWING THE LATEST
ECMWF AND NAM SOLUTION...WILL PUSH STEADILY THROUGH EAST KENTUCKY
THURSDAY NIGHT. THE RAIN WILL BE ENHANCED BY AMPLE UPPER LEVEL
DIVERGENCE OVER EAST KENTUCKY DUE TO BEING ON THE EDGE OF A COUPLE
OF JET STREAKS CYCLING AROUND THE UPPER LOW. IN ADDITION...A LOW
LEVEL JET AT 850 MB WILL INCREASE TO 75 KTS AS IT PASSES OVER THE CWA
THURSDAY NIGHT BOTH ENHANCING THE RAINFALL AND INCREASING THE RISK OF
HIGH WINDS REACHING THE SFC...ESPECIALLY GIVEN THE WAY IT BISECTS OUR
RIDGE ORIENTATION. ACCORDINGLY...WILL BE ISSUING A WIND ADVISORY FOR
OUR FOUR MOUNTAIN COUNTIES BORDERING VIRGINIA STARTING AT 7 PM EST 
THURSDAY AND RUNNING THROUGH 4 PM EST FRIDAY. THE WINDS WILL BE
STRONG ELSEWHERE THROUGH FRIDAY AFTERNOON...BUT SHOULD NOT POSE AS
MUCH OF A THREAT IN THE LOWER TERRAIN. THEREFORE...FOR THE REST OF
THE CWA...WILL BE ISSUING A LAKE WIND ADVISORY TO HIGHLIGHT WINDS OF
20 TO 30 MPH AND POSSIBLE GUSTS TO 45 MPH THROUGH THE SAME TIME FRAME
OF THE WIND ADVISORY.

EXPECTING A GOOD SIX HOURS OF MODERATE TO OCCASIONALLY HEAVY RAINS
AS THE FRONT PASSES THURSDAY NIGHT RESULTING IN BASIN AVERAGE QPF OF
A HALF TO ONE INCH. THIS...COMBINED WITH THE LINGERING SNOW COVER
MELTING OFF IN THE RAINS...RAISES A CONCERN FOR FLOODING. HOWEVER...
AT THIS POINT...MUCH OF THE SNOW MELT HAS BEEN MAKING IT INTO THE
RIVERS OVER THE PAST THREE DAYS LIMITING THE POTENTIAL FOR ITS
CONTRIBUTION TO ANY MORE THAN A LOCALIZED FLOOD THREAT. WILL MENTION
THE POTENTIAL FOR ISOLATED FLOODING IN THE HWO AND ALSO IN A SPS
HIGHLIGHTING THE SPECTRUM OF WEATHER TO EXPECT FROM THIS LARGE STORM
SYSTEM...EVEN AS IT JUST BRUSHES US.

THE MODELS ALL POINT TO A GOOD DRY SLOT COMING THROUGH EAST KENTUCKY
ON FRIDAY ENDING THE RAIN QUICKLY AND EVEN ALLOWING FOR THE CLOUDS TO
BREAK UP BY MIDDAY. OF COURSE...ANY CLEARING WILL ONLY ENHANCE THE
WIND POTENTIAL THROUGH FRIDAY AFTERNOON NECESSITATING RUNNING THE
ADVISORIES UNTIL WELL PAST THE SFC GRADIENT RELAXING. IN ADDITION...
SUNSHINE WOULD CURB THE COOLING EFFECT OF THE CAA ON THE BACKSIDE OF
THE FRONT FRIDAY...LIMITING THE AFTERNOON DROPOFF IN TEMPS COMPARED
TO WHAT WAS DEPICTED BY THE MODELS 24 HOURS AGO. ALSO...EXPECT A NON
DIURNAL TEMP CURVE THURSDAY NIGHT WITH THE FRONT PASSING. USED THE
DIURNAL FROM MODEL TOOL AND THE NAM AS AN INPUT TO DERIVE TEMPS FOR
THE LATTER PORTION OF THE SHORT TERM FORECAST.

AS FOR TEMPS...STILL MASSAGED THEM FOR LEFTOVER SNOW PACK THROUGH
THURSDAY AFTERNOON ALONG WITH THE RIDGE TO VALLEY SPLIT SET UP
ANTICIPATED TONIGHT. THURSDAY NIGHT AND FRIDAY TEMPS WERE CLOSER TO
THE MET THAN THE MAV...BUT MAINLY FOLLOWED THE DIURNAL TRENDS FROM
THE NAM. WITH POPS...THE MAV NUMBERS MATCHED UP CLOSEST AS CONTINUITY
WAS HONORED TO SOME EXTENT WHILE THE MET SHOWED A SLOWER ARRIVAL TO
THE ANY RAIN TONIGHT AND THURSDAY. FOLLOWING THAT...THE MET GUIDANCE
MATCHED UP CLOSEST TO OUR GRIDS FOR POPS TONIGHT...THOUGH DID END
THE RAIN WEST TO EAST A BIT QUICKER THAN GUIDANCE WOULD IMPLY.

.LONG TERM.../FRIDAY NIGHT THROUGH WEDNESDAY/

LONG WAVE TROUGH TO REMAIN NEAR WESTERN GREAT LAKES AND ALONG 
MISSISSIPPI RIVER THROUGH THIS PERIOD. THIS WILL ALLOW FOR MINIMAL 
CHANGES DURING THE WEEKEND AND EARLY NEXT WEEK...COLD ENOUGH TO SNOW 
IF ANY PRECIPITATION OCCURS. MOISTURE WILL NOT BE DEEP ENOUGH FOR 
SIGNIFICANT SNOW EXCEPT POSSIBLY SUNDAY BUT LOW LEVEL RIDGE WILL BE 
IN PLACE THEN TO SUPPRESS SUCH AN OCCURRENCE. THEREAFTER CHANGED
LITTLE WITH UNCERTAINTY OVER GFS VS. ECWMF PROGRESSIVENESS OF 
EASTERN 5H LOW.

&&

.AVIATION.../00Z TO 24Z/...UPDATED

VFR CONDITIONS SHOULD BE THE RULE THROUGH THE TAF PERIOD...ALTHOUGH
SOME MVFR FOG WILL BE A CONCERN OVERNIGHT...ESPECIALLY AT
JKL...WHERE SOME TEMPORARY IFR CONDITIONS MAY IMPACT THE SITE JUST
BEFORE DAWN. CEILINGS WILL GENERALLY BE AROUND 10K...ALTHOUGH SOME
OCCASIONAL 5-6K CEILINGS...POSSIBLY CONTAINING A FEW SPRINKLES WILL
MOVE THROUGH FROM TIME TO TIME...ESPECIALLY NEAR THE I-75 CORRIDOR.
LIGHT EAST WINDS WILL BECOME MORE SOUTHEASTERLY AND TURN GUSTY TOMORROW
AFTERNOON. THE STRONGEST WINDS WILL HOLD OFF UNTIL AFTER 00Z FRIDAY
AS WELL AS THE MAJORITY OF THE SHOWER ACTIVITY AS A STRONG COLD FRONT
MOVES THROUGH THE STATE.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY FROM 7 PM THURSDAY TO 4 PM EST FRIDAY FOR 
KYZ044-050>052-058>060-068-069-079-080-083>086-104-106>117-119.

WIND ADVISORY FROM 7 PM THURSDAY TO 4 PM EST FRIDAY FOR KYZ087-
088-118-120.

&&

$$

SHORT TERM...GREIF
LONG TERM....GV
AVIATION...GEOGERIAN