FXUS63 KJKL 241148
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
648 AM EST THU DEC 24 2009
.SHORT TERM.../TODAY THROUGH FRIDAY NIGHT/
THE FIRST ISSUE TO ADDRESS IS THE LAKE WIND AND WIND ADVISORIES THAT
WILL GO INTO EFFECT AT 7 PM TODAY. THERE IS SOME CONCERN THAT WITH
THE LOW LEVEL JET NOW PROJECTED TO BE IN THE 75-85 KNOT RANGE AND VERY
CLOSE TO PERPENDICULAR TO THE TERRAIN IN THE SOUTHEAST THAT A HIGH
WIND WATCH/WARNING SHOULD BE ISSUED FOR THE FOUR COUNTIES ALONG THE
SOUTHEAST CWA BORDER. WITH THE RECENT HEAVY SNOWFALL AND THE AREA
STILL REELING FROM DOWNED TREES AND POWER OUTAGES...FEEL THE IMPACT
FROM HIGH WINDS COULD BE SIGNIFICANT. ALSO...ADDITIONAL TREES ARE
LIKELY WEAKENED DUE TO THE SNOW AND MOIST GROUND. WITH THE JET
ORIENTATION VERY CLOSE TO PERPENDICULAR TO THE TERRAIN...FEEL THAT
MOUNTAIN WAVES COULD BE A POSSIBILITY AS THIS HAS HAPPENED IN THE
PAST AND A LOCAL STUDY WOULD SUGGEST IT COULD HAPPEN AGAIN WITH THIS
SETUP. AFTER COLLABORATING WITH RLX/MRX WILL CONTINUE WITH THE WIND
ADVISORY WHICH WOULD SUGGEST GUSTS UP TO 57 MPH. THE DAY SHIFT STILL
HAS POTENTIAL TO UPGRADE TO A HIGH WIND WARNING...SO STAY UP TO DATE
WITH THE LATEST FORECASTS. THE BOTTOM LINE THAT NEEDS TO BE TAKEN
FROM THIS IS THAT THERE IS POTENTIAL FOR HIGH IMPACT EVEN WITH
STANDARD WIND ADVISORY CRITERIA AS DUE TO RECENT SNOWFALL AND CURRENT
POWER OUTAGES/DOWNED TREES.
HAVE DELAYED THE ONSET OF THE HEAVIEST PRECIPITATION UNTIL TONIGHT
BETWEEN 1 AM AND 7 AM. WILL ONLY HAVE CHANCE POPS FOR THIS AFTERNOON
AS STRONG DOWNSLOPE COMPONENT SHOULD COMBAT MOISTENING OF THE COLUMN
AND LATEST NAM/SREF HAVE COME IN MUCH SLOWER. LOW LEVEL JET REALLY
RAMPS UP TONIGHT AND IS PROGGED TO BE ANYWHERE FROM 75 TO 90 KNOTS.
OBVIOUSLY...THIS WILL ALLOW STRONG MOISTURE TRANSPORT/WAA INTO THE
REGION ABOVE A STABLE BOUNDARY LAYER. FEEL THAT MIXDOWN WILL BE HARD
EVEN IN THE STRONGER SHOWERS AS WE HAVE NOTICED WITH PAST EVENTS.
NEVERTHELESS...THE PRESSURE GRADIENT ALONE SHOULD ALLOW FOR
SUTSTAINED WINDS ABOVE 20 MPH FOR A TIME AND THIS WILL CONTINUE TO
WARRANT THE LAKE WIND ADVISORY. CANNOT RULE OUT A RUMBLE OF THUNDER
OR TWO...ALTHOUGH SOUNDINGS SHOW VERY MARGINAL ELEVATED INSTABILITY
AND WILL CONTINUE TO LEAVE THUNDER OUT OF THE ZFP.
QPF IS EXPECTED TO BE FAIRLY LOW FOR THIS EVENT FOR SEVERAL REASONS.
FIRST...CONVECTION TO THE SOUTH COULD HURT MOISTURE INTO THE REGION...
ALTHOUGH WILL HAVE TO BE CAREFUL BECAUSE ITS HARD TO IMAGINE MOISTURE
NOT GETTING INTO THE REGION WITH AN 80 KNOT LOW LEVEL JET. ALSO...
MODELS ARE HINTING AT THE BEST QPF SPLITTING THE CWA TO THE NORTH AND
SOUTH...A PATTERN THAT IS COMMON WITH OCCLUDED AND SHEARING OUT
FRONTS OBSERVED IN THE PAST FOR THIS AREA. OVERALL...A QUARTER TO A
HALF AN INCH IS EXPECTED...HOWEVER WITH THE STRENGTH OF THE LOW LEVEL
JET...CANNOT RULE OUT HIGHER AMOUNTS AT THIS POINT.
AS FAR AS TEMPERATURES ARE CONCERNED...DID NOT CHANGE A WHOLE LOT
FROM THE PREVIOUS FORECAST. EXPECTING ANOTHER NICE WARM UP
TODAY...WITH SNOW PACK AREAS STILL STRUGGLING. TONIGHT WILL SEE A
SMALL DROP OFF IN TEMPERATURES AS STRONG WARM AIR ADVECTION COMBINES
WITH HEAVY SKY COVER AND PRECIPITATION.
DRY SLOT WORKS INTO THE AREA FRIDAY NIGHT AND WILL LIKELY CREATE A
LULL IN PRECIPITATION. THIS WOULD HAVE BEEN THE TIME WHEN RAIN
CHANGED OVER TO SOME SNOW. HOWEVER...AT THIS POINT THERE WILL ONLY BE
A SLIGHT CHANCE FOR SNOW TOWARD DAWN IN NORTH OF INTERSTATE 64 AND IN
THE EXTREME EAST.
.LONG TERM.../SATURDAY THROUGH WEDNESDAY/
THE MODELS START OUT IN PRETTY GOOD AGREEMENT. ON SATURDAY
MORNING...A STRONG BLOCKING RIDGE EXTENDS FROM CALIFORNIA THOUGH
BRITISH COLUMBIA AND THERE IS A VERY STRONG UPPER LOW LOCATED OVER
CENTRAL IL ON THE GFS AND OVER SOUTH WI ON THE ECMWF. THE UPPER
PATTER IS IN PRETTY GOOD AGREEMENT THROUGH SUNDAY NIGHT AS THE
UPPER RIDGE AND UPPER LOWS ARE BOTH DISPLACE EASTWARD. THE GFS IS A
BIT FASTER MOVING THE UPPER LOW TO THE EAST. AS THE UPPER LOW MOVES
OFF TO THE EAST IT ALLOW FOR A PATTERN THAT WOULD BE FAVORABLE FOR
CLIPPERS. THE PREFERRED MODEL FOR MAKING THE FORECAST IS THE ECMWF.
ON SATURDAY...WE START OUT WITH A FRONT THAT HAD PREVIOUSLY MOVED
THROUGH THE AREA. THE COLD AIR HAS ALREADY MOVED IN...BUT A DRY
SLOT ALLOWS THING TO STAY DRY UNTIL SUNDAY AFTERNOON WITH THE WRAP
AROUND MOISTURE FROM THE LOW FINALLY MOVES ACROSS THE AREA. THERE
SHOULD THEN BE A STEADY STREAM OF CLIPPERS WHICH WILL BRING MOSTLY
ISOLATED SHOWER ACTIVITY TO THE REGION...EXCEPT FOR THE MOUNTAINOUS
AREAS IN THE BORDER COUNTIES. ON TUESDAY...THE MODEL DISAGREEMENT
IS QUITE HIGH. THE PROBLEM IS HOW TO HANDLE THE LOW UNDERCUTTING
THE UPPER RIDGE AND TRANSITIONING TO A NEW PATTERN. THIS IS A
PROBLEM FOR MOST MODELS...SO FOR TUES ON...THE CONFIDENCE IN THE
FORECAST SPIKES DOWN. UPPER RIDGES ARE PRETTY PESKY AND DO NOT WANT
TO BE MOVED OR BROKEN DOWN...HOWEVER THE MODELS NORMALLY TRY TO MOVE
THE RIDGES TOO QUICKLY.
&&
.AVIATION.../12Z TO 12Z/...UPDATED
EXPECT MAINLY VFR CONDITIONS TODAY...HOWEVER CIGS WILL GRADUALLY
LOWER TO JUST ABOVE MVFR THRESHOLD BY MIDNIGHT WITH RAIN BEGINNING AT
KSME/KLOZ AND WORKING WEST. HEAVIEST RAIN IS FORECAST TO FALL AT TAF
SITES FROM 3Z TO 12Z WITH PERIODS OF MVFR/IFR IN THE HEAVIER RAIN
SHOWERS. ALSO...SURFACE WINDS WILL GRADUALLY STRENGTHEN OUT OF THE
EAST AND SOUTHEAST TODAY. BY TONIGHT...EXPECT SUSTAINED WINDS OF 10
TO 20 MPH WITH GUSTS UP TO 40 MPH. IN THE HIGHER TERRAIN IN THE
SOUTHEAST...GUSTS UP TO 55 MPH CANNOT BE RULED OUT. A LOW LEVEL JET
OF 80 KNOTS FLOWING PERPENDICULAR TO THE TERRAIN COULD CREATE
MOUNTAIN WAVE TURBULENCE AND WILL INCLUDE LLWS OUT OF THE SOUTHEAST
AT 50 KNOTS BELOW 2000 FEET. ALTHOUGH CONDITIONS WILL LIKELY BE VFR
THROUGH MOST OF THE FORECAST PERIOD...STRONG SURFACE WINDS WILL
LIKELY MAKE IT DIFFICULT TO FLY SMALL AIRCRAFT BY LATE THIS
AFTERNOON.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY FROM 7 PM THIS EVENING 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 THIS EVENING TO 4 PM EST FRIDAY FOR
KYZ087-088-118-120.
&&
$$
SHORT TERM...SCHOETTMER
LONG TERM....JJ
AVIATION...SCHOETTMER
