FXUS63 KJKL 291756
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
1256 PM EST SUN NOV 29 2009
.SHORT TERM.../REST OF TODAY/...UPDATED
TEMPS WERE OUT OF THE GATE VERY QUICKLY THIS MORNING WITH HOURLY
TEMPS RUNNING SEVERAL DEGREES HIGHER THAN EXPECTED. BUT INCOMING
CLOUDS SHOULD KEEP HIGH IN CHECK. ADJUSTED HOURLY ISC GRIDS FOR
LATEST OBS/TRENDS...AND FRESHENED UP ZONE WORDING. ALSO INCLUDED
A RANGE TO AFTERNOON HIGH TEMPS TO ACCOUNT FOR POSSIBLE PARTIAL
CLEARING THROUGH THE AFTERNOON.
THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS...
/TODAY THROUGH TUESDAY/
FRONTAL PASSAGE FAIRLY CERTAIN BETWEEN MON 06-18Z WITH LITTLE
ACTIVITY BEFORE OR AFTER FRONT. CONCERN IS WITH THE QPF. THIS LOOKS
TO BE A HIGH POP/LOW QPF EVENT WITH GENERALLY LESS THAN A HALF INCH
TOTAL EVENT QPF. HAVE FOLLOWED THE GFS FOR TIMING... ALTHOUGH ALL
MODELS ARE IN GOOD AGREEMENT WITH THE PASSAGE OF THE FRONT. FOR
SENSIBLE WEATHER... LOOK FOR A SW WIND TO PICK UP TODAY BETWEEN 7 AND
12 MPH... WITH HIGH TEMPS RISING INTO THE MID 60S IN SPITE OF
INCREASING CLOUDS. SHIELD OF PCPN IN ADVANCE OF FRONT TO CROSS THE
I-75 CORRIDOR AROUND 06Z WITH THE BACK EDGE EXITING THE CWFA TO THE
EAST BETWEEN 15-18Z. PROGRESSIVE SYSTEM WITH LIMITED MOISTURE WILL
LIMIT RAINFALL EVEN THOUGH EVERYONE SHOULD BE ABLE TO REPORT A
MEASURE ABLE AMOUNT. WITH THE PCPN TO OCCUR DURING NORMALLY THE TIMING
OF OUR LOW TEMPS... FEEL THERE WILL BE A MODIFICATION OF THE LOWS
WITH MOST LOCATIONS ONLY DROPPING INTO THE MID 40S. PCPN WILL EXIT
DURING THE EARLY MORNING HOURS OF MON BUT CONTINUED CLOUD COVER AND
COLD/DRY AIR ADVECTION WILL LIMIT THE DIURNAL RISE IN TEMPS TO ONLY
THE UPPER 40S. THEN EXPECT THE SKY TO BEGIN CLEARING LATE WITH
OVERNIGHT TEMPS TUE MORNING TO DROP TO AROUND THE FREEZING MARK. WILL
HAVE TO WATCH THESE TEMPS FOR THE AMOUNT OF CLEARING AND IF WE CAN
SET UP A DECENT RIDGE/VALLEY SPLIT AS THE DRIER AIR PUSHING IN BEHIND
THE FRONT COULD ALLOW VALLEY TEMPS TO PLUNGE INTO THE UPPER 20S
WITHOUT MUCH PROBLEM. HOWEVER THE CLEAR SKY... DRIER AIR AND A RETURN
TO SW FLOW WILL PUSH MAX TEMPS ON TUE BACK INTO THE MID 50S.
.LONG TERM.../TUESDAY NIGHT THROUGH SATURDAY/
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 AIR MASS 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 AIR MASS 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 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.../18Z TO 18Z/...UPDATED
MID AND HIGH CLOUDS ARE RAPIDLY OVERSPREADING THE AREA. UPSTREAM
SATELLITE LOOP DOES SHOW A FEW BREAKS. BUT IN GENERAL CLOUDS WILL
CONTINUE TO INCREASE AND LOWER WITH TIME. SHOWERS WILL ENTER THE
PICTURE IN ERNST LATE THIS EVENING...THOUGH COULD NOT RULE OUT SOME
ISOLATED SHOWER ACTIVITY AROUND KSME AND KLOZ CLOSER TO SUNSET. A
COLD FRONTAL BOUNDARY WILL MOVE THROUGH EASTERN KENTUCKY TOWARDS DAWN
ON MONDAY. CIGS AND VSBYS WILL DROP INTO MVFR RANGE AS FRONTAL
SHOWERS ARRIVE...WITH CIGS THEN FALLING FURTHER INTO THE IFR RANGE
POST FRONTAL. HIGHER RIDGETOP TERMINALS WILL LIKELY SEE LIFR CIGS.
SHOWERS AND AT LEAST PARTIAL CLEARING SHOULD OCCUR A JUST BEYOND THE
END OF THE FORECAST PERIOD.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...DUSTY/RAY
LONG TERM....SCHOETTMER
AVIATION...RAY
