FXUS63 KJKL 030252
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
952 PM EST WED DEC 2 2009
.SHORT TERM.../THE REST OF TONIGHT/...UPDATED
UPDATED THE HOURLY TEMPERATURE...DEWPOINT...AND WIND GRIDS WITH
OBSERVATIONAL DATA THROUGH 2Z. HOURLY TEMPERATURES HAVE BEEN RUNNING
MUCH WARMER THAN PREVIOUSLY FORECAST...MAINLY DUE TO A PERIOD OF
CLEARING THAT OCCURRED DURING THE LATE AFTERNOON HOURS. INSPITE OF
THIS...THE LATEST HOURLY TEMP OBS UPSTREAM INDICATE THAT TEMPERATURES
WILL DECREASE RAPIDLY AS COLD AIR RUSHES IN BEHIND A DEPARTING LOW
PRESSURE SYSTEM. THEREFORE...OVERNIGHT LOW TEMPERATURES SHOULD BE
WELL WITHIN REACH. MADE A FEW TWEAKS TO THE POP...WEATHER...AND QPF
FORECAST GRIDS...BUT THE OVERALL TREND IS STILL THE SAME. WITH
PACKETS OF ENERGY ROTATING AROUND THE AFOREMENTIONED LOW
PRESSURE...AND RADAR IMAGERY INDICATING THAT ANOTHER AREA OF SHOWERS
MOVING IN FROM THE SOUTHWEST...DECIDED TO CONTINUE WITH LIKELY POPS
THROUGH ABOUT 6Z TONIGHT. AFTER 6Z THE RAIN WILL TAPER OFF TO
SCATTERED LIGHT RAIN SHOWERS ON THE BACK SIDE OF THE DEPARTING LOW.
WINDS WILL ALSO DROP OFF GRADUALLY OVERNIGHT...BUT WILL REMAIN GUSTY
FOR THE NEXT COUPLE OF HOURS. THE LAST CHANGE MADE TO THE FORECAST
WAS THE REMOVAL OF STALE WORDING FROM THE TONIGHT PERIOD OF THE ZONE
FORECAST TEXT PRODUCT. UPDATED ZONES WILL BE ISSUED SHORTLY.
THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS...
/THE REST OF TONIGHT/
UPDATED THE ZONE FORECAST TEXT PRODUCT AND GRIDS TO REFLECT THE
EXPIRATION OF THE LAKE WIND ADVISORY. SOME OTHER GRID MODIFICATIONS
HAVE BEEN MADE AND AN ADDITIONAL FORECAST UPDATE WILL BE NEEDED TO
REFLECT THESE CHANGES...AND TO REMOVE SOME OUTDATED WORDING FROM THE
TONIGHT PERIOD OF THE ZONE TEXT PRODUCT.
THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS...
/TONIGHT THROUGH THURSDAY/
SFC FEATURES SHOW LOW PRESSURE CENTERED OVER SOUTH CENTRAL KY THIS
AFTERNOON...WITH UPPER LEVEL CLOSED LOW ROUGHLY OVER LITTLE ROCK.
THERE IS A PRONOUNCED DRY SLOT PUSHING NORTHWARD INTO OUR AREA FROM
THE SOUTH. THIS FEATURE PRESENTS THE FORECAST CHALLENGE FOR THE
SHORT TERM...I.E. PROBABILITY OF RAIN FOR TONIGHT WITH THE USUALLY
VERY RELIABLE NAM IN THE IMMEDIATE SHORT TERM COMING IN DRIER THAN
THE GFS. THIS HAS RESULTED IN SIGNIFICANT DIFFERENCES IN MOS
GUIDANCE FOR POPS OVERNIGHT AS WELL...WITH THE NAM ADVERTISING
SLIGHT TO CHANCE POPS AND THE MAV MOS PREDICTING HIGH LIKELY TO CAT
POPS. CONSIDERING THE PROXIMITY AND TRACK OF THE LOW...PREFERRED TO
STAY CLOSER TO THE MORE ROBUST MAV MOS GUIDANCE AND USED A BLEND OF
THIS WITH PERSISTENCE. THEREFORE EXPECT RAIN TO REDEVELOP AS THIS
SYSTEM TRACKS NORTHEAST TONIGHT. WITH AMPLE MOISTURE ASSOCIATED WITH
THIS SYSTEM...EXPECT SHOWERS TAPER OFF TO DRIZZLE DURING THE DAY
THURSDAY. OTHERWISE...WITH EXTENSIVE CLOUD COVER THROUGH THE BULK OF
THE OVERNIGHT PREFERRED WARMER MOS GUIDANCE FOR OVERNIGHT LOWS AD
COOLER NUMBERS FOR HIGHS THURSDAY. THIS JIVES VERY WELL WITH
INHERITED GRIDS SO ONLY MINOR TWEAKS WERE MADE TO TEMPS...MORE FOR
CCF PURPOSES. HAD SOME REPORTS OF WIND DAMAGE IN TN...AND HAVE SEEN
DECENT INTERMITTENT GUSTS FROM AREA SFC OBS. THEREFORE WILL LET
CURRENT NPW RIDE THROUGH 6 PM.
.LONG TERM.../THURSDAY NIGHT THROUGH WEDNESDAY/
GOOD CHANCE OF DRIZZLE OR EVEN FLURRIES THU EVENING BUT FIGURE
MOISTURE WILL BE TOO SHALLOW TO MEASURE OUT. A LITTLE BETTER CHANCE
OF SNOW FRI NIGHT BUT MODELS BARELY BRUSH BY WITH ENOUGH MOISTURE
BELOW 700 MB SO SLIGHT CHANCE STILL SUFFICIENT.
00Z GFS/ECMWF/CANADIAN MODELS AGREED PRETTY WELL THROUGH 144 HOURS
(00Z TUE) IN A HIGH AMPLITUDE PATTERN HOLDING ON. BY THAT TIME A 5H
RIDGE WOULD EXTEND NORTH INTO AK AND A LOW/TROUGH EXTENDING FROM NWT
TO NV/OR. THEREAFTER THE DIFFERENCES INCREASE BUT GFS/ECMWF AGREE IN
A STRONG SOUTHERN STREAM DOMINATING CONUS. TIMING OF THE EMBEDDED
SHORTWAVE PASSING THROUGH THE MIDWEST AT MID-WEEK IS DIFFICULT FOR
THESE MODELS ATTM AND WILL NOT LATCH ONTO ANY ONE FOR NOW.
12Z GFS AND ECMWF AGREE A LITTLE BETTER ON THE SHORTWAVE PASSING
EAST KY EARLY ON WED WITH THE COLD FRONT AND ASSOCIATED PRECIPITATION
OCCURRING LATE ON TUE NIGHT. THIS IS GOOD ENOUGH TO BOOST POPS TO
HIGH CHANCE BUT TIMING IS STILL LIKELY TO CHANGE SOME SINCE THE
UPPER FLOW IS ALMOST ZONAL WITH FAST FLOW.
&&
.AVIATION.../00Z TO 24Z/
A COLD FRONT WILL PASS EAST THROUGH THE REGION FROM WEST TO EAST
BETWEEN 00Z AND 06Z...LIKELY BRINGING SHOWERS. WEST SOUTHWEST WINDS
WILL INCREASE BEHIND THE FRONT...WITH GUSTS OF 20-25 KNOTS. THE WIND
WILL GRADUALLY DIMINISH OVERNIGHT AND THURSDAY MORNING. GENERALLY
VFR CONDITIONS AHEAD OF THE FRONT WILL DETERIORATE AFTER THE FRONT
PASSES...FALLING TO MAINLY IFR CEILINGS OVERNIGHT. SOME LIMITED
IMPROVEMENT IS EXPECTED TOWARD THE END OF THE PERIOD...WITH MOST OF
THE AREA IMPROVING TO MVFR CEILINGS ON THURSDAY AFTERNOON.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...RAY/AR
LONG TERM....GV
AVIATION...HAL
