FXUS62 KCAE 020757
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
257 AM EST WED DEC 2 2009
.SYNOPSIS...
AN AREA OF LOW PRESSURE WILL MOVE FROM THE GULF COAST TO THE OHIO
VALLEY TODAY AND TONIGHT. THIS WILL SPREAD PRECIPITATION INTO OUR
REGION TODAY...ENDING WHEN A COLD FRONT MOVES THROUGH TONIGHT.
FAIR WEATHER EXPECTED THURSDAY. AN AREA OF LOW PRESSURE WILL TRACK
BY TO OUR SOUTH LATE FRIDAY AND SATURDAY...PROVIDING OUR REGION
WITH A CHANCE OF PRECIPITATION. FAIR WEATHER EXPECTED SUNDAY AND
MONDAY...WITH RETURNING MOISTURE POSSIBLE BY TUESDAY AND WEDNESDAY
FO NEXT WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
CURRENT SURFACE ANALYSIS INDICATES AN AREA OF LOW PRESSURE NEAR THE
LOUISIANA COAST...WITH A WARM FRONT STRETCHING EAST ALONG THE GULF
COAST/NORTHERN FLORIDA. CLOSED UPPER LOW IS SPINNING OVER CENTRAL
TEXAS...WITH A SW FLOW AHEAD OF IT WITH EMBEDDED IMPULSES. LEADING
EDGE OF A LARGE AREA OF ISENTROPIC LIFT INDUCED RAINFALL CURRENTLY
PUSHING THROUGH THE CSRA. UPPER AND SURFACE LOWS PROGGED BY MODELS
TO MOVE NE TODAY...AND GENERALLY REMAIN TO OUR WEST. GIVEN THIS
TRACK AND WITHOUT A STRONG PARENT HIGH TO OUR NE...ANY IN SITU
WEDGE THAT COULD DEVELOP THIS MORNING SHOULD BE WEAK AND SHORT
LIVED FOR OUR FA. SO...WILL EXPECT WARM FRONT/WEAK WEDGE BOUNDARY
TO PUSH NORTH OF OUR FA BY AFTERNOON. THIS WILL PUT MUCH OF OUR FA
IN A WARM SECTOR THIS AFTERNOON AND EARLY EVENING AHEAD OF THE
COLD FRONT WHICH WILL MOVE THROUGH TONIGHT. ALTHOUGH CLOUD COVER
COULD HAMPER INSTABILITIES. INSTABILITIES ARE PROGGED TO BE WEAK
OVER OUR FA...BUT MORE UNSTABLE NEAR THE COAST. HOWEVER...A STRONG
850MB JET AROUND 50 KNOTS EXPECTED...WITH VERY STRONG SHEAR AND
STORM RELATIVE HELICITY VALUES INDICATED...MEANING ANY SIGNIFICANT
CONVECTION THAT DEVELOPS WILL HAVE THE POTENTIAL TO PRODUCE
STRONG DAMAGING WINDS AND POSSIBLY A TORNADO. SPC INDICATES A
SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS OUR FA.
&&
.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
MODELS INDICATE UPPER FLOW TO REMAIN SW...WHICH WOULD NOT ALLOW THE
FRONT TO GET A GOOD PUSH. IT APPEARS IT MAY STALL OFFSHORE...WITH
SOME DRIER AIR MOVING IN THU...WITH A WEAK SURFACE RIDGE OF HIGH
PRESSURE TO OUR NORTH. MODELS ARE TRENDING A LITTLE EARLIER WITH
SOME RETURNING MOISTURE BY LATE FRIDAY. LATEST GFS/ECMWF/CANADIAN
MODEL RUNS ALL SEEM TO SUGGEST A LOW DEVELOPING AND MOVING ACROSS
CENTRAL FLORIDA IN VARYING DEGREES SATURDAY AND MOVING NE. THOUGH
MAIN MOISTURE PLUME AND ANY SURFACE LOW TRACK TO REMAIN TO OUR
SOUTH...SOME MOISTURE COUPLED WITH LIFT FROM UPPER TROUGH COULD
PRODUCE SOME PRECIPITATION. WILL FOLLOW LATEST GFS ENSEMBLE
AVERAGE POP WHICH GENERALLY PROVIDES A SLIGHT CHANCE POP FROM LATE
FRIDAY THROUGH SATURDAY.
&&
.LONG TERM /SUNDAY THROUGH TUESDAY/...
GFS/ECMWF BRING IN SURFACE HIGH PRESSURE FOR SUN/MON...AND
REDEVELOPS A SW UPPER FLOW WITH RETURING MOISTURE FOR TUE/WED TIME
FRAME.
&&
.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
AN INCREASE IN ISENTROPIC LIFT AND MOISTURE AHEAD OF THE STRONG LOW
PRESSURE SYSTEM WILL RESULT IN LOWERING CEILINGS AND VISIBILITIES
DURING THE TAF PERIOD. USED AN AVERAGE OF THE GFS MOS...LAMP...NAM
MOS AND SREF FOR THE TIMING OF MVFR AND IFR. SURFACE DEW POINT
TEMPERATURES IN THE 30S INDICATE THE WEDGE RIDGE PATTERN WILL
PERSIST THROUGH THE EARLY PART OF THE TAF PERIOD AND RESULT IN
RELATIVELY LIGHT WINDS AT THE SURFACE WITH A SHARP INCREASE IN WINDS
ALOFT. BASED ON THE NAM HAVE INCLUDED LOW-LEVEL WIND SHEAR IN THE
FORECAST. EXPECT THE WARM FRONT WILL LIFT NORTH OF THE REGION LATE
WEDNESDAY AFTERNOON AND RESULT IN LESS WIND SHEAR...BUT STRONGER
GUSTY WINDS AT THE SURFACE. THUNDERSTORMS MAY OCCUR...BUT THE CHANCE
APPEARS TOO LOW TO INCLUDE IN THE FORECAST AT THIS TIME.
ANOTHER LOW PRESSURE SYSTEM MAY BRING WIDESPREAD MVFR OR IFR
CONDITIONS SATURDAY.
&&
.HYDROLOGY...
BOTH GFS AND NAM...AS WELL AS THE AVERAGE TOTAL RAINFALL
AMOUNT FROM THE SHORT RANGE ENSEMBLE PLUME DIAGRAM...PROJECT AROUND
TWO INCHES OF RAIN AT COLUMBIA. TWO INCHES OF RAIN ACROSS OUR CWA...
COUPLED WITH HEAVY RAIN UPSTREAM IN THE UPSTATE...COULD LEAD TO
RIVER FLOODING POTENTIAL. IT APPEARS THAT THE TIME WINDOW OF HIGHEST
PRECIPITABLE WATER VALUES AND WIDESPREAD PRECIPITATION WILL ONLY BE
AROUND 12 HOURS OF SO FOR OUR FORECAST AREA...REDUCING CONFIDENCE
OF AREAL FLOODING OUTSIDE RIVER FLOOD PLAINS. ALSO...NO TROPICAL
CYCLONE REMNANT OR CLEAR STRONG TROPICAL CONNECTION APPEARS
PRESENT. BLOB OF CONVECTION OVER THE NORTHERN GULF MAY ALSO ACT TO
CUT OFF FLOW OF THE MOST MOIST AND UNSTABLE AIR. SO...DECIDED NOT
TO ISSUE A FLASH FLOOD WATCH AT THIS TIME. LATEST FORECASTS FROM
THE RIVER FORECAST CENTER KEEP RIVER STAGES WELL BELOW FLOOD
STAGE. HOWEVER...INTERESTS NEAR OUR RIVER FORECAST POINTS SHOULD
BE AWARE THAT RIVER FLOODING MAY BE POSSIBLE OVER THE NEXT SEVERAL
DAYS.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...LAKE WIND ADVISORY FROM 1 PM THIS AFTERNOON TO 7 AM EST
THURSDAY FOR SCZ015-016-018-020>022-025>031-035>038-041.
GA...LAKE WIND ADVISORY FROM 1 PM THIS AFTERNOON TO 7 AM EST
THURSDAY FOR GAZ040-063>065-077.
&&
$$
