085
FXUS62 KFFC 210244 AAA
AFDFFC
AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
930 PM EST FRI NOV 20 2009
UPDATE
NOT MANY CHANGES NEEDED FOR THE OVERNIGHT PERIOD. INCREASING HIGH
CLOUDS AS INTENSIFYING...VIGOROUS SHORT WAVE LIFTS OUT OF SOUTH TX.
THIS IS A RATHER TYPICAL SYSTEM FOR AN EL NINO TYPE PATTERN.
GFS/ECMWF CONTINUE TO DIFFER ON TIMING...WITH ECMWF HOLDING OFF ON
BRINGING RAIN INTO THE CWA UNTIL LATE SAT. ECMWF HAS GENERALLY BEEN
VERIFYING BETTER RECENTLY. HAVE BACKED OFF ON POPS FOR FIRST THREE
PERIODS AND INCREASED POPS FOR NEXT THREE PERIODS BASED ON SLOWER
ECMWF SOLUTION. QPF STILL IN QUESTION...BUT LATEST HPC GUIDANCE
SUGGESTS 2.0+ INCHES ACROSS CENTRAL PORTIONS OF CWA AND 1.0-1.5
INCHES NORTH. INCREASING CONCERNING FOR AT LEAST MINOR
FLOODING...BUT VALUES REMAIN BELOW 6 HR FFG VALUES OF 3 INCHES NORTH
TO 4.5 INCHES SOUTH. EARLIER SPS HIGHLIGHTS CONCERNS FOR
FLOODING...ESPECIALLY SINCE IT HAS ONLY BEEN A WEEK SINCE THE LAST
FLOOD EVENT. FLOOD WATCH MAY BE NEEDED IF LATER MODEL RUNS CONTINUE
TO SHOW HIGHER QPF FROM SLOWER MOVING/MORE INTENSE SYSTEM. HEAVIEST
RAIN SHOULD FALL SE OF A CSG-MCN-AGS LINE AS MODELS IN GENERAL
AGREEMENT IN TRACKING SFC LOW ACROSS S GA. THERE IS ALSO SOME
CONCERN FOR TSRA IN OUR SOUTHERN ZONES. 18Z GFS AGREES WITH CURRENT
THINKING...HOWEVER...KEEPING TSRA THREAT JUST SOUTH OF THE CWA.
NONETHELESS...SOME TSRA THREAT 00Z-18Z SUN ACROSS OUR SE
COUNTIES...BUT WILL SHOW JUST SE OF CWA FOR NOW. AGAIN...MAIN
CONCERN WILL BE HEAVY RAIN ON SATURATED SOIL.
19
PREVIOUS FORECAST DISCUSSION ISSUED 525 PM EST FRIDAY
SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/
SURFACE HIGH PRESSURE AND WEAK SOUTHWEST FLOW ALOFT WILL KEEP THE
AREA DRY TONIGHT AND EARLY SATURDAY. STRONG WAVE MOVING OFF THE
SOUTHERN ROCKIES WILL DEVELOP AN ATTENDANT SURFACE LOW ALONG THE
TEXAS GULF COAST...AND LATENT HEAT RELEASE WILL ALLOW THE LOW TO
STRENGTHEN SOMEWHAT OVER THE NEXT DAY OR SO. GFS IS THE FASTEST OF
THE SHORT-TERM MODELS WITH BRINGING THE LOW EAST ALONG THE
COAST...AND ALLOWING MOISTURE TO OVERSPREAD THE SOUTHEAST. HAVE
LEANED MORE TOWARD A COMPROMISE AS THE ECMWF IS THE SLOWEST...AND IS
EVEN SLOWER ON THE LATEST 12Z RUN. IN THE MEANTIME...THE SURFACE
HIGH SLIDES EAST ACROSS THE OHIO VALLEY AND WILL BEGIN RIDGING DOWN
THE EASTERN SLOPES OF THE APPALACHIANS IN A HYBRID DAMMING EVENT
BEGINNING TOMORROW. THIS WILL KEEP TEMPERATURES NOTICEABLY COOLER
SATURDAY AND ESPECIALLY SUNDAY UNDER ALL THE CLOUD COVER...AND WILL
ENHANCE THE AVAILABLE LIFT FOR THE MOISTURE FROM THE COASTAL LOW. DO
NOT EXPECT SIGNIFICANT HEAVY RAINFALL...BUT DO EXPECT WIDESPREAD
LIGHT TO OCCASIONALLY MODERATE RAINFALL BETWEEN LATE SATURDAY AND
SUNDAY...WITH BEST CHANCES SATURDAY NIGHT. OVERALL RAINFALL ANYWHERE
BETWEEN 1-2". THE LOW BEGINS TO FILL IN LATE IN THE SHORT
TERM...UNLESS YOU BELIEVE THE NAM WHICH LINGERS IT NEAR LOUISIANA.
BY THE END OF THE PERIOD THE MOISTURE BEGINS TO MOVE OUT AS THE NEXT
WAVE IN PLAINS KICKS THE COASTAL SYSTEM TOWARD THE NORTHEAST.
LONG TERM /MONDAY THROUGH FRIDAY/
AFOREMENTIONED WAVE COMING OFF THE ROCKIES EARLY IN THE WEEK
DEVELOPS INTO A CLOSED LOW OVER THE CENTRAL PLAINS MONDAY INTO
TUESDAY. ATTENDANT FRONT NOT ESPECIALLY IMPRESSIVE...AT LEAST
INITIALLY... DUE TO LACK OF MOISTURE RETURN BEHIND THE WEEKEND
SYSTEM. GFS FASTER...SLIGHTLY DEEPER...AND FURTHER NORTHEAST WITH
THE LOW AND COLD FRONT...BRINGING THE WEAK REMNANTS OF THE FRONT
THROUGH TUESDAY NIGHT...WITH HARDLY MORE THAN AN INCREASE IN CLOUD
COVER INDICATED FOR OUR AREA. ECMWF HAS A VASTLY DIFFERENT
SOLUTION...ALLOWING MORE MOISTURE RETURN WITH THE SLOWER SYSTEM.
IT BRINGS WIDESPREAD MOISTURE TO THE SOUTHEAST DURING THE DAY ON
WEDNESDAY...LINGERING THROUGH EARLY THURSDAY. CONFIDENCE EXTREMELY
LOW TOWARD MIDWEEK. ABOUT THE ONLY THING BOTH MODELS ARE AGREEING
ON IS THE GENERAL TROUGHINESS THAT WILL BE OVER THE EASTERN THIRD
OF THE COUNTRY...BUT EVEN THEN THE GFS INDICATING A MUCH DEEPER
AND COLDER TROUGH. WILL LEAVE THE EXTENDED AS IS FOR NOW WITH ONLY
SLIGHT CHANCE POPS NORTH ON TUESDAY AS THE GFS WOULD INDICATE...
BUT WOULD NOT BE A BIT SURPRISED TO SEE THE ECMWF VERIFY (IT'S
BEEN DOING A MUCH BETTER JOB AT HANDLING THE SYSTEMS COMING
THROUGH LATELY).
25
AVIATION
VFR THROUGH THE FORECAST...EXCEPT AFTER 00Z SUN IN ATL WHEN THE RAIN
WILL BECOME MORE WIDESPREAD AND MVFR CIGS WILL ENTER THE AREA.
EXPECT HIGH CLOUDS THROUGH SATURDAY MORNING WITH MID LEVEL MOISTURE
MOVING IN DURING THE LATE MORNING/AFTERNOON. THERE IS A CHANCE OF
RAIN AFTER 21Z IN THE ATL/CSG/MCN AREAS AND WILL ADD A PROB30 TO
THOSE LOCATIONS AFTER 21Z. WINDS WILL REMAIN NORTHEAST LESS THAN 10
KTS THROUGH SATURDAY AFTERNOON.
17
PRELIMINARY POINT TEMPS/POPS
ATHENS 43 62 47 52 44 / 0 30 90 90 40
ATLANTA 46 61 48 54 46 / 0 40 90 70 30
BLAIRSVILLE 37 57 43 50 42 / 0 20 80 80 40
CARTERSVILLE 39 60 47 53 45 / 0 30 90 60 30
COLUMBUS 45 60 51 62 47 / 0 50 90 50 20
GAINESVILLE 44 61 46 50 44 / 0 30 90 80 40
MACON 44 64 51 62 46 / 0 40 90 70 20
ROME 39 61 47 56 45 / 0 30 80 60 40
PEACHTREE CITY 39 61 47 56 43 / 0 40 90 60 30
VIDALIA 44 66 53 63 50 / 0 20 90 80 30
FFC WATCHES/WARNINGS/ADVISORIES
NONE.
25/17/19
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