000
FXUS62 KFFC 172305 AAA
AFDFFC
AREA FORECAST DISCUSSION...UPDATED FOR AVIATION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
705 PM EDT SAT MAY 17 2008
.SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
HIGH AMPLITUDE PATTERN TO REMAIN IN PLACE FOR THE NEXT WEEK...AND
ACTUALLY AMPLIFIES EVEN FURTHER TOWARD THE END OF THE WEEK. POLAR
VORTEX DOMINATES THE EASTERN U.S. FOR THE NEXT SEVEN DAYS...WITH
A HIGH AMPLITUDE RIDGE ALIGNED ALONG THE WEST COAST. INITIAL
SPLIT FLOW...BASICALLY TWO WAVE PATTERN ACROSS THE U.S. WITH
POSITIVELY TILTED CUTOFF LOW WESTERN U.S...TRANSITIONS TO
3-WAVE...HIGH AMPLITUDE WESTERN U.S. TROUGH...CENTRAL U.S.
RIDGE...AND EASTERN U.S. TROUGH TOWARD THE END OF THE WEEK. FOR
THE SE U.S...NORTHWEST FLOW ALOFT WILL REMAIN IN PLACE THROUGH THE
WEEK. WHILE OVERALL A DRY PATTERN FOR THE SE U.S...A SERIES OF
DISTURBANCES OR SHORT WAVES...WITH ASSOCIATED POCKETS OF COLD AIR
ALOFT...ROTATING AROUND THE DEEP UPPER LOW IN THE NE U.S...WILL
PROVIDE SUFFICIENT INSTABILITY ALOFT TO SUPPORT SMALL CHANCES FOR
SHRA AND POSSIBLY EVEN TSRA DURING MAX DAYTIME HEATING HOURS. THE
FIRST THREAT FOR SUCH COMES SUNDAY AFTERNOON/EVENING. SFC MOISTURE
LIMITED...SO MAINLY EXPECTING SHRA WITH THIS FIRST SYSTEM...BUT
GIVEN POCKET OF -16C AT 500MB NEAR THE TN BORDER...CANNOT RULE OUT
ISOLD TSRA. WITH BROAD UPPER RIDGING DEVELOPING ACROSS THE GULF
EXPECT ACTIVITY TO BE CONFINED TO THE NORTHERN COUNTIES...WITH A RESULTANT
TIGHT GRADIENT OF POPS FROM NORTH TO SOUTH...NAMELY GOOD CHANCE
POPS NORTH TO NEAR ZERO POPS SOUTH. THIS FIRST SYSTEM WILL PUSH A
SFC BOUNDARY TO NEAR THE TN/GA BORDER MON...WHICH WILL LINGER IN
THAT VICINITY...AND AWAIT THE NEXT IMPULSE ROTATING AROUND THE UPPER
LOW TO MAKE ANY FURTHER SOUTHWARD PROGRESS. WITH SLOWLY INCREASING
INSTABILITY AND MOISTURE ACROSS THE NORTH MON...CANNOT RULE OUT
ISOLD AFTERNOON/EVENING SHRA/TSRA NEAR THE FRONT...SO HAVE
INCLUDED LOW POPS FOR THAT AREA MON AFTERNOON. OTHERWISE...THE
SHORT TERM PERIODS SHOULD BE DRY. SHORT TERM MOS GUIDANCE APPEARS
REASONABLE AND ONLY MINOR CHANGES WERE MADE. MAIN CONCERN IS FIRST
PERIOD MINS. WITH SFC FLOW SW TONIGHT INSTEAD OF N AS IT WAS LAST
NIGHT...FEEL THAT MAV MOS IS TOO COLD...SO HAVE TRENDED TOWARD THE
SLIGHTLY WARMER MET MOS. GRANTED DEW POINTS REMAIN MOSTLY IN THE
40S...BUT INCREASING HIGH CLOUDS AND SW SFC FLOW SHOULD KEEP MINS
5-10 DEGREES WARMER TONIGHT. WILL NEED TO WATCH THOSE LOCATIONS
THAT DECOUPLE...SUCH AS FFC...FOR POTENTIALLY SIGNIFICANTLY
COOLER MINS.
.LONG TERM /TUESDAY THROUGH SATURDAY/...
BY TUE AFTERNOON...YET ANOTHER SHORT WAVE ROTATES AROUND THE
LARGE NE U.S. UPPER LOW. BY THIS TIME...DEWPOINTS HAVE RISEN TO
NEAR 60. INSTABILITY IS ALSO MORE NOTICEABLE...WITH CAPES RISING
TO NEAR 1000 IN THE NW/WC AREAS AND LIS DROPPING TO -2. THUS...THE
THREAT FOR TSRA APPEARS TO BE GREATER WITH THIS SECOND SYSTEM.
HOWEVER...WE ARE ONCE AGAIN JUST BEING BRUSHED BY THE SYSTEM AS
THE MAIN DYNAMICS ARE SHUNTED INTO NC. HAVE ADVERTISED CHANCE POPS
NORTH TO SLIGHTLY CHANCE POPS CENTRAL TUE AFTERNOON/EVE. THIS
SECOND SYSTEM WILL PUSH THE INITIAL WEAK SFC BOUNDARY FURTHER SOUTH
INTO CENTRAL GA WHERE IT IS LEFT LINGERING AS A FOCUSING MECHANISM
FOR ADDITIONAL CONVECTION INTO THE EXTENDED PERIODS AS
DISTURBANCES IN NW FLOW ALOFT CONTINUE TO TRAVERSE THE
AREA...ESPECIALLY AS THE LOWER ATMOSPHERE BECOMES INCREASINGLY
MOIST AND UNSTABLE INTO MID-WEEK/LATE WEEK. NONETHELESS...THERE IS
NOTHING OVERLY EXCITING ABOUT THE EXTENDED PERIODS. IN FACT...THE ATTEMPT
TO TRANSITION FROM SPRING TO SUMMER IS QUITE EVIDENT IN THE
EXTENDED. THE FIRST SIGN OF A STRONG SUBTROPICAL SUMMER RIDGE
BECOMES QUITE APPARENT BY THE WEEKEND...ALBEIT AN EXTREMELY HIGH
AMPLITUDE PATTERN REMAINS IN PLACE WITH A TROUGH...RIDGE...TROUGH
PATTERN. THE EXACT LOCATION OF THE RIDGES AND TROUGHS ALWAYS
SUSPECT WITH A HIGH AMPLITUDE/BLOCKING PATTERN THAT FAR OUT...BUT
THE ECMWF CONFIRMS THE GFS`S SOLUTION THAT THE SE U.S. WILL MOST
LIKELY REMAIN UNDER NW FLOW ALOFT...AS THE DEEP POLAR VORTEX
SHIFTS ONLY SLIGHTLY FURTHER EAST AND A STRONG UPPER RIDGE
AMPLIFIES JUST TO THE WEST...ACROSS THE MID-SOUTH. THE SFC AIR
MASS BECOMES INCREASINGLY SUMMER LIKE WITH 70 DEWPOINTS SPREADING
INTO THE MID MISSISSIPPI VALLEY REGION JUST TO OUR WEST. DIURNALLY
DRIVEN CONVECTION SHOULD BE ON THE INCREASE AND NW FLOW ACROSS OUR
REGION SHOULD HELP ENHANCE THIS ACTIVITY...AT LEAST DURING THE
FIRST PART OF THE EXTENDED AS WEAK SHORT WAVES ROTATED OVER THE
UPPER RIDGE AND DOWN THE WEST SIDE OF THE POLAR VORTEX INTO THE SE
U.S. THE 12Z GFS...SHOWING CONSIDERABLE AMPLIFICATION OF THE
PATTERN TOWARD DAY 7...PUSHES THE BEST MOISTURE AND INSTABILITY
BACK INTO THE MID-SOUTH AND TRIES TO SHOW SOME DRYING AND COOLING
INTO GA FROM THE NE. AGAIN...ALL SUBJECT TO THE EXACT SETUP OF
TROUGHS AND RIDGES AT THAT POINT. FOR NOW...HAVE ADVERTISED MAINLY
DIURNAL POPS FOR FRI-SUN...WITH DRYING INTO NE GA BY SUN. 12Z MEX
MOS TEMPS NOTICEABLY COOLER THAN THE 00Z MEX...ESPECIALLY TOWARD
DAY 7...AS NORTHERLY FLOW ALOFT INTO THE SE U.S. MUCH STRONGER ON
LATEST 12Z GFS. HAVE TEMPERED MAX TEMPS JUST SLIGHTLY FROM THOSE
EARLIER INDICATED...REMOVING THE 90S THAT WERE ADVERTISED FOR
SOUTHERN AREAS. THE EXPECTED PATTERN SHOULD KEEP ANY EXTREME HEAT
TO THE WEST OF THE REGION.
&&
.FIRE WEATHER...
CRITICAL RH VALUES ARE BEING APPROACHED IN CENTRAL GA THIS
AFTERNOON...BUT WILL NOT MEET FOUR HOUR DURATION. DEWPOINTS ARE
EXPECTED TO INCREASE SLIGHTLY SUNDAY...AND CONTINUE INCREASING
INTO EARLY NEXT WEEK. THUS...CRITICAL RH CONDITIONS ARE NOT
EXPECTED TO BE MET NEXT 48-72 HOURS. STRONGER WEST WINDS PROGGED
ACROSS THE NORTH SUN AND MON AFTERNOON SHOULD ALSO REMAIN BELOW
CRITICAL THRESHOLDS. THUS...NO RFW PLANNED AT THIS TIME FOR THIS PACKAGE.
&&
.AVIATION...
CIRRUS WILL BE ON THE INCREASE OVERNIGHT AS UPPER LEVEL SHORT WAVE
PASSES BY. LOWER LEVELS SHOULD REMAIN DRY. SURFACE DEWPOINTS LOOK
LOW ENOUGH TO PRECLUDE FOG. SURFACE FRONT PUSHING INTO NORTH GEORGIA
SUNDAY SHOULD BRING ENOUGH MOISTURE AND LIFT FOR SCATTERED TO BROKEN
CLOUDS AT 5 TO 6 THOUSAND FEET FOR THE NORTHERN AIRPORTS. CENTRAL
GEORGIA AIRPORTS MAY SEE NOTHING LOWER THAN SCATTERED ALTOCUMULUS
AROUND 10 THOUSAND. BY MIDDAY WINDS WILL BE ON THE INCREASE AND
BECOMING GUSTY AS PRESSURE GRADIENT TIGHTENS AND MIXING DEPTH
INCREASES.
&&
.PRELIMINARY POINT TEMPS/POPS...
ATHENS 54 80 54 82 60 / 5 20 20 10 20
ATLANTA 57 77 56 79 64 / 5 20 20 10 10
BLAIRSVILLE 49 72 48 70 56 / 10 40 10 20 30
CARTERSVILLE 51 77 50 78 58 / 10 30 10 10 20
COLUMBUS 59 81 60 85 68 / 5 10 10 10 10
GAINESVILLE 56 76 54 76 60 / 10 30 20 10 20
MACON 55 81 58 83 65 / 0 10 10 10 10
ROME 52 77 52 80 61 / 10 30 10 10 20
PEACHTREE CITY 50 78 54 80 59 / 5 20 10 10 10
VIDALIA 59 82 60 84 64 / 5 10 10 10 10
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
19/15
