FXUS62 KFFC 092256 AAA AFDFFC AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PEACHTREE CITY GA 655 PM EDT WED JUL 9 2014 .UPDATE... SCATTERED THUNDERSTORMS WILL OCCUR MAINLY OVER CENTRAL GA ALONG AND SOUTH OF A WEAK FRONTAL BOUNDARY FROM FRANKLIN THROUGH CONYERS TO ATHENS THIS EVENING. AN UPPER LEVEL DISTURBANCE CONTINUES TO TRIGGER ADDITIONAL SCATTERED THUNDERSTORMS OVER EXTREME NORTH GA FROM TRENTON TO DALTON. THE STORMS WILL GENERALLY MOVE EAST AT 15 KTS BEFORE DISSIPATING BY MIDNIGHT. THE POPS OVER THE ATLANTA METRO AREA HAVE BEEN LOWERED INTO THE 30-40 PERCENT RANGE AND ALL OF NORTH GA WILL DROP TO AROUND 20 PERCENT AFTER MIDNIGHT. 16/39 .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/... COLD FRONT IS PUSHING INTO NORTHWEST GEORGIA AT AFD TIME...WITH A LINE OF CONVECTION ROUGHLY FROM ATHENS TO THE SOUTH SIDE OF ATLANTA ALONG A WEAK SURFACE CONVERGENCE ZONE AND DIFFERENTIAL HEATING BOUNDARY /FROM MIDLEVEL CLOUDS UP NORTH/. DEEP UPPER TROUGH REMAINS IN PLACE OVER THE EASTERN PORTION OF THE COUNTRY BUT WILL BEGIN TO LIFT TOWARD THE END OF THE SHORT TERM...WITH THE FRONT PROGGED TO LINGER ACROSS CENTRAL GEORGIA THROUGH THURSDAY. CONCERN FOR THIS EVENING WILL BE MAINLY ABOUT CONVECTION...NAMELY COVERAGE AND INTENSITY. EXPECT CHANCES TO REMAIN PRETTY HIGH AS DEEP LAYER MOISTURE HAS INCREASED AHEAD OF THE FRONT. BUFR SOUNDINGS REMAIN FAIRLY SATURATED THROUGH THE EVENING AND OVERNIGHT HOURS AND WITH PLENTIFUL SBCAPE...IT IS MAINLY JUST A MATTER OF WHERE CONVECTION WILL BE ABLE TO GET GOING. CANNOT RULE OUT ISOLATED SEVERE STORMS WITH MARGINALLY SEVERE HAIL AS THE MAIN THREAT. DCAPE VALUES ARE BETWEEN 1000-1300 J/KG ACROSS NORTH GEORGIA AND ALSO ACROSS PORTIONS OF CENTRAL GEORGIA...WITH AREAS FROM METRO ATLANTA TO ATHENS TOO LOW FOR MUCH CONCERN. NEW TRENDS IN RAP DATA KEEP THE HIGH DCAPE VALUES IN PLACE DOWN SOUTH BUT DIMINISH THEM UP NORTH THROUGH THE AFTERNOON...SO BEST CHANCE FOR MARGINAL SEVERE WOULD LIKELY BE ACROSS PORTIONS OF CENTRAL GEORGIA. WIDESPREAD CLOUD COVER AND PLENTIFUL SURFACE MOISTURE WILL KEEP HIGH TEMPS TOMORROW A FEW DEGREES LOWER THAN NORMAL...WITH NEAR-NORMAL LOWS. TDP .LONG TERM /FRIDAY THROUGH WEDNESDAY/... LONG WAVE TROUGH TO CONTINUE TO FILL OVER ERN CONUS FRI THRU SUN WHILE E-W ORIENTED RIDGE ALOFT BUILDS OVER SRN STATES. SHOULD SEE WARMING TEMPS AND LOWER POPS IN THIS PATTERN. ISOLD SHRA/TSRA STILL LIKELY BUT LESS COVERAGE THAN PREVIOUS DAYS. LARGE UPPER VORTEX AND TROUGH PROGGED BY 12Z MED RANGE MODELS TO SWING SOUTH FROM CANADA INTO ERN CONUS AGAIN MONDAY WITH PERIPHERY OF WESTERLIES AND WEAK FRONT DIPPING INTO GA ON TUES. EXPECT RETURN TO HIGHER POPS AND SLIGHTLY COOLER TEMP TUES/WED. MADE ONLY SMALL MODIFICATIONS TO POPS/WX AND TEMPS WITH MODEST ADJUSTMENTS TOWARD HPC GUIDANCE. SNELSON PREV LONG TERM DISCUSSION... /ISSUED 148 PM EDT WED JUL 9 2014/ /VALID THURSDAY NIGHT THROUGH TUESDAY/... THURSDAY AND FRIDAY....EXTENDED PERIOD BEGINS WITH EASTERN US TROF CENTERED NEAR 85 WEST AND REMNANT FRONTAL BOUNDARY DRAPED ACROSS CENTRAL GA. BOTH THE ECMWF AND GFS IN GOOD AGREEMENT WITH BOTH THE LOCATION OF THE FRONT AND DEPTH OF THE EASTERN TROF. END RESULT IS MOSTLY DIURNAL CONVECTION PARTICULARLY NEAR THE BOUNDARY ALONG AND SOUTH OF I85 WITH BEST CHANCES ON THURSDAY. MODEL CAPE VALUES ARE MODEST AND TYPICAL FOR SUMMERTIME PATTERN...HOWEVER PRECIPITABLE WATER VALUES PEAK ACROSS THE AREA ON THURSDAY BETWEEN 1.8 AND 2.0 INCHES WHICH COULD RESULT IN SOME EFFICIENT RAIN PRODUCING STORMS. DRIER AIR WORKS IN BEHIND THE FRONT ON FRIDAY SQUASHING THE BEST RAIN CHANCES TO THE SOUTH AND EAST PORTION OF THE AREA...I.E. CSG TO MCN AND POINTS SOUTH NEAR THE REMNANT FRONT. WEEKEND...THE GENERAL PATTERN PERSISTS INTO THE WEEKEND ACROSS THE EASTERN U.S. WITH THE TROF AXIS SHIFTING SLIGHTLY EAST OF GA BY SATURDAY AND SOME MID LEVEL RIDGING TRYING TO NOSE IN FROM THE WEST...WHILE THE REMNANT FRONT IS ALL BUT A DISTANT MEMORY. END RESULT WILL BE NEAR TO SLIGHTLY BELOW CLIMO POP CHANCES BOTH SATURDAY AND SUNDAY. CAVEAT HERE IS THAT PW VALUES SOAR UP TO NEAR OR SLIGHTLY ABOVE 2.0 INCHES MAKING FOR A MUGGY WEEKEND. STILL THINK THE GREATEST CHANCES WILL BE SOUTH AND EAST CLOSER TO WHERE SEA BREEZE ACTIVITY HAS THE BEST INFLUENCES LATE IN THE AFTERNOON. MONDAY AND TUESDAY...GFS AND ECMWF SLIGHTLY DIFFERENT BUT STILL GENERALLY AGREE THAT THE LARGER SCALE TROF WILL BE REINFORCED ACROSS THE REGION WITH ANOTHER FRONT APPROACHING. END RESULT WILL BE INCREASED POP CHANCES ON MONDAY AND PARTICULARLY TUESDAY. MUCH CAN HAPPEN BETWEEN NOW AND THEN SO WILL TREND HIGHER BUT NOT GO OVERBOARD. STELLMAN && AVIATION... 18Z UPDATE... VFR CONDITION THIS AFTERNOON WITH CONVECTION STARTING TO FIRE. HAVE GONE PREVAILING SHRA EVERYWHERE WITH TEMPO TSRA STARTING 20Z AND WILL REFINE AS NECESSARY. CONVECTION MAY LINGER OVERNIGHT SO ADDED VCSH THROUGH 06Z. EXPECT MVFR CIGS TO DEVELOP OVERNIGHT... LIFTING ON THURSDAY WITH ADDITIONAL CONVECTION POSSIBLE SO INTRODUCED PROB30 STARTING AT 15Z. WINDS GENERALLY W THROUGH THE PERIOD WITH LOW-END GUSTS THIS AFTERNOON. //ATL CONFIDENCE...18Z UPDATE... MEDIUM ON TIMING OF CONVECTION THIS AFTERNOON AND CIGS TONIGHT. HIGH ON ALL OTHER ELEMENTS. TDP && .PRELIMINARY POINT TEMPS/POPS... ATHENS 70 89 69 91 / 60 50 30 30 ATLANTA 71 86 71 89 / 60 40 30 20 BLAIRSVILLE 64 82 63 84 / 60 30 20 20 CARTERSVILLE 68 86 67 89 / 60 30 20 20 COLUMBUS 73 90 73 92 / 50 60 30 30 GAINESVILLE 70 85 69 88 / 60 40 30 20 MACON 71 90 70 91 / 40 60 40 30 ROME 69 87 67 90 / 60 30 20 10 PEACHTREE CITY 69 87 68 89 / 60 40 30 20 VIDALIA 73 92 73 90 / 20 60 50 60 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...TDP LONG TERM....SNELSON AVIATION...TDP
Posted on: Wed, 09 Jul 2014 22:56:39 +0000