Special Weather Statement, NWS Atlanta, GA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
737 PM EDT FRI AUG 23 2013

.UPDATE
HAVE ADJUSTED POPS ACROSS THE AREA...RAISING THEM ACROSS CENTRAL GA
AND ALSO OVER THE EXTREME NORTHWEST COUNTIES FOR CONVECTION MOVING
SOUTHWEST OUT OF TENNESSEE. NO OTHER CHANGES PLANNED.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...
/ISSUED AT 342 PM EDT FRI AUG 23 2013/
A MUCH QUIETER PATTERN IN STORE FOR THE NEXT FEW DAYS...FAR MORE
TYPICAL OF LATE FALL THAN WHAT WE HAVE BEEN SEEING...THAT SAID...
TEMPS WILL STILL REMAIN ON THE COOL SIDE AS A RESULT OF A BUILDING
DAMMING EVENT /LOOKS LIKE DRY ONSET CLASSICAL CAD BUT PRETTY
TRANSIENT/. SO FOR THE OVERALL PATTERN...STRONG TROUGHING ALONG THE
EASTERN SEABOARD...WITH SURFACE HIGH PRESSURE OVER THE GREAT LAKES
UNDER THE UPSTREAM CONFLUENT FLOW ALOFT...WILL GRADUALLY TRANSITION
EAST THROUGH THE WEEKEND. WEAK FRONT WILL PUSH INTO THE STATE THIS
EVENING...WORKING ITS WAY SOUTH TOWARD THE COAST TONIGHT AND EARLY
SATURDAY. IN THE WAKE OF THE FRONT...THE SURFACE HIGH WILL TRANSLATE
EAST AND BEGIN RIDGING DOWN THE EASTERN SEABOARD...AGAIN IN WHAT
LOOKS LIKE A DRY ONSET CLASSICAL CAD SCENARIO. WITH NO PRECIP
ASSOCIATED WITH THE CAD AT ONSET...SENSIBLE WEATHER IMPACTS WILL BE
MINIMIZED WITH THE EXCEPTION OF DRIER AIR MOVING AND AND THUS
SLIGHTLY COOLER TEMPS.

CONVECTION ALREADY FIRING ACROSS THE AREA AT AFD TIME WILL CONTINUE
TO SAG SOUTH THIS EVENING...MINIMIZING THE RISK OF FLASH FLOODING
WITH ANY INDIVIDUAL STORM. CONVECTION MAY LINGER THROUGH THE NIGHT
ACROSS SOUTHERN ZONES BUT THIS MAY BE A LITTLE HEAVY-HANDED. HAVE
BROUGHT CHANCE POPS BACK UP INTO THE METRO AREA ON SATURDAY BUT THIS
WILL HEAVILY DEPEND ON HOW FAR SOUTH THE FRONT PUSHES TONIGHT AND
TOMORROW AS WELL AS WHERE THE WEDGE FRONT SETS UP...AND HOW MUCH DRY
AIR PUSHES IN BEHIND IT. CERTAINLY BY SATURDAY NIGHT ENOUGH DRY AIR
HAS PUSHED IN TO WARRANT REMOVING POPS. KEPT TREND OF SLIGHT TO LOW
CHANCE POPS ACROSS EXTREME SOUTHERN ZONES ON SUNDAY.

TOOK A BIAS-ADJUSTED BLEND FOR TEMPS RESULTING IN GENERALLY MID 80S
TO NEAR 90 ON SATURDAY. GENERALLY ALL MOS GUIDANCE IS A COUPLE OF
DEGREES COOLER FOR SUNDAY AS A RESULT OF THE CAD BUT AM HESITANT TO
DROP TEMPS YET...AM NOT SURE HOW MUCH CLOUD COVER THERE WILL BE TO
LIMIT INSOLATION AND WE ARE STILL TALKING AUGUST SO SUN ANGLE STILL
HIGHER THAN EQUINOX TO CONTEND WITH. MAY SEE BIGGER IMPACTS INTO THE
BEGINNING OF THE EXTENDED AS THE SURFACE HIGH STRENGTHENS OVER THE
SOUTHEAST...EVEN WITH THE LOSS OF THE PARENT HIGH. OVERNIGHT LOWS
SHOULD BE INCREASINGLY PLEASANT WITH THE DRY AIR FILTERING IN.

TDP

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
/ISSUED AT 342 PM EDT FRI AUG 23 2013/
LONG TERM FORECAST STILL LOOKS GOOD. HAVE MADE ONLY ONE TWEAK AND
THAT WAS TO ADD SLIGHT CHANCE NORTHEAST WEDNESDAY NIGHT. LOOKS
LIKE ANOTHER BOUNDARY WILL BEGIN TO SLIDE SOUTHWARD AND APPROACH
THE NORTHEAST ZONES OVERNIGHT WEDNESDAY INTO THURSDAY MORNING.
UNTIL THEN...PRECIPITABLE WATER AMOUNTS DROPPING SIGNIFICANTLY
THROUGH THE WEEK AND THIS WILL SUPPORT MINIMAL POPS. MOISTURE
RETURNING BY THE END OF THE PERIOD. PREVIOUS DISCUSSION IS
INCLUDED BELOW.

41

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
/ISSUED 348 AM EDT FRI AUG 23 2013/
A COLD FRONT IS FORECAST TO MOVE S OF THE AREA SATURDAY EVENING AS
SURFACE HIGH PRESSURE BUILDS ALONG THE EASTERN SEABOARD AND UPPER
LEVEL HIGH PRESSURE BUILDS OVER THE MID U.S. SHOWER AND THUNDERSTORM
CHANCES SHOULD BE HIGHLY DIURNAL SATURDAY NIGHT AND DIMINISH WITH THE
LOSS OF HEATING. SHOWER AND THUNDERSTORM CHANCES LOOK TO BE LIMITED
TO MAINLY CENTRAL GA ON SUNDAY DURING THE AFTERNOON AND EARLY
EVENING HOURS WHERE THE BEST INSTABILITY IS EXPECTED TO BE WITH THE
INFLUENCE OF DRIER AIR AND HIGH PRESSURE HAVING THE MOST AFFECT ON N
GA.

PRECIP CHANCES FOR MONDAY AND TUESDAY LOOK TO BE AS LOW AS WE HAVE
SEEN IN A LONG TIME WITH A GENERALLY DRIER AIRMASS OVER THE AREA AND
THE INFLUENCE OF HIGH PRESSURE. GFS IS MORE AGGRESSIVE WITH PRECIP
AMOUNTS AND CHANCES THAN THE EUROPEAN. WILL NEED TO WATCH THE NE
MOUNTAINS AND FAR S AS AREAS WHERE SMALL CHANCES COULD BE NEEDED.

GFS MORE AGGRESSIVE WITH MOISTURE RETURN ON WEDNESDAY THAN THE
EUROPEAN FROM THE NNW FLOW ALOFT. GUIDANCE FROM HPC FAVORING LOW
POPS FOR N AND PORTIONS OF CENTRAL GA. A SURFACE TROUGH DEVELOPS
ACROSS THE AREA ON THURSDAY AND AGAIN THE GFS IS MORE AGGRESSIVE WITH
THE MOISTURE THAN THE EUROPEAN IN THE NNW FLOW ALOFT. HPC GUIDANCE
FAVORING LOW POPS ACROSS THE ENTIRE AREA DUE TO THE UNCERTAINTY.
BOTH MODELS INDICATING INCREASED MOISTURE OVER THE AREA ON FRIDAY.

TEMPERATURES GENERALLY RUNNING NEAR TO AROUND 6 DEGREES BELOW NORMAL
DURING THIS PERIOD.

BDL

&&

.AVIATION...
00Z UPDATE...
BAND OF TSRA FROM CSG TO MCN WILL SLOWLY SINK SOUTH OVER THE NEXT
COUPLE HOURS AND BY 02Z THEY SHOULD BE OUT OF THE TAF SITES. VFR
SKIES WILL PREVAIL THROUGH SATURDAY AFTERNOON/EVENING. EXPECT PATCHY
DENSE FOG TO DEVELOP ACROSS THE MCN AREA DUE TO SIGNIFICANT RAINFALL
THIS EVENING. SCATTERED TSRA SHOULD DEVELOP ACROSS THE FORECAST AREA
AFTER 18 TO 20Z SATURDAY AND HAVE ADDED A PROB30 FOR TSRA FOR ALL
SITES SATURDAY AFTERNOON.

//ATL CONFIDENCE...00Z UPDATE...
HIGH ON ALL ELEMENTS

17

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          69  85  67  84 /  30  30  20  10
ATLANTA         72  86  69  85 /  20  30  20  10
BLAIRSVILLE     64  80  64  81 /  20  30  10  10
CARTERSVILLE    68  87  68  87 /  20  20  20  10
COLUMBUS        73  89  71  88 /  30  30  20  30
GAINESVILLE     71  83  68  84 /  20  30  20  10
MACON           70  89  70  87 /  30  30  20  10
ROME            68  88  68  87 /  20  20  20  10
PEACHTREE CITY  68  86  67  86 /  20  30  20  10
VIDALIA         72  89  71  87 /  30  40  20  20

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SHORT TERM...TDP
LONG TERM....41
AVIATION...TDP