Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 300522
AFDFFC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
122 AM EDT SAT MAY 30 2015



.UPDATE...
/ISSUED 857 PM EDT FRI MAY 29 2015/
MAIN FORECAST ISSUE FOR THE OVERNIGHT HOURS WILL BE WHEN/IF LOW
CLOUDS WILL DEVELOP ON THE EASTERLY FLOW ON PLACE. MODELS ARE IN
DISAGREEMENT ON WHETHER LOW CLOUDS WILL DEVELOP TONIGHT...AM NOT
CONFIDENT THAT CIGS WILL GO CLOUDY/OVERCAST...BUT DO SUSPECT SKIES
COULD BE AT LEAST PARTLY CLOUDY BY DAWN. HAVE MADE SOME MINOR
TWEAKS TO THE SKY GRIDS. ALSO...HAVE ADJUSTED THE HOURLY TEMP/DEW
GRIDS FOR CURRENT TRENDS.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
/ISSUED 316 PM EDT FRI MAY 29 2015/
ALTHOUGH THE CWA REMAINS IN THE SOUTHWEST FLOW THROUGH THE SHORT
TERM...THE UPPER LEVEL TROUGH DOES SLOWLY PUSH TOWARDS THE
EAST...MOVING THE TROUGH AXIS CLOSER TO GEORGIA. THIS WILL
EVENTUALLY BRING SOMETHING MORE CONCRETE TO KEY IN OFF OF FOR
PRECIPITATION...BUT THAT WILL NOT OCCUR UNTIL THE VERY END OF THE
SHORT TERM INTO THE LONG TERM. UNTIL THEN...ISOLATED TO SCATTERED
CONVECTION WILL CONTINUE EACH AFTERNOON FOR MUCH OF THE CWA.

DO EXPECT CONVECTION TO CONTINUE TO BE FOCUSED ACROSS NORTH GEORGIA
TODAY WITH STORMS DISSIPATING TONIGHT. FOR TOMORROW...HI-RES MODELS
ARE PICKING UP ON SEA BREEZE CONVECTION MAKING IT INTO THE SW
PORTION OF THE CWA. THIS DOES NOT PRECLUDE THE REST OF THE CWA FROM
CONVECTION BUT APPEARS THERE COULD BE A LULL IN ACTIVITY BETWEEN THE
SEA BREEZE AND CONVECTION TO THE NORTH AND WEST...HOWEVER HARD TO
PIN POINT WHERE THIS LULL WILL SET UP.

LOW TEMPERATURES TONIGHT WILL ONLY BE A FEW DEGREES WARMER THAN THIS
MORNING.

11

.LONG TERM /SUNDAY THROUGH FRIDAY/...
/ISSUED 316 PM EDT FRI MAY 29 2015/
12Z MODEL RUN SHOWING NO SIGNIFICANT DEPARTURES FROM RECENT TRENDS.
CURRENT EXTENDED FORECAST GRIDS COVER THIS WELL AND MINIMUM CHANGES
WERE MADE AT THIS TIME. PLEASE SEE THE PREVIOUS LONG TERM FORECAST
DISCUSSION BELOW.

20

PREV LONG TERM FORECAST DISCUSSION...

SATURDAY NIGHT THROUGH THURSDAY...

SYNOPSIS...00Z GFS AND ECMWF IN GENERAL PATTERN AGREEMENT AT THE
BEGINNING OF THE EXTENDED THROUGH MIDDAY MONDAY BEFORE DIFFERENCES IN
THE EVOLUTION OF A CUT OFF LOW OVER THE SOUTHERN MISSISSIPPI VALLEY
APPEAR.

SATURDAY AND SUNDAY...MEAN TROF THAT HAS BEEN ANCHORED OVER THE
WESTERN US FOR THE LAST MONTH IT SEEMS BEGINS SHIFTING EAST INTO THE
CENTRAL US WITH RIDGING BUILDING ACROSS THE WEST. GA WILL REMAIN
UNDER THE INFLUENCE OF UPPER RIDGING CENTERED OFF THE EAST COAST
PARTICULARLY SATURDAY AND WANING BY LATE SUNDAY AS THE TROF SHIFTS
EASTWARD ALONG WITH A WEAK SURFACE FRONT. BEST CHANCES FOR RAIN ON
THE WEEKEND WILL REMAIN GENERALLY CONFINED TO FAR NW GA SAT AND NORTH
AND WEST OF I85 ON SUNDAY AFTERNOON AND EVENING. LOOK FOR TYPICAL
AFTERNOON THUNDERSTORMS TO DEVELOP ACROSS THE AFOREMENTIONED REGIONS
EACH DAY.

MONDAY THRU THURSDAY...DIFFERENCES BEGIN TO APPEAR ON MONDAY BETWEEN
THE GFS AND ECMWF OVER THE EVOLUTION OF A CUTOFF LOW AS ENERGY RIDES
OVER THE DEVELOPING WESTERN RIDGE INTO THE BASE OF THE FAIRLY SHALLOW
TROF CENTERED OVER THE MS RIVER AT THAT TIME. OPERATIONAL GFS WANTS
TO CUT THE LOW OFF OVER LA WHICH PUTS OUR REGION ON THE MOIST FLOW
SIDE WITH A TAP INTO A MOISTURE PLUME FROM THE CARIBBEAN BY WED AND
MAKING FOR A MUCH WETTER WEEK. THE ECMWF ON THE OTHER HAND DELAYS THE
ONSET OF CUTTING THE LOW OFF UNTIL THE MEAN TROF GETS TO AROUND THE
85TH PARALLEL AND THUS CENTERING THE LOW OVER FLORIDA. THIS
DIFFERENCE PUTS OUR AREA ON THE DRIER NORTH SIDE OF THE LOW MID TO
LATE WEEK. GFS ENSEMBLE RESEMBLES THE OPERATIONAL GFS QUITE A BIT
MORE THUS MAKING THE ECMWF AN OUTLIER FOR NOW. CARRYING ABOVE CLIMO
POPS EACH DAY FOR NOW THAT WILL LIKELY NEED TO BE FINE TUNED EACH DAY
FOR NUANCES AS CONFIDENCE INCREASES. LOCALIZED FLOOD THREAT WILL
CERTAINLY BE ON THE TABLE EACH DAY AS PW VALUES...PER THE GFS...EACH
DAY THRU THURSDAY RANGE FROM 1.50 TO 1.75 INCHES ACROSS THE REGION
WHICH STATISTICALLY IS IN THE 90TH PERCENTILE. STAY TUNED TO THE
FORECAST FOR NEXT WEEK.

KS

&&

.AVIATION...
06Z UPDATE...
CURRENTLY VFR CONDITIONS AT ALL SITES...HOWEVER EXPECT
MVFR/POSSIBLY IFR CONDITIONS AT MCN/AHN LATER TONIGHT AS LOW
CLOUDS AND FOG DEVELOP OVER THESE AREAS. THE REMAINING SITES COULD
SEE A FEW-SCT MVFR CLOUDS BUT DO NOT EXPECT ANY CIGS IN THOSE
AREAS. CU FIELD WILL DEVELOP LATE THIS MORNING. AT THIS TIME
PRECIP IS NOT EXPECTED AT ANY OF THE TAF SITES. WINDS WILL REMAIN
LIGHT SOUTHEAST THROUGH SUNDAY.

//ATL CONFIDENCE...06Z UPDATE...
MEDIUM ON MVFR CLOUDS EARLY THIS MORNING.
HIGH ON REMAINING ELEMENTS.

17

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          85  67  86  67 /  20  20  40  30
ATLANTA         84  69  84  69 /  20  30  50  30
BLAIRSVILLE     79  62  79  62 /  20  40  60  40
CARTERSVILLE    85  66  84  66 /  20  40  60  30
COLUMBUS        88  69  88  69 /  10  20  40  40
GAINESVILLE     82  67  83  67 /  20  30  50  40
MACON           88  67  87  67 /  20  20  30  30
ROME            85  66  84  66 /  20  50  60  40
PEACHTREE CITY  85  66  85  66 /  20  30  40  40
VIDALIA         86  69  88  69 /  30  20  30  20

&&

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

$$

SHORT TERM...17
LONG TERM....30
AVIATION...17


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