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Area Forecast Discussion

750
FXUS62 KGSP 221805
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
205 PM EDT FRI AUG 22 2014

.SYNOPSIS...
A BROAD UPPER LEVEL RIDGE OF HIGH PRESSURE WILL CONTINUE TO BRING
VERY WARM TEMPERATURES TO MUCH OF THE REGION INTO SATURDAY. A BACK
DOOR COLD FRONT WILL THEN PUSH INTO THE AREA FROM NORTHEAST USHERING
IN COOLER TEMPERATURES STARTING SUNDAY. TEMPERATURES WILL GRADUALLY
RETURN TO NORMAL THROUGH NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 150 PM EDT...WATER VAPOR IMAGERY SHOWS CONVECTION DEVELOPING
ALL AROUND THE RING OF FIRE THAT STRETCHES FROM KANSAS TO IL TO WEST
VIRGINIA AROUND THE STRONG CENTRAL CONUS RIDGE. LITTLE TO NO UPPER
LEVEL TRIGGERING HAS BEEN PRESENT IN OUR FORECAST AREA...AND IT MAY
TAKE A RUN FROM AN UPSTREAM MCS SEGMENT TO PRODUCE MUCH COVERAGE.
THE AMPLIFYING UPPER RIDGE IS COOPERATING IN THIS REGARD BY TURNING
DEEP LAYER STEERING FLOW MORE NWLY TO NRLY WITH TIME. IN ADDITION...
DECENT HEATING ALONG AND SOUTH OF THE INTERSTATE 40 CORRIDOR...ALONG
WITH DEWPOINTS PERSISTING IN THE UPPER 60S IN MOST LOCATIONS...HAS
GENERATED SFC BASED CAPE VALUES OF NEARLY 3000 J/KG TO HELP PRIME
THE AREA. THE BEST CONSENSUS OF SOLUTIONS IS AN MCS RUNNING SE FROM
KY TO REACH OUR FORECAST AREA CLOSE TO 00Z AND TRANSITING A PORTION
OF THE REGION N TO S BEFORE DISSIPATING BY AROUND 06Z. WILL THUS
FEATURE HIGH CHANCE TO NEAR LIKELY NRN TIER POPS FOR THE
EVENING...AND DIMINISH SWD...WITH JUST LINGERING WRN NC POPS FOR ANY
ADDITIONAL WEAK OVERNIGHT ACTIVITY IN THE NW STEERING FLOW. EXPECT
SULTRY MINS IN THE UPPER 60S IN THE MTN VALLEYS TO LOWER 70S EAST.

A BACKDOOR FRONTAL BOUNDARY WILL MAKE STEADY PROGRESS IN OUR
DIRECTION FROM THE NE ON SAT...BUT WITH ANY REAL THICKNESS FALLS
DELAYED UNTIL AFTER THE NEAR TERM PERIOD. NRLY FLOW AND MORE CLOUDS
WILL ALLOW MAX TEMPS TO FALL A COUPLE OF DEGREES OR MORE DESPITE THE
CONTINUED WARM LOW LEVEL THICKNESSES. ANOTHER RUN OF ORGANIZED
CONVECTION WILL BE POSSIBLE SAT AFTN AS ACTIVITY MOVES SOUTHEAST
ALONG THE BACKDOOR FRONT. IN ADDITION...PRECIPITABLE WATER WILL POOL
ABOVE 2 INCHES ACROSS THE REGION BY SAT AFTN. HOWEVER...THERE SHOULD
BE ENOUGH NRLY STEERING FLOW TO KEEP THE HEAVIER RAIN ELEMENTS
MOVING. ANY TRAINING OF THUNDERSTORMS WOULD BE THE PRIMARY HYDRO
CONCERN SAT AFTN. LAPSE RATES WILL ACTUALLY BE STEEPER IN SW
SECTIONS...BUT THE COVERAGE MIGHT BE BETTER IN THE NRN TIER CLOSER
TO THE FORCING AND WEAK MCS TRACKS. SHOTGUN PM CHANCES POPS SEEMS
REASONABLE THROUGHOUT.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 1245 PM FRIDAY...THE INHERITED MAGNITUDE OF THE EXPECTED
COOLDOWN FOR SUNDAY REMAINS ON TRACK WITH THE EXPECTATION OF SFC
RIDGE BUILDING SWWD IN THE CWFA. ACCOMPANYING LLVL EASTERLY FLOW
CONTINUES TO PROMISE UNSETTLED WX...ESPECIALLY ACRS THE MTNS/FTHLS
WHERE THE INSTABILITY WILL BECOME INCREASINGLY CONFINED TO. AN
INFLUX OF DRIER AIR...FROM NE TO SW ACRS THE REGION...IS PROGGED FOR
SUNDAY NIGHT AND PRECIP CHANCES WILL WANE ACCORDINGLY. DEEPER
LAYERED RIDGING AND DRY AIR ATOP THE CWFA SHOULD PROVIDE QUIET WX
CONDITIONS WITH MAX TEMPERATURES SVRL CATEGORIES BELOW CLIMO ON
MONDAY. CLOSER TO THE LLVL RIDGE PERIPHERY...SLIGHT CHANCES FOR
DIURNAL DEEP CONVECTION WILL BE CONFINED TO THE SW NC/N GA MTNS.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
AS OF 3 AM FRIDAY...MONDAY THROUGH WEDNESDAY...MEDIUM RANGE GUIDANCE
INDICATES THAT MID LEVEL RIDGING AND SFC HIGH PRESSURE WILL BUILD
ACROSS THE CWA. GFS FORECAST SOUNDING THROUGH THE PERIOD SHOWS A
PERSISTENT LAYER OF DRY AIR...YIELDING LITTLE TO NO INSTABILITY. I
WILL FORECAST A DRY PERIOD ACROSS THE CWA...WITH ISO CONVECTION
LIMITED TO THE MTNS. HIGH TEMPERATURES ON MON WILL RANGE AROUND 5
DEGREES BELOW NORMAL...RECOVERING TO NEARLY NORMAL BY WEDNESDAY. ON
THURSDAY...MODELS TIME A COLD FRONT ACROSS THE SOUTHERN APPALACHIANS
DURING THE DAYLIGHT HOURS. RETURN FLOW SHOULD RESULT IN BUILD
MOISTURE AND LLVL DEWPOINTS. I WILL FORECAST CHC POPS FOR SHRA/TSRA
WITH NEAR NORMAL TEMPERATURES.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT...LITTLE TO NO ACTIVITY HAS BEEN OBSERVED ON RADAR THIS
AFTERNOON...AND ANY PRECIPITATION MENTION GOING FORWARD WILL BE
ASSOCIATED WITH DECAYING MCS ACTIVITY ARRIVING FROM THE NW THIS
EVENING. SINCE THUNDER IS QUESTIONABLE DEPENDING ON HOW QUICKLY THE
SYSTEM DISSIPATES...WILL ADVERTISE ONLY VCSH AT THIS POINT.
OTHERWISE...EXPECT NW WINDS THIS AFTN TO TOGGLE WSW WITH WEAK LEE
TROUGHING THROUGH THE EVENING HOURS...RETURNING TO NW OR NRLY
OVERNIGHT INTO SAT. MAINLY SCT CUMULUS ARE EXPECTED EARLY...BUT WITH
MOISTURE INCREASING IN NRLY FLOW TO PERMIT VFR CIGS TO DEVELOP
TONIGHT AND PERSIST SAT WITH AN APPROACHING BACKDOOR COLD FRONT.

ELSEWHERE...SIMILAR TO KCLT...ALL EYES WILL BE ON CONVECTIVE
ACTIVITY DEVELOPING FROM TN TO ERN KY TO WV TO SEE WHAT CAN RUN INTO
OR NEAR THE TERMINAL FORECAST AREA THIS EVENING. IT STILL APPEARS
THE BEST CHANCE OF VCTS WILL RANGE FROM AS EARLY AS 22Z IN THE FAR
NRN TIER TO PERHAPS AS LATE AS 06Z IN FAR SRN SECTIONS. EXPECT
MAINLY NW FLOW IN WRN NC...TURNING MORE NRLY WITH TIME. WINDS MAY
BRIEFLY TOGGLE WSW OR SW IN THE UPSTATE WITH WEAK LEE
TROUGHING...BUT WITH A RETURN TOWARD NRLY OVERNIGHT INTO SAT.
MOISTURE WILL INCREASE IN THE NRLY FLOW THROUGH THE MORNING ON
SAT...WITH VFR CIGS LIKELY. ANY FOG AT KAVL SHOULD BE MVFR AT
WORST.

OUTLOOK...A BACKDOOR COLD FRONT WILL SAG INTO THE REGION THROUGH THE
WEEKEND...WITH CHANCES OF RESTRICTIONS INCREASING AT KHKY AND KAVL
THROUGH SUNDAY. A MORE DIURNAL PATTERN OF EARLY MORNING LOW
CLOUDS/FOG AND ISOLD AFTN TSTMS MAY RETURN EARLY NEXT WEEK...WITH
STEADY DRYING.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  94%     HIGH  97%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  97%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  97%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE
HOURLY EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE
FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JOH
NEAR TERM...HG
SHORT TERM...CSH
LONG TERM...NED
AVIATION...HG






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