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Area Forecast Discussion

260
FXUS62 KGSP 191752
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
152 PM EDT SAT APR 19 2014

.SYNOPSIS...
A MOIST LOW PRESSURE SYSTEM WILL MOVE SLOWLY ACROSS SOUTHERN GEORGIA
TODAY...AND CONTINUE TRACKING EAST OFF THE SOUTH CAROLINA COAST
TONIGHT THROUGH SUNDAY. HIGH PRESSURE WILL BRIEFLY BUILD IN
MONDAY...BEFORE A COLD FRONT PUSHES ACROSS THE REGION ON TUESDAY. A
BROAD AND DRY AREA OF HIGH PRESSURE WILL THEN BUILD IN FROM THE
NORTH WEDNESDAY AND LINGER THROUGH THE END OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 145 PM EDT SATURDAY...RAINFALL CONTINUES TO BECOME MORE
WIDESPREAD AND HEAVIER OVER WESTERN NC AND THE NRN UPSTATE OF SC.
THIS IS IN LINE WITH THE LATEST GFS AND ECMWF. UPPER DIVERGENCE
REMAINS STRONG THROUGH 00 UTC AND THE RAIN SHOULD FALL FOR SEVERAL
MORE HOURS. THE POPS GENERALLY REFLECT THIS...THOUGH I WILL INCREASE
THEM SOME WITH THE AFTERNOON PACKAGE. I HAVEN/T SEEN MUCH GROUND
TRUTH ON RAINFALL RATES YET...THOUGH I DO NOT THINK THEY WILL BE
HEAVY ENOUGH TO CAUSE FLOODING.

AS OF 1035 AM EDT SATURDAY...DEFORMATION ZONE PCPN CONTINUES ACROSS
MOST OF WESTERN NC AND THE NRN UPSTATE. IN FACT...RADAR RETURNS ARE
INCREASING AND COOLER CLOUD TOPS ARE WRAPPING INTO THIS REGION FROM
THE WEST. PER THE ECMWF AND NAM I SEE NO REASON WHY IT WON/T
RAIN/DRIZZLE ACROSS THESE AREAS THROUGH THE AFTERNOON HOURS AND I/VE
INCREASED POPS ACCORDINGLY. OVERALL...THE RAINFALL RATES SHOULD NOT
BE HEAVY ENOUGH TO CAUSE ANY SIGNIFICANT FLOODING CONCERNS...THOUGH
SOME OF THE USUAL PROBLEM AREAS OVER THE NC FOOTHILLS AND PIEDMONT
MAY EXPERIENCE SOME LOW END FLOODING DUE TO THE PROTRACTED NATURE OF
THE 0.10 INCH PER HOUR RAINFALL RATES AND SATURATED GROUND. WINDS
WILL CONTINUE TO GUST UP TO 25 KTS ALONG THE I-85 CORRIDOR THROUGH
THE REST OF THE DAY AS WELL.

AS OF 700 AM EDT...WATER VAPOR IMAGERY CONTINUES TO SHOW A TONGUE OF
MID AND UPPER LEVEL DRY AIR WRAPPING INTO THE SW HALF OF THE
FORECAST AREA THIS MORNING. PRECIPITATION HAS LARGELY TRANSITIONED
TO DRIZZLE IN THESE AREAS...AND POPS HAVE BEEN PARED BACK FROM THE
SW WITH AREAS OF DRIZZLE ADDED TO THE FORECAST. OTHERWISE...THE
INCREASINGLY STACKED SE LOW PRES SYSTEM WILL CONTINUE DRIFTING EWD
TOWARD THE COAST. STILL ANTICIPATE A BRIEF RESURGENCE IN FORCING 12Z
TO 18Z AS DEEP LAYER QG FORCING CROSSES THE REGION AND AN AXIS OF
FRONTOGENESIS PERSISTS ACROSS THE HEART OF THE FORECAST AREA THROUGH
EARLY AFTN BEFORE WEAKENING LATE TODAY INTO TONIGHT. THE GREATEST
QPF SHOULD IMPACT THE CHARLOTTE METRO AREA...BUT GIVEN THE WEAK
RAINFALL RATES OBSERVED THUS FAR...AS WELL AS THE FFG AND HEADWATER
GUIDANCE VALUES...IT APPEARS THAT ANY HYDRO PROBLEMS WILL BE QUITE
ISOLATED.

IN ADDITION...THE TIGHTENING PRES GRADIENT WILL CAUSE NE WINDS TO
PICK UP...WITH GUSTS WELL INTO THE 20S AND POSSIBLY ABOVE 30 MPH AT
TIMES THIS AFTN ACROSS THE PIEDMONT. SFC CAD REMAINING IN PLACE
THROUGH TONIGHT WILL KEEP THE DIURNAL TEMP RANGE FAIRLY SMALL.
PRECIPITATION SHOULD GRADUALLY END FROM THE WEST TONIGHT AS THE
MOISTURE AND FORCING DIMINISH.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 230 AM SATURDAY...THE STACKED LOW PRES SYSTEM WILL CONTINUE TO
SLOWLY DRIFT EAST AWAY FROM THE CAROLINA COASTS ON SUNDAY...WITH
WRAP-AROUND CLOUD COVER AND DECENT NELY LLVL FLOW LINGERING ATOP THE
CWFA. IT DOES LOOK LIKE POPS SHUD PRETTY MUCH BE OVER ACRS THE AREA
BY DAYBREAK SUNDAY...BUT A SLGT CHC DOES LINGER IN THE SE ZONES THRU
MIDDAY. WITH THE COOL NE FLOW AND LINGERING CLOUDS...I UNDERCUT MOS
TEMPS...ESP IN THE EAST.

SUNDAY NIGHT THRU MONDAY...SHORTWAVE RIDGING RIPPLES ACRS THE AREA
BEHIND THE DEPARTING LOW. TEMPS REBOUND TO NEAR NORMAL READINGS
UNDER MOSTLY CLEAR SKIES.

MONDAY NIGHT...THE NEXT SHORTWAVE TROF APPROACHES FROM THE WEST.
HEIGHT FALLS ALOFT AND LLVL MOISTURE ARRIVING WITHIN INCREASING WLY
FLOW MAY SUPPORT A FEW SHWRS ALONG THE NC/TN BORDER OVERNIGHT. BUT
OTHERWISE...JUST AN INCREASE IN CLOUDS AND TEMPS A COUPLE CATEGORIES
ABOVE NORMAL.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 245 AM SATURDAY...MODELS STILL IN GOOD AGREEMENT ON TIMING A
COLD FROPA ACRS THE CWFA ON TUESDAY. THE FRONT WILL BE RELATIVELY
WEAKLY FORCED. BUT THERE SHUD BE ENUF Q-VECTOR CONVERGENCE COUPLED
WITH LLVL FRONTAL CONVERGENCE AND MOISTURE TO SUPPORT AT LEAST
SCATTERED SHWRS WITH THE FRONT. THE TIMING LOOKS GOOD FOR ABOUT
MAXIMUM DAYTIME HEATING INSTBY...WITH THE GFS MOST BULLISH WITH UP
TO 1000 J/KG OF SBCAPE BY 18Z TUESDAY. HOWEVER...I THINK THE
DOWNSLOPE W/NW LLVL FLOW WILL LIMIT COVERAGE AND OVERALL INSTBY. THE
GFS HODOGRAPHS ALSO DON/T SHOW MUCH SHEAR FOR ORGANIZED
CONVECTION...WITH UNIDIRECTIONAL W/NW FLOW ONLY INCREASING TO ABOUT
30 KTS IN THE MID LVLS. TEMPS WILL BE ABOVE NORMAL...UPR 70S TO LWR
80S EAST OF THE MTNS...ASSUMING FRONT PUSHES THRU LATE AFTN/EVE.

TUESDAY NIGHT THRU END OF THE WEEK...UPR FLOW CONTINUES TO BE QUITE
PROGRESSIVE...WITH ANOTHER UPR RIDGE BUILDING IN FOR WEDNESDAY AND
THURSDAY...FOLLOWED BY ANOTHER LATITUDINAL TROF APPROACHING THE AREA
FRIDAY. TEMPS REMAIN NEAR OR SLIGHTLY ABOVE NORMAL...WITH THE SFC
HIGH PRES CENTER TRANSLATING EAST ACRS THE GREAT LAKES. A COLD FRONT
WILL PUSH INTO THE OHIO VALLEY FRIDAY...WITH SLGT CHC TO LOW-END CHC
POPS CREEPING BACK IN BY FRIDAY EVENING.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AT KCLT AND ELSEWHERE...RAINFALL INTENSITY AND COVERAGE IS
INCREASING OVER WESTERN NC...THOUGH THE HEAVIER RAIN IS LOCATED A
LITTLE WAYS TO THE NORTH AND WEST OF THE KCLT AIRFIELD. AS LONG AS
THE UPSTREAM AIRMASS CONTINUES TO BE SATURATED BY PCPN...IFR CIGS
SHOULD CONTINUE TO AFFECT THE AIRFIELDS...ESPECIALLY AT KCLT AND THE
UPSTATE SITES. IFR CIGS WERE KEPT AT KCLT THROUGH 21 UTC WITH MVFR
DEVELOPING THEREAFTER. HOWEVER...I SUSPECT THAT IFR COULD CONTINUE
LONGER THAN THIS AT KCLT. GUSTY NORTHEAST WINDS WILL CONTINUE
THROUGH THE NIGHT FROM KCLT DOWN TO KAND. WIND GUSTS OF 25 KTS
SHOULD BE COMMON. CIGS SHOULD BEGIN TO LIFT BY LATE EVENING ONCE THE
PCPN STARTS TO DIMINISH.

OUTLOOK...DRY HIGH PRES WILL THEN DEVELOP THROUGH MONDAY...WITH A
FAIRLY WET FRONTAL SYSTEM EXPECTED ON TUE.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       MED   73%     HIGH  81%     HIGH  93%     HIGH 100%
KGSP       LOW   59%     HIGH  80%     HIGH  93%     HIGH 100%
KAVL       MED   72%     HIGH  81%     HIGH 100%     HIGH 100%
KHKY       HIGH  83%     MED   78%     HIGH  94%     HIGH 100%
KGMU       LOW   51%     HIGH  80%     HIGH  91%     HIGH 100%
KAND       MED   71%     HIGH  85%     HIGH  92%     HIGH 100%

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...ARK
NEAR TERM...MCAVOY
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...MCAVOY






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