Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 171742
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
142 PM EDT THU APR 17 2014

.SYNOPSIS...
AN UNSEASONABLY COLD AIR MASS WILL REMAIN OVER THE REGION INTO
FRIDAY. A SUBTROPICAL LOW WITH DEEP MOISTURE WILL DEVELOP ACROSS THE
SOUTHEAST STATES ON FRIDAY AND SATURDAY. BY EARLY NEXT
WEEK...TEMPERATURES SHOULD RANGE CLOSE TO NORMAL AHEAD OF AN
APPROACHING COLD FRONT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 140 PM EDT THURSDAY...THE AFTERNOON GRIDS ARE IN GOOD SHAPE
AND NO CHANGES HAVE BEEN MADE INTO THE EARLY EVENING HOURS.

AS OF 1025 AM EDT THURSDAY...STILL EXPERIENCING SOME CI OVER THE
FORECAST AREA AS A WEAK UPPER WAVE IS PASSING BUY. SKY COVER WAS
INCREASED A LITTLE TO ACCOUNT FOR THIS...THOUGH THE REST OF THE
FORECAST IS IN FINE SHAPE.

AS OF 645 AM...CIRRUS HAS OVERSPREAD THE AREA AND WILL REMAIN THRU
THE DAY. GUIDANCE IS NOW IN GOOD AGREEMENT SHOWING LOW CLOUDS MOVING
INTO THE AREA FROM THE SOUTH THIS EVENING AND OVERNIGHT. SAT PIX
SHOW THESE CLOUDS ALONG THE GA/SC COAST WITH A NORTHWARD TRAJECTORY.
OTHERWISE...GOING FCST LOOKS ON TRACK...SO UPDATES MAINLY FOR
CURRENT CONDITIONS.

AS OF 245 AM...HIGH PRESSURE REMAINS RIDGED INTO THE AREA FROM THE
NE TODAY. RISING THICKNESSES...SUN FILTERING THRU MOSTLY THIN CIRRUS
AND A MODERATING AIR MASS WILL LEAD TO WARMER HIGHS TODAY.
HOWEVER...THEY WILL STILL BE AROUND 10 DEGREES BELOW NORMAL. NELY
WINDS OUTSIDE OF THE MTNS WILL BECOME GUSTY WITH MIXING ACROSS THE
UPSTATE AND NE GA...AND POSSIBLY PARTS OF NC...BY MID MORNING AS
MIXING BEGINS. GUSTS SHUD TAPER OF FOR THE AFTERNOON. WINDS ACROSS
THE MTNS WILL BE SLY AND COULD SEE GUSTS FOR THE AFTERNOON.

ALTHOUGH SFC WINDS WILL REMAIN NELY OUTSIDE OF THE MTNS TONIGHT WITH
HIGH PRESSURE REMAINING IN PLACE...LOW LEVEL FLOW BECOMES SLY AHEAD
OF AN APPROACHING SHORT WAVE IN THE SWLY UPPER FLOW AND A DEVELOPING
GULF OF MEXICO SFC LOW. GUIDANCE NOW INDICATES LOW LEVEL MOISTURE
WILL MOVE INTO THE AREA FROM THE SOUTH AS THE SHORT WAVE APPROACHES
THE AREA. LOWS SHUD BE QUITE A BIT WARMER THAN PREVIOUS NITES WITH
INCREASING CLOUDS AND MODERATING AIR MASS. LOWS STILL END UP AROUND
5 DEGREES BELOW NORMAL...AND COULD LEAD TO PATCHY FROST ACROSS THE
NC MTNS.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
AS OF 240 AM THURSDAY...THE GFS AND ECMWF INDICATE THAT AN AMPLIFIED
H5 TROUGH WILL RIPPLE OVER THE DEEP SOUTH ON FRIDAY. BOTH SOLUTIONS
SHOW THE TROUGH CLOSING OFF OVER S. GA AND N. FL...WITH THE GFS
NORTH OF THE ECMWF. AT THE SFC...LOW PRESSURE WILL LIKELY ORGANIZE
ALONG THE GA/FL LINE...WITH NEW ENGLAND CENTERED HIGH PRESSURE
RIDGING ACROSS THE WESTERN CAROLINAS. THERE IS STRONG AGREEMENT
WITH PLACEMENT OF DEEP MOISTURE AND LIFT ALONG AND EAST OF THE SFC
AND MID LEVEL LOW. HOWEVER...MODEL AGREEMENT IS LOW ACROSS THE
WESTERN CAROLINAS...WITH THE GFS AND ECMWF TRENDING WETTER ACROSS
THE CWA AND NAM REMAINING DRY. BASED ON MODEL TRENDS...I WILL
HIGHLIGHT THE MTNS...UPPER SAVANNAH RIVER VALLEY...AND EASTERN
PIEDMONT WITH CHC POPS FOR SHRA. IN ADDITION...SKY COVER WILL
LIKELY FAVOR MOSTLY CLOUDY CONDITIONS. A BLEND OF PREFERRED MOS
GUIDANCE SUPPORTS HIGHS ON FRIDAY IN THE UPPER 50S.

FRIDAY NIGHT AND SATURDAY...A BAND OF CLOUD COVER AND DEFORMATION
FORCING MAY LINGER ACROSS THE WESTERN CAROLINAS. THIS BAND WILL
LIKELY SLOWLY DRIFT EASTWARD THROUGH SATURDAY. THE FORECAST WILL
INDICATE MOSTLY CLOUDY CONDITIONS WITH SCHC POPS FRIDAY
NIGHT...DECREASING FROM WEST TO EAST DURING THE DAYLIGHT HOURS ON
SATURDAY. SATURDAY HIGHS ARE VERY CHALLENGING...WITH THE PRESENCE OF
CLOUDS AND SHRA WILL LIKELY IMPACT TEMPS BY 10 TO 15 DEGREES. AT
THIS TIME...I WILL FORECAST HIGHS AROUND 5 DEGREES BELOW NORMAL.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 3 AM THURSDAY...SUNDAY AND MONDAY...MEDIUM RANGE MODELS INDICATE
THAT THE MID LEVEL CLOSED LOW WILL DRIFT EAST OVER THE WESTERN
ATLANTIC AS MID LEVEL RIDGING INCREASES EAST OF THE MISSISSIPPI
RIVER VALLEY. THIS PATTERN SHOULD RESULT IN WEAK SFC HIGH PRESSURE
AND DRY AIR TO BUILD WEST TO EAST ACROSS THE FORECAST AREA SUNDAY
AND MONDAY. HIGH TEMPERATURES WILL LIKELY RANGE WITHIN 2 TO 4 DEGREES OF
NORMAL.

ON TUESDAY...THE GFS AND ECMWF INDICATE THAT A MID LEVEL SHORT WAVE
WILL RIPPLE OVER THE FORECAST AREA DURING THE DAYLIGHT HOURS. AT THE
SFC...A WEAK COLD FRONT IS TIMED TO SWEEP ACROSS THE SOUTHERN
APPALACHIAN REGION DURING THE AFTERNOON. BOTH SOLUTIONS INDICATES
THAT A FIELD OF WEAK CAPE WILL EXIST ALONG AND AHEAD OF THE COLD
FRONT. THE APPROACH OF THE MID LEVEL S/W AND COLD FRONT...COMBINED
WITH WEAK INSTABILITY SHOULD YIELD AT LEAST SCT SHRA/TSRA. DRY
CANADIAN HIGH PRESSURE SHOULD BUILD ACROSS THE REGION ON WEDNESDAY.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AT KCLT AND ELSEWHERE...LATEST MODEL RUNS AND GUIDANCE ARE NOT AS
AGGRESSIVE IN BRINGING IN STRATO-CU OVERNIGHT. HOWEVER...THERE IS A
GOOD CU FIELD NOT TOO FAR SOUTHWEST OF THE FORECAST AREA. I HAVE
DECIDED TO KEEP THE LOW END VFR CIGS...THOUGH I DID PUSH THEM BACK A
FEW HOURS AT ALL SITES. KCLT HAS ABOUT THE BEST CHANCE OF SEEING A
DECK UP AROUND 4KFT DEVELOPING LATE TONIGHT...AT LEAST PER THE
GUIDANCE. WINDS WILL BE ENE THIS AFTN...TURNING BACK TO NE OR EVEN
NNE LATE TONIGHT AS ANOTHER SURGE OF COOLER AIR MOVES IN FROM THE
NORTH. AS THIS HAPPENS...WIND SPEEDS SHOULD PICK BACK UP TO 8 TO 10
KTS BY AROUND SUNRISE.

OUTLOOK...CEILING AND VISIBILITY RESTRICTIONS WILL RETURN FRIDAY
EVENING THROUGH SATURDAY AS A COLD FRONT APPROACHES FROM THE WEST
AND A LOW PRESSURE SYSTEM DEVELOPS ALONG THE COAST. FAIR AND DRIER
WEATHER WITH NO RESTRICTIONS SHOULD RETURN FOR SUNDAY AND MONDAY.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-17Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  92%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  92%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  85%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  89%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  96%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     MED   78%

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...NED
NEAR TERM...MCAVOY/RWH
SHORT TERM...NED
LONG TERM...NED
AVIATION...MCAVOY






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