Scientific Forecaster Discussion

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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
658 AM 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 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 /12Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...CIRRUS HAS OVERSPREAD THE AREA AND WILL 
CONTINUE THRU THE PERIOD. GUIDANCE NOW IN BETTER AGREEMENT ON LOW 
VFR CLOUDS MOVING IN FROM THE SOUTH DURING THE EVENING AND BECOMING 
BKN OVERNIGHT. MVFR CIGS CANNOT BE RULED OUT BEFORE DAYBREAK...BUT 
BULK OF THE GUIDANCE KEEPS THEM LOW VFR. NELY WIND THIS MORNING 
BECOMES GUSTY WITH MIXING BY MID-MORNING ACROSS THE UPSTATE...THEN 
WEAKENS DURING THE AFTERNOON AS IT TURNS ENE. KAVL THE EXCEPTION 
WHERE LIGHT NLY WIND EARLY THIS MORNING BECOMES SLY BEFORE NOON THEN 
BECOMES GUSTY FOR AFTERNOON. KAVL WIND RETURNS TO LIGHT NLY DURING 
THE EVENING. ELSEHWERE...WINDS TURN BACK TO NELY BUT REMAIN ABOVE 
THE LIGHT CATEGORY.

OUTLOOK...CEILING AND VISIBILITY RESTRICTIONS WILL RETURN FRIDAY AND 
SATURDAY AS A COLD FRONT APPROACHES FROM THE WEST AND A LOW PRESSURE 
SYSTEM DEVELOPS ALONG THE COAST.

CONFIDENCE TABLE...

            11-17Z        17-23Z        23-05Z        05-11Z 
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  97%     
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KAND       HIGH 100%     HIGH 100%     HIGH 100%     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...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR GAZ010-017.
     FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR GAZ018-026-028-
     029.
NC...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR NCZ035>037-048-
     051>053-056>059-062>065-068>072-082-501>510.
SC...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR SCZ003-006>009-
     011>014-019.
     FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR SCZ001-002-004-
     005-010.

&&

$$
SYNOPSIS...NED
NEAR TERM...RWH
SHORT TERM...NED
LONG TERM...NED
AVIATION...RWH