542  
FXUS62 KGSP 221946  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
246 PM EST SAT NOV 22 2014  
   
SYNOPSIS
 
 
DRY HIGH PRESSURE WILL GIVE WAY TO A VERY MOIST SOUTHERLY FLOW ON  
SUNDAY. A COLD FRONT WILL MOVE OVER THE REGION ON MONDAY WITH DRIER  
AND COLDER AIR BEHIND IT. A COASTAL LOW IS THEN EXPECTED TO DEVELOP  
OFF THE SOUTHEAST COAST AND MOVE UP THE ATLANTIC SEABOARD ON  
WEDNESDAY AND THURSDAY. HIGH PRESSURE WILL SPREAD BACK OVER THE AREA  
IN THE LOWS WAKE.  
 

 
   
NEAR TERM /THROUGH SUNDAY/
 
 
AS OF 200 PM EST SATURDAY...1033 MB HIGH PRESSURE CURRENTLY CENTERED  
OVER THE EASTERN CAROLINAS WILL CONTINUE TO SLIDE OFFSHORE THROUGH  
TONIGHT AS A DEVELOPING SURFACE LOW OVER THE WESTERN GULF TRACKS  
NORTHEASTWARD. AS A SOUTHERN STREAM UPPER SHORTWAVE TROUGH  
APPROACHES FROM THE SOUTHWEST...UPPER PATTERN BECOMES SOUTHWESTERLY  
OVER THE REGION WITH MID-HIGH LVL CLOUDINESS OVERSPREADING THE  
REGION IN ITS WAKE. LATEST SHORT RANGE MODELS CONTINUE TO AGREE THAT  
THE LOW WILL TRACK NNE ACROSS THE MID MISSISSIPPI VALLEY AND  
INTO THE GREAT LAKES REGION TONIGHT INTO SUNDAY...LIFTING AN  
ASSOCIATED WARM FRONT NE ACROSS THE SOUTHERN PLAINS TONIGHT AND INTO  
SOUTHERN GA/SC BY SUNDAY. ISENTROPIC UPGLIDE WILL STRENGTHEN OVER  
THE REGION AHEAD OF THIS FEATURE TONIGHT AS S/SSELY LLVL JET  
INCREASES ATOP THE IN-SITU CAD. AS A RESULT...PRECIP SHOULD  
OVERSPREAD THE AREA FROM THE SOUTHWEST BY SUN MORNING. HEAVIER  
PRECIP SHOULD OCCUR DURING THE DAY ON SUNDAY AS THE COMBINATION OF  
DIFFLUENT UPPER FLOW AND IMPRESSIVE ISENTROPIC UPGLIDE PROMOTE  
STRONGER LIFT AS WELL AS MAXIMIZING DEEP ATLANTIC MOISTURE FLUX OVER  
THE REGION. HENCE...POPS RAMP UP FROM SW TO NE SUN MORNING AND  
PEAKING CATEGORICAL RANGE THROUGH SUN AFTERNOON.  
 
HYDRO...TOTAL RAINFALL SHOULD RANGE FROM 1.5-2 INCHES OVER THE  
BLUE RIDGE ESCARPMENT TO 1 TO 1.5" ELSEWHERE. GIVEN PROLONGED DRY  
CONDITIONS AND +3.5" OF 6HR FLASH FLOOD GUIDANCE OVER MUCH OF THE  
AREA...THE THREAT FOR FLASH FLOODING APPEARS MINIMAL...THOUGH  
ISOLATED FLOODING CAN NOT BE RULED OUT IN LOW LYING/POOR DRAINAGE  
URBAN AREAS.  
 
SEVERE WEATHER POTENTIAL...ALTHOUGH WILL BE VERY STRONG WIND SHEAR  
ALOFT AND LONG CURVY HODOGRAPH...THE THREAT FOR SEVERE WEATHER  
APPEARS UNLIKELY THANKS TO PERSISTENT IN-SITU CAD AND THE LACK OF  
DEEP UPPER FORCING. HOWER...HAVE CARRIED THUNDER MAINLY EAST OF THE  
MTNS ZONES AS MODELS DEPICT WEAK ELEVATED BUOYANCY REGIME EXTENDS  
NORTHWARD TOWARD LATE SUN AFTERNOON.  
 

 
   
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/
 
 
AS OF 230 PM SATURDAY...THE TIMING OF THE PASSAGE OF A STRONG SHORT  
WAVE HAS SLIPPED JUST A BIT INTO SUNDAY EVENING...WHICH DELAYS THE  
DEPARTURE OF THE MAIN PRECIP AREA...SO A CATEGORICAL POP WAS KEPT  
INTO THE EVENING HOURS OVER THE ERN HALF OF THE FCST AREA...WITH  
LIKELY W OF THERE. OUR MAIN CONCERN CONTINUES TO BE THE THREAT FOR  
SEVERE STORMS...PRIMARILY OVER THE AREA S/E OF I-85. THE OPERATIONAL  
MODELS SUGGEST THAT OUR IN-SITU WEDGE WILL BREAK DOWN/ERODE FROM THE  
SE LATE IN THE DAY ALLOWING FOR SOME WEAK BOUYANCY TO CREEP INTO THE  
SE FRINGE OF THE FCST AREA. THUS...THE MODEL TREND LOOKS TO BE  
POINTED TOWARD A BIT MORE INSTABILITY...TO GO ALONG WITH THE VERY  
STRONG SHEAR. HOWEVER...THE EXPECTED DEGREE OF ORGANIZATION STILL  
APPEARS TO BE LACKING. IN TYPICAL EVENTS WHERE WE SEE SEVERE WEATHER  
FROM LINEAR CONVECTION IN HIGH SHEAR LOW CAPE ENVIRONMENTS...WE TEND  
TO HAVE A VERY STRONG ADVECTIVE SHORT WAVE THAT TRACKS RIGHT ACROSS  
THE FCST AREA. THIS WAVE TRACKS PAST THE MTNS TO THE NW SUNDAY EVE.  
FURTHERMORE...AN EXPERIMENTAL INDEX FOR HIGH SHEAR LOW CAPE SEVERE  
WEATHER (CALLED THE SHERB INDEX)...HAS VALUES BELOW WHAT IS EXPECTED  
FOR AN ENVIRONMENT THAT SUPPORTS SEVERE WEATHER...WHEN RUN FOR THE  
OPERATIONAL NAM AND GFS. WILL INCLUDE A CHANCE FOR THUNDERSTORMS  
OVER THE SE ZONES IN THE EVENING. BOTTOM LINE...WE CANNOT TOTALLY  
RULE OUT SEVERE WEATHER OVER THE SE ZONES...BUT UNLESS WE SEE MORE  
INSTABILITY OR A BETTER INDICATION OF STORM ORGANIZATION...WE WILL  
NOT MENTION THE NON-ZERO SEVERE WEATHER CHANCES IN THE HWO. AS FOR  
HEAVY RAIN...CANNOT RULE OUT SOME HEAVY RAIN NEAR THE BLUE RIDGE IN  
THE EVENING AS A STRONG LOW LEVEL JET REMAINS DIRECTED AT THE  
MTNS...BUT THE 850MB FLOW VEERS QUICKLY SW IN THE EVE AS THE WAVE  
PASSES. ANTECEDENT CONDITIONS ARE DRY...WHICH LOWERS OUR FLOOD RISK.  
TEMPS ARE INTERESTING SUNDAY EVE/NIGHT WITH THE DESTRUCTION OF THE  
WEAK WEDGE AND CONTINUED WARM ADVECTION. EXPECT THAT MOST PLACES  
WILL HAVE THEIR HIGH FOR SUNDAY AFTER SUNSET AS TEMPS CONTINUE TO  
RISE. TEMPS SHOULD REMAIN MILD OVERNIGHT AS THE MAIN FRONT REMAINS  
TO THE WEST. ON MONDAY...THERE ARE SOME MODEL DISCREPANCIES AS TO  
THE AMOUNT OF SHOWER ACTIVITY...WITH THE GFS/ECMWF SHOWING LESS  
PRECIP THAN THE NAM. WILL KEEP A LOW CHANCE FIRST THING AND  
GRADUALLY TAPER IT DOWN FROM THERE...MAINLY BECAUSE THE FRONT SHOULD  
PASS THROUGH DURING THE DAY. FEEL THE NAM IS WAY OVERDONE BECAUSE IT  
KEEPS SFC DEWPOINT VALUES IN THE LOWER TO MIDDLE 60S E OF THE MTNS  
WHICH RESULTS IN TOO MUCH INSTABILITY WHICH TRIGGERS THE CONVECTIVE  
PRECIP SCHEME. THE GFS LOOKS MORE REASONABLE WITH MID/UPPER 50S  
DEWPOINTS...SO QUITE A BIT LESS CONVECTIVE PRECIP.  
 
THE REST OF THE SHORT RANGE IS QUIET. WE STAY IN A SW FLOW ALOFT  
WITH NO MID/UPPER FORCING AND HIGH PRESSURE BUILDING IN FROM THE  
WEST. SOME LINGERING LIGHT PRECIP OVER THE TN BORDER ZONES SHOULD  
END MONDAY EVENING AND AFTER THAT THE FCST WAS KEPT DRY. ANY  
DEVELOPMENT CLOSER TO THE OLD STALLED FRONT OFF THE E COAST SHOULD  
STAY TO OUR EAST. TEMPS TUESDAY WILL BE 10-15 DEGREES COOLER THAN  
MONDAY.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/
 
 
AS OF 2 PM SATURDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON  
WEDNESDAY WITH BROAD AND DEEP UPPER TROFFING CENTERED JUST TO OUR  
WEST. OVER THE NEXT 24 TO 36 HRS...THE TROF AXIS IS EXPECTED TO LIFT  
NE OF THE FCST AREA WITH SOME DEGREE OF DEAMPLIFICATION IN ITS WAKE.  
THE LONG RANGE MODELS DIFFER WRT EXACTLY HOW LONG THE DEEPER TROFFING  
LASTS OVER THE CWFA WITH THE ECMWF MAINTAINING A CONSIDERABLY  
STEEPER TROF THRU THE FIRST HALF OR SO OF FRI WHILE THE GFS AND  
CANADIAN INCREASE HEIGHTS FASTER AND FLATTEN THE UPPER PATTERN  
SOONER. EITHER WAY...ALL OF THE GUIDANCE SUGGESTS THAT FROM LATE FRI  
ONWARD...THE REGION WILL REMAIN UNDER A RELATIVELY ZONAL PATTERN  
WITH UPPER HEIGHTS RELATIVELY CONSTANT.  
 
AT THE SFC...THE LATEST 12Z RUN OF THE GFS IS TRENDING MORE TOWARDS  
AN ECMWF-LIKE SCENARIO WRT THE DEVELOPMENT OF A SOUTHERN COASTAL LOW  
ON WED. BY 18Z WED...BOTH MODELS NOW HAVE A WELL DEFINED LOW CENTERED  
JUST OFF THE CAROLINA COAST WITH DEEP LYR MOISTURE SPREADING OVER  
THE MAJORITY OF THE CWFA. THE ECMWF STILL MAINTAINS A LARGER...DEEP  
MOISTURE PLUME OVER OUR AREA COMPARED TO THE GFS...BUT NOT BY MUCH.  
BOTH MODELS AGREE THAT BY EARLY THURS...THINGS SHOULD DRY OUT PRETTY  
QUICKLY AS THE LOW TRACKS UP THE EAST COAST. A WEAK SECONDARY COLD  
FRONT IS EXPECTED TO PASS JUST TO OUR NORTH AS THE MAIN LOW LIFTS NE  
AND SOME LINGERING PRECIP IS POSSIBLE OVER THE NORTHERN AND WESTERN  
ZONES...HOWEVER IT SHOULD NOT AMOUNT TO MUCH. THE REST OF THE MEDIUM  
RANGE SHOULD BE DRY WITH HIGH PRESSURE REGAINING CONTROL OVER THE  
REGION. AS HIGHLIGHTED IN THE PREVIOUS DISCUSSION...MINOR AMOUNTS OF  
FROZEN PRECIP ARE POSSIBLE WITH THE COASTAL LOW ON WED. MODEL  
SOUNDINGS STILL SUPPORT SNOW AND/OR SNOW/SLEET OVER THE HIGHER  
ELEVATIONS EARLY WED...HOWEVER BEYOND THE LATE MORNING IT LOOKS LIKE  
TEMPS WILL BE TOO WARM TO SUPPORT ANYTHING BUT RAIN. IN  
ADDITION...AT PRESENT THE BULK OF THE QPF IS EXPECTED OVER THE  
EASTERN HALF OF THE CWFA AND NOT THE HIGHER TERRAIN. YET...THE NC  
MTS COULD SEE SOME ADDITIONAL LINGERING NW FLOW SNOW WED NIGHT INTO  
THURS...BUT IT LIKELY WONT BE MUCH. OTHERWISE...TEMPS START OUT  
BELOW CLIMO AND REMAIN THERE THRU DAY 7.  
 

 
   
AVIATION /20Z SATURDAY THROUGH THURSDAY/
 
 
AT KCLT...EXPECT VFR CONDITIONS TO CONTINUE AT LEAST THROUGH EARLY  
SUNDAY MORNING AS CP HIGH PRESSURE CENTERED OVER THE EASTERN  
CAROLINAS CONTINUES TO SHIFT EAST. AS MOIST SWLY FLOW ALOFT DEVELOPS  
IN RESPONSE TO AN APPROACHING UPPER SHORTWAVE TROUGH FROM THE  
SW...EXPECT INCREASING MID-HIGH LVL CLOUDINESS THIS EVENING INTO  
TONIGHT. LIGHT SE WINDS THIS AFTERNOON WILL BECOME NORTHEASTERLY BY  
AROUND 03Z SUN AND STAY THAT WAY THRU THE END OF THE TAF PERIOD AS  
COLD AIR DAMMING SETS UP OVER THE AREA. AS A SOUTHERN STREAM UPPER  
WAVE APPROACHES THE REGION TONIGHT...ISENTROPIC UPGLIDE WILL  
STRENGTHEN AND CIGS WILL BE LOWERED TO MVFR LVL BY AROUND 14Z SUN  
WITH PRECIP OVERSPREADING THE REGION FROM THE SW. LATEST GUIDANCE  
SUGGESTS THAT IFR CIGS IN MODERATE RAIN WILL AFFECT THE TERMINAL BY  
16Z SUN AS DEEP MOISTURE/BETTER UPPER FORCING MOVE THROUGH.  
 
ELSEWHERE...EXPECT VFR CONDITIONS TO PERSIST AT LEAST THROUGH LATE  
TONIGHT/EARLY SUNDAY MORNING AS CP HIGH PRESSURE CENTERED OVER THE  
EASTERN CAROLINAS CONTINUES TO SLIDE EAST. AS MOIST SWLY FLOW ALOFT  
DEVELOPS IN RESPONSE TO AN APPROACHING UPPER SHORTWAVE TROUGH FROM  
THE SW...EXPECT INCREASING MID-HIGH LVL CLOUDINESS THROUGH TONIGHT.  
LIGHT ESE/SE WINDS THIS AFTERNOON WILL BECOME NORTHEASTERLY BY THIS  
EVENING AND STAY THAT WAY THRU THE END OF THE TAF PERIOD AS COLD AIR  
DAMMING SETS UP OVER THE AREA. THE EXCEPTION WILL BE KAVL WHERE  
SOUTHERLY WINDS WILL PERSIST THROUGH THE PERIOD. AS A SOUTHERN  
STREAM UPPER WAVE ASSOCIATED WITH A WARM FRONT APPROACHES THE  
REGION...ISENTROPIC UPGLIDE WILL STRENGTHEN AND MVFR CLOUDS WITH  
PRECIP WILL OVERSPREAD THE REGION FROM THE SW LATE TONIGHT INTO  
EARLY SUN MORNING. LATEST GUIDANCE SUGGESTS THAT IFR CIGS...MODERATE  
RAIN AND MVFR VSBY WILL AFFECT MUCH OF THE REGION BY LATE SUN  
MORNING AS DEEP MOISTURE/BETTER UPPER FORCING MOVE THROUGH.  
 
OUTLOOK...RESTRICTIVE CIGS AND PRECIPITATION WILL BE WIDESPREAD  
SUNDAY AS A WARM FRONT LIFTS THRU THE REGION FROM THE SOUTH. BRIEF  
DRYING FOLLOWS THE FRONT MON-TUE...WITH PRECIP POSSIBLY RETURNING  
WED.  
 
CONFIDENCE TABLE...  
 
19-01Z 01-07Z 07-13Z 13-18Z  
KCLT HIGH 100% HIGH 100% HIGH 94% MED 78%  
KGSP HIGH 100% HIGH 100% HIGH 88% HIGH 94%  
KAVL HIGH 100% HIGH 100% HIGH 96% HIGH 82%  
KHKY HIGH 100% HIGH 100% HIGH 93% HIGH 83%  
KGMU HIGH 100% HIGH 100% HIGH 86% HIGH 94%  
KAND HIGH 100% HIGH 100% HIGH 88% HIGH 90%  
 
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...JPT  
NEAR TERM...JOH  
SHORT TERM...PM  
LONG TERM...JPT  
AVIATION...JOH  
 
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