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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
952 PM EDT MON MAY 4 2015

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN ACROSS THE REGION THROUGH THE MIDDLE OF 
THE WORK WEEK. A WEAK COLD FRONT IS EXPECTED TO DRIFT DOWN FROM THE 
NORTH ON THURSDAY. THE REMAINDER OF THE WEEK AND WEEKEND IS STILL 
FAIRLY UNCERTAIN AS LOW PRESSURE MAY MOVE UP THE SOUTHEAST COAST AND 
OVER THE CAROLINAS OR REMAIN JUST OFFSHORE.

&&

.NEAR TERM /THROUGH TUESDAY NIGHT/...
0200 UTC UPDATE...POPS WERE LOWERED BASED ON RADAR TRENDS...AND
SKY COVER WAS LOWERED BASED ON SATELLITE TRENDS. WINDS WERE
UPDATED TO INCORPORATE THE LATEST ADJMAV GUIDANCE. ONLY VERY MINOR
CHANGES WERE MADE TO MINIMUM TEMPERATURES.

AS OF 245 PM...LATEST VISIBLE SATELLITE IMAGES INDICATED CU 
CONGESTUS ACROSS THE MTNS WITH FAIR WEATHER CU ACROSS THE FOOTHILLS 
AND PIEDMONT. MESOSCALE ANALYSIS CONTINUED TO SHOW AN AREA OF SBCIN 
ACROSS THE WESTERN NC MTNS AND ADJACENT FOOTHILLS. 
OTHERWISE...SBCAPE WAS LIMITED TO AROUND 250 J/KG. LATEST VCP32 SCAN 
FROM KGSP INDICATED A FEW SMALL SHOWERS ACROSS THE NRN MTNS AND 
ACROSS THE SOUTHERN MTNS. IT APPEARS THAT CONVECTIVE POTENTIAL WILL 
EXCEED ACTIVITY OBSERVED THIS WEEKEND...BUT NOT REACH THE LEVEL 
INDICATED IN THE LATEST CAMS. ANY STORMS THAT DO DEVELOP WILL BE 
VERY SLOW MOVING...POSSIBLY AS SLOW AS 10 KTS. BASED ON THE 
INSTABILITY PROFILES AND SLOW STORM MOTIONS I WILL INDICATE POPS 
HIGHLY DEPENDENT ON ELEVATION...WITH SCHC ACROSS THE VALLEY AND 
LIKELY ABOVE 6 KFT. CONVECTION SHOULD DISSIPATE EARLY THIS 
EVENING...FOLLOWED BY GRADUAL CLEARING. THIN SKY COVER...LIGHT TO 
CALM WINDS...AND POCKETS OF WET GROUND COULD RESULT IN FOG DURING 
THE PRE DAWN HOURS.

ON TUESDAY...VERY LITTLE CHANGE FROM TODAY. ONCE AGAIN...HIGH 
TEMPERATURES ARE FORECAST TO RANGE FROM THE MID TO UPPER 70S WITHIN 
THE MTN VALLEYS TO THE LOW 80S TO THE EAST. FORECAST SOUNDINGS 
INDICATE A GREATER TEMPERATURE INVERSION AROUND 15 KFT...REMAINING 
UNDER MID LEVEL RIDGE. I WILL KEEP POPS A LITTLE LOWER THAN 
INDICATED FOR MON AFTERNOON AND EVENING. I WILL FAVOR THE EAST 
FACING SLOPES WITH CHC POPS...SCHC ACROSS THE VALLEYS...WITH LITTLE 
TO NO COVERAGE EXPECTED EAST.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 315 PM MONDAY...THE SHORT TERM CONTINUES TO BE FAIRLY 
UNEVENTFUL...DOMINATED BY HIGH PRESSURE OFF THE ATLANTIC RIDGING 
WESTWARD TOWARD THE SOUTHEAST AND MID-ATLANTIC STATE...AND WEAK 
RIDGING ALOFT. EXPECT A TYPICAL DIURNAL PATTERN IN SHOWER AND 
THUNDERSTORMS ACTIVITY...MAINLY CONCENTRATED OVER THE MOUNTAINS 
WHERE SOME SBCAPE MAY BE REALIZED...SO CONTINUED TREND OF SLIGHT TO 
LOW CHANCE POPS IN THOSE AREAS. THE OTHER FORECAST ISSUE...NOT 
REALLY MUCH OF AN ISSUE FOR THE SHORT TERM BUT REALLY FOR THE 
EXTENDED...IS PROGRESSION OF A NON-TROPICAL LOW PRESSURE DEVELOPING 
OVER THE BAHAMAS. THROUGH THE END OF THE SHORT TERM...STILL NOT 
REALLY EXPECTING ANY IMPACTS FROM THIS LOW...BUT FORECAST 
DIFFERENCES IN THE SYNOPTIC MODELS MAY MEAN SOME LARGE RESULTING 
DIFFERENCES IN SENSIBLE WEATHER. ALL GUIDANCE IS TRENDING TOWARD 
TURNING THIS LOW A LITTLE MORE TO THE RIGHT...BUT GFS/NAM/SREF STILL 
HAVE THE CENTER OF THE LOW APPROACHING THE SOUTH CAROLINA COAST AT 
THE END OF THE SHORT TERM...WITH SOME PRECIPITATION SPREADING TOWARD 
OUR SOUTHERN ZONES. ECMWF ON THE OTHER HAND KEEPS THE SURFACE LOW 
WELL OFFSHORE WITH NO REAL IMPACTS TO OUR FORECAST AREA AT ALL. FOR 
NOW...HAVE TRENDED A LITTLE HIGHER WITH SKY COVER ACROSS EASTERN 
ZONES WHICH MAY KEEP HIGH TEMPERATURES A LITTLE LOWER THURSDAY 
AFTERNOON...BUT KEPT POPS WITH MORE OF A DIURNAL TREND WITH HIGHEST 
CHANCES OVER THE MOUNTAINS.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 320 PM MONDAY...AS WE WORK INTO THE EXTENDED/MEDIUM RANGE... 
ALL EYES WILL BE ON THE NON-TROPICAL LOW IN THE ATLANTIC. NHC DOES 
HAVE A 30 PERCENT CHANCE OF THIS LOW DEVELOPING SUBTROPICAL 
CHARACTERISTICS OVER THE NEXT 5 DAYS SO WE WILL CONTINUE TO MONITOR. 
AS FOR THE FORECAST HOWEVER...DEFINITELY SOME CONCERNS WITH 
DIFFERENCES IN THE MAJOR SYNOPTIC MODELS WITH ECMWF KEEPING THE LOW 
OFFSHORE AND THE GFS BRINGING THE LOW INLAND OVER SOUTH CAROLINA AND 
SPREADING PRECIPITATION INTO OUR AREA LATE IN THE WEEKEND. WITH 
THIS...THE GFS IS BRINGING A BULLSEYE OF OVER 4 INCHES QPF TO 
CENTRAL SOUTH CAROLINA...WITH WIDESPREAD 1-2 INCHES ACROSS OUR 
EXTREME SOUTHEAST ZONES. THIS IS LIKELY OVERDONE WITH CONVECTIVE 
FEEDBACK BUT DOES GO TO SHOW THE RANGE OF POSSIBILITIES...BETWEEN 
NOTHING ON THE ECMWF TO THE HEFTY QPF VALUES ON THE GFS. WPC AND NHC 
GUIDANCE SUGGESTS...AT LEAST FOR NOW...FAVORING THE WESTWARD 
PROGRESSION OF THE LOW BUT CONFIDENCE IS NOT PARTICULARLY HIGH AT 
THIS POINT. SO FOR NOW...HAVE BEGUN BRINGING IN MID-RANGE CHANCE 
POPS ACROSS EASTERN ZONES OVER THE WEEKEND.

BEYOND ALL THIS...A STRONG TROUGH PUSHING THROUGH THE PLAINS OVER 
THE WEEKEND WILL ALLOW A COLD FRONT TO APPROACH THE APPALACHIANS 
EARLY NEXT WEEK. GFS IS FASTER WITH THIS...ABSORBING WHAT IS 
LEFTOVER OF THE FORMER COASTAL LOW BY THE END OF THE PERIOD... 
WHEREAS THE ECMWF HOLDS OFF ON PHASING THESE TWO SYSTEMS TILL AFTER 
THE END OF THE PERIOD. EITHER WAY...THE APPROACH OF THE COLD FRONT 
WILL PUSH ANY EFFECTS FROM THE COASTAL LOW OFFSHORE AS THE FRONT 
PUSHES EASTWARD. CONFIDENCE FOR THE END OF THE PERIOD IS 
PARTICULARLY LOW DUE TO THE TIMING DIFFERENCES IN THE FRONT AND 
UNCERTAINTY REGARDING THE POSITION/TIMING/PROGRESSION OF THE COASTAL 
LOW.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
AT KCLT...VFR. LOW VFR CIGS ARE NOT AS LIKELY AS OVER THE MOUNTAINS 
TO THE WEST. MODEL SOUNDINGS DO NOT LOOK MOIST ENOUGH FOR DAYBREAK 
FOG. DAYTIME PRECIPITATION SHOULD REMAIN TO THE WEST NEAR THE 
MOUNTAINS WHERE BETTER INSTABILITY WILL EXIST. LIGHT WINDS WILL 
FAVOR THE S. 

ELSEWHERE...VFR. A SMALL CHANCE OF SHOWERS WILL DWINDLE THIS 
EVENING OVER THE NC MOUNTAINS AS HEATING ABATES...BUT A LOW VFR 
CIGS REMAINS POSSIBLE AT KAVL THIS EVENING. MODEL GUIDANCE WAS NOT 
OVERLY SUPPORTIVE OF DAYBREAK FOG...BUT AS SOME DID OCCUR IN THE SW 
NC MOUNTAINS...AND THE LOWER ATMOSPHERE IS TRENDING MORE MOIST WITH 
TIME...GREATER FOG COVERAGE WILL BE ALLOWED BY DAWN...PRODUCING ONLY 
LOW IFR AT KAVL ONLY. LIGHT WINDS WILL FAVOR THE S.
  
OUTLOOK...ISOLATED TO SCATTERED DIURNAL MOUNTAIN CONVECTION IS 
EXPECTED THROUGH FRIDAY...AS MOIST SOUTHERLY FLOW PERSISTS.

CONFIDENCE TABLE...

            01-07Z        07-13Z        13-19Z        19-00Z 
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
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...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JPT
NEAR TERM...JAT/NED
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...JAT

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