548  
FXUS62 KGSP 260018  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
718 PM EST TUE NOV 25 2014  
   
SYNOPSIS
 
 
LOW PRESSURE WILL DEVELOP ALONG A STALLED COLD FRONT OFF THE  
ATLANTIC SEABOARD TONIGHT AND MOVE UP THE COAST WEDNESDAY. AN UPPER  
LEVEL SYSTEM WILL CROSS WESTERN NORTH CAROLINA EARLY THURSDAY. DRY  
HIGH PRESSURE WILL RETURN FRIDAY AND LINGER INTO THE WEEKEND.  
 

 
   
NEAR TERM /THROUGH WEDNESDAY/
 
 
AS OF 715 PM...LATEST RADAR INDICATED A BAND OF LIGHT RAIN OR VIRGA  
ACROSS THE PIEDMONT...EAST OF CLT. THIS BAND IS PRIMARILY LOCATED  
NW OF A BAND OF FRONTOGENESIS. THE NAM INDICATES THAT H7  
FRONTOGENESIS WILL LIFT NORTHWARD THIS EVENING...REACHING THE I-85  
CORRIDOR BY 3Z. LARGE SCALE LIFT SLIDE ACROSS THE REGION AROUND  
SUNRISE...RESULTING IN THE GREATEST PRECIP RATES.  
 
I ADJUST POPS AND TEMPERATURES...BASED ON THE LATEST MOS AND MODEL  
RUNS. IT APPEARS THAT ACCUM SN WILL BE GREATER WITHIN THE MTN  
VALLEYS...WITH AREAS SEEING AROUND 2 INCHES. THIS UPDATE WILL  
INCREASE THE STORM TOTAL SNOWFALL...WITH PRIMARY FOCUS GIVEN TO THE  
VALLEY LOCATIONS.  
 
AS OF 225 PM EST...A FEW WINTER WEATHER WARNING/ADVISORY ADJUSTMENTS  
ARE BEING MADE. THE WINTER STORM WARNING IS BEING EXPANDED SLIGHTLY  
TO ENCOMPASS AVERY/MITCHELL/YANCEY. THE ADVISORY TIER HAS ALSO BEEN  
EXPANDED TO THE ERN SLOPES OF THE NRN BLUE RIDGE AND ALSO A BIT  
FARTHER INTO THE CENTRAL AND SRN NC MTNS.  
 
WATER VAPOR IMAGERY SHOWS A POSITIVELY TILTED 500 MB TROUGH EMERGING  
FROM THE PLAINS. THIS FEATURE WILL BECOME MORE NEUTRALLY TILTED OVER  
THE LOWER MS VALLEY TONIGHT AND THEN ACQUIRE A NEGATIVE TILT AS IT  
CROSSES THE APPALACHIANS WED AND PHASES BACK INTO THE BROADER TROUGH  
TO THE WEST OF THE APPALACHIANS. AT THE SFC...A LOW CENTER  
DEVELOPING ALONG THE FL E COAST LATE TODAY WILL MOVE RAPIDLY UP THE  
COASTLINE OF THE CAROLINAS TONIGHT. DEEP LAYER FORCING FROM  
FRONTOGENESIS WILL LIKELY SET UP INTO FAR INTERIOR PARTS OF THE  
CAROLINAS...POSSIBLY OVER THE FOOTHILLS. IN ADDITION...THE BEST  
UPPER DIVERGENCE IN THE RIGHT ENTRANCE REGION OF THE 250 MB JET  
STREAK WILL CROSS THE FORECAST AREA FROM THE WEST 09Z TO 15Z...WHILE  
DEEP LAYER Q VECTOR CONVERGENCE MAXIMIZES WITH THE TROUGH OVER WRN  
NC WED MORNING. THESE FEATURES SHOULD COME TOGETHER TO PRODUCE SOME  
SOLID 0.5 TO 0.75 INCH LIQUID EQUIVALENT PRECIP TOTALS TONIGHT  
THROUGH WED MORNING. MOST MODELS HAVE SLIGHTLY MORE QPF...BUT  
COASTAL CONVECTION COULD BE A LIMITING FACTOR IN CAPPING TOTALS.  
 
REGARDING PTYPES...MODEL PROFILES ALL HAVE SOME DEGREE OF A SFC WARM  
LAYER ACROSS THE PIEDMONT...FOOTHILLS...AND LOWER MTN VALLEYS.  
HOWEVER...THE MOST TROUBLING MODEL TREND IS FAIRLY STRONG 700 MB  
FRONTOGENESIS THAT APPEARS TO SET UP OVER THE FOOTHILLS. ALTHOUGH  
NON MTN PROFILES LOOK JUST WARM ENOUGH FOR RAIN THROUGHOUT...ANY  
HIGHER RATES COULD OVERCOME THE SFC BASED WARM LAYER AND PRODUCE  
SNOW SHOWERS AT TIMES OVER THE NC FOOTHILLS AND THE FAR NW  
PIEDMONT...AS WELL AS THE LOWER MTN VALLEYS. THE HIGHER TERRAIN  
SHOULD BE SOLIDLY SNOW FOR MOST OF THE EVENT. THE EVENTUAL TRACK OF  
THE DEEPENING 850 MB LOW CENTER WILL BE CRITICAL. SINCE THE MODELS  
HAVE TRENDED JUST WEST OF INTERSTATE 95...THE ASSOCIATED FORCING FOR  
RA/SN SHOWERS WILL BE PUSHED WEST INTO THE FOOTHILLS...WITH  
CORRESPONDING SLIGHTLY HIGHER QPF/SNOW TOTALS ALONG AND JUST E OF  
THE BLUE RIDGE. FOR THIS REASON...AN ERN ESCARPMENT EXPANSION OF THE  
WINTER WEATHER ADVISORY HAS BEEN ADDED. THE NRN MTN FORECAST TEETERS  
ON WARNING CRITERIA...BUT SINCE AVERY IS ALREADY IN SEE NO REASON TO  
NOT ADD YANCEY/MITCHELL FOR SOME 4 PLUS INCH ACCUMULATIONS OVER AT  
LEAST THE ERN HALF OF THESE COUNTIES. ADDITIONAL LOW END ADVISORY  
NUMBERS ARE EXPECTED A BIT FARTHER SW IN THE MTN...MAINLY AT HIGHER  
ELEVATIONS...BUT THE BRIEF DURATION OF THE EVENT AND THE MARGINALLY  
COLD TEMPS SHOULD PRECLUDE ANY WARNING AMOUNT/SIGNIFICANT TRAVEL  
PROBLEMS THERE.  
 
A LULL IN ACTIVITY IS EXPECTED BETWEEN UPPER WAVES WED AFTN ALONG  
WITH BRIEF DEEPER LAYER DRYING. HOWEVER...LOW LEVEL NW FLOW MOISTURE  
MAY CONTINUE TO WRING OUT SCATTERED NRN/WRN MTN SNOW SHOWERS WELL  
INTO THE AFTN. WILL TRIM MIN AND MAX TEMPS BELOW  
GUIDANCE...ESPECIALLY IN NRN SECTIONS...TONIGHT/WED.  
 

 
   
SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/
 
 
AT 230 PM EST TUESDAY...ON WEDNESDAY EVENING AN UPPER TROUGH AXIS  
WILL EXTEND FROM HUDSON BAY TO THE EASTERN GULF OF MEXICO. A STRING  
CHANNELED VORT LOBE ROUNDING THE BASE OF THE TROUGH WILL BE  
APPROACHING THE SOUTHERN APPALACHIANS. THE VORT LOBE CROSSES OUR  
AREA EARLY THURSDAY...WHILE THE DEAMPLIFYING TROUGH PROGRESSES TO  
THE EASTERN SEABOARD. BY FRIDAY THE UPPER TROUGH MOVES OFF THE EAST  
COAST...AND FLOW ALOFT BECOMES MORE ZONAL.  
 
AT THE SURFACE...A WEAKENING LOW WILL MOVE FROM THE LOWER OH RIVER  
VALLEY...ACROSS THE SOUTHERN APPALACHIANS ON WEDNESDAY NIGHT.  
MOISTURE AHEAD OF THIS SYSTEM WILL MOVE NE ACROSS OUR AREA...  
GENERALLY TO THE NW OF INTERSTATE 85. THICKNESS VALUES ARE RATHER  
LOW AT THIS TIME...SUPPORTING MAINLY WINTRY PRECIPITATION TO START  
WITH IN THE MOUNTAINS. PREVIOUS MODEL RUNS LACKED A WARM NOSE  
ALOFT...BUT MORE RECENT RUNS HAVE A BRIEF WARM NOSE AHEAD OF THIS  
LOW. THIS COULD RESULT IN SOME BRIEF FREEZING RAIN IN SOME PORTIONS  
OF THE SOUTHWEST NC MOUNTAINS WEDNESDAY EVENING...BUT OVERALL...  
PRECIPITATION SHOULD BE IN THE FORM OF SNOW IN THE NC  
MOUNTAINS...WITH RAIN TO THE EAST. MODEL SOUNDINGS DO LOWER THE  
FREEZING LEVEL LATE WEDNESDAY NIGHT AND EARLY THURSDAY ALONG  
INTERSTATE 40...TO THE POINT WHERE SNOW MAY MIX IN WITH RAIN...BUT  
SURFACE TEMPERATURES AROUND SIX DEGREES BELOW NORMAL ARE ONLY  
MARGINALLY SUPPORTIVE OF SNOWFALL ACCUMULATIONS. AT THIS  
POINT...MOUNTAIN SNOWFALL ACCUMULATIONS APPEAR TO FALL SHORT OF  
ADVISORY CRITERIA.  
 
BEHIND THE SURFACE LOW...SOME LINGERING NW FLOW SNOW SHOWERS WILL  
PERSIST AT HIGHER ELEVATIONS INTO THURSDAY...WHILE LOWER ELEVATIONS  
OF THE MOUNTAINS CHANGE OVER TO RAIN. THE EVENT IS EXPECTED TO WIND  
DOWN QUICKLY THURSDAY EVENING. GUSTY NE WINDS WILL DELIVER ENOUGH  
COLD ADVECTION TO OVERCOME DOWNSLOPE WARMING AND BRING TEMPERATURES  
TO AROUND 10 DEGREES BELOW NORMAL ON THURSDAY AND THURSDAY NIGHT.  
GUSTY WINDS ABATE ON FRIDAY AS A SURFACE HIGH MOVES OVER THE  
AREA....WHILE HIGH TEMPERATURES REMAIN ABOUT 10 DEGREES BELOW NORMAL.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
 
 
AS OF 215 PM TUESDAY...QUASI-ZONAL 500 MB FLOW ACRS THE CONUS TO  
START OUT THE MEDIUM RANGE 00Z SAT...THEN A GRADUAL  
AMPLIFICATION...WITH ONE TROF SWEEPING ACRS THE GREAT LAKES...AND  
ANOTHER ENTERING THE WEST COAST OVER THE WEEKEND. UPPER RIDGING WILL  
PERSIST ACRS THE SOUTHEAST STATES...ALBEIT FAIRLY FLAT. AT THE  
SFC...A MODERATING HIGH PRES WILL SETTLE ACRS THE CAROLINAS...GA AND  
FL. WITH PERSISTENT WESTERLY 850 MB AND INCREASING  
THICKNESSES...EXPECT TEMPS TO REBOUND FROM A COUPLE CATEGORIES BELOW  
NORMAL SATURDAY...TO 2-3 CATEGORIES ABOVE NORMAL BY MONDAY. THE  
ECMWF AND GFS CONTINUE TO DISAGREE ON HOW BULLISH A BACKDOOR COLD  
FRONT IS IN PUSHING SOUTH THRU THE AREA MONDAY NIGHT THRU TUESDAY.  
THE 12Z/25 ECMWF IS STRONGER WITH A SFC HIGH AS IT SLIDES INTO THE  
NORTHEAST STATES...AND KEEPS MORE MOISTURE ATOP A WEDGE DURING THE  
DAY ON TUESDAY. THE GFS KEEPS THE FRONT AND MOISTURE MAINLY NORTH OF  
THE AREA THRU TUESDAY NIGHT. I WENT WITH THE 12Z HPCGUIDE...WHICH  
WAS BASED ON ECWMF ENS...WHICH IS NOT AS BULLISH AS THE OP  
ECWMF...BUT DOES INCREASE CLOUDINESS AND BRING SLIGHTLY COOLER TEMPS  
ON TUESDAY. OTHERWISE...EXPECT GENERALLY CLEAR TO PARTLY CLOUDY  
SKIES AND DRY CONDITIONS. SOME SLGT TO LOW-END CHC POPS WILL EXIST  
ALONG THE TN BORDER...AS MOISTURE IS LIFTED WITH PERSISTENT WESTERLY  
UPSLOPE FLOW...SUNDAY THRU TUESDAY.  
 

 
   
AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
 
 
AT KCLT...LATEST RADAR INDICATED A BAND OF LIGHT RAIN OR VIRGA  
ACROSS THE PIEDMONT...EAST OF CLT. THIS BAND IS PRIMARILY LOCATED  
NW OF A BAND OF FRONTOGENESIS. THE NAM INDICATES THAT H7  
FRONTOGENESIS WILL LIFT NORTHWARD THIS EVENING...REACHING THE I-85  
CORRIDOR BY 3Z. LARGE SCALE LIFT SLIDE ACROSS THE REGION AROUND  
SUNRISE...RESULTING IN THE GREATEST PRECIP RATES. BASED ON THE  
TIMING AND PLACEMENT OF FORCING...RA SHOULD BEGIN AT CLT AROUND 2Z  
AND REMAIN THROUGH MID DAY WED. FORECAST SOUNDINGS SHOW CEILINGS  
FALLING TO MVFR BY 2Z...WITH IFR EXPECTED BETWEEN 10Z-14Z. IT IS  
INTERESTING THAT THE FRONTOGENESIS TRACKS OVER CLT AROUND 12Z. IF  
HEAVY SHOWERS DEVELOP...IT IS POSSIBLE A PERIOD OF RASN COULD OCCUR  
DURING THE 12-15Z WINDOW. WINDS WILL REMAIN FROM THE NE THROUGH  
TONIGHT...WITH NW WINDS BY 14Z.  
 
ELSEWHERE...CONDITIONS WILL REMAIN SIMILAR TO CLT. HOWEVER...KAVL  
IS EXPECTED TO SEE RASN BY 7Z...MIXING OVER TO SN BY 9Z.  
ACCUMULATING SNOW IS EXPECTED OT KAVL BY SUNRISE. ELSEWHERE...PRECIP  
SHOULD FALL AS A COLD RAIN WITH MVFR TO IFR CEILINGS LATE TONIGHT  
INTO WED MORNING. PRECIP WILL END FROM THE SW TO THE NE THROUGH THE  
AFTERNOON HOURS.  
 
OUTLOOK...ANOTHER ROUND OF SCATTERED RAIN SHOWERS SOUTH AND  
RAIN/SNOW SHOWERS NORTH WILL IMPACT THE AREA WED NIGHT INTO THU  
MORNING. A DRY AIR MASS WILL THEN RETURN TO THE AREA THU NIGHT  
THROUGH THE WEEKEND.  
 
CONFIDENCE TABLE...  
 
00-06Z 06-12Z 12-18Z 18-00Z  
KCLT HIGH 97% HIGH 93% HIGH 95% HIGH 96%  
KGSP HIGH 97% MED 76% HIGH 80% HIGH 95%  
KAVL HIGH 100% HIGH 80% HIGH 93% HIGH 100%  
KHKY HIGH 100% HIGH 86% HIGH 90% HIGH 100%  
KGMU HIGH 100% HIGH 81% HIGH 88% HIGH 95%  
KAND HIGH 97% MED 76% HIGH 86% 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...WINTER WEATHER ADVISORY UNTIL 4 PM EST WEDNESDAY FOR NCZ501-  
503-505.  
WINTER STORM WARNING UNTIL 4 PM EST WEDNESDAY FOR NCZ033-049-  
050.  
WINTER WEATHER ADVISORY UNTIL NOON EST WEDNESDAY FOR NCZ048-  
051>053-059-063-064.  
SC...NONE.  
 

 
 

 
SYNOPSIS...RWH  
NEAR TERM...NED  
SHORT TERM...JAT  
LONG TERM...ARK  
AVIATION...NED  
 
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