109  
FXUS62 KGSP 210751  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
251 AM EST TUE FEB 21 2017  
   
SYNOPSIS
 
 
A FRONTAL BOUNDARY WILL PUSH ACROSS THE AREA LATE TUESDAY AND  
WEDNESDAY, BRINGING A CHANCE FOR SOME MODEST RAINFALL. THIS WILL BE  
FOLLOWED BY BRIEF DRYING, BEFORE ANOTHER FRONTAL SYSTEM BRINGS  
ADDITIONAL CHANCES FOR RAIN AND THUNDERSTORMS HEADING INTO NEXT  
WEEKEND.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
A STRONG ULVL RIDGE AXIS CONTINUES TO TRACK EAST OF THE FA TODAY  
WHILE A CLOSED OFF LOW PUSHES INTO THE NRN GOM. THIS WILL LEAVE THE  
AREA IN A WEAKLY DIFL COL THIS EVENING THRU THE OVERNIGHT PERIOD. AT  
THE SFC...A WEDGE OF HIGH PRESSURE WILL RETREAT NE WITH AN ADVANCING  
WARM FRONT REACHING THE MTNS ARND MIDNIGHT. HIGH CLOUD COVER WILL  
PERSIST AND HELP KEEP A LID ON MAX TEMPS...HOWEVER STILL EXPECT  
HIGHS ABOUT 10 DEGREES ABOVE NORMAL. DUE TO THE WEAK UPPER LEVEL  
FORCING...PRECIP WILL REMAIN LIGHT AND GENERALLY ASSOCIATED WITH  
MECH LIFT ACROSS THE WRN ZONES AND WAA ASCENT TO THE EAST. IT LOOKS  
TO BE A HIGH POP / LOW QPF EVENT. A VERY LIMITED INSTABILITY  
POTENTIAL IS HAD WITH THE NOCTURNAL TIMING AND MID LEVELS REMAIN TOO  
WARM FOR DEEP CONV. THUS...WILL KEEP ALL PRECIP AS -SHRA WITH NO  
THUNDER MENTION. MINS OVERNIGHT SHUD REMAIN QUITE WARM WITH ARND 50  
NON/MTNS AND M40S MTN VALLEYS.  
 

 
   
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
 
 
AS OF 215 AM EST TUESDAY: THE CLOSED UPPER LEVEL LOW PRESSURE SYSTEM  
OVER THE GULF OF MEXICO WEDNESDAY MORNING WILL MOVE SOUTHEAST ACROSS  
THE SOUTHERN TIP OF FLORIDA THROUGH THURSDAY. NORTH OF THIS SYSTEM,  
SOUTHERLY FLOW AT 850 MB WILL CONTINUE THROUGH THE DAY WEDNESDAY TO  
KEEP CLOUDS IN PLACE AND PROVIDE SOME UPSLOPE ENHANCEMENT ALONG THE  
SOUTHERN AND EASTERN SLOPES OF THE MOUNTAINS. MEANWHILE, THE SURFACE  
HIGH CENTER WILL MIGRATE EAST OF THE NC OUTER BANKS BUT EXTEND  
WESTWARD OVER THE FORECAST AREA. THESE FEATURES WILL COMBINE TO KEEP  
PLENTY OF CLOUDS IN THE PICTURE AND CAP MAXIMUM TEMPERATURES AT THE  
LOWER END OF GUIDANCE WEDNESDAY AFTERNOON. THE DEEPER MOISTURE WILL  
PERSIST ACROSS THE NORTHWEST PART OF THE FORECAST AREA WEDNESDAY,  
BUT WITH DWINDLING POP THROUGH WEDNESDAY NIGHT.  
 
SOME MEASURE OF LOW LEVEL UPSLOPE WILL LIKELY PERSIST THURSDAY  
THROUGH THURSDAY NIGHT. IN ADDITION, AS DEWPOINTS CONTINUE TO  
RECOVER THROUGH THE DAY ON THURSDAY, ANTICIPATE DECENT AMOUNTS OF  
SBCAPE MAINLY ALONG AND SOUTHEAST OF I-85 THROUGH THE AFTERNOON  
HOURS. TRIGGERING WILL BE WEAK WITH THE SURFACE RIDGE OVER THE AREA,  
AND LIMITED FORCING ALOFT, BUT ISOLATED TO SCATTERED THUNDERSTORMS  
WILL BE POSSIBLE. TEMPERATURES SHOULD REBOUND SOME 6 TO 8 DEGREES  
OVER WEDNESDAY MAXES.  
 

 
   
LONG TERM /FRIDAY THROUGH MONDAY/
 
 
AS OF 230 AM EST TUESDAY: BY FRIDAY MORNING, AN UPPER RIDGE OVER THE  
EASTERN CONUS WILL AMPLIFY QUICKLY AS A SURFACE COLD FRONT QUICKLY  
APPROACHES THE SOUTHERN APPALACHIANS. WARM, MOIST SOUTHEASTERLY FLOW  
OFF AN UPPER LOW CENTERED OVER THE FL PENINSULA WILL ENSUE AHEAD OF  
THE FRONT DURING THE DAY ON FRIDAY, AND HEATING WILL LIKELY RESULT  
IN A SMALL AMOUNT OF INSTABILITY DEVELOPING, ESPECIALLY ACROSS THE  
OUR SOUTHERNMOST ZONES. THE BEST UPPER FORCING ASSOCIATED WITH THE  
H5 SHORTWAVE WILL NOT ARRIVE UNTIL LATE FRIDAY, WELL AFTER PEAK  
HEATING. ANY INSTABILITY LOOKS QUITE WEAK FRIDAY, AND GENERALLY TOO  
MUCH OUT OF PHASE WITH THE BEST DYNAMICS FOR THE FRONT TO LOOK TOO  
WORRISOME FOR OUR AREA FRIDAY NIGHT. MODELS HAVE BEEN IN GOOD  
AGREEMENT WITH THE FRONT CLEARING OUR ENTIRE AREA BY 18Z  
SATURDAY...WHICH IS A VERY GOOD THING, CONSIDERING BOTH THE LATEST  
GFS AND CMC SPIN UP AN AXIS OF MUCH BETTER INSTABILITY ACROSS THE  
EASTERN PIEDMONT ZONES SATURDAY AFTERNOON. OVERALL, THOUGH, SEVERE  
POTENTIAL IN OUR AREA APPEARS UNIMPRESSIVE BOTH DAYS AT THIS TIME.  
 
A DRY SURFACE HIGH WILL WASTE NO TIME IN BUILDING INTO THE SOUTHEAST  
SATURDAY AFTERNOON AND SUNDAY AS THE UPPER TROUGH SWINGS THROUGH THE  
EASTERN CONUS, BRINGING TEMPERATURES BACK DOWN TO AROUND 10 DEGREES  
ABOVE AVERAGE. A MORE ZONAL REGIME ALOFT WILL SET UP WITH SOUTHERLY  
FLOW AT THE SURFACE BY EARLY NEXT WEEK, AND ANOTHER SYSTEM IN THE  
LOW TRACK WILL APPROACH THE AREA. THERE IS STILL A LARGE AMOUNT OF  
UNCERTAINTY AS TO THE TIMING OF ANY PRECIP AND AVAILABLE MOISTURE BY  
THE TIME THE FRONT ARRIVES, SO POPS WERE KEPT TO CHANCE AT THE END  
OF THE MEDIUM RANGE.  
 

 
   
AVIATION /08Z TUESDAY THROUGH SATURDAY/
 
 
AT KCLT AND ELSEWHERE: BKN/OVC CI WILL PERSIST ACROSS ALL TAF SITES  
THROUGH MOST OF THE PERIOD. MEANWHILE...AN INCREASE IN LLVL MOISTURE  
WILL ADV IN FROM THE ATL THIS MORNING AND GENERATE STCU IN E/WARD  
FACING MECH LIFT. EXPECT MOST SITES LIMITED TO VFR CIGS...HOWEVER  
THE NRN FTHILLS INCLUDING KHKY WILL SEE THE BEST CHANCE FOR MVFR/IFR  
CIGS SHORTLY AFTER OR AROUND DAYBREAK. WINDS WILL REMAIN RATHER  
LIGHT AS A SFC HIGH REMAINS WEDGED ACROSS THE AREA WITH A LOW-END  
AGEO ADJ POTENTIAL. EXPECT -SHRA TO START MOVING IN FROM THE WEST  
ASSOCIATED WITH A WARM FRONT...THUS PROB 30S WILL BEGIN AFT 00Z WEST  
AND BY 04Z AT KCLT.  
 
OUTLOOK: AN AREA OF LOW PRESSURE WILL DRIFT FROM THE SOUTHERN PLAINS  
TO NEAR FL, KEEPING A PERSISTENT MOIST SOUTHERLY FLOW ACROSS THE  
AREA THRU WEDNESDAY. THIS WILL RESULT IN PERIODS OF RESTRICTIONS  
BY WAY OF STRATUS EACH DAY THRU AT LEAST THURSDAY.  
 
CONFIDENCE TABLE...  
 
08-14Z 14-20Z 20-02Z 02-06Z  
KCLT HIGH 100% HIGH 100% HIGH 100% HIGH 87%  
KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 91%  
KAVL HIGH 100% HIGH 100% HIGH 100% HIGH 92%  
KHKY HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KGMU HIGH 100% HIGH 100% HIGH 89% HIGH 84%  
KAND HIGH 100% HIGH 100% MED 68% HIGH 84%  
 
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:  
 
WWW.WEATHER.GOV/GSP/AVIATION  
 

 
   
GSP WATCHES/WARNINGS/ADVISORIES
 
 
GA...NONE.  
NC...NONE.  
SC...NONE.  
 

 
 

 
SYNOPSIS...LEV  
NEAR TERM...SBK  
SHORT TERM...HG  
LONG TERM...LEV  
AVIATION...SBK  
 
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