529  
FXUS62 KGSP 242215  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
615 PM EDT TUE APR 24 2018  
   
SYNOPSIS
 
 
A SLOWLY MOVING LOW PRESSURE SYSTEM WILL EXIT OUR REGION BY  
LATE TONIGHT. THE ATMOSPHERE WILL DRY BRIEFLY WEDNESDAY BEFORE  
ANOTHER MOIST AREA OF LOW PRESSURE CROSSES THE REGION THURSDAY  
THROUGH EARLY SATURDAY. HIGH PRESSURE BUILDS ACROSS OUR AREA BY THE  
END OF THE WEEKEND.  
 

 
   
NEAR TERM /THROUGH WEDNESDAY/
 
 
AS OF 6PM EST TUESDAY: SHOWERS CONTINUE THIS EVENING WITH SOME  
LIGHTNING PRIMARILY OVER EASTERN PARTS OF THE CWA. SHORT-TERM  
GUIDANCE HAS A DECLINE IN SHOWER ACTIVITY AFTER 8PM, WITH RESIDUAL  
SHOWERS MOVING OUT OF THE AREA TO THE NORTHEAST.  
 
OVERALL COVERAGE OF SHOWER ACTIVITY IS EXPECTED TO GRADUALLY  
DIMINISH INTO THE EVENING, AS UPPER LOW CONTINUES TO WOBBLE TOWARD  
THE SOUTHERN APPALACHIANS, ALLOWING THE LOW LEVEL FLOW TO CONTINUE  
TO WEAKEN WHILE SHIFTING TO MORE OF A DOWNSLOPE REGIME.  
 
THE SURFACE LOW WILL MOVE EAST OF THE AREA TONIGHT, AHEAD OF THE  
UPPER LOW WHICH IS FORECAST TO MOVE ACROSS WESTERN NC OVERNIGHT. THE  
RESULT WILL BE SHUNTING OF THE DEEPER MOISTURE TO OUR EAST AND NORTH  
AS THE LOW LEVEL FLOW TURNS NW/DOWNSLOPE. PRECIP PROBABILITIES  
SHOULD THEREFORE BECOME INCREASINGLY CONFINED TO LIGHT SHOWER  
CHANCES ALONG THE TN BORDER, WHICH WILL PERSIST INTO WED, WHILE  
SKIES SHOULD BEGIN CLEARING EAST OF THE MTNS LATE TONIGHT THROUGH  
THE MORNING. TONIGHT'S MIN TEMPS SHOULD BE A CATEGORY OR TWO ABOVE  
CLIMO IN MOST AREAS, WHILE HIGHS TOMORROW ARE FORECAST TO BE CLOSE  
TO NORMAL.  
 

 
   
SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/
 
 
AS OF 220 PM EDT TUESDAY: THE SHORT TERM FCST PICKS UP AT 00Z ON  
THURSDAY WITH A BRIEF FLATTENING OF THE UPPER PATTERN BEFORE ANOTHER  
UPPER TROF DIGS DOWN ACROSS SOUTHERN ARKANSAS. THE TROF AXIS IS  
EXPECTED TO LIFT UP AND OVER THE CWFA LATE THURS INTO EARLY FRI AS  
ANOTHER TROF DIVES DOWN THE BACKSIDE OF THE BROADER UPPER TROF.  
THIS SECOND TROF AXIS IS NOT EXPECTED TO REACH THE FCST AREA UNTIL  
EARLY SAT, WHICH IS JUST BEYOND THE SHORT TERM PERIOD. AT THE SFC,  
THE LARGE LOW THAT HAS BEEN IMPACTING OUR REGION WILL FINALLY LIFT  
NORTHWARD AND OVER NEW ENGLAND. IN THE LOW'S WAKE, WEAK HIGH PRESSURE  
WILL BRIEFLY MOVE OVER THE AREA FROM THE NORTHWEST. THE HIGH WILL BE  
SHORT-LIVED AS ANOTHER LOW DEVELOPS TO OUR WEST AND APPROACHES THE  
FCST AREA THURS AFTERNOON. THE OPERATIONAL MODELS ARE NOW IN MUCH  
BETTER AGREEMENT WITH THE TIMING AND PLACEMENT OF THIS LOW. IT IS  
EXPECTED TO MOVE OVER THE CWFA LATE THURS/EARLY FRI AND LIFT NORTH  
OF THE AREA LATE FRIDAY. AS FOR THE SENSIBLE FCST, POPS WERE INCREASED  
FOR THE LATER HALF OF THURS AS THE DEEPER MOISTURE ASSOCIATED WITH  
THE LOW OVERSPREADS THE CWFA. THEY REMAIN HIGH THRU EARLY FRI MORNING  
AND THEN TAPER OFF DURING THE REST OF THE DAY. SOME SFC-BASED INSTABILITY  
IS PRESENT THURS AFTERNOON/EVENING, ESPECIALLY OVER OUR SOUTHERN AND  
EASTERN ZONES, SO ISOLATED TO SCATTERED THUNDER IS INCLUDED OVER THOSE  
AREAS. HIGH TEMPS WILL BE ABOUT A CATEGORY BELOW NORMAL FOR THURS AND  
NEAR NORMAL FOR FRI. LOWS ARE EXPECTED TO REMAIN A FEW DEGREES ABOVE  
CLIMATOLOGY BOTH DAYS.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
 
 
AS OF 230 PM TUESDAY: THE EXTENDED FORECAST STARTS AT 00Z SATURDAY  
WITH YET ANOTHER POTENT SHORTWAVE TROUGH ROUNDING THE BASE OF THE  
MEAN LONGWAVE TROUGH OVER THE SOUTHEAST STATES. THE MEDIUM RANGE  
GUIDANCE IS STILL NOT IN GOOD AGREEMENT ON THE DETAILS OF THIS WAVE.  
THE 12Z EC STILL IS THE FURTHER SOUTH AND LEAST PHASED OF THE  
DETERMINISTIC MODELS. IT TAKES THE WAVE ALL WAY TO THE FL PANHANDLE.  
THIS RESULTS IN A RELATIVELY DRY SOLN. THE 12Z GFS STILL ON THE  
WETTER SIDE OF GUIDANCE, KEEPING SHOWERY WX FOR THE AREA ON SATURDAY  
WITH THE SHORTWAVE TRACKING RIGHT THRU THE CAROLINAS. FOR NOW, THE  
WPC PREFERENCE IS TOWARD THE EC SOLN, AND RESULTS IN ONLY SLGT CHC  
POPS FOR SATURDAY. TEMPS WILL BE NEAR NORMAL.  
 
FROM SUNDAY ONWARD, CONDITIONS LOOK DRY WITH TEMPS WARMING ABOVE  
NORMAL FOR THE START OF NEXT WEEK. THE EASTERN TROUGH SHOULD FINALLY  
START TO SHIFT EAST AND AN UPPER RIDGE WILL BUILD IN FROM THE WEST.  
BY NEXT TUESDAY, THE MODELS ARE IN DECENT AGREEMENT ON A FAIRLY  
AMPLIFIED WESTERN TROUGH AND EASTERN RIDGE PATTERN ACROSS THE  
COUNTRY. SFC HIGH PRESSURE WILL DOMINATE OUR WEATHER FOR MONDAY AND  
TUESDAY.  
 

 
   
AVIATION /22Z TUESDAY THROUGH SUNDAY/
 
 
AT KCLT AND ELSEWHERE: SCATTERED TO NUMEROUS SHOWERS CONTINUE TO  
FIRE THIS AFTERNOON ALONG AND NORTH OF A SURFACE BOUNDARY EXTENDING  
ACROSS NORTHERN SC, WITH ACTIVITY PRIMARILY CONCENTRATED ACROSS THE  
NC FOOTHILLS IN RESPONSE TO A SE UPSLOPE FLOW. AN AREA OF WEAK  
INSTABILITY HAS DEVELOPED IN THE VICINITY AND ESPECIALLY SOUTH OF  
THE BOUNDARY, AND THE INTENSITY OF SHOWERS HAS BEEN GRADUALLY  
INCREASING OVER THE PASS HOUR OR SO IN THESE AREAS. WOULD EXPECT AT  
LEAST A FEW OF THESE TO DEVELOP INTO TS, WITH THE BEST CHANCE FOR TS  
EXISTING AT KAND AND KCLT, WHERE TEMPOS FOR -TSRA ARE CARRIED FOR A  
WHILE THIS AFTERNOON INTO THE EVENING. OTHERWISE, IFR TO LMVFR  
CLOUDS WILL PERSIST NORTH OF THE BOUNDARY THROUGH MUCH OF THE  
AFTERNOON, ALTHOUGH WE DO EXPECT MOST SITES IN THESE AREAS TO LIFT  
ABOVE THE IFR LEVEL BY MID-AFTERNOON. AS THE FLOW BEGINS TO TURN  
AROUND TO MORE OF A DOWNSLOPE REGIME, CIGS MAY IMPROVE TO VFR (OR  
EVEN SCATTER BY LATE EVENING), ALTHOUGH AMPLE LOW LEVEL MOISTURE  
COULD ALLOW STRATUS AND/OR FOG TO FILL BACK IN OVERNIGHT, BUT  
OVERALL CONFIDENCE IN FLT CONDITIONS IS FAIRLY LOW TOMORROW MORNING.  
GENERALLY E/NE WINDS WILL GRADUALLY WEAKEN THROUGH THE EVENING WHILE  
TURNING TOWARD THE NW AT MOST TERMINALS.  
 
OUTLOOK: AFTER VERY BRIEF DRYING WEDNESDAY, MOISTURE AND UNSETTLED  
WEATHER MAY QUICKLY RETURN WEDNESDAY NIGHT INTO THURSDAY AS A TROUGH  
OF LOW PRESSURE REDEVELOPS ACROSS THE EASTERN PART OF THE COUNTRY. A  
DRIER COLD FRONT WILL LIKELY CROSS THE REGION BY THE EARLY WEEKEND.  
 
CONFIDENCE TABLE...  
 
22-04Z 04-10Z 10-16Z 16-18Z  
KCLT HIGH 80% HIGH 83% LOW 56% HIGH 81%  
KGSP MED 69% HIGH 91% LOW 38% HIGH 100%  
KAVL HIGH 94% HIGH 80% HIGH 90% HIGH 84%  
KHKY HIGH 80% HIGH 80% LOW 45% HIGH 81%  
KGMU MED 69% HIGH 100% LOW 55% HIGH 100%  
KAND HIGH 97% 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:  
 
WWW.WEATHER.GOV/GSP/AVIATION  
 

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

 
 

 
SYNOPSIS...CARROLL  
NEAR TERM...JDL/WJM  
SHORT TERM...JPT  
LONG TERM...ARK  
AVIATION...JDL  
 
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