073  
FXUS62 KGSP 262353  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
753 PM EDT FRI MAY 26 2017  
   
SYNOPSIS
 
 
WEAK, DRY HIGH PRESSURE CENTERED OVER FLORIDA WILL ALLOW A WEAK COLD  
FRONT TO SLIDE SOUTH ACROSS KENTUCKY AND THE VIRGINIAS ON SATURDAY.  
MOISTURE AND UNSTABLE CONDITIONS WILL RETURN TO THE REGION OVER THE  
WEEKEND, AS THIS COLD FRONT SLOWLY APPROACHES FROM THE NORTHWEST  
INTO THE START OF THE UPCOMING WEEK.  
 

 
   
NEAR TERM /UNTIL 6 AM SATURDAY MORNING/
 
 
AS OF 730 PM EDT: THE CURRENT FORECAST FOR THE VERY NEAR TERM  
REMAINS ON TRACK. MINOR ADJUSTMENTS HAVE BEEEN MADE TO THE SATURDAY  
AFTERNOON PERIOD TO ADJUST POPS UP A BIT AS DETAILED BELOW.  
 
THE LOW AMPLITUDE RIDGE OVER THE REGION WILL CONTINUE TO GRADUALLY  
BREAK DOWN TONIGHT THROUGH SATURDAY. A SERIES OF WEAK VORT MAXES,  
SOME OF WHICH ARE LIKELY CONVECTIVELY-INDUCED, WILL PASS THROUGH THE  
RIDGE INTO THE EASTERN CONUS OVER THE NEXT 24-36 HOURS. MEANWHILE,  
SIGNIFICANT THERMODYNAMIC CHANGES ARE EXPECTED TO OCCUR ACROSS OUR  
AREA OVER THE NEXT 24 HOURS, AS LOW LEVEL MOISTURE INCREASES ON THE  
HEELS OF INCREASING W/SW FLOW, WHILE EXPANSIVE ELEVATED MIXED LAYER  
AIR WILL YIELD VERY IMPRESSIVE MID-LEVEL LAPSE RATES (7-8 C/KM)  
ACROSS THE REGION THROUGH THE DAY TOMORROW. THE RESULT IS FORECAST  
SBCAPE VALUES OF 2000+ J/KG ACROSS THE TN VALLEY AND SOUTHERN  
APPALACHIANS BY LATE AFTERNOON. FORECAST SOUNDINGS ARE QUITE CAPPED  
AND CHARACTERIZED BY HIGH LFCS UNTIL ABOUT LATE AFTERNOON. THIS WILL  
BE AROUND THE TIME THAT SOME OF THE HIGHER RESOLUTION GUIDANCE  
DEPICTS A MID-LEVEL VORT MAX MOVING ACROSS THE TN VALLEY, WHERE THE  
ATMOSPHERE WILL BE LESS CAPPED AND MORE UNSTABLE. THE VERY LATEST  
HI-RES CONVECTION ALLOWING MODELS CONTINUE TO TREND TOWARD BETTER  
CONVECTIVE COVERAGE SURVIVING INTO THE REGION FROM THE WEST. POPS  
HAVE BEEN PUSHED UP INTO A HIGHER CHANCE RANGE OVER WESTERN SECTIONS  
AND INCREASED A BIT OUT EAST ACROSS THE FOOTHILLS AND INTO THE  
PIEDMONT THROUGH LATE SATURDAY AFTERNOON GIVEN THE ROBUST  
INSTABILITY. SUBSTANTIAL LOW LEVEL SHEAR AND HIGH DCAPE COULD  
SUPPORT COLD POOL ORGANIZATION, AND SOME SEVERE WEATHER REMAINS  
POSSIBLE.  
 

 
   
SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/
 
 
AS OF 230 PM FRIDAY: IT LOOKS LIKE A BUSY MEMORIAL DAY WEEKEND  
WITH A CONTINUED THREAT OF ORGANIZED SEVERE WEATHER. THE OVERALL  
PATTERN SHOWS A FLAT UPPER RIDGE ACROSS THE MID-MS VALLEY/TN  
VALLEY/SRN APPALACHIANS/CAROLINAS THROUGH THE PERIOD. THE MODEL  
GUIDANCE SHOWS BITS OF UPPER DIVERGENCE AND VORT MAXES TRUCKING  
ALONG PERIODICALLY THROUGH THIS NEARLY-ZONAL FLOW. IT APPEARS AS  
THOUGH THE NUMERICAL MODELS ARE TRYING TO TELL US THAT WE WILL  
BE IN AN MCS TRACK THROUGH MONDAY. IF THAT WILL INDEED BE THE  
CASE, THE SPECIFICS OF THE MODEL GUIDANCE, SUCH AS THE CONVECTIVE  
PARAMETERS AND PRECIP RESPONSE, ARE PERHAPS LESS IMPORTANT THAN THE  
IDEA THAT WE MAY SEE THUNDERSTORM DEVELOPMENT AND ORGANIZATION AT  
SOME POINT. THE ENVIRONMENT WILL PROBABLY DEVELOP AT LEAST MODERATE  
INSTABILITY WITH SFC-BASED CAPE IN THE 2000-3000 J/KG RANGE ALONG  
WITH SHEAR IN THE 20-30KT RANGE AT SOME POINT, MAINLY TIED TO THE  
DIURNAL CYCLE. THIS WILL SPELL THE BEST CHANCES IN THE AFTERNOON  
AND EVENING, BUT NOT NECESSARILY IF AN MCS DEVELOPS UPSTREAM. AT  
THIS POINT, THE CONVECTION-ALLOWING MODEL GUIDANCE DOES NOT GO  
OUT THAT FAR. WHAT DOES ALL THIS MEAN? UPSTREAM MCSS AND LEFTOVER  
MCVS ARE TOO DIFFICULT TO TIME MORE THAN 24 HRS IN ADVANCE, BUT  
WE EXPECT SOMETHING TO BE LURKING OUT THERE SUNDAY AND MONDAY,  
WHICH MEANS WE WILL HAVE TO BE ON THE LOOKOUT FOR STRONG/SEVERE  
STORMS AT LEAST ON SUNDAY. PRECIP PROBS WILL BE KEPT MAINLY IN  
THE CHANCE RANGE FOR NOW, OWING TO THE UNCERTAINTY AS TO WHEN THE  
MOST LIKELY TIME FOR STORMS WILL BE. TEMPS WILL BE SLIGHTLY ABOVE  
NORMAL THROUGH THE PERIOD.  
 

 
   
LONG TERM /MONDAY THROUGH FRIDAY/
 
 
AS OF 210 PM EDT FRIDAY: STARTING WITH TUESDAY MORNING AFTER THE  
MAIN COLD FRONT HAS PASSED JUST SOUTHEAST OF OUR AREA. AS WEAK HIGH  
PRESSURE WILL BE IN CONTROL OF OUR WEATHER TUESDAY, THERE WILL BE  
VERY LITTLE CONVECTIVE ACTIVITY. EXPECT SLIGHTLY BETTER INSTABILITY  
AND CONVERGENCE WEDNESDAY.  
 
A CLOSED UPPER LOW LOCATED JUST NORTH OF THE GREAT LAKES ON TUESDAY  
CREATES A TROUGH OVER THE EAST. THE CLOSED UPPER LOW OPENS UP LATE  
WEDNESDAY AND MOVES EAST AS ANOTHER COLD FRONT DROPS SE IN RESPONSE  
TO THE CHANGE IN THE UPPER PATTERN. THIS FRONT APPROACHING THE NC  
MOUNTAINS LATE WEDNESDAY SHOULD FURTHER ENHANCE CONVECTION MOVING IN  
FROM TN. A FRONTAL BOUNDARY IS EXPECTED TO LAY OUT FROM WEST TO EAST  
FROM NORTH TX TO NC TO START THE WEEKEND AND GIVE OUR REGION  
SCATTERED TO NUMEROUS SHOWERS AND STORMS. SOME TROFINESS REMAINS  
OVER THE EAST COAST AT THE END OF THE WEEK WITH UPPER RIDGING FROM  
THE MISS VALLEY TO WEST COAST.  
 
TEMPERATURES WILL BE NEAR NORMAL IN THIS EXTENDED PERIOD.  
 

 
   
AVIATION /00Z SATURDAY THROUGH WEDNESDAY/
 
 
AT KCLT AND ELSEWHERE: A SHALLOW UPPER RIDGE WILL KEEP VFR  
CONDITIONS IN PLACE THROUGH SATURDAY MORNING FOR MOST OF THE AREA.  
THE MAIN EXCEPTION WILL LIKELY BE ANOTHER ROUND OF LIFR TO IFR LOW  
CLOUDS AND FOG IN THE SOUTHWEST MOUNTAIN VALLEYS. WINDS WILL REMAIN  
OUT OF THE SW (NW AT KAVL) THROUGH SATURDAY MORNING, WITH SPEEDS  
LESS THAN 10 KT THROUGHOUT. HIGH CLOUDS WILL INCREASE FROM THE WEST  
ON SATURDAY WITH CONVECTION LIKELY DEVELOPING UPSTREAM OVER TN. THE  
LATEST CONVECTION ALLOWING MODELS PERMIT SOME OF THIS ACTIVITY TO  
MOVE ACROSS THE NC MOUNTAINS AND POSSIBLY SURVIVE INTO THE FOOTHILLS  
AND PIEDMONT LATE DAY. PROB30 TSRA WILL BE ADVERTISED THROUGHOUT,  
WITH LOW END AFTERNOON GUSTS EXPECTED IN THE SW FLOW.  
 
OUTLOOK: THUNDERSTORMS AND ASSOCIATED RESTRICTIONS WILL INCREASE  
THROUGH THE LATE WEEKEND WITH COVERAGE MAXIMIZING LATER SUNDAY.  
CONDITIONS MAY REMAIN UNSETTLED THROUGH EARLY TO MIDDLE TO NEXT WEEK  
AS A TRAIN OF UPSTREAM CONVECTION MAY CONTINUE TO RIDE THROUGH THE  
AREA FROM THE WEST FROM TIME TO TIME.  
 
CONFIDENCE TABLE...  
 
00-06Z 06-12Z 12-18Z 18-00Z  
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:  
 
WWW.WEATHER.GOV/GSP/AVIATION  
 

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

 
 

 
SYNOPSIS...ARK  
NEAR TERM...HG/JDL  
SHORT TERM...ARK  
LONG TERM...ARK  
AVIATION...HG/JDL  
 
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