869  
FXUS62 KGSP 190232  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
932 PM EST THU DEC 18 2014  
   
SYNOPSIS
 
 
WEAK HIGH PRESSURE OVER THE REGION ON FRIDAY WILL GIVE WAY TO A  
BRIEF INCREASE IN MOISTURE ALONG WITH CHILLY TEMPERATURES ON  
SATURDAY. DRIER HIGH PRESSURE THEN RETURNS FOR SUNDAY BEFORE AN AREA  
OF LOW PRESSURE BRINGS RAIN CHANCES BACK FOR MONDAY.  
 

 
   
NEAR TERM /THROUGH FRIDAY/
 
 
915 PM UPDATE...CLOUD COVER CROSSING THE MTNS FROM THE TENN VALLEY  
IS BREAKING UP UPSTREAM AS MODELS SUGGESTED...BEING IN THE WAKE  
OF THE SHORTWAVE NOW OVER THE CENTRAL APPALACHIANS. DOWNSLOPING  
HAS HAD SOMEWHAT OF AN IMPACT...AS THE CLOUDS THAT FILLED IN OVER  
THE CWFA AFTER SUNSET NOW ARE BEGINNING TO DISSOLVE. SKIES WILL  
REMAIN MOSTLY CLOUDY OVERALL FOR A COUPLE MORE HRS BUT SHOULD  
BECOME MOSTLY CLEAR BY EARLY MRNG. REVISED SKY GRIDS TO ACCOUNT FOR  
THIS. TEMPS THRU THE LATE EVENING SHOULD BE UNAFFECTED...BUT  
PREVIOUS MINS APPEAR TO BE ON TRACK.  
 
630 PM UPDATE...IN COLLABORATION WITH NEIGHBORING  
OFFICES...REVISED POPS FOR LATE FRI NIGHT AND SATURDAY TO BETTER  
REFLECT GUIDANCE DEPICTION OF THE PRECIP ASSOCIATED WITH THE PASSING  
SRN STREAM WAVE. CATEGORICAL POPS SEEMED TOO HIGH OVER THE NRN  
UPSTATE AND SRN NC PIEDMONT/FOOTHILLS...SO WE REDUCED THEM TO LKLY  
RANGE.  
 
AS OF 220 PM...A VORT MAX WILL STREAK WEST TO EAST FROM THE OHIO  
VALLEY TO THE MID ATLANTIC TONIGHT...WITH THE ONLY REAL EFFECT THIS  
FAR SOUTH BEING A REINFORCING VEERING NWLY LLVL FLOW IN ITS WAKE. SO  
WHILE THERE IS STILL A FAIR AMOUNT OF MID CLOUDS TRYING TO MAKE  
INROADS FROM THE TN VALLEY AND THE GULF STATES...MOST OF THE CLOUDS  
WILL BE FROM PERIODS OF CIRRUS WITHIN A STRONG SUBTROPICAL JET THRU  
FRIDAY. WINDS WILL BE LIGHT AND THE AIR FAIRLY DRY. MIN TEMPS WILL  
BE A CATEGORY OR TWO ABOVE NORMAL (MID-UPR 20S MTNS AND LWR-MID 30S  
PIEDMONT).  
 
ON FRIDAY...ANOTHER POTENT SOUTHERN STREAM SHORTWAVE WILL ENTER THE  
SOUTHERN PLAINS...WITH INCREASING HIGH CLOUDS FOR THE AFTN ATOP THE  
CWFA. LLVL FLOW WILL WEAKEN AND BEGIN TO BACK TO SWLY...WHILE SFC  
HIGH PRES LINGERS ACRS THE GREAT LAKES AND OHIO VALLEY. TEMPS ARE  
EXPECTED TO BE NEAR NORMAL IN THE MTNS...AND A CATEGORY OR TWO ACRS  
THE PIEDMONT.  
 

 
   
SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/
 
 
AS OF 245 PM...BEGINNING FRIDAY NIGHT...SHORT RANGE MODELS INDICATE  
THAT A WEAK INVERTED SURFACE TROUGH WILL DEVELOP NEAR THE  
MISSISSIPPI DELTA. BY 12Z SAT...THE CENTER OF SFC HIGH PRESSURE IS  
FORECAST TO REACH THE GREAT LAKES REGION...RIDGING SOUTHWARD ACROSS  
THE WESTERN CAROLINAS. A H5 TROUGH IS EXPECTED TO RIPPLE ACROSS THE  
DEEP SOUTH...MOISTURE AHEAD OF THE DISTURBANCE WILL ADVECT NORTH  
FROM THE GULF OF MEXICO TO TN. AS THE MID LEVEL WAVE  
APPROACHES...MOISTURE WILL BUILD ACROSS THE SOUTHERN APPALACHIAN  
REGION. HOWEVER...LLVL FLOW WILL REMAIN FROM THE SW AND MODEL  
ISENTROPIC LIFT APPEARS VERY WEAK. AS A RESULT...12Z MODEL RUNS HAVE  
CONTINUED A DRIER TREND. I WILL DELAY POPS UNTIL BETTER MID FORCING  
ARRIVES AROUND SUNRISE SATURDAY. AT THE TIME OF PRECIP  
ARRIVAL...TEMPERATURES ARE FORECAST TO RANGE FROM THE MID TO LOW 30S  
ACROSS THE MTNS TO MID TO UPPER 30S EAST. BASED ON FORECAST  
SOUNDINGS...PRECIP SHOULD FALL AS A MIX OF RA AND SNOW ACROSS THE  
MTNS DURING THE EARLY MORNING HOURS...WITH A COLD RAIN EAST. IN  
ADDITION...FOLLOWING MODEL TRENDS...I HAVE DECREASED QPF ACROSS THE  
CWA ON SATURDAY. SNOWFALL BETWEEN A HALF INCH TO INCH IS STILL  
POSSIBLE ACROSS THE NRN MTNS...ELSEWHERE...LITTLE TO NO ACCUMS.  
HIGHS WILL BE TWEAKED A LITTLE WARMER FROM PREVIOUS  
FORECAST...RANGING IN THE LOW TO MID 40S.  
 
SUNDAY...S/W RIDGING WILL RIPPLE ACROSS REGION AHEAD OF THE NEXT  
AMPLIFYING TROUGH. MIN TEMPERATURES UNDER PARTLY CLOUDY SKY SHOULD  
RANGE FROM THE L30S ALONG I-40 TO U30 ACROSS THE UPPER SAVANNAH  
RIVER VALLEY. MOISTURE WILL SURGE ACROSS THE REGION DURING THE  
AFTERNOON. LLVL WINDS SHOULD BACK FROM THE SOUTH-  
SOUTHEAST...PROVIDING MARGINAL UPSLOPE FLOW. I WILL INCREASE POPS TO  
SCHC ACROSS THE PIEDMONT FOR RAIN. HIGHS SHOULD REMAIN AROUND 3-5  
DEGREES BELOW NORMAL.  
 

 
   
LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/
 
 
AS OF 225 PM THURSDAY...THE MEDIUM RANGE WILL FEATURE A TRANSITION  
TO A HIGHLY AMPLIFIED AND ACTIVE UPPER FLOW PATTERN...AS A DEEP  
EASTERN TROUGH IS EXPECTED TO BECOME ESTABLISHED IN RESPONSE TO A  
SERIES OF POTENT SHORT WAVE TROUGHS DIVING OUT OF THE NORTHERN  
ROCKIES. THE GLOBAL MODELS GENERALLY AGREE IN INITIATING WEAK  
CYCLOGENESIS OFF THE SOUTHEAST COAST ON MONDAY IN ADVANCE OF THE  
FIRST SHORT WAVE. THE GFS AND THE ECMWF RESPOND WITH QPF ACROSS THE  
WESTERN CAROLINAS AND NORTH GEORGIA BY MONDAY MORNING...ALTHOUGH THE  
STRENGTH AND POSITION OF THE CONSENSUS LOW CENTER SUGGESTS PRECIP IS  
HARDLY A SLAM DUNK...THUS POPS WILL BE MAINTAINED IN THE CHANCE  
RANGE IN MOST AREAS. PARTIAL THICKNESS PROGS FROM THE GFS AND ECMWF  
SUGGEST AN ALL-LIQUID EVENT OVER THE VAST MAJORITY OF THE AREA.  
HOWEVER...WITH IN SITU COLD AIR DAMMING POSSIBLY DEVELOPING IN  
RESPONSE TO LIGHT PRECIP FALLING OVER COOL/DRY SURFACE RIDGE...  
LOCATIONS ALONG THE EASTERN BLUE RIDGE ESCARPMENT...PARTICULARLY THE  
NORTHERN MTNS...COULD SEE A BRIEF PERIOD OF FZRA EARLY MONDAY.  
 
THE NEXT WEATHER MAKER APPEARS TO ARRIVE IN THE TUE NIGHT/EARLY WED  
TIME FRAME...WHEN A MORE SUBSTANTIVE WAVE DIVES INTO THE  
SOUTHEAST...POTENTIALLY RESULTING IN A STRONGER SURFACE RESPONSE  
(ALTHOUGH THIS IS NOT ENTIRELY CERTAIN...ESP GIVEN THE DETERMINISTIC  
GFS SOLUTION...WHICH SUGGESTS MORE OF AN OPEN WAVE OVER THE  
SOUTHEAST). HIGHER POPS WILL BE FEATURED DURING THIS TIME FRAME.  
ONCE AGAIN...IT APPEARS THE COLD AIR WILL HOLD OFF UNTIL AFTER THE  
AREA OF DEEP FORCING EXITS THE FORECAST AREA. HOWEVER...POST FRONTAL  
NORTHWEST FLOW COULD RESULT IN SNOW SHOWERS ACROSS THE MTNS WED INTO  
WED NIGHT. THERE WILL ALSO BE THE POTENTIAL FOR SOME THUNDER ACROSS  
THE PIEDMONT AS THE COLD FRONT PASSES THROUGH THE AREA EARLY WED.  
TEMPS WILL GENERALLY BE NEAR-TO-BELOW NORMAL THROUGH THE PERIOD...  
WITH MONDAY EXPECTED TO BE THE COOLEST DAY THANKS TO THE POTENTIAL  
FOR IN SITU CAD.  
 

 
   
AVIATION /03Z FRIDAY THROUGH TUESDAY/
 
 
AT KCLT AND ELSEWHERE...VFR. PATCHY CLOUDS AROUND 050 WILL PASS THRU  
THE REGION THIS EVENING AS A POCKET OF LLVL MOISTURE ARRIVES.  
PERIODS OF CIGS WILL BE SEEN UNTIL THESE CLOUDS MOVE OUT. THE BULK  
OF THE CLOUD COVER OVER THE TENN VALLEY IS EXPECTED TO BE ERODED BY  
THE MOUNTAINS AS IT PUSHES EAST...BUT SCT 050-070 CLOUDS WILL LIKELY  
STILL BE SEEN THRU MRNG. WINDS WILL PREVAIL NW-N BY LATE EVENING AS  
MIXING CEASES...VEERING SLIGHTLY FOR FRIDAY BUT REMAINING LIGHT THRU  
THE DAY. KAVL IS AN EXCEPTION...REMAINING BREEZY OVERNIGHT. CIRRUS  
WILL THICKEN AHEAD OF SHORTWAVE RISING OUT OF THE GULF STATES LATE  
FRI.  
 
OUTLOOK...A MORE ORGANIZED SYSTEM WILL APPROACH FROM THE WEST EARLY  
SATURDAY BRINGING ELEVATED PRECIP/RESTRICTION CHANCES. SOME WINTRY  
PRECIP IS POSSIBLE ACROSS THE NC MTNS AND FOOTHILLS AFFECTING  
KAVL/KHKY SATURDAY MORNING. WINTRY PRECIP IS NOT EXPECTED AT THIS  
TIME FOR ANY OTHER TAF SITES. A WETTER SYSTEM WILL TRACK INTO THE  
AREA FOR MONDAY LIKELY BRINGING SOME RESTRICTIONS.  
 
CONFIDENCE TABLE...  
 
02-08Z 08-14Z 14-20Z 20-00Z  
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...CSH  
NEAR TERM...ARK/WIMBERLEY  
SHORT TERM...NED  
LONG TERM...JDL  
AVIATION...WIMBERLEY  
 
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