National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KGSP 170234
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1034 PM EDT THU MAY 16 2013

.SYNOPSIS...
A WARM AND INCREASINGLY MOIST AIR MASS WILL REMAIN OVER THE REGION
THROUGH THE REST OF THIS WEEK. A MID LEVEL DISTURBANCE WILL MOVE
ACROSS THE CAROLINAS THIS WEEKEND... TRIGGERING A MORE UNSETTLED
PATTERN WITH SHOWERS AND THUNDERSTORMS FOLLOWING A MAINLY DIURNAL
TREND THROUGH EARLY NEXT WEEK. A COLD FRONT WILL APPROACH THE
AREA DURING THE MIDDLE PART OF NEXT WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
-- Changed Discussion --
AS OF 1030 PM EDT...ANY REMAINING POPS HAVE BEEN YANKED AS THE BNDRY
LAYER HAS CONTINUED TO COOL. I TRIMMED SKY COVER BACK A BIT. AS
CLOUDS ARE WARMING AND DISSIPATING UPSTREAM THAT WILL PROBABLY BE A
TREND THROUGH THE REST OF THE NIGHT.

AS OF 745 PM EDT...STILL NO SHOWERS OR THUNDERSTORMS OVER THE FA.
THE CONVECTION UPSTREAM OF THE REGION ISN/T ORGANIZED AND IS SHOWING
LITTLE EASTWARD MOVEMENT. WITH WEAK SHEAR AND LIMITED
INSTABILITY...POPS HAVE BEEN REMOVED FOR THE OVERNIGHT HOURS WITH
THE EXCEPTION OF A SLIGHT CHANCE RIGHT ALONG THE TN LINE.

AS OF 545 PM EDT...A SHORT WAVE IS MOVING ACROSS THE FOOTHILLS AT
THIS TIME. CONVECTION NEVER DID FIRE AHEAD OF THE WAVE...AND NVA
BEHIND IT SHOULD SUPPRESS CONVECTION FOR A FEW MORE HOURS. THEREFORE
I/VE REMOVED POPS FOR A WHILE...THOUGH I DO HAVE A PERIOD OF SLIGHT
CHANCE POPS LATER IN THE EVENING AS CONVECTION DEVELOPING OVER THE
CUMBERLAND PLATEAU MAY WORK INTO THE MTNS BY THAT TIME.

AS OF 230 PM EDT...BROAD UPPER LEVEL CLOSED LOW LOCATED OVER THE
OZARKS CONTINUES TO SLOWLY MOVE TO THE EAST...THUS SPREADING MID TO
UPPER LEVEL MOISTURE ACROSS THE SOUTHEASTERN UNITED STATES.
MEANWHILE ON A MORE LOCAL SCALE...LARGE CLOUD SHIELD CONTINUES TO
SPREAD ACROSS NORTHEAST GEORGIA AND THE CAROLINAS...THUS STUNTING
DAYTIME HEATING TRENDS SOMEWHAT.  HOWEVER...MODEL GUIDANCE STILL
INDICATES SBCAPE VALUES HAVE TOPPED THE 1000J/KG MARK ACROSS
PORTIONS OF NORTHEAST GEORGIA...THE NORTHERN PIEDMONT OF SOUTH
CAROLINA...AND THE SOUTHERN MOUNTAIN REGIONS OF NORTH CAROLINA.
STILL EXPECTING SOME CONVECTIVE INITIATION ACROSS THE HIGH TERRAINS
LATER THIS AFTERNOON AS THE CAP WEAKENS...THEREFORE KEPT CHANCE POPS
FOR THIS REGION.

OTHERWISE...EXPECTING CONVECTIVE PROBABILITIES TO DROP DURING THE
OVERNIGHT HOURS DUE TO DIURNAL COOLING EFFECTS.  LOW TEMPS OVERNIGHT
WILL BE SLIGHTLY WARMER THAN LAST NIGHT AS MID TO HIGH CLOUD DECK
WILL REMAIN OVER THE AREA.  FOR FRIDAY...MODEL GUIDANCE INDICATES
THE ABOVE MENTIONED UPPER LOW WILL PASS BY TO THE NORTH THUS
PROVIDING AT LEAST SOME BROAD SCALE LIFTING ACROSS THE AREA.  THIS
COMBINED WITH DIURNAL HEATING IN THE AFTERNOON PROMPTED INCREASES TO
LIKELY POPS ACROSS THE NORTH CAROLINA MOUNTAINS...AND CHANCE POPS
ELSEWHERE.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
SHORT TERM PERIOD CHARACTERIZED BY STEADY AND SUMMER-LIKE SOUTHERLY
FLOW ON WESTERN PERIPHERY OF BERMUDA HIGH...WITH UPPER TROUGH RIDING
OVER SE CONUS RIDGE PROVIDING SOME WEAK FORCING FROM DPVA BUT
ENHANCING LLVL WINDS AND MIDLEVEL LAPSE RATES. FRI NIGHT THE COMBINED
LIFTING EFFECTS OF THE TROUGH AND SOUTHERLY FLOW ARE SUFFICIENT TO
THINK THAT SOME OF THE ELEVATED INSTABILITY SHOWN ON NAM FCST
SOUNDINGS COULD BE REALIZED...SO THOUGH POPS WILL DIMINISH AS
CONVECTION WANES FOLLOWING DIURNAL MAX FRI AFTN IT IS PRUDENT TO
MAINTAIN AT LEAST A SCHC MOST PLACES OVERNIGHT. THE INCREASING LLVL
WINDS FRI NIGHT MAY ENHANCE LLVL LIFT ESPECIALLY NEAR THE BLUE RIDGE
ESCARPMENT TOWARD SAT MORNING ALLOWING FOR INCREASING PRECIP CHANCES.
THE WINDS WILL ALSO MAINTAIN FAIRLY MIXED CONDITIONS JUST ABOVE THE
SFC SO ONCE DIURNAL HEATING BEGINS SATURDAY CONVECTION SHOULD EASILY
BEGIN TO FIRE BY LATE MORNING. CAPE VALUES OF AT LEAST SEVERAL
HUNDRED JOULES FCST BY GFS/NAM CONSENSUS...WITH HIGHEST VALUES OVER
THE PIEDMONT WHERE IT APPEARS SKIES WILL BE CLEARER DUE TO LATER
CONVECTIVE INITIATION ALLOWING FOR BETTER HEATING. SHEAR TOO WEAK TO
SUGGEST A THREAT OF ORGANIZED TSTMS AND DEEP MOISTURE SUFFICIENTLY
HIGH TO LIMIT DOWNBURST THREAT.

SIMILAR STORY FOR SATURDAY NIGHT INTO SUNDAY WITH SOME ELEVATED
CONVECTION POSSIBLY CONTINUING OVERNIGHT AND A FAIRLY EARLY DIURNAL
RISE IN ACTIVITY SUN MORNING UNDER LARGELY THE SAME SYNOPTIC SETUP.
ONE DIFFERENCE IS THAT THE UPPER TROUGH SHOULD BE OVERHEAD
SUNDAY...PERHAPS LIMITING CONVECTION SOMEWHAT DUE TO MORE HIGH
CLOUDINESS...THOUGH ALSO ENHANCING INSTABILITY THROUGH BETTER UPPER
LAPSE RATES. MOISTURE INCREASES THROUGH THE COLUMN BUT ESPECIALLY IN
THE LOW LEVELS WHERE CONDENSATION PRESSURE DEFICITS DECREASE AND MAKE
UP FOR THE CONVECTIVE LIMITATIONS POSED BY THE EXPECTED CLOUD COVER.
HAVE KEPT POPS IN HIGH CHANCE RANGE SUNDAY. THE INCREASED MOISTURE IS
ALSO REFLECTED IN HIGHER PWAT VALUES AT THIS TIME...THE HIGHEST OF
THE PERIOD...SUPPORTING HEFTIER QPF VALUES THOUGH STILL NOT OF GREAT
CONCERN.

LOW TEMPS WILL BE A BIT ABOVE NORMAL ON ACCOUNT OF CLOUD COVER. HIGH
TEMPS WILL BE HELD NEAR NORMAL VALUES WITH THE SOUTHERLY FLOW
OFFSETTING THE LIMITED HEATING BY CLOUD COVER DURING THE PERIOD.
FAVORED COOL SIDE OF GUIDANCE IN THE HIGHER TERRAIN WHERE CLOUD COVER
EXPECTED TO SEE DIURNAL INCREASES EARLIER IN THE DAY.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 102 PM THURSDAY...FOR MONDAY AND TUESDAY...WE ARE STILL
EXPECTING TO BE TRANSITIONING TO S/WV RIDGING ALOFT...LEE TROUGHING
AND MEAN SOUTHERLY LLVL FLOW AROUND BERMUDA HIPRES. BASED ON THIS...
DAILY PCPN CHANCES WILL GRADUALLY LOWER TO JUST TOKEN CLIMO...MAINLY
DIURNAL POPS FOR DEEP CONVECTION BY TUESDAY. MAX TEMPERATURES EACH
DAY ARE SLATED TO BE A FEW DEG F ABOVE CLIMO. UPPER HEIGHTS ATOP THE
SE CONUS LOOK TO STEADILY LOWER THROUGH THE LATTER HALF OF THE
PERIOD WITH UPPER WAVE PROGGED TO DIG FROM THE MIDWEST TO THE OHIO
VALLEY. THE ATTENDANT FRONTAL ZONE MAY ALSO BE IMPINGING UPON OUR
AREA BY DAY 7. WITH THIS POTENTIAL INCREASE IN FORCING...MOISTURE AND
FLOW...DAILY THUNDERSTORM CHANCES...AND PERHAPS INTENSITY...WILL
INCREASE.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
AT KCLT AND ELSEWHERE...VFR CONDITIONS WILL CONTINUE THROUGH THE
ENTIRE TAF PERIOD. MID AND UPPER LEVEL CLOUDS CUT DOWN ON THE
INSTABILITY EARLIER IN THE DAY AND NO SHRA/TSTMS HAVE DEVELOPED OVER
THE REGION. AS WE ARE APPROACHING SUNSET...WE SHOULD BE SHOWER FREE
THE REST OF THE NIGHT. EXPECTING A LITTLE MORE SUN ON FRIDAY...WHICH
SHOULD YIELD ISOLATED TO SCT SHRA/TSTMS OVER THE WRN CAROLINAS.
ADDED PROB30 TO A FEW TAF SITES. THE BEST CHANCES LOOK TO BE OVER
THE MTNS AND FOOTHILLS...AND IN A WEAK CONVERGENCE AXIS OVER THE WRN
NC PIEDMONT...INCLUDING KCLT.

OUTLOOK...SHOWER AND THUNDERSTORM COVERAGE...AND ASSOCIATED
RESTRICTIONS...WILL GRADUALLY INCREASE FRIDAY THROUGH MONDAY. FAIR
WEATHER MAY RETURN BY TUESDAY.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-02Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  89%     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
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...LEV
NEAR TERM...MCAVOY
SHORT TERM...WIMBERLEY
LONG TERM...CSH
AVIATION...MCAVOY