Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 270556
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
156 AM EDT MON JUL 27 2015

.SYNOPSIS...
WEAK BERMUDA HIGH PRESSURE WILL REMAIN OVER THE AREA WITH TYPICAL
SUMMERTIME CONDITIONS INTO MONDAY. THE CENTER OF A STRONG MID LEVEL
RIDGE WILL SLIDE WEST THROUGH THE WORK WEEK. A WEAK COLD FRONT WILL
THEN APPROACH THE REGION BY THE END OF THE WEEK...WITH INCREASING
CHANCES FOR AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS EACH DAY.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 150 AM...RECENT OBSERVATIONS INDICATES THAT PIEDMONT AREAS HAD A 8
TO 9 DEWPOINT DEPRESSION. LATEST MOS AND FORECAST SOUNDINGS INDICATE
THAT DEPRESSIONS MAY CLOSE TO 3 TO 4 DEGREES BY SUNRISE...TOO WIDE
TO MENTION FOG. OBS AND MOS SHOW THE CLOSEST DEPRESSIONS WITHIN THE
MTN VALLEYS. I WILL UPDATE THE FORECAST TO ADJUST THE FOG MENTION.
IN ADDITION...I WILL REDUCE POP AND CLOUD COVER.

0200 UTC UPDATE...POPS HAVE FINALLY BEEN ALLOWED TO DECREASE IN THE
NC MOUNTAINS PER RADAR TRENDS...ALTHOUGH IT MAY TAKE SOME TIME FOR
PRECIPITATION TO EXPIRE COMPLETELY.

0120 UTC UPDATE...POPS AND QPF WERE AGAIN RAISED IN THE NC
MOUNTAINS...MOST NOTABLY IN THE ASHEVILLE AREA WHERE PRECIPITATION
PERSISTS. WINDS WERE UPDATED TO INCORPORATE THE LATEST ADJMAV
GUIDANCE.

0010 UTC UPDATE...POPS WERE RAISED PER RADAR TRENDS...RESULTING IN AN
INCREASE OVER THE SW AND CENTRAL NC MOUNTAINS...AND THE FAR N GA
MOUNTAINS...AND THE SC MOUNTAINS.

2315 UTC UPDATE...SKY COVER WAS UPDATED FROM VISIBLE SATELLITE
IMAGERY...FAVORING THE SW NC MOUNTAINS FOR BEST COVERAGE. WINDS WERE
UPDATED TO INCORPORATE THE LATEST NAM GUIDANCE...FAVORING A SOUTHERLY
DIRECTION.

2010 UTC UPDATE...POPS AND QPF HAVE BEEN UPDATED PER THE LATEST
RADAR TRENDS. SKY COVER HAS BEEN UPDATED PER VISIBLE SATELLITE
IMAGERY.

AS OF 230 PM...UPPER PATTERN CONTINUES TO FEATURE A BROAD UPPER RIDGE
CENTERED OVER THE SRN PLAINS AND A TROUGH OVER THE EAST COAST. THIS
PATTERN WILL REMAIN STAGNANT OVER THE NEXT 24 HRS. PER LATEST GOES
IMAGERY...CURRENTLY SEEING THE BEST CUMULUS OVER THE MTN RIDGELINES.
RADAR IS PICKING UP A COUPLE OF SHOWERS ALONG THE SAME RIDGES AS
WELL. OVERALL THE MESO MODELS ARE NOT ESPECIALLY RESPONSIVE THIS
AFTERNOON...ON ACCOUNT OF POOR LAPSE RATES ASSOCIATED WITH OUR
POSITION DOWNSTREAM OF THE RIDGE. THE MODELS KEEP THE CELLS THEY DO
DEVELOP OVER THE HIGH TERRAIN...NOT JUST BECAUSE OF POORER LAPSE
RATES AS ONE HEADS EAST...BUT ALSO GIVEN WEAK STEERING FLOW. PWAT
VALUES ARE SOMEWHAT LIMITED ON ACCOUNT OF DRY PROFILES...SO HEAVY
RAIN IS NOT OF GREAT CONCERN DESPITE THE EXPECTATION OF SLOW MOVING
CELLS.

A SHORTWAVE ROUNDING THE CENTRAL CONUS RIDGE WILL HELP AMPLIFY THE
TROUGH DURING THE DAY MONDAY. IT APPEARS MOST IF NOT ALL OF THE
DYNAMIC FORCING ASSOCIATED WITH THIS WAVE WILL PASS BY TO OUR NORTH
AND EAST. HOWEVER THE LOWER HEIGHTS/COOLER TEMPS ALOFT WILL IMPROVE
LAPSE RATES AND ONCE AGAIN MAKE DEEP CONVECTION FEASIBLE ACROSS THE
CWFA. EVEN THEN...INSTABILITY IS EXPECTED TO REMAIN BELOW
CLIMATOLOGICAL VALUES. THE FCST WILL REFLECT MAINLY SHOWERS...WITH
ANY TSTMS LIKELY TO REMAIN WEAK...PARTICULARLY IN LIGHT OF PROFILES
BEING FAIRLY MOIST.

MINS TONIGHT WILL BE A TAD ABOVE CLIMO...WITH HIGHS TOMORROW 3-5
DEGREES ABOVE...SIMILAR TO THOSE SUNDAY.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
AS OF 230 PM EDT SUNDAY...THE SHORT TERM FCST PERIOD INITIALIZES
MONDAY EVENING WITH A BROAD H5 ANTICYCLONE CENTERED OVER THE
SOUTHERN PLAINS WHILE A TROF AXIS SLIDES OUT TO SEA OFF THE EAST
COAST.  AT THE SURFACE...A WEAK COLD FRONT WILL BE ADVECTING SOUTH
FROM THE GREAT LAKES INTO THE OHIO VALLEY REGION.  CLOSER TO
HOME...MODELS FAVOR CONTINUED SOUTHERLY FLOW OVER THE SOUTHEAST
THANKS TO SYNOPTIC INFLUENCES FROM BERMUDA HIGH.  PREVIOUS GUIDANCE
TRENDED TOWARD POSSIBLE TROPICAL DEVELOPMENT FROM A REGION OF LOW
PRESSURE THAT IS CURRENTLY ROTATING OVER CENTRAL FL...HOWEVER LATEST
RUNS FAVOR LESS ORGANIZATION AND THUS ONLY INDICATE EJECTION OF SAID
SFC DISTURBANCE OUT TO SEA.  EXPECTING ONGOING MTN CONVECTION AT
FCST INITIALIZATION WHERE GUIDANCE FAVORS THE MOST UNSTABLE AIRMASS
WILL RESIDE.  LACK OF SUBSTANTIAL DRY AIR IN THE PROFILES EAST OF
THE MTNS WILL WORK TO LIMIT LAPSE RATES THUS ANY CONVECTION SHOULD
BE LESS DENSE/ROBUST THAN OVER THE MTNS.

PROFILES ON TUESDAY DRY OUT SOMEWHAT AS THE ABOVE MENTIONED COLD
FRONT LINGERS TO THE NORTH THUS ALLOWING FOR SUBSTANTIALLY MORE CAPE
AS LOW/MID LEVEL LAPSE RATES STEEPEN.  CIN WILL LIKELY KEEP SAID
CONVECTION AT BAY THROUGH MORNING BEFORE ANY CAPPING IS ERODED OVER
THE MTNS ALLOWING FOR INITIATION AROUND MIDDAY.  MODELS FAVOR
EAST/SOUTHEAST STORM MOTIONS ON TUESDAY THUS EXPECTING ANY WESTERN
NC CONVECTION TO PROPAGATE INTO NORTHEAST GA AND THE NC/SC FOOTHILLS
AND PIEDMONT WHERE ADDITIONAL DEVELOPMENT COULD ALSO BE ONGOING.
NAM SOUNDINGS DUE EXHIBIT UPWARDS OF 2.5-3.0K J/KG SBCAPE ALONG WITH
FREEZING LEVELS AROUND 14.5KFT WHICH WOULD SUPPORT DEEP CONVECTION
CAPABLE OF LARGE HAIL AND DAMAGING WINDS ALONG WITH HEAVY RAINFALL
AS PWATS REMAIN AROUND THE 2IN MARK.  THAT SAID...THE USUALLY MORE
TAME GFS IS SOMEWHAT RESERVED WITH CAPES GENERALLY 800-1000J/KG
LESS.  THINK THE NAM DEWPOINTS ARE A TAD OVERDONE THEREFORE LEANING
MORE SO TOWARDS THE GFS WHICH WOULD STILL YIELD SCATTERED TO
WIDESPREAD CONVECTION...HOWEVER AT GENERAL THUNDER LEVELS WITH
PERHAPS A FEW STRONGER CELLS.  THE OVERALL PATTERN REALLY DOESNT
CHANGE ALL THAT MUCH ON WEDNESDAY...HOWEVER THE NAM DOES INDICATE A
FAIRLY SUBSTANTIAL NEGATIVE DEWPOINT FLUX LEADING TO MUCH MORE
STABLE PROFILES RELATIVE TO TUESDAY.  THIS INCONSISTENCY WAS ALSO
ANOTHER REASON THE FCST LEANED ON THE GFS/ECMWF WHICH WAS NEARLY A
CARBON COPY BOTH DAYS.  TEMPERATURES THROUGH THE SHORT TERM WILL
REMAIN AT OR JUST ABOVE NORMAL AS THE UPPER RIDGE CONTINUES TO
DOMINATE.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 2 PM SUNDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
THURSDAY WITH STEEP UPPER RIDGING CENTERED OVER NEW ENGLAND AND A
NORTHERN STREAM UPPER TROF MOVING ACROSS THE NORTHERN GREAT LAKES.
ON THURS...THE UPPER TROF WILL OPEN UP AS IT MOVES EASTWARD AND
BECOMES MORE NEGATIVELY TILTED. THIS WILL SUPRESS THE UPPER RIDGE
OVER OUR REGION AND HEIGHTS WILL FALL A FAIR AMOUNT. BROAD UPPER
TROFFING IS EXPECTED TO REMAIN IN PLACE OVER THE NE CONUS FOR THE
REMAINDER OF THE PERIOD WITH UPPER RIDGING RESTRENGHTENING OVER THE
WESTERN CONUS AND PERSISTING BEYOND DAY 7. AT THE SFC...A WEAK COLD
FRONT ASSOCIATED WITH THE UPPER TROF WILL MOVE OVER THE FCST ON
THURS. THE LATEST MODEL GUIDANCE SHOWS A LESS DEFINED FRONT OVERALL
WITH LESS DEEP LYR MOISTURE ASSOCIATED WITH THE FROPA. AS THE FRONT
DISSIPATES TO OUR SE...SFC RIDGING WILL SPREAD BACK OVER THE CWFA
FROM THE NW ON FRI AND LINGER INTO THE WEEKEND. AT PRESENT...THE
MODELS APPEAR TO BE LESS BULLISH WRT THE DEVEOPMENT OF A SFC LOW TO
OUR SOUTH. BOTH THE GFS AND ECMWF TRY TO DEVELOP SOME SORT OF
LOW...HOWEVER IT REMAINS DIFFUSE AND POORLY ORGANIZED THRU THE
WEEKEND. THEY DO KEEP A HEALTHY AMOUNT OF DEEP LYR MOISTURE OVER THE
EXTREME SE...ESPECIALLY ALONG THE COAST THRU THE WEEKEND...HOWEVER
OUR NW ZONES ARE LOOKING DRIER. AS FOR THE SENSIBLE FCST...WE CAN
EXPECT DIURNAL CHANCES FOR SCT TO WIDESPREAD CONVECTION EACH
DAY/EVENING WITH INCREASING CHANCES FOR WIDESPREAD CONVECTION ON FRI
AND SAT AS THE POTENTIAL FOR A LOW TO DEVELOP TO OUR SOUTH REMAINS
DECENT. TEMPS WILL START OUT JUST ABOVE NORMAL AND ARE EXPECTED TO
DROP BELOW NORMAL OVER THE WEEKEND.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AT KCLT...VFR CONDITIONS EXPECTED THROUGH THE 6Z TAF PERIOD. RECENT
OBSERVATIONS INDICATES THAT KCLT AREA HAD A 8 TO 9 DEWPOINT
DEPRESSION. LATEST MOS AND FORECAST SOUNDINGS INDICATE THAT
DEPRESSIONS MAY CLOSE TO 3 TO 4 DEGREES BY SUNRISE...TOO WIDE TO
MENTION FOG. LIGHT SOUTH WINDS SHOULD DEVELOP WITH MIXING THIS
MORNING...THEN STRENGTHENING TO 6 KTS DURING THE HEAT OF THE
AFTERNOON. INSTABILITY APPEARS LIMITED TO LESS THAN 500 J/KG THIS
AFTERNOON. HOWEVER...CAMS INDICATE THAT A TSRA CLUSTER MAY DEVELOP
NEAR KGSO LATE THIS AFTERNOON...THEN SLIDE SE THROUGH EARLY THIS
EVENING. COVERAGE OF ANY CONVECTION SHOULD REMAIN EAST OF KCLT...SO
NO MENTION WILL BE INCLUDED IN THE TAF.

ELSEWHERE...WIDE DEWPOINT DEPRESSION ACROSS THE WESTERN CAROLINAS
WILL LIMIT FOG DEVELOPMENT THIS MORNING. LATEST OBS AND MOS SHOW THE
CLOSEST DEPRESSIONS WITHIN THE MTN VALLEYS. I WILL INCLUDE A TEMPO
FROM 10Z TO 12Z AT KAVL FOR MVFR FOG...ELSEWHERE NO RESTRICTIONS
EXPECTED. MIXING TO 5 TO 6KFT THIS AFTERNOON SHOULD RESULT IN
DEWPOINTS FALLING IN THE LOW TO MID 60S. INSTABILITY ACROSS THE
REGION SHOULD REMAIN WEAK...WITH THE GREATEST VALUES OVER THE MTNS.
I WILL GIVE KAVL A MID TO LATE AFTERNOON PROB30...ELSEWHERE
TERMINALS APPEAR DRY. WINDS SHOULD FAVOR A LIGHT SOUTH WIND DURING
THE DAYLIGHT HOURS...KAVL NNW.

OUTLOOK...A MID LEVEL RIDGE WILL REMAIN ACROSS THE WESTERN CAROLINAS
THROUGH MID WEEK. A LONGWAVE TROUGH WILL AMPLIFY ACROSS THE ATLANTIC
STATE LATE IN THE WEEK...WITH THE LIKELY PASSAGE OF A COLD FRONT ON
FRIDAY. THE POTENTIAL FOR CONVECTION WILL INCREASE EACH DAY THIS
WEEK.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  97%     HIGH  97%     HIGH 100%     HIGH  88%
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...JPT
NEAR TERM...NED/WIMBERLEY
SHORT TERM...CDG
LONG TERM...JPT
AVIATION...NED


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