Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KGSP 161501
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
ISSUED BY NATIONAL WEATHER SERVICE COLUMBIA SC
1101 AM EDT TUE SEP 16 2014

.SYNOPSIS...
A COLD FRONT WILL CROSS THE AREA TODAY...ENHANCING CHANCES FOR
SHOWERS AND THUNDERSTORMS THROUGH TONIGHT. IN ITS WAKE...SEASONABLY
COOL AIR WILL SPILL INTO THE REGION WEDNESDAY. THE COOL CONDITIONS
AND MOSTLY DRY WEATHER WILL LAST INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...

AS OF 1055 AM EDT TUESDAY...LATEST VISIBLE SATELLITE IMAGERY ALONG
WITH OBS INDICATE LOW STRATUS/FOG HAS SUBSIDED WITH ONLY A FEW LOW
CLOUDS LINGERING ACROSS THE HIGH TERRAIN. DOWNSLOPING FLOW HAS
AIDED IN STRATUS EROSION ACROSS THE UPSTATE AND NC PIEDMONT REGION
ALLOWING FOR ABUNDANT SUNSHINE TO PREVAIL LEADING TO TEMPERATURES
ALREADY WARMING INTO THE MID TO UPPER 70S AT MOST SITES. DEWPOINTS
CONTINUE TO SURGE ACROSS NORTHEAST GA AND THE WESTERN UPSTATE AS
SOUTHWESTERLY WAA PREVAILS LEADING TO DEWPOINT READINGS IN THE
LOWER 70S. IN RESPONSE...LATEST SPC MESO PLOTS INDICATE AN
INCREASINGLY UNSTABLE AIRMASS RESIDING OVER NORTHEAST GA AND THE
WESTERN CAROLINAS WITH THE SBCAPE MAXIMA ALONG THE I85 CORRIDOR.
THUS FOR THE FORECAST...DID NOT MAKE ANY SIGNIFICANT CHANGES WITH
THIS UPDATE AS LATEST GUIDANCE FAVORS ISOLATED/SCATTERED
CONVECTION THIS AFTERNOON AHEAD OF APPROACHING FRONT IN THE WARM
SECTOR.

PREVIOUS DISCUSSION...

AS OF 845 AM...VERY SPOTTY SHOWERS CONTINUE ACROSS THE REGION...WITH
SLIGHTLY BETTER COVERAGE NOW DEVELOPING CLOSER TO THE FRONT OVER
EXTREME NW NC. WILL MAINTAIN MAINLY ISOLATED LATE MORNING POPS AND
RAMP UP TO MORE SOLID SCATTERED COVERAGE WITH THE FRONT THIS
AFTERNOON. HAVE ALSO TRIMMED MAXES A DEGREE OR SO IN MOST AREAS IN
LINE WITH THE 06Z BIAS CORRECETD MOS AND IN LIGHT OF PREVIOUS DAYS.
OTHERWISE...THE FOG AND LOW STRATUS SHOULD IMPROVE RAPIDLY GIVEN
THE LIGHT DOWNSLOPE FLOW.

A SERIES OF SUBTLE SHORT WAVES IS EXPECTED TO RIPPLE THROUGH THE
DEVELOPING EASTERN TROUGH OVER THE NEXT 24 HOURS...WITH A MODEL
CONSENSUS SUGGESTING THE FIRST ONE WILL APPROACH OUR AREA BY EARLY
THIS EVENING...ALONG WITH AN ACCOMPANYING COLD FRONT. THESE FEATURES
WILL FIND AN AIR MASS WITH LESS DEEP-LAYER MOISTURE CONTENT THAN
WE/VE BEEN SEEING IN RECENT DAYS. HOWEVER...THE ADDITIONAL HEATING
(WITH MAXES EXPECTED TO PEAK NEAR CLIMO) WILL RESULT IN MODERATE
DESTABILIZATION ACROSS THE REGION THIS AFTERNOON. THUS...EXPECT SCT
CONVECTION TO DEVELOP ACROSS THE MTNS BY LATE AFTERNOON...WITH
ACTIVITY TRUCKING EASTWARD FAIRLY QUICKLY IN MODERATELY FAST W/NW
FLOW. SPEAKING OF WHICH...DEEP LAYER SHEAR IS EXPECTED TO BE RATHER
RESPECTABLE TODAY...WITH FORECAST SOUNDINGS DEPICTING BULK 0-6KM
SHEAR OF AROUND 30 KTS. HOWEVER...INSTABILITY IS NOT EXPECTED TO BE
VERY ROBUST (SBCAPE 1500-2000 J/KG)...BUT SOME DEGREE OF MESOSCALE
ORGANIZATION AND A BRIEF SEVERE WIND GUST OR TWO CANNOT BE RULED
OUT.

CONVECTIVE CHANCES WILL LIKELY REACH A NADIR DURING EARLY EVENING...
THEN GRADUALLY DIMINISH TOWARD THE OVERNIGHT HOURS. WITH PLENTY OF
LOW LEVEL JUICE LINGERING...MIN TEMPS SHOULD AVERAGE A LITTLE ABOVE
CLIMO FOR ONE MORE NIGHT BEFORE THE COOLER AIR ARRIVES.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 300 AM TUE...AN AMPLIFIED UPPER PATTERN WILL BE SEEN OVER THE
CONUS DURING THE PERIOD...KEEPING MOST OF THE ERN STATES UNDER A
LONGWAVE TROUGH. HOWEVER THE PATTERN DOES KEEP MOVING AS THE RIDGE
MOVES FROM THE INTERMOUNTAIN WEST INTO THE PLAINS...WITH A WEAK SFC
HIGH BUILDING INTO THE ERN CONUS DOWNSTREAM OF IT. OUR AREA WILL BE
UNDER THE INFLUENCE OF THE WEAK HIGH WEDNESDAY BEFORE A LARGER
CANADIAN HIGH SLIDES IN FOR THURSDAY. A COUPLE OF WEAK SHORTWAVES
BURIED IN THE UPPER FLOW ARE ALSO SHOWN ON THE NAM/GFS/EC...RESOLVED
MORE DISTINCTLY ON THE NAM ON ACCOUNT OF ITS HIGHER RESOLUTION.
MOISTURE PROFILES APPEAR INSUFFICIENT FOR THESE WAVES TO PRODUCE ANY
PRECIP ON THEIR OWN...AND THEY ARE POORLY TIMED TO ENHANCE DIURNAL
CONVECTION WITHIN THE CWFA. IN FACT ON THU THE SUBSIDENCE IN THE WAKE
OF A WAVE APPEARS TO BE ITS BIGGEST IMPACT. THOUGH LAPSE RATES ARE
NOT THAT BAD EITHER DAY...MODELS SUPPORT SCHC POPS ACRS MUCH OF THE
AREA WED. THE GREATER SUBSIDENCE THU LENDS CONFIDENCE TO A DRY FCST.
TEMPS WILL BE A COUPLE CATEGORIES BELOW CLIMO BOTH DAYS THOUGH
CLEARER SKIES THU WARRANT SLIGHTLY WARMER MAXES. THE SFC HIGH AND
TIGHTENING HEIGHT GRADIENT WITHIN THE DOWNSTREAM UPPER TROUGH LINE UP
THU NIGHT TO ALLOW CAD TO FORM WHICH PERSISTS INTO THE WEEKEND.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 200 AM TUE...AS UPPER TROUGH PROGRESSES EWD THRU THE CANADIAN
MARITIMES...EARNEST COLD AIR DAMMING CONTINUES OVER OUR REGION
REINFORCING SEASONABLY COOL TEMPS FRI-SAT. EASTERLY FLOW MAY PRODUCE
SOME CLOUD COVER BUT PRECIP IS NOT EXPECTED. PARENT HIGH MOVES
OFFSHORE FAIRLY QUICKLY BUT THE WEDGE HOLDS ON THRU SATURDAY.
FALLING UPPER HEIGHTS TAKE THEIR TOLL ON IT BY SUNDAY
MORNING...BRINGING RETURN FLOW AHEAD OF A LOW PRESSURE SYSTEM
CROSSING THE GREAT LAKES.  16/00Z GFS AND 15/12Z EC CONTINUE TO
DEPICT THIS SYSTEM DIFFERENTLY BUT BOTH FEATURE A COLD FRONT MOVING
OUT OF THE TENN VALLEY AND INTO OUR AREA EARLY IN THE WEEK. EACH
MODEL AGREES WITH THE PATTERN SEEN ON THEIR OWN PREVIOUS RUNS.
BEYOND THAT THE GENERAL CONSENSUS IS FOR AN AMPLIFYING UPPER
PATTERN...WITH A DEEP ERN CONUS TROUGH CARVING OUT BY NEXT TUESDAY.
TEMPS TREND UPWARD THRU THE PERIOD AS THE WEDGE GIVES WAY AND THE
FROPA OCCURS...BUT AT THEIR WARMEST ARE AROUND CLIMO.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
AT KCLT...CIGS HAVE ALREADY IMPROVED TO MVFR THIS MORNING AND
SHOULD IMPROVE TO VFR BY MID TO LATE MORNING WITH WEAK NW
DOWNSLOPE FLOW DEVELOPING. MORE HEATING WILL MEAN MORE
INSTABILITY...AND SCATTERED CONVECTION SHOULD DEVELOP ACROSS THE
AREA DURING LATE AFTERNOON/ EARLY EVENING...WARRANTING A PROB30
FOR TSRA AFTER 21Z. WINDS WILL GENERALLY BE LIGHT NW FROM LATE
MORNING ON. LINGERING LOW LEVEL MOISTURE COULD SPELL ANOTHER ROUND
OF FOG AND/OR LOW STRATUS LATE TONIGHT...ALTHOUGH THE POTENTIAL
APPEARS TO BE QUITE A BIT LOWER THAN IN PREVIOUS MORNINGS.

ELSEWHERE...ANY LINGERING IFR CONDITIONS SHOULD IMPROVE QUICKLY WITH
A LIGHT DOWNSLOPE FLOW THROUGH THE MID MORNING HOURS...WITH MVFR
LIFTING OR SCATTERING TO VFR BY LATE MORNING. THE BETTER HEATING
WILL MEAN MORE INSTABILITY AND SCATTERED CONVECTION SHOULD DEVELOP
ACROSS THE AREA DURING LATE AFTERNOON/EARLY EVENING...WARRANTING A
PROB30 FOR TSRA AT ALL TERMINALS BEGINNING AROUND 20Z GIVE OR TAKE.
LINGERING LOW LEVEL MOISTURE COULD SPELL ANOTHER ROUND OF FOG AND/OR
LOW STRATUS LATE TONIGHT... ESP AT KAVL. ELSEWHERE...THE POTENTIAL
APPEARS TO BE QUITE A BIT LOWER THAN IN PREVIOUS MORNINGS.

OUTLOOK...ALTHOUGH THE CHANCES FOR DIURNAL CONVECTION WILL GREATLY
DIMINISH AFTER WEDNESDAY...THE POTENTIAL FOR LATE NIGHT/MORNING
FOG/STRATUS WILL PERSIST INTO LATE WEEK...ESP IN THE MTN VALLEYS.
CONDITIONS MAY FINALLY DRY OUT FOR THE WEEKEND.

CONFIDENCE TABLE...

            12-18Z        18-24Z        00-06Z        06-12Z
KCLT       MED   67%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       MED   67%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  86%     HIGH 100%     MED   78%     HIGH  96%
KHKY       LOW   59%     HIGH 100%     HIGH 100%     HIGH  91%
KGMU       MED   79%     HIGH 100%     HIGH 100%     HIGH  95%
KAND       HIGH  82%     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...WIMBERLEY
NEAR TERM...CDG/HG/JDL
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...HG/JDL






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.