Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 161133
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
733 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 645 AM...PATCHY SHOWERS CONTINUE ACROSS THE REGION...MAINLY
SOUTH AND WEST OF THE FORECAST AREA. WILL MAINTAIN A SLIGHT CHANCE
FOR SHOWERS ALONG THOSE FRONTS THROUGH THE MORNING. OTHERWISE...
FOG/LOW STRATUS MAY GET BRIEFLY WORSE SHORTLY AFTER SUNRISE...BEFORE
RAPID IMPROVEMENT OCCURS LATER THIS MORNING.

NW FLOW WILL BECOME ESTABLISHED BY LATE THIS MORNING...IN THE WAKE
OF DEPARTING MID-LEVEL SHORT WAVE/ATTENDANT SURFACE TROUGH. A BIT OF
MID-LEVEL DRY AIR SHOULD ALSO FILTER IN...WITH THE UPSHOT BEING
MINIMAL CHANCES FOR PRECIP FOR THE REMAINDER OF THE MORNING...
ALTHOUGH A STRAY SHOWER WILL BE POSSIBLE ACROSS THE FAR WESTERN NC
MTNS WITHIN NW/UPSLOPE FLOW. THE NW FLOW SHOULD ALSO ACT TO SCOUR
THE LOW CLOUDS IN FAIRLY QUICK FASHION WITHIN A COUPLE OF HOURS OF
SUNRISE...AND MOST LOCATIONS SHOULD SEE NO WORSE THAN PARTLY CLOUDY
SKIES BY LATE MORNING.

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 /12Z TUESDAY THROUGH SATURDAY/...
AT KCLT...LIFR/IFR CIGS ARE EXPECTED TO CONTINUE THROUGH AT LEAST
14Z...BUT WITH INCREASING DOWNSLOPE FLOW COMBINING WITH DAYTIME
HEATING...CIGS ARE EXPECTED TO LIFT/SCATTER RATHER QUICKLY
AFTERWORDS...WITH VFR CONDITIONS LIKELY BY NOON-ISH. THAT BEING
SAID...MORE HEATING SPELLS MORE INSTABILITY...AND SCATTERED
CONVECTION SHOULD DEVELOP ACROSS THE AREA DURING LATE AFTERNOON/
EARLY EVENING...WARRANTING A PROB30 FOR SHRA AFTER 22Z. WINDS WILL
GENERALLY BE LIGHT NNE TO NNE 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...LIFR/VLIFR CONDITIONS CONTINUE AT KGSP/KGMU/KHKY...WHILE
KAVL APPEARS TO BE SEEING THE INITIAL EFFECT OF AN INCREASING NW UP
VALLEY FLOW...AS CIGS HAVE RECENTLY LIFTED AND SCATTERED THERE.
EXPECT ALL TERMINALS TO SEE AT LEAST A BRIEF PERIOD OF SUB-MVFR
CONDITIONS THROUGH ABOUT 14Z...BUT INCR DOWNSLOPE FLOW COMBINED WITH
DAYTIME HEATING SHOULD RESULT IN CIGS LIFTING/SCATTERING RATHER
QUICKLY AFTERWORDS...WITH VFR CONDITIONS LIKELY BY LATE MORNING.
THAT BEING SAID...MORE HEATING SPELLS 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...

            11-17Z        17-23Z        23-05Z        05-11Z
KCLT       LOW   57%     HIGH 100%     HIGH 100%     HIGH  89%
KGSP       MED   63%     HIGH 100%     HIGH 100%     HIGH  97%
KAVL       HIGH  80%     HIGH 100%     MED   77%     HIGH  93%
KHKY       LOW   47%     HIGH 100%     HIGH 100%     HIGH  86%
KGMU       MED   75%     HIGH 100%     HIGH 100%     HIGH  91%
KAND       MED   76%     HIGH  99%     HIGH 100%     HIGH  94%

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...JDL
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...JDL






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