Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 181745
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
145 PM EDT THU SEP 18 2014

.SYNOPSIS...
A WEAK RIDGE OF HIGH PRESSURE WILL LINGER ATOP THE REGION INTO
SATURDAY. COOL TEMPERATURES WILL RETURN TO NORMAL READINGS ON SUNDAY
AHEAD OF A COLD FRONT WHICH IS FORECAST TO PASS THROUGH ON MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 145 PM...LOW CLOUDS FINALLY CLEARING WITH QUITE A BIT OF LOW
VFR CONVECTIVE CU DEVELOP IN ITS PLACE. STILL A LOW CHC OF
CONVECTION THIS AFTERNOON AND EVENING. HIGHS ON TRACK WITH ONLY
MINOR ADJUSTMENTS.

AS OF 1030 AM...LEADING EDGE OF LOW STRATUS HAS NEARLY STALLED BUT
DID REACH THE NC BLUE RIDGE AND A GSP TO LAURENS LINE ACROSS THE
UPSTATE. SOME OF THE HIGHER BASED STRATOCU TO THE WEST IS
DISSIPATING...BUT CONVECTIVE CU IS BEGINNING TO FORM WHERE CLEAR
SKIES ARE IN PLACE OR DEVELOPING. HAVE UPDATED THE SKY COVER TO SHOW
ONLY A SLOW IMPROVEMENT WHERE THE LOW STRATUS IS AND INCREASING
CLOUDS ELSEHWERE. THAT SAID...THERE SHUD STILL BE QUITE A BIT OF
SUNSHINE ACROSS THE WEST EVEN WITH THE DEVELOPING CU. FCST SOUNDINGS
STILL SHOW UNSTABLE ATMOS...EVEN WHERE THE STRATUS IS IN PLACE.
THEREFORE...THE CURRENT POP FCST STILL LOOKS ON TRACK WITH ISOLATED
TO LOW END SCT CONVECTION. HIGHS ALSO LOOK ON TRACK AS THE CURRENT
FCST ALREADY TOOK THESE TRENDS INTO ACCOUNT.

AS OF 650 AM...WIDESPREAD LOW STRATUS PERSISTS ACROSS THE EASTERN
HALF OF THE AREA THIS MORNING...BUT IS GENERALLY MORE PATCHY ACROSS
WESTERN AREAS...OTHER THAN IN THE MTN VALLEYS. SKIES WILL REMAIN
MOSTLY CLOUDY TO CLOUDY FOR THE NEXT COUPLE OF HOURS...BUT CIGS
SHOULD LIFT/SCATTER RATHER QUICKLY...WITH SOME SUN POSSIBLE BY LATE
MORNING.

STRATOCU CONTINUES TO GRADUALLY EXPAND ACROSS EASTERN AREAS...WHILE
A FAIRLY EXTENSIVE AREA OF MID-LEVEL CLOUDS CONTINUES TO ENCROACH
FROM THE WEST. THIS SHOULD CONTINUE TO PRECLUDE ANY DENSE FOG
CONCERNS EARLY THIS MORNING. OTHERWISE...WITH WEAK MID-LEVEL SHORT
WAVE TROUGH AND UPPER JET ENTRANCE REGION PUSHING EAST OF THE AREA
BY LATE MORNING...WE ARE EXPECTING SCATTERING/LIFTING OF CLOUDS TO
OCCUR A BIT QUICKER THAN IT DID YESTERDAY...WHICH SHOULD RESULT IN
TEMPS WARMING TO NEAR 80 IS MOST AREAS OUTSIDE THE MTNS...AND MID
70S IN THE MTN VALLEYS. AS A RESULT...NAM FORECAST SOUNDING CAPE IS
SURPRISINGLY ROBUST...AROUND 2000 J/KG IN THE PIEDMONT. HOWEVER...IT
IS THE ONLY MODEL THAT FEATURES EVEN ANYTHING APPROACHING THIS
DEGREE OF INSTABILITY. IN FACT...THE SREF /LIKELY PROBABILITY/ OF
CAPE > 500 J/KG IS CONFINED TO A RATHER SMALL AREA AROUND THE
SOUTHERN PERIPHERY OF THE CWFA. MEANWHILE...ONCE THE MID-LEVEL WAVE
PASSES BY LATER THIS MORNING WITH LITTLE FANFARE...THERE WON/T BE
MUCH OF A SIGNIFICANT SOURCE OF RISING MOTION. THEREFORE...WHILE
CONVECTION IS POSSIBLE LATER TODAY...THIS IS CERTAINLY SUPPORTED BY
THE LATEST CONVECTION ALLOWING MODELS...IT SHOULD PRIMARILY BE OF
THE SHOWER VARIETY AND ISOLATED IN NATURE.

TONIGHT...SHORT TERM MODELS DEPICT A BIT OF AN INCREASE IN THE LOW
LEVEL EASTERLY FLOW...ALONG WITH A PERSISTENT QPF RESPONSE...ESP
NEAR THE BLUE RIDGE. POPS WILL THEREFORE INCREASE JUST A BIT
TONIGHT...ESP ALONG THE EASTERN ESCARPMENT...BUT CHANCES ARE STILL
EXPECTED TO BE NO BETTER THAN 30 PERCENT. MIN TEMPS WILL AVERAGE
FAIRLY CLOSE TO CLIMO.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 300 AM THU...SPRAWLING CONTINENTAL HIGH PRESSURE INITIALLY
COVERS MUCH OF THE ERN CONUS FRIDAY MORNING...BUT UPPER PATTERN
REMAINS PROGRESSIVE AND THE HIGH STEADILY SHIFTS OFF INTO THE
ATLANTIC DURING THE PERIOD. AIDED BY CONFLUENCE IN THE CO-LOCATED
ENTRANCE REGION OF A SHORTWAVE...THIS HIGH WILL CREATE A SHORT-LIVED
CAD EVENT AGAINST THE SRN APPALACHIANS. EASTERLY FLOW INITIALLY WILL
WARRANT POPS NEAR THE BLUE RIDGE...BUT AS MOISTURE BECOMES MORE
SHALLOW THRU THE DAY THIS BECOMES A LESSER FACTOR. UPGLIDE OVER THE
WEDGE IS UNIMPRESSIVE...APPEARING CAPABLE OF A FAIR AMOUNT OF CLOUD
COVER BUT NOT MEASURABLE PRECIP. HOWEVER NAM/GFS BOTH INDICATE MODEST
INSTABILITY DURING PEAK HEATING...AND FOR THE AFTN HOURS THAT IS THE
MAIN DRIVER FOR POPS. AT LEAST A SCHC IS INCLUDED EVERYWHERE...WITH
CHC OVER MTN RIDGES. THESE POPS SLOWLY DIMINISH FRI NIGHT AS LLVL RH
CONTINUES TO DROP. MAX TEMPS WILL BE ABOUT TWO CATEGORIES BELOW
CLIMO...WITH MINS NEAR CLIMO SAT MRNG.

THOUGH RIDGING IS SEEN DOWN THE ERN SEABOARD ON SATURDAY THE WEDGE IS
LIKELY TO LOSE ITS GRIP ON THE REGION AS THE PARENT HIGH MOVES
FURTHER AWAY. ISENTROPIC LIFT BECOMES ESSENTIALLY NEUTRAL AND
MOISTURE OVER THE WEDGE IS NOT SUFFICIENT TO EXPECT MUCH CLOUD COVER
TO PERSIST THRU THE DAY. RISING HEIGHTS ARE REFLECTED IN WEAKER LAPSE
RATES ON MODEL PROFILES...BUT AS FAR AS IMPACTING INSTABILITY THIS IS
COUNTERACTED BY WARMER SFC TEMPS. NONETHELESS BLENDED GUIDANCE
SUPPORTS A DRY FCST. TEMPS WILL REBOUND SLIGHTLY...TOPPING OUT A
COUPLE DEGREES BELOW CLIMO SAT AFTN. HOWEVER MINS SHOULD BE A LITTLE
BELOW CLIMO SUN MRNG UNDER CLEARER SKIES.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 1240 PM THU...LESS WARM AIR WILL ADVECT INTO THE REGION ON
MONDAY COINCIDENT WITH THE PASSAGE OF A MOISTURE LACKING COLD FRONT.
THERE REMAINS THE POSSIBILITY OF A ROUND OF MAINLY NC MTN SHOWERS
SUNDAY NIGHT AND MAYBE A FEW SHOWERS EAST OF THE BLUE SOMETIME ON
MONDAY. THE INFLUX OF POST FRONTAL DRIER AIR AND ENCROACHING SFC
RIDGE WILL RESULT IN DRY AND COOLER WX MONDAY NIGHT AND TUE AM MINS
ARE PROGGED TO BE ABT 5 DEG F BELOW CLIMO.

THE CWFA LOOKS TO BE WITHIN THE COOL CYCLONIC FLOW CLOSE TO THE
PERIPHERY OF THE EASTERN CONUS L/WV TROUGH ON TUESDAY WITH MODERATELY
STRONG SFC RIDGING BUILDING DOWN THE EASTERN SLOPES WEDNESDAY INTO
THURSDAY. WITHIN THIS DRY AND COOL PATTERN...TEMPERATURES SHOULD
AVERAGE 5 TO 8 DEG F BELOW CLIMO EACH DAY.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AT KCLT...CIGS HAVE FINALLY LIFTED...BUT SCT TO BKN LOW VFR WILL
CONTINUE THRU THE AFTERNOON. EXPECT BKN TO OVC LOW VFR TO DEVELOP
THIS EVENING WITH CONTINUED LOW LEVEL MOISTURE AND DEVELOPING SELY
FLOW. CIGS SHUD DETERIORATE TO MVFR OVERNIGHT AND IFR TOWARD
MORNING. VSBY SHUD BOTTOM OUT AT MVFR. HOWEVER...CANNOT RULE OUT
LIFR CIGS AND IFR VSBY AROUND DAYBREAK. SHUD AGAIN BE A SLOW
INCREASE TO MVFR CIGS/VFR VSBY TOWARD MID MORNING...THEN LOW VFR BY
EARLY AFTERNOON. LIGHT WIND THIS AFTERNOON BECOMES LIGHT ESE FOR
LATE AFTERNOON INTO EARLY EVENING. WINDS RETURN TO ENE OVERNIGHT
INTO FRI MORN WITH SOME INCREASE IN SPEED. THERE IS A SMALL CHC OF
CONVECTION THIS AFTERNOON...BUT TOO LOW FOR TAFS. COULD BE SOME
LIGHT SHRA ANYTIME OVERNIGHT OR FRI MORNING...AGAIN CHC LOW.

ELSEWHERE...SIMILAR CONDITIONS AS KCLT...ESPECIALLY KHKY. THE SC
SITES SHUD SEE LOW VFR FOR THE BULK OF THE AFTERNOON BEFORE FALLING
TO IFR OVERNIGHT. KAVL HAS THE BEST CHC OF SEEING LIFR OR VLIFR
TOWARD MORNING. HOWEVER...CHC STILL TO LOW TO INCLUDE FOR NOW.
ANOTHER MORNING WITH A SLOW RISE TO LOW VFR THRU CIG RESTRICTIONS.
THERE IS A SMALL CHC OF CONVECTION THIS AFTERNOON...BUT TOO LOW FOR
TAFS. COULD BE SOME LIGHT SHRA ANYTIME OVERNIGHT OR FRI MORNING...
AGAIN CHC LOW. WINDS WILL BE VARIABLE THIS AFTERNOON AND EVENING...
LIGHT NE TO SE. HOWEVER...STRONGER NELY WINDS DEVELOP OVERNIGHT AND
CONTINUE THRU FRI MORN. KAVL WILL SEE LIGHT SLY WIND DEVELOP FRI.

OUTLOOK...THE POTENTIAL FOR LATE NIGHT/MORNING FOG/STRATUS WILL
PERSIST INTO THE EARLY PART OF THE WEEKEND...ESPECIALLY IN THE MTN
VALLEYS. CONDITIONS MAY FINALLY DRY OUT FOR THE LATTER PART OF THE
WEEKEND. A COLD FRONT MAY BRING INCREASING CHANCES FOR SHOWERS/TSTMS
EARLY NEXT WEEK.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-17Z
KCLT       HIGH  94%     HIGH 100%     MED   66%     LOW   58%
KGSP       HIGH 100%     HIGH 100%     HIGH  81%     MED   66%
KAVL       HIGH 100%     MED   78%     MED   61%     HIGH  83%
KHKY       HIGH  98%     MED   78%     LOW   53%     MED   66%
KGMU       HIGH 100%     HIGH 100%     MED   79%     MED   75%
KAND       HIGH 100%     HIGH 100%     MED   66%     LOW   50%

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...JDL
NEAR TERM...JDL/RWH
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...RWH






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