Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 281755
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
155 PM EDT THU MAY 28 2015

.SYNOPSIS...
BERMUDA HIGH PRESSURE WILL PERSIST ACROSS THE REGION THROUGH THE
WEEKEND AND INTO EARLY NEXT WEEK. DEEPER MOISTURE WILL GRADUALLY
POOL ALONG THE SOUTHERN APPALACHIANS IN THE SOUTHERLY FLOW BETWEEN
LOW PRESSURE APPROACHING THE MID MISSISSIPPI VALLEY FROM THE WEST
AND THE OFFSHORE BERMUDA HIGH TO THE EAST. A COLD FRONT WILL PUSH
SOUTHWARD INTO THE REGION AROUND MID WEEK AND THEN LIKELY STALL
NEARBY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 145 PM...CONVECTION IS FIRING ACROSS THE SOUTHERN APPALACHIANS
AND UPPER SAVANNAH RIVER VALLEY THIS AFTERNOON. CLOUD COVER HAS
SOMEWHAT LIMITED BUOYANCY ACROSS THE HIGH TERRAIN THUS FAR...SO THE
BEST COVERAGE IS CURRENTLY FOUND OVER THE USRV. POPS HAVE BEEN
INCREASED TO A SOLID CHANCE THERE...AND LIKELY MAY BE WARRANTED THIS
AFTERNOON BEFORE ALL IS SAID AND DONE. ELSEWHERE...COVERAGE IS MUCH
MORE ISOLATED. HOWEVER...STEERING CURRENTS AND PROPAGATING OUTFLOWS
SHOULD RESULT IN A GRADUAL INCREASE IN POPS FROM SW TO NE THROUGH
THE AFTERNOON. CELL MOVEMENT WILL REMAIN SLOW UNTIL OUTFLOWS GET A
BIT OF MOMENTUM IN THEIR WAKE. THUS...LOCALLY HEAVY RAINFALL WILL BE
A CONCERN IN THE VERY NEAR TERM....WHILE A BRIEF MICROBURST OR TWO
CANNOT BE RULED OUT.

AS OF 11 AM...SHOWERS LINGER ACROSS SOUTHEAST TENN IN ASSOCIATION
WITH REMNANT/SLOW MOVING MCV. THE PWAT FROM THE 12Z KFFC RAOB
EXCEEDED 1.58 INCHES WITHIN DEEP MOIST PLUME AHEAD OF THIS
FEATURE...CERTAINLY ABOVE CLIMO BUT NOT SUBSTANTIALLY SO. ALTHOUGH
MUCH OF THE AREA WAS CLEAR AS OF LATE MORNING...CLOUDS WERE
INCREASING ACROSS THE NC MTNS...AND THIS WILL LIMIT INSTABILITY
DURING THE AFTERNOON. HOWEVER...COMBINATION OF DIFF HEATING/HIGH
PWATS AND MESOSCALE UVV IN THE VICINITY OF THE MCV SHOULD SUPPORT
NUMEROUS COVERAGE OF SHOWERS AND THUNDERSTORMS ACROSS THE MTNS THIS
AFTERNOON. WIND PROFILES ARE VERIFYING A BIT STRONGER THAN WHAT WAS
SUGGESTED BY YESTERDAY/S NUMERICAL GUIDANCE...AND INDEED THIS
AFTERNOON/S FORECAST SOUNDINGS SUPPORT STORM MOTIONS OF AROUND 10
KTS. THEREFORE...LOCALLY EXCESSIVE RAINFALL ISSUES SHOULD BE
CONFINED TO ANY AREAS THAT SEE TRAINING CELLS...WHICH IS CERTAINLY
NOT OUT OF THE QUESTION. POPS TAPER OFF SOUTHEAST OF THE MTNS...WITH
40-50 PERCENT FAVORED OVER THE FOOTHILLS AND THE UPPER SAVANNAH
RIVER VALLEY (NEARER THE MOISTURE PLUME)...TAPERING TO 30 PERCENT
ALONG THE I-77 CORRIDOR. WITH CAPE ALREADY EXCEEDING 1000 J/KG THIS
MORNING OUTSIDE THE MTNS...A FEW STRONG TO SEVERE STORMS WILL BE
POSSIBLE...ESP ACROSS THE EASTERN HALF OF THE AREA...WHERE DRIER AIR
ALOFT AND WARMER TEMPS/LOWER B.L. RH SHOULD RESULT IN REASONABLY
HIGH DCAPE.

AS OF 650 AM...PATCHY DENSE FOG ACROSS THE AREA SHUD BURN OFF EARLY
THIS MORNING. SPS ISSUED TO ADDRESS THIS. SHRA JUST WEST OF THE CWFA
MAY MOVE INTO THE WRN COUNTIES THIS MORNING...BUT ONLY VERY LIGHT
RAIN EXPECTED. THERE IS A SWIRL SEEN IN THIS ACTIVITY WHICH WILL
MOVE INTO THE MTNS TODAY. HIGHER POP ALREADY IN PLACE THERE.
OTHERWISE...GOING FCST ON TRACK WITH ONLY UPDATES MAINLY FOR CURRENT
CONDITIONS.

AS OF 310 AM...CONVECTION OVER CENTRAL GA DIMINISHING AS IT SLOWLY
MOVES NE TOWARD THE SAVANNAH RIVER. HOWEVER...A FEW CELLS CONTINUE
TO REGENERATE ALONG THE LEADING EDGE OF THE WEAKENING COLD POOL. IF
THE CELLS CAN MAINTAIN THEMSELVES...THIS ACTIVITY WOULD MOVE INTO
OUR NE GA...AND POSSIBLY...WRN UPSTATE COUNTIES. IF THIS DOES
HAPPEN...THE CELLS SHOULD BE SHORT LIVED AND DISSIPATE BEFORE
DAYBREAK. OTHERWISE...EXPECT PATCHY FOG AND/OR LOW CLOUDS THIS
MORNING. SHOULD BE MORE DIURNAL CONVECTION TODAY AS PW VALUES RISE
ABOVE NORMAL AND A WEAK SHORT WAVE AND UPPER DIVERGENCE MOVE INTO
THE AREA. MODERATE INSTABILITY DEVELOPS BUT SHEAR IS WEAK. DCAPE
VALUES BETWEEN 500 J/KG AND 750 J/KG DEVELOP ALONG WITH DECENT SFC
DELTA THETA-E VALUES. HOWEVER...THERE WILL BE QUITE A BIT OF
CONVECTIVE DEBRIS CLOUDS ACROSS THE AREA TODAY WHICH COULD LIMIT
HEATING. ALL THAT SAID...ISOLATED SVR STORMS ARE POSSIBLE WITH
DAMAGING WINDS THE MAIN THREAT. THE CONVECTION SHOULD BE DIURNAL IN
NATURE...BUT COULD LINGER WELL INTO THE EVENING...AND POSSIBLY EARLY
OVERNIGHT...BEFORE DISSIPATING. HIGHS WILL BE NEAR TO 5 DEGREES
ABOVE NORMAL WITH LOWS AROUND 5 TO 10 DEGREES ABOVE NORMAL.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 230 AM THURSDAY...AN UPPER RIDGE WILL PERSIST ALONG THE EAST
COAST...WHILE A WEAK TROF WILL SLOWLY CROSS THE CENTRAL-NORTHERN
PLAINS FRIDAY THRU SATURDAY. A SFC RIDGE AXIS WILL LINGER ACROSS THE
AREA...EXTENDING WESTWARD FROM THE NORTH ATLANTIC TO THE FL
PANHANDLE. THE MODELS AGREE THAT THIS RIDGE WILL HELP KEEP THINGS
MORE CAPPED...ESP ON SATURDAY. HOWEVER...THERE WILL STILL BE
SCATTERED MTN CONVECTION BOTH DAYS...WITH ISOLD CONVECTION POSSIBLE
ACRS THE PIEDMONT. SATURDAY WILL PROBABLY HAVE THE LEAST COVERAGE
PER MODEL CONSENSUS. TEMPS WILL BE A COUPLE CATEGORIES ABOVE NORMAL
FOR DAYTIME HIGHS...AND A FEW CATEGORIES ABOVE NORMAL FOR OVERNIGHT
LOWS...AS AIR MASS REMAINS HUMID. FCST SNDGS SHOW MODEST INSTBY ON
FRIDAY...WITH WEAK SHEAR. SO EXPECT SLOW-MOVING STORMS PRODUCING
HEAVY RAINFALL AS THE MAIN THREAT...WHILE A SEVERE WIND THREAT WILL
BE LOW. SATURDAY HAS EVEN LESS INSTBY...SO OVERALL HEAVY RAIN AND
SEVERE THREATS WILL BE VERY ISOLATED.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 245 AM THURSDAY...THE LATEST MEDIUM RANGE GUIDANCE HAS BEEN
TRENDING TOWARD BREAKING OFF THE SOUTHERN END OF THE APPROACHING
SHORTWAVE OVER THE MID MS VALLEY ON SUNDAY...CLOSING OFF A WEAK
CLOSED UPPER LOW INVOF THE MID SOUTH MONDAY THRU WEDNESDAY. THIS
ALLOWS THE EAST COAST RIDGE TO PERSIST THRU EARLY NEXT WEEK. THIS
SLOWS DOWN THE APPROACHING COLD FRONT. THE 00Z GFS AND ECMWF NOW
KEEP THE FRONT NORTH OF THE AREA THRU THE WEEKEND...THEN SLOWLY BACK
DOOR THE FRONT EARLY NEXT WEEK...AS HIGH PRES SETTLES IN ACRS THE
NORTHEAST STATES. IN ANY CASE...THERE BE A RETURN TO ABOVE CLIMO
POPS EACH DAY NEXT WEEK. TEMPS WILL BE ABOUT 5-8 DEG ABOVE NORMAL ON
SUNDAY...THEN BACK TO JUST A CATEGORY ABOVE NORMAL FOR MONDAY AND
TUESDAY...WITH INCREASED COVERAGE OF AFTN/EVE CONVECTION. OVERNIGHT
LOWS ARE NEARLY THE SAME EACH NIGHT WITHIN THE HUMID AIR MASS. THE
ATMOSPHERE WILL CONTINUE TO BE WEAKLY SHEARED ATOP THE CWFA...SO
EXPECT LOCALLY HEAVY RAIN TO BE THE MAIN THREAT AGAIN NEXT
WEEK...WITH A MARGINAL/ISOLATED SEVERE WIND/HAIL THREAT EACH DAY.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AT KCLT...MAIN CONCERN THIS PERIOD IS CONVECTIVE POTENTIAL DURING
THE REMAINDER OF THE PM. ALTHOUGH THE BEST COVERAGE DURING THIS TIME
WILL BE ACROSS THE FAR WESTERN CAROLINAS...ONE LONE CELL HAS DEVELOPED
RECENTLY JUST SOUTH OF THE TERMINAL...THUS THE TEMPO FOR TSRA HAS
BEEN MOVED TO 18-22Z. OTHERWISE...WINDS WILL GENERALLY REMAIN
SOUTHERLY...WITH SOME GUSTS POSSIBLE NEAR SHOWERS AND STORMS.
SUFFICIENT MOISTURE WILL REMAIN IN PLACE THROUGH THE PERIOD SUCH
THAT THERE WILL BE A POTENTIAL FOR CIG AND/OR VISBY RESTRICTIONS
LATE TONIGHT/EARLY FRI. HOWEVER...CONFIDENCE IS QUITE LOW ATTM...AND
IN FACT...LOW CIGS AND/OR FOG MAY BE CONFINED TO AREAS CLOSER TO THE
HIGH TERRAIN.

ELSEWHERE...SCATTERED CELLS ARE DEVELOPING ALONG AN AXIS FROM
ROUGHLY KAND TO KAVL. TEMPOS FOR TSRA WILL PERSIST AT THESE
TERMINALS THROUGH 22Z. STEERING WINDS AND PROPAGATING OUTFLOW
BOUNDARY SHOULD TAKE THIS ACTIVITY OFF TO THE E/NE RATHER GRADUALLY.
THUS...TEMPOS HAVE ALSO BEEN INTRODUCED AT KGSP/KGMU AFTER 19Z. VCTS
WILL BE RETAINED AT KHKY FOR NOW...BUT WILL HAVE TO WATCH THAT SITE
CLOSELY FOR A POTENTIAL TEMPO AS WELL. SUFFICIENT MOISTURE WILL
REMAIN IN PLACE THROUGH THE PERIOD SUCH THAT THERE WILL BE A
POTENTIAL FOR CIG AND/OR VISBY RESTRICTIONS LATE TONIGHT/EARLY FRI.
VISBY RESTRICTIONS WILL BE CARRIED AT MOST TERMINALS DURING THIS
TIME...WITH LOW CIGS LIMITED TO KAVL. LOW CIGS CAN BY NO MEANS BE
RULED OUT ELSEWHERE...BUT CONFIDENCE IS QUITE LOW ATTM.

OUTLOOK...MOIST SW FLOW WILL CONTINUE TO AFFECT THE TERMINAL
FORECAST AREA THROUGH THE UPCOMING WEEKEND...AS A COLD FRONT LAYS
OVER TO THE NORTH OF THE AREA. EXPECT POCKETS OF MORNING FOG AND/OR
STRATUS MOST DAYS...WITH CONTINUED CHANCES OF AFTN/EVENING SHRA/TSRA
EACH DAY.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH  97%     HIGH  97%
KGSP       HIGH 100%     HIGH 100%     HIGH  97%     HIGH  94%
KAVL       HIGH  99%     MED   78%     HIGH  94%     MED   76%
KHKY       HIGH  92%     HIGH  85%     HIGH 100%     HIGH  94%
KGMU       HIGH 100%     HIGH 100%     HIGH  90%     HIGH  83%
KAND       HIGH 100%     HIGH 100%     HIGH  94%     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...ARK
NEAR TERM...JDL/RWH
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...RWH



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