Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 190515
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
115 AM EDT TUE AUG 19 2014

.SYNOPSIS...
A WEAK LOW PRESSURE SYSTEM WILL LINGER OVER THE AREA TONIGHT AND
THEN SLOWLY MOVE OFF THE COAST ON TUESDAY. A BROAD UPPER LEVEL RIDGE
OF HIGH PRESSURE WILL THEN BUILD ACROSS THE MISSISSIPPI RIVER VALLEY
OVER THE NEXT FEW DAYS AND LINGER FOR THE REST OF THE WORK
WEEK...RESULTING IN ABOVE NORMAL TEMPERATURES AND DRIER WEATHER.

&&

.NEAR TERM /THROUGH TODAY/...
0515 UTC UPDATE...POPS WERE REDUCED EARLY ON PER RADAR TRENDS. WINDS
WERE UPDATED WITH THE LATEST NAM AND ADJMET. AREAS OF FOG WERE
ADJUSTED BASED ON FORECAST DEW POINT DEPRESSIONS BY DAWN. SKY COVER
WAS UPDATED FROM SATELLITE IMAGERY.

AS OF 1030 PM...AS EXPECTED...THE LOSS OF INSTABILITY WITH SUNSET
HAS STARVED THE CONVECTION COMING OUT OF TN AND N GA...WITH ONLY A
WEAKENING STORM DRIFTING INTO THE LAKELANDS AS OF 02Z. WILL ADJUST
POP DOWNWARD BASED ON RADAR TRENDS. OUR ATTENTION THEN TURNS TO THE
OBVIOUS MCV FEATURE OVER NRN AL. GIVEN ITS COHERENT NATURE...IT
SEEMS LIKELY THAT IT WILL SURVIVE IN SOME FASHION AND MOVE INTO THE
WESTERN ZONES AFTER 06Z...SO THE CHC POP WILL BE RETAINED THERE.
TEMPS STILL LOOK GOOD.

REMAINDER OF PREVIOUS DISCUSSION...

A LULL IS EXPECTED IN ANY CONVECTIVE ACTIVITY LATER THIS EVENING.
HOWEVER...CHANCES WILL INCREASE AGAIN DURING THE EARLY MORNING AS
A SHORT WAVE APPROACHES FROM GA/AL. DESPITE THE RATHER POTENT
APPEARANCE OF THIS WAVE...THE MODELS ARE NOT EXACTLY ROBUST WITH
THEIR QPF RESPONSE IN OUR AREA. CERTAINLY THE TIMING REFLECTS AN
ABSENCE OF ROBUST INSTABILITY WITH WHICH TO INTERACT. MEANWHILE...
THERE APPEARS TO BE A CONSENSUS THAT THE BETTER LOW LEVEL SHEAR WILL
PASS SOUTH OF OUR AREA. THUS THE POTENTIAL FOR ORGANIZED CONVECTION
APPEARS TO BE HIGHER SOUTH OF OUR AREA. NEVERTHELESS...POPS WILL
INCREASE TO 30-50 PERCENT ACROSS THE WESTERN HALF OF THE AREA
BETWEEN 06Z AND 12Z.

BY TUE AFTERNOON...THE WAVE IS EXPECTED TO BE PUSHING EAST OF THE
AREA...LIKELY PLACING THE AREA WITHIN WEAK SYNOPTIC SCALE SUBSIDENCE
THAT COULD LIMIT COVERAGE OF CONVECTION DURING THE AFTERNOON.
OVERALL...THERE IS QUITE A BIT OF UNCERTAINTY REGARDING THE
EVOLUTION OF CONVECTION TUE MORNING...SO WE WILL ESSENTIALLY FEATURE
TOKEN 30/40 POPS ACROSS THE AREA DURING THE AFTERNOON.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
AS OF 230 PM MONDAY...AN ENDLESS PARADE OF S/W`S WILL BE IMPACTING
OUR FORECAST AREA DURING THIS CYCLE. THE FIRST WILL BE EXITING OUR
REGION TUESDAY. I LEFT A SLIGHT CHANCE IN THE FAR EASTERN FA OF NC
DURING THE EARLY EVENING... AND ALSO ACROSS THE WEST FACING SLOPES
OF THE NC MOUNTAINS (ALSO IN THE EVENING )...WHERE WEAK UPSLOPE
PERSISTS.

MODELS DIFFER ON TIMING AND DEGREE OF NWLY FLOW DEVELOPING OVER THE
CAROLINAS AND NE GA WEDNESDAY AND THURSDAY...AS AN UPPER LEVEL RIDGE
BUILDS FROM THE WESTERN GULF OF MEXICO INTO THE NRN PLAINS. THIS
EVOLUTION...COMBINED WITH A PERSISTENT CUTOFF UPPER LOW MEANDERING
OVER THE GREAT LAKES...WILL SET UP A NWLY FLOW PATTERN ACROSS THE
ERN CONUS...AND ALMOST A RING OF FIRE (ROF) LOOK. ALTHOUGH OUR SHORT
TERM SUITE OF GUIDE VARY IN DETAIL...THE OVERALL PHILOSOPHY / OR BIG
PICTURE / SEEM TO COINCIDE. AS A RESULT THE STAGE WILL BE SET FOR
CLUSTERS OF SHOWERS/TSTMS TO RIDE THE NWLY FLOW DOWN INTO/TOWARD OUR
REGION. IT APPEARS THE FIRST SUCH WOULD BE ASSOCIATED WITH THE
ENERGY IN THE WESTERN OHIO VALLEY TUESDAY...REACHING OUR NC
MOUNTAINS IN THE WEE HOURS WEDNESDAY. CORFIDI VECTORS SUGGEST THAT
ACTION WOULD SPREAD E-SE...POTENTIALLY REACHING PARTS OF NE GA AND
UPSTATE OF SC. STEEP LOW LEVEL LAPSE RATES AND FAT CAPE (ESPECIALLY
WHERE LACK OF DEBRIS CLOUDS MOVE) COULD PROVE FOR AN INTERESTING
WEATHER DAY.

YET ANOTHER S/W WILL FOLLOW ON THURSDAY. FLOW ALOFT SUBTLY SHIFTS
MORE NWLY...THEREFORE I HAVE BROUGHT POPS A BIT DEEPER (SOUTHWARD)
IN OUR CWA IN THE AFTERNOON. ALTHOUGH POPS WITH EACH OF THE
AFOREMENTIONED EPISODES REMAIN ON THE LOW SIDE...THE CONDITIONAL
PROBABILITIES REMAIN ELEVATED. WE ARE NEAR GUIDE POPS OVERALL...OR
SLIGHTLY HIGHER ON OUR SOUTHERN FORECAST FRINGES. ONCE WE GET A
BETTER HANDLE IF/WHERE THESE CLUSTERS WILL FOCUS...POPS CAN BE
ADJUSTED ACCORDINGLY.

ON THE TEMPERATURE END OF THE SPECTRUM...POTENTIAL DEBRIS CLOUDS AND
SHOWERS AND THUNDERSTORMS WOULD SUGGEST LOWERING GUIDE. HOWEVER LOW
LEVEL THERMAL PROFILE IS SOLIDLY ON THE RISE AND WOULD SUGGEST
TEMPERATURE VALUES REACHING NEAR MAXES...WITH DIFFERENTIAL HEATING
EVEN OF WIDESPREAD CONVECTION DEVELOP.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 210 PM EDT MONDAY...THE MEDIUM RANGE PICKS UP AT 00Z ON FRIDAY
WITH THE UPPER RIDGE AMPLIFYING OVER THE MISS RIVER VALLEY WHILE
ANOTHER BROAD UPPER TROF DIGS DOWN JUST OFF THE ATLANTIC SEABOARD.
FOR THE REMAINDER OF THE PERIOD...THE RIDGE AXIS REMAINS LARGELY IN
PLACE TO OUR WEST WHILE THE UPPER TROF BECOMES NEARLY STATIONARY AND
MORPHS INTO A CLOSED H5 LOW OVER THE WEEKEND. THE LATEST LONG RANGE
MODEL GUIDANCE SUGGESTS THAT WE WILL PROBABLY SEE SOME FLATTENING OF
THE UPPER RIDGE BY THE END OF THE PERIOD...BUT IT WONT BE TOO
SIGNIFICANT.

AT THE SFC...OUR AREA IS EXPECTED TO REMAIN UNDER A WARM AND MOIST
AIR MASS DURING THE FIRST PART OF THE PERIOD WITH WEAK HIGH PRESSURE
IN PLACE AND A SERIES OF WEAK MESO LOWS THAT TRY TO SPIN UP TO OUR
NORTH AND EAST. AS WE GO INTO THE WEEKEND...THE LONG RANGE MODELS
ARE LEANING TOWARDS A MORE ROBUST WEDGE DEVELOPING ON SAT AND
ESPECIALLY ON SUN. THIS PATTERN DEVELOPS FROM THE COMBINATION OF A
STRONG HIGH CENTERED OVER NOVA SCOTIA AND A LOW SPINNING UP AS IT
MOVES OFF THE NC COAST. THIS PROVIDES FOR STRONGER NELY LOW LVL FLOW
OVER THE FCST REGION AS THE HIGH IS SLOW TO PROGRESS EASTWARD AND
THE LOW REMAINS OFF THE NORTHEAST COAST THRU NEW DAY 7. THE WEDGE PATTERN
APPEARS TO BREAK DOWN BY THE END OF THE PERIOD EARLY NEXT
WEEK...HOWEVER MANY TIMES THESE FEATURES LINGER LONGER THAN THE
MODELS DEPICT. AS FOR THE SENSIBLE WX...NO MAJOR CHANGES WERE MADE
TO THE POP FCST WITH CHANCE COVERAGE INCREASED ON BOTH SAT AND SUN
AND ONLY SLIGHT CHANCE FOR MON AS THE DEEPER MOISTURE SHIFTS
EASTWARD AND THE WEDGE WEAKENS. TEMPS START OUT ABOUT A CATEGORY
ABOVE NORMAL ON FRI AND STEADILY COOL THRU EARLY NEXT WEEK WITH
VALUES ENDING RIGHT AROUND CLIMO IF NOT JUST BELOW.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AT KCLT...THE DEW POINT DEPRESSION IS RATHER LARGE AT THIS TIME...
AND A MODEL BLEND YIELDS ONLY LOW VFR VSBY BY DAYBREAK...WHICH MAY
BE TOO PESSIMISTIC. LOW VFR CLOUDS ARE NOT EXPECTED TO BECOME
PREVALENT UNTIL MORNING...AS A MID LEVEL SYSTEM MOVES ACROSS SC. THE
LOW VFR CIG WILL THEN ERODE AFTER SUNSET AS THE MID LEVEL SYSTEM
DEPARTS. CONVECTIVE CHANCES LOOK BEST AT PEAK HEATING IN THE
AFTERNOON. LIGHT SW WINDS ARE EXPECTED TO VEER NW BY MID DAY.

ELSEWHERE...DEW POINT DEPRESSION ARE NOT VERY SUPPORTIVE OF FOG AT
KGSP AND KGMU...BUT GUIDANCE DOES TAKE KHKY DOWN TO MVFR VSBY BY
DAYBREAK. GUIDANCE SUGGESTED IFR VSBY AT KAVL BY DAWN...BUT FOR SO
BRIEF A PERIOD THAT ONLY MVFR WILL BE CARRIED THERE. KAND IS
EXPECTED TO HAVE MVFR FOG AS WELL. VFR RETURNS BY MID MORNING. LOW
VFR CIGS WILL DEVELOP IN THE MOUNTAINS AS A MID LEVEL SYSTEM
APPROACHES FROM THE WEST TOWARD DAWN...WITH GUIDANCE SUPPORTING
BRIEF MVFR AT KAVL AROUND DAYBREAK. THE LOW VFR CIGS WILL SET UP IN
THE FOOTHILLS AFTER DAYBREAK. CONVECTIVE CHANCES WILL BE BEST WITH
AFTERNOON HEATING...BUT SOME PRECIPITATION MAY CROSS THE SAVANNAH
RIVER AND AFFECT SC SITES AROUND DAYBREAK. LOW VFR CIGS WILL ERODE
THIS EVENING AS THE MID LEVEL SYSTEM DEPARTS.SW WINDS WILL VEER TO W
IN THE FOOTHILLS THIS AFTERNOON. WINDS WILL REMAIN CHANNELED UP
VALLEY FORM THE NW AT KAVL.

OUTLOOK...SCT AFTERNOON CONVECTION AND PATCHY EARLY MORNING FOG WILL
REMAIN IN THE FORECAST THROUGH THE WEEK. THERE WILL ALSO BE
INCREASING CHANCES FOR ORGANIZED CONVECTION APPROACHING THE AREA
FROM THE NW DURING THE LATE NIGHT/EARLY MORNING HOURS.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-05Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH  87%     HIGH 100%     HIGH 100%
KAVL       HIGH  87%     HIGH  88%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH  93%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH  93%     HIGH  99%     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...JAT/JDL/PM
SHORT TERM...TS
LONG TERM...JPT
AVIATION...JAT





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