Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 172356
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
756 PM EDT SUN AUG 17 2014

.SYNOPSIS...
WEAK HIGH PRESSURE ATOP THE REGION THIS WEEKEND WILL GIVE WAY TO A
GRADUAL INFLUX OF MOISTURE ON MONDAY AND TUESDAY WITH IMPROVING
SOUTHWEST FLOW. A SERIES OF LOW PRESSURE SYSTEMS PASSING BY TO THE
NORTH WILL INCREASE THE CHANCES OF SHOWERS AND THUNDERSTORMS THROUGH
MIDWEEK...ESPECIALLY OVER THE MOUNTAINS.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 730 PM...AS EXPECTED...PRECIP MOVING IN FROM SE TN AND N GA
CONTINUES TO WEAKEN AS IT FIGHTS ITS WAY INTO A LESS FAVORABLE
ENVIRONMENT. HAVE EXTENDED A CHANCE POP ACROSS THE LAKELANDS AND
OVER PARTS OF THE NRN FOOTHILLS OF NC BASED ON RADAR TRENDS. THINK
THE LIKELY POP OVER THE SRN MOUNTAINS LOOKS GOOD WITH A LOWERING
TREND INTO THE LATE EVE. TEMPS ARE IN GOOD SHAPE.

REMAINDER OF PREVIOUS DISCUSSION...

MODELS INDICATE THIS INITIAL MCS WILL LIKELY DECAY SOMEWHAT WITH
HEATING LOSS AS IT ENTERS THE HIGH TERRAIN OF WESTERN NC AND
NORTHEAST GA BY EARLY EVENING.  HOWEVER...PROFILES ACROSS THIS
REGION WILL REMAIN SUPPORTIVE OF MILDLY STRONG UPDRAFTS THEREFORE A
FEW THUNDERSTORMS CANNOT BE RULED OUT ACROSS THE MOUNTAINS THROUGH
MID/LATE EVENING.  MODELS SEEM TO DIFFER SOMEWHAT AT THIS POINT WITH
THE 12Z HIRES WRF PRODUCTS INDICATING A SECONDARY MCS DEVELOPING AND
TRAILING THE INITIAL LINE BY ABOUT 4-5 HOURS AND ENTERING THE
MOUNTAIN ZONES JUST AFTER MIDNIGHT.  THAT SAID...THE HRRR AND LOWER
RES 12Z NAM INDICATE A LULL AS MENTIONED ABOVE WITH INITIAL MCS
DECAY...WHICH WAS THE PREFERRED SOLUTION IN THE FORECAST.

BY DAYBREAK EXPECTING COVERAGE OF SHOWERS AND PERHAPS A THUNDERSTORM
OR TWO TO BE INCREASING ACROSS MOST OF WESTERN NC...AND EVENTUALLY
SPREADING SOUTHEAST INTO THE NC/SC PIEDMONTS BY LATE MORNING INTO
EARLY AFTERNOON.  PROFILES LOOK FAIRLY MOIST WHICH WILL INHIBIT
DIURNAL HEATING SOMEWHAT HOWEVER THERE WILL BE NEARLY 1000J/KG
SBCAPE PRESENT BY LATE MORNING.  THUS CANNOT RULE OUT A STRONG TO
PERHAPS ISOLATED SEVERE THUNDERSTORM BEFORE THE PRIMARY UPPER
FORCING MECHANISM MOVES OUT LEAVING ONLY THERMODYNAMIC EFFECTS IN
PLAY.  ONE ADDITIONAL NOTE...AS MENTIONED ABOVE PROFILES WILL BE
ABUNDANTLY MOIST THEREFORE ANY THUNDERSTORMS COULD PRODUCE
SUBSTANTIAL RAIN RATES LEADING TO MINOR FLASH FLOODING.  FORTUNATELY
DUE TO 30-40KTS OF WESTERLY H5 FLOW AND CONTINUED SOUTHWESTERLY FLOW
BENEATH...IT DOES NOT LOOK AS IF ANY CELLS WILL ANCHOR.  CONDITIONS
WILL SLOWLY IMPROVE TOWARDS THE LATE AFTERNOON ACROSS THE SOUTHWEST
WITH THE NORTHEASTERN ZONES TO FOLLOW AS THE WAVE DEPARTS.  AS FOR
THE FORECAST...CHANCE POPS ARE FEATURED ACROSS THE MOUNTAINS WITH
ONLY SLIGHT CHANCE POPS ACROSS THE FOOTHILLS FOR THIS AFTERNOON AND
EVENING.  POPS ON MONDAY WILL FEATURE LIKELY LEVELS ACROSS MUCH OF
WESTERN NC WITH SOLID CHANCE LEVEL POPS ELSEHWERE. TEMPERATURES WILL
BE COOLER ON MONDAY AS PARTLY/MOSTLY CLOUDY SKIES PREVAIL YIELDING
BELOW NORMAL TEMPERATURES.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 255 PM SUNDAY...NEARLY ZONAL FLOW REMAINS ACROSS THE AREA THRU
THE PERIOD AS AN UPPER LOW MOVES TO THE GREAT LAKES AND A RIDGE
BUILDS OVER THE LOWER MS RIVER VALLEY AND GULF COAST. A SHORT WAVE
TO THE SOUTH MOVES INTO THE AREA TUE...ANOTHER SHORT WAVE MOVES
ACROSS THE NORTH TUE NITE WITH ANOTHER WEAK WAVE ACROSS THE AREA
WED. AT THE SFC...A QUASI STATIONARY FRONT REMAINS TO OUR NORTH WITH
A LEE TROF NEAR THE FALL LINE. THERE WILL BE WAVES OF MOISTURE
MOVING INTO THE AREA WITH THE WAVES...ALMOST MCS LIKE. HOWEVER...
THERE IS QUITE A BIT OF SPREAD IN THE GUIDANCE SOLUTIONS REGARDING
CONVECTIVE COVERAGE. IN ADDITION...THERE IS LITTLE IN THE WAY OF LOW
LEVEL SLY FLOW WITH LOW LEVEL RIDGING KEEPING THE WINDS MORE WLY.
ALSO...LFC LEVELS REMAIN HIGH ACROSS THE SOUTH...BUT DO LOWER ACROSS
THE MTNS AND NRN TIER WHERE LOW LEVEL MOISTURE INCREASES THE MOST.
THERE IS QUITE A BIT OF ELEVATED INSTABILITY HOWEVER...SO ANY
FORCING THAT CAN LIFT THE PARCELS TO THAT LEVEL WILL ALLOW CONVECTION
TO BE REALIZED. THEREFORE...HAVE CONTINUED THE PREV TREND OF HIGHEST
POP MTNS AND NRN TIER THRU THE PERIOD...WITH A DIURNAL TREND. THAT
SAID...KEEP POP ACROSS THE MTNS OVERNIGHT TO ACCOUNT FOR ANY MCS
ACTIVITY THAT DOES MAKE IT THIS FAR EAST. LOWS WILL REMAIN NEARLY
STEADY A LITTLE ABOVE NORMAL. HIGHS WILL BE NEAR TO SLIGHTLY ABOVE
NORMAL TUE...THEN WARM A COUPLE OF DEGREES WED.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 2 PM EDT SUNDAY...THE MEDIUM RANGE PICKS UP AT 00Z ON THURSDAY
WITH RELATIVELY FLAT UPPER RIDGING OVER THE SE CONUS AND A HEALTHY
LOOKING UPPER SHORTWAVE CROSSING THE SOUTHERN GREAT LAKES TO OUR
NORTH. OVER THE NEXT COUPLE OF DAYS...THE LONG RANGE MODELS HAVE THE
UPPER RIDGE RETROGRADING BACK TOWARDS THE WEST WHILE THE ABOVE
SHORTWAVE BECOME ABSORBED BACK INTO MEAN UPPER FLOW AND A BROADER
UPPER TROF DEVELOPS JUST OFF THE NEW ENGLAND COAST. FOR THE
REMAINDER OF THE PERIOD...THE RIDGE AXIS REMAINS IN PLACE TO OUR
WEST WHILE THE UPPER TROF BECOMES NEARLY STATIONARY AND MORPHS INTO
A CLOSED H5 LOW BY DAY 7.

AT THE SFC...OUR AREA IS EXPECTED TO REMAIN UNDER A WARM AND MOIST
AIR MASS THRU 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 WOULD BE EXPECTED...MODEL PLACEMENT AND TIMING OF THESE LOWS IS
SPORADIC BETWEEN RUNS WITH THE DEEPER LYR MOISTURE ASSOCIATED WITH
THE NEAR SFC FEATURES GENERALLY CONFINED TO OUR NORTH AND EAST. THE
DEEPER MOISTURE APPEARS TO SPREAD MORE TO THE WEST OVER THE WEEKEND
SO SAT AND SUN  SHOULD BE OUR BEST SHOT AT WIDESPREAD DIURNAL
CONVECTION. OTHERWISE...POPS FOLLOW A TYPICAL LATE SUMMERTIME
DIURNAL SLIGHT CHANCE TO CHANCE. TEMPS WILL START OUT ABOUT A
CATEGORY ABOVE NORMAL ON THURS AND STEADILY COOL THRU DAY 7 WITH
VALUES ENDING RIGHT AROUND CLIMO.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL THROUGH TONIGHT AND MONDAY
MORNING. CONVECTION SEEN ON THE KGSP RADAR STANDS ONLY A SMALL
CHANCE OF SURVIVING LONG ENOUGH AS THE BOUNDARY LAYER COOLS AND
STABILIZES AFTER SUNSET. INSTEAD...EXPECT HIGH BASED STRATOCU AND
ALTOCU TO FORM A VFR CEILING. A LIGHT SW TO S WIND WILL PREVAIL. ON
MONDAY...THE MODELS ARE FAIRLY CONSISTENT WITH MOISTURE CONVERGENCE
OVER THE PIEDMONT BEGINNING AROUND 16Z THROUGH THE END OF THE
PERIOD...AND THE MODELS ALSO DEVELOP SOME PRECIP DURING THAT TIME
FRAME. AN APPROACHING UPPER WAVE WILL HELP TO INCREASE MOISTURE AND
BRING A STRONGER SW WIND. THIS SHOULD PROVIDE FOR A VFR CEILING IN
THE 040-060 RANGE IN THE MORNING AND EARLY AFTERNOON. THE PRECIP
CHANCE WILL BE HANDLED WITH A PROB30 FOR THE TIME BEING IN THE 16Z
TO 22Z TIME FRAME...BUT THE CHANCE WILL PERSIST INTO MONDAY EVENING.

ELSEWHERE...THE MAIN CONCERN IS CONVECTIVE PRECIP SEEN ON THE KGSP
RADAR...BUT A DIMINISHING TREND IS EXPECTED AS THE SHOWERS WORK
FARTHER E OVER THE CAROLINAS. HAVE LIMITED THE TAFS TO ONLY A VCSH
AND WILL AMEND IF MORE COHERENT RADAR ECHOES APPROACH A TAF SITE.
FOR THE MOST PART...VFR CONDITIONS WILL PREVAIL AT THE MAJORITY OF
THE FORECAST SITES UNTIL THE EARLY MORNING HOURS. KAVL WILL HAVE A
HIGHER CHANCE OF SEEING FOG DEVELOPING IN THE VALLEY AROUND DAYBREAK
SO AN MVFR VSBY WAS INCLUDED. THE OTHER SITES COULD SEE AN MVFR
CLOUD DECK IN THE EARLY MORNING HOURS AROUND DAYBREAK ACCORDING TO
THE LAMP GUIDANCE...WHICH WAS GENERALLY ACCEPTED. OTHERWISE...
PREVAILING VFR FROM MID MORNING ONWARD. ALL SITES WILL HAVE THE
POSSIBILITY OF THUNDERSTORMS ON MONDAY AFTERNOON...AND THE FCST WAS
HANDLED SIMILAR TO KCLT. WINDS THROUGH THE PERIOD WILL REMAIN
PREDOMINATELY OUT OF THE SOUTHWEST ASIDE FOR AT KAVL WHERE WINDS ARE
CHANNELED FROM THE NORTHWEST.

OUTLOOK...CHANCES FOR PRECIP AND CIG/VSBY RESTRICIONS WILL REMAIN
ELEVATED THROUGH MONDAY NIGHT AS AN UPPER DISTURBANCE SPREADS
CONVECTION ACROSS THE REGION.  UPPER LEVEL RIDGING WILL SET IN BY
MIDWEEK WITH ENOUGH MOISTURE IN THE PROFILE TO SUPPORT DIURNAL
CONVECTION THROUGH WEEKS END LEADING TO AFTERNOON TSRA RESTRICTIONS
AND POSSIBLE EARLY MORNING FOG.

CONFIDENCE TABLE...

            00-06Z        06-12Z        12-18Z        18-24Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH  92%     HIGH  92%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  91%     HIGH 100%
KHKY       HIGH 100%     HIGH  82%     HIGH  91%     HIGH 100%
KGMU       HIGH  92%     HIGH  86%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     MED   74%     MED   73%     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...CDG/PM
SHORT TERM...RWH
LONG TERM...JPT
AVIATION...PM






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