Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 051853
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
253 PM EDT THU MAY 5 2016

.SYNOPSIS...
UNSEASONABLY COOL AIR WILL FILTER IN FROM THE NORTHWEST TODAY IN THE
WAKE OF A COLD FRONT. THE WEATHER WILL REMAIN UNSETTLED AS A DEEP
UPPER LOW CENTER MOVES DOWN ACROSS THE CAROLINAS TODAY AND
TONIGHT...AND THEN MOVES AWAY TO THE NORTHEAST ON FRIDAY. ANOTHER
FRONT IS EXPECTED TO STALL JUST TO OUR NORTH ON SATURDAY AND SUNDAY.
THE FRONT SHOULD LIFT BACK TO THE NORTH ON MONDAY...AS HIGH PRESSURE
OFF THE SOUTHEAST COAST EXPANDS AND WARM SOUTHERLY FLOW RETURNS.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 130 PM...CLOSED CIRCULATION WITHIN UPPER LEVEL LOW PRESSURE IS
NOW CENTERED INVOF THE SMOKY MTNS. THE LOW WILL SHIFT SOUTHEASTWARD
THRU THIS EVENING. A DEEP LAYER OF MODESTLY FAVORABLE LAPSE RATES
IS PRESENT OVER THE AREA...AND WITH DIURNAL HEATING COVERAGE OF
SHOWERS IS INCREASING. AS FAR BACK AS WED AFTN...MOST CONVECTION
ALLOWING MODELS /CAMS/ HAVE FOCUSED ON THE SW HALF OF THE AREA AS
HAVING THE BEST COVERAGE THIS AFTN...WITH A SECONDARY FOCUS OVER
THE I-77 CORRIDOR. THIS APPEARS TO BE WORKING OUT FAIRLY WELL...WITH
THE LULL IN THE NC FOOTHILLS AND VCNTY POSSIBLY DUE TO DOWNSLOPING
NW WINDS. LATEST POP TRENDS WERE BASED ON CONSENSUS OF THE LATEST
CAMS. THOUGH COOL TEMP PROFILES WOULD SUGGEST CLOUDS WILL PRODUCE
ICE EASILY...ONLY A COUPLE OF LIGHTNING STRIKES HAVE BEEN REPORTED
OVER THE PAST COUPLE HRS. AT LEAST ONE STORM HAS PRODUCED GRAUPEL
OR SMALL HAIL...AND IT IS LIKELY THAT THE MORE ROBUST CELLS THIS
AFTN WILL PRODUCE MORE OF THE SAME. WHILE WINDS WILL BE FAIRLY
GUSTY ANYWAY...SUCH STORMS COULD BRING DOWN SOME STILL STRONGER
GUSTS IN LIGHT OF DCAPE VALUES NEARING 600 J/KG OVER PARTS OF THE
AREA PER NAM.

TONIGHT THE LOW WILL MOVE TOWARD THE CAROLINA COAST...AND THE
BEST Q VECTOR CONVERGENCE WILL BE TO OUR EAST. LAPSE RATES WILL
BECOME LESS FAVORABLE...BUT DEEPER MOISTURE ARRIVES FROM THE N
ON THE BACK SIDE OF THE LOW. INTERESTINGLY...FAIRLY WELL-DEFINED
ISENTROPIC LIFT OCCURS IN THE NORTHERLY FLOW THRU THE FIRST HALF
OF THE NIGHT...AND THAT APPEARS TO BE THE MAIN DRIVER FOR THE QPF
PRODUCED BY VARIOUS GUIDANCE. TEMPS WILL AGAIN BE A CATEGORY OR
TWO BELOW NORMAL...AND SOME SNOW IS LIKELY TO MIX IN ONCE AGAIN
ON THE HIGHEST MTN RIDGES. NO APPRECIABLE ACCUM IS EXPECTED. POPS
DIMINISH IN THE EARLY MRNG HOURS. THE SETUP REMAINS SIMILAR FROM
THERE THRU THE DAY FRIDAY...AS THE LOW REMAINS OVER THE MID-ATLANTIC
COAST. LAPSE RATES WILL BE SLIGHTLY POORER WITH THE BETTER COLD
AIR OFF TO THE EAST...BUT TEMPS/DEWPTS REBOUND BY 5-7 DEGREES...AND
THESE SUGGEST SOME INSTABILITY STILL WILL DEVELOP. CHANCES OVERALL
ARE LESSER WITH MODEL QPF BEING LESS WIDESPREAD.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 225 PM THURSDAY...ONE MORE POCKET OF COLD AIR ROTATES AROUND
THE UPPER LOW AND ACROSS THE AREA FRIDAY NIGHT BEFORE WARMER MID
LEVEL AIR MOVES IN ON SATURDAY. THIS WILL COMBINE WITH THE LINGERING
LOW LEVEL MOISTURE ACROSS THE MOUNTAINS TO KEEP ISOLATED TO
SCATTERED SHOWERS THERE DURING THE EVENING BEFORE ENDING BY
MIDNIGHT. A WEAK WARM FRONT TRAILING FROM A SURFACE LOW OVER THE
GREAT LAKES WILL BRUSH THE MOUNTAINS ON SATURDAY CREATING THE
POTENTIAL FOR ISOLATED SHOWERS. FINALLY...A BACK DOOR COLD FRONT
DROPS INTO THE AREA BY SUNDAY AS THE GREAT LAKES LOW MOVES EAST.
SOME WEAK SHORT WAVE ENERGY WILL CROSS THE AREA SATURDAY NIGHT AND
SUNDAY EVEN AS HEIGHTS RISE BETWEEN THE DEPARTING UPPER LOW AND A
RIDGE DEVELOPING OVER THE CENTRAL CONUS. BEST CHANCE FOR CONVECTION
WILL BE THE NORTHERN NC MOUNTAINS...WITH ISOLATED CONVECTION
POSSIBLE ACROSS THE I-40 CORRIDOR. TEMPS REBOUND TO NEAR NORMAL
LEVELS ON SATURDAY THEN RISE TO NEARLY 10 DEGREES ABOVE NORMAL ON
SUNDAY.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 245PM THURSDAY...THE EXTENDED PERIOD BEGINS SUNDAY NIGHT WITH
A STALLED FRONTAL BOUNDARY DRAPED W TO E ACROSS THE REGION
UNDERNEATH FAIRLY ZONAL FLOW ALOFT.  THE BOUNDARY WILL RETREAT NORTH
AS A WARM FRONT AS SUBTROPICAL HIGH PRESSURE OVER THE SARGASSO SEA
INDUCES WARM SOUTHERLY FLOW ACROSS THE REGION BEGINNING MONDAY
AFTERNOON AND PERSISTING THROUGH AT LEAST WEDNESDAY. THE RETURN FLOW
WILL ALLOW TEMPERATURES TO QUICKLY REBOUND TO GENERALLY 5-10 DEGREES
ABOVE NORMAL THROUGH MID TO LATE WEEK.  DEWPOINTS WILL GRADUALLY
RETURN TO THE UPPER 50S AND LOWER 60S DURING THIS TIME AS WELL AND
WITH THE INCREASING DIURNAL INSTABILITY...THERE IS A CHANCE OF
SHOWERS AND THUNDERSTORMS EACH DAY...WITH THE BEST COVERAGE EXPECTED
OVER THE MOUNTAINS.  THE ECMWF REMAINS LESS OPTIMISTIC ABOUT
COVERAGE THROUGH MID-WEEK WHILE THE GFS MAINTAINS SCATTERED TO
WIDESPREAD COVERAGE EACH AFTERNOON.  THE FORECAST REFLECTS A BLEND
OF THE GUIDANCE AS THE PATTERN CERTAINLY WARRANTS SLIGHT CHANCE
COVERAGE EAST AND CHANCE COVERAGE WEST.

AN OPPORTUNITY EXISTS FOR MORE WIDESPREAD COVERAGE OF SHOWERS AND
STORMS WEDNESDAY EVENING INTO FRIDAY AS ANOTHER CLOSED LOW DROPS
INTO THE UPPER MIDWEST AND GREAT LAKES REGIONS AND A FEW LOBES OF
VORTICITY ROTATE AROUND THE BASE OF THE LOW ACROSS THE OH AND TN
VALLEYS AND INTO VIRGINIA AND THE CAROLINAS. HOWEVER...GIVEN THE
SOMEWHAT ANOMALOUS NATURE OF THIS PATTERN...AGAIN THE GUIDANCE
DIFFERS ON THE EXACT PLACEMENT AND EVOLUTION OF THE UPPER-LEVEL
FLOW. WHILE POPS INCREASE SLIGHTLY INTO LATE WEEK IN RESPONSE TO THE
ANTICIPATED BETTER FORCING ALOFT...THERE IS TOO MUCH UNCERTAINTY TO
WARRANT MORE AGGRESSIVE COVERAGE ATTM.  FOR NOW...THESE FEATURES DO
LITTLE TO CHANGE THE ABOVE NORMAL TEMPERATURES WE EXPECT THROUGH THE
END OF NEXT WEEK.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
AT KCLT...UPPER LEVEL LOW OVER THE REGION WILL MAINTAIN GOOD
MIDLEVEL LAPSE RATES OVER THE REGION...AND HIGH BASED SCT SHRA/TSRA
WILL DEVELOP VIA DIURNAL HEATING THIS AFTN. DEEPER MOISTURE ARRIVES
FROM THE N BY EARLY EVENING AND THIS IS EXPECTED TO LEAD TO MORE
ROBUST AND WIDESPREAD SHRA AND A BETTER CHANCE OF RESTRICTED
VSBY...HENCE TEMPO. SOME POTENTIAL FOR ENHANCED GUSTS WITH THE
SHRA EXISTS BUT HARD TO PIN DOWN FOR INCLUSION IN TEMPO. CHANCE OF
SHRA DIMINISHES OVERNIGHT. VIRTUALLY ALL CIG GUIDANCE INDICATES
BASES WILL REMAIN VFR. WINDS WILL STAY IN THE NW QUAD THRU THE
PERIOD...BACKING TOWARD W FOR A TIME TONIGHT AS SFC LOW MOVES
NWD ALONG THE OUTER BANKS. THOUGH THE EFFECTS OF THE LOW WILL BE
LESS FRIDAY...LAPSE RATES ARE STILL SUFFICIENT TO EXPECT GOOD CU
DEVELOPMENT. A TIGHT PRS GRADIENT WILL ALLOW GUSTY WINDS TO RETURN.

ELSEWHERE...GENERALLY AS AT KCLT...BUT WITH PRECIP CHANCES SOMEWHAT
LOWER ACRS KGSP/KGMU/KAND PER CONSENSUS OF HIGH-RES GUIDANCE. KAVL
WILL CONTINUE TO SEE BRISK NWLY GUSTS INTO THE EVENING...AND LO
LEV MOISTURE IS A BIT MORE SIGNIFICANT...SUGGESTING A SMALL CHANCE
OF AN MVFR CIG EXISTS OVERNIGHT.

OUTLOOK...A LOW CHANCE OF SHRA/TSRA WILL PERSIST FRI AFTN MAINLY
ACROSS THE NC SITES...BEFORE UPPER LOW DEPARTS TO THE EAST. DRY
HIGH PRES RETURNS SATURDAY...WHILE ANOTHER COLD FRONT APPROACHES
FROM THE NORTH THRU SUNDAY.

CONFIDENCE TABLE...

            19-01Z        01-07Z        07-13Z        13-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  94%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JMP
NEAR TERM...WIMBERLEY
SHORT TERM...RWH
LONG TERM...JMP
AVIATION...WIMBERLEY



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