Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KGSP 300557
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
157 AM EDT SAT AUG 30 2014

.SYNOPSIS...
A WEAK NEARLY STATIONARY FRONT WILL LINGER OVER NORTH CAROLINA
TONIGHT AND THEN DISSIPATE BY SATURDAY NIGHT.  A BERMUDA HIGH WILL
SET UP FOR THE WEEKEND AND EARLY NEXT WEEK...BRINGING TYPICAL
SUMMERTIME HEAT AND HUMIDITY...WITH SCATTERED AFTERNOON SHOWERS AND
THUNDERSTORMS EACH DAY.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 150 AM EDT SATURDAY...LOW LEVEL STRATUS CLOUD DECK CONTINUES
TO DEEPEN AND EXPAND ACROSS WESTERN NC EARLY THIS MORNING.  GUIDANCE
HAS BEEN ON TRACK REGARDING TRENDS...HOWEVER MAGNITUDE OF THE SKY
COVER WAS UNDER DONE.  THUS...INCREASED SKY COVER IN THE FORECAST
THROUGH THE OVERNIGHT ALL THE WHILE ALSO HOLDING MIN TEMPERATURES A
DEGREE OR TWO WARMER BENEATH AND ADJACENT TO THIS STRATUS DECK.
LATEST MAV/MET/LAMP CONTINUE TO INDICATE PATCHY FOG DEVELOPMENT
ACROSS THE NC PIEDMONT WITH PATCHY DENSE FOG IN AND AROUND THE
MOUNTAIN VALLEYS BY MORNING.  ALTHOUGH CONFIDENCE REMAINS LOW DUE TO
ABOVE MENTIONED STRATUS AFFECTING TEMPERATURE TRENDS...OPTED TO KEEP
FORECAST UNCHANGED AT THIS TIME.

PREVIOUS DISCUSSIONS...

EVENING UPDATE...MADE SOME MINOR TWEAKS TO THE MIN TEMP GRID AND ADJ
HR/LY TD/S TO FIT CURRENT TRENDS. A SFC BNDRY REMAINS ACROSS THE SRN
ZONES AND THE OP MODELS SHOW WEAK ATL MOIST ADV OVERNIGHT AS BL
WINDS VEER S/LY. THIS WILL KEEP THE SFC LAYER MOIST AND ALLOW FOR
FG/BR DEVELOPMENT ALONG WITH LOW STCU ACROSS THE ERN ZONES BEFORE
DAYBREAK. THE FG WILL LIKELY BECOME MOST DENSE ACROSS THE MTN
VALLEYS...BUT A WIDESPREAD EVENT IS NOT PROBABLE.

AS OF 130 PM EDT...LOW STRATUS ARE FINALLY DISSOLVING OVER OUR
PORTION OF THE NW NC PIEDMONT THOUGH OVC SKIES REMAIN JUST NE OF
CHARLOTTE. THESE CLOUDS ARE EXPECTED TO CONTINUE TO BREAK UP THROUGH
MID AFTERNOON. THE NEARLY STATIONARY BOUNDARY ON THE SRN FRINGE OF A
WEDGELIKE SFC RIDGE WHICH CAUSED THESE CLOUDS TO FORM EARLY THIS
MRNG REMAINS NEAR THE NC/SC BORDER. DEWPOINTS ARE CURRENTLY HIGHEST
IN AN ARC FROM ASHEVILLE TO SPARTANBURG TO CHARLOTTE...A RESULT OF
MOISTURE POOLING ALONG THE BOUNDARY. THIS HAS IMPLICATIONS FOR THE
FORECAST TONIGHT. HOWEVER...THOUGH ANALYZED CAPE VALUES ARE NOTABLY
HIGHER WITHIN THE AREA OF HIGHER DEWPOINTS...LOW TO MID LEVEL LAPSE
RATES ARE NOT GOOD ENOUGH EAST OF THE MTNS TO EXPECT DEEP
CONVECTION. HAVE MAINTAINED ISOLD TSRA MENTION OVER THE MTNS AND SRN
ESCARPMENT AREAS...BUT THAT/S IT.

TONIGHT THE UPPER RIDGE CONTINUES TO SHIFT EWD INTO CLASSIC BERMUDA
HIGH POSITION AS TROUGH MOVES INTO THE MISSISSIPPI VALLEY. ANY
REMNANT OF THE STATIONARY BOUNDARY APPEARS TO WASH OUT...AT LEAST
ENOUGH SO THAT ANY UPGLIDE WILL DIMINISH...SO LOW CLOUDS NOT
EXPECTED OVER THE BOUNDARY TONIGHT. VERY WEAK SOUTHERLY LLVL FLOW
WILL PREVAIL AGAIN OVER THE AREA WHICH DOES PROMPT THOUGHTS OF LOW
STRATUS OR FOG CREEPING UP FROM THE COAST...BUT MOISTURE DOES NOT
LOOK ESPECIALLY GOOD THIS FAR INLAND. A BETTER CASE CAN BE MADE FOR
FOG TO FORM WHERE SFC MOISTURE IS POOLING ALONG THE FRONT THIS
AFTN...GIVEN GOOD GUIDANCE SUPPORT FOR TEMPS COOLING BELOW THE
EXPECTED CROSSOVER TEMPS AS WELL AS WITH THE WEAK SOUTHERLY FLOW.
WILL ADVISE EVENING SHIFT TO CONSIDER THREAT OF PATCHY DENSE FOG
OVERNIGHT.

THAT UPPER TROUGH DOES BRING SOME WEAK DISTURBANCES NWD INTO THE
TENN VALLEY TOMORROW AFTN BUT THESE WILL HAVE MINIMAL IMPACT ON
FORCING OVER OUR AREA. LAPSE RATES AND MODEL CAPE VALUES ARE BEST
OVER THE SRN MTNS AND ADJACENT BLUE RIDGE...WHERE THE UPPER HEIGHTS
ARE A LITTLE LOWER. SOUTHERLY FLOW INTO THESE AREAS MAY ALSO ENHANCE
THE COVERAGE...SO I WILL MAINTAIN THE HIGHEST POPS THERE. FURTHER
EAST SUBSIDENCE CAPPING WILL KEEP THE FCST DRY. MAINLY DIURNAL
CUMULUS WILL BE SEEN FOR SKY COVER WITH MAX TEMPS NEAR NORMAL.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...
AS OF 200 PM FRIDAY...A WEAKENING SHORT WAVE TROUGH EJECTING FROM
THE GREAT PLAINS WILL ACT TO NUDGE THE SOUTHEAST CONUS UPPER HIGH
OFF THE SOUTHEAST COAST EARLY IN THE SHORT TERM...WHILE GENERALLY
RESULTING IN AN OVERALL LOWER AMPLITUDE UPPER PATTERN. A BERMUDA
HIGH WILL BECOME ESTABLISHED WITHIN THIS REGIME...WHICH WILL ACT TO
INCREASE MOISTURE AND INSTABILITY ACROSS THE WESTERN CAROLINAS AND
NORTH GEORGIA. ADDITIONALLY...A PLUME OF DEEP MOISTURE ACCOMPANYING
THE SHORT WAVE TROUGH/WEAKENING FRONTAL ZONE WILL APPROACH THE
FORECAST AREA BY SUNDAY MORNING. THIS SHOULD RESULT IN INCREASING
CHANCES FOR DEEP CONVECTION BEGINNING ACROSS THE WEST SUNDAY
NIGHT...WITH CHANCES INCREASING AND OVERSPREADING THE REMAINDER OF
THE AREA BY SUNDAY AFTERNOON. TERRAIN EFFECTS AND LEE TROUGH
INTERACTING WITH LINGERING MOISTURE PLUME...ALONG WITH RESPECTABLE
SBCAPE VALUES (GENERALLY 1500 TO 2500 J/KG PER FORECAST SOUNDINGS)
SHOULD SUPPORT SCATTERED TO PERHAPS NUMEROUS CONVECTION...WITH THE
HIGHEST POPS OCCURRING NEAR THE NC BLUE RIDGE. SHEAR WILL REMAIN
QUITE WEAK THROUGHOUT THE PERIOD...SO SEVERE STORM CHANCES WILL BE
LIMITED TO THE ISOLATED PULSE VARIETY.

WITH FRONTAL ZONE EXPECTED TO WEAKEN ACROSS THE EASTERN CONUS...
EXPECT A MORE TYPICAL DIURNAL WIDELY SCATTERED CONVECTIVE TREND TO
RETURN BY THE END OF THE PERIOD. THE BREAKDOWN OF THE RIDGE AND
INCREASING CLOUD COVER/CONVECTION SHOULD SPELL A PERIOD OF SLIGHTLY
BELOW NORMAL MAX TEMPS/NEAR NORMAL MINS THROUGH THE PERIOD.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 150 PM FRIDAY...THE MEDIUM RANGE PERIOD BEGINS 00Z TUESDAY
WITH A NEARLY ZONAL PATTERN ACROSS THE NATION AS AN UPPER RIDGE
DEPARTS EAST FROM THE ATLANTIC COAST. A SUBTROPICAL RIDGE BEING
SUPPRESSED SOUTH OVER FLORIDA AT 00Z TUES WILL RETROGRADE OVER THE
DEEP SOUTH BEING CENTERED OVER THE GULF STATES IN MID WEEK. THIS
RIDGE WILL EXPAND INTO LATE WEEK CREATING A GREATER AMPLITUDE
PATTERN THURS AND FRI WITH THE JET STREAM FROM CALIFORNIA TO THE
DAKOTAS TO NEW ENGLAND. THERE APPEARS TO BE A TREND IN THE
MODELS...ESPECIALLY IN THE GFS...OF MOVING THE CENTER OF THE RIDGE
EVEN FARTHER WEST AT THE END OF NEXT WEEK. IF THE CENTER OF THE
RIDGE SETS UP AROUND OKLAHOMA NEXT WEEKEND...OUR PATTERN MAY SHIFT
FROM BEING IN A RIDGE TO BEING IN NW FLOW WHICH WOULD BRING MCS
SYSTEMS FROM OVER THE TOP OF THE RIDGE TO THE CAROLINAS.

A WEAK COLD FRONT WILL DROP DOWN FROM THE NORTH IN MID WEEK BUT IT
IS QUESTIONABLE WHETHER THE FRONT WILL REACH OUR AREA BEFORE
DISSIPATING. THIS BOUNDARY WILL PROVIDE A FOCUS FOR CONVECTION IN
MID WEEK ESPECIALLY IN THE PM HOURS. LOW LEVEL WIND WILL BE LIGHT
AND VARY FROM DAY TO DAY DEPENDING ON THE INFLUENCES OF PASSING
SHORTWAVES TO THE NORTH...A PERSISTENT LEE TROUGH AND
WHETHER THE FRONT MAKES IT THROUGH OR NOT.

TEMPERATURES ARE FORECAST TO BE ABOVE NORMAL THROUGH THE PERIOD
UNDER THE UPPER RIDGE. MAXES ABOVE BY 5 TO 7 DEGREES IN MID WEEK AND
3 TO 5 ABOVE ON FRIDAY.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...VFR WILL PREVAIL THROUGH THE OVERNIGHT BEFORE A BRIEF
PERIOD OF FOG/STRATUS DEVELOPMENT INCREASES FLIGHT RESTRICTIONS TO
MVFR LEVELS.  THIS WAS HANDLED WITH A 3HR TEMPO MENTIONING 5SM VSBY
AND NO CIG AT THIS TIME.  BEYOND THAT...DEEP LAYER RIDGING WILL
PREVAIL THROUGH THE TAF PERIOD ACROSS THE NC PIEDMONT LEADING TO DRY
WEATHER AND MOSTLY SUNNY SKIES.  LIGHT/CALM WINDS AROUND DAYBREAK
WILL INCREASE OUT OF THE SOUTHEAST BY MID/LATE MORNING WITH POSSIBLE
AFTERNOON FEW LOW VFR CU AND SCT HIGH LEVEL CIRRUS BEING THE
DOMINATE SKY COVER IF ANY DEVELOPS.

ELSEWHERE...VFR CONDITIONS WILL PREVAIL THROUGH MUCH OF THE FORECAST
CYCLE WITH THE EXCEPTION OF MVFR LEVEL FOG/STRATUS THIS MORNING AT
KHKY AND KAND WHILE IFR CONDITIONS DUE TO FOG/STRATUS ARE POSSIBLE
AT KAVL.  LATEST SATELLITE DIFFERENCE IMAGERY AND OBS INDICATE MVFR
STRATUS DECK IS ALREADY SPREADING THROUGH WESTERN NC AND IS EXPECTED
TO CONTINUE EXPANSION.  ALL SITES WILL RETURN TO VFR LEVELS BY
MID/LATE MORNING WITH ABOVE MENTIONED DEEP LAYER RIDGING DOMINATING
THE WEATHER FOR THE DAY.  THUS...ALL SITES WILL EXPERIENCE
LIGHT/CALM WINDS INCREASING INTO THE 5-8KTS RANGE OUT OF THE SOUTH
BY EARLY AFTERNOON.  AS FOR SKY COVER...LOW VFR CU WILL HIGHLIGHT
THE SKIES BY LATE MORNING BENEATH OCCASIONAL HIGH LEVEL CIRRUS.
EXPECTING OVERALL COVERAGE OF SKY COVER TO INCREASE LATE IN THE
PERIOD AS DEEPER MOISTURE ADVECTS IN FROM THE SOUTHWEST.
ADDITIONALLY...AS THIS MOISTURE AXIS INTRUDES...SHRA/TSRA CHANCES
WILL INCREASE FOR THE LAST FEW HOURS OF THE TAF CYCLE AT KAND AND
KAVL.  HOWEVER...AS MODELS REMAIN VARIED ON THIS TIMING AND
INTENSITY OPTED FOR VCSH MENTION AT THESE TWO LOCATIONS.

OUTLOOK...MOISTURE ADVECTION BEGINNING TONIGHT WILL LEAD TO
INCREASING CHANCES FOR ISOLATED/SCATTERED DIURNAL SHRA/TSRA THROUGH
MIDWEEK WITH THE GREATEST PROBABILITIES RESIDING ALONG THE HIGH
TERRAIN. IN ADDITION...MORNING FOG/STRATUS WILL BE POSSIBLE WITH THE
MOUNTAINS ONCE AGAIN HAVING THE GREATEST CHANCES AT RESTRICTIONS.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   66%     HIGH  87%     HIGH 100%     HIGH 100%
KHKY       MED   62%     HIGH  90%     HIGH 100%     HIGH 100%
KGMU       HIGH  95%     HIGH  91%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     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...DEO
NEAR TERM...SBK/WIMBERLEY
SHORT TERM...JDL
LONG TERM...DEO
AVIATION...CDG






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.