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 121731
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
131 PM EDT SAT APR 12 2014

.SYNOPSIS...
A WARM SOUTHERLY FLOW OF AIR WILL CONTINUE THROUGH THE WEEKEND.
MOISTURE AHEAD OF AN APPROACHING COLD FRONT IS EXPECTED TO
OVERSPREAD THE REGION ON MONDAY...WITH THE FRONT CROSSING THE AREA
ON TUESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 125 PM EDT SATURDAY...CURRENT FORECAST REMAINS ON TRACK.
LATEST VISIBLE SATELLITE IMAGERY INDICATES EXPANDING FAIR WX CU
FIELD ACROSS THE FOOTHILL/PIEDMONT REGIONS AS PREVIOUSLY FORECAST.
WINDS REMAIN GENERALLY LIGHT WITH OCCASIONAL GUSTS BEING OBSERVED
ACROSS THE UPSTATE AS THE MIXED LAYER DEEPENS.  NO SIGNIFICANT
CHANGES NEEDED/MADE PERTAINING TO THIS UPDATE.

PREVIOUS DISCUSSION...

AS OF 3 AM...NICE SPRING-TIME WEATHER EXPECTED THROUGH THE NEAR
TERM. A RIDGE OF SFC HIGH PRESSURE CENTERED OVER THE WESTERN
ATLANTIC TODAY AND TONIGHT. AT H5...ZONAL FLOW WILL TRANSITION TO
RIDGING ALONG THE ATLANTIC COAST. THIS PATTERN WILL SUPPORT LIGHT
RETURN FLOW ACROSS THE SOUTHEAST U.S. THROUGH TONIGHT. AFTER THE
PASSAGE OF MORNING DEBRIS CLOUDS...SKY CONDITIONS SHOULD BECOME
MOSTLY CLEAR TO CLEAR. HIGH TEMPERATURES ARE FORECAST TO RANGE FROM
THE MID 70S WITHIN THE MTN VALLEYS TO AROUND 80 ACROSS THE FOOTHILLS
AND PIEDMONT. ONGOING RETURN FLOW SHOULD FAVOR AFTERNOON DEWPOINTS
IN THE MID TO UPPER 40S...YIELDING RH VALUES IN THE LOW 30S. A BLEND
OF PREFERRED MOS GUIDANCE INDICATES LOW TEMPERATURES IN THE UPPER
40S ACROSS THE MTNS TO THE MID 50S EAST.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 115 PM SATURDAY...AS WE HEAD TOWARD THE START OF THE WORK
WEEK...IN ADVANCE OF OHIO VALLEY SYSTEM...THE ONSET OF GULF TAP AND
THE INCREASE IN LLVL WAA/UPSLOPE FLOW...A FEW SHOWERS STILL COULD
DEVELOP NEAR THE HIGHER TERRAIN BY MONDAY MORNING. OTHERWISE...
CLOUDS SHOULD BE ON THE INCREASE SUNDAY NIGHT WITH TEMPERATURES
REMAINING MILD INTO MONDAY MORNING.

WITH THE COMBINATION OF S/WV ENERGY EJECTING FROM THE PLAINS L/WV
AND THE STEADY INCREASE IN BROAD UPGLIDE/UPSLOPE FLOW...FORCING
FOR EXPANDING SHOWER ACTIVITY SHOULD INCREASE THROUGHOUT MONDAY.
WITH CONSIDERABLE CLOUDINESS AND PCPN LIKELY...FCST SNDGS ARE
EXPECTEDLY DEPICTING JUST WEAK CAPE VALUES DURING THE AFTERNOON...
AND REGIONALLY THE GREATEST CHANCE FOR ROBUST THUNDERSTORMS IS
SHAPING UP TO BE WELL WEST AND SW OF THE CWFA.

WITH BAND OF DEEP LYR RH PROGGED TO TRANSLATE INTO THE CWFA MONDAY
NIGHT...WIDESPREAD SHOWERS ARE LIKELY TO BE THE RESULT. THERE IS A
POTENTIAL FOR HEAVIER RAINFALL BUT UNCERTAINTY LIES WITH RESPECT TO
THE GREATEST THREAT AREA THE POSSIBILITY OF CONSIDERABLE GULF DEEP
CONVECTION INTERRUPTING NORTHWARD MOISTURE TRANSPORT.

I WOULD EXPECT DEEP CONVECTIVE CVRG TO REMAIN CONSIDERABLE
THROUGHOUT TUESDAY COINCIDENT WITH THE COLD FRONTAL PASSAGE. THE
POTENTIAL FOR ANY STRONGER STORMS SEEMS TO BE DEPENDENT OF FRONTAL
TIMING...WITH THE SREF PROBABILITIES FOR GREATEST RISK BEING IN THE
PIEDMONT DURING THE AFTERNOON.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 345 AM SATURDAY...THE FRONT APPROACHING THE AREA BY THE END OF
THE SHORT RANGE...WILL CROSS THE AREA EARLY IN THE MEDIUM RANGE. THE
GFS REMAINS FASTER THAN THE ECMWF WITH THIS SYSTEM. IN FACT...THE
ECMWF HAS SLOWED SO MUCH THAT THE FRONT STALLS JUST OFF SHORE WITH
WAVES OF LOW PRESSURE MOVING ALONG THE FRONT SPREADING MOISTURE AND
PRECIP BACK INTO THE AREA THRU THURSDAY. GIVEN THE DIFFERENCES...
HAVE TRENDED TOWARD WPC AND ENSEMBLE MEAN GUIDANCE. THIS WOULD
SUGGEST THE FRONT CROSSES THE AREA TUESDAY WITH DRY HIGH PRESSURE
BUILDING IN ON WED. THERE IS STILL QUITE A BIT OF UNCERTAINTY
REGARDING THE AMOUNT OF INSTABILITY AND SHEAR ASSOCIATED WITH THIS
SYSTEM. ALTHOUGH PW VALUES ARE SUGGESTED TO BE AS MUCH AS 2.5
STANDARD DEVIATIONS ABOVE NORMAL...THERE IS STILL UNCERTAINTY ON THE
AMOUNT OF PRECIP POTENTIAL DUE TO THE DIFFERING SPEED OF THE SYSTEM.
THEREFORE...WILL NOT INCLUDE AN HWO MENTION...BUT WILL HAVE TO KEEP
AN EYE OUT AS THE SYSTEM APPROACHES.

ALTHOUGH DRY HIGH PRESSURE MOVES IN FOR WED AND THU...IT SETS UP IN
A COLD AIR DAMMING PATTERN. THERE COULD BE LOW CLOUDS RETURNING TO
THE AREA IN THE MOIST SLY LOW LEVEL FLOW DEVELOPING OVER THE DAMMING
HIGH. THE GFS SHOWS PRECIP DEVELOPING AHEAD OF A WEAK COLD FRONT
BRINGING DEEP MOISTURE AND LIFT OVER THE COLD DOME. THE ECMWF
REMAINS DRY...SO HAVE KEPT THE DRY FCST IN PLACE. TEMPERATURES WILL
REMAIN BELOW NORMAL THRU THE PERIOD...WITH FROST/FREEZE CONCERNS
POSSIBLE MAINLY TUE AND WED NITES.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS WILL PREVAIL THROUGH THE TAF
PERIOD AS SURFACE HIGH PRESSURE SLIDES EAST.  DAYTIME HEATING
CONTINUES TO ENHANCE LOW LEVEL LAPSE RATES AS MOISTURE ADVECTS IN
FROM THE SOUTH.  FAIR WX CU FIELD HAS DEVELOPED ACROSS THE HIGH
TERRAIN AND WILL LIKELY SPREAD EAST INTO THE FOOTHILLS/PIEDMONT OF
THE CAROLINAS.  WINDS ACROSS THE PIEDMONT HAVE BEEN SLOW TO BACK
SOUTHERLY...BUT SHOULD DO SO IN THE NEXT HOUR OR SO THUS WILL GO
AHEAD AND PREVAIL SUCH.  SKC WILL BE LIKELY OVERNIGHT BEFORE
MOISTURE ADVECTION IN THE LOW LEVELS YIELDS REDEVELOPMENT OF LOW
LEVEL SKY COVER ACROSS THE PIEDMONTS OF NC/SC BY MORNING.  NOT
EXPECTING ANY CEILINGS TO DEVELOP AS MOIST LAYER REMAINS SHALLOW
THEREFORE CARRIED ONLY FEW/SCT THROUGH THE PERIOD.  WINDS TOMORROW
WILL HOLD SOUTHERLY IN THE 5-10KTS RANGE.

OUTLOOK...HIGH PRESSURE WILL REMAIN ACROSS THE TERMINALS THROUGH THE
WEEKEND. A LOW PRESSURE SYSTEM WILL ORGANIZE ACROSS THE DEEP SOUTH
EARLY NEXT WEEK. MOISTURE AND LIFT ASSOCIATED WITH THIS SYSTEM WILL
LIKELY YIELD RESTRICTIVE CONDITIONS FROM EARLY MON MORNING THROUGH
TUESDAY.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-17Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  93%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  93%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  91%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  93%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  93%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  93%

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...RWH
NEAR TERM...CDG/NED
SHORT TERM...CSH
LONG TERM...RWH
AVIATION...CDG






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