Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 070728
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
328 AM EDT THU MAY 7 2015

.SYNOPSIS...
A WEAK RIDGE OF HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN
CAROLINAS TODAY AND TONIGHT...AS LOW PRESSURE MOVES SLOWLY NORTHWARD
AND ORGANIZES OFF THE SOUTHEAST COAST. THE LOW PRESSURE CENTER IS
EXPECTED TO STALL OFF THE SOUTH CAROLINA COAST FRIDAY AND
SATURDAY...AND MAY MOVE SLOWLY NORTHWARD ALONG THE NORTH CAROLINA
COAST AND OUTER BANKS SUNDAY AND INTO MONDAY. MEANWHILE...WE WILL BE
LEFT WITH WEAK HIGH PRESSURE THROUGH THE WEEKEND. A COLD FRONT WILL
EVENTUALLY MOVE IN FROM THE WEST...PERHAPS TUESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 320 AM EDT THURSDAY...UPPER RIDGE AXIS CONTINUES TO PREVAIL
ACROSS THE SOUTHEAST WHILE A CLOSED UPPER/SFC LOW SLIDES INTO THE
PICTURE OFF THE FL/GA COAST.  CLOSER TO HOME...TEMPERATURES AROUND
THE REGION INDICATE LIMITED RADIATIONAL COOLING DUE TO INTRUDING
MID/HIGH CLOUDS FROM THE ABOVE MENTIONED LOW PRESSURE SYSTEM.  SFC
FLOW ACROSS THE REGION IS RATHER CALM...WITH A FEW LOCATIONS
REPORTING LIGHT NORTHERLY WINDS.

CURRENTLY...NHC ANALYSIS PLACES THE CENTER OF THE CIRCULATION ABOUT
220 MILES SSE OF MYRTLE BEACH SC AND NEARLY STATIONARY...WITH THEIR
FCST INDICATING SOME ADDITIONAL DEVELOPMENT LIKELY OVER THE NEXT 48
HOURS.  FORTUNATELY...MINIMAL WESTWARD MOVEMENT IS FCST THUS
LITTLE/NO IMPACT IS EXPECTED ACROSS THE CAROLINAS THROUGH THE NEAR
TERM.  THUS...PARTLY/MOSTLY CLOUDY SKIES WILL PREVAIL OVER THE NC/SC
PIEDMONT THROUGH THE PERIOD AS MID/HIGH LEVEL CLOUDS CONTINUE TO
ADVECT OVERHEAD.  MOVING WESTWARD INTO NORTHEAST GA AND THE WESTERN
CAROLINAS...EXPECTING ABOVE MENTIONED MID/HIGH CIRRUS TO BE LESS
DENSE THUS ALLOWING FOR DIFFERENTIAL HEATING TO STEEPEN LAPSE RATES
AND THEREFORE INITIATE LLV CU DEVELOPMENT.  ASIDE FOR LOW POPS OVER
THE FARTHEST EAST ZONES TO ACCOUNT FOR MOISTURE WRAPPING AROUND THE
OFFSHORE LOW...EXPECTING RIDGING TO PREVAIL OVER THE LOW TERRAIN
WHERE ANY CAPPING WILL HOLD.  AS USUAL...LATEST NAM GUIDANCE IS MORE
ROBUST WITH INSTABILITY/CONVECTION THAN THE GFS AS NAM SOUNDINGS
INDICATE UPWARDS OF 5-7 HUNDRED JOULES SBCAPE AT KAVL AS OPPOSED TO
1-2 HUNDRED IN THE GFS.  THEREFORE...CARRIED POPS FOR ISOLATED TO
SCATTERED SHRA/TSRA OVER THE MOUNTAINS WHERE EASTERLY UPSLOPING
COULD ENHANCE CONVECTION THIS AFTERNOON.  OTHERWISE...TEMPERATURES
THROUGH THE PERIOD WILL REMAIN ABOVE NORMAL LEVELS.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
AS OF 215 AM THURSDAY...THE MODELS HAVE COME INTO BETTER AGREEMENT
WITH THE POSITION AND MOVEMENT OF THE LOW OF SOMEWHAT TROPICAL
NATURE AND ORIGIN THIS WEEKEND. THERE NOW IS A CONSENSUS THAT THE
LOW WILL STALL OFF THE SC COAST THRU FRIDAY AND SATURDAY...THEN
PERHAPS START TO MOVE NORTHWARD OVER THE NC COASTAL PLAIN AND OUTER
BANKS ON SUNDAY. ALTHO THE DIFFERENCE BETWEEN PREVIOUS RUNS IS
RELATIVELY SMALL...THE HUNDRED OR SO MILES FARTHER EAST WILL MAKE
THE DIFFERENCE OVER THE EASTERN ZONES BETWEEN SEEING A DECENT CHANCE
OF SHOWER ACTIVITY OR REMAINING DRY FOR THE MOST PART. WHAT WE WILL
PROBABLY BE LEFT WITH...IF THE GUIDANCE IS CORRECT...IS THE TYPICAL
OUTCOME FOR THE WESTERN CAROLINAS WHEN THERE IS A TROPICAL-ISH LOW
OFF THE COAST. THAT IS...A DIURNAL LOW CHANCE OF SHOWER ACTIVITY
OVER THE MTNS...PERHAPS A BAND OF SHOWERS REACHING THE I-77 CORRIDOR
BEFORE DYING...AND NOT MUCH IN BETWEEN. SUBSIDENCE AND DRY AIR
ENTRAINED AROUND THE FAR WRN PERIPHERY OF THE SYSTEM SHOULD BE
INHOSPITABLE TO THE DEVELOPMENT OF ANYTHING MORE THAN SCATTERED
SHOWERS. THAT GOES FOR THE PERIOD FRIDAY THRU SUNDAY...ALTHO SUNDAY
MIGHT HAVE THE BEST CHANCE OF THE LOT FOR CONVECTIVE COVERAGE. TEMPS
SHOULD REMAIN ABOVE NORMAL THRU THE PERIOD...WITH SLIGHLY LOWER
TEMPS IN THE AREA E OF I-77 WHERE CLOUD COVER MIGHT BE THICKER AND A
FEW SHOWERS MAY STRAY WESTWARD.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
AS OF 325 AM THURSDAY...THE GUIDANCE DEVELOPS SOME TIMING
DIFFERENCES AS TO WHEN LOW PRESSURE MOVES NORTHWARD ALONG THE NC
COAST AND OUTER BANKS SUNDAY NIGHT THROUGH MONDAY...BUT AT LEAST
THERE IS GENERAL AGREEMENT WITH THE TRACK. THAT SHOULD KEEP THE
AFFECTS FROM THE LOW AT A MINIMUM AND CONFINED MAYBE TO THE AREA
ALONG AND E OF I-77...BUT THAT MIGHT BE PESSIMISTIC. THAT WILL LEAVE
US WITH MORE OF THE SAME...WHICH IS A DIURNAL SHOWER/T-STORM CHC
OVER THE MOUNTAINS. NO SIGNIFICANT CHANGES WERE MADE.

REMAINDER OF PREVIOUS DISCUSSION...

TUESDAY AND WEDNESDAY...THE PERSISTENT WESTERN CONUS TROF WILL EJECT
INTO THE PLAINS...AND LIFT NORTH INTO THE GREAT LAKES. THE FLOW WILL
FLATTEN THE SOUTHEASTERN CONUS RIDGE...BUT NOT COMPLETELY.
STILL...BOTH THE GFS AND ECMWF SHOW A COLD FRONT ASSOCIATED WITH THE
UPPER WAVE PUSHING THRU THE AREA ON TUESDAY. THE GFS HAS IT THRU BY
EARLY MORNING...WHILE THE ECMWF PUSHES IT ACRS TUESDAY EVENING.
AGAIN...THE WPC PREFERENCE IS MORE IN LINE WITH THE EC...SO WILL
CONTINUE THE CHC POPS FOR SHWRS AND TSTMS...WITH ABOVE NORMAL TEMPS
TUESDAY. THEN DRY WEDNESDAY WITH SLIGHTLY COOLER TEMPS.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD.  PRIMARILY
A WIND FORECAST ONCE AGAIN AS THE PRESSURE GRADIENT TIGHTENS DUE TO
APPROACHING SOUTHEAST COASTAL LOW.  INITIALIZED TAF UNDER BKN HIGH
CIRRUS AS MOISTURE STREAMS IN ALOFT FROM SAID LOW...WITH LIGHT ENE
FLOW.  NE WINDS WILL INCREASE THROUGH THE DAY ON THURSDAY WITH GUSTS
LIKELY DURING THE AFTERNOON AS THE MIXED LAYER DEEPENS ALLOWING
MOMENTUM TRANSFER OF INCREASED LLV FLOW AROUND THE COASTAL SYSTEM.
CIGS WILL CONTINUE TO LOWER TO THE MID LEVELS THROUGH THE AFTERNOON
WITH 10KFT CIGS PREVAILING BY PERIODS END.

ELSEWHERE...SIMILAR TO THAT OF KCLT ABOVE WITH INCREASING MID/HIGH
CLOUDS TONIGHT AND THROUGH THE DAY ON THURSDAY WITH SOME LLV CU
POSSIBLE AT KAVL AND KAND WHERE DIFFERENTIAL HEATING WILL STEEPEN
LAPSE RATES.  WINDS WILL ALSO INCREASE OUT OF THE NE...HOWEVER
SHOULD BE WEAKER FURTHER WEST DUE TO PROXIMITY OF BEST PRESSURE
GRADIENT FORCING.  NO WX MENTIONED AT ANY SITE.

OUTLOOK...A MOIST AIRMASS WITH POSSIBLE UPSLOPE ENHANCEMENT ALONG
THE HIGH TERRAIN WILL SUPPORT DIURNAL SHRA/TSRA THROUGH THE
WEEKEND.  ALTHOUGH RAIN CHANCES WILL BE MINIMAL OUTSIDE OF THE
MTNS...CANT RULE OUT LIGHT SHRA AS MOISTURE WRAPS AROUND SOUTHEAST
COASTAL LOW WITH LLV CIGS ALSO A POSSIBILITY THIS WEEKEND AND INTO
THE START OF THE NEW WORK WEEK.

CONFIDENCE TABLE...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     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 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...PM
NEAR TERM...CDG
SHORT TERM...PM
LONG TERM...PM
AVIATION...CDG



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