Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 060157
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
957 PM EDT SUN JUL 5 2015

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL PREVAIL WITH AN INLAND TROUGH OF LOW
PRESSURE LINGERING THROUGH THE WEEK.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
LATE SUNDAY EVENING...BAND OF SHOWERS/THUNDERSTORMS HAD DISSIPATED
EAST OF I-95. HOWEVER...HIGH RESOLUTION GUIDANCE DEPICTS NEW
SHOWERS/THUNDERSTORMS DEVELOPING ALONG THE BOUNDARY LEFT BEHIND
BY EARLIER CONVECTION. THUS...SLIGHT CHANCE/CHANCE POPS REMAIN IN
FORECASTS OVERNIGHT MAINLY ACROSS SC COUNTIES EAST OF
I-95...INCLUDING THE CHARLESTON TRI-COUNTY REGION. THE POTENTIAL
FOR SEVERE WEATHER WILL REMAIN LOW...BUT PWATS EXCEEDING 1.75 INCH
COULD SUPPORT LOCALLY HEAVY RAIN.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
OVERVIEW: UPPER LEVEL LOW PRESSURE WILL WEAKEN AND EJECT OUT OF THE
TENNESSEE VALLEY EARLY TUESDAY. A POTENT MULTI-LAYER RIDGE WILL
BUILD WEST AND EXTEND ACROSS THE REGION THROUGH MID WEEK. THIS WILL
YIELD A RETURN TO A MORE STANDARD EARLY SUMMER CONVECTIVE REGIME
ACROSS SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA.

MONDAY: MONDAY LOOKS TO BE THE MOST ACTIVE DAY OF THE MID-RANGE
PERIOD AS UPPER LEVEL LOW PRESSURE WEAKENS AND EJECTS OUT OF THE
TENNESSEE VALLEY IN RESPONSE TO STRONG SHORTWAVE ENERGY PIVOTING
ACROSS THE WESTERN GREAT LAKES. MODELS SHOW A DEEP 500 HPA TROUGH
LINGERING ACROSS THE DEEP SOUTH IN THE WAKE OF THE DEPARTING LOW
AS A LARGE...UPPER RIDGE REMAINS POSITIONED OFFSHORE OF THE
SOUTHEAST U.S. COAST. THE COMBINATION OF SUFFICIENT LEVELS OF
MOISTURE... INSTABILITY AND LIFT WILL SUPPORT ANOTHER ROUND OF
MAINLY AFTERNOON AND EVENING SHOWERS/TSTMS. IN ADDITION...THERE
ARE SIGNALS THAT AN ENHANCED AREA OF UPPER DIFLUENCE COULD DEVELOP
OVER THE AREA DURING THE AFTERNOON AS THE RIGHT ENTRANCE REGION OF
A SUBTROPICAL JET STREAK MEANDERS EAST/NORTHEAST IN RESPONSE TO
THE EJECTION OF THE UPPER LOW. WILL HIGHLIGHT 50-60 PERCENT POPS.
FORECAST SOUNDINGS YIELD A BIT LESS IN THE WAY OF INSTABILITY
COMPARED TO THE PAST SEVERAL DAYS WITH SLIGHTLY LOWER MLCAPE AND
DCAPE...BUT LEVELS ARE STILL SUFFICIENT TO SUPPORT A FEW
STRONG/SEVERE TSTMS...MAINLY ALONG MESOSCALE BOUNDARY COLLISIONS.
CONVECTION WILL WANE DURING THE EVENING HOURS AS THE AXIS OF
STRONGEST LOW-LEVEL CONVERGENCE REDEVELOPS ALONG THE WESTERN WALL
OF THE GULF STREAM AFTER MIDNIGHT. HIGHS WILL TOP OUT IN THE LOWER
90S INLAND WITH LOWS RANGING FROM THE LOWER-MID 70S INLAND TO THE
UPPER 70S ALONG THE BEACHES AND DOWNTOWN CHARLESTON.

TUESDAY AND WEDNESDAY...MEAN RIDGING WILL BUILD WEST THROUGH THE
PERIOD WITH THE REGION REMAINING ALONG THE WESTERN FRINGE OF
ATLANTIC HIGH PRESSURE. SHOWERS AND TSTMS ARE POSSIBLE EACH
AFTERNOON AND EVENING...BUT COVERAGE WILL BE LIMITED BY WARMING
TEMPERATURES ALOFT AND SOME SYNOPTIC SUBSIDENCE ASSOCIATED WITH THE
UPPER RIDGE. INSTABILITY AND MOISTURE STILL LOOK PLENTIFUL...WHICH
SHOULD BE SUFFICIENT TO SUPPORT ISOLATED TO PERHAPS LOW-END
SCATTERED CONVECTION ALONG/AHEAD OF THE RESULTANT SEA BREEZE
CIRCULATION AS WELL AS A PERSISTENT PIEDMONT TROUGH. 20-30 PERCENT
POPS LOOK REASONABLE EACH AFTERNOON AND EVENING. HIGHS WILL WARM
INTO THE LOWER-MID 90S WITH LOWS RANGING FROM THE LOWER-MID 70S
INLAND WITH UPPER 70S AT THE BEACHES AND DOWNTOWN CHARLESTON.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
MEDIUM RANGE GUIDANCE IS IN FAIRLY GOOD AGREEMENT INDICATING HIGH
PRESSURE DOMINATING THROUGH AT LEAST FRIDAY...THEN THERE IS MORE
DISCREPANCY/FORECAST UNCERTAINTY REGARDING HOW QUICKLY THE RIDGE
BREAKS DOWN LATE WEEK AND OVER THE WEEKEND. EXPECT LOW SHOWER AND
THUNDERSTORM COVERAGE THROUGH THE PERIOD...MAINLY EACH
AFTERNOON/EVENING. TEMPERATURES WILL LIKELY BE A BIT WARMER THAN
NORMAL WITH HIGHS IN THE MID 90S AWAY FROM THE COAST AND LOWS IN THE
MID 70S INLAND AND MID TO UPPER 70S AT THE COAST. THE COMBINATION OF
SUCH TEMPS AND THE HUMIDITY LEVELS SHOULD RESULT IN HEAT INDEX
VALUES AT OR ABOVE 100 DEGREES.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
LATE SUNDAY EVENING...IFR CEILINGS HAD DEVELOPED SOUTH OF THE
ALTAMAHA RIVER...AND THERE IS A CHANCE THAT LOW CEILINGS SHOULD
SPREAD INTO KSAV LATER TONIGHT. CONFIDENCE REMAINS INSUFFICIENT
TO INTRODUCE FLIGHT RESTRICTIONS TO THE KSAV TAF...BUT WILL
CONTINUE TO ASSESS. ALSO OF CONCERN...HIGH RESOLUTION GUIDANCE
DEPICTS NEW THUNDERSTORMS DEVELOPING OVERNIGHT ESPECIALLY EAST OF
I-95. UNCLEAR WHETHER THUNDERSTORMS WILL IMPACT KCHS OR WILL
REMAIN JUST SOUTH/EAST OF THE TERMINAL. WILL AMEND TAFS AS NEEDED.
OVERALL...ODDS STILL FAVOR VFR CONDITIONS MOST/ALL OF THE
OVERNIGHT HOURS.

THUNDERSTORMS ARE EXPECTED TO REDEVELOP IN THE VICINITY OF
TERMINALS MONDAY AFTERNOON. TIMING/IMPACTS CANNOT BE PRECISELY
DETERMINED AT THIS STAGE...BUT VCTS/CBS ARE CERTAINLY JUSTIFIED
WITHIN 00Z TAFS. ASIDE FROM THUNDERSTORMS AND A LOW CHANCE FOR
BRIEF FLIGHT RESTRICTIONS IN LOWER CEILINGS AND/OR FOG AROUND
DAYBREAK MONDAY...VFR WILL PREVAIL.

EXTENDED AVIATION OUTLOOK...BRIEF FLIGHT RESTRICTIONS ARE POSSIBLE IN
MAINLY AFTERNOON/EARLY EVENING SHOWERS AND THUNDERSTORMS...WITH THE
BEST CHANCES MONDAY.

&&

.MARINE...
OVERNIGHT...S/SW WINDS 15-20 KT NORTH AND 10-15 KT WITH
OCCASIONAL GUSTS AS HIGH AS 20 KT SOUTH WILL PREVAIL. SEAS WILL
REMAIN 2-3 FT WITHIN NEARSHORE WATERS AND 3-4 FT BEYOND 20 NM.
SCATTERED THUNDERSTORMS WILL LOCALLY ALTER WINDS/SEAS OVERNIGHT.

MONDAY THROUGH FRIDAY...SOUTH TO SOUTHWEST WINDS WILL PREVAIL
THROUGH THE PERIOD AS THE REGION REMAINS ALONG THE WESTERN FRINGE
OF ATLANTIC HIGH PRESSURE CENTERED WELL OFFSHORE. WINDS WILL
GENERALLY AVERAGE 10-15 KT...POSSIBLY A BIT HIGHER AT NIGHT WITH
WEAK NOCTURNAL SURGING AND ALONG THE LAND/SEA INTERFACE WITH THE
AFTERNOON SEA BREEZE. SEAS WILL AVERAGE 2-4 FT. BOTH WINDS AND
SEAS LOOK TO REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS.

RIP CURRENTS...THE COMBINATION OF LINGERING LUNAR INFLUENCES...AN
EASTERLY SWELL OF 2 FT EVERY 8-9 SECONDS AND GUSTY WINDS WILL
SUPPORT A MODERATE RISK FOR RIP CURRENTS FOR THE LOWER SOUTH
CAROLINA BEACHES INTO THIS EVENING.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...
NEAR TERM...SPR
SHORT TERM...ST
LONG TERM...RJB
AVIATION...SPR/ST
MARINE...SPR/ST



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