Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 042235
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
635 PM EDT SAT JUL 4 2015

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL PREVAIL AS A TROUGH OF LOW PRESSURE
LINGERS INLAND THROUGH THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
A PERSISTENT MID LVL TROUGH OF LOW PRESSURE WILL EXTEND ACROSS
MUCH OF THE EASTERN CONUS WITH SHORTWAVE ENERGY THAT CONTINUES TO
ROUND ITS SOUTHERN BASE OVER PARTS OF THE DEEP SOUTH AND MID
ATLANTIC STATES. AT THE SFC...THE AREA WILL REMAIN BETWEEN A
PIEDMONT TROUGH INLAND AND HIGH PRESSURE CENTERED WELL OFFSHORE IN
THE WESTERN ATLANTIC. THE PATTERN WILL FAVOR DEEP MOISTURE WITHIN
A WEST/SOUTHWEST FLOW...CHARACTERIZED BY PWATS THAT APPROACH 2.0
INCHES.

THIS EVENING...SHOWERS AND THUNDERSTORMS WILL CONTINUE TO INTERACT
WITH A SEABREEZE IN SOUTHEAST GEORGIA FOR THE NEXT COUPLE HOURS. A
FEW OF THESE PULSE TYPE THUNDERSTORMS COULD BE STRONG OR SEVERE
UNTIL SUNSET...MAINLY IN COASTAL COUNTIES. THE PRIMARY THREAT WITH
THESE THUNDERSTORMS WILL BE DAMAGING WIND GUSTS GIVEN DCAPE VALUES
NEAR 800-1000 J/KG. FURTHER NORTH...THE SEVERE WEATHER WILL BE MORE
QUESTIONABLE...PARTICULARLY IN TRI-COUNTY AREA WHERE LCL AND LFC
HEIGHTS HAVE BECOME HIGHER. HOWEVER...WE CAN NOT COMPLETELY RULE OUT
A STRONGER THUNDERSTORM CAPABLE OF PRODUCING STRONG WIND GUSTS AHEAD
OF BROKEN LINE OF SHOWERS/THUNDERSTORMS THAT CONTINUE TO SHIFT
NORTHEAST TOWARD THE TRI-COUNTY AREA THIS EVENING...ESPECIALLY GIVEN
THE POSITION OF AN ENHANCED LOW-LVL WIND FIELD JUST TO OUR NORTH.

OVERNIGHT...THE THREAT OVER SEVERE WEATHER SHOULD DIMINISH ACROSS
ALL AREAS WITH THE LOSS OF DAYTIME HEATING WITHIN AN HOUR OF SUNSET.
HOWEVER...A SLIGHT CHANCE TO CHANCE OF SHOWERS/THUNDERSTORMS WILL
REMAIN IN THE FORECAST GIVEN SOME ONGOING UNSTABLE CONDITIONS.
GREATEST CHANCES OF SHOWERS/THUNDERSTORMS SHOULD OCCUR NEAR COASTAL
AREAS. LOW TEMPS WILL RANGE IN THE LOW TO MID 70S ACROSS THE AREA.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
OVERVIEW: THE PATTERN WILL BE CHARACTERIZED BY LONG WAVE TROUGHING
ACROSS THE EASTERN THIRD OF THE U.S. WITH THE SOUTHEAST STATES
POSITIONED ALONG THE WESTERN FRINGES OF ATLANTIC HIGH PRESSURE
CENTERED WELL OFFSHORE. DIURNAL CONVECTION IS LIKELY THROUGH THE
PERIOD WITH COVERAGE BEING DETERMINED BY THE POSITION OF THE UPPER
RIDGE CENTERED JUST OFFSHORE AND UPPER LEVEL LOW PRESSURE THAT
IS FORECAST TO DEVELOP OVER THE TENNESSEE VALLEY.

SATURDAY...SATURDAY LOOKS TO BE THE LEAST ACTIVE DAY THROUGH THE MID
RANGE WITH UPPER LEVEL RIDGING HOLDING FIRM. PWATS WILL REMAIN
ELEVATED AND JUXTAPOSED WITH SUFFICIENT INSTABILITY TO SUPPORT
ISOLATED TO SCATTERED SHOWERS/TSTMS MAINLY IN THE AFTERNOON AND
EVENING. THE HIGHER PROBABILITIES FOR MEASURABLE RAINFALL LOOKS TO
OCCUR ACROSS COASTAL GEORGIA WHERE CONVECTION COULD MOVE NORTHEAST
OUT OF NORTHERN FLORIDA AND FAR SOUTHEAST GEORGIA WHERE LOW-LEVEL
CONVERGENCE WILL BE ENHANCED BY A POSSIBLE MERGING OF THE ATLANTIC
AND GULF SEA BREEZE CIRCULATIONS. MESOSCALE BOUNDARY INTERACTIONS
ARE DIFFICULT TO PIN DOWN THIS FAR OUT...SO POPS OF 20-30 PERCENT
WILL BE MAINTAINED /HIGHEST ALONG THE GEORGIA COAST/...BUT LOCALLY
HIGHER POPS MAY EVENTUALLY BE NEEDED. THERE ARE SIGNALS THAT
CONVECTION COULD LINGER THROUGH THE NIGHT AS UPPER LEVEL RIDING
BEGINS TO BREAK DOWN...BUT DIMINISHING INSTABILITY SHOULD KEEP THIS
ACTIVITY FAIRLY ISOLATED EXCEPT OVER THE COASTAL WATERS WHERE
NOCTURNAL JETTING COULD SUPPORT MORE SCATTERED ACTIVITY. HIGHS WILL
RANGE FROM THE LOWER-MID 90S WITH OVERNIGHT LOWS IN THE LOWER-MID
70S.

SUNDAY...MODELS ARE SIMILAR IN THE DEPICTION OF AN UPPER LOW CUTTING
OFF OVER THE TENNESSEE VALLEY AS POTENT SHORTWAVE ENERGY CUTS OFF FROM
THE MAIN BELT OF THE WESTERLIES. SIMILARLY...THE PREVAILING UPPER
RIDGE IS FORECAST TO BREAKDOWN AND SHIFT EAST OFF THE SOUTHEAST U.S.
COAST. DEEP MOISTURE CHARACTERIZED BY PWATS NEAR 2 INCHES FUNNELED
BETWEEN THESE TWO FEATURES COUPLED WITH SUFFICIENT INSTABILITY AND
DPVA INDUCED BY WAVES OF PASSING VORTICITY WILL SUPPORT SCATTERED
SHOWERS/TSTMS FOR MUCH OF THE AREA. POPS AROUND 50 PERCENT LOOK
REASONABLE THIS FAR OUT...ALTHOUGH HIGHER POPS MAY EVENTUALLY BE
NEEDED. CONVECTION COULD VERY WELL LINGER WELL INTO THE OVERNIGHT
HOURS. HIGHS WILL WARM INTO THE LOWER 90S AWAY FROM THE COAST WITH
OVERNIGHT LOWS IN THE LOWER-MID 70S.

MONDAY...THE UPPER LOW IS FORECAST TO WEAKEN AND EJECT OUT OF THE
TENNESSEE VALLEY MONDAY AFTERNOON AS STRONGER SHORTWAVE ENERGY DIGS
INTO THE WESTERN GREAT LAKES. HOWEVER...LINGERING TROUGHING ACROSS
THE SOUTHEAST U.S. COUPLED WITH RICH MOISTURE WILL KEEP A RISK FOR
SCATTERED SHOWERS/TSTMS ACROSS THE REGION. HIGHS WILL TOP OUT AROUND
90 WITH LOWS IN THE LOWER-MID 70S.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
MEDIUM RANGE GUIDANCE IS IN FAIRLY GOOD AGREEMENT THROUGH MID WEEK
INDICATING MORE HIGH PRESSURE RIDGING. ANOTHER TROUGH COULD RETURN
LATE IN THE WEEK. SHOULD SEE LOW RAIN CHANCES THROUGH AT LEAST
THURSDAY...MAINLY EACH AFTERNOON/EVENING. TEMPERATURES WILL
GENERALLY BE NEAR NORMAL...WITH HIGHS IN THE LOWER TO MID 90S AND
LOWS IN THE LOWER TO MID 70S.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS ARE EXPECTED AT BOTH TERMINALS FOR THE NEXT COUPLE
HOURS. FLIGHT RESTRICTIONS WILL THEN BE POSSIBLE...STARTING AT THE
SAV TERMINAL AROUND 20Z AND AT THE CHS TERMINAL AROUND 21-22Z.
TEMPO MVFR GROUPS HAVE BEEN MAINTAINED AT BOTH TERMINALS...MAINLY
ASSOCIATED WITH SHOWER AND THUNDERSTORMS BETWEEN 20Z/21Z TO
00Z/01Z. GUSTY WINDS WILL ALSO BE POSSIBLE WITH THUNDERSTORMS THAT
IMPACT THE TERMINALS. EXPECT VFR CONDITIONS TO RETURN EARLY
TONIGHT AT BOTH TERMINALS...THEN PERSIST INTO AT LEAST LATE SUNDAY
MORNING HOURS.

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

&&

.MARINE...
THIS EVENING AND TONIGHT...CONDITIONS WILL SLOWLY IMPROVE OVER
THE COASTAL WATERS AS THE PRESSURE GRADIENT RELAXES BETWEEN
ATLANTIC HIGH PRESSURE CENTERED WELL OFFSHORE AND A TROUGH OF LOW
PRESSURE NORTHWEST OF THE AREA. SOUTH/SOUTHWEST WINDS WILL PREVAIL
WITH SPEEDS AROUND 15 KTS EARLY TONIGHT...BEFORE GENERALLY
BECOMING 10-15 KTS THROUGH THE REST OF TONIGHT. SEAS WILL SUBSIDE
A BIT AS WINDS DIMINISH OVER THE PERIOD...BUT OVERALL SHOULD RANGE
BETWEEN 2-4 FT...HIGHEST IN THE OUTER GEORGIA WATERS.

SATURDAY THROUGH WEDNESDAY...A PERSISTENT PATTERN FEATURING ATLANTIC
HIGH PRESSURE AND AN INLAND TROUGH OF LOW PRESSURE EXPECTED. A
TIGHTENED PRESSURE GRADIENT BETWEEN THESE FEATURES WILL MAINTAIN
ELEVATED WINDS/SEAS THROUGH THE PERIOD BUT CONDITIONS SHOULD LARGELY
REMAIN BELOW ADVISORY LEVELS. SEAS WILL BE 2-4 FEET ON AVERAGE...BUT
COULD REACH 5 FT AT TIMES MOSTLY BEYOND 20 NM.

RIP CURRENTS...THE COMBINATION OF LINGERING LUNAR INFLUENCES...AN
EASTERLY SWELL OF 2 FT EVERY 9 SECONDS AND GUSTY WINDS WILL SUPPORT
A MODERATE RISK FOR RIP CURRENTS FOR THE BEACHES OF CHARLESTON
COUNTY. ATTM IT APPEARS SLIGHTLY LOWER WINDS FROM EDISTO BEACH SOUTH
ALONG GEORGIA COAST WILL LIMIT THE RIP CURRENT RISK TO A HIGH-END
LOW CATEGORY.

&&

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

&&

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



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