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Area Forecast Discussion

470
FXUS62 KCHS 031521
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1121 AM EDT FRI JUL 3 2015

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

&&

.NEAR TERM /THROUGH TONIGHT/...
STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE EARLY THIS AFTERNOON
INTO EARLY EVENING FOR SOUTHEAST SOUTH CAROLINA AND SOUTHEAST
GEORGIA. A SEVERE THUNDERSTORM WATCH IS NOW IN EFFECT FOR ALL AREAS
UNTIL 6 PM THIS EVENING.

TODAY...A BROAD MID LVL TROUGH OF LOW PRESSURE WILL EXTEND ACROSS
REMAIN MUCH OF THE EASTERN CONUS WITH SHORTWAVE ACTIVITY THAT ROUNDS
ITS SOUTHERN BASE OVER THE SOUTHEAST AND MID ATLANTIC STATES. AT THE
SFC...THE AREA WILL REMAIN BETWEEN A PIEDMONT TROUGH INLAND AND HIGH
PRESSURE OVER THE WESTERN ATLANTIC. THE SETUP WILL FAVOR A PERIOD OF
SHOWERS AND THUNDERSTORMS OVER SOUTHEAST SOUTH CAROLINA AND
SOUTHEAST GEORGIA EARLY THIS AFTERNOON INTO EARLY EVENING HOURS.
SOME OF THESE THUNDERSTORMS COULD BE STRONG OR SEVERE...IN THE FORM
OF A LINE CURRENTLY DEPICTED ON RADAR IMAGERY OVER CENTRAL GEORGIA.

SOME QUESTIONS REMAIN IN REGARDS TO HOW WELL NORTHERN AREAS IN
SOUTHEAST SOUTH CAROLINA WILL REBOUND FROM PREVIOUS CONVECTION
EARLIER THIS MORNING...BUT MODEL CONSENSUS INDICATES THAT AT LEAST
PARTIAL BOUNDARY LAYER RECOVERY WILL OCCUR AHEAD OF A 30-40 KT LOW
LVL JET SHIFTING INTO THE REGION THIS AFTERNOON. THIS SEEMS
PLAUSIBLE GIVEN POCKETS OF SUN NOW REACHING THE SFC IN THE TRI-
COUNTY AREA. SBCAPES RANGING BETWEEN 1500-2000 J/KG ALONG WITH
FORCING FROM THE LOW LVL JET AND H5 SHORTWAVE CURRENTLY POSITIONED
TO OUR NORTH/NORTHWEST...SHOULD FAVOR A ROUND OF ENHANCED CONVECTION
IN THE FORM OF LINE...AS CURRENTLY SEEN VIA RADAR IMAGERY TO OUR
WEST. THE MAIN THREAT ASSOCIATED WITH THUNDERSTORMS THAT ENTER
NORTHERN AREAS THIS AFTERNOON WILL BE DAMAGING WIND GUSTS. GIVEN
AMPLE SHEAR/HELICITY AN ISOLATED TORNADO CAN NOT BE RULED OUT AS
WELL. FURTHER SOUTH...STRONG SFC HEATING WILL OCCUR UNDER MOSTLY
SUNNY TO CLEAR SKIES. AS A RESULT...SBCAPES WILL LIKELY APPROACH
2000-3000 J/KG. HOWEVER...SHEAR WILL NOT BE AS STRONG GIVEN THE
POSITION OF THE LOW LVL JET TO THE NORTH. GIVEN THE SETUP...THE
PRIMARY CONCERN WITH THUNDERSTORMS OVER SOUTHEAST GEORGIA WILL BE
DAMAGING WIND GUSTS...ESPECIALLY AS DCAPES APPROACH AT OR ABOVE 1000
J/KG THIS AFTERNOON.

OVERALL HIGH TEMPS WILL RANGE IN THE LOWER 90S FOR MOST AREAS IN
SOUTHEAST GEORGIA...BUT SHOULD BE A DEGREE OR TWO COOLER IN
SOUTHEAST SOUTH CAROLINA DUE TO CLOUD COVER.

LATE THIS EVENING AND OVERNIGHT...SOME LINGERING SHOWERS AND
POSSIBLY A FEW THUNDERSTORMS WILL PERSIST...ESPECIALLY NORTH OF
INTERSTATE 16...BEFORE DIMINISHING IN COVERAGE LATE. LOW
TEMPERATURES ARE GENERALLY EXPECTED TO BE IN THE LOWER TO MID 70S.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
GENERALLY THE SAME PATTERN OF OFFSHORE HIGH PRESSURE AND INLAND LOW
PRESSURE TO PERSIST THROUGH THE PERIOD WITH THE TIMING OF UPPER
SHORTWAVES BEING KEY TO RAIN CHANCES.

SATURDAY...INCREASED HIGH PRESSURE RIDGING FROM THE EAST SHOULD KEEP
SHOWER/THUNDERSTORM COVERAGE LOWER THAN PREVIOUS DAYS...WITH THE
HIGHEST CHANCES LIKELY COMING LATER IN THE DAY INTO SATURDAY NIGHT
AS THE UPPER TROUGH AND DEEPER MOISTURE AFFECT THE AREA. HIGHS
LIKELY AT OR JUST ABOVE NORMAL IN THE LOWER TO MID 90S.

SUNDAY...SHOULD BE BETTER RAIN COVERAGE WITH THE UPPER TROUGH A BIT
CLOSER. SEVERE RISK APPEARS LOW OVERALL BUT WILL HAVE TO WATCH HOW
ORGANIZED UPSTREAM CONVECTION BECOMES AS IT PUSHES EAST TOWARD THE
COAST. HIGHS LIKELY SLIGHTLY BELOW NORMAL. SOME SHOWERS AND STORMS
WILL LINGER INTO SUNDAY NIGHT.

MONDAY...SCATTERED TO POSSIBLY NUMEROUS SHOWERS AND THUNDERSTORMS
EXPECTED AGAIN WITH ABUNDANT CLOUDS LIKELY HELPING KEEP
TEMPERATURES SLIGHTLY BELOW NORMAL.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
MEDIUM RANGE GUIDANCE IS IN FAIRLY GOOD AGREEMENT THROUGH MID WEEK
INDICATING THE UPPER TROUGH OVER THE EAST COAST WILL BREAK DOWN AND
GIVE WAY TO HIGH PRESSURE. THIS PATTERN WILL FAVOR CHANCES OF MAINLY
DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS EACH DAY...WITH THE
GREATEST COVERAGE LIKELY TUESDAY. TEMPERATURES WILL GENERALLY BE
NEAR NORMAL...WITH HIGHS IN THE LOWER TO MID 90S AND LOWS IN THE
LOWER TO MID 70S.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
KCHS...SCATTERED SHOWERS ASSOCIATED WITH AN UPPER LEVEL DISTURBANCE
COULD AFFECT THE TERMINAL THROUGH ABOUT 16Z...THUS HAVE ADDED A
TEMPO GROUP FOR LIGHT SHOWERS DURING THAT PERIOD. AN EMBEDDED THUNDERSTORM
IS CERTAINLY POSSIBLE AS WELL BUT CONFIDENCE IS NOT HIGH ENOUGH TO
INCLUDE MENTION AT THIS TIME AS STORMS HAVE GENERALLY BEEN
WEAKENING AS THEY APPROACH THE TERMINAL. THEN...CONFIDENCE IS
INCREASING THAT STRONGER CONVECTION COULD IMPACT THE TERMINAL LATE
THIS AFTERNOON INTO EARLY THIS EVENING AND THE FORECAST HAS A
TEMPO GROUP FOR THUNDERSTORMS FROM 20-24Z WITH FLIGHT
RESTRICTIONS AND GUSTY WINDS LIKELY TO ACCOMPANY ANY
THUNDERSTORMS. LINGERING SHOWERS ARE THEN EXPECTED THROUGH MUCH OF
THE EVENING.

KSAV...VFR CONDITIONS ARE GENERALLY EXPECTED TO PREVAIL. CONVECTION
LATER THIS AFTERNOON AND EARLY THIS EVENING IS EXPECTED TO
PRIMARILY REMAIN NORTH OF THE TERMINAL SO HAVE NO MENTION IN THE
FORECAST...BUT THIS WILL NEED TO BE REEVALUATED WITH EACH FORECAST
UPDATE AS TRENDS BECOME MORE APPARENT. IF ANY THUNDERSTORMS WERE
TO OCCUR...IT WOULD MOST LIKELY BE IN THE 20-24Z TIME FRAME AND
BRIEF FLIGHT RESTRICTIONS WOULD BE POSSIBLE.

EXTENDED AVIATION OUTLOOK...BRIEF FLIGHT RESTRICTIONS ARE
POSSIBLE IN MAINLY AFTERNOON/EARLY EVENING SHOWERS AND
THUNDERSTORMS...WITH THE BEST CHANCES BEGINNING SUNDAY.
OTHERWISE...VFR CONDITIONS ARE EXPECTED TO PREVAIL.

&&

.MARINE...
TODAY AND TONIGHT...THE SURFACE PRESSURE GRADIENT WILL TIGHTEN
BETWEEN A PIEDMONT TROUGH NORTHWEST OF THE AREA AND HIGH PRESSURE
OVER THE WESTERN ATLANTIC. STRONG WIND FIELDS ALOFT WILL SUPPORT
WINDS UPWARDS OF 15-20 KT OVER MUCH OF THE WATERS THIS AFTERNOON
INTO TONIGHT...ESPECIALLY AS NOCTURNAL JETTING DEVELOPS. A SMALL
CRAFT ADVISORY WILL REMAIN IN EFFECT BEGINNING MID-AFTERNOON FOR
CHARLESTON HARBOR AND THE CHARLESTON COUNTY COASTAL WATERS...THEN
FOR THE OUTER GEORGIA WATERS EARLY THIS EVENING AS FREQUENT GUSTS
TO 25 KT ARE EXPECTED TO DEVELOP OVER THESE WATERS. WINDS SHOULD
DIMINISH IN THE HARBOR DURING THE EVENING...THEN LATE TONIGHT OVER
THE COASTAL WATERS. SEAS WILL BUILD AS HIGH AS 3-5 FT...HIGHEST
OVER 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...ELEVATED S/SW WINDS AND ASTRONOMICAL FACTORS WILL
RESULT IN A MODERATE RISK FOR RIP CURRENTS ALONG THE LOWER SOUTH
CAROLINA COAST TODAY. AN ELEVATED RISK FOR RIP CURRENTS COULD
THEN PERSIST INTO THE FOURTH OF JULY WEEKEND.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 8 PM EDT THIS
     EVENING FOR AMZ330.
     SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 5 AM EDT
     SATURDAY FOR AMZ374.
     SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 5 AM EDT
     SATURDAY FOR AMZ350.

&&

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



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