Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 041754
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
154 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 /THROUGH TONIGHT/...
THIS AFTERNOON...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.

LATEST RADAR MOSAICS INDICATE NUMEROUS SHOWERS AND THUNDERSTORMS
OVER PARTS OF SOUTH/CENTRAL GEORGIA WHERE THE ATMOSPHERE HAS BECOME
QUITE UNSTABLE SOUTH OF AN OUTFLOW BOUNDARY CREATED BY PREVIOUS
CONVECTION TO THE NORTH EARLIER TODAY. ADDITIONAL SHOWERS AND
THUNDERSTORMS WILL LIKELY DEVELOP OVER CENTRAL GEORGIA AND GRADUALLY
TRACK EAST/NORTHEAST WITHIN A WEST/SOUTHWEST FLOW. A FEW OF THESE
PULSE TYPE THUNDERSTORMS COULD BECOME STRONG OR SEVERE AS THEY CROSS
OVER OR NEAR THE OUTFLOW BOUNDARY IN PLACE AHEAD OF THEM.

LATEST MESOSCALE ANALYSIS INDICATES A HIGHLY UNSTABLE ATMOSPHERE
AHEAD OF THESE THUNDERSTORMS...WITH SBCAPES APPROACHING 3500 TO
4000 J/KG ACROSS OVER MUCH OF SOUTHEAST GEORGIA. THIS AMOUNT OF
ENERGY ALONG WITH DCAPE VALUES NEAR 1000 J/KG AND INVERTED-V
SOUNDINGS SUGGEST SOME THUNDERSTORMS COULD BECOME STRONG OR SEVERE
WITH DAMAGING WIND GUSTS BEING THE PRIMARY CONCERN. AS ACTIVITY
SLOWLY TRACKS EAST/NORTHEAST INTO SOUTHEAST SOUTH CAROLINA LATE
AFTERNOON INTO EARLY EVENING HOURS...THERE WILL STILL BE A THREAT
FOR SEVERE WEATHER IN THE FORM OF DAMAGING WIND GUSTS...ESPECIALLY
SINCE THERE WILL BE STRONGER SHEAR ASSOCIATED WITH A 30-40 KT LOW
LVL JET. HOWEVER...CLOUD COVER COULD BE AN ISSUE FOR FURTHER
DESTABILIZATION OVER THE TRI-COUNTY AREA LATER THIS AFTERNOON AND
EVENING. OTHER THAN THE NOTED SCENARIO ABOVE...A FEW SHOWERS
AND/OR THUNDERSTORM COULD DEVELOP ALONG A SEABREEZE THIS
AFTERNOON...BEFORE THE BULK OF PRECIP ARRIVES FROM THE WEST. OVERALL
HIGH TEMPS SHOULD RANGE IN THE UPPER 80S TO LOWER 90S AWAY FROM
THE COAST...HIGHEST IN SOUTHEAST GEORGIA WHERE SFC HEATING IS
STRONGEST.

LATE THIS EVENING AND OVERNIGHT...THE UPPER RIDGE MAY BEGIN TO BREAK
DOWN A BIT...WITH THE LOWERING HEIGHTS AND SOME PASSING UPPER LEVEL
SHORT WAVE DISTURBANCES SUPPORTING LOW CHANCES OF SHOWERS AND
THUNDERSTORMS...WITH THE GREATEST COVERAGE NEAR THE COAST. LOWS
SHOULD BE IN THE LOWER TO MID 70S ACROSS THE AREA.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
GENERALLY A CONTINUATION OF THE SAME PATTERN WITH HIGH PRESSURE OVER
THE ATLANTIC AND LOW PRESSURE INLAND. THE MAIN CHALLENGE IS TIMING
OF SHORTWAVE TROUGHS ALOFT WHICH WILL BE THE MAIN FORCING FOR
CONVECTION.

SUNDAY...CLOSE PROXIMITY TO THE UPPER TROUGH ALONG WITH DEEP
MOISTURE WILL MEAN ABOVE NORMAL RAIN CHANCES...HIGHEST INLAND CLOSER
TO POSSIBLE ORGANIZED CONVECTION UPSTREAM. HIGH TEMPERATURES IN THE
LOWER 90S...MAINLY NEAR AND WEST OF I-95. SOME SHOWERS AND STORMS
WILL LINGER INTO SUNDAY NIGHT WITH LOWS MAINLY IN THE LOWER TO MID
70S.

MONDAY...SCATTERED TO POSSIBLY NUMEROUS SHOWERS AND THUNDERSTORMS
EXPECTED AGAIN WITH ABUNDANT CLOUDS LIKELY HELPING KEEP TEMPERATURES
SLIGHTLY BELOW NORMAL CLOSER TO 90. SEVERE RISK APPEARS LOW GIVEN
REDUCED INSTABILITY/SHEAR.

TUESDAY...SCATTERED CONVECTION AGAIN ALTHOUGH PROBABLY NOT QUITE AS
MUCH AS THE UPPER TROUGH WEAKENS AND HIGH PRESSURE EXERTS MORE
INFLUENCE. HIGHS A BIT WARMER CLOSER TO NORMAL IN THE LOWER 90S AWAY
FROM THE LOCALLY COOLER COASTAL AREAS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
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 /18Z SATURDAY 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 THE CHS 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 AFTERNOON...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 UP TO 15 KTS THROUGH 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.

SUNDAY THROUGH THURSDAY...EXPECT A PERSISTENT PATTERN FEATURING
ATLANTIC HIGH PRESSURE AND AN INLAND TROUGH OF LOW PRESSURE. 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 LOWER SOUTH
CAROLINA BEACHES TODAY. IT APPEARS SLIGHTLY LOWER WINDS FROM
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...RJB
LONG TERM...RJB
AVIATION...DPB/RJB
MARINE...DPB/RJB



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