000
FXUS62 KCHS 160228
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1028 PM EDT WED MAY 15 2013

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL EXTEND ACROSS THE REGION THIS WEEK.
RAIN CHANCES WILL INCREASE OVER THE WEEKEND AS UPPER LEVEL ENERGY
MOVES OVER THE AREA...WITH A COLD FRONT APPROACHING FROM THE WEST
BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
AN UPPER LEVEL RIDGE WILL PREVAIL OVER THE REGION TONIGHT.
MEANWHILE AT THE SURFACE...ATLANTIC HIGH PRESSURE WILL EXPAND
FARTHER ACROSS THE FLORIDA PENINSULA AND GEORGIA AS A WEAK TROUGH
LINGERS INLAND. THE GRADIENT BETWEEN THESE TWO SURFACE FEATURES
COULD PREVENT WINDS FROM FULLY DECOUPLING OVER PARTS OF SOUTHEAST
SOUTH CAROLINA TONIGHT...ESPECIALLY THE CHARLESTON TRI-COUNTY
AREA. CLEAR SKIES SHOULD GIVE WAY TO INCREASING HIGH CIRRUS FROM
THE WEST OVERNIGHT AS THE NOSE OF AN H25 JET PUSHES TOWARD THE
REGION. GIVEN THESE FACTORS...TEMPERATURES WILL BE SLOW TO FALL
THIS EVENING...WITH GOOD RADIATIONAL COOLING BRIEFLY SETTING UP
OVERNIGHT BEFORE HIGH CLOUDS EXPAND LATE. OVERALL...EXPECT LOW
TEMPERATURES IN THE LOWER TO MID 60S ACROSS MUCH OF THE AREA.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
THURSDAY...FAIRLY QUIET WEATHER DAY EXPECTED ON THURSDAY. SURFACE
HIGH PRESSURE WILL REMAIN OFF THE SOUTHEAST COAST...WITH A WEAK
TROUGH INLAND. ALOFT...A BROAD UPPER TROUGH WILL APPROACH FROM THE
WEST...WITH ASSOCIATED VORT ENERGY FORECAST TO CROSS THROUGH THE
AREA. THIS WILL MAINLY RESULT IN AN INCREASE IN MID AND HIGH LEVEL
CLOUDS AS MODELS REMAIN CONSISTENT IN KEEPING THE FORECAST AREA
PRECIP-FREE. DESPITE INCREASING CLOUD COVER...THICKNESS VALUES ONCE
AGAIN SUPPORT HIGH TEMPS A FEW DEGREES ABOVE NORMAL...IN THE MIDDLE
AND UPPER 80S. LOWS WILL BE IN THE LOWER AND MIDDLE 60S.

FRIDAY...THE INLAND SURFACE TROUGH WILL BECOME LESS DEFINED...AND
THE FORECAST AREA WILL BE MAINLY UNDER THE INFLUENCE OF HIGH
PRESSURE OFFSHORE. MODELS CONTINUE TO HINT AT POSSIBLE CONVECTION
FIRING OFF THE SEA BREEZE IN THE AFTERNOON...WITH BEST CHANCES AWAY
FROM THE COAST. NO MORE THAN LOW END SLIGHT CHANCES ARE WARRANTED AT
THIS TIME AS COVERAGE SHOULD REMAIN ISOLATED. POPS WILL DIMINISH
AFTER SUNSET WITH LOSS OF INSOLATION.

SATURDAY...A WEAK PRESSURE PATTERN WILL BE IN PLACE...BOTH ALOFT AND
AT THE SURFACE WITH SOME UPPER LEVEL ENERGY STILL APPARENT. MODELS
ARE BIT MORE AGGRESSIVE SHOWING DIURNALLY DRIVEN PRECIP DEVELOPING
ONCE AGAIN IN THE AFTERNOON....THUS HAVE MAINTAINED CHANCE POPS
INLAND AND SLIGHT CHANCE POPS ALONG THE COAST. CONVECTIVE PARAMETERS
CURRENTLY ARE NOT ALL THAT IMPRESSIVE WITH WEAK MID LEVEL LAPSE
RATES AND WEAK SHEAR...SO SEVERE POTENTIAL IS LOW.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
WEAK UPPER LEVEL RIDGING WILL PREVAIL ACROSS THE SOUTHEAST STATES
INTO EARLY NEXT WEEK...DEFLECTING A PROGRESSIVE SHORTWAVE TO THE
NORTHWEST SUNDAY INTO MONDAY. ATLANTIC HIGH PRESSURE WILL CONTINUE
TO BE THE MAIN FEATURE AT THE SURFACE...AND WITH LITTLE CHANGE IN
THE PATTERN UNTIL AS LATE AS WEDNESDAY...EXPECT SHOWER/THUNDERSTORM
POTENTIAL TO MAINLY BE DRIVEN BY TYPICAL DIURNAL HEATING/INSTABILITY
AND SEABREEZE FORCING. WILL THUS CONTINUE TO ADVERTISE ISOLATED TO
SCATTERED THUNDERSTORM DEVELOPMENT SUNDAY THROUGH WEDNESDAY DURING
THE CLIMATOLOGICALLY FAVORED AFTERNOON AND EARLY EVENING HOURS.
HIGH TEMPERATURES EACH AFTERNOON WILL RISE INTO THE UPPER 80S
INLAND...TO THE LOW 80S RIGHT ALONG THE COAST BEHIND THE
SEABREEZE. THE NEXT MAJOR SYNOPTIC FEATURE WILL BE AN UPPER TROUGH
AND ASSOCIATED COLD FRONT APPROACHING FROM THE WEST BY LATE TUESDAY
INTO WEDNESDAY.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS WILL PREVAIL AT KCHS AND KSAV THROUGH 00Z FRIDAY.

EXTENDED AVIATION OUTLOOK...VFR. ISOLATED DIURNAL CONVECTION IS
POSSIBLE OVER THE WEEKEND.

&&

.MARINE...
TONIGHT...AN ENHANCED SURFACE PRESSURE GRADIENT BETWEEN ATLANTIC
HIGH PRESSURE AND A TROUGH OF LOW PRESSURE INLAND...IN COMBINATION
WITH WEAK LOW LEVEL JETTING...WILL KEEP SOUTH-SOUTHWEST WINDS ELEVATED
IN THE 15-20 KT RANGE INTO THE EARLY OVERNIGHT HOURS. AS THE HIGH
EXPANDS TO THE SOUTH AND THE GRADIENT WEAKENS LATE TONIGHT...SOUTHWEST
WINDS WILL BEGIN TO DIMINISH. SEAS WILL GENERALLY RANGE FROM 2-4 FT.

THURSDAY THROUGH MONDAY...ON THURSDAY SURFACE HIGH PRESSURE WILL
REMAIN CENTERED OFFSHORE EAST OF THE WATERS WITH A TROUGH INLAND.
INITIALLY THERE WILL BE SOME RESULTANT SURGE BETWEEN THE TWO WITH
WIND SPEEDS 15-20 KT POSSIBLE...MAINLY OVER THE SC WATERS. THE
TROUGH WILL GRADUALLY BECOME LESS DEFINED THURSDAY NIGHT AND ALLOW
FOR QUIET MARINE CONDITIONS TO RETURN. OVERALL SUB-SCA CRITERIA WILL
PREVAIL THROUGH THE WEEKEND...WITH WINDS GENERALLY 10-15 KT AND SEAS
2-3 FEET...HIGHEST OVER THE OUTER WATERS.

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...JAQ
SHORT TERM...ECT
LONG TERM...WMS
AVIATION...JAQ
MARINE...JAQ/ECT