310 
FXUS62 KCHS 290150
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
950 PM EDT THU AUG 28 2014

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL EXPAND WESTWARD OVER THE AREA LATE
THIS WEEK AND PERSIST INTO THE MIDDLE OF NEXT WEEK. A BACKDOOR
COLD FRONT WILL APPROACH LATE NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
THE 00Z KCHS RAOB DEPICTED AN UNUSUALLY DRY AIRMASS FOR LATE
AUGUST. UNDER CLEAR SKIES/WITH LIGHT WINDS THIS AIRMASS WILL
SUPPORT EXCELLENT RADIATIONAL COOLING. BY DAYBREAK...LOWS WILL
RANGE FROM THE MID 60S AT MOST INLAND LOCATIONS TO THE LOWER/MID
70S ON THE BEACHES.

SOME HIGH RESOLUTION GUIDANCE DEPICTS INLAND FOG DEVELOPMENT
OVERNIGHT. HOWEVER...AS OF LATE THURSDAY EVENING NOT CONVINCED
THAT COVERAGE/IMPACT OF ANY RADIATION FOG JUSTIFIES A MENTION
WITHIN PUBLIC FORECASTS. WILL CONTINUE TO ASSESS...PERHAPS 
WE WILL NEED TO ADD A MENTION OF PATCHY FOG LATER TONIGHT. 

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
A DEEP LAYERED RIDGE WILL SET UP SHOP ABOVE THE LOCAL AREA THROUGH 
THE SHORT TERM PERIOD. MEANWHILE AT THE SURFACE WE FIND AN ATLANTIC 
RIDGE AROUND 28-30 DEGREES NORTH FRIDAY...THAT BECOMES ABSORBED BY A 
STRONGER 1027 MB HIGH THAT PUSHES EAST/SE OFF NEW ENGLAND OVER THE 
WEEKEND. 

A PROMINENT SUBSIDENCE CAP AND THE CONTINUED LACK OF MOISTURE ON 
FRIDAY...WITH PWATS DOWN NEAR 2 STANDARD DEVIATIONS BELOW 
NORMAL...WILL MAINTAIN OUR CURRENT STRETCH OF RAIN-FREE WEATHER. WE 
CAN/T ENTIRELY RULE OUT SOMETHING SNEAKING IN FROM SOUTH OF THE 
ALTAMAHA RIVER LATE IN THE DAY...BUT POPS HAVE BEEN HELD TO 10 
PERCENT OR LESS. FRIDAY LOOKS TO BE THE LAST DAY WITH DEW POINTS 
GENERALLY LESS THAN 70 DEGREES...SO THE HUMIDITY STILL WON/T BE 
HARSH. TEMPS THOUGH WILL BE QUITE WARM...PEAKING IN THE LOWER OR 
MIDDLE 90S INLAND FROM THE INTRA-COASTAL AND WARMEST WEST OF THE 
I-95 CORRIDOR.

MOISTURE WILL STEADILY BE ON THE INCREASE BOTH SATURDAY AND 
SUNDAY...AND THE THERMODYNAMIC ENVIRONMENT WILL BECOME MORE 
TYPICALLY UNSTABLE AS A RESULT. WITH A MID LEVEL 5930-5940 METER 
ANTICYCLONE OVERHEAD THROUGH THE PERIOD THERE IS NOT REALLY MUCH
TRIGGERING MECHANISM OTHER THAN THE SEA BREEZE ON SATURDAY...AND
THE SEA BREEZE AND MAYBE A LEE SIDE TROUGH ON SUNDAY. THUS WE ARE
RELUCTANT TO CARRY ANY COVERAGE OF SHOWERS AND T-STORMS GREATER
THAN ISOLATED TO SCATTERED...HIGHEST OVER THE WEST/SW SECTIONS
WHERE ANY BOUNDARY INTERACTIONS MAY OCCUR. STORM MOTION IS FAIRLY
NON-EXISTENT SATURDAY AND NO MORE THAN 5-10 KT SUNDAY...AND WHEN
COMBINED WITH PWATS BACK UP NEAR NORMAL SATURDAY AND APPROACHING 2
STANDARD DEVIATIONS ABOVE NORMAL SUNDAY SUPPORTS A RISK FOR
LOCALLY HEAVY RAINS. MAX TEMPS BOTH DAYS PRIOR TO ANY RAINFALL
WILL HIT THE LOWER AND MIDDLE 90S INLAND AND THE MID OR UPPER 80S
AT THE BEACHES DUE TO A SYNOPTIC ONSHORE FETCH AND THE SEA BREEZE.
WHEN COMBINED WITH DEW POINTS UP NEAR OR GREATER THAN 70 BOTH
DAYS...THE STICKY CONDITIONS WILL HAVE RETURNED.

CONDENSATION PRESSURE DEFICITS ARE MORE CONDUCIVE FOR THE 
DEVELOPMENT OF LATE NIGHT/EARLY MORNING FOG SATURDAY THROUGH 
SUNDAY...ESPECIALLY INLAND. HOWEVER...GIVEN THE LACK OF RECENT RAINS 
AND MANY LOCATIONS STRUGGLING TO REACH THEIR CROSS-OVER TEMPS WE 
HAVE NOT YET ADDED ANY MENTION IN THE GRIDDED FORECAST.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
MEDIUM RANGE GUIDANCE IN PRETTY DECENT AGREEMENT SHOWING THE RIDGING 
OVER THE REGION WEAKENING SLIGHTLY TOWARD MID WEEK AS A WEAKENING 
COLD FRONT APPROACHES FROM THE NORTH. BY THURSDAY A BIT MORE 
MOISTURE AND THIS WEAK FRONTAL BOUNDARY COULD LEAD TO SLIGHTLY 
GREATER RAIN CHANCES. TEMPERATURES WILL REMAIN SLIGHTLY ABOVE 
NORMAL.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
VFR THROUGH FRIDAY. THE PROBABILITY FOR PATCHY GROUND FOG WILL
INCREASE LATE TONIGHT/AROUND DAYBREAK FRIDAY...BUT THE CHANCE FOR
FLIGHT RESTRICTIONS REMAINS TOO LOW TO INCLUDE WITHIN 00Z TAFS. 

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS THE VAST MAJORITY OF THE 
PERIOD. LOW END PROBABILITIES OF DIRECT HITS FROM ISOLATED SHRA/TSRA 
SATURDAY THROUGH TUESDAY...WITH LOW TO MODERATE POTENTIAL FOR 
SUB-VFR WEATHER IN FOG AROUND DAYBREAK SUNDAY THROUGH TUESDAY.

&&

.MARINE...
A WEAK PRESSURE PATTERN ON THE PERIPHERY OF ATLANTIC HIGH PRESSURE
SHOULD HOLD WINDS BELOW 15 KT OVERNIGHT. INITIAL WIND DIRECTION
WILL RANGE FROM S/SW ACROSS SC WATERS TO E/SE ACROSS GA WATERS. 
WINDS WILL VEER WITH TIME...AND BY DAYBREAK THE LAND BREEZE WILL
CONTRIBUTE TO W/SW MAINLY 10 KT OR LESS. SEAS WILL RANGE FROM 1-3
FT WITHIN NEARSHORE WATERS TO 3-4 FT BEYOND 20 NM. SEA STATE WILL
BE DOMINATED BY A 9-10 SECOND PERIOD SWELL. 

FRIDAY THROUGH TUESDAY...OVERALL...THE CONDITIONS ACROSS THE
MARINE LOCALES WILL BE RATHER NON-EVENTFUL AND UNDER THE INFLUENCE
OF ATLANTIC HIGH PRESSURE. WEAK OFFSHORE WINDS EARLY FRIDAY WILL
THEN BE FOLLOWED BY LIGHT TO OCCASIONALLY MODERATE ONSHORE WINDS
THE BALANCE OF THE VALID PERIOD...WITH SEAS ON AVERAGE NO MORE
THAN 2 TO 3 FT. EVENTUALLY A FEW SHOWERS AND THUNDERSTORMS WILL
DEVELOP DURING THE HOLIDAY WEEKEND AND INTO EARLY NEXT WEEK...BUT
AREAL COVERAGE WILL BE LIMITED.

&&

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

&&

$$

NEAR TERM...SPR
SHORT TERM...
LONG TERM...RJB
AVIATION...SPR
MARINE...SPR