000
FXUS62 KCHS 040608
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
208 AM EDT SAT SEP 4 2010

.SYNOPSIS...
A COLD FRONT WILL APPROACH THE AREA OVERNIGHT AND PUSH INTO THE
REGION SATURDAY...THEN WILL STALL OVER OR NEARBY INTO EARLY NEXT
WEEK. HIGH PRESSURE WILL BUILD NORTH OF THE FRONT AND WILL THEN
SETTLE SOUTH INTO THE REGION FOR THE MIDDLE AND LATTER PART OF
NEXT WEEK.

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
QUIET CONDITIONS CONTINUE EARLY THIS MORNING...WITH JUST A FEW
SWATHS OF HIGH LEVEL CLOUDS STREAMING INTO THE FORECAST AREA FROM
THE SOUTHWEST. ANY CLOUD COVER SHOULD REMAIN SCATTERED. AHEAD OF
AN APPROACHING COLD FRONT...THE SURFACE PRESSURE GRADIENT WILL
SUPPORT PERSISTENT SOUTHWEST WINDS...HOLDING TEMPERATURES UP
OVERNIGHT.

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY/...
SATURDAY...A COLD FRONT WILL APPROACH DURING THE DAY...BUT AS IT
BECOMES PARALLEL TO THE DEEP WESTERLY FLOW THROUGHOUT THE ATMOSPHERE
IT WILL STRUGGLE TO PUSH OFF THE COAST. ALTHOUGH WE DO SEE AN
INCREASE IN PWATS OF 1.5 TO 1.75 INCHES IN ASSOCIATION WITH THE
FRONT DURING THE PEAK AFTERNOON HEATING...MUCH OF THAT MOISTURE IS
CONFINED TO THE LOWEST 5-10 KFT. WITH ONLY LIMITED LOW LEVEL
CONVERGENCE TO RESULT...THE PROSPECTS FOR PRECIP LOOKS SPARSE.
WHILE WE WILL SEE SOME INTERACTION OF THE SEA BREEZE AND THE FRONT
LATE ACROSS FAR SE GA...RAIN PROBABILITIES ARE NOT SUFFICIENT
ENOUGH TO MENTION IN THE FORECAST. THUS WE WILL MAINTAIN RAINFREE
CONDITIONS OVER LAND...BUT SHOW POPS AS HIGH AS 12 PERCENT OVER
THE GA COASTAL ZONES WHERE FRONT AND SEA BREEZE MIGHT PROVIDE
ENOUGH LIFT TO SPUR A FEW SHOWERS. WHILE THE LOW LEVEL THICKNESS
INDICATES 1420-1424M...OR A BIT LOWER THAN TODAY...WITH SIMILAR
850 MB TEMPS NEAR 17 OR 18C AND COMPRESSIONAL HEATING AHEAD OF THE
FRONT...WE LOOK FOR AFTERNOON MAX TEMPS TO TOP OUT IN THE LOWER
90S MOST PLACES AWAY FROM THE SHORELINE. SOME MID 90S WILL OCCUR
OVER INLAND MCINTOSH AND LONG COUNTIES...WHILE SEA BREEZE
CIRCULATIONS HOLD READINGS DOWN IN THE MID AND UPPER 80S AT THE
BEACHES.

SATURDAY NIGHT THROUGH MONDAY...THE COLD FRONT WILL STALL OVER OR
NEAR THE LOCAL AREA AS HIGH PRESSURE BUILDS FROM THE OH/TN VALLEYS
SATURDAY NIGHT...TO THE MID ATLANTIC STATES SUNDAY...THEN INTO THE
ATLANTIC MONDAY. WESTERLY FLOW ALOFT WILL BACK TO THE SW DURING THIS
TIME AS THE LOW AND MIDDLE LEVEL RIDGE GRADUALLY BUILDS BACK IN FROM
THE SW ATLANTIC BY EARLY NEXT WEEK. AT THE SAME TIME...OCCASIONAL
SHORT WAVES ALOFT WILL SKIRT THE AREA FROM THE GULF OF MEXICO...WE
WILL BE IN THE RIGHT REAR QUAD OF THE UPPER LEVEL JET FOR A PART OF
THE TIME...AND WITH THE FRONT IN THE VICINITY WE MIGHT FINALLY SEE
THE RETURN OF SOME PRECIP TO THE FORECAST AREA. HOWEVER...THE AMOUNT
OF MOISTURE WILL BE IN QUESTION. FOR NOW WE WILL MAINTAIN CONTINUITY
OF THE PREVIOUS FORECAST AND SHOW 14 PERCENT POPS OVER LAND...AND
SLIGHT CHANCE POPS OVER THE COASTAL WATERS LATE THIS WEEKEND INTO
EARLY NEXT WEEK WHERE BEST LOW LEVEL THETA-E AIR RESIDES. BUT KEEP
IN MIND IF WE SEE ENOUGH AVAILABLE MOISTURE...WITH ONSHORE LOW LEVEL
FLOW SOME COASTAL SHOWERS CERTAINLY COULD MOVE ONSHORE. TEMPS
SATURDAY NIGHT WILL RANGE FROM THE LOWER 60S ALONG OUR NW TIER WHERE
THE DRIEST AIR RESIDES...WHILE COASTAL LOCATIONS WILL BE HELD ABOUT
10-12 DEGREES HIGHER. FOR SUNDAY AND MONDAY...MAX TEMPS ARE DRIVEN
BY AMOUNT OF INSOLATION...AS WE EXPECT AT LEAST PARTIAL CLOUDINESS
WITH THE NEARBY FRONT. FOR NOW WE WILL CARRY TEMPS WITHIN A FEW
DEGREES OF 90 BOTH DAYS...PROVIDED THAT THERE IS ENOUGH SUNSHINE.
COASTAL LOCATIONS WILL HOLD IN THE MIDDLE 80S WITH ONSHORE FLOW AND
SEA BREEZE CIRCULATIONS BOTH AFTERNOONS.

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
MEDIUM RANGE GUIDANCE IS IN GOOD AGREEMENT BUILDING DEEP LAYER
RIDGING BACK OVER THE SOUTHEAST STATES THROUGH THE PERIOD. CAN/T
RULE OUT AN ISOLATED SHOWER DRIFTING IN OFF THE ATLANTIC...PARTICULARLY
ACROSS SOUTHEAST GEORGIA MONDAY NIGHT THROUGH TUESDAY NIGHT BEFORE
THE LOW LEVEL NORTHEAST FLOW WEAKENS AS HIGH PRESSURE BUILDS OVER
THE REGION...BUT PROBABILITIES APPEAR TOO LOW TO MENTION IN THE
FORECAST AT THIS TIME. THEREFORE...WILL KEEP THE FORECAST RAIN
FREE THROUGHOUT THE LONG TERM PERIOD. TEMPERATURES ARE EXPECTED TO
RUN SLIGHTLY ABOVE NORMAL LEVELS.

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR CONDITIONS WILL CONTINUE AT BOTH TERMINALS THROUGH EARLY
SUNDAY MORNING. A DRY COLD FRONT WILL DROP INTO THE REGION TODAY.
WIND DIRECTIONS WILL BE SOMEWHAT VARIABLE DURING THE AFTERNOON
HOURS AS A RESULT...BEFORE BECOMING SOUTHERLY TOWARD LATE
AFTERNOON/EARLY EVENING WITH THE SEABREEZE PROGRESSION. CLOUD
COVER WILL INCREASE WITH THE FRONT IN THE AREA...HOWEVER ANY
CEILINGS ARE EXPECTED TO REMAIN VFR AT THIS TIME.

EXTENDED AVIATION OUTLOOK...GROUND FOG COULD BRIEFLY PRODUCE
MVFR VISIBILITY AROUND DAWN MONDAY THROUGH WEDNESDAY. OTHERWISE...
VFR.

.MARINE...
AHEAD OF AN APPROACHING COLD FRONT...A RELATIVELY TIGHT SURFACE
PRESSURE GRADIENT WILL CONTINUE TO SUPPORT ELEVATED SOUTH TO
SOUTHWEST WINDS AROUND 15 TO 20 KT. WINDS WILL VEER TOWARD THE WEST
AND DIMINISH TOWARD DAYBREAK SATURDAY. SEAS WILL RANGE FROM 2-4
FT WITHIN NEARSHORE WATERS TO 4-5 FT BEYOND 20 NM.

SATURDAY THROUGH MONDAY...A SOMEWHAT PINCHED GRADIENT AHEAD OF
THE COLD FRONT AND LAND BREEZE CIRCULATIONS WILL RESULT IN WINDS
UP TO 15 KT SATURDAY MORNING...BEFORE GRADIENT RELAXES BY
AFTERNOON AS SEA BREEZE CIRCULATIONS TAKE HOLD AND WINDS DROP TO
MOSTLY 10 KT OR LESS. THERE IS STILL SOME SMALL BACK SWELL FROM
DISTANT TC EARL...BUT OVERALL SEAS WILL REACH NO MORE THAN 3 OR 4
FT.

THE COLD FRONT WILL LIE OVER OR NEAR THE COASTAL WATERS SATURDAY
NIGHT INTO EARLY NEXT WEEK...AND AS HIGH PRESSURE BUILDS EASTWARD TO
THE NORTH OF THE FRONT...THE SYNOPTIC FLOW WILL SHIFT TO ONSHORE
DURING THIS TIME. SPEEDS HOWEVER ARE CAPPED AT NO MORE THAN 10 OR 15
KT...ALTHOUGH THERE ARE SOME INDICATIONS OF A LATE NIGHT/EARLY
MORNING NE SURGE AROUND 12Z MONDAY. SEAS ARE LIMITED TO 3 OR 4
FT...WITH MOST OF THE WAVE ENERGY TO RESULT FROM WIND DRIVEN WAVES.

TUESDAY AND WEDNESDAY...WEAK HIGH PRESSURE BUILDING IN FROM THE
NORTH WILL RESULT IN LIGHT EASTERLY FLOW THROUGH THE PERIOD. THE
PRESSURE GRADIENT REMAINS WEAK...SO AFTERNOON SEA BREEZE AND
NOCTURNAL LAND BREEZE CIRCULATIONS WILL PREVAIL. WINDS WILL
GENERALLY BE 10-15 KT OR LESS...AND SEAS NO MORE THAN 3 OR 4 FT.

RIP CURRENTS...WITH STILL SOME SMALL LONG PERIOD SWELLS AT THE
BEACHES ON SATURDAY AND GIVEN THAT IT IS THE START OF A HOLIDAY
WEEKEND...WE HAVE OPTED FOR A MODERATE RISK OF RIP CURRENTS.

.FIRE WEATHER...
SC FORESTRY OFFICIALS REPORT THAT FAIRLY DRY CONDITIONS ARE IN
PLACE ACROSS MUCH OF THE AREA...BASED ON DROUGHT INDICES AND FUEL
MOISTURE VALUES. WILL HOLD OFF ON ISSUING A FIRE DANGER STATEMENT
AS WINDS AND RELATIVE HUMIDITY VALUES ARE NOT EXPECTED TO REACH
CRITICAL LEVELS.

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