Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 291652
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1252 PM EDT TUE JUL 29 2014

.SYNOPSIS...
A COLD FRONT WILL STALL OFFSHORE TODAY THROUGH THE MIDDLE OF THE
WEEK. THE FRONT WILL THEN SLOWLY MOVE BACK TOWARDS THE SOUTHEAST
COAST LATE IN THE WEEK THROUGH EARLY NEXT WEEK... BRINGING MORE
UNSETTLED WEATHER TO THE LOCAL AREA.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UNDER MOSTLY SUNNY SKIES/AN UNSEASONABLY DEEP UPPER
TROUGH...TEMPERATURES THIS AFTERNOON WILL TOP OUT IN THE UPPER
80S/LOWER 90S. UNUSUALLY LOW DEWPOINTS MAINLY IN THE 60S WILL
PREVAIL.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
TONIGHT...THE FORECAST WILL REMAIN VERY QUIET WITH THE COLD FRONT
WELL OFFSHORE AND VERY DRY MID/UPPER LEVELS. THE PRESSURE FIELD WILL
BECOME A BIT NEBULOUS AND WEAK...RESULTING IN NEAR CALM CONDITIONS
IN MANY AREAS. MUCH COOLER LOWS ARE ON TAP AS WELL...WITH VALUES
EXPECTED TO FALL INTO THE UPPER 60S AWAY FROM THE IMMEDIATE COAST.

A DEEP LAYERED GYRE WILL REMAIN SPINNING NEAR JAMES BAY IN CANADA
DURING THE MIDDLE AND LATTER PARTS OF THE WEEK...WITH AN ANOMALOUS
TROUGH TO REMAIN ANCHORED OVER THE EASTERN UNITED STATES.
SIMULTANEOUSLY AT THE SURFACE WE/LL FIND A STATIONARY FRONT
STRETCHING FROM OFF NEW ENGLAND TO SOUTHERN FLORIDA WEDNESDAY AND
THURSDAY...BEFORE THE FRONT BEGINS TO TREK BACK TOWARD THE SE COAST
ON FRIDAY. THERE COULD EVEN BE A WEAK WEDGE THAT ATTEMPTS TO FORM
WELL INLAND AS THE FRONT APPROACHES FROM THE SE LATE IN THE WEEK.

MOISTURE WILL GRADUALLY BEGIN ITS RETURN WEDNESDAY AS THE SYNOPTIC
FLOW VEERS AROUND TO THE EAST AND SE. FORCING FROM THE SEA BREEZE
LOOKS TO BE THE ONLY MECHANISM FOR A FEW SHOWERS OR T-STORMS TO POP.
BUT A STRONG CAP REMAINS IN PLACE...SO WE HAVE HELD OFF ON ANY
MENTIONABLE PRECIPITATION PROBABILITIES IN THE FORECAST AT THIS TIME.

THERE IS SLIGHTLY BETTER RAIN CHANCES TO OCCUR THURSDAY AS THE
INFLUX OF MARITIME AIR CONTINUES TO INCREASE AND OUR CAP IS WEAKER.
WE/LL SHOW NO HIGHER THAN 20 POPS ACROSS THE BOARD...ALTHOUGH THERE
ARE HINTS OF SOME MID LEVEL FORCING THAT COULD RESULT IN SLIGHTLY
GREATER COVERAGE.

OUR BEST CHANCE OF RAINFALL FOR THE SHORT TERM PERIOD WILL COME
FRIDAY...AS THE CAP HAS ERODED AND THERE IS A CONTINUED FEED OF
MOISTURE FROM THE ATLANTIC IN THE LOW LEVELS. ADDITIONALLY THE FLOW
ALOFT BACKS MORE TO THE SW WITH SOME RETROGRESSION TO THE LONG WAVE
TROUGH IN THE EAST. THIS PROVIDES FOR A FEED OF GULF MOISTURE...AND
ALSO ALLOWS THE STATIONARY FRONT TO LIFT BACK CLOSER TO THE SE
COAST. WE/LL BUMP POPS INTO THE SOLID CHANCE RANGE AS A RESULT.

THE BROAD CYCLONIC FLOW ALOFT COMBINED WITH A FETCH OFF THE ATLANTIC
AND INCREASING RAIN CHANCES WILL HOLD DAYTIME TEMPS DOWN A BIT BELOW
LATE JULY/EARLY AUGUST NORMS. NIGHT TIME LOWS WILL AVERAGE NEAR OR
SLIGHTLY BELOW NORMAL.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
THE LATTER PORTION OF THE FORECAST PERIOD LOOKS TO BE RATHER
UNSETTLED WITH THE MEAN LONG WAVE TROUGH POSITION ALOFT TO SHIFT A
HAIR FURTHER WEST...AND THE SUB-TROPICAL ATLANTIC RIDGE TO NOSE IN
FROM THE EAST. THIS ALLOWS FOR THE STATIONARY FRONT AT THE SURFACE
TO SET UP OVER OR NEAR THE FORECAST AREA THIS WEEKEND AND EARLY
NEXT WEEK. MOISTURE WILL CONTINUE TO STREAM IN COURTESY OF A SE
AND SOUTH FLOW IN THE LOW LEVELS AND A RICH SW FEED IN THE MID AND
UPPER REACHES OF THE TROPOSPHERE. FORCING DUE TO THE PROXIMITY OF
THE STATIONARY FRONT WILL PROVIDE THE NECESSARY LIFT TO GENERATE
AT LEAST A SOLID CHANCE OF PRECIPITATION COVERAGE THROUGHOUT.
TEMPS WILL BE HELD IN CHECK DUE TO PLENTY OF CLOUDS AND THE HIGHER
RAIN CHANCES.

THERE ARE FORTUNATELY STILL NO INDICATIONS THAT ANY SORT OF TROPICAL
OR SUB-TROPICAL LOW WILL FORM ON THE FRONT...ESPECIALLY SINCE IT
LOOKS TO HAVE TOO MUCH INTERACTION WITH THE NEARBY LAND MASS OF THE
SE. HOWEVER...THE TROPICAL WAVE IN THE EASTERN ATLANTIC HAS A HIGH
PROBABILITY OF DEVELOPING INTO A TROPICAL CYCLONE. BUT THIS FEATURE
LOOKS TO CURVE OUT IN THE ATLANTIC...TURNING AWAY FROM CONUS BEFORE
IT GETS MUCH FURTHER WEST THAN ABOUT 70-75 DEGREES AND TO THE NE OF
THE BAHAMAS. SHOULD IT BECOME A NAMED SYSTEM IT WOULD BE BERTHA. IN
2008 BERTHA WAS BOTH THE LONGEST LIVED AND EASTERNMOST DEVELOPING
JULY TROPICAL CYCLONE ON RECORD.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
VFR THROUGH THE 18Z TAF PERIOD.

EXTENDED AVIATION OUTLOOK...MAINLY VFR INTO THURSDAY. OCCASIONAL
FLIGHT RESTRICTIONS ARE POSSIBLE LATE WEEK AND NEXT WEEKEND AS A
STATIONARY FRONT MEANDERS CLOSE TO THE SE COAST.

&&

.MARINE...
MAINLY ONSHORE WINDS LESS THAN 10 KT WILL PREVAIL THIS AFTERNOON
INTO THIS EVENING. NE WINDS 10 KT OR LESS ARE EXPECTED TONIGHT.
SEAS WILL AVERAGE 1-2 FT WITHIN NEARSHORE WATERS AND 2-3 FT BEYOND
20 NM.

WEDNESDAY...CONDITIONS ACROSS THE
COASTAL WATERS WILL BE FAIRLY BENIGN WITH A LAX NE TO EAST
PRESSURE PATTERN. WE LOOK FOR WINDS HELD UNDER 10 OR 12 KT AND
SEAS MAINLY AROUND 2 FT.

THURSDAY THROUGH FRIDAY...HIGH PRESSURE TO THE NORTH AND THE
STATIONARY FRONT TO THE SE LIFTING SLOWLY BACK TOWARD THE AREA WILL
ALLOW FOR A SMALL INCREASE IN THE LOCAL GRADIENT. WINDS AND SEAS
WILL CLIMB A TAD...BUT REMAINING WELL BELOW ANY SMALL CRAFT ADVISORY
CRITERIA.

SATURDAY THROUGH SUNDAY...THE STATIONARY FRONT LOOKS TO SLIDE INTO
THE WATERS...PERHAPS EVEN MOVING ONSHORE OF THE SE. WINDS WILL VEER
IN RESPONSE...BUT STILL NOTHING MORE THAN ABOUT 12-18 KT AND 3 OR 4
FT SEAS.

&&

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

&&

$$

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





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