Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 031947
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
347 PM EDT SUN MAY 3 2015

.SYNOPSIS...
HIGH PRESSURE OVER THE WATERS WILL SHIFT FURTHER OFFSHORE TONIGHT
AND PREVAIL THROUGH AT LEAST THE MIDDLE OF THIS WEEK. AN AREA OF LOW
PRESSURE IS EXPECTED TO DEVELOP NEAR THE BAHAMAS...AND COULD MEANDER
OFF THE SOUTHEAST COAST MID WEEK INTO NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
TONIGHT...QUIET AND DRY WEATHER EXPECTED AS THE FORECAST AREA
REMAINS UNDER THE INFLUENCE OF SURFACE HIGH PRESSURE CENTERED
OVER THE MID ATLANTIC. DIURNAL CUMULUS FIELD WILL QUICKLY DIE OFF
AFTER SUNSET...WITH MOSTLY CLEAR SKIES EXPECTED OVERNIGHT. A
COUPLE MODELS HINT AT SOME LIGHT FOG DEVELOPING TOWARDS
SUNRISE...HOWEVER CROSSOVER TEMPS WILL NOT BE REACHED AND
SOUNDINGS REMAIN QUITE DRY IMMEDIATELY ABOVE THE SURFACE. TRENDED
ON THE COOLER SIDE OF GUIDANCE AGAIN GIVEN FAVORABLE RADIATIONAL
COOLING CONDITIONS. LOWS WILL RANGE FROM MID 50S INLAND TO UPPER
50S/LOW 60S ALONG THE COAST WHERE LIGHT ONSHORE FLOW WILL KEEP
TEMPERATURES A BIT MORE MILD.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
MONDAY...A VERY WEAK UPPER TROUGH WILL BE OVER THE REGION FOR MUCH
OF THE DAY...WHILE AT THE SURFACE...A RIDGE OF HIGH PRESSURE WILL BE
CENTERED NORTHEAST OF THE AREA OVER THE ATLANTIC. DEEP LAYER
MOISTURE IS ONCE AGAIN EXPECTED TO BE INSUFFICIENT TO WARRANT ANY POP
MENTION. LOW LEVEL WINDS WILL VEER TO EASTERLY BY AFTERNOON...WHICH
WILL KEEP HIGH TEMPS A LITTLE COOLER AT THE COAST IN THE MID 70S.
AWAY FROM THE COAST...EXPECT HIGHS AROUND 80 TO THE LOWER 80S.

MONDAY NIGHT THROUGH TUESDAY NIGHT...A DEEP LAYER RIDGE AXIS SETS UP
JUST NORTH OF THE AREA ACROSS NORTH CAROLINA AND TENNESSEE. THIS
WILL RESULT IN GENERALLY EASTERLY WINDS. TEMPERATURES WILL CONTINUE
PLEASANT WITH HIGHS AROUND 80 AND LOWS IN THE MID TO UPPER 50S
INLAND...AND LOWER 60S NEAR THE COAST. CHANCES FOR RAINFALL WILL
REMAIN LESS THAN 15% GIVEN LACK OF ANY UPPER FORCING AND DEEP LAYER
MOISTURE.

WEDNESDAY...MODELS START TO DIVERGE IN THEIR SOLUTIONS DURING THIS
TIME FRAME CONCERNING THE POTENTIAL FOR A LOW TO DEVELOP NORTH OF
THE BAHAMAS.  BOTH THE GFS AND ECMWF KEEP ANY LOW DEVELOPMENT AND
ASSOCIATED MOISTURE WELL SOUTH AND EAST OF THE AREA THROUGH THIS
PERIOD. THE GFS CONTINUES TO TREND STRONGER AND MORE WEST WITH THE
LOW THAN THE ECMWF...BUT STILL WELL SOUTHEAST OF THE AREA. THE NHC
ISSUED A SPECIAL OUTLOOK ON THIS SYSTEM...GIVING IT A 30% CHANCE TO
BECOME TROPICAL THROUGH 5 DAYS.

REGARDLESS OF WHETHER OR NOT THE SYSTEM BECOMES TROPICAL...ITS
EVENTUAL STRENGTH AND POSITION WILL DETERMINE WHAT IMPACTS OUR AREA
RECEIVES. STAY TUNED TO THE LATEST FORECASTS AND STATEMENTS FROM OUR
OFFICE AND THE NHC ON THE POTENTIAL FOR THIS SYSTEM TO DEVELOP.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
ATTENTION CONTINUES TO FOCUS ON LOW PRESSURE WHICH IS EXPECTED TO
DEVELOP OVER OR CLOSE TO THE BAHAMAS BY MID-WEEK. SINCE THE SURFACE
AND UPPER LOWS WILL RESIDE WITHIN A REX BLOCK PATTERN...BLOCKED BY
THE RIDGE TO THE NORTH...SLOW AND ERRATIC MOVEMENT OF THE SURFACE
LOW APPEARS LIKELY LATE WEEK THROUGH NEXT WEEKEND. IN FACT...LATEST
GUIDANCE EXHIBITS CONSIDERABLE SPREAD REGARDING THE STRENGTH...TRACK
AND RELATIVE TROPICAL/EXTRATROPICAL CHARACTERISTICS OF THE LOW...AND
THIS TRANSLATES TO A HIGH DEGREE OF FORECAST UNCERTAINTY LATE WEEK
INTO NEXT WEEKEND. REGARDLESS OF THE SOLUTION ONE CHOOSES...
DISCOUNTING THE 03/00 UTC CANADIAN SCENARIO A SIGNIFICANT/HIGH
IMPACT SYSTEM APPEARS UNLIKELY.

THE POTENTIAL FOR MOISTURE TO PUSH ONSHORE IS SUFFICIENT TO JUSTIFY
LOW POPS ESPECIALLY ALONG/EAST OF INTERSTATE 95 FRIDAY THROUGH
SUNDAY...BUT FORECAST CONFIDENCE REMAINS LOW EVEN REGARDING THE
POTENTIAL FOR ANY PRECIPITATION. THE ONGOING RAIN-FREE REGIME COULD
PERSIST THROUGH NEXT WEEKEND ESPECIALLY IF A WEAK LOW/TROUGH REMAINS
FARTHER OFFSHORE. OTHERWISE...HIGHS IN THE 80S AND LOWS IN THE 60S
SHOULD PREVAIL THROUGH THIS PERIOD.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
VFR CONDITIONS WILL PREVAIL AT KCHS AND KSAV THROUGH 18Z MONDAY.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS EXPECTED TO PREVAIL
THROUGH AT LEAST THE MIDDLE PART OF THIS WEEK. THE GLOBAL MODELS
CONTINUE TO TREND TOWARD A LOW PRESSURE CENTER MOVING SLOWLY
NORTHWARD OUT OF THE BAHAMAS BY MID WEEK. IF THE SYSTEM MOVES
FURTHER WEST/CLOSER TO OUR COAST...THEN IMPACT ON FLIGHT
RESTRICTIONS WILL BECOME MORE LIKELY...ESPECIALLY BY LATER
THURSDAY AND FRIDAY.

&&

.MARINE...
TONIGHT...QUIET MARINE CONDITIONS EXPECTED AS SURFACE HIGH PRESSURE
BECOMES ANCHORED OVER THE MID ATLANTIC. WEAK PRESSURE GRADIENT
WILL KEEP WINDS LESS THAN 10 KT. SOUTHEAST FLOW WILL EVENTUALLY
BACK MORE TO THE EAST NEAR DAYBREAK. SEAS ON AVERAGE WILL BE
AROUND 2 FEET IN THE NEARSHORE WATERS...3 FEET IN THE OUTER
PORTIONS.

MONDAY THROUGH TUESDAY...NO HIGHLIGHTS EXPECTED AS A DEEP LAYER
RIDGE SETS UP NORTH OF THE REGION OFF THE NORTH CAROLINA COAST. THIS
WILL RESULT IN EASTERLY FLOW OF GENERALLY 15 KTS OR LESS AND SEAS OF
4 FT OR LESS.

BY WEDNESDAY...MODELS BEGIN TO DIVERGE ON THE STRENGTH AND POSITION
OF THE LOW THAT IS EXPECTED TO DEVELOP JUST NORTH OF THE BAHAMAS.
LATEST WAVE WATCH GUIDANCE TRIES TO BRING IN 6-7 FOOT SEAS BY LATE
TUESDAY NIGHT AND WEDNESDAY OVER THE OFFSHORE GA WATERS. HOWEVER...
THIS GUIDANCE IS BASED OFF OF THE GFS SOLUTION...WHICH IS CURRENTLY
THE STRONGEST WITH THE LOW AND FARTHEST NORTH. FOR NOW...HAVE CAPPED
WINDS AROUND 6 FT...WHICH IS STILL LOW END SCA FOR THE OFFSHORE GA
WATERS.

THURSDAY AND FRIDAY...THE FORECAST WILL HINGE ENTIRELY ON THE
STRENGTH AND POSITION OF THE LOW PRESSURE SYSTEM MOVING IN FROM THE
SOUTH. FOR NOW...HAVE CONTINUED A SLOW RAMP UP IN WINDS AND SEAS AS
THE AREA WILL POSSIBLY BE AT LEAST ON THE WEST/NORTHWEST SIDE OF A
DEVELOPING LOW CENTER...WHICH NHC HAS RECENTLY PUT A 30% CHANCE OF
BECOMING TROPICAL IN NATURE. THEREFORE...EXPECT THAT SCA OR HIGH
WINDS/SEAS WILL BECOME MORE LIKELY BY LATE IN THE WORK WEEK.

RIP CURRENTS...RIP CURRENTS CONTINUE TO BE A CONCERN AS WE PROGRESS
THROUGH THE WEEK. HOWEVER...THE RISK WILL DEPEND VERY MUCH ON THE
EVENTUAL EVOLUTION OF THE LOW PRESSURE SYSTEM MENTIONED ABOVE. FOR
NOW...EXPECT THAT RIP RISKS WILL INCREASE BY MID AND LATE WEEK AS
SOME HIGHER SWELL AND POSSIBLY INCREASING WINDS MOVE INTO THE AREA.

&&

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

&&

$$
SYNOPSIS...
NEAR TERM...ECT
SHORT TERM...RFM
LONG TERM...
AVIATION...ECT
MARINE...ECT/RFM


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