Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 230010
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
810 PM EDT FRI MAY 22 2015

.SYNOPSIS...
HIGH PRESSURE WILL EXTEND ACROSS THE REGION THROUGH EARLY NEXT WEEK.
A WEAK COASTAL TROUGH WILL PUSH TO THE GEORGIA COAST SATURDAY INTO
SUNDAY.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
TONIGHT...THE REGION WILL REMAIN ALONG THE NORTHERN PERIPHERY OF
STRONG RIDGING ALOFT. MEANWHILE...HIGH PRESSURE AT THE SURFACE
WILL MOVE FROM THE GREAT LAKES TO THE MID-ATLANTIC REGION. A DRY
AIRMASS AND A STRONG SUBSIDENCE INVERSION WILL RESULT IN FEW IF
ANY CLOUDS...AND EXPECT RATHER COOL AND DRY CONDITIONS ACROSS THE
AREA GIVEN A SYNOPTIC NORTH-NORTHEAST FLOW. IT SHOULD BE NOTED
THAT WHILE WINDS SHOULD DECOUPLE ACROSS MOST INLAND AREAS...THE
SURFACE PRESSURE GRADIENT AND ONSHORE FLOW COULD RESULT IN A MORE
MIXED/COUPLED ENVIRONMENT NEAR THE IMMEDIATE COAST. TEMPERATURES
WILL FALL TO LOWS IN THE MID AND UPPER 50S INLAND WHERE WINDS
DECOUPLE...BUT LIKELY ONLY FALL TO LOWS IN THE LOWER TO MID 60S
NEAR THE COAST.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
SATURDAY AND SUNDAY...HIGH PRESSURE OVER THE MID-ATLANTIC STATES
WILL STEADILY SHIFT OFFSHORE DURING THE PERIOD. MODELS SHOW A
WEAK/SUBTLE COASTAL TROUGH FEATURE DEVELOPING OFF THE SOUTHEAST
GEORGIA AND NORTHEAST FLORIDA COASTS, WHICH WILL SLOWLY SHIFT TO THE
BEACHES BY SUNDAY. THE 22/12Z NAM/GFS ARE SIMILAR IN SHOWING
ISOLATED-SCATTERED SHOWERS/TSTMS DEVELOPING OVER THE COASTAL WATERS
AND PUSHING ONSHORE SOUTH OF THE SAVANNAH RIVER ENTRANCE SATURDAY
NIGHT INTO SUNDAY, BUT THIS LOOKS A BIT BULLISH WITH THE ASSOCIATED
SREF MEMBERS AND THE 22/00Z ECMWF SHOWING MUCH DRIER SOLUTIONS.
PREFER TO LEAN CLOSER TO THE DRIER ECMWF/SREF ENSEMBLE MEAN, WHICH
IS ALSO SIMILAR THE PREVIOUS FORECAST. THIS KEEPS MENTIONABLE POPS
OUT OF THE FORECAST WITH SLIGHT CHANCE POPS CONFINED TO THE ADJACENT
GEORGIA COASTAL WATERS. IF THE 22/12Z ECMWF AND 22/21Z SREF TREND
WETTER...THAN THE INTRODUCTION OF MENTIONABLE POPS MAY BE NEEDED
WITH THE FULL FORECAST PACKAGE SATURDAY MORNING. HIGHS WILL RANGE
FROM LOWER-MID 80S BOTH DAY, POSSIBLY WARMING INTO THE UPPER 80S
WELL INLAND BY SUNDAY AFTERNOON. LOWS WILL RANGE FROM THE UPPER
50/NEAR 60 WELL INLAND TO THE LOWER 70S AT THE BEACHES SUNDAY
MORNING.

MONDAY...LOW-LEVEL MOISTURE WILL INCREASE MONDAY AFTERNOON AS HIGH
PRESSURE SHIFTS FARTHER OUT INTO THE ATLANTIC, HELPING TO ADVECT
HIGHER MEAN BOUNDARY LAYER-700 HPA THETA-E INTO THE REGION. THE BEST
LOW-LEVEL MOISTURE RETURN LOOKS TO BE CONFINED TO SOUTHEAST GEORGIA
WHERE A RISK FOR ISOLATED SHOWERS/TSTMS WILL OCCUR DURING THE
AFTERNOON AND EARLY EVENING HOURS. UPPER LEVEL RIDING WILL BE
SUBSTANTIAL WITH 500 HPA HEIGHTS REACHING 593 DM AND THE CENTER OF
THE 850 HPA ANTICYCLONE CENTERED DIRECTLY OVERHEAD. THIS WILL TEND TO
LIMIT THE OVERALL AMOUNT OF SHOWER/TSTM ACTIVITY WITH FAIRLY WARM
MID-LEVEL THERMAL PROFILES. SLIGHT CHANCE POPS WERE MAINTAINED FOR
ALL OF SOUTHEAST GEORGIA WITH POPS BELOW MENTIONABLE THRESHOLDS OVER
SOUTHEAST GEORGIA. HIGHS WILL RANGE FROM THE MID-UPPER 80S; COOLER
AT THE BEACHES.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
A STRONG DEEP LAYERED RIDGE WILL REMAIN THE DOMINANT WEATHER FEATURE
DURING THE LONG TERM PERIOD. INCREASING LOW-LEVEL THICKNESSES
SUPPORT A WARMING TREND WITH TEMPS SEVERAL DEGREES ABOVE NORMAL
THROUGH THE PERIOD. A STRONG MID-LEVEL CAP WILL MINIMIZE RAIN
CHANCES THROUGH WEDNESDAY. SOME SHORTWAVE ENERGY WILL BEGIN TO ERODE
THE RIDGE FROM THE WEST THURSDAY INTO FRIDAY...POTENTIALLY ALLOWING
FOR ISOLATED SHOWERS AND TSTMS TO MOVE INTO INLAND AREAS DURING THE
AFTERNOON HOURS.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
VFR CONDITIONS WILL PREVAIL THROUGH 00Z SUNDAY.

EXTENDED AVIATION OUTLOOK...VFR.

&&

.MARINE...
TONIGHT...HIGH PRESSURE WILL CROSS THE GREAT LAKES THIS EVENING
AND MOVE TOWARD THE MID ATLANTIC REGION THROUGH THE OVERNIGHT.
THIS WILL MAINTAIN THE ONGOING MODESTLY PINCHED GRADIENT ALONG THE
COAST AND CONTINUE TO FEED ELEVATED NORTHEAST FLOW. WINDS ALONG
THE LAND/SEA INTERFACE MAY BRIEFLY TURN MORE EASTERLY THIS
EVENING...BEFORE BECOMING NORTHEASTERLY AGAIN OVERNIGHT. THE
TIGHTEST GRADIENT WILL BE ACROSS THE GEORGIA WATERS WHICH WILL
SUPPORT 15-20 KT THROUGH THE NIGHT. ELSEWHERE...WINDS MAY DIMINISH
BACK TO 10-15 KT THIS EVENING BEFORE INCREASING BACK INTO THE
15-20 KT RANGE LATE TONIGHT. GIVEN THAT THE MAIN WIND DRIVER IS
PRESSURE GRADIENT RELATED AND NOT MIXING...FEEL PRETTY CONFIDENT
THAT GUSTS WILL BE LIMITED TO THE LOW 20 KT RANGE AT TIME AND
SMALL CRAFT ADVISORIES WILL NOT BE NEEDED. SEAS WILL BE UP TO 4 FT
OUT AROUND 20 NM MAINLY OFF THE GEORGIA COAST...AND 4-5 FT BEYOND
20 NM.

SATURDAY...AN ENHANCED PRESSURE GRADIENT WILL MAINTAIN LESS THAN
IDEAL CONDITIONS OVER THE COASTAL WATERS INTO SATURDAY. NORTHEAST
WINDS OF 15-20 KT WILL KEEP THE SEA STATE RATHER CHOPPY WITH SEA
BUILDING TO 3-4 FT NEARSHORE WATERS AND 4-5 FT BY SATURDAY AFTERNOON
AND 4-5 FT NEARSHORE WATERS WITH 5-6 FT OFFSHORE WATERS SATURDAY
NIGHT. A SMALL CRAFT ADVISORY MAY EVENTUALLY BE NEEDED...MAINLY FOR
THE GEORGIA OFFSHORE LEG WHERE SEA BREACH THE 6 FT ADVISORY
CRITERIA.

SUNDAY...WINDS WILL DIMINISH A BIT AS THE PRESSURE GRADIENT RELAXES
A BIT IN RESPONSE TO HIGH PRESSURE SHIFTING OUT INTO THE ATLANTIC.
WINDS WILL TURN MORE EASTERLY AS A RESULT WITH SPEEDS GENERALLY 15
KT OR SO. SEAS WILL REMAIN ELEVATED WITH 3-4 FT NEARSHORE WATERS AN
5-6 FT OFFSHORE WATERS.

MONDAY THROUGH WEDNESDAY...THERE ARE NO SIGNIFICANT CONCERNS WITH
WINDS GENERALLY 15 KT OR LESS AND SEAS 4 FT OR LESS.

&&

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

&&

$$

NEAR TERM...JAQ
SHORT TERM...ST
LONG TERM...JRL
AVIATION...JAQ
MARINE...BSH/ST



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