Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 051431
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1031 AM EDT THU MAY 5 2016

.SYNOPSIS...
HIGH PRESSURE WILL EXPAND INTO THE AREA LATE FRIDAY THEN SHIFT
SOUTH OF THE REGION OVER THE WEEKEND. ATLANTIC HIGH PRESSURE WILL
THEN PREVAIL THROUGH THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
TODAY...A LARGE MID/UPPER LVL TROUGH OF LOW PRESSURE WILL DIG OVER
THE EASTERN CONUS...WITH ITS CENTER SETTLING OVER THE SOUTHEASTERN
UNITED STATES THIS AFTERNOON AND EVENING. STRONG COLD AIR ADVECTION
ASSOCIATED WITH THE LOW WILL HELP PROMOTE LOW LVL MIXING OVER THE
AREA THIS AFTERNOON...LEADING TO BREEZY WIND CONDITIONS AS SFC TEMPS
PEAK IN THE LOWER 70S. IN GENERAL...A 15-20 MPH WEST/NORTHWEST WIND
WILL PREVAIL WITH GUSTS UPWARDS TO 25-30 MPH AT TIMES. WE COULD ALSO
SEE A FEW SHOWERS DEVELOP OVER NORTHERN AREAS THIS AFTERNOON AS H5
TEMPS NEAR -26 C SUPPORT STEEPER MID LVL LAPSE RATES. HOWEVER...THE
OVERALL SHOWER COVERAGE INCLUDING THE THREAT OF ANY THUNDER WILL BE
QUITE LOW GIVEN CONSIDERABLE DRY AIR ASSOCIATED WITH A DOWNSLOPING
WEST/NORTHWEST WIND OVER THE REGION.

TONIGHT...THE PRESSURE GRADIENT WILL DECREASE...ALLOWING WINDS TO
EASE. BUT CONTINUED WEST/NORTHWEST FLOW AND MOSTLY CLEAR SKIES
WILL ALLOW TEMPERATURES TO SETTLE TO LEVELS THAT ARE STILL BELOW
NORMAL FOR THIS TIME OF YEAR. LOWS WILL BE CHILLY...IN THE UPPER
40S ACROSS THE INTERIOR AND THE LOWER 50S ALONG THE COAST.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
ON FRIDAY...THE DEEP AND COMPLEX UPPER TROUGH/CUT-OFF WILL PERSIST
BEFORE THE BASE OF THE TROUGH MOVES OFFSHORE ON FRIDAY NIGHT. ONLY
SCATTERED CLOUDS EARLY FRIDAY WILL EXPAND AND BECOME BROKEN ACROSS
THE REGION FRIDAY AFTERNOON AS DIURNAL HEATING IN THE BOUNDARY LAYER
RESULTS IN STEEP LOW LEVEL LAPSE RATES DESPITE SURFACE HIGHS ONLY
REACHING THE LOWER TO MID 70S. MID LEVELS WILL ALSO FEATURE COLD AIR
ALOFT WITH 500-700 MB LAPSE RATES NEAR -7.5C AND 500 MB TEMPS CLOSE
TO -23C. MODELS INDICATE QUITE A BIT OF QG FORCING ACROSS THE
CAROLINAS WITH DEEP CYCLONIC FLOW...HOWEVER A DISTINCT LACK OF
MOISTURE IS NOTED ACROSS OUR FORECAST AREA WITH SURFACE TEMP-DEW
POINT SPREADS OF 20F-30F PROGGED THROUGHOUT THE DAY. WE MAINTAINED
SLIGHT CHANCES OF SHOWERS ACROSS NORTHERN ZONES AND PERHAPS ISOLATED
LIGHT SHOWERS ELSEWHERE NORTH OF I-16 DURING THE AFTERNOON. THERE
COULD BE A FEW LOW-TOPPED TSTMS ACROSS NE SOUTH CAROLINA AND SMALL
HAIL MAY FALL GIVEN FREEZING LEVELS NEAR 6KT. WE INCLUDED A MENTION
OF TSTMS BORDERING THE SANTEE COOPER LAKES AND PEE DEE REGIONS.
SKIES WILL CLEAR FRIDAY NIGHT WITH COOL TEMPS FALLING TO THE LOWER
TO MID 50S BY DAYBREAK ON SATURDAY.

AS UPPER HEIGHTS BUILD ON SATURDAY AND SUNDAY WITH BOUNDARY LAYER
FLOW REMAINING OFFSHORE...A WARMING TREND IS IN STORE WITH AFTERNOON
TEMPS WARMING JUST ABOVE 80 DEGREES IN MANY AREAS ON SATURDAY WITH
PLENTY OF SUNSHINE. EVEN WARMER WEATHER IS ON TAP ON SUNDAY WITH
HIGHS AROUND 90 AND THE SEA BREEZE PINNED CLOSE TO THE BEACHES AND
BARRIER ISLANDS MAKING FOR A WARM AFTERNOON THERE AS WELL.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
MID LEVEL RIDGING EARLY NEXT WEEK WILL GRADUALLY BREAK DOWN THROUGH
MID WEEK. SURFACE HIGH PRES OVER THE ATLANTIC WILL BE THE DOMINANT
SYNOPTIC FEATURE FOR OUR REGION. TEMPS WILL REMAIN ABOVE CLIMO FOR
MUCH THE PERIOD. IT LOOKS LIKE WE WILL RETAIN A DECENT MID LEVEL CAP
ON MONDAY AND PROBABLY AGAIN ON TUESDAY. WE MAINTAINED SLIGHT CHANCES
FOR MAINLY DIURNAL SHOWERS AND TSTMS IN THE MID WEEK TIME FRAME.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
VFR THROUGH 12Z FRIDAY. BREEZY/GUSTY WEST/NORTHWEST WINDS WILL
PREVAIL THROUGH THIS AFTERNOON AT BOTH TERMINALS WITH GUSTS IN
THE MID 20 KT RANGE AT TIMES.

EXTENDED AVIATION OUTLOOK...VFR WILL PREVAIL.

&&

.MARINE...
TODAY...SMALL CRAFT ADVISORIES WILL REMAIN IN EFFECT FOR ALL WATERS
INCLUDING THE CHS HARBOR THROUGH THIS EVENING AS STRONG COLD AIR
ADVECTION ASSOCIATED WITH A MID/UPPER LVL LOW PROMOTES DEEP MIXING
IN THE ATMOSPHERE. IN GENERAL...WEST/NORTHWEST WINDS WILL RANGE
BETWEEN 15-20 KT WITH GUSTS UP TO 25-30 KT...HIGHEST IN OFFSHORE
GEORGIA WATERS. SEAS WILL ALSO BUILD DURING THE AFTERNOON...RANGING
BETWEEN 2-4 IN NEARSHORE WATERS AND 4-7 FT IN OFFSHORE GEORGIA
WATERS. CONDITIONS WILL BEGIN TO IMPROVE THIS EVENING IN THE CHS
HARBOR AS DIURNAL HEATING IS LOST.

TONIGHT...SMALL CRAFT ADVISORIES WILL LIKELY BE ONGOING IN
NEARSHORE WATERS EARLY WHILE THE PRESSURE GRADIENT REMAINS
ENHANCED AND COLD AIR ADVECTION PERSISTS. HOWEVER...THERE SHOULD
BE A GRADUAL IMPROVEMENT TO WINDS/SEAS OVER ALL WATERS THROUGH THE
OVERNIGHT PERIOD WITH CONDITIONS FALLING BELOW SMALL CRAFT
ADVISORY LEVELS IN NEARSHORE WATERS BY MIDNIGHT. FURTHER
OFFSHORE...WINDS/SEAS WILL REMAIN ELEVATED...PROLONGING THE SMALL
CRAFT ADVISORY IN OFFSHORE GEORGIA WATERS.

WINDS AND SEAS WILL DIMINISH ON FRIDAY IN THE WAKE OF THE POTENT
OVERNIGHT SURGE. THERE WILL BE ANOTHER SURGE FRIDAY NIGHT AS THE
UPPER TROUGH MOVES OFF THE COAST BUT THIS SURGE WILL NOT BE AS
SIGNIFICANT WITH A PERIOD OF 15 KT WITH 20 KT GUSTS OVER OUTER
WATERS OVERNIGHT.

OVER THE WEEKEND...SURFACE HIGH PRES WILL BUILD SW TO SE OF THE
WATERS AND THIS WILL RESULT IN THE FLOW BACKING TO SW. THERE COULD
BE BREEZY CONDITIONS IN THE INTRA-COASTAL WATERS EACH AFTERNOON AS
THERMAL GRADIENTS STRENGTHEN THANKS TO WARMER LAND TEMPS EACH DAY
AND ROBUST DEEP MIXING PROFILES DURING MAX HEATING. OTHERWISE SEAS
WILL AVERAGE 2 TO 3 FT.

MONDAY AND TUESDAY...ATLC HIGH PRES WILL MAINTAIN A SOUTHERLY FLOW
MAINLY AT OR BELOW 15 KT WITH SEAS 2 TO 4 FT...HIGHEST OFFSHORE.

&&

.EQUIPMENT...
THE NOAA WEATHER RADIO TRANSMITTER AT METTER GEORGIA OPERATING ON
A FREQUENCY OF 162.425 MHZ WILL BE OFF THE AIR UNTIL FURTHER
NOTICE.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR AMZ330.
     SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR AMZ350-
     352-354.
     SMALL CRAFT ADVISORY UNTIL 2 AM EDT FRIDAY FOR AMZ374.

&&

$$
SYNOPSIS...
NEAR TERM...DPB
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...DPB
EQUIPMENT...



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