Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 051112
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
712 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...WEAK LOW PRESSURE OFF OF THE OUTER BANKS OF NORTH
CAROLINA WILL DRIFT TO THE NORTHEAST. MEANWHILE A LARGE TROUGH
WILL HOVER OVER THE EAST COAST WHILE AN UPPER LEVEL LOW MOVES
SOUTH...SETTLING OVER THE CAROLINAS BY LATE IN THE DAY. THE
NORTHERN THIRD OF OUR AREA WILL BE UNDER THE SOUTHERN PERIPHERY OF
THE UPPER LEVEL LOW. THERE WILL BE OCCASIONAL WEAK VORT LOBES THAT
ROTATE ACROSS OUR THE AREA...GENERATING DECENT FORCING. DESPITE
THE FORCING THERE IS LIMITED MOISTURE IN THE ATMOSPHERE...PWATS
ARE ONLY AROUND 0.6 INCHES. THIS WILL LIMIT CONVECTIVE POTENTIAL.
WE MAINTAINED SLIGHT CHANCE POPS FOR THE NORTHERN THIRD OF OUR
AREA...MAINLY FOR LIGHT SHOWERS. A STRAY THUNDERSTORM IS NOT OUT
OF THE THE QUESTION LATE THIS AFTERNOON. BUT IT WILL BE DIFFICULT
FOR ONE TO DEVELOP DUE TO THE LACK OF MOISTURE AND BECAUSE
INSTABILITY IS MEAGER. AS FOR TEMPERATURES...WESTERLY WINDS AT THE
SURFACE AND NORTHWESTERLY ALOFT WILL AID IN COLD AIR ADVECTION
ACROSS OUT AREA. THIS WILL LEAD TO MUCH COOLER THAN NORMAL
TEMPERATURES...TOPPING OUT IN THE LOWER TO MID 70S ACROSS MOST
AREAS. A LARGE PRESSURE GRADIENT WILL ALSO LEAD TO BREEZY
CONDITIONS THIS AFTERNOON WITH 15 TO 20 MPH SUSTAINED WINDS AND
GUSTS OF 25 TO 30 MPH POSSIBLE.

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 /12Z THURSDAY THROUGH MONDAY/...
VFR THROUGH 12Z FRIDAY. BREEZY/GUSTY W/NW WINDS WILL PREVAIL
LATER THIS MORNING THROUGH THIS AFTERNOON AT BOTH TERMINALS WITH
GUSTS IN THE MID 20 KT RANGE AT TIMES.

EXTENDED AVIATION OUTLOOK...VFR WILL PREVAIL.

&&

.MARINE...
TODAY...LOW END SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED TO
PERSIST THROUGH THE DAY AND INTO THE EVENING FOR AMZ352-354-374.
MODELS INDICATE THAT WINDS COULD BRIEFLY GUST TO LOW END SMALL
CRAFT LEVELS FOR AMZ350 AND THE CHARLESTON HARBOR. BUT CONFIDENCE
WAS NOT HIGH ENOUGH TO PUT THESE TWO ZONES UNDER ADVISORIES.
CONDITIONS WILL GRADUALLY IMPROVE TONIGHT AS THE GRADIENT
DECREASES...ALLOWING WINDS/SEAS TO TREND DOWNWARD.

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 FROM 11 AM THIS MORNING TO 10 PM EDT THIS
     EVENING FOR AMZ352-354.
     SMALL CRAFT ADVISORY UNTIL 2 AM EDT FRIDAY FOR AMZ374.

&&

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



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