Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 301728
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
128 PM EDT TUE SEP 30 2014

.SYNOPSIS...
LOW PRESSURE OFF THE SOUTHEAST COAST WILL SHIFT FARTHER INTO THE
ATLANTIC TODAY. HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE
NORTH ON WEDNESDAY AND THURSDAY...BEFORE A STRONG COLD FRONT MOVES
THROUGH LATE FRIDAY AND FRIDAY NIGHT. HIGH PRESSURE WILL THEN BUILD
OVER THE REGION THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
NO CHANGES WERE MADE TO THE GOING FORECAST.

LOW PRESSURE LOCATED WELL OFF THE SOUTHEAST U.S. COAST WILL
CONTINUE TO MOVE AWAY FROM THE REGION TODAY. EXTENSIVE DRY AIR
ROTATING AROUND THE LOW WILL ERODE THE CLOUD DECK FROM NORTH-SOUTH
THROUGH THE REST OF THE MORNING AND INTO THE AFTERNOON BEFORE A
SHALLOW CUMULUS FIELD DEVELOPS. MOST AREAS SHOULD SEE SOME SUN...
THE FIRST TIME IN OVER A WEEK. THE RISK FOR MEASURABLE RAINFALL
HAS ENDED AND GRIDDED POPS WILL REFLECT THIS. HIGHS IN THE LOWER
80S LOOK REASONABLE. ONLY MINOR CHANGES WERE NEEDED FOR THE LATE
MORNING UPDATE.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
TONIGHT...HIGH PRESSURE WILL MOVE IN FROM THE NORTHWEST BEHIND A
SECONDARY SHORTWAVE TROUGH PUSHING THROUGH THE MID-ATLANTIC
REGION. TEMPS SHOULD BOTTOM OUT AROUND 60 INLAND WITH MID 60S CLOSER
TO THE COAST...EXCEPT NEAR 70 ALONG THE GA COAST.

WEDNESDAY THROUGH THURSDAY NIGHT...MID AND UPPER LEVEL RIDGING WILL
GRADUALLY STRENGTHEN OVER THE REGION...AS SURFACE HIGH PRESSURE
BUILDS FROM THE NORTH. THE RETURN FLOW AROUND THE SOUTHERN PERIPHERY
OF THE HIGH WILL RESULT IN SLIGHTLY GREATER MOISTURE AND THEREFORE
CLOUD COVER OVER SOUTHEAST GEORGIA...BUT GENERALLY EXPECT MOSTLY
CLEAR TO PARTLY CLOUDY SKIES ACROSS THE AREA. ANY SHOWERS SHOULD
REMAIN SOUTH OF THE AREA GIVEN SUBSIDENCE ASSOCIATED WITH THE HIGH
AND A LACK OF DEEP MOISTURE...BUT A FEW SHOWERS COULD MANAGE TO WORK
THEIR WAY INTO THE COUNTIES ADJACENT TO THE ALTAMAHA RIVER BY
THURSDAY NIGHT. FORECAST THICKNESS VALUES SUPPORT HIGHS WELL INTO
THE UPPER 80S...BUT GIVEN THE LOW LEVEL ONSHORE FLOW THE FORECAST
WILL INDICATE MID 80S CLOSER TO THE COAST WITH THE UPPER 80S LIMITED
TO AREAS WELL INLAND. LOWS WILL GENERALLY BE IN THE MID 60S...EXCEPT
IN THE UPPER 60S NEAR THE COAST.

FRIDAY...THE MID AND UPPER LEVEL RIDGE AXIS WILL SHIFT INTO THE
WESTERN ATLANTIC AS A TROUGH MOVES INTO THE GREAT LAKES REGION AND
BECOMES NEGATIVELY TILTED. MEANWHILE AT THE SURFACE...A STRONG COLD
FRONT WILL APPROACH FROM THE WEST. SCATTERED SHOWERS AND
THUNDERSTORMS WILL OVERSPREAD THE AREA IN ADVANCE OF THE
FRONT...WITH THE POTENTIAL FOR A FEW OF THE THUNDERSTORMS TO BECOME
STRONG IF THE ATMOSPHERE CAN DESTABILIZE ENOUGH.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
MEDIUM RANGE GUIDANCE IS IN VERY GOOD AGREEMENT WITH THE OVERALL
SYNOPTIC PATTERN...LEADING TO HIGHER THAN NORMAL CONFIDENCE IN THE
FORECAST FOR THE LONG TERM PERIOD. A DEEP UPPER LEVEL TROUGH WILL
LIFT OUT TO THE NORTHEAST OVER THE WEEKEND AND GET REPLACED BY A
MORE BROAD UPPER LEVEL TROUGH WHICH WILL ENCOMPASS MUCH OF THE
EASTERN UNITED STATES THROUGH EARLY NEXT WEEK. MEANWHILE AT THE
SURFACE...A STRONG COLD FRONT WILL MOVE ACROSS THE AREA FRIDAY
NIGHT...WITH HIGH PRESSURE THEN BUILDING OVER THE SOUTHEAST STATES
INTO EARLY NEXT WEEK.

AS FOR EXPECTED WEATHER...SCATTERED SHOWERS AND THUNDERSTORMS WILL
ACCOMPANY THE PASSAGE OF THE COLD FRONT FRIDAY NIGHT...WITH
RAIN-FREE CONDITIONS AND SIGNIFICANTLY COOLER TEMPERATURES THEN
EXPECTED THROUGH EARLY NEXT WEEK.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
VFR. SHALLOW GROUND FOG POSSIBLE AT BOTH TERMINAL EARLY WEDNESDAY
MORNING. WILL LIMIT VISIBILITIES TO MVFR FOR NOW...ALTHOUGH LOWER
CONDITIONS ARE POSSIBLE...ESPECIALLY AT KSAV.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED TO PREVAIL
THROUGH MUCH OF FRIDAY OUTSIDE OF ANY LATE NIGHT/EARLY MORNING
PATCHY FOG AND/OR STRATUS. FLIGHT RESTRICTIONS WILL BE POSSIBLE
FRIDAY NIGHT INTO EARLY SATURDAY WITHIN SCATTERED SHOWERS AND
THUNDERSTORMS ASSOCIATED WITH A PASSING COLD FRONT.

&&

.MARINE...
TODAY AND TONIGHT...THE BEST PRESSURE GRADIENT WILL OCCUR THIS MORNING
AS LOW PRESSURE DEEPENS A BIT AS IT MOVES FARTHER OFFSHORE. COULD
SEE SOME GUSTS TO 25 KT...ESPECIALLY OVER THE CHARLESTON COUNTY
WATERS AND OFFSHORE GA WATERS BUT DO NOT THINK AN ADVISORY IS
WARRANTED. SIGNIFICANT WAVE HEIGHTS SHOULD REMAIN 5 FT OR
LESS...HIGHEST IN THE AREAS THAT WILL SEE THE STRONGER WINDS.

WEDNESDAY THROUGH SUNDAY...WINDS/SEAS WILL REMAIN WELL BELOW SMALL
CRAFT ADVISORY LEVELS AS HIGH PRESSURE BUILDS FROM THE NORTH THROUGH
MIDWEEK. IN GENERAL...ONSHORE WINDS WILL REMAIN LESS THAN 15 KT WITH
SEAS NO HIGHER THAN 1-3 FT. SOUTHERLY FLOW WILL THEN STRENGTHEN ON
FRIDAY AHEAD OF A COLD FRONT...WHICH WILL PUSH OFFSHORE FRIDAY
NIGHT. OFFSHORE FLOW WILL THEN PREVAIL ON SATURDAY...WITH A SLIGHT
NORTHEAST SURGE POSSIBLE SUNDAY BEHIND A WEAK REINFORCING COLD
FRONT.

&&

.EQUIPMENT...
REPAIRS TO THE DOWNTOWN CHARLESTON WEATHER SENSOR AT WATERFRONT
PARK /KCXM/ ARE COMPLETE. HOURLY OBSERVATIONS ARE ONCE AGAIN
AVAILABLE. DAILY CLIMATE PRODUCTS WILL RESUME WEDNESDAY AFTERNOON.

&&

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

&&

$$

ST






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