Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 292010
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
410 PM EDT SAT AUG 29 2015

.SYNOPSIS...
A STALLED FRONT TO THE SOUTH AND EAST OF THE AREA WILL LIFT NORTH
TONIGHT BUT GRADUALLY DISSIPATE LATE. UPPER LEVEL LOW PRESSURE
WILL PASS INLAND SUNDAY...THEN ATLANTIC HIGH PRESSURE WILL EXPAND
INTO THE REGION MONDAY THROUGH TUESDAY. MID TO LATE WEEK...THE
REMNANTS OF ONCE TROPICAL STORM ERIKA COULD DRIFT NORTHEAST OR
MEANDER OVER OR CLOSE TO THE REGION.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
SURFACE HIGH PRESSURE WILL PERSIST TO THE NORTH WHILE A STALLED
FRONT WILL LINGER OVER OR NEAR THE AREA. DEEP MOISTURE WILL
CONTINUE TO ADVECT NORTHWARD AHEAD OF UPPER LEVEL LOW PRESSURE TO
THE WEST AND THUS RAIN CHANCES LOOK TO BE HIGHER THAN NORMAL FOR
THIS TIME OF DAY. CHANCES WILL LIKELY BE LOW TO START THE NIGHT
BEFORE INCREASING GENERALLY FROM SOUTHEAST TO NORTHWEST AS
SHORTWAVE ENERGY ASSOCIATED WITH THE LOW ROTATES NORTHWARD INTO
THE AREA. COULD SEE A FEW WEAK THUNDERSTORMS AS INSTABILITY
INCREASES...ESPECIALLY NEAR THE COAST. ALSO...HEAVY RAINFALL WILL
BE POSSIBLE...MAINLY NEAR THE COAST AND OVER SOUTHEAST GEORGIA
WHERE THE BEST LOW-LEVEL CONVERGENCE AND DEEPER MOISTURE ARE
ANTICIPATED. LOW TEMPS SHOULD RANGE FROM ABOUT 70 INLAND TO MID
70S AT THE COAST.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
WE/RE IN STORE FOR A WET AND UNSETTLED WEATHER PATTERN DURING THE
EARLY PART OF THE UPCOMING WEEK...WITH A DEEP AND RICH FEED OF
TROPICAL-LIKE MOISTURE FROM THE GULF OF MEXICO AND ATLANTIC OCEAN.
WHILE THIS WILL KEEP DAYTIME TEMPS BELOW NORMAL FOR LATE AUGUST...IT
WILL RESULT IN THE POSSIBILITY FOR AT LEAST LOCALLY HEAVY RAINS AND
MAYBE EVEN A FLASH FLOOD CONCERN IN PARTS OF THE CWFA.

FOR SUNDAY AND SUNDAY NIGHT...A MID AND UPPER LOW OVER THE WESTERN
FLORIDA PANHANDLE AT DAYBREAK SUNDAY WILL LIFT NE AND GRADUALLY
OPENS INTO A WAVE AS IT HEADS TOWARD THE SOUTHERN APPALACHIANS. THIS
FEATURE WILL RESULT IN AN INCREASED/FOCUSED INFLUX OF CONSIDERABLE
MOISTURE WITH PWATS ABOVE 2 INCHES INTO SOUTHERN SC AND SE GA. IT
ALSO ARRIVES WITH DECENT FORCING FOR ASCENT IN RESPONSE TO A 55-65
JET MAX AND IT/S RESULTING UPPER DIVERGENCE AS IT PASSES OVERHEAD.
THIS WILL CAUSE AT LEAST SCATTERED TO NUMEROUS COVERAGE OF
CONVECTIVE RAINS...WITH THE GREATEST CHANCES EASTERN ZONES WHERE WE
FIND THE BEST LOW LEVEL CONVERGENCE AND ISENTROPIC ASCENT. GIVEN
THESE FACTORS...UPPER DYNAMICS AND AN ABUNDANCE OF MOISTURE WILL
SUPPORT DIURNALLY-DRIVEN RAINS HEAVY AT TIMES...ESPECIALLY ACROSS
THE EASTERN HALF OF THE REGION. RAIN CHANCE WILL STEADILY DIMINISH
INLAND AFTER DARK...WHILE CONTINUED CONVERGENCE AND AN INFLUX OF
MOISTURE RESULTS IN AT LEAST SCATTERED POPS NEARER THE COAST. THE
DAILY TEMP CURVE WILL BE INTERRUPTED BY RAIN-COOLED AIR...AND WE CAN
EXPECT THAT AT LEAST SOME SECTIONS WILL STRUGGLE TO HIT ABOVE 80F
DURING THE DAYLIGHT HOURS WHERE PRECIPITATION LINGERS FOR AN
EXTENDED PERIOD OF TIME.

MONDAY THROUGH TUESDAY...IN WAKE OF THE DEPARTING SHORT WAVE TROUGH
AN EXPANDING SUB-TROPICAL ATLANTIC RIDGE WILL BUILD OVER THE SE.
THIS LARGE SCALE SYSTEM WILL BE RESPONSIBLE FOR STEERING WHATEVER IS
LEFT OF ERIKA INTO THE GULF OF MEXICO AS IT HEADS TO THE FLORIDA
PANHANDLE LATE IN THE FORECAST PERIOD. WHILE THERE ARE NO
SIGNIFICANT DYNAMICS THAT ARE NOTED ALOFT...WE STILL ANTICIPATE A
SOLID BAND OF MOISTURE TO PERSIST ACROSS THE LOCAL DISTRICT FROM THE
GULF AND ATLANTIC. THIS WILL GENERATE AT LEAST SCATTERED TO NUMEROUS
SHOWERS AND ISOLATED TO SCATTERED T-STORMS...WITH THE HIGHEST
PROBABILITIES SOUTH AND EAST WHERE AGAIN WE FIND THE BEST LOW LEVEL
FORCING AND ISENTROPIC UPGLIDE. SIMILAR TO RECENT DAYS WHERE
PROLONGED RAINS PERSIST IT WILL MESS UP THE DIURNAL CURVE. AN
ABUNDANCE OF MOISTURE AND A WEAK STEERING FLOW WILL PROMOTE ERRATIC
SHOWER/THUNDERSTORM PROPAGATION AND LOCALLY EXCESSIVE RAINFALL.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
THROUGH THIS PERIOD...FORECAST DETAILS INCLUDING POPS WILL
SIGNIFICANTLY DEPEND ON THE STRENGTH AND TRACK OF THE REMNANTS OF
ERIKA...WHICH COULD DRIFT NORTH/NORTHEAST INTO THE REGION OR MEANDER
OVER THE SOUTHEAST. A STRONGER SYSTEM DRIFTING NORTH/NORTHEAST INTO
CLOSER PROXIMITY TO THE REGION COULD PRODUCE LOCALLY EXCESSIVE
RAINFALL AND EVEN AN INCREASED RISK FOR SEVERE WEATHER...INCLUDING
ISOLATED TORNADOES FOR AT LEAST SOME PART OF THE LONG TERM PERIOD.
BUT A WEAKER SYSTEM COULD MEANDER OUTSIDE OF OUR AREA WITH FEW
DIRECT IMPACTS. FOR NOW...THE FORECAST MAINTAINS HIGHER THAN NORMAL
POPS...ESPECIALLY DURING THE DAYTIME HOURS WHEN CHANCE TO HIGH
CHANCE POPS ARE INDICATED. TEMPERATURES SHOULD REMAIN CLOSE TO
NORMAL...AND 90F TEMPS ARE NOT INDICATED ANY DAY DURING THIS PERIOD.
ASIDE FROM INCREASING CONFIDENCE THAT THE REGION WILL NOT BE
DIRECTLY IMPACTED BY A SIGNIFICANT TROPICAL CYCLONE...UNCERTAINTY
REMAINS HIGH REGARDING IMPORTANT FORECAST DETAILS. EXPECT
ADJUSTMENTS WITHIN SUBSEQUENT FORECAST PACKAGES.

&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
CONTINUED DEEP MOISTURE AND FORCING FOR ASCENT FROM AN UPPER LOW
TO THE WEST AND AN UPPER JET WILL KEEP RAIN CHANCES ABOVE NORMAL
MOST OF THE PERIOD...ESPECIALLY LATE TONIGHT. HOWEVER...TIMING IS
UNCERTAIN SO ADDRESSED WITH VCSH...ALTHOUGH TS WILL BE
POSSIBLE...MAINLY LATE IN THE PERIOD. CIGS WILL MOSTLY BE VFR BUT
CAN/T RULE OUT SOME MVFR AT TIMES...ESPECIALLY LATE TONIGHT.

EXTENDED AVIATION OUTLOOK...PERIODIC FLIGHT RESTRICTIONS WILL OCCUR
THROUGH EARLY IN THE WEEK WITH OCCASIONAL SHOWERS/THUNDERSTORMS AND
MAYBE DUE TO LATE NIGHT/EARLY MORNING STRATUS/LIGHT FOG.

FOR WEDNESDAY AND THURSDAY...CONDITIONS REMAIN HIGHLY DEPENDENT ON
THE UNCERTAIN TRACK AND INTENSITY OF THE REMNANTS OF TROPICAL
CYCLONE ERIKA...BUT AT LEAST SPORADIC FLIGHT RESTRICTIONS CAN OCCUR
IN SHOWERS/THUNDERSTORMS AND LATE NIGHT/EARLY MORNING FOG/STRATUS.

&&

.MARINE...
TONIGHT...A STATIONARY FRONT JUST SOUTHEAST OF THE WATERS WILL
LIKELY MOVE NORTHWARD INTO THE AREA LEADING TO MORE SOUTHEASTERLY
WINDS LATE...ESPECIALLY OVER THE GEORGIA WATERS. AHEAD OF THE
FRONT THIS EVENING STEADY NORTHEAST WINDS UP TO 20 KT WILL
PREVAIL BUT WITH SEAS 4 FT OR LESS WE DON`T ANTICIPATE REACHING
ADVISORY CONDITIONS. MARINERS SHOULD BE ADVISED THAT SOME STRONG
THUNDERSTORMS WILL BE POSSIBLE...ESPECIALLY LATE TONIGHT...WITH
GUSTY WINDS...FREQUENT LIGHTNING AND HEAVY RAINFALL.

SUNDAY...THE COASTAL WATERS WILL BE MAINLY UNDER CONTROL OF ATLANTIC
HIGH PRESSURE...WITH MAYBE A LITTLE ENHANCEMENT FROM THE SEA BREEZE
CIRCULATIONS. THIS WILL ALLOW FOR EASTERLY WINDS AT OR BELOW 15
KT...WITH A MIX OF SWELLS AND SHORTER PERIOD WIND-DRIVEN WAVES TO
GENERATE SIGNIFICANT SEAS OF 2-4 FT.

SUNDAY NIGHT THROUGH THURSDAY...THE LOCAL WATERS WILL BE SITUATED ON
THE WESTERN SIDE OF BERMUDA HIGH PRESSURE...WHILE THE REMNANTS OF
ERIKA IS STEERED INTO THE EASTERN GULF OF MEXICO EARLY IN THE WEEK.
WHATEVER FORM IT/S IN WILL LIKELY THEN HEAD INTO THE FLORIDA
PANHANDLE...SOUTHERN GEORGIA AND/OR SOUTHERN ALABAMA DURING THE
MIDDLE OF NEXT WEEK. WHILE THERE WILL BE OCCASIONAL SURGES OF
WINDS...THEY LOOK TO REMAIN BELOW 15 OR 20 KT...WITH SEAS CAPPED AT
OR UNDER 5 FT THROUGH THE PERIOD.

MARINERS ARE ADVISED THAT SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS WILL OCCUR EACH OF THE NEXT SEVERAL DAYS AND NIGHTS.
SOME OF THESE STORMS WILL PRODUCE FREQUENT LIGHTNING...HEAVY RAINS
REDUCING VISIBILITIES TO NEAR ZERO AT TIMES AND WIND GUSTS UP TO AT
LEAST 30 KT WITH BRIEFLY HIGHER SEAS. REMEMBER TO MONITOR OUR
FORECASTS AND YOUR NOAA WEATHER RADIO.

RIP CURRENTS...WE RECEIVED REPORTS OF NUMEROUS RIP CURRENTS FROM
TYBEE BEACH SATURDAY AFTERNOON...SOME AS LARGE AS 30 YARDS WIDE BY
80 YARDS OUT. LIFEGUARDS ARE DIRECTING PEOPLE AWAY FROM REGION WHERE
THE RIP ARE OCCURRING. THUS A CONTINUATION OF A MODERATE RISK OF RIP
CURRENTS INTO THIS EVENING.

CONDITIONS WON/T BE MUCH DIFFERENT SUNDAY WITH ONSHORE WINDS...SMALL
SWELLS AND ASTRONOMICAL INFLUENCES FROM THE PERIGEE AND FULL MOON.
THIS WILL RESULT IN AT LEAST A MODERATE RISK OF RIP CURRENTS AT AREA
BEACHES.

WHILE WE START TO LOSE THE ASTRONOMICAL INFLUENCES AS WE GO THROUGH
THE WEEK...THERE IS STILL AN ONSHORE WIND COMPONENT AND POSSIBLE
SMALL SWELLS TO GENERATE A POSSIBLE ELEVATED RISK DURING AT LEAST THE
EARLY PART OF THE WEEK.

&&

.TIDES/COASTAL FLOODING...
TONIGHT...ASTRONOMICAL INFLUENCES DUE TO THE PERIGEAN SPRING
TIDES PLUS ONSHORE WINDS WILL MAINTAIN ELEVATED HIGH TIDE LEVELS
ALONG THE COAST. WE ISSUED A COASTAL FLOOD ADVISORY FOR MINOR
SALTWATER INUNDATION ALONG THE LOWER SOUTH CAROLINA AND NORTHERN
GEORGIA COASTS DURING THIS EVENING/S HIGH TIDE.

SUNDAY THROUGH MONDAY...ASTRONOMICAL INFLUENCES DUE TO THE PERIGEAN
SPRING TIDE PLUS ONSHORE WINDS WILL MAINTAIN ELEVATED HIGH TIDE
LEVELS AT AND NEAR THE COAST. WHILE WE WILL BE CLOSE TO POSSIBLE
SHALLOW COASTAL FLOODING IN CHARLESTON HARBOR WITH THE MORNING HIGH
TIDES INTO EARLY NEXT WEEK...A BETTER CHANCE FOR SHALLOW SALT WATER
FLOODING EXISTS WITH THE EVENING HIGH TIDE SUNDAY AND MONDAY.
COASTAL FLOOD ADVISORIES WILL LIKELY BE REQUIRED FOR AT LEAST PARTS
OF THE SC COAST...AND WE/LL BE CLOSE TO THE ADVISORY CRITERIA
FURTHER SOUTH...INCLUDING THE SAVANNAH AREA. ALSO OF NOTE...PERIODS
OF SHOWERS/THUNDERSTORMS WITH HEAVY RAIN ARE EXPECTED THROUGH THE
PERIOD. IF HEAVY RAIN FALLS IN COASTAL COMMUNITIES...INCLUDING
DOWNTOWN CHARLESTON AND/OR DOWNTOWN SAVANNAH AROUND THE TIMES OF
HIGH TIDE...MORE SIGNIFICANT FLOODING IS POSSIBLE.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...COASTAL FLOOD ADVISORY FROM 7 PM TO 11 PM EDT THIS EVENING FOR
     GAZ117-119-139-141.
SC...COASTAL FLOOD ADVISORY FROM 7 PM TO 11 PM EDT THIS EVENING FOR
     SCZ048>051.
MARINE...NONE.

&&

$$
SYNOPSIS...
NEAR TERM...RJB
SHORT TERM...33
LONG TERM...SPR
AVIATION...33/RJB
MARINE...33/RJB
TIDES/COASTAL FLOODING...


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