Area Forecast Discussion
Issued by NWS Charleston, SC

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493
FXUS62 KCHS 281954
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
354 PM EDT THU APR 28 2016

.SYNOPSIS...
A WEAKENING COLD FRONT WILL APPROACH THE AREA LATE TONIGHT INTO
FRIDAY...THEN SHIFT OFFSHORE AND DISSIPATE OVER THE WEEKEND.
LOW PRESSURE WILL TRACK TO OUR NORTH ON SUNDAY...BRINGING UNSETTLED
CONDITIONS TO THE AREA. ATLANTIC HIGH PRESSURE WILL THEN PREVAIL
EARLY NEXT WEEK BEFORE A COLD FRONT APPROACHES THE AREA MID WEEK.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
ATLANTIC HIGH PRESSURE WILL WEAKEN AS AN AREA OF LOW PRESSURE
AND ASSOCIATED WEAK FRONT SAGS SOUTH TOWARDS THE FORECAST AREA.
LATEST RADAR TRENDS SHOW CONVECTIVE ACTIVITY INCREASING ACROSS THE
LOCAL AREA...HOWEVER COVERAGE IS STILL FAIRLY ISOLATED. GIVEN
LACK OF ANY NOTABLE FORCING MECHANISMS...0-6 KM SHEAR OF LESS THAN
20 KT AND MLCAPE OF AROUND 1500 J/KG...THE THREAT FOR ORGANIZED
SEVERE WEATHER LOOKS LOW. BEST CHANCES FOR STRONGER STORMS WOULD
BE ALONG BOUNDARY INTERACTIONS...SUCH AS THE SEA BREEZE OR OUTFLOW
BOUNDARIES. DCAPE OF 1000 J/KG WOULD SUPPORT GUSTY WINDS AS THE
PRIMARY THREAT WITHIN ANY STRONGER STORMS THAT DO DEVELOP. HI RES
MODELS INDICATE THAT CONVECTIVE COVERAGE WILL GRADUALLY WANE WITH
LOSS OF INSOLATION LATE THIS EVENING. THE REMAINDER OF THE NIGHT
SHOULD BE RELATIVELY QUIET WITH CLEARING SKIES. ANOTHER MILD NIGHT
EXPECTED WITH LOWS EXPECTED TO RANGE FROM THE MID 60S INLAND TO
UPPER 60S AT THE COAST.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
FRIDAY...A DEEP LAYER RIDGING AND DRIER MID AND UPPER LEVELS WILL
MOVE IN WITH NO PRECIPITATION MOST OF THE PERIOD. EXPECTED. A WEAK
FRONT IS EXPECTED TO STALL AND DISSIPATE JUST SOUTH OF THE AREA.
VERY WARM AGAIN WITH HIGHS IN THE UPPER 80S TO AROUND 90...EXCEPT
SLIGHTLY COOLER NEAR THE COAST AS LIGHT WINDS TURN TO ONSHORE BY
AFTERNOON. MOSTLY CLEAR FRIDAY NIGHT WITH LOWS IN THE 60S.

SATURDAY...THE DEEP LAYER RIDGE SHIFTS EASTWARD THROUGH THE DAY AS
THE NEXT UPPER TROUGH MOVES INTO THE CENTRAL PORTION OF THE COUNTRY.
BY LATE IN THE DAY THERE COULD BE ENOUGH MOISTURE AND SOME WEAK
UPPER FORCING ON THE EAST OF THE ADVANCING TROUGH TO PRODUCE
ISOLATED CONVECTION OVER THE WESTERN PORTION. THUS HAVE KEPT SLIGHT
CHANCE POPS OVER THAT REGION. HIGHS AGAIN VERY WARM IN THE UPPER 80S
TO NEAR 90...EXCEPT COOLER AT THE COAST DUE TO SOUTHERLY FLOW
VEERING TO A RESULTANT SEA BREEZE DURING THE AFTERNOON. INCREASING
MOISTURE/CLOUDS SATURDAY NIGHT AS THE UPPER TROUGH MOVES
EASTWARD...BUT REMAINING WELL NORTH OF THE AREA. THERE WILL BE SOME
WEAK UPPER IMPULSES MOVING ACROSS THE REGION IN THE DEEP SOUTHWEST
FLOW...BUT WITH LACK OF STRONG FORCING AND LOSS OF
HEATING/INSTABILITY...HAVE KEPT ONLY SLIGHT CHANCE POPS. LOWS AGAIN
MILD IN THE MID TO UPPER 60S.

SUNDAY...LOOKS TO BE THE MOST UNSETTLED DAY OF THE PERIOD.
SUFFICIENT DEEP LAYER MOISTURE AND CAPE VALUES 1000-1500 J/KG ON THE
SOUTHEAST SIDE OF THE UPPER TROUGH OVER THE OH RIVER VALLEY...SHOULD
TRANSLATE TO SCATTERED SHOWERS AND THUNDERSTORMS. AGAIN...NO STRONG
UPPER FORCING...THUS FEEL BEST CHANCES WILL BE MAINLY AFTERNOON
COINCIDENT WITH MAXIMUM HEATING/INSTABILITY. HIGHS A TAD COOLER
THAN PREVIOUS DAYS DUE TO CLOUD COVER...IN THE MID 80S MOST AREAS.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
CHANCES OF SHOWERS AND THUNDERSTORMS WILL PERSIST SUNDAY NIGHT INTO
MONDAY AHEAD OF A COLD FRONT EXPECTED TO SHIFT THROUGH THE AREA
MONDAY AFTERNOON/EVENING. DRYER HIGH PRESSURE WILL THEN FILTER INTO
THE REGION MONDAY NIGHT INTO EARLY TUESDAY...BEFORE SFC LOW PRESSURE
DEVELOPS TO THE SOUTH OR SOUTHWEST AND TRACKS OVER THE AREA TUESDAY
AFTERNOON THROUGH WEDNESDAY. CHANCES OF SHOWERS AND THUNDERSTORMS
WILL REMAIN IN THE FORECAST MID WEEK UNTIL SFC LOW PRESSURE SHIFTS
OFFSHORE WEDNESDAY NIGHT. DRY CONDITIONS AND BELOW NORMAL TEMPS ARE
THEN EXPECTED HEADING INTO LATE WEEK WHILE A LARGE TROUGH OF LOW
PRESSURE DOMINATES THE EASTERN CONUS.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
VFR FOR MUCH OF THE 18Z TAF PERIOD. ISOLATED TO SCATTERED
SHOWERS/TSTMS WILL AFFECT THE REGION THIS AFTERNOON. TIMING AND
COVERAGE WILL BE DIFFICULT TO PINPOINT SO AMENDMENTS WILL LIKELY
BE NEEDED SHOULD CONVECTION AFFECT THE TERMINALS.

EXTENDED AVIATION OUTLOOK...VFR EXPECT TO PREVAIL.
SATURDAY NIGHT THROUGH EARLY NEXT WEEK...BETTER DEEP LAYER MOISTURE
RETURNS WITH SCATTERED MAINLY AFTERNOON SHOWERS AND THUNDERSTORMS
POSSIBLE...WHICH COULD PRODUCE BRIEF FLIGHT RESTRICTIONS.

&&

.MARINE...
TONIGHT...ATLANTIC HIGH PRESSURE WILL BEGIN TO LOSE INFLUENCE AS
AN AREA OF LOW PRESSURE AND WEAK FRONT SAGS SOUTHWARD TOWARDS THE
AREA. SOUTHWEST WINDS WILL VEER MORE TOWARD THE WEST LATE AS THIS
OCCURS WITH SPEEDS EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY
CRITERIA GENERALLY IN THE 10-15 KT RANGE...HIGHEST ACROSS
CHARLESTON COUNTY AND OUTER GA WATERS. SEAS WILL AVERAGE 2-4 FT.

FRIDAY THROUGH TUESDAY...NO HIGHLIGHTS EXPECTED THROUGH THE
PERIOD WITH WINDS GENERALLY 15 KNOTS OR LESS AND SEAS 3 FEET OR
LESS. ATLANTIC HIGH PRESSURE WILL DOMINATE FRIDAY THROUGH
SATURDAY. BY SUNDAY AND LIKELY INTO MONDAY...BECOMING A BIT MORE
UNSETTLED AS AN UPPER TROUGH MOVES WELL NORTH OF THE WATERS.
EXPECT ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THIS PERIOD. THERE IS MODEL UNCERTAINTY BY LATER MONDAY AND
TUESDAY. THE GFS AND CANADIAN MODELS SHOW A COLD FRONT MOVING
SOUTH OF THE AREA LATER MONDAY AND TUESDAY WITH HIGH PRESSURE
BUILDING FROM THE NORTH...WHILE THE ECMWF KEEPS UNSETTLED
CONDITIONS WITH AN ELONGATED AREA OF LOW PRESSURE OVER THE MID
ATLANTIC STATES. DUE TO UNCERTAINTY...HAVE KEPT PREVIOUS FORECAST
OF SLIGHT CHANCE POPS THROUGH THIS PERIOD...AND WILL LET THE
MIDNIGHT SHIFT RE-EVALUATE.


&&

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

&&

$$
SYNOPSIS...
NEAR TERM...ECT
SHORT TERM...RFM
LONG TERM...
AVIATION...ECT
MARINE...ECT/RFM



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