Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 010139
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
939 PM EDT SAT APR 30 2016

.SYNOPSIS...
HIGH PRESSURE WILL EXTEND ACROSS THE AREA TONIGHT AS A STATIONARY
FRONT TO THE NORTH TODAY LIFTS NORTH. LOW PRESSURE WILL PASS FAR
TO THE NORTH SUNDAY AND MONDAY. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DEVELOP OVER OR JUST NORTH OF THE AREA TUESDAY AND
WEDNESDAY. HIGH PRESSURE WILL BUILD BACK INTO THE AREA BY THE END
OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
THE 00Z SOUNDING FROM KCHS SHOWED PLENTY OF DRY/STABLE AIR ALOFT
WHICH HAS BEEN ANCHORED ACROSS MUCH OF THE FORECAST AREA TODAY.
LATEST RAP ANALYSIS SHOWS A RING OF DEEPER MOISTURE AND
INSTABILITY WHICH EXTENDS FROM AROUND VALDOSTA GA TO ATLANTA AND
CHARLOTTE EARLY THIS EVENING. THIS LINES UP WELL WITH CONVECTIVE
RAINS WHICH HAVE BEEN PULSING SINCE THE AFTERNOON HOURS IN THOSE
AREAS .OVERNIGHT...A MID LEVEL SHORT WAVE MOVING INTO WEST
GEORGIA IS FORECAST TO REACH THE I-95 CORRIDOR AROUND 12Z. MODELS
INDICATE THAT PWATS WILL INCREASE OVERNIGHT WITH GRADUALLY
IMPROVING MID LEVEL INSTABILITY FROM THE SW AND W.

SHOWERS MAY BEGIN TO NUDGE INTO THE SW GEORGIA ZONES THE NEXT 1-2
HOURS BUT THIS ACTIVITY WILL PROBABLY JUST CONTINUE TO WEAKEN
PROVIDING SOME SPOTTY SHOWERS AT TIMES PRIOR TO 2 AM. AS THE SHORT
WAVE NEARS LATE...WE MAY SEE AN INCREASE IN SHOWERS ALONG THE
SAVANNAH RIVER CORRIDOR...SPREADING NE OVER PARTS OF SE SOUTH
CAROLINA AFTER 08Z-09Z. AT THIS TIME WE HAVE MAINTAINED SLIGHT
CHANCE POPS IN THE FORECAST. CANNOT RULE OUT AN ISOLATED LATE
NIGHT TSTM GIVEN A BIT OF LOW LEVEL CAPE FORECAST TO ADVECT IN OFF
THE ATLC. GIVEN UNCERTAINTIES OF OCCURRENCE...TIMING AND OVERALL
COVERAGE...WE OPTED TO HOLD OFF THUNDER MENTION IN THE FORECAST AT
THIS TIME. CONDITIONS DO NOT LOOK OVERLY FAVORABLE FOR A LOT OF
FOG BUT SINCE QUITE A BIT OF STRATUS IS MAY OCCUR LATE...WE COULD
SEE SOME VSBYS IMPACTED BY THE LOWER CIGS ADJACENT TO THE CSRA
AND SOUTHERN MIDLANDS.

ABUNDANT HIGHER LEVEL CLOUDS AND THE FORMATION OF STRATUS/STRATOCU
WILL MAKE FOR MOSTLY CLOUDY OVERNIGHT. THAT ALONG WITH WEAK WARM
ADVECTION WILL LIMIT LOWS TO AN WARM 66-70F...OR ABOUT 8-9F ABOVE
NORMAL.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
AN UNSETTLED PATTERN EXPECTED THROUGH THIS PERIOD. A BROAD...
POSITIVELY TILTED UPPER LEVEL TROUGH...WILL REMAIN OVER THE NORTH-
CENTRAL PORTION OF THE COUNTRY. THIS WILL KEEP OUR REGION ON THE
SOUTHEAST PERIPHERY OF THE UPPER TROUGH...WITH PERIODIC WEAK UPPER
IMPULSES EXPECTED TO MOVE ACROSS THE REGION SUNDAY AND MONDAY. GIVEN
THE WEAKNESS OF THE UPPER FEATURES...TIMING OF CONVECTION IS
CHALLENGING. FOR SUNDAY AND MONDAY...HAVE KEPT CHANCE POPS FOR MUCH
OF THE AREA. GIVEN UPPER FORCING IS WEAK THROUGH THIS PERIOD...FEEL
BEST CHANCES WILL BE DURING THE AFTERNOON COINCIDENT WITH MAXIMUM
HEATING. CAPE VALUES ARE MODERATE IN THE 1000-1500 J/KG RANGE...BUT
WEAK BULK SHEARS WILL MEAN ANY THUNDERSTORM ACTIVITY SHOULD REMAIN
BELOW SEVERE LIMITS AND LACK ORGANIZATION. ALTHOUGH GUIDANCE
MAINTAINS HIGHER POPS THAN TYPICAL DURING THE NIGH TIME
PERIODS...CONFIDENCE NOT VERY HIGH THAT THIS WILL OCCUR. NEVER THE
LESS...HAVE KEPT LOW END CHANCE DURING THE NIGHT TO REMAIN CLOSER TO
GUIDANCE AND COLLABORATE BETTER WITH SURROUNDING OFFICES.

TUESDAY WILL HAVE THE STRONGEST/BEST UPPER LEVEL SUPPORT AS THE
BROAD TROUGH SHARPENS AND MOVES E-NE TOWARD THE MID ATLANTIC. AT THE
SURFACE...A WEAK LOW PRESSURE SYSTEM IS PROGGED TO TRACK ACROSS
THE CAROLINAS AND MID ATLANTIC. THIS WILL KEEP THE AREA ON THE
WARM/UNSTABLE SIDE OF THE SYNOPTIC LOW. HAVE KEPT HIGH END CHANCE
POPS...BUT WOULD NOT BE SURPRISED IF LATER FORECASTS NUDGE INTO
LIKELY OR HIGHER POPS. GIVEN BETTER UPPER FORCING FROM THE
TROUGH...AS WELL AS BEING ON THE ENTRANCE SIDE OF AN UPPER
JET...WILL BE MONITORING THE POTENTIAL FOR SOME STORMS TO BE
STRONG OR POSSIBLY SEVERE. TOO SOON TO ADD MENTION DUE TO
UNCERTAINTY WITH TIMING OF THE UPPER FEATURES AND DEEP LAYER
MOISTURE...WHICH MAY BE DEPARTING THE AREA BY LATE MORNING/EARLY
AFTERNOON. IF THAT HAPPENS...CHANCES FOR ANY STRONG STORMS WILL BE
MUCH LOWER. HIGHS IN THE LOWER 80S AND LOWS IN THE MID TO UPPER
60S.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
THERE IS STILL A FAIR AMOUNT OF DISAGREEMENT WITH THE MODELS TUESDAY
NIGHT ONWARD. THE 00Z GFS HAS WEAK LOW PRESSURE HOVERING OVER OR
NEAR US TUESDAY NIGHT INTO WEDNESDAY...THEN MOVING TO THE NORTHEAST
WEDNESDAY NIGHT FOLLOWED BY BUILDING HIGH PRESSURE THURSDAY. THE 00Z
ECMWF HAS A MUCH STRONGER/STRENGTHENING LOW DURING THIS SAME TIMER
PERIOD. HOWEVER...WRAP AROUND SHOWERS WILL PERSIST INTO THURSDAY
BEFORE HIGH PRESSURE BUILDS THURSDAY NIGHT INTO FRIDAY. THE 00Z
CANADIAN SEEMS TO BE IN THE MIDDLE OF THESE TWO...EXCEPT IT BRINGS
THE HIGH PRESSURE IN WEDNESDAY NIGHT. GIVEN ALL THE DIFFERENT
SOLUTIONS AND A GENERAL TROUGH OVER THE EAST COAST...OPTED TO KEEP
CHANCE POPS TUESDAY NIGHT INTO WEDNESDAY...FOLLOWED BY POPS TRENDING
DOWNWARD TO SLIGHT CHANCE WEDNESDAY NIGHT INTO THURSDAY. BUILDING
HIGH PRESSURE WILL BRING DRY CONDITIONS ON FRIDAY WITH BELOW NORMAL
TEMPERATURES.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
VFR INTO EARLY TONIGHT. CONDITIONS SHOULD DETERIORATE TO MVFR OR
PERHAPS IFR AT BOTH TERMINALS OVERNIGHT INTO SUNDAY MORNING...AS
BOUNDARY LAYER MOISTURE INCREASES WITHIN A SE/SOUTH FLOW. 18Z NAM
SOUNDINGS INDICATE A WEAKER NOCTURNAL INVERSION AND THIS COULD
MEAN A TRICKY FORECAST FOR THE OVERNIGHT WITH RESPECT TO CLOUD
COVERAGE AND TIMING CIGS IN THE COASTAL CORRIDOR. WHILE THERE
COULD BE A SHRA LATE TONIGHT INTO EARLY SUNDAY AT BOTH TERMINALS
DUE TO ENERGY MOVING IN ALOFT...ANY IMPACTS WOULD BE FAIRLY
BENIGN. VFR CONDITIONS WILL RETURN THE SECOND HALF OF SUNDAY
MORNING INTO EARLY AFTERNOON. DIURNAL CONVECTION POTENTIAL LOOKS
TOO LOW ON SUNDAY FOR ANY EARLY MENTIONS.

EXTENDED AVIATION OUTLOOK...UNSETTLED CONDITIONS WILL RESULT IN
THE CHANCE FOR PERIODIC FLIGHT RESTRICTIONS WITHIN SCATTERED
SHOWERS/THUNDERSTORMS...MAINLY DURING THE AFTERNOON HOURS BOTH
KCHS AND KSAV THROUGH TUESDAY.

WEDNESDAY AND THURSDAY...LATEST MEDIUM RANGE GUIDANCE INDICATING
THE AREA WILL BE AT THE SOUTHERN END/BASE OF A LARGE...CLOSED UPPER
LOW OVER THE NE U.S./SE CANADA. WITH MUCH DRIER DEEP
LAYER MOISTURE...EXPECT THAT VFR WILL DOMINATE THIS PERIOD.

&&

.MARINE...
OVERNIGHT...A DECAYING STATIONARY FRONT NEAR THE NC/SC BORDER AND
EXTENDING EAST/SE INTO THE ATLANTIC AS A 1025 MB HUGGING THE COAST
OF NEW ENGLAND CONTINUES TO POKE SW ACROSS THE LOCAL WATERS. THIS
SUPPORTS A MODEST EAST/SE FLOW WITH SPEEDS 10-15 KT AND SEAS
BUILDING TO 2-4 FT...HIGHEST BEYOND 40 NM OFF THE GA COAST.

SUNDAY THROUGH THURSDAY...NO HIGHLIGHTS ARE EXPECTED THROUGH THE
PERIOD. IN GENERAL...THE WATERS WILL SIT BETWEEN ATLANTIC HIGH
PRESSURE WELL ENE OF THE AREA AND LOWER PRESSURE OVER THE MID
ATLANTIC AND CAROLINAS. THIS WILL RESULT IN SOUTH-SOUTHWEST WINDS
OF 15 KNOTS OR LESS AND SEAS 3 FEET OR LESS. UNSETTLE CONDITIONS
LIKELY WITH SCATTERED SHOWER AND THUNDERSTORMS...ESPECIALLY MONDAY
AND TUESDAY.

&&

.EQUIPMENT...
THE CHARLESTON HARBOR NOS TIDE GAUGE HAS STOPPED REPORTING ALL
METEOROLOGICAL AND TIDE DATA. THE NATIONAL OCEAN SERVICE IS
INVESTIGATING THE CAUSE OF THE OUTAGE. AN ESTIMATED TIME FOR DATA
RESTORATION IS UNKNOWN AT THIS TIME.

&&

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

&&

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



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