Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 301130
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
730 AM EDT TUE JUN 30 2015

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL RESIDE ACROSS THE AREA WHILE A TROUGH
OF LOW PRESSURE PERSISTS INLAND.

&&

.NEAR TERM /THROUGH TONIGHT/...
THE SYNOPTIC PATTERN CONTINUES TO BE DOMINATED BY VERY STRONG
SUBTROPICAL RIDGES OVER THE GREAT BASIN AND WESTERN ATLC WITH A
MID/UPPER LEVEL TROUGH BETWEEN THEM ACROSS THE EASTERN HALF OF THE
UNITED STATES. QUIET WEATHER ON MONDAY LOOKS TO BE SHORT-LIVED AS
CHANCES FOR ISOLATED TO SCATTERED CONVECTIVE RAINS INCREASE FROM
THE WEST AFTER MID/LATE AFTERNOON WITH CHANCES FOR SHOWERS AND
TSTMS TO EVEN REACH THE COAST LATE DAY INTO THE EVENING HOURS. WE
HAVE MADE SOME CHANGES TO OUR FORECAST PACKAGE TO BUMP POPS UP TO
THE WEST OF I-95 IN THE 20Z-22Z TIME FRAME AND INTRODUCED 30 POPS
OVER A LARGE PORTION OF SE SOUTH CAROLINA THIS EVENING.

MODELS IN GOOD AGREEMENT ON MANY FEATURES SUCH AS DEEP LAYERED
MOISTURE ADVECTION AND BUILDING PWATS TODAY. A BROAD REGION OF
IMPROVED MID LEVEL INSTABILITY AND SOMEWHAT STEEPER LAPSE RATES
ACROSS THE UPPER GULF COAST TO NORTH GEORGIA ARE EXPECTED TO
SHIFT TOWARD OUR FORECAST REGION WITH 500 MB TEMPS AND MID LEVEL
HEIGHTS DIPPING A BIT JUST PRIOR TO 00Z INTO TONIGHT. ACROSS OUR
FORECAST AREA THIS AFTERNOON...DEEP MIXING FOR THIS TIME OF YEAR
IS FORECAST TO BE ONGOING AT MID AFTERNOON WITH TEMPS IN THE LOW
TO MID 90S. WE DO NOT THINK CONVECTIVE COVERAGE WILL BE TOO GREAT
GIVEN FORECAST PROXIMITY SOUNDINGS BUT WE MUST CONSIDER INCREASING
INCREASING DEEP LAYERED WIND FIELDS WITH 700 MB WINDS AROUND 30 KT
ACROSS THE CSRA AND SE MIDLANDS THIS AFTERNOON. DOWNDRAFT CAPES
ARE POTENTIALLY IMPRESSIVE SO WILL NEED TO FOLLOW UPSTREAM
CONVECTIVE TRENDS TODAY AS THE SEA BREEZE LOOKS TO BE FAIRLY
PINNED MUCH OF THE DAY.

THIS EVENING AND PERHAPS INTO THE NIGHT...THE SHORT WAVE WILL MOVE
THROUGH WITH THE MID LEVELS FAIRLY IMPRESSIVE FOR CONVECTION. THE
RESULTANT SEA BREEZE WILL ENHANCE SB CAPES ACROSS SE SOUTH
CAROLINA THIS EVENING AND ISOLATED TO SCATTERED SHOWERS AND TSTMS
POSSIBLE WITH SOME RISK FOR ISOLATED SEVERE WEATHER GIVEN THE
SWIFT STORM MOTIONS AND IMPROVED DEEP LAYERED INSTABILITY WITH
DAMAGING WIND GUSTS THE MAIN RISK. WITH COVERAGE/TIMING
UNCERTAINTIES...WE OPTED TO HOLD OFF INTRODUCING SEVERE WEATHER
IN OUR HAZARDOUS WEATHER OUTLOOK BUT IT MAY NEED TO BE ADDED AT
SOME POINT TODAY. CLOUDS WILL INCREASE LATER TODAY AND TONIGHT AND
A MILDER OVERNIGHT IS EXPECTED WITH LOWS IN THE MID 70S.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
WEDNESDAY...FLOW WILL BE RELATIVELY ZONAL FOLLOWING THE DEPARTURE OF
A SERIES OF SHORTWAVE PERTURBATIONS AROUND DAYBREAK. THERE ARE SOME
INDICATIONS THAT THERE WILL BE WEAK NEGATIVE VORTICITY ADVECTION
PRODUCING BROAD SUBSIDENCE ACROSS THE AREA AND ALLOWING DEWPOINTS TO
MIX INTO THE 60S IN THE AFTERNOON. PWATS ARE ONLY PROGGED AROUND
1.5" IN THE AFTERNOON. WITH 15-20 KT WSW 850 MB WINDS... THE SEA
BREEZE WILL BE PINNED NEAR THE COAST UNTIL LATE IN THE DAY.
CONDITIONS ARE NOT TERRIBLY CONDUCIVE FOR CONVECTIVE INITIATION
THOUGH WE CANNOT RULE OUT ISOLATED ACTIVITY. HIGHS WILL BE IN THE
LOW TO MID 90S.

THURSDAY...A SERIES OF SHORTWAVES WILL PUSH INTO THE AREA LATE IN
THE DAY. LOW-LEVEL FLOW WILL BACK...BRINGING BETTER MOISTURE INTO
THE AREA. PWATS WILL INCREASE SUBSTANTIALLY WITH READINGS
APPROACHING 2 INCHES BY LATE IN THE DAY. GIVEN BETTER MID-LEVEL
LAPSE RATES...INCREASING SURFACE THETA-E AND SYNOPTIC ASCENT... WE
EXPECT BETTER COVERAGE OF SHOWERS AND THUNDERSTORMS ESPECIALLY IN
THE AFTERNOON AND EVENING. HIGHS WILL BE IN THE LOWER 90S.

FRIDAY...A FAIRLY SIMILAR PATTERN WILL EXIST THOUGH THERE MAY BE
LESS SHORTWAVE ENERGY AS ON THURSDAY. NEVERTHELESS...BROAD TROUGH
PATTERN AND AMPLE DESTABILIZATION WILL SUPPORT SCATTERED SHOWERS AND
THUNDERSTORMS DURING THE DAYTIME HOURS. HIGHS WILL BE IN THE LOW TO
MID 90S.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
THE UPPER TROUGH WILL DEAMPLIFY ALLOWING THE RIDGE TO BUILD OVER THE
SOUTHEAST UNITED STATES. ATLANTIC HIGH PRESSURE WILL PREVAIL AT THE
SURFACE WHILE A TROUGH EXISTS WELL INLAND. WARMING MID LEVELS WILL
DECREASE THE COVERAGE OF SHOWERS AND TSTMS WHILE INCREASING
THICKNESSES YIELD HIGH TEMPS IN THE MIDDLE 90S MOST DAYS.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
VFR THROUGH 12Z WEDNESDAY WITH THE ONLY POTENTIAL PUNCTUATION
IN THE FORM OF ISOLATED TSTMS WHICH COULD IMPACT THE COASTAL
CORRIDOR BETWEEN 21Z AND 02Z. THERE IS A FAIR POSSIBILITY THAT
VCTS/CB MAY NEED TO BE INTRODUCED AT EITHER OF THE TERMINALS BY
THE 18Z TAF CYCLE.

EXTENDED AVIATION OUTLOOK...MAINLY VFR. BRIEF FLIGHT RESTRICTIONS
POSSIBLE IN AFTERNOON SHOWERS/THUNDERSTORMS.

&&

.MARINE...
ATLANTIC HIGH PRESSURE WILL GENERALLY DOMINATE THE WEATHER
PATTERN OVER THE COASTAL WATERS WITH A PIEDMONT TROUGH SITUATED
INLAND. TIGHTENED PRESSURE GRADIENT BETWEEN THE TWO FEATURES
WILL KEEP WINDS FAIRLY ELEVATED THROUGH THE PERIOD...HOWEVER NO
HEADLINES ARE ANTICIPATED AT THIS TIME. SEA BREEZE CIRCULATIONS
AND NOCTURNAL LOW LEVEL JETTING WILL ALLOW SOUTH/SOUTHWEST WINDS
TO PEAK 15-20 KT OR EVEN CLOSE TO 20 KT LOCALLY AT TIMES IN
FAVORED LOCATIONS. SEAS WILL BE 2-4 FEET ON AVERAGE...BUT MAY
REACH 5 FT IN THE OUTER PORTIONS OF THE WATERS DURING NOCTURNAL
SURGES.

&&

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

&&

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



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