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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 170740
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
340 AM EDT MON JUN 17 2013

.SYNOPSIS...
-- Changed Discussion --
HIGH PRESSURE WILL CONTINUE TO RETREAT FARTHER INTO THE ATLANTIC
EARLY THIS WEEK. A COLD FRONT WILL APPROACH FROM THE NORTHWEST
TUESDAY...THEN SLOWLY PROGRESS THROUGH THE AREA WEDNESDAY AND
THURSDAY. HIGH PRESSURE WILL BUILD FROM THE NORTH INTO NEXT
WEEKEND.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TODAY/...
-- Changed Discussion --
THROUGH SUNRISE...CLOUDS HAVE BEEN SLOW TO THICKEN EARLY THIS
MORNING. TEMPERATURES ARE RUNNING A TAD COOLER THAN EXPECTED AS A
RESULT. A LARGE MASS OF SHOWERS/TSTMS MOVING ACROSS NORTHERN
GEORGIA AND THE UPPER SAVANNAH RIVER VALLEY WILL CONTINUE TO
PROPAGATE SLOWLY EAST. MOST HIGH RESOLUTION MODELS DISSIPATE THE
BULK OF THIS ACTIVITY BEFORE REACHING THE FAR WESTERN ZONES PRIOR
TO SUNRISE. WILL MAINTAIN A MENTION OF SLIGHT CHANCE POPS IN THESE
AREAS TO COVER ANY ACTIVITY THAT MAY DRIFT EAST INTO THE LOCAL
FORECAST AREA.

TODAY...IT LOOKS TO BE CONVECTIVELY ACTIVE DAY AS THE UPPER RIDGE
RAPIDLY BREAKS DOWN AND THE WESTERN FLANKS OF ATLANTIC HIGH
PRESSURE BUCKLES. FILTERED SUNSHINE THIS MORNING WILL ALLOW
TEMPERATURES TO WARM QUICKLY INTO THE UPPER 80S FOR MOST
LOCATIONS AWAY FROM THE COAST WITH MODIFIED BUFR SOUNDINGS
SUPPORTING CONVECTIVE TEMPERATURES AROUND 84-85 DEGREES. THE
PRIMARY FOCI FOR TSTMS TO DEVELOP TODAY WILL BE ALONG A SOMEWHAT
ILL-DEFINED SEA BREEZE AND A CONVECTIVE OUTFLOW BOUNDARY THAT CAN
BE SEEN EMERGING FROM THE CONVECTION OVER NORTHERN GEORGIA EARLY
THIS MORNING. THE VARIOUS LAKE BREEZE CIRCULATIONS AROUND THE
SANTEE-COOPER LAKES COULD ALSO COME INTO PLAY AS THE AFOREMENTIONED
OUTFLOW BECOMES ALIGNED SOUTHWEST-NORTHEAST ACROSS THE INTERIOR
SOUTHEAST SOUTH CAROLINA ZONES BY EARLY AFTERNOON.

THERE LOOKS TO BE A PRETTY HEALTHY COVERAGE OF SHOWERS/TSTMS
DURING PEAK HEATING SO WILL BUMP POPS UP SLIGHTLY TO 60 PERCENT
AWAY FROM THE BEACHES...WHICH WILL LINGER INTO THE EARLY EVENING
HOURS. SHEAR IS WEAK AND INSTABILITY PROGNOSTICATIONS ARE NOT ALL
THAT IMPRESSIVE SO THE RISK FOR SEVERE WEATHER LOOKS TO BE PRETTY
LOW...HOWEVER AN ISOLATED WET MICROBURST OR TWO CAN NOT BE
COMPLETELY RULED OUT WHERE UPDRAFTS BECOME ENHANCED BY MESOSCALE
BOUNDARY INTERACTIONS. SHOWER/TSTMS ACTIVITY IS EXPECTED TO SLOWLY
FORM/REFORM ACROSS INTERIOR SOUTHEAST GEORGIA BY LATE AFTERNOON...
POSSIBLY BECOMING ENHANCED BY ADDITIONAL CONVECTIVE OUTFLOW.
-- End Changed Discussion --

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
-- Changed Discussion --
TONIGHT...SHOWER/TSTMS ACTIVITY WILL GRADUALLY WIND DOWN AS
INSTABILITY WANES WITH THE LOSS OF INSOLATION AND THE ATMOSPHERE
IS STEADILY OVERTURNED. THERE ARE SOME INDICATIONS THAT
CONVECTION COULD CLUSTER ALONG/NEAR THE ALTAMAHA RIVER EARLY THIS
EVENING AS THE GULF SEA BREEZE MAKES A RUN FOR THE FAR SOUTHERN
ZONES...BUT IT IS UNCLEAR WHETHER THE GULF SEA BREEZE WILL MAKE
IT THIS FAR NORTH. THIS WILL HAVE TO THE WATCHED CAREFULLY. WILL
CARRY 40-60 PERCENT POPS EARLY THIS EVENING...DIMINISHING TO 20-30
PERCENT FORTH OVERNIGHT HOURS. LOWS WILL RANGE FROM AROUND 70 WELL
INLAND TO THE MID 70S AT THE COAST.

TUESDAY...A PROGRESSIVE NEARLY ZONAL PATTERN ALOFT WILL ALLOW A
SERIES OF WEAK SHORTWAVES TO CONTINUALLY MOVE THROUGH THE SOUTHEAST
STATES EARLY IN THE WEEK. AT THE SURFACE...A WAVE OF LOW PRESSURE
WILL DEVELOP ALONG A COLD FRONT STRETCHING FROM APPROXIMATELY
UPSTATE SOUTH CAROLINA THROUGH COASTAL NORTH CAROLINA. THE
COMBINATION OF UPPER LEVEL ENERGY AND DEEP LAYER MOISTURE...ALONG
WITH FRONTAL CONVERGENCE...WILL SUPPORT INCREASING CONVECTIVE
COVERAGE BY TUESDAY AFTERNOON. THE BEST POTENTIAL FOR THUNDERSTORM
ACTIVITY WILL BE ALONG THE FAR INLAND TIER COUNTIES CLOSEST TO THE
LINGERING FRONT...YET SOLID DEEP WESTERLY FLOW SHOULD STILL PUSH
UPSTREAM CONVECTION TOWARD THE COAST. WILL THUS ADVERTISE
THUNDERSTORM CHANCES RANGING FROM 50 TO 60 PERCENT INLAND TO 40
PERCENT CLOSER TO THE COAST DURING THE DAYTIME HOURS. IF THE
CENTER OF THE MAIN SURFACE WAVE SLIPS TOWARD THE OUTER BANKS OF
NORTH CAROLINA LATE TUESDAY NIGHT...THEN SHOWER/THUNDERSTORM
COVERAGE WILL DECREASE FROM SOUTH TO NORTH AFTER MIDNIGHT.
SUFFICIENT SYNOPTIC SCALE FORCING WILL STILL MAINTAIN CHANCES IN
THE 20 PERCENT RANGE SOUTHEAST GEORGIA TO THE 30 TO 40 PERCENT
RANGE CHARLESTON TRI COUNTY REGION TOWARD THE PRE DAWN HOURS. HIGH
TEMPERATURES WILL REACH THE UPPER 80S TO AROUND 90 DEGREES AWAY
FROM THE LOCALLY COOLER COASTLINE.

WEDNESDAY...CONVECTIVE COVERAGE WILL SURGE AGAIN AFTER
DAYBREAK...AS THE AMPLIFYING SHORTWAVE TROUGH MOVING OVER THE EAST
COAST PULLS THE FRONT DIRECTLY INTO THE FORECAST AREA DURING THE
AFTERNOON HOURS. HAVE INDICATED HIGHEST THUNDERSTORM POTENTIAL OF
THE PERIOD ON WEDNESDAY...WITH LIKELY POPS FOR THE MAJORITY OF
THE ZONES AWAY FROM THE COASTLINE. THE AXIS OF THE LOW PRESSURE
WAVE WILL SHIFT INTO THE MARINE ZONES WITH THE MAIN SHORTWAVE
OVERNIGHT...PULLING DEEPEST MOISTURE AND ASSOCIATED CONVECTIVE
ACTIVITY TOWARD THE EASTERN HALF OF THE FORECAST AREA AND THE
COASTAL WATERS. HIGH TEMPERATURES ON WEDNESDAY WILL BE A BIT
TRICKY...ESPECIALLY ACROSS NORTHERN AREAS THAT COULD END UP ON THE
COOL SIDE OF THE DESCENDING FRONT. WILL INDICATE MID TO UPPER 80S
NORTHERN MOST ZONES AND UPPER 80S TO AROUND 90 FARTHER SOUTH.

THURSDAY...THE WEAK COLD FRONT WILL CONTINUE TO SLIP SOUTH THROUGH
THE FORECAST AREA EARLY IN THE DAY...BEFORE STALLING ALONG THE
SOUTHERN PERIPHERY AS IT BECOMES MORE PARALLEL TO FLOW ALOFT.
THERE IS SOME DISAGREEMENT BETWEEN THE GFS AND ECMWF MODEL
SOLUTIONS REGARDING PRECIPITATION COVERAGE...A RESULT OF THE GFS
MAINTAINING A MORE PROMINENT UPPER TROUGH OVER THE SOUTHEAST
STATES. HAVE OPTED TO MAINTAIN SOLID THUNDERSTORM CHANCES ACROSS
THE AREA FOR THE AFTERNOON PERIOD...INDICATING SLIGHTLY HIGHER
POTENTIAL ACROSS THE SOUTHERN SECTIONS CLOSEST TO THE STALLED
BOUNDARY. HIGH TEMPERATURES COULD ONCE AGAIN REFLECT A SLIGHT
NORTHEAST/SOUTHWEST GRADIENT...WITH SUBTLE COOLER CONDITIONS IN
THE MID TO UPPER 80S CHARLESTON TRI COUNTY REGION COMPARED TO
AROUND 90 DEGREES FARTHER SOUTH NEAR THE ALTAMAHA RIVER.

OVERALL SEVERE POTENTIAL LOOKS LOW THROUGH THE PERIOD...AS THE
STRONGEST SYNOPTIC FORCING AND WIND FIELDS REMAIN NORTH OF THE
FORECAST AREA. HOWEVER...AS IS TYPICAL THIS TIME OF YEAR...AN
ISOLATED STRONG TO SEVERE THUNDERSTORM IS POSSIBLE WHERE BOUNDARY
INTERACTIONS OCCUR AND ENHANCE UPDRAFT STRENGTH.
-- End Changed Discussion --

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
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THE CENTER OF UPPER LEVEL RIDGING WILL REMAIN WEST OF THE
REGION...ALLOWING THE PATTERN ALOFT FOR THE SOUTHEAST STATES TO
BE SOMEWHAT WEAK AND PROGRESSIVE THROUGH MUCH OF THE EXTENDED
PERIOD. THE LINGERING FRONT NEAR THE SOUTHERN PERIPHERY OF THE
FORECAST AREA LOOKS TO REMAIN GENERALLY IN PLACE...EVENTUALLY
TRANSITIONING INTO A COASTAL FRONT/COASTAL TROUGH FEATURE AS HIGH
PRESSURE BUILDS FROM THE NORTH. MEDIUM RANGE MODEL SOLUTIONS STILL
DIVERGE ON DETAILS FOR THE LATE WEEK AND WEEKEND PERIOD...AND HAVE
DECIDED TO MAINTAIN A RATHER GENERIC 30 PERCENT POP DURING THE
DAYTIME HOURS FRIDAY THROUGH AT LEAST SUNDAY. IF THE COASTAL
TROUGH PATTERN DOES INDEED TAKE SHAPE...THEN EXPECT BEST
CONVECTIVE COVERAGE TO TRANSITION OFFSHORE EACH NIGHT. HIGH
TEMPERATURES WILL VARY LITTLE EACH AFTERNOON...REACHING THE UPPER
80S TO AROUND 90 DEGREES AWAY FROM THE LOCALLY COOLER COASTLINE.
-- End Changed Discussion --

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
GENERALLY VFR. RISK FOR SHOWERS/TSTMS WILL INCREASE LATER THIS
MORNING AND INTO THE AFTERNOON. MODELS GENERALLY FAVOR THE
CORRIDOR OF GREATEST COVERAGE REMAINING TO THE WEST OF THE KCHS-
KSAV CORRIDOR...ALTHOUGH SOME OF THE HIGHER RESOLUTION DATA
SUGGEST KCHS MAY HAVE A BETTER SHOW LATER THIS AFTERNOON FOR
IMPACTS. WILL TEMPO 19-21Z FOR 4SM TSRA BR SCT015 BKN035CB TO
COVER FOR NOW. WILL LEAVE TSRA OUT OF THE KSAV TAF UNTIL CONFIDENCE
INCREASES. AMENDMENTS WILL MOST CERTAINLY BE NEEDED THROUGHOUT
THE DAY AS MESOSCALE AND SHORT TERM RADAR TRENDS BECOME MORE
APPARENT.

EXTENDED AVIATION...PERIODIC FLIGHT RESTRICTIONS MONDAY NIGHT
THROUGH THURSDAY IN ASSOCIATION WITH SCATTERED TO NUMEROUS
SHRA/TSRA.

&&

.MARINE...
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TODAY...SOUTHERLY WIND REGIME WILL PERSIST WITH WINDS GENERALLY 10
KT OR LESS AND SEAS 2-4 FT.

TONIGHT...WINDS WILL INCREASE SLIGHTLY AHEAD OF AN APPROACHING
COLD FRONT. SPEEDS COULD REACH AS HIGH AS 15-20 KT AT TIMES WITH
SEAS 2-4 FT. SMALL CRAFT ADVISORY CONDITIONS ARE UNLIKELY AT THIS
TIME.

TUESDAY THROUGH FRIDAY...THE MARINE ZONES WILL BECOME SITUATED
BETWEEN AN APPROACHING COLD FRONT/SURFACE TROUGH INLAND AND
RETREATING HIGH PRESSURE TO THE EAST EARLY THIS WEEK. SOUTHERLY
FLOW WILL SURGE SLIGHTLY BY WEDNESDAY AS THE PRESSURE GRADIENT
TIGHTENS BETWEEN THE TWO FEATURES...SUPPORTING A BRIEF PERIOD OF
15 TO 20 KT WINDS AND SEAS UP TO 5 FT BEYOND 20 NM. EXPECT WIND
DIRECTIONS TO VEER WEST/NORTHWEST AS THE FRONT STEADILY SLIPS INTO
THE FORECAST AREA THURSDAY...AS SPEEDS DIMINISH A BIT WITHIN A
WEAKENING PRESSURE GRADIENT. NUMERICAL MODEL SOLUTIONS DIFFER
REGARDING THE PRECISE LOCATION OF THE STALLING FRONT BY LATE
WEEK...AND WILL LEAN TOWARD PERSISTENCE IN INDICATING A GENERAL
EAST/NORTHEAST FLOW FOR THURSDAY AND FRIDAY. WINDS AND SEAS ARE
EXPECTED TO REMAIN BELOW ADVISORY CONDITIONS THROUGH THE PERIOD.
-- End Changed Discussion --


&&

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

&&

$$

ST/WMS