000
FXUS62 KCHS 162343
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
743 PM EDT SUN JUN 16 2013

.SYNOPSIS...
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 TO THE NORTH INTO NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
EARLY SUNDAY EVENING...FORECASTS REMAINED ON TRACK.

FAIRLY TRANQUIL NIGHT ON TAP ALTHOUGH THERE WILL BE INCREASING
MOISTURE AHEAD OF AN APPROACHING UPPER TROUGH AND SURFACE COLD
FRONT. THE DIURNAL CUMULUS FIELD...FOCUSED ALONG THE INLAND
ADVANCING SEA BREEZE...WILL DISSIPATE THIS EVENING LEAVING MOSTLY
CLEAR SKIES TO START THE NIGHT. HOWEVER...CLOUDS WILL BE ON THE
INCREASE LATE. THERE COULD BE A FEW SHOWERS BY DAYBREAK DUE TO
COASTAL CONVERGENCE AND/OR ACTIVITY MOVING IN FROM THE WEST BUT
CHANCES OF MEASURABLE RAINFALL SEEM TOO LOW TO MENTION. LOWS
LIKELY IN THE UPPER 60S TO NEAR 70 INLAND WITH MID 70S AT THE
COAST.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
MONDAY...AN IMMENSE MID AND UPPER LEVEL TROUGH WILL BE FOUND OVER SE
CANADA...WHILE A FLAT AND STRETCHED OUT RIDGE IS LOCATED FROM THE SW
ATLANTIC ACROSS THE GULF AND NORTHERN OLD MEXICO INTO THE SE
PACIFIC. THE LOCAL REGIME WILL LIE NEAR THE SOUTHERN EXTENSION OF A
SLIGHTLY CYCLONIC FLOW ALOFT...WITH WEAK ENTRENCHED SHORT WAVES
FOUND WITHIN THE SOUTHERN STREAM OF THE JET. ONE OF THESE FEATURES
WILL TRIGGER THE DEVELOPMENT OF A VERY WEAK WARM FRONT OR TROUGH
ACROSS SOUTHERN GA IN THE AFTERNOON...AS THE LAST OF THE BERMUDA
SURFACE HIGH STRIVES TO HANG ON. THE MOST NOTICEABLE CHANGES IN THE
AIR MASS WILL BE THE RETURN OF HIGHER DEW POINTS...MUCH GREATER
MOISTURE AS PWATS TOP OUT NEAR 1.8 TO 1.9 INCHES AND WARMER TEMPS.
ALL THIS IS COURTESY OF THE RETURN FLOW AROUND THE ATLANTIC RIDGE.
INSTABILITY AND ESPECIALLY CAPE WILL BE AT HIGHER VALUES...THE
PERSISTENT SUBSIDENCE CAP WILL HAVE ERODED WHILE CINH WANES
THROUGHOUT THE DAY...AND THERE IS A LITTLE COOLER CONDITIONS IN THE
MID LEVELS. THE COMBINED INFLUENCES WILL ALLOW FOR THE RESUMPTION OF
OUR TYPICAL WARM SEASON CONVECTION...TRIGGERED BY THE SEA
BREEZE...THE SOUTHERN GA TOUGH OR WARM FRONT AND UPSTREAM BOUNDARIES
THAT COULD DRIFT IN WITH THE WESTERLY FLOW. DUE TO A SLOW STORM
MOTION OF NO MORE THAN ABOUT 10 KT AND THE ELEVATED PWATS...LOCALLY
HEAVY RAINS CAN OCCUR IN SOME OF THE MORE PERSISTENT STORMS.
CONVECTION WILL HOLD OFF UNTIL LATE MORNING OR EARLY AFTERNOON WHEN
WE REACH OUR TRIGGER TEMPS...WITH HIGHEST AFTERNOON COVERAGE MAINLY
IN THE SCATTERED RANGE...FROM 30 POPS NEAR THE COAST TO 50 POPS FAR
INLAND. DESPITE PARTLY TO MOSTLY CLOUDY SKY CONDITIONS...WARM
ADVECTION AND A STRETCHING OF THE LOW LEVEL THICKNESS WILL GENERATE
MAX TEMPS WITHIN A DEGREE OR TWO EITHER SIDE OF 90 INLAND FROM THE
INTRA-COASTAL WATERS.

MONDAY NIGHT...ALTHOUGH THERE IS A RETURN TO THE CINH AS PER
SOUNDINGS...GIVEN THAT THE SURF ACE TROUGH OR WARM FRONT WILL LIFT
THROUGH THE FORECAST AREA AND THERE IS SOME SHORT WAVE ENERGY
ALOFT...WE FEEL THAT SLIGHT CHANCE AND CHANCE POPS ARE JUSTIFIED
DESPITE THE NOCTURNAL ENVIRONMENT. OUR GRIDS WILL SHOW THE GREATEST
POPS ALONG THE NW RANGE OF THE CWFA DURING THE EVENING...THEN
TRANSITIONING TO OVER THE CHARLESTON TRI-COUNTY ZONES LATE AT NIGHT
IN PROXIMITY TO THE SURFACE FEATURE. MINIMUM TEMPS WILL BE NEAR OR
SLIGHTLY ABOVE NORMAL.

TUESDAY THROUGH WEDNESDAY...THE LARGE SCALE PATTERN ACROSS THE NORTH
AMERICAN CONTINENT WILL BE HIGHLY AMPLIFIED AND SOMEWHAT PROGRESSIVE
THROUGH THE PERIOD. LOCALLY WE WILL LIE NEAR THE SOUTHERN REACHES OF
CYCLONIC FLOW OVER THE EASTERN UNITED STATES...WITH PERIODIC MID
LEVEL PERTURBATIONS TO PASS ON THROUGH. SIMULTANEOUSLY AT THE
SURFACE WE WILL FIND A COLD FRONT FROM NEW ENGLAND TO THE TENNESSEE
VALLEY ON TUESDAY THAT STRUGGLES TO PUSH SE THROUGH WEDNESDAY. THE
FRONT BECOMES ORIENTED MORE PARALLEL TO THE FLOW ALOFT...WHILE AT
THE SAME TIME WAVES OF LOW PRESSURE PREVENT THE FRONT FROM SHIFTING
SOUTH AND SE AT MORE THAN A CRAWL. PRESENTLY IT LOOKS LIKE WE WILL
REMAIN IN THE WARM SECTOR SOUTH OF THE FRONT THROUGH THE MIDDLE OF
THE WEEK...AWAITING THE FORMATION OF ONE LAST WAVE THAT CLOSES INTO
A LOW OFF THE NC COAST LATE WEDNESDAY OR WEDNESDAY NIGHT. THERE IS
AMPLE INSTABILITY AND MOISTURE TO PRODUCE AT LEAST SCATTERED
CONVECTION. THERMODYNAMICS ARE NOT OVERLY IMPRESSIVE IN REGARDS TO
SEVERE WEATHER...BUT AT THIS TIME OF YEAR THERE IS ALWAYS AT
LEAST AN ISOLATED RISK SHOULD ANY BOUNDARY INTERACTIONS RESULT IN
STRONGER UPDRAFTS. COMPRESSIONAL HEATING IN ADVANCE OF THE COLD
FRONT FRONT...AIDED BY A DEEP WESTERLY FLOW OFF THE APPALACHIANS
WILL ALLOW FOR MANY LOCATIONS TO PEAK AT OR ABOVE 90 EACH AFTERNOON.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
WITH THE CENTER OF UPPER LEVEL RIDGING REMAINING WELL WEST OF THE
REGION THROUGH THE PERIOD...THE PATTERN ALOFT WILL BE SOMEWHAT ILL
DEFINED AND PROGRESSIVE INTO AT LEAST LATE WEEK. THUS EXPECT
UNSETTLED CONDITIONS TO PERSIST INTO THE EXTENDED FORECAST
PERIOD...WITH FORECAST DETAILS QUITE UNCERTAIN DUE TO MODEL
INCONSISTENCIES. THE LINGERING FRONT OVER OR NEAR THE FORECAST
AREA...WHEN COMBINED WITH WEAK SHORTWAVE ENERGY EMBEDDED WITHIN
UPPER TROUGHING...WILL MAINTAIN DEEP MOISTURE AND CONVERGENCE TO
SUPPORT THUNDERSTORM CHANCES EACH DAY. MEDIUM RANGE MODELS DO
SUGGEST THAT THE SURFACE PATTERN WILL EVENTUALLY SETTLE TOWARD HIGH
PRESSURE TO THE NORTH AND A COASTAL TROUGH DEVELOPING ALONG THE
PERSISTENT FRONT TO THE SOUTH AND EAST. HIGH TEMPERATURES WILL VARY
LITTLE EACH AFTERNOON...REACHING THE UPPER 80S TO AROUND 90 DEGREES
AWAY FROM THE LOCALLY COOLER COASTLINE.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
00Z TAFS INDICATE PREVAILING VFR CONDITIONS THROUGH MONDAY. THERE
EXISTS A LOW PROBABILITY FOR MVFR CEILINGS AND/OR VISIBILITIES
LATE TONIGHT INTO MONDAY MORNING...INSUFFICIENT TO INCLUDE WITHIN
TAFS. THEN...A SHORTWAVE TROUGH WILL PUSH INTO THE REGION
MONDAY...AND DEEPENING MOISTURE WILL POOL OVER THE REGION
SUPPORTING AT LEAST SCATTERED SHOWERS/THUNDERSTORMS. ODDS FAVOR
THUNDERSTORMS IMPACTING BOTH TERMINALS AT SOME POINT MONDAY...BUT
SPECIFIC TIMING REMAINS IMPOSSIBLE TO PIN DOWN. CONSERVATIVELY
INCLUDED PROB30 GROUPS FOR THUNDERSTORMS 16-22Z AT KCHS AND 18-24Z
AT KSAV...BUT A SHOWER/THUNDERSTORM COULD OCCUR OUTSIDE OF THESE
TIME WINDOWS. ALSO...FLIGHT RESTRICTIONS WILL OCCUR WITHIN AND
CLOSE TO SHOWERS/THUNDERSTORMS...BUT MAGNITUDE/PERSISTENCE OF ANY
SUB-VFR CONDITIONS CANNOT BE FORECAST WITH ANY CONFIDENCE.

EXTENDED AVIATION...VFR CONDITIONS COULD PERIODICALLY GIVE WAY TO
FLIGHT RESTRICTIONS MONDAY NIGHT THROUGH THURSDAY IN ASSOCIATION
WITH SCATTERED TO NUMEROUS SHRA/TSRA.

&&

.MARINE...
TONIGHT...S/SE WIND REGIME WILL PERSIST AS HIGH PRESSURE REMAINS
CENTERED OFFSHORE. WINDS WILL BE NO HIGHER THAN 10-15 KT WITH SEAS
2-4 FT...HIGHEST BEYOND 40 NM.

MONDAY AND MONDAY NIGHT...THE LOCAL DOMAIN WILL BE PLACED WITHIN THE
WEST AND NW PORTION OF THE SUB-TROPICAL ATLANTIC RIDGE MONDAY THAT
GRADUALLY GIVES WAY TO A WEAK WARM FRONT OR SURFACE TROUGH THAT
PROGRESSES THROUGH MONDAY NIGHT. WHILE THERE WILL BE SOME INCREASE
IN WINDS WITH THE SEA BREEZE CIRCULATION MONDAY AFTERNOON AND WITH
NOCTURNAL LOW LEVEL JETTING MONDAY NIGHT...SOUTH AND SW WINDS WILL
GENERALLY HOLD UNDER 15-17 KT. SEAS AROUND 2-3 FEET MONDAY WILL RISE
ABOUT ANOTHER FOOT MONDAY NIGHT. ISOLATED TO SCATTERED CONVECTION
WILL FINALLY MAKE A RETURN TO THE COASTAL WATERS DURING THIS TIME.

TUESDAY THROUGH WEDNESDAY...THE QUASI-WARM FRONT OR SURFACE TROUGH
WILL LIFT NORTH OF THE MARINE COMMUNITY EARLY IN THE PERIOD...WHILE
WE FIND THE ATLANTIC RIDGE SUBDUED TO THE SOUTH. MEANWHILE...AN
UPSTREAM COLD FRONT WILL RELUCTANTLY MAKE A SE PUSH TOWARD THE
WATERS TUESDAY NIGHT AND WEDNESDAY. STILL TOO MUCH UNCERTAINTY AS TO
HOW FAR THE FRONT WILL BE ABLE TO PENETRATE...AS THE OCEANIC RIDGE
TO THE SOUTH AND SE ATTEMPTS TO HOLD FIRM. WE DO FEEL CONFIDENT THAT
WINDS AND SEAS WILL ASCEND TUESDAY AND TUESDAY NIGHT...WITH A
TIGHTENING OF THE PRESSURE GRADIENT BETWEEN THE UPSTREAM COLD FRONT
AND THE ATLANTIC HIGH. EVEN SO...ODDS AT THIS STAGE ARE AGAINST ANY
SMALL CRAFT ADVISORY CONDITIONS. WIND AND SEA CONDITIONS WILL THEN
BE DETERMINED BY WHERE THE FRONT ALIGNS ITSELF ON WEDNESDAY...BUT NO
MATTER WHERE IT IS LOCATED...ADVISORY HEADLINES ARE NOT ANTICIPATED.
MARINERS ARE ADVISED THAT AT LEAST SCATTERED CONVECTION WILL
OCCUR...AND WE/LL MAINTAIN A WEATHER WATCH FOR THE POSSIBLE
ORGANIZATION OF STRONGER STORMS MOVING OFF THE COAST IN ADVANCE OF
THE COLD FRONT.

THURSDAY THROUGH FRIDAY...THE FRONT LOOKS TO BECOME MORE DIFFUSE
NEAR OR JUST SE OF THE LOCAL WATERS...AS HIGH PRESSURE BUILDS OVER
NEW ENGLAND AND THE MID ATLANTIC REGION. WINDS AND SEAS WILL BE WELL
BELOW ANY CRITERIA FOR SMALL CRAFT ADVISORIES.

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...SPR
SHORT TERM...33
LONG TERM...WMS
AVIATION...SPR
MARINE...33/SPR