Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 242118
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
418 PM EST MON NOV 24 2014

.SYNOPSIS...
A SLOW MOVING COLD FRONT WILL SHIFT INTO THE AREA TONIGHT AND
STALL JUST OFF THE COAST TUESDAY. AN AREA OF LOW PRESSURE WILL
DEVELOP OFF THE GEORGIA COAST TUESDAY AFTERNOON AND LIFT NORTHEAST
TUESDAY NIGHT. DRY HIGH PRESSURE WILL BUILD INTO THE SOUTHEAST
UNITED STATES WEDNESDAY THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
A HUGE AND DEEPENING LARGE SCALE TROUGH COVERING MUCH OF THE
CONUS WILL PREVAIL TONIGHT...WITH A BLOCKING ANTICYCLONE OVER THE
SW ATLANTIC. WE/RE SITUATED BETWEEN THESE 2 FEATURES WITH A DEEP
AND EXTREMELY MOIST SW FLOW TO PREVAIL. THIS WILL CONTINUE TO DRAW
CONSIDERABLE SUB-TROPICAL AND TROPICAL MOISTURE FROM OUT OF THE
GULF OF MEXICO WITH PWATS NEAR OR ABOVE 2 STANDARD DEVIATIONS
ABOVE NORMAL. AT THE SURFACE IS A SLUGGISH MIGRATING COLD FRONT
THAT IS BEING HELD UP BY THE ALIGNMENT WITH THE FLOW ALOFT AND
ALSO RUNNING INTO A STAGNANT ATLANTIC SUB-TROPICAL RIDGE TO THE SE
THAT REFUSES TO BUDGE.

ALTHOUGH SHEAR PARAMETERS ARE STILL IMPRESSIVE WITH 45-55 KT 0-6KM
BULK SHEAR...OUR THERMODYNAMICS ARE DIMINISHING DUE TO THE
EXTENSIVE CLOUD COVER AND EARLIER RAINS WHICH HAVE DROPPED TEMPS
CONSIDERABLY. IN RESPONSE TO THIS WE HAVE SEEN AN EXPANSION AND
STRENGTHENING OF CINH WHICH ACCORDING TO LATEST MESO-ANALYSIS
REVEALS THAT IT IS COVERING MUCH OF THE CWFA. IN ADDITION LAPSE
RATES ARE PUNY AND THE LFC HAS RISEN GREATLY SINCE PEAK HEATING.
THUS OUR SEVERE RISK IS FADING AND WE WILL REMOVE MENTION FROM THE
HAZARDOUS WEATHER OUTLOOK. HOWEVER THERE IS STILL THE RISK FOR AN
ISOLATED STRONG OR SEVERE STORM...ESPECIALLY SOUTH OF I-16 IN SE GA
THROUGH THIS EVENING.

ALTHOUGH THE LOW LEVEL JET STARTS TO PULL AWAY...WE/LL BE SITUATED
NEAR THE FAVORABLE RIGHT ENTRANCE REGION OF A POWERFUL UPPER JET
WITH WINDS IN EXCESS OF 160 OR 170 KT THAT BECOMES ORIENTED NE-SW
THROUGH THE OHIO VALLEY TO THE LOWER MS VALLEY LATE. THIS ALONG
WITH INCREASING ISENTROPIC UPGLIDE AND THE COLD FRONT NOW NOT
SCHEDULED TO ARRIVE UNTIL VERY LATE TONIGHT...WILL HAVE
CONSIDERABLE MOISTURE TO WORK WITH.

A BAND OF SHOWERS WITH A FEW T-STORMS THIS EVENING WILL OCCUR
MAINLY NEAR AND WEST OF I-95...ALTHOUGH THE BULK OF THE T-STORMS
WILL BE ELEVATED GIVEN THE EXPANSION OF THE CINH AND NOCTURNAL
STABILIZING INFLUENCES. THEN FOR MIDNIGHT AND BEYOND IT LOOKS LIKE
ADDITION RENEWED SHOWERS WILL FORM AS THE COLD FRONT DRAW CLOSER
AND THE ISENTROPIC ASCENT INCREASE. WHILE WE MIGHT BE A LITTLE
CONSERVATIVE ON POPS...UNTIL WE/RE SURE ON TRENDS WE HAVE LIMITED
POPS TO 50-60 PERCENT.

WE TIED A RECORD MAX AT KSAV EARLIER TODAY AT 83 DEGREES...BUT
LOOKS LIKE WE FELL SHORT AT KCHS AND KCXM. TEMPS WILL REMAIN WARM
IN ADVANCE OF THE COLD FRONT AND GIVEN THAT THE FORECAST NOW SHOWS
A DELAY IN THE FRONT MAKING IT IN...WE HAVE RAISED TEMPS SEVERAL
DEGREES FROM THE PREVIOUS FORECAST. ACTUAL LOWS WILL MOST LIKELY
OCCUR AFTER 12Z...AND WILL AVERAGE SOME 10-15 DEGREES ABOVE NORMS
FOR LATE NOVEMBER.

ONE FINAL CONCERN WILL BE THE DEVELOPMENT OF FOG...RESULTING FROM
THE LOWERING OF THE WIDESPREAD STRATUS DECKS OVER THE SATURATED
GROUNDS. SEA FOG IS STILL LURKING JUST OFF THE COAST IN PARTS OF
THE AREA AND WILL ALSO BECOME INVOLVED. BUT SINCE THE FLOW VEERS
TO SW AND WEST...MOST OF THE SEA FOG SHOULD STAY OFFSHORE OR
IMPACT ONLY THE CHARLESTON COUNTY COAST.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
A POWERFUL LONGWAVE UPPER TROUGH DIGGING ACROSS THE CENTRAL UNITED
STATES ON TUESDAY WILL YIELD IMPRESSIVE DYNAMICS ACROSS THE LOCAL
AREA AND ANOTHER ROUND OF RAINFALL. AT THE TOP OF THE TROPOSPHERE A
150-200 KT JET STREAM WILL STRETCH FROM LOUISIANA TO NEW ENGLAND
WITH A BROAD SWATH OF UPPER LEVEL DIVERGENCE OVERSPREADING THE
SOUTHEAST STATES TUESDAY AND TUESDAY NIGHT. AT MID LEVELS A POTENT
SHORTWAVE TROUGH IS EXPECTED TO LIFT OUT OF THE CENTRAL GULF COAST
REGION TUESDAY EVENING AND INTO THE CAROLINAS ON WEDNESDAY. AHEAD OF
THE SHORTWAVE AN ANOMALOUSLY MOIST AIR MASS WILL CONTINUE TO SURGE
INTO THE AREA WITH PWATS 1.5-1.8". THE COLD FRONT WILL BE STALLED
JUST OFF THE COAST AT DAYBREAK TUESDAY. AS THE UPPER TROUGH
APPROACHES...A WAVE OF LOW PRESSURE IS EXPECTED TO DEVELOP AND
STRENGTHEN ALONG THE FRONT JUST OFF THE GA COAST. SYNOPTIC SCALE
MODELS ARE IN VERY GOOD AGREEMENT THAT THIS LOW WILL CLOSE OFF AND
INTENSIFY JUST OFF THE SC/GA COAST TUESDAY EVENING BEFORE LIFTING
RAPIDLY NORTHEAST LATE TUESDAY NIGHT.

LIGHT TO MODERATE RAIN WILL INCREASE IN COVERAGE ON TUESDAY AS THE
SYNOPTIC SCALE LIFT AND ISENTROPIC ASCENT RAMP UP TO THE LEE OF THE
STALLED FRONT. TEMPERATURES WILL REMAIN STEADY OR SLOWLY FALL
THROUGH THE DAY AS SOME COOLER AIR WRAPS IN BEHIND THE FRONT AND
RAIN FALLS INTO THE BOUNDARY LAYER. LATE TUESDAY AFTERNOON THROUGH
TUESDAY NIGHT LOOK LIKE THE MOST INTERESTING PERIODS DUE TO THE
SURFACE LOW DEVELOPING OFF THE COAST. SEVERAL MODELS ARE SHOWING A
40-50 KT SSW LOW-LEVEL JET ENHANCING MOISTURE CONVERGENCE ACROSS THE
TRI-COUNTY AREA TUESDAY NIGHT...COINCIDENT WITH THE CLOSEST APPROACH
BY THE LOW. WITH ANOMALOUS PWATS FOR LATE NOVEMBER IN PLACE...HEAVY
RAINFALL IS POSSIBLE IN OUR FAR EASTERN ZONES TUESDAY NIGHT...SO WE
ADDED HEAVY RAINFALL TO THE FORECAST.

PRECIPITATION IS EXPECTED TO END QUICKLY FROM WEST TO EAST WEDNESDAY
MORNING ONCE THE SHORTWAVE PUSHES TO THE EAST AND SUBSIDENT WESTERLY
FLOW SETS UP. PARTIAL CLEARING IS ANTICIPATED IN THE AFTERNOON
ACROSS THE WESTERN HALF OF THE AREA...THOUGH WRAP AROUND MOISTURE
ACROSS SOUTH CAROLINA WILL MAINTAIN MOSTLY CLOUDY SKIES AND PERHAPS
SOME LIGHT RAIN. COLD ADVECTION WILL KEEP TEMPS IN THE 50S.

THURSDAY NIGHT LOOKS COLD AS THE CANADIAN HIGH BECOMES FIRMLY
ENTRENCHED. LOWS WILL BE IN THE MIDDLE 30S. THURSDAY WILL FEATURE A
MODEST WARM-UP DUE TO INCREASING DOWNSLOPE FLOW WITH HIGHS IN THE
LOWER 60S.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE REGION FROM THE
NORTH LATE THURSDAY...DESCENDING INTO THE SOUTHEAST STATES BY
FRIDAY...BEFORE GRADUALLY SHIFTING TOWARD THE COASTLINE AND NEARBY
ATLANTIC WATERS OVER THE WEEKEND. EXPECT TEMPERATURES TO SLOWLY
MODERATE AS A RESULT OF THE TRACK OF THE HIGH PRESSURE CENTER.
HIGH TEMPERATURES WILL ONLY REACH THE UPPER 50S FRIDAY...WHILE
PEAKING IN THE MID TO UPPER 60S BY EARLY NEXT WEEK. LOW
TEMPERATURES WILL ALSO REFLECT THIS WARMING TREND...RANGING FROM
THE LOW TO MID 30S THURSDAY AND FRIDAY NIGHTS...TO THE LOW TO MID
40S BY SUNDAY NIGHT. CONDITIONS APPEAR DRY THROUGH THE EXTENDED
PERIOD...AND WILL KEEP RAIN OUT OF THE FORECAST.

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/...
KCHS...A WEAKENING AND BROKEN BAND OF CONVECTION WILL BRUSH THE
TERMINAL THIS AFTERNOON...WITH NO WORSE THAN MVFR CONDITIONS.
WHILE THERE ARE STILL INDICATIONS THAT ANOTHER BAND WHICH IS
FORMING FURTHER TO THE WEST COULD ARRIVE THIS EVENING...WE FEEL
MORE CONFIDENT THAT CONVECTIVE RAINS WILL ARRIVE LATE TONIGHT AND
CONTINUE INTO TUESDAY AS A COLD FRONT MOVES INTO THE AREA AND
STALLS NOT FAR OFFSHORE. ANY IMPROVEMENT IN CONDITIONS EARLY
TONIGHT BACK TO VFR...WHICH IS NOT A GIVEN...WILL BE SHORT-
LIVED...AS FLIGHT RESTRICTIONS WILL AGAIN PREVAIL LATE TONIGHT
INTO TUESDAY. IF ANY FOG AND STRATUS BUILD- DOWN OCCURS WE COULD
BE WORSE THAN NOW IN THE 18Z TAF SET.

KSAV...SCATTERED SHRA WILL STILL IMPACT THE AIRFIELD THIS
AFTERNOON WITH NO WORSE THAN PERIODIC MVFR WEATHER TO OCCUR.
UNLESS ANOTHER BAND ORGANIZES AND MOVES IN THIS EVENING A BETTER
CHANCE FOR CONVECTIVE RAINS AND SHRA WILL BE OVERNIGHT INTO
TUESDAY AS THE COLD FRONT MOVES INTO AND THE AREA AND OFFSHORE.
CONDITIONS WILL BE MVFR OR LOWER FOR THE BULK OF THE TIME FROM
AROUND 06Z THROUGH THE END OF THE VALID TAF PERIOD...AND BEYOND.
LOOKS LIKE THE FEW HOURS OF EARLIER GUSTY WINDS HAS SUBSIDED NOW
THAT TEMPS HAVE DROPPED SEVERAL DEGREES.

EXTENDED AVIATION OUTLOOK...HIGH PROBABILITY FOR MVFR CEILINGS
TUESDAY AFTERNOON. MODERATE TO HIGH CHANCES FOR IFR CEILINGS
TUESDAY NIGHT INTO WEDNESDAY MORNING WITH OCCASIONAL VSBY
REDUCTIONS TO IFR/MVFR DUE TO RAIN TUESDAY AND TUESDAY NIGHT. VFR
AND BREEZY NW WINDS ON WEDNESDAY.

&&

.MARINE...
TONIGHT...THE ANTICYCLONIC FLOW AROUND THE SUB-TROPICAL ATLANTIC
RIDGE TO OUR SE WILL ATTEMPT TO HOLD ON THROUGH THE
NIGHT...DESPITE THE GRADIENT RELAXING AS A COLD FRONT LIMPS TOWARD
THE SE COAST LATE. SOUTH AND SW WINDS AT 12-18 KT WILL BE AT THEIR
HIGHEST THIS EVENING...THEN VEER SOME 20-50 DEGREES OVERNIGHT AS
SPEEDS DROP AROUND 3-6 KT. SEAS WILL ALSO PEAK EARLY ON AT 4-7 FT
AND HIGHEST ACROSS AMZ350-374 WHERE WE HAVE THE REMAINING SMALL
CRAFT ADVISORIES...THEN SEAS FALL ABOUT A FOOT OR SO OVERNIGHT. OF
ADDITIONAL CONCERN WILL BE SEA FOG AND THE LOWERING OF STRATUS
CLOUD DECKS. RECENT REPORTS AROUND THE REGION FROM VARIOUS SOURCES
INDICATE THAT THE FOG IS LOCALIZED IN NATURE. BUT WE CONTINUE TO
HAVE A LARGE SPREAD OF TEMPS BETWEEN THE COOLER WATERS AND WARMER
AIR...PLUS FAVORABLE TRAJECTORIES ALIGNED NEARLY PARALLEL TO THE
SST ISOTHERMS. WE CONTINUE TO SHOW PATCHY FOG WITH VSBYS AT 1-3 NM
IN THE FORECAST AND THERE IS ALSO A MARINE WEATHER STATEMENT IN
EFFECT TO ADDRESS THIS CONCERN.

THE COLD FRONT WILL STALL JUST OFF THE COAST TUESDAY MORNING. WITH A
STRONG UPPER TROUGH APPROACHING FROM THE WEST...A SURFACE LOW IS
EXPECTED TO STRENGTHEN ALONG THE FRONT JUST OFF THE GA COAST. WINDS
WILL BECOME NNE TUESDAY AFTERNOON AND THE GRADIENT WILL TIGHTEN
CONSIDERABLY. SMALL CRAFT ADVISORY CONDITIONS EXPECTED BY LATE IN
THE AFTERNOON ACROSS MUCH OF THE MARINE AREA...INITIALLY IN 25 KT
WIND GUSTS. WINDS INCREASE AND BEGIN TO BACK TO THE NNW OVERNIGHT AS
THE SURFACE LOW LIFTS NORTHEAST AND COLD AIR BEGINS TO DROP IN FROM
THE WEST. SOLID SMALL CRAFT ADVISORIES EXPECTED TUESDAY NIGHT
THROUGH WEDNESDAY WITH THE POSSIBILITY OF GALE CONDITIONS OVER THE
WARMER OFFSHORE GA WATERS. AT THIS POINT WE ARE SHOWING SOME 35 KT
WIND GUSTS OVER OUTER WATERS LATE TUESDAY NIGHT INTO WEDNESDAY
MORNING BUT WILL HOLD OFF ON A GALE WATCH DUE TO THE STRONGEST WINDS
OCCURRING IN THE 4TH PERIOD AND THE DURATION LIKELY BEING LIMITED.

WINDS AND SEAS WILL FALL BELOW ADVISORY THRESHOLDS BY THURSDAY...YET
COULD REMAIN SOMEWHAT ELEVATED AS THE GRADIENT REMAINS TIGHT ON THE
PERIPHERY OF BUILDING HIGH PRESSURE INLAND. CONDITIONS WILL IMPROVE
BY LATE WEEK INTO THE WEEKEND...AS THE SURFACE HIGH SHIFTS TOWARD THE
WATERS AND THE GRADIENT RELAXES.

&&

.CLIMATE...
RECORD HIGHS FOR 24 NOVEMBER...
KCHS...82 SET IN 1986 AND PREVIOUS.
KCXM...81 SET IN 1998.
KSAV...83 SET IN 1967. /TIED TODAY/

RECORD HIGH MINIMUMS FOR 24 NOVEMBER...
KCHS...63 SET IN 2001 AND PREVIOUS.
KCXM...66 SET IN 2001.
KSAV...65 SET IN 1979.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 AM EST TUESDAY FOR AMZ374.
     SMALL CRAFT ADVISORY UNTIL 2 AM EST TUESDAY FOR AMZ350.

&&

$$

NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
CLIMATE...








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