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Area Forecast Discussion

887
FXUS62 KCHS 010955
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
455 AM EST SUN MAR 1 2015

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO WEDGE SOUTHWARD OVER THE REGION TODAY
WHILE A COASTAL TROUGH LINGERS OFF THE SOUTHEAST COAST. A COLD FRONT
WILL SHIFT OVER THE AREA LATE MONDAY THEN STALL JUST SOUTH OF THE
AREA MONDAY NIGHT AS HIGH PRESSURE BUILDS FROM THE NORTH. THE FRONT
WILL LIFT BACK NORTH AS A WARM FRONT TUESDAY AFTERNOON AHEAD OF A
COLD FRONT THAT SHIFTS THROUGH THE AREA LATE WEDNESDAY INTO THURSDAY.
HIGH PRESSURE WILL THEN BUILD OVER THE AREA THROUGH THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
PRE-DAWN...HIGH PRES WEDGED INTO GEORGIA AND THE CAROLINAS EARLY THIS
MORNING WITH A COASTAL TROUGH ALONG THE WEST WALL OF THE GULF STREAM.
AREAS OF LIGHT RAINS HAVE BEEN QUITE TRANSIENT OVERNIGHT AND MAINLY
NORTH OF I-16 BUT A STEADY STREAM OF ISENTROPIC ASCENT SHOULD ENSURE
PERIODIC WET WEATHER FOR MUCH OF THE FORECAST AREA AS ISENTROPIC
ASCENT IS MAINTAINED ACROSS A DEEP THERMAL SURFACE. AT THE GROUND
LEVEL...SURFACE PRESSURES WERE FALLING ACROSS THE AREA...A SIGN
THAT THE STRENGTH OF THE WEDGE HAS PEAKED. CLOUDS WERE LOWERING AS
WARM AIR ADVECTION INCREASES ATOP THE BOUNDARY LAYER. TEMPS WERE
CHILLY ONCE AGAIN WITH READINGS IN THE UPPER 30S INLAND TO LOWER
40S ALONG THE COAST.

WHILE CLOUDY/COOL AND OCCASIONALLY DAMP WEATHER WILL BE THE MAIN
WEATHER FEATURES TO RING IN THE MONTH OF MARCH...THE MAIN FORECAST
QUEST TODAY WILL BE FORECASTING THE DIURNAL TEMP CURVE ALONG WITH
HIGH TEMPS IN A STUBBORN WEDGE PATTERN WITH THE COASTAL TROUGH
UNLIKELY TO PUNCTUATE THE VERY CHILLY NEAR SHORE SHELF WATERS.
EVEN THOUGH WE WILL KEEP THE WARM FRONT OFF THE COAST...QUITE A
FEW OF THE MODELS RESPECT THE 14C BOUNDARY LAYER TEMPS ADVECTING
OVER THE COASTAL EROSION OF THE SHALLOW COLDER AIR MASS AND
SUGGEST LATE AFTERNOON TEMPS ALONG AND EAST OF U.S. 17 WILL
EVENTUALLY REBOUND LATE AS SURFACE WINDS BECOME LIGHT AND PERHAPS
VARIABLE. THE 13 KM RAP AND ECMWF BOTH SHOW A VERY NARROW SLOT OF
NEAR 60 DEGREE SURFACE TEMPS JUST INLAND FROM THE BEACHES AROUND
NORTH CHARLESTON AND WHILE NOT FAR INLAND COULD BE LOCKED IN TO
LOWER TO MID 40 DEGREE AIR AT THE SURFACE. A THERMAL GRADIENT
THAT SIGNIFICANT IS NOT TOTALLY OUT OF THE QUESTION BUT WE OPTED
JUST TO TIGHTEN THE TEMP GRADIENT THIS AFTERNOON JUST A BIT WITH
PLENTY OF MESOSCALE UNCERTAINTIES INCLUDING RAINFALL COVERAGE.
RAINFALL AMOUNTS SHOULD GENERALLY BE LIGHT AND LESS THAN A QUARTER
INCH FOR THE MOST PART.

WIDESPREAD LOW CLOUDS WILL BLANKET THE REGION GOING INTO TONIGHT
WITH STRATUS POTENTIALLY BUILDING DOWN ENOUGH TO BE A CONCERN FOR
DENSE FOG IN SOME AREAS TONIGHT AS SIGNIFICANT DRYING ADVECTS NE
INTO THE 925-850 MB LAYER. WE HAVE FAIRLY LOW CONFIDENCE AT THIS
JUNCTURE BUT ENOUGH TO JUSTIFY UPGRADING PATCHY FOG TO AREAS OF
FOG AS A TREND. THERE WILL PROBABLY BE PATCHY DRIZZLE AROUND THE
REGION TONIGHT GIVEN FORECAST SOUNDING PROFILES AND THE SYNOPTIC
OVERVIEW. LOW TEMPS MAINLY 40 TO 45 DEGREES BUT READINGS MANY BE
STEADY OR RISING LATE.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY/...
MONDAY...A BRIEF WARMUP WILL OCCUR IN ADVANCE OF A COLD FRONT THAT
APPROACHES FROM THE NORTH LATE IN THE DAY. TEMPS SHOULD PEAK IN THE
MID 60S NORTH TO AROUND 70 SOUTH OF INTERSTATE 16 IN SOUTHEAST
GEORGIA. SLIGHT CHANCES OF SHOWERS ARE POSSIBLE AHEAD OF THE
FRONT...FOLLOWED BY CHANCES OF SHOWERS AS THE FRONT STALLS JUST
SOUTH OF THE AREA MONDAY NIGHT. PRECIP COVERAGE SHOULD REMAIN
HIGHEST IN NORTHERN AREAS THROUGH THE OVERNIGHT PERIOD. LOW TEMPS
WILL BE WARMER THAN THE PREVIOUS NIGHT...IN THE UPPER 40S NORTH TO
LOW/MID 50S IN SOUTHEAST GEORGIA.

TUESDAY...HIGH PRESSURE WILL WEDGE SOUTHWARD INTO THE AREA
EARLY...BEFORE A STATIONARY FRONT LIFTS NORTH AS A WARM FRONT DURING
THE AFTERNOON. CHANCES OF SHOWERS WILL BE POSSIBLE NORTH OF THE
FRONT...BEFORE MOST PRECIP SHIFTS TO OUR NORTH TUESDAY NIGHT. HIGH
TEMPS WILL BE LARGELY DEPENDENT ON THE POSITION OF THE WARM FRONT
OVER THE COURSE OF THE DAY. CLOUD COVER AND A FEW SHOWERS WILL ALSO
POSE SOME LIMITING FACTORS AS TO HOW WARM CONDITIONS WILL GET DURING
TYPICAL PEAK HEATING HOURS. AT THIS TIME...HAVE MAINTAINED TEMPS IN
THE LOW/MID 60S FOR MOST AREAS...WITH PERHAPS SOME LOW 70S FOR
LOCATIONS SOUTH OF INTERSTATE 16 IN SOUTHEAST GEORGIA.

WEDNESDAY...STRONG WARM AIR ADVECTION WILL OCCUR AS SOUTHERLY FLOW
STRENGTHENS OVER THE SOUTHEAST UNITED STATES WELL AHEAD OF A COLD
FRONT APPROACHING FROM THE WEST LATE WEDNESDAY NIGHT. BREAKS IN
CLOUD COVER AS WELL AS SOME COMPRESSIONAL HEATING SUPPORT THE
WARMEST TEMPS OF THE WEEK...WITH HIGH TEMPS IN THE MID/UPPER 70S
OVER MOST AREAS BEFORE THE ONSET OF SHOWERS LATE WEDNESDAY
AFTERNOON/EVENING.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A COLD FRONT WILL APPROACH WESTERN ZONES WEDNESDAY NIGHT WITH MAINLY
SHOWERS. HOWEVER...STRONG FORCING WILL BE ASSOCIATED WITH THE
FRONT...SUPPORTING THE NEED FOR A FEW THUNDERSTORMS OVER INLAND
AREAS EARLY WEDNESDAY NIGHT. THE COLD FRONT WILL THEN CONTINUE TO
PUSH THROUGH THE AREA EARLY THURSDAY...WITH GREATEST COVERAGE OF
SHOWERS THURSDAY MORNING AND AFTERNOON. MOST SHOWERS WILL THEN SHIFT
OFFSHORE THURSDAY NIGHT INTO EARLY FRIDAY AS COOLER HIGH PRESSURE
BUILDS BEHIND THE FRONT. THURSDAY AND FRIDAY NIGHT LOW TEMPS SHOULD
BE THE COOLEST OF THE WEEK...IN THE MID/UPPER 30S. AFTERNOON HIGHS
WILL ONLY BE IN THE LOW/MID 50S INTO THE WEEKEND. HIGH PRESSURE
SHOULD PREVAIL THROUGH THE WEEKEND...BUT THERE ARE INDICATIONS THAT
SOME SHOWERS COULD DEVELOP MAINLY ALONG THE COAST AS A SFC LOW
DEVELOPS OFFSHORE AND DEEPENS WHILE LIFTING TO THE NORTH/NORTHEAST.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
BOTH AIRFIELDS HAD MVFR CEILINGS AT 09Z...WHICH WILL GRADUALLY
LOWER INTO THE IFR RANGE IN A FEW HOURS...THEN PERSIST THROUGH
THE REMAINDER OF THE VALID CYCLE. THIS IS THE RESULT OF ABUNDANT
MOISTURE TRAPPED BENEATH THE WEDGE INVERSION...AIDED BY ISENTROPIC
LIFT AT VARIOUS LEVELS. PERIODIC LIGHT RAINS OR EVEN DRIZZLE AT
TIMES LIKELY TODAY WITH FOG POTENTIALLY AN ISSUE TONIGHT AS THE
LOW CLOUDS BUILD DOWN WITH STRONG WARM AIR ADVECTION ABOVE THE
COOLER SURFACE TEMPS WITH A DRYING TREND IN THE 3-5 KFT LAYER.
THEE 00Z-06Z MONDAY PORTION OF THE TAFS...CONFIDENCE IS VERY GOOD
THAT LIFR CIGS AND PERHAPS IFR VSBYS WILL PREVAIL GIVEN LATEST
MODEL DATA.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED MONDAY. A
BACKDOOR COLD FRONT COULD PRODUCE A ROUND OF FLIGHT RESTRICTIONS
MONDAY NIGHT AND THEN AGAIN ON TUESDAY AS IT RETURNS AS AS WARM
FRONT. VFR CONDITIONS SHOULD RETURN ON WEDNESDAY...BEFORE ANOTHER
ROUND OF FLIGHT RESTRICTIONS OCCURS WEDNESDAY NIGHT INTO THURSDAY
AS A COLD FRONT SHIFTS THROUGH THE AREA.

&&

.MARINE...
HIGH PRESSURE WILL WEDGE INLAND ON TODAY WHILE A COASTAL TROUGH
LIFTS NORTH ALONG THE SOUTHEAST COAST. A STRONG PRESSURE GRADIENT
BETWEEN THESE TWO FEATURES IS FORECAST TO DECREASE THROUGH THE
MORNING WITH A MUCH LIGHTER GRADIENT BY LATER TODAY AND TONIGHT.
IT WILL DIFFICULT TO TURN DIRECTIONS AWAY FROM A NORTHERLY COMPONENT
GIVEN THE STABLE CHILLY SHELF WATERS BUT THEY COULD BECOME MORE NW
TO N LATER TONIGHT. SEAS SHOULD FALL BELOW 5 FT TONIGHT EXCEPT
OVER OUTER GEORGIA WATERS WHERE ELEVATED SEAS WILL MAINTAIN
ADVISORY LEVELS UNTIL AT LEAST LATE IN THE NIGHT. STRATUS CLOUDS
COULD LOWER TO 1-2 HUNDRED FT OVER COOL STABLE WATERS ALONG THE
LAND/SEA INTERFACE OVERNIGHT. WE INCLUDED AREAS OF FOG AS VSBYS
LIKELY WILL BE LOWERED AT LEAST SOMEWHAT BY LOWER CEILINGS.

MONDAY AND TUESDAY...WINDS/SEAS SHOULD REMAIN BELOW ADVISORY LEVELS
AS A COLD FRONT APPROACHES FROM THE NORTH ON MONDAY...THEN STALLS
JUST SOUTH OF THE COASTAL WATERS MONDAY NIGHT. HOWEVER WE COULD SEE
WINDS BETWEEN 15-20 KT OVER NORTHERN SC WATERS LATE. THE FRONT WILL
THEN LIFT BACK NORTH AS A WARM FRONT TUESDAY AFTERNOON WITH DEWPTS
THAT APPROACH THE UPPER 50S TO AROUND 60 LATE IN THE DAY. SEA FOG
COULD BE AN ISSUE...MAINLY OVER SOUTHERN WATERS TUESDAY NIGHT.

WEDNESDAY THROUGH SATURDAY...GREATEST CHANCES OF SEA FOG WILL BE
POSSIBLE ON WEDNESDAY AND THURSDAY AS DEEP MOISTURE ADVECTS OVER
COOLER WATERS AHEAD A COLD FRONT. WINDS AND SEAS WILL ALSO GRADUALLY
INCREASE/BUILD AHEAD OF THE FRONT...LIKELY SUPPORTING THE NEED FOR
SOLID SMALL CRAFT ADVISORIES THURSDAY EVENING INTO FRIDAY AS THE
COLD FRONT SHIFTS OVER THE WATERS AND IS FOLLOWED BY COLDER HIGH
PRESSURE. CONDITIONS SHOULD SLOWLY IMPROVE LATE WEEKEND AS THE
PRESSURE GRADIENT BECOMES MORE RELAXED OVER COASTAL WATERS.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR AMZ350-
     352-354.
     SMALL CRAFT ADVISORY UNTIL 5 AM EST MONDAY FOR AMZ374.

&&

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



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