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Area Forecast Discussion

012
FXUS62 KCHS 201544
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1144 AM EDT SUN APR 20 2014

.SYNOPSIS...
LOW PRESSURE OFF THE GEORGIA COAST WILL GRADUALLY MOVE AWAY THROUGH
TONIGHT. HIGH PRESSURE WILL BRIEFLY BUILD INTO THE REGION MONDAY.
A WEAKENING COLD FRONT WILL PUSH THROUGH THE AREA TUESDAY NIGHT...
FOLLOWED BY HIGH PRESSURE AND WARMER TEMPERATURES THROUGH LATE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
THE NEARLY VERTICALLY STACKED SURFACE AND UPPER LOW IS NOW SITTING
ABOUT 200 MI SE OF CHARLESTON. A LARGE DEFORMATION AXIS REMAINS
ACROSS THE SOUTHEAST UNITED STATES ON THE WESTERN PERIPHERY OF THE
SYSTEM. WITH PLENTIFUL LOW-LEVEL MOISTURE...OVERCAST SKIES
PERSIST. PATCHY DRIZZLE OR LIGHT RAIN HAS BEEN OCCURRING FROM TIME
TO TIME THOUGH COVERAGE IS NOW QUITE LIMITED. FOR THE REMAINDER OF
THE DAY THE MAIN CHALLENGE CENTERS AROUND CLOUD COVER. AS THE
CYCLONE SHIFTS FARTHER FROM THE REGION...ISENTROPIC LIFT WILL
GRADUALLY WEAKEN AND LOW-LEVEL MOISTURE WILL SLOWLY THIN OUT AS
DRIER AIR SHIFTS IN FROM THE WEST. WE HAVE ALREADY SEEN SOME
BREAKS IN THE CLOUDS OVER CHARLESTON AS WELL AS FAR INLAND
SOUTHEAST GA THOUGH THEY TEND TO FILL BACK IN WITH STRATOCUMULUS
WHEN WARM POCKETS FORM. NEAR-TERM GUIDANCE STILL SHOWS
CONSIDERABLE ISENTROPIC LIFT THROUGH THE AFTERNOON WHICH SUPPORTS
CONTINUED MOSTLY CLOUDY SKIES. HOWEVER THERE WILL LIKELY TO
CONTINUE TO BE BREAKS DEVELOPING...WHICH WILL LET TEMPS RISE INTO
THE 60S MOST LOCATIONS.

SKIES WILL GRADUALLY CLEAR LATER TONIGHT AS IMPACTS FROM LOW PRES
FADE OFFSHORE. THE TIMING OF CLEARING WILL DEFINE HOW COOL IT
EVENTUALLY GETS BY DAYBREAK. GIVEN LARGE DIFFERENCES IN SOME OF
THE MOS GUIDANCE... WE MAINTAINED LOW TEMPS AS-IS FOR TONIGHT.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
MONDAY...A WEAK SURFACE RIDGE OF HIGH PRESSURE SHOULD BUILD IN FOR
MONDAY...PROVIDING MUCH MORE SUNSHINE THAN RECENT DAYS....ESPECIALLY
IN THE AFTERNOON. MODEL SOUNDINGS SHOWS SOME MOISTURE TRAPPED
BELOW THE INVERSION FOR ALL AREAS DURING AT LEAST THE FIRST PART OF
THE MORNING...SO EXPECT AT LEAST SOME EARLY MORNING STRATUS.
AFTERNOON TEMPERATURES SHOULD CLIMB INTO THE LOWER TO MID 70S AWAY
FROM THE COAST.

MONDAY NIGHT...WEAKENING SURFACE HIGH PRESSURE WILL SETTLE SOUTH
INTO THE GULF COAST STATES...ALLOWING FOR A WEAK RETURN FLOW FROM
THE SOUTHWEST TO DEVELOP. SOME HIGH LEVEL CLOUDS WILL BE ON THE
INCREASE...ESPECIALLY LATE. TEMPS WILL BE A BIT MILDER THAN THE
NIGHT BEFORE AS WELL...MAINLY IN THE LOWER TO MID 50S.

TUESDAY AND TUESDAY NIGHT...A QUICK MOVING UPPER LEVEL DISTURBANCE
WILL SWING THROUGH THE SOUTHEASTERN STATES DURING THE AFTERNOON
AND EVENING HOURS. A  WEAKENING SURFACE COLD FRONT ACCOMPANYING
THE DISTURBANCE WILL MOVE THROUGH MOST AREAS DURING THE EVENING AND
OVERNIGHT HOURS. SOUTHWESTERLY WINDS AHEAD OF THE FRONT ON TUESDAY
WILL ALLOW FOR SOME LOW LEVEL WARM ADVECTION...WITH TEMPERATURES
CLIMBING TO NEAR 80 AT MOST LOCATIONS AWAY FROM THE COOLER OCEAN
WATERS. THERE IS A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS DURING
THE AFTERNOON AND EVENING HOURS ALONG AND AHEAD OF THE FRONT.
SOME WEAK INSTABILITY MAINLY WITH LIS FROM -1 TO -3 AND CAPE VALUES
AOB 500 J/KG COULD BE IN PLACE ACROSS AT LEAST PORTIONS OF THE CWA
BY LATE AFTERNOON IN ADVANCE OF THE FRONT. HOWEVER...ONLY WEAK
CONVERGENCE ALONG THE FRONT AND FAIRLY LOW PRECIPITABLE WATER VALUES
NEAR 1.25 INCHES PRECLUDE THE INCLUSION OF ANY HIGHER POPS AT THE
PRESENT TIME. IN FACT...WOULD NOT BE SURPRISED IF UPSTREAM
CONVECTION LOCATED IN A SLIGHTLY MORE UNSTABLE AIRMASS WEAKENS OR
DISSIPATES AS IT MOVES INTO THE AREA LATER TUESDAY AND TUESDAY
EVENING.

.WEDNESDAY...WEAK SURFACE HIGH PRESSURE WILL BUILD IN BEHIND THE
FRONT. SUNNY SKIES HIGHS ON WEDNESDAY WILL ALLOW AFTERNOON
TEMPERATURES TO CLIMB INTO THE MID AND UPPER 70S IN THE NORTH TO
NEAR 80 IN THE SOUTH.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL BUILD OVER THE SOUTHEAST
THROUGH THURSDAY SUPPORTING RAIN-FREE CONDITIONS AND HIGH
TEMPERATURES RANGING FROM THE UPPER 70S TO LOWER 80S THURSDAY. AS A
SURFACE RIDGE OF HIGH PRESSURE SHIFTS OFFSHORE FRIDAY THROUGH
SUNDAY...TEMPERATURES IN THE LOWER TO MID 80S WILL BE COMMON AWAY
FROM THE IMMEDIATE COAST. WITH MODERATE INSTABILITY EXPECTED FRIDAY
AND SATURDAY...INCLUDED A SLIGHT CHANCE FOR AFTERNOON THUNDERSTORMS.

&&

.AVIATION /16Z SUNDAY THROUGH THURSDAY/...
IFR CONDITIONS WILL PREVAIL AT BOTH TERMINALS THROUGH MID TO LATE
MORNING...AS A STRONG INVERSION REMAINS IN PLACE AND TRAPS CONSIDERABLE
MOISTURE UNDERNEATH. DUE TO THE PROXIMITY OF A SURFACE LOW OFF THE
SE COAST...SHOWERS WERE BANDING AROUND KCHS WITH ONLY SPOTTY DRIZZLE
AROUND KSAV EARLY THIS MORNING. CIGS SHOULD VERY SLOWLY LIFT TO
MVFR AT BOTH SITES TODAY THEN MVFR CIGS INTO THIS EVENING...LIFTING
TOWARD THE END OF 06Z TAF CYCLE. A BREEZY DAY ON TAP AT BOTH
TERMINALS AS A TIGHT GRADIENT LINGERS. NORTH FLOW WILL LIKELY GUST
INTO THE 20-25 KT RANGE. TONIGHT...MODELS HANDLE LOW LEVEL
MOISTURE TRAPPED BELOW THE INVERSION DIFFERENTLY AND MVFR
CONDITIONS COULD LINGER MUCH OF THE NIGHT AT KCHS WHICH THE 06Z
NAM STRONGLY SUGGEST. CHANCES ARE GOOD THAT MVFR CIGS LINGER
THROUGH THE COASTAL CORRIDOR BETWEEN 06Z AND 12Z MONDAY.

EXTENDED AVIATION OUTLOOK...OTHER THAN PERHAPS A BRIEF PERIOD OF
MVFR CIGS EARLY MONDAY...VFR CONDITIONS ARE EXPECTED TO CONTINUE
INTO TUESDAY. THERE IS A SMALL CHANCE OF SOME IFR/MVFR CONDITIONS IN
CONVECTION LATE TUESDAY OR TUESDAY NIGHT...WITH CONDITIONS IMPROVING
BACK TO VFR BY WEDNESDAY.

&&

.MARINE...
NEAR-DAWN SURFACE ANALYSIS INDICATES AN IMPRESSIVE PRES GRADIENT
OFF THE GRAND STRAND OF SOUTH CAROLINA NORTHWARD OVER THE SE NORTH
CAROLINA WATERS. THE GRADIENT OVER OUR WATERS WAS TIGHT BUT NOT
NEARLY AS PACKED. STRONGEST FLOW TONIGHT IS EXPECTED TO BE SEAWARD
FROM CHARLESTON BUOY SIX TOWARD THE EDISTO BUOY. WE RAISED A GALE
WARNING FOR AMZ360 ALONG CHARLESTON COUNTY...MAINLY FOR CONDITIONS
ACROSS THE NE PORTION OF THE MARINE ZONE. THE GALE WARNING ALSO
CONTINUES FOR GEORGIA WATERS BEYOND 20 NM.

NEAR SHORE WATERS SHOULD END UP WITH A HIGHER END SMALL CRAFT
ADVISORY DAY WITH 20-30 KT FLOW AND OCCASIONAL GUSTS ABOVE 30
KT. AS THE LOW PULLS FURTHER AWAY TONIGHT...GRADUAL IMPROVEMENT IS
EXPECTED BUT CONDITIONS ARE STILL LIKELY TO EXCEED ADVISORY
CRITERIA...ESPECIALLY WITH RESPECT TO SEA HEIGHTS. SPEAKING OF
SEAS...THE OFFSHORE LOW AND NE FETCH WILL GENERATE 10 FT PLUS
SEAS OUT CLOSER TO THE GULF STREAM THROUGH THIS EVENING...THEN
SLOWLY SUBSIDE TONIGHT. NEAR SHORE SEAS AVERAGING 5-7 FT WITH A
ROUGH 4 TO 5 FT WAVE VERY NEAR SHORE AND 7-9 FT WELL EAST OF
CHARLESTON TODAY...SLOWLY COMING DOWN LATER TONIGHT.

WINDS WILL CONTINUE TO DECREASE ON MONDAY..WITH SEAS SLOWLY
DECREASING AS WELL. CURRENTLY FORECASTING SMALL CRAFT ADVISORY
CONDITIONS...MAINLY DUE TO SEAS...DURING MUCH OF MONDAY MORNING FOR
AMZ350 AND INTO THE MONDAY EVENING FOR AMZ374.

AFTER A RELATIVELY QUIET MONDAY NIGHT...WINDS WILL TURN TO THE
SOUTHWEST AND INCREASE INTO THE 12 TO 15 KNOT RANGE TUESDAY AND
CONTINUE INTO TUESDAY NIGHT. SEAS WILL INCREASE SOME...BUT SHOULD
REMAIN BELOW SCA LEVELS.

WEDNESDAY THROUGH FRIDAY WILL BE QUITE TRANQUIL WITH WINDS GENERALLY
AT OR BELOW 12 KNOTS AND SEAS MAINLY AOB 3 FEET.

&&

.TIDES/COASTAL FLOODING...
TIDES WILL CONTINUE TO RUN HIGH TODAY. THERE IS A SMALL CHANCE THAT
SHALLOW COASTAL FLOODING WILL OCCUR AROUND HIGH TIDE NEAR 1 AM MONDAY.
DEPARTURES WOULD HAVE TO BE OVER 1 FT...THAT MAY NOT BE ATTAINABLE...
BUT IT CERTAINLY COULD BE CLOSE.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT MONDAY FOR AMZ330-352-354.
     GALE WARNING UNTIL 11 PM EDT THIS EVENING FOR AMZ350.
     GALE WARNING UNTIL 6 AM EDT MONDAY FOR AMZ374.

&&

$$

SYNOPSIS...
NEAR TERM...JRL
SHORT TERM...MTE
LONG TERM...MTE
AVIATION...
MARINE...MTE
TIDES/COASTAL FLOODING...






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