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Area Forecast Discussion

062
FXUS62 KCHS 211426
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1026 AM EDT THU MAY 21 2015

.SYNOPSIS...
A WEAK AREA OF LOW PRESSURE OVER THE CAROLINAS TODAY WILL MOVE
OFFSHORE TONIGHT DRAGGING A COLD FRONT THROUGH THE REGION. HIGH
PRESSURE WILL BUILD IN ON FRIDAY AND REMAIN THE PRIMARY FEATURE
THROUGH THE MIDDLE OF NEXT WEEK AS IT SITS OVER THE ATLANTIC.

&&

.NEAR TERM /THROUGH TONIGHT/...
LATE THIS MORNING...NO SIGNIFICANT CHANGES TO CURRENT FORECAST OR
FORECAST REASONING. WATER VAPOR IMAGERY SHOWS AN EMBEDDED
SHORTWAVE ALOFT QUICKLY MOVING THROUGH IN THE FAST WEST FLOW WITH
MUCH DRIER AIR IN THE MID/UPPER LEVELS NOW PUSHING INTO THE SOUTH
CAROLINA UPSTATE AND CENTRAL GEORGIA. MEANWHILE...SURFACE OBS SHOW
THE CENTER OF A SURFACE LOW SITTING UP AROUND THE SPARTANBURG AREA
WITH PLENTY OF SUNSHINE ACROSS MOST OF THE CAROLINAS. THE SURFACE
LOW WILL PUSH EASTWARD TODAY AND IT LOOKS LIKE THE BEST FOCUSING
OF FORCING AND LOW LEVEL CONVERGENCE WILL TAKE PLACE ACROSS
EASTERN NORTH CAROLINA. THERE IS A SMALL WINDOW FOR
SHOWER/THUNDERSTORM DEVELOPMENT CLOSER TO THE SANTEE
RIVER...BASICALLY FROM AROUND NOW THROUGH ABOUT 1 PM.
THEREAFTER...SOUNDINGS SHOW THE COLUMN DRYING RAPIDLY WITH WARMING
TEMPERATURES AROUND 800 MB. THE FORECAST REMAINS DRY AND THIS IS
SUPPORTED BY MODEL DATA OUTPUT. THE MAIN STORY WILL BE THE WARM
TEMPERATURES. LOW LEVEL FLOW WILL BE WESTERLY AND KEEP THE SEA
BREEZE PINNED ALONG THE COAST. LOW LEVEL THICKNESS VALUES SUPPORT
HIGHS AROUND 95/96 THIS AFTERNOON. AS SUCH...HIGHS HAVE BEEN
WARMED A DEGREE OR TWO AND SOLIDLY INTO THE MID 90S EVERYWHERE.
RECORD HIGHS ARE IN THE 98/99 DEGREE RANGE SO IT DOES NOT APPEAR
WE WILL THREATEN THOSE VALUES.

OVERNIGHT...THE DRYING WILL CONTINUE AND COOLER AIR WILL FILTER IN
UNDER MOSTLY CLEAR SKIES. LOWS WILL REACH CLOSE TO 60 DEGREES WELL
INLAND AND THE MID 60S ALONG THE U.S. 17 CORRIDOR.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
FRIDAY...AT DAYBREAK THE REGION WILL BE POSITIONED BETWEEN A
DEPARTING COLD FRONT AND HIGH PRESSURE BUILDING FROM THE NORTHWEST.
NORTH/NORTHEAST FLOW WILL BRING COOLER AND MUCH DRIER AIR INTO THE
AREA. A PRONOUNCED CAP NOTED IN MODEL SOUNDINGS AND PWATS UNDER AN
INCH WILL KEEP A DRY FORECAST IN TACT. HIGH TEMPERATURES WILL BE
SEVERAL DEGREES COOLER THAN PREVIOUS DAYS...RANGING FROM THE UPPER
70S/AROUND 80 IN THE NORTHERN ZONES TO THE MID 80S SOUTH. FRIDAY
NIGHT...MOSTLY CLEAR SKIES AND LIGHT WINDS WILL PROVIDE IDEAL
RADIATIONAL COOLING CONDITIONS. LOWS ARE EXPECTED TO BE IN THE UPPER
50S/LOW 60S AWAY FROM THE COAST WHERE LOWS WILL BE IN THE MID 60S.

THE SURFACE HIGH WILL SHIFT INTO THE ATLANTIC OVER THE
WEEKEND...WITH UPPER RIDGE BUILDING OVER THE SOUTHEAST. LARGE SCALE
SUBSIDENCE AND LACK OF ANY SIGNIFICANT MOISTURE WILL KEEP POPS
CAPPED BELOW 15 PERCENT. TEMPERATURES WILL MODERATE CLOSER TO NORMAL
WITH HIGHS MAINLY IN THE LOW/MID 80S AND LOWS IN THE LOW/MID 60S
AWAY FROM THE COAST.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
SURFACE HIGH PRESSURE WILL REMAIN ANCHORED OVER THE ATLANTIC
THROUGH MID WEEK. RAIN CHANCES WILL BE QUITE LIMITED AS STRONG
UPPER RIDGE HOLDS FIRM OVER THE SOUTHEAST...HOWEVER AN INCREASE IN
MOISTURE TOWARDS THE MIDDLE OF WEEK MAY ALLOW SOME ISOLATED
CONVECTION TO FIRE IN THE AFTERNOON ALONG THE SEA BREEZE. FORECAST
WILL FEATURE NO HIGHER THAN SLIGHT CHANCE POPS. TEMPERATURES WILL
BE ABOVE NORMAL FOR MUCH OF THE PERIOD.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS AT KCHS/KSAV THROUGH 12Z FRIDAY. GUSTY WINDS
UPWARDS OF 20 KT ARE EXPECTED THIS AFTERNOON AS DEEPER MIXING
DEVELOPS.

EXTENDED AVIATION OUTLOOK...VFR.

&&

.MARINE...
W TO SW SYNOPTIC FLOW WILL BACK TO PURE SW THIS AFTERNOON WITH
SPEEDS 15 KT OR LESS. IT SHOULD BECOME GUSTY ALONG A PINNED
RESULTANT SEA BREEZE IN COASTAL CHARLESTON COUNTY THIS AFTERNOON
AND WE MENTIONED SOME GUSTS TO NEAR 20 KT IN THE VICINITY OF THE
CHARLESTON HARBOR. COOLER AND DRIER AIR MOVING OVER THE WATERS
LATER TONIGHT WILL ENHANCE THE MEAN LOW LEVEL MIXING/JETTING
ENVIRONMENT AND GUIDANCE WAS NOW PAINTING 20 KT JETTING FLOW AT
GRAYS REEF AS WINDS VEER AHEAD OF A LATE NIGHT WIND SHIFT TO THE
NORTH. WE TRENDED A BIT HIGH ON WIND SPEEDS LATER TONIGHT TO
ACCOUNT FOR LATEST TRENDS. SEAS THROUGH TONIGHT MAINLY IN THE 2 TO
3 FT RANGE...INCREASING TO 3 TO 4 FT BEYOND 10-15 NM OFF THE COAST
LATE.

FRIDAY THROUGH TUESDAY...THE WATERS WILL BE POSITIONED BETWEEN A
DEPARTING COLD FRONT AND HIGH PRESSURE BUILDING IN FROM THE
NORTHWEST AT DAYBREAK FRIDAY. NORTHEAST WINDS OF 15-20 KT WILL
QUICKLY SUBSIDE IN THE MORNING AS THE HIGH PUSHES THE FRONT FURTHER
AWAY. THE HIGH WILL THEN SHIFT INTO THE ATLANTIC OVER THE
WEEKEND...VEERING WINDS TO THE EAST. A PINCHED PRESSURE GRADIENT
WILL RESULT IN A BRIEF SURGE IN WINDS AND SEAS SATURDAY NIGHT INTO
SUNDAY ESPECIALLY ACROSS THE OUTER GA WATERS...HOWEVER CONDITIONS
ARE EXPECTED TO REMAIN BELOW HEADLINE CRITERIA. ATLANTIC HIGH
PRESSURE WILL THEN PREVAIL THROUGH MID WEEK. SOUTH/SOUTHEAST WINDS
WILL BE 15 KT OR LESS WITH SEAS 2-4 FEET ON AVERAGE.

&&

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

&&

$$

NEAR TERM...BSH
SHORT TERM...ECT
LONG TERM...ECT
AVIATION...
MARINE...ECT



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