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Area Forecast Discussion

460
FXUS62 KCHS 020523
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
123 AM EDT TUE SEP 2 2014

.SYNOPSIS...
HIGH PRESSURE WILL PREVAIL INTO NEXT WEEKEND. A COLD FRONT WILL
STALL AND DISSIPATE NORTH OF THE REGION BY LATE WEEK...THEN A
STRONGER COLD FRONT COULD ADVANCE INTO THE REGION LATE IN THE
WEEKEND OR EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
CONVECTIVE DEBRIS CLOUDINESS WILL CONTINUE TO DISSIPATE THROUGH
THE REST OF THE OVERNIGHT HOURS. ANY RISK FOR ADDITIONAL SHOWERS
AND T-STORMS WILL STAY OUT OVER THE ATLANTIC WHERE BEST
BAROCLINICITY IS FOUND.

TEMPERATURES WILL FALL INTO THE LOWER TO MID 70S...SEVERAL DEGREES
WARMER THAN SEASONAL NORMALS. BARRIER ISLAND COMMUNITIES WILL
STRUGGLE TO EVEN DIP BELOW 80!

MODEL GUIDANCE IS ONCE AGAIN HINTING AT THE POTENTIAL FOR PATCHY
FOG DURING THE PRE-DAWN HOURS TUESDAY MORNING. HOWEVER...SREF AND
NAM VISIBILITY SOLUTIONS ARE RATHER CONSERVATIVE AND THUS PREFER
NOT TO MENTION FOG IN THE FORECAST AT THIS TIME. AREAS THAT
RECEIVED NOTABLE RAIN AND WHERE SKY COVER SCATTERS COULD HAVE THE
BEST CHANCE FOR SOME LIGHT FOG BEFORE DAYBREAK.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY/...
TUESDAY...BENEATH AN WEST/EAST ORIENTED MID/UPPER LEVEL RIDGE AND
ON THE WESTERN PERIPHERY OF ATLANTIC HIGH PRESSURE WILL SUPPORT
ANOTHER HOT/HUMID DAY FEATURING HIGHS IN THE MID/UPPER 90S AND
HEAT INDEX VALUES 100-105F AWAY FROM THE COAST. MAINTAINED SLIGHT
CHANCE POPS CLOSE TO THE COAST AS THE SEA BREEZE PUSHES INLAND AND
CHANCE POPS INLAND CLOSE TO A SURFACE TROUGH. 01/12Z GUIDANCE
SUGGESTS THAT CONVECTIVE COVERAGE COULD EVENTUALLY REQUIRE LOCALLY
GREATER POPS INLAND...BUT HIGHEST POPS ARE CAPPED AROUND 40
PERCENT DUE TO THE PRESENCE/INFLUENCE OF THE UPPER RIDGE. PWATS
AROUND 2 INCHES AND ERRATIC THUNDERSTORM PROPAGATION COULD SUPPORT
LOCALLY HEAVY RAIN. THE THERMODYNAMIC ENVIRONMENT SHOULD LIMIT THE
SEVERE POTENTIAL TO NOTHING MORE THAN A COUPLE OF BRIEF/PULSE
DAMAGING WIND EVENTS ESPECIALLY WHERE BOUNDARY INTERACTIONS OCCUR.

TUESDAY EVENING...CONVECTIVE ACTIVITY IS EXPECTED TO DIMINISH
QUICKLY WITH THE LOSS OF HEATING AND THE BULK OF THE OVERNIGHT IS
EXPECTED TO BE DRY. TEMPERATURES SHOULD BOTTOM OUT IN THE MID 70S
MANY AREAS...EXCEPT AROUND 80F AT THE COAST.

WEDNESDAY...A COLD FRONT WILL APPROACH THE REGION FROM THE
NORTH/NORTHWEST. THIS FRONT WILL EVENTUALLY STALL NORTH OF THE
REGION...BUT THE FRONTAL TROUGH WILL COMBINE WITH THE SEA BREEZE TO
SUPPORT AT LEAST ISOLATED/SCATTERED SHOWERS/THUNDERSTORMS ESPECIALLY
DURING THE AFTERNOON. PWATS AROUND 2 INCHES WILL ONCE AGAIN SUPPORT
LOCALLY HEAVY RAIN...WHILE THE SEVERE THREAT SHOULD REMAIN LOW.
OTHERWISE...HIGHS AT LEAST IN THE LOWER TO MID 90S AND HEAT INDEX
VALUES 100-105F WILL AGAIN PREVAIL OUTSIDE THUNDERSTORMS.

WEDNESDAY NIGHT...SOME GUIDANCE DEPICTS A NORMAL DIURNAL DISSIPATION
OF CONVECTION WHILE OTHER GUIDANCE SUGGESTS THAT CONVECTION COULD
PERSIST WELL INTO THE OVERNIGHT. PREVIOUS FORECASTS INCLUDED SLIGHT
CHANCE POPS. WITHOUT A STRONG REASON TO LOWER POPS MAINTAINED
WITHOUT MUCH CHANGE...BUT FORECAST CONFIDENCE REMAINS LOW.

THURSDAY...THE STATIONARY FRONT WILL GRADUALLY DISSIPATE NORTH OF
THE REGION. 01/12Z GUIDANCE SUGGESTS THAT RIDGING WILL STRENGTHEN AT
THE SURFACE AND ALOFT...PERHAPS ACCOMPANIED BY SOME DEGREE OF
SUBSIDENCE/SUBTLE DRYING AS SUGGESTED BY MODEL SOUNDINGS.
THUS...MAINTAINED SLIGHT CHANCE/LOW CHANCE POPS...BUT THURSDAY COULD
BE SOMEWHAT LESS ACTIVE AS COMPARED WITH TUESDAY/WEDNESDAY. DEEP
LAYERED ONSHORE FLOW COULD TRANSLATE TO TEMPERATURES A COUPLE OF
DEGREES COOLER THAN TUESDAY/WEDNESDAY...FEATURING HIGHS IN THE UPPER
80S/LOWER 90S EAST OF I-95 AND MID 90S WELL INLAND.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
THE EVER EVOLVING UPPER RIDGE ALOFT WILL PERSIST ACROSS THE
SOUTHEAST CONUS AS IT WOBBLES AROUND SOUTH OF THE MAIN BELT OF
WESTERLIES. THERE ARE INDICATIONS THAT BY THE LATTER PART OF THE
WEEKEND THE RIDGE WILL WEAKEN AND BECOME A BIT SEPARATED BY A
SHORTWAVE TO THE NORTH AND A TUTT-LIKE FEATURE NEAR THE NORTHERN
BAHAMAS. IN FACT...THE MEDIUM RANGE GUIDANCE SEEMS TO BE INDICATING
AN IMPROVING CHANCE FOR A MORE SIGNIFICANT FRONT TO APPROACH THE
AREA FROM THE NORTHWEST AND THEN STALL LATE IN THE WEEKEND INTO
EARLY NEXT WEEK. IF THIS COMES TO FRUITION IT WOULD NECESSITATE
HIGHER RAIN CHANCES LATE IN THE PERIOD. TEMPERATURES SHOULD HOLD
NEARLY STEADY ABOVE NORMAL WITH HIGHS IN THE LOW 90S AND LOWS IN THE
LOW 70S.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
VERY SMALL PROBABILITIES OF SUB-VFR CONDITIONS AROUND DAYBREAK
TUESDAY IN LOW STRATUS AND/OR LIGHT FOG...BUT PROBABILITIES ARE
TOO MINIMAL TO INCLUDE IN THE 06Z SET OF TAFS. FOR TUESDAY
AFTERNOON WE LOOK FOR ISOLATED TO SCATTERED SHRA/TSRA AROUND THE
AREA. BUT CONFIDENCE AND EXACT TIMING ARE NOT YET SUFFICIENT
ENOUGH TO INCLUDE ANY DIRECT IMPACTS AT THIS TIME. OTHERWISE...VFR
CONDITIONS WILL PREVAIL AT KSAV AND KCHS THROUGH 06Z WEDNESDAY.

EXTENDED AVIATION OUTLOOK...LOW CHANCES OF DIRECT IMPACTS FROM
ISOLATED SHOWERS/THUNDERSTORMS ESPECIALLY EACH AFTERNOON/EVENING
THROUGH FRIDAY. OTHERWISE...MAINLY VFR.

&&

.MARINE...
TONIGHT...LITTLE CHANGE EXPECTED IN THE OVERALL SYNOPTIC
PATTERN...AS THE MARINE ZONES REMAIN ON THE WESTERN PERIPHERY OF
SURFACE HIGH PRESSURE ANCHORED ACROSS THE FORECAST AREA. LOW LEVEL
JETTING WILL ALLOW WIND SPEEDS TO INCREASE UP TO 15 KT FOR
SEVERAL HOURS AS DIRECTIONS BECOME MORE SOUTH TO THE SOUTHWEST
THROUGH THE NIGHT. ISOLATED SHOWERS AND THUNDERSTORMS WILL AGAIN
TAKE SHAPE...ESPECIALLY OUT NEAR THE WESTERN WALL OF THE GULF
STREAM.

TUESDAY THROUGH FRIDAY...OVERALL THE PATTERN WILL GENERALLY
REMAIN THE SAME THROUGH MIDWEEK AS ATLANTIC HIGH PRESSURE PRODUCES
GENERAL/PERSISTENT SOUTHERLY FLOW MAINLY LESS THAN 15 KT.
DEVIATIONS WILL OCCUR MAINLY AS THE DAILY SEA BREEZE TURNS WINDS
TOWARD THE SOUTH/SOUTHEAST...AS NOCTURNAL SURGES DEVELOP AND AS
THE LAND BREEZE PUSHES OFFSHORE EACH MORNING.

THURSDAY THROUGH FRIDAY...A SHIFTING OF THE PRIMARY SURFACE HIGH
POSITION WILL RESULT IN PREVAILING EAST/SOUTHEAST FLOW MAINLY 15 KT
OR LESS...PERHAPS ENHANCED BY THE DAILY SEA BREEZE CIRCULATION.

SEAS THIS WEEK WILL REMAIN 1-3 FT...HIGHEST BEYOND 20 NM.

THE WEAK PRESSURE PATTERN/LIGHT WIND FIELD EACH MORNING COULD
SUPPORT WATERSPOUT DEVELOPMENT...ESPECIALLY TUESDAY AND WEDNESDAY.

&&

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

&&

$$

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






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