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Area Forecast Discussion

011
FXUS62 KCHS 301454
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1054 AM EDT SAT AUG 30 2014

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL EXPAND WESTWARD THROUGH THE WEEKEND AND
PREVAIL THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. A COLD FRONT COULD
APPROACH THE REGION LATE NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
LATEST AREA OBSERVATIONS INDICATE DEWPOINT TEMPERATURES CURRENTLY
RUNNING SEVERAL DEGREES HIGHER THAN THE PREVIOUS 24 HOURS. THE
12Z CHARLESTON SOUNDING SHOWS PRECIPITABLE WATER VALUES HAVING
RECOVERED TO ABOUT 1.2 INCHES AND MORE NOTABLE MOISTURE BELOW 800
MB. AS A RESULT...SCATTERED SKY COVER IS EVIDENT IN LATE MORNING
SATELLITE IMAGERY...WITH CUMULUS CLOUDS SPREADING FROM EAST TO
WEST WITHIN A LIGHT ONSHORE FLOW. A FEW SHOWERS HAVE EVEN
INITIATED AS EARLY AS 10 AM EDT IN SOUTH CAROLINA ZONES WEST OF
INTERSTATE 95...LIKELY ALONG A SUBTLE LINE OF CONVERGENCE. HIGH
RESOLUTION MODEL SOLUTIONS SUGGEST THAT ISOLATED SHOWERS/BRIEF
THUNDERSTORMS COULD CONTINUE TO DEVELOP ALONG THE COAST...AND THEN
SPREAD ALONG AND INLAND OF THE SEABREEZE BY EARLY AFTERNOON.
HOWEVER...THE BEST INSTABILITY AND DEEPER MOISTURE WILL LIKELY BE
CONFINED JUST OUTSIDE OF THE FORECAST AREA...AWAY FROM THE
STRONGEST INFLUENCE OF DEEP LAYER RIDGING. HIGH TEMPERATURES WILL
ONCE AGAIN RISE ABOVE SEASONAL NORMALS...REACHING THE LOW TO MID
90S AWAY FROM THE LOCALLY COOLER COASTLINE.

TONIGHT...ISOLATED SHOWER/THUNDERSTORM ACTIVITY WILL DISSIPATE
WITH SUNSET. THUS EXPECT MAINLY DRY WEATHER OVERNIGHT...WITH
PERHAPS AN ISOLATED SHOWER AT THE BEACHES AND BARRIER ISLANDS
AFTER MIDNIGHT. THERE WILL BE ANOTHER CHANCE FOR PATCHY FOG ACROSS
INLAND AREAS TOWARD DAYBREAK SUNDAY.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
SUNDAY AND SUNDAY NIGHT...THE CENTER OF THE UPPER RIDGE ALOFT AND
ASSOCIATED ANTICYCLONE WILL MOVE VERY LITTLE AND REMAIN NEARLY RIGHT
ON TOP OF THE FORECAST AREA. SIMILARLY...THE SURFACE PATTERN WILL
FEATURE ATLANTIC HIGH PRESSURE NOSING IN FROM THE EAST AND
CONTROLLING THE LOW LEVELS. MUCH OF THE FORECAST AREA WILL CONTINUE
TO SEE VERY DRY MID/UPPER LEVELS...THOUGH BETTER MOISTURE WILL EXIST
ACROSS SOUTHEAST GEORGIA IN THE AFTERNOON/EVENING HOURS. SOUNDINGS
SHOW A NOTABLE CAP IN THE 700-800 MB LAYER ACROSS THE SOUTH CAROLINA
ZONES. I HAVE NOT MADE ANY CHANGES TO THE POP FORECAST...WHICH STILL
FEATURES CHANCES POPS ACROSS SOUTHEAST GEORGIA AND ALONG THE
SAVANNAH RIVER...WITH ONLY SLIGHT CHANCES ELSEWHERE DURING PEAK
HEATING. OVERNIGHT...ANY LINGERING ACTIVITY WILL DIMINISH IN THE
EVENING WITH JUST SLIGHT CHANCES OVER THE COASTAL WATERS LATE. LOOK
FOR HIGHS IN THE LOW/MID 90S AND LOWS IN THE MID/UPPER 70S.

MONDAY THROUGH TUESDAY...THE PATTERN WILL REMAIN QUITE TYPICAL OF
SUMMERTIME WITH RIDGING ALOFT AND ATLANTIC HIGH PRESSURE AT THE
SURFACE. THROUGH THE EARLY WEEK PERIOD...THE UPPER RIDGE WILL BECOME
INCREASINGLY WEST/EAST ORIENTED AS IT RETROGRADES A BIT BACK TO THE
WEST. THE BELT OF WESTERLIES WILL REMAIN NORTH OF THE AREA...AS WELL
AS ANY EMBEDDED SHORTWAVES. THE ATMOSPHERE WILL GRADUALLY BE LESS
HOSTILE TO CONVECTIVE DEVELOPMENT AS MOISTURE IMPROVES ACROSS THE
REGION. HOWEVER...DUE TO THE LACK OF LARGER SCALE
FORCING...PRECIPITATION CHANCES WILL LARGELY BE DRIVEN BY
CONVERGENCE ALONG THE AFTERNOON SEA BREEZE AND SURFACE HEATING
PROCESSES. THIS WILL KEEP THE COVERAGE IN THE ISOLATED TO SCATTERED
RANGE EACH AFTERNOON AND EVENING. THE OVERALL SEVERE THREAT IS QUITE
LOW DURING THIS TIME...BUT AN ISOLATED SEVERE STORM CANNOT BE RULED
OUT DUE TO MESOSCALE BOUNDARY INTERACTIONS. TEMPERATURES WILL
CONTINUE TO BE ABOVE NORMAL WITH HIGHS IN THE LOW/MID 90S AND LOWS
IN THE MID/UPPER 70S.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
LITTLE CHANGE WAS MADE TO THE GOING FORECAST IN THE LONG TERM
PERIOD. THE SOUTHEAST REGION WILL REMAIN UNDER THE INFLUENCE OF THE
RIDGE ALOFT...WHICH WILL ACTUALLY EXPAND BACK EASTWARD AND
STRENGTHEN IN THE MID/LATE TIME FRAME. ATLANTIC HIGH PRESSURE WILL
STILL BE THE PRIMARY SURFACE FEATURE AS IT EXTENDS WESTWARD ACROSS
THE FORECAST AREA. THERE ARE SOME INDICATIONS THAT A FRONT WILL
ATTEMPT TO APPROACH FROM THE NORTH LATE IN THE PERIOD...BUT GIVEN
THE OVERALL PATTERN THE EXPECTATION IS FOR IT TO REMAIN NORTH OF THE
AREA. ABOVE NORMAL TEMPERATURES ARE FORECAST THROUGH THE PERIOD.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
INCREASING LOW LEVEL MOISTURE...COMBINED WITH SEABREEZE AND
BOUNDARY INTERACTIONS...COULD SUPPORT ISOLATED SHRA/TSRA AT BOTH
TERMINALS THIS AFTERNOON. HOWEVER...PREFER TO MONITOR RADAR TRENDS
TO DETERMINE TIMING AND COVERAGE POTENTIAL BEFORE ADDING EXPLICIT
MENTION OF ANY IMPACTS TO EITHER TAF. MODEL GUIDANCE IS AGAIN
HINTING AT THE POTENTIAL FOR PATCHY FOG DEVELOPMENT AFTER
MIDNIGHT...AND WILL CONSIDER TRENDING TOWARD THIS SCENARIO WITH
LATER TAF ISSUANCES.

EXTENDED AVIATION OUTLOOK...LOW CHANCES OF DIRECT IMPACTS FROM
ISOLATED SHOWERS/THUNDERSTORMS THROUGH EARLY NEXT WEEK. ALSO...LOW
CHANCES FOR EARLY MORNING FOG/STRATUS THROUGH EARLY NEXT WEEK.
OTHERWISE...MAINLY VFR.

&&

.MARINE...
A RELATIVELY LIGHT PRESSURE GRADIENT WILL LINGER OVER THE WATERS
THROUGH TONIGHT. A LIGHT AND MOSTLY ONSHORE SOUTHEAST FLOW WILL
PREVAIL AT LESS THAN 15 KT...WITH SEAS RANGING FROM 2 TO 3 FT. THE
INCREASE IN LOW LEVEL MOISTURE...WHEN COMBINED WITH PERSISTENT
LIGHT WINDS...WILL SUPPORT A SMALL POTENTIAL FOR WATERSPOUTS
WITHIN ANY LINES OF CONVERGENCE AND/OR SHOWER ACTIVITY. MARINE
WEATHER STATEMENTS WILL ADDRESS ANY SHORT-FUSED CONCERNS.

SUNDAY THROUGH WEDNESDAY...ATLANTIC HIGH PRESSURE CENTERED TO THE
EAST OF THE LOCAL WATERS WILL BE THE PRIMARY FEATURE THROUGH THE
MIDDLE OF NEXT WEEK. THIS WILL DRIVE A PERSISTENT SOUTH TO SOUTHWEST
FLOW THROUGH MOST OF THE PERIOD. FOR MUCH OF THE PERIOD...WINDS WILL
BE LESS THAN 15 KT. THEY COULD INCREASE INTO THE 15-20 KT RANGE AT
TIMES...ESPECIALLY WITH THE AFTERNOON SEA BREEZE ALONG THE LAND/SEA
INTERFACE AND IN NOCTURNAL SURGES. SEAS WILL GENERALLY BE 2 FT
ACROSS THE NEARSHORE WATERS AND 2-3 FT FOR THE OUTER WATERS. OVERALL
CONDITIONS ARE EXPECTED TO STAY BELOW SMALL CRAFT ADVISORY
THRESHOLDS THROUGH THE PERIOD.

&&

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

&&

$$

NEAR TERM...WMS
SHORT TERM...BSH
LONG TERM...BSH
AVIATION...WMS/
MARINE...WMS/BSH






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