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Area Forecast Discussion

798
FXUS62 KCHS 021456
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1056 AM EDT THU JUL 2 2015

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL PREVAIL AS A TROUGH OF LOW PRESSURE
LINGERS INLAND THROUGH THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
TODAY...A BROAD MID LVL TROUGH OF LOW PRESSURE WILL EXPAND OVER MUCH
OF THE EASTERN CONUS WITH A SERIES OF H5 SHORTWAVES THAT ROUND ITS
SOUTHERN PERIPHERY OVER THE SOUTHEASTERN UNITED STATES. AT THE
SFC...THE AREA WILL REMAIN BETWEEN A PIEDMONT TROUGH INLAND AND HIGH
PRESSURE OVER THE WESTERN ATLANTIC. THE SETUP WILL FAVOR A
WEST/SOUTHWEST FLOW THAT BUILDS DEEP MOISTURE TO THE AREA WITH PWATS
CHARACTERIZED AROUND 2.0 INCHES THIS AFTERNOON. THESE MOISTURE
LEVELS ALONG WITH FORCING ALONG THE BASE OF THE LOW PRESSURE TROUGH
CENTERED TO OUR NORTH WILL FAVOR A PERIOD OF SHOWERS AND
THUNDERSTORMS OVER MUCH OF THE AREA THIS AFTERNOON AND EVENING.

THE BULK OF PRECIP ACTIVITY SHOULD COME IN TWO ROUNDS TODAY...MAINLY
WITH THE ARRIVAL OF TWO DISTINCT H5 SHORTWAVES. THE FIRST OF THESE
SHORTWAVES CONTINUES TO SUPPORT A FEW SHOWERS OVER INLAND AREAS OF
SOUTHEAST SOUTH CAROLINA...BUT FURTHER STRENGTHENING AND COVERAGE OF
THIS ACTIVITY WILL BE LIMITED WHILE THE AREA REMAINS CAPPED. THE
SECOND AND SLIGHTLY MORE POTENT SHORTWAVE IS EXPECTED TO SHIFT OVER
THE AREA LATER THIS AFTERNOON INTO THE EVENING. EXPECT PRECIP
COVERAGE AND INTENSITY TO PEAK AS THIS SHORTWAVE SHIFTS OVER THE
AREA DURING MAXIMUM SFC HEATING...POSSIBLY IN THE FORM OF A LINE OF
SHOWERS/THUNDERSTORMS THAT PUSH EASTWARD INTO THE AREA DURING MID
AFTERNOON THROUGH EVENING HOURS. SBCAPES RANGING BETWEEN
1500-2000 J/KG ALONG WITH 20-30 KT LOW LVL WINDS WILL ALSO SUPPORT
SOME STRONGER AND/OR SEVERE THUNDERSTORMS LATER THIS AFTERNOON
INTO THE EVENING...ESPECIALLY WHEN ACTIVITY ENCOUNTERS AN INLAND
MOVING SEABREEZE. THE MAIN THREAT ASSOCIATED WITH STRONG OR SEVERE
THUNDERSTORMS WILL BE DAMAGING WIND GUSTS.

OVERALL HIGH TEMPS WILL GENERALLY PEAK IN THE LOWER 90S THIS
AFTERNOON...WARMEST OVER SOUTHEAST GEORGIA AWAY FROM THE COAST.
CONVECTION WILL THEN LINGER LATE THIS EVENING...GRADUALLY
TAPERING OFF FROM WEST TO EAST OVERNIGHT. LOW TEMPS WILL RANGE IN
THE LOW TO MID 70S.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
FRIDAY AND FRIDAY NIGHT...A BROAD UPPER LEVEL TROUGH WILL PERSIST
ALOFT...WHILE AT THE SURFACE ATLANTIC HIGH PRESSURE WILL PREVAIL AS
A PIEDMONT TROUGH LINGERS JUST INLAND. THE RESULTING DEEP SOUTHWEST
FLOW WILL ALLOW ABUNDANT MOISTURE TO ADVECT INTO THE REGION...WITH
PRECIPITABLE WATER VALUES RISING TO JUST ABOVE 2 INCHES. THE
MOISTURE COMBINED WITH SHORT WAVE ENERGY ALOFT ROUNDING THE BASE OF
THE UPPER TROUGH WILL BE MORE THAN SUFFICIENT TO GENERATE SHOWERS
AND THUNDERSTORMS ACROSS THE AREA. THE COVERAGE SHOULD BE BEST
ACROSS THE CHARLESTON TRI-COUNTY AREA DUE TO ITS CLOSER PROXIMITY TO
THE PIEDMONT TROUGH AND GREATER ENERGY ALOFT...WITH THE FORECAST
REFLECTING SHOWERS AND THUNDERSTORMS LIKELY HERE...WITH A DIMINISHING
CHANCE FARTHER SOUTH INTO SOUTHEAST GEORGIA. THE CHANCE FOR SHOWERS
AND THUNDERSTORMS WILL PERSIST WELL INTO THE EVENING...BEFORE
DIMINISHING OVERNIGHT. THERE IS THE POTENTIAL FOR SOME OF THE
THUNDERSTORMS TO BECOME STRONG OR SEVERE...ESPECIALLY IF ANY
ORGANIZATION CAN OCCUR...WITH THE PRIMARY THREAT BEING DAMAGING
WINDS. HIGHS SHOULD BE IN THE LOWER 90S WITH LOWS IN THE LOWER TO
MID 70S INLAND FROM THE IMMEDIATE COAST.

SATURDAY AND SUNDAY...THE SYNOPTIC PATTERN CHANGES LITTLE...BUT
THERE APPEARS TO BE A BIT LESS IN THE WAY OF SHORT WAVE ENERGY ALOFT
AND MORE OF A WESTERLY COMPONENT TO THE LOW AND MID LEVEL FLOW.
WHILE THIS SHOULD RESULT IN LESS COVERAGE OF SHOWERS AND
THUNDERSTORMS...WILL STILL MAINTAIN A LOW CHANCE IN THE FORECAST
GIVEN THE PROXIMITY OF THE PIEDMONT TROUGH AND TO ACCOUNT FOR SOME
LOW LEVEL CONVERGENCE ALONG THE SEA BREEZE. HIGHS SHOULD BE IN THE
LOWER TO MID 90S ON SATURDAY AND AROUND 90 OR IN THE LOWER 90S ON
SUNDAY. LOWS SHOULD REMAIN IN THE LOWER TO MID 70S.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
MEDIUM RANGE GUIDANCE IS IN FAIRLY GOOD AGREEMENT THROUGH THE LONG
TERM PERIOD. AN UPPER LEVEL TROUGH WILL DEEPEN OVER THE SOUTHEAST
STATES AND PERSIST THROUGH MID-WEEK. MEANWHILE AT THE SURFACE...
ATLANTIC HIGH PRESSURE WILL PREVAIL AS A PIEDMONT TROUGH PERSISTS
INLAND. THIS PATTERN WILL FAVOR CHANCES OF MAINLY DIURNALLY DRIVEN
SHOWERS AND THUNDERSTORMS EACH DAY...WITH THE GREATEST COVERAGE
LIKELY TO OCCUR MONDAY AND TUESDAY. TEMPERATURES WILL GENERALLY BE
NEAR NORMAL...WITH HIGHS AROUND 90 OR IN THE LOWER 90S AND LOWS IN
THE LOWER TO MID 70S.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
HIGH RESOLUTION MODELS SUGGEST THE POSSIBILITY OF SOME CONVECTION
DEVELOPING EARLY IN THE AFTERNOON IN THE VICINITY OF KCHS...WITH A
GREATER POTENTIAL AT BOTH TERMINALS LATE THIS AFTERNOON AND EARLY
THIS EVENING AS A MORE ORGANIZED AREA OF CONVECTION MOVES THROUGH
THE AREA. THE FORECAST WILL REFLECT VICINITY THUNDERSTORMS
BEGINNING AT 17Z...WITH A TEMPO GROUP FOR THUNDERSTORMS FROM
21-01Z. CEILING AND VISIBILITY RESTRICTIONS ARE EXPECTED IN
CONVECTION AT LEAST TEMPORARILY...BUT VFR CONDITIONS SHOULD
PREVAIL OUTSIDE OF CONVECTION. IN ADDITION...GUSTY WINDS UPWARDS
OF 20 KT ARE EXPECTED THROUGH MUCH OF THE AFTERNOON.

EXTENDED AVIATION OUTLOOK...BRIEF FLIGHT RESTRICTIONS ARE POSSIBLE
IN MAINLY AFTERNOON/EARLY EVENING ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS. OTHERWISE...VFR CONDITIONS ARE GENERALLY EXPECTED TO
PREVAIL.

&&

.MARINE...
THROUGH TUESDAY...ATLANTIC HIGH PRESSURE WILL GENERALLY DOMINATE
THE WEATHER PATTERN OVER THE COASTAL WATERS WITH A PIEDMONT TROUGH
SITUATED INLAND. A TIGHTENED PRESSURE GRADIENT BETWEEN THE TWO
FEATURES WILL KEEP WINDS FAIRLY ELEVATED THROUGH THE PERIOD. IN
FACT...IT APPEARS THAT CONDITIONS COULD REACH MARGINAL SMALL CRAFT
ADVISORY CRITERIA OVER A PORTION OF THE WATERS FRIDAY AFTERNOON
INTO FRIDAY NIGHT. OTHERWISE...SEA BREEZE CIRCULATIONS AND
NOCTURNAL LOW LEVEL JETTING WILL ALLOW SOUTH/SOUTHWEST WINDS TO
PEAK NEAR 15-20 KTS...WITH 25 KTS LOCALLY AT TIMES IN FAVORED
LOCATIONS. SEAS WILL BE 2-4 FEET ON AVERAGE...BUT COULD REACH 5 FT
IN THE OUTER PORTIONS OF THE WATERS DURING NOCTURNAL SURGES.

RIP CURRENTS...WINDS WILL BE A BIT STRONGER ALONG THE CHARLESTON
COUNTY COAST TODAY. THIS COMBINED WITH MODEST SWELL AND
ASTRONOMICAL INFLUENCES WILL CONTRIBUTE TO A MODERATE RISK OF RIP
CURRENTS TODAY.

&&

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

&&

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



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