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Area Forecast Discussion

918
FXUS62 KCHS 021714
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
114 PM 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/...
THIS AFTERNOON AND EVENING...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 BASE 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...THE FIRST
BEING ASSOCIATED WITH A SEABREEZE ALONG THE SOUTHEAST SOUTH CAROLINA
AND SOUTHEAST GEORGIA COASTLINE EARLY THIS AFTERNOON. THUNDERSTORMS
SHOULD REMAIN PULSE TYPE IN NATURE FOR THE NEXT COUPLE HOURS...BUT
COULD PRODUCE ISOLATED STRONG AND/OR DAMAGING WIND GUSTS. THE SECOND
ROUND OF PRECIP WILL LIKELY BE ASSOCIATED WITH A H5 SHORTWAVE THAT
SHIFTS OVER THE AREA LATER THIS AFTERNOON INTO THE EVENING. EXPECT
PRECIP COVERAGE AND INTENSITY TO PEAK WHILE THIS SHORTWAVE SHIFTS
OVER THE AREA DURING MAXIMUM SFC HEATING. A FEW OF THE HIRES MODELS
SUGGEST ACTIVITY WILL BE IN THE FORM OF A LINE OF SHOWERS AND
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 SUPPORT SOME STRONGER AND/OR SEVERE
THUNDERSTORMS LATER THIS AFTERNOON INTO THE EVENING...ESPECIALLY
WHEN ACTIVITY ENCOUNTERS THE SEABREEZE. THE MAIN THREAT ASSOCIATED
WITH THESE STRONG OR SEVERE THUNDERSTORMS WILL BE DAMAGING WIND
GUSTS.

TONIGHT...CONVECTION WILL LINGER LATE THIS EVENING...BUT SHOULD
GRADUALLY TAPER OFF FROM WEST TO EAST WITH THE LOSS OF DAYTIME
HEATING EARLY TONIGHT. 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 /17Z 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...
THIS AFTERNOON...ATLANTIC HIGH PRESSURE WILL DOMINATE THE WEATHER
PATTERN OVER THE COASTAL WATERS WITH A PIEDMONT TROUGH SITUATED
INLAND. IN GENERAL...SOUTH/SOUTHWEST WINDS WILL REMAIN AT OR BELOW
15-20 KTS...HIGHEST NEAR A SEABREEZE CIRCULATION AND DURING
NOCTURNAL LOW LEVEL JETTING. SEAS WILL RANGE BETWEEN 2-4 FT. WINDS
AND SEAS WILL VARY WITHIN THUNDERSTORMS...WHICH ARE CURRENTLY
ONGOING NEAR A SEABREEZE ALONG THE COAST EARLY THIS AFTERNOON. A
FEW OF THESE THUNDERSTORMS COULD BE SEVERE WITH STRONG WIND GUSTS
BEING THE PRIMARY CONCERN.

FRIDAY 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 THIS AFTERNOON THAN PREVIOUS DAYS. THIS COMBINED WITH
MODEST SWELL AND ASTRONOMICAL INFLUENCES WILL CONTRIBUTE TO A
MODERATE RISK OF RIP CURRENTS THROUGH THIS AFTERNOON.


&&

.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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