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Area Forecast Discussion

803
FXUS62 KCHS 020829
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
429 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/...
A FAIRLY PROGRESSIVE UPPER PATTERN WILL EXIST TODAY AS A BROAD
UPPER TROUGH RESIDES ACROSS THE EASTERN UNITED STATES. A SERIES OF
UPPER SHORTWAVES ARE EXPECTED TO AFFECT THE FORECAST AREA...THE
FIRST MOVING INTO SOUTHERN SC EARLY THIS AFTERNOON...FOLLOWED BY A
MORE POTENT VORT MOVING INTO SOUTHEAST GA LATE THIS AFTERNOON.
CONSIDERABLE MID AND HIGH LEVEL CLOUDINESS LOCATED UPSTREAM EARLY
THIS MORNING WILL SLIDE EAST THIS MORNING. THIS...ALONG WITH
RESIDUAL SMOKE FROM WESTERN CANADA WILDFIRES...WILL PUT A SLIGHT
DAMPER ON OUR DIABATIC HEATING AND KEEP HIGH TEMPS IN THE 90-92F
RANGE AWAY FROM THE COAST. HOWEVER...A JUICY AIRMASS WILL
NONETHELESS BE IN PLACE AS THE FLOW BACKS BELOW 500 MB. PWATS ARE
PROGGED AT RIGHT AROUND 2 INCHES THIS AFTERNOON AND EVENING WHICH
WILL BE SUFFICIENT FOR SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS TO DEVELOP. SURFACE BASED CAPES WILL BE BETWEEN 1500
AND 2000 J/KG ACROSS THE BOARD WITH HIGHER VALUES IN POCKETS WHERE
MORE SUNSHINE OCCURS.

WE COULD SEE THE FIRST CONVECTION ACROSS INLAND SC EARLIER THIS
AFTERNOON AS THE INITIAL SHORTWAVE DROPS INTO THE AREA. WE ARE
THINKING THERE IS SLIGHTLY HIGHER POTENTIAL FOR SEVERE
THUNDERSTORMS ACROSS SOUTHEAST GA LATER IN THE AFTERNOON AS A MORE
POTENT SHORTWAVE MOVES INTO AN AREA WITH GREATER INSTABILITY AND
850 MB WINDS INCREASE TO 30 KT. IT IS POSSIBLE AN MCS MAY DEVELOP
UPSTREAM AND MOVE INTO SOUTHEAST GA LATE IN THE DAY AS INDICATED
BY THE 00Z NSSL WRF MODEL. WE INCREASED POPS TO 50 PERCENT LATE
IN THE DAY IN COASTAL AREAS...ESPECIALLY SOUTHEAST GA.

CONVECTION WILL LIKELY LINGER INTO THE EVENING...GRADUALLY
TAPERING OFF FROM WEST TO EAST. LOWS WILL BE IN THE LOW TO MIDDLE
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 /08Z THURSDAY THROUGH MONDAY/...
INCREASING CHANCES FOR CONVECTION AT BOTH TERMINALS THIS AFTERNOON
AND POTENTIALLY LINGERING INTO EARLY EVENING. CEILING AND
VISIBILITY RESTRICTIONS ARE EXPECTED AT LEAST TEMPORARILY AT BOTH
SITES. ALTHOUGH THERE IS FAIRLY STRONG UPPER FORCING TO SUPPORT
SCATTERED SHOWERS AND TSTMS THROUGH THE AFTERNOON...THERE ARE
HINTS THAT KCHS WILL EXPERIENCE A STORM EARLIER IN THE AFTERNOON
VS LATE AFTERNOON FOR KSAV. AT THIS POINT WE SIMPLY MAINTAINED
THE VICINITY THUNDERSTORMS AT BOTH SITES. NO SIGNIFICANT
RESTRICTIONS IN VSBY OR CEILING ANTICIPATED OUTSIDE CONVECTION.

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...JRL
SHORT TERM...JAQ
LONG TERM...JAQ
AVIATION...JAQ/JRL
MARINE...JAQ/JRL



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