National Weather Service Weather Forecast Office

Area Forecast Discussion

750
FXUS62 KCHS 240825
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
425 AM EDT FRI MAY 24 2013

.SYNOPSIS...
A WEAK COLD FRONT WILL MOVE OFFSHORE THIS MORNING...FOLLOWED BY A
REINFORCING COLD FRONT LATE THIS AFTERNOON AND EARLY THIS EVENING.
HIGH PRESSURE WILL THEN BUILD INTO THE REGION THROUGH NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS A BROAD UPPER LEVEL
TROUGH CENTERED OVER THE GREAT LAKES REGION. MEANWHILE AT THE
SURFACE...A COLD FRONT EXTENDS ACROSS THE UPSTATE OF SOUTH
CAROLINA AND NORTH-CENTRAL GEORGIA...WITH A WEAK PRE-FRONTAL
TROUGH SHIFTING TOWARD THE COAST.

AS THE DAY PROGRESSES...THE UPPER LEVEL TROUGH WILL DIG ACROSS
THE MID-ATLANTIC REGION. THIS WILL PUSH THE PRIMARY COLD FRONT
ACROSS THE AREA LATER THIS MORNING...WITH A REINFORCING COLD FRONT
THEN EXPECTED TO SHIFT INTO THE AREA LATE THIS AFTERNOON AS THE
TROUGH AXIS CROSSES.

THE PRE-FRONTAL TROUGH WAS RESPONSIBLE FOR SOME ISOLATED SHOWERS
ACROSS SOUTHEAST GEORGIA OVERNIGHT...BUT THIS ACTIVITY SHOULD END
AS THE TROUGH MOVES OFFSHORE PRIOR TO DAYBREAK. THE DRY WESTERLY
FLOW BEHIND THE PRE-FRONTAL TROUGH WILL PREVENT ANY ADDITIONAL
SHOWERS FROM FORMING AS THE PRIMARY COLD FRONT MOVES
THROUGH...WITH THE FLOW THEN VEERING NORTHWEST INTO THIS
AFTERNOON. THERE COULD BE SOME SCATTERED MID LEVEL CLOUDS BENEATH
THE UPPER TROUGH...ESPECIALLY OVER SOUTHEAST SOUTH CAROLINA...BUT
A GOOD AMOUNT OF SUNSHINE AND A STRONG DOWNSLOPE FLOW WILL SUPPORT
HIGHS IN THE MID TO UPPER 80S ACROSS THE AREA AWAY FROM THE
IMMEDIATE COAST. DEEP MIXING THIS AFTERNOON WILL SUPPORT BREEZY
CONDITIONS...WITH WINDS AS HIGH AS 15-20 MPH WITH GUSTS TO 25 MPH
AT TIMES.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
TONIGHT...THE UPPER LEVEL TROUGH WILL BEGIN TO SHIFT OFF THE MID-
ATLANTIC COAST THIS EVENING THEN PROGRESS OFFSHORE OVERNIGHT. A
REINFORCING COLD FRONT WILL COMPLETE ITS PASSAGE ACROSS THE AREA
DURING THE EARLY EVENING...WITH A NORTHERLY FLOW DEVELOPING IN ITS
WAKE AS HIGH PRESSURE BUILDS FROM THE GREAT LAKES REGION. THE
REINFORCING COLD FRONT WILL USHER IN A SIGNIFICANTLY DRIER AND
COOLER AIRMASS. THE COLD AIR ADVECTION WILL CAUSE TEMPERATURES TO
PLUMMET INTO THE UPPER 40S TO LOWER 50S AWAY FROM THE IMMEDIATE
COAST...WITH SOME MID 40S POSSIBLE WELL INLAND IF WINDS FULLY
DECOUPLE.

SATURDAY THROUGH MONDAY...MEDIUM RANGE GUIDANCE IS IN PRETTY GOOD
AGREEMENT THIS PERIOD SHOWING THE UPPER TROUGH SHIFTING OFFSHORE
WITH THE SURFACE HIGH TO FOLLOW. THIS WILL KEEP A DRY AND COOLER
THAN NORMAL AIR MASS IN PLACE. DEEP MOISTURE AND FORCING FOR
ASCENT WILL BE LACKING SO RAINFALL IS NOT EXPECTED THROUGH THE
PERIOD. THE BEST CHANCE OF ISOLATED SHOWERS WILL LIKELY COME
MONDAY AFTERNOON...MAINLY NORTH OF CHARLESTON...AS THE SEA BREEZE
PUSHES INLAND IN AN AXIS OF SLIGHTLY DEEPER MOISTURE.

WITH THE VERY DRY AIRMASS IN PLACE...TEMPERATURES WILL VARY ABOUT
25-30 DEGREES FROM THE MORNING LOWS TO THE AFTERNOON HIGHS. MORNING
LOWS SUNDAY COULD GET WITHIN A FEW DEGREES OF THE RECORDS AT
CHARLESTON AND SAVANNAH.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
DECENT MODEL AGREEMENT THIS PERIOD WITH ABOVE AVERAGE FORECAST
CONFIDENCE. UPPER HIGH PRESSURE SHOULD BUILD ACROSS THE REGION
TOWARD THE MIDDLE OF NEXT WEEK LEADING TO WARMING TEMPERATURES AND
SLOWLY INCREASING LOW-LEVEL MOISTURE. RAIN CHANCES WILL REMAIN LOW
GIVEN THE LACK OF DEEP MOISTURE AND FORCING...MAINLY CONFINED TO
INLAND AREAS DURING AFTERNOON PEAK HEATING AS THE SEA BREEZE PUSHES
INLAND.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
VFR CONDITIONS WILL PREVAIL AT KCHS AND KSAV THROUGH 06Z SATURDAY.

EXTENDED AVIATION...VFR CONDITIONS SHOULD PREVAIL.

&&

.MARINE...
TODAY...A WEAK COLD FRONT WILL MOVE OFFSHORE THIS MORNING WITH
NORTHWEST WINDS PREVAILING ACROSS THE WATERS. WIND SPEEDS WILL
GENERALLY BE IN THE 10-15 KT RANGE TODAY...ALTHOUGH SOME HIGHER WINDS
COULD OCCUR OVER THE OUTER GEORGIA WATERS THIS MORNING. SEAS WILL
BE NO HIGHER THAN 2-4 FT WITH THE LIMITED OFFSHORE FETCH.

TONIGHT...A REINFORCING COLD FRONT WILL MOVE THROUGH EARLY THIS
EVENING...WITH A STRONG NORTHERLY SURGE DEVELOPING IN ITS WAKE.
A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR THE OUTER GEORGIA
WATERS DUE TO THE ELEVATED WINDS/SEAS ASSOCIATED WITH THE
NORTHERLY SURGE. CONDITIONS WILL BE NEAR SMALL CRAFT ADVISORY
LEVELS WITHIN 20 NM OF THE COAST...ESPECIALLY IN GEORGIA...HOWEVER
CONFIDENCE IS TOO LOW GIVEN THE MARGINAL CONDITIONS TO ISSUE ANY
ADDITIONAL SMALL CRAFT ADVISORIES AT THIS TIME.

SATURDAY THROUGH WEDNESDAY...HIGH PRESSURE WILL MOVE OFFSHORE EARLY
NEXT WEEK AND PERSIST THROUGH MID WEEK. ENHANCED WINDS/SEAS EARLY
SATURDAY WILL DIMINISH DURING THE DAY AS THE HIGH GAINS MORE
INFLUENCE AND THE PRESSURE GRADIENT SLACKENS. A MORE TYPICAL
SPRINGTIME PATTERN WILL DOMINATE THERAFTER WITH SOME WIND
ENHANCEMENT DURING THE DAY NEAR THE COAST AS THE SEA BREEZE DEVELOPS
AND THEN OFFSHORE OVERNIGHT WITH NOCTURNAL SURGING.
HOWEVER...CONDITIONS ARE EXPECTED TO REMAIN BELOW ADVISORY LEVELS
THROUGH THE PERIOD.

RIP CURRENTS...THE COMBINATION OF ASTRONOMICAL INFLUENCES AND AN 8
SECOND LONG PERIOD SWELL WILL RESULT IN A MODERATE RISK OF RIP
CURRENTS AT AREA BEACHES TODAY. THE ENHANCED RIP CURRENT RISK MAY
PERSIST INTO SATURDAY.

&&

.TIDES/COASTAL FLOODING...
HIGH ASTRONOMICAL TIDES AND FAVORABLE NORTH/NORTHEAST WINDS COULD
LEAD TO MINOR SALTWATER INUNDATION NEAR THE COAST DURING THE HIGH
TIDE THIS EVENING AND AGAIN SATURDAY EVENING. BY THE TIME OF THE
HIGH TIDE SUNDAY EVENING AND MONDAY EVENING...WINDS WILL NOT BE AS
CONDUCIVE...YET MINOR SALTWATER FLOODING WILL STILL BE POSSIBLE AS
ASTRONOMICAL FACTORS WILL CAUSE HIGHER THAN TYPICAL TIDES.

&&

.CLIMATE...
RECORD LOW TEMPERATURES FOR MAY 25TH...
CHARLESTON INTERNATIONAL AIRPORT /KCHS/.....47 SET IN 1967
DOWNTOWN CHARLESTON /KCHL/..................54 SET IN 1979
SAVANNAH/HHI INTERNATIONAL AIRPORT /KSAV/...49 SET IN 1967

RECORD LOW TEMPERATURES FOR MAY 26TH...
CHARLESTON INTERNATIONAL AIRPORT /KCHS/.....50 SET IN 1979
DOWNTOWN CHARLESTON /KCHL/..................50 SET IN 1979
SAVANNAH/HHI INTERNATIONAL AIRPORT /KSAV/...49 SET IN 1979

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 8 AM EDT
     SATURDAY FOR AMZ374.

&&

$$

SYNOPSIS...
NEAR TERM...JAQ
SHORT TERM...JAQ/RJB
LONG TERM...RJB
AVIATION...JAQ/RJB
MARINE...JAQ/RJB
TIDES/COASTAL FLOODING...JAQ/RJB
CLIMATE...JAQ