National Weather Service Weather Forecast Office

Area Forecast Discussion

144
FXUS62 KCHS 231155
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
755 AM EDT THU MAY 23 2013

.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH LATE TONIGHT WITH DRY HIGH PRESSURE
BUILDING IN THROUGH THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
RAIN SHOWERS ASSOCIATED WITH A WELL DEFINED SHORTWAVE DISTURBANCE
MOVING ACROSS EASTERN GEORGIA AND THE UPSTATE OF SOUTH CAROLINA
HAVE GENERALLY DISSIPATED THIS MORNING DURING WHAT IS TYPICALLY A
CLIMATOLOGICAL MINIMUM FOR CONVECTION.

THE PRIMARY SHORTWAVE WILL PROGRESS THROUGH THE AREA FROM WEST TO
EAST TODAY. BY EARLY AFTERNOON IT LOOKS AS THOUGH VEERING WINDS ACROSS
SOUTHEAST GA WILL PRODUCE SOME DOWNSLOPE FLOW AND ALLOW FOR
PARTIAL CLEARING WITH TEMPS PUSHING INTO THE UPPER 80S. IN
SOUTHERN SC A DECENT SEABREEZE SHOULD TAKE SHAPE EARLY TO MID
AFTERNOON AND INTERACT WITH THE RESIDUAL SHORTWAVE ENERGY. WITH
DECENT SURFACE BASED CAPES AND COOLING MID-LEVELS THERE SHOULD BE
SCATTERED COVERAGE OF SHOWERS AND TSTMS MAINLY IN SOUTHERN SC THIS
AFTERNOON.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
THE COLD FRONT WILL MOVE THROUGH SHORTLY AFTER MIDNIGHT TONIGHT
WITH SLIGHTLY DRIER AIR BEGINNING TO FILTER IN. MOSTLY CLEAR SKIES
EXPECTED WITH TEMPERATURES IN THE LOWER 60S.

FRIDAY AND FRIDAY NIGHT...AN UPPER LEVEL TROUGH WILL MOVE ACROSS THE
MID-ATLANTIC REGION ON FRIDAY. IN WAKE OF THE DEPARTING COLD
FRONT...A DEEP LAYERED NORTHWEST FLOW WILL PREVAIL THROUGH MUCH OF
THE DAY. THE DOWNSLOPE FLOW WILL RESULT IN DRYING ACROSS THE AREA
AND WILL ALSO NEGATE MOST OF THE INITIAL SURGE OF COLD AIR ADVECTION
AS HIGHS SHOULD STILL BE IN THE MID TO UPPER 80S. UNDER MOSTLY SUNNY
SKIES...BREEZY CONDITIONS ARE ALSO EXPECTED. THEN...AS THE UPPER
TROUGH PASSES OFF THE MID-ATLANTIC COAST FRIDAY EVENING...IT WILL
PUSH A SECONDARY COLD FRONT ACROSS THE AREA ALLOWING HIGH PRESSURE
TO BUILD FROM THE GREAT LAKES REGION. THE AIRMASS WILL BEGIN TO
MODIFY SIGNIFICANTLY FOLLOWING THE SECONDARY COLD FRONT WITH
TEMPERATURES PLUMMETING INTO THE UPPER 40S AND LOWER 50S FRIDAY
NIGHT ON A NORTHERLY FLOW.

SATURDAY AND SATURDAY NIGHT...A VERY DRY AIRMASS WILL SETTLE OVER
THE REGION SATURDAY AS HIGH PRESSURE CONTINUES TO BUILD IN FROM THE
GREAT LAKES REGION. PRECIPITABLE WATER VALUES OF .25 TO .40 INCHES
WILL BE ABOUT AS LOW AS THEY CAN GET FOR THIS TIME OF YEAR...OR MORE
THAN 2 STANDARD DEVIATIONS BELOW NORMAL. FORECAST THICKNESS VALUES
ONLY SUPPORT HIGHS IN THE MID TO UPPER 70S...BUT GIVEN FULL SUNSHINE
AND THE HIGHER SUN ANGLE THIS TIME OF YEAR...WILL INDICATE HIGHS IN
THE UPPER 70S TO LOWER 80S ACROSS THE AREA. ANOTHER UNSEASONABLY
COOL NIGHT IS EXPECTED SATURDAY NIGHT...WITH LOWS IN THE LOWER TO
MID 50S.

SUNDAY...A WEAK PRESSURE PATTERN WILL PREVAIL OVER THE REGION. AN
INCREASE IN MID AND HIGH LEVEL MOISTURE WILL SUPPORT SOME CLOUD
COVER BUT THE AIRMASS IS TOO DRY STILL FOR ANY SHOWERS TO DEVELOP.
HIGHS SHOULD BE IN THE LOWER TO MID 80S ACROSS MUCH OF THE AREA.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
THE REGION WILL BE SANDWICHED BETWEEN TWO AREAS OF HIGH PRESSURE
EARLY IN THE WEEK...THE STRONGER OF THE TWO PASSING ACROSS THE
MID-ATLANTIC REGION AND THE OTHER OVER THE NORTHEAST GULF OF MEXICO.
DEEPENING MOISTURE WILL RESULT IN AT LEAST AN INCREASE IN CLOUD
COVER...BUT IT APPEARS THE RAIN-FREE CONDITIONS SHOULD PERSIST
THROUGH MEMORIAL DAY. ATLANTIC HIGH PRESSURE WILL THEN BECOME
ESTABLISHED THROUGH THE MIDDLE OF NEXT WEEK...SUPPORTING MAINLY
DIURNAL ISOLATED CONVECTION EACH AFTERNOON ALONG AND AHEAD OF THE
SEA BREEZE TUESDAY THROUGH THURSDAY. TEMPERATURES WILL MODERATE TO
NEAR NORMAL BY EARLY NEXT WEEK AND CONTINUE NEAR SEASONAL NORMS
THROUGH THE END OF THE FORECAST PERIOD.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS ARE EXPECTED TO PREVAIL AT BOTH KCHS AND KSAV
THROUGH 12Z FRIDAY. SCATTERED SHOWERS SHOULD DEVELOP IN ASSOCIATION
WITH A PRE-FRONTAL TROUGH ACROSS SOUTHEAST SC THIS AFTERNOON...WITH
COVERAGE MORE ISOLATED ELSEWHERE. AS A RESULT...VICINITY SHOWERS
ARE INCLUDED IN THE KCHS TAF FROM 16-22Z UNTIL CONFIDENCE IN
TIMING/COVERAGE IMPROVES. HAVE KEPT MENTION OF ANY PRECIPITATION
OUT OF THE KSAV TAF SINCE COVERAGE WILL BE LIMITED ACROSS
SOUTHEAST GA. ANY CEILINGS WILL REMAIN VFR OUTSIDE OF
CONVECTION...WITH CLEARING EXPECTED TONIGHT.

EXTENDED AVIATION...VFR CONDITIONS WILL PREVAIL. GUSTY WINDS ARE
POSSIBLE FRIDAY AFTERNOON.

&&

.MARINE...
WINDS/SEAS WILL BE FAIRLY LOW THROUGH TODAY...THEN WINDS INCREASE
OUT OF THE SW AND W TONIGHT AS A COLD FRONT PUSHES THROUGH THE
WATERS. WIND SPEEDS WILL TOP OUT AROUND 15 KT BUT THE OFFSHORE
FETCH WILL LIMIT THE BUILDING OF SEAS TO NO HIGHER THAN 4 FT.

FRIDAY THROUGH TUESDAY...A NORTHWEST FLOW WILL DEVELOP ON FRIDAY IN
WAKE OF A DEPARTING COLD FRONT. A SECONDARY COLD FRONT WILL THEN
MOVE THROUGH BY FRIDAY EVENING...WITH A STRONGER NORTHERLY SURGE
DEVELOPING IN ITS WAKE FRIDAY NIGHT INTO EARLY SATURDAY...POSSIBLY
RESULTING IN SMALL CRAFT ADVISORY CONDITIONS OVER A PORTION OF THE
WATERS.

CONDITIONS WILL THEN IMPROVE LATER IN THE WEEKEND WITH WINDS/SEAS
EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH
EARLY NEXT WEEK.

&&

.TIDES/COASTAL FLOODING...
HIGH ASTRONOMICAL TIDES AND FAVORABLE NORTH/NORTHEAST WINDS COULD
LEAD TO MINOR SALTWATER INUNDATION NEAR THE COAST DURING THE HIGH
TIDE FRIDAY AND 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.

&&

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

&&

$$

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