Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 222348
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
748 PM EDT TUE JUL 22 2014

.SYNOPSIS...
HIGH PRESSURE WILL PREVAIL IN THE ATLANTIC THROUGH LATE WEEK...
WHILE AN INLAND TROUGH OF LOW PRESSURE APPROACHES THE COASTLINE
THURSDAY AND FRIDAY. THE SURFACE TROUGH WILL DISSIPATE DURING THE
WEEKEND...BEFORE A COLD FRONT APPROACHES EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
THE UPPER LOW CONTINUES TO SPIN OVER SOUTHERN LOUISIANA THIS
EVENING...SLOWLY RETROGRADING TO THE WEST. MEANWHILE A MESOSCALE
LOW SPINS OVER SOUTHWEST GEORGIA WITH BANDS OF CONVERGENCE
SPURRING SHOWERS OVER OUR FAR INLAND GEORGIA COUNTIES TO THE WEST OF
SAVANNAH ALONG THE I-16 CORRIDOR. WITH THE LOSS OF DAYTIME HEATING
MOST OF THE ACTIVITY WILL WANE BY LATE EVENING ACROSS INLAND
AREAS WHILE CONVECTION RE-FIRES OVER THE COASTAL WATERS LATER
TONIGHT...PERHAPS BRUSHING SOME OF BEACHES OF SOUTH CAROLINA
DEPENDENT ON THE PROGRESSION OF THE LAND BREEZE AFTER MIDNIGHT.
MOSTLY CLOUDY SKIES WILL PREVAIL OVERNIGHT WITH LOWS IN THE LOWER
70S.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
WEDNESDAY...THE CLOSED LOW ALOFT PARTLY RESPONSIBLE FOR THE
PERSISTENT UNSETTLED WEATHER WILL CONTINUE TO RETROGRADE WESTWARD
AND DISSIPATE...ALLOWING THE UPPER LEVEL RIDGE OVER THE ATLANTIC TO
PUSH CLOSER TO THE SOUTHEAST STATES. AT THE SURFACE...A TROUGH WILL
SET UP INLAND ON WEDNESDAY...WHILE HIGH PRESSURE OFFSHORE STRUGGLES
TO MAKE SIGNIFICANT PROGRESS BEYOND THE COASTAL COUNTIES. THIS
SHIFTING PATTERN WILL SUPPORT A MORE SUMMERTIME CONVECTIVE
SCENARIO...WITH ACTIVITY OVER THE MARINE ZONES AND COASTAL COUNTIES
DURING THE MORNING SPREADING INLAND WITH THE SEABREEZE BY THE
AFTERNOON HOURS. PRECIPITABLE WATER VALUES ARE STILL QUITE HIGH NEAR
2 INCHES THROUGH THE DAYTIME PERIOD...SUGGESTING THAT SCATTERED
THUNDERSTORMS COULD PRODUCE HEAVY DOWNPOURS...ESPECIALLY WHERE
BOUNDARY INTERACTIONS SLOW STORM PROGRESSION. HOWEVER...STORM
MOTIONS WILL BE SLIGHTLY FASTER THAN PREVIOUS DAYS...SO OVERALL
FLOOD THREAT APPEARS LOWER. RAIN COVERAGE WILL DIMINISH OVER LAND
BY THE EVENING TIME FRAME. EXPECT HIGH TEMPERATURES TO BE SEVERAL
DEGREES WARMER THAN TODAY/TUESDAY...REACHING THE LOW TO MID 90S
INLAND.

THURSDAY...THE AXIS OF AN UPPER LEVEL TROUGH WILL BE MOVING
EAST/SOUTHEAST TOWARD THE APPALACHIAN REGION...ALLOWING THE INLAND
SURFACE TROUGH TO AMPLIFY ACCORDINGLY. MID LEVEL WESTERLY FLOW
WILL STRENGTHEN AHEAD OF THE APPROACHING TROUGH AXIS...AND
FORECAST MODEL SOUNDINGS SHOW PRECIPITABLE WATER VALUES DROPPING
TO 1.75 INCHES OR LESS AND A CAPPING INVERSION PERSISTING INTO THE
EARLY AFTERNOON. CONVECTIVE COVERAGE COULD BE MORE LIMITED
INITIALLY...BEFORE INCREASING LATE DAY INTO THE EVENING HOURS AS
SHORTWAVE ENERGY NEARS THE REGION AND LOW LEVEL CONVERGENCE
INCREASES. HAVE INDICATED THUNDERSTORM CHANCES PEAKING IN THE 30
TO 40 PERCENT RANGE FOR SOUTH CAROLINA ZONES...HIGHEST CHARLESTON
TRI COUNTY AREA...WHILE ADVERTISING LOWER POPS IN THE 20 TO 30
PERCENT RANGE SOUTHEAST GEORGIA FARTHER AWAY FROM SYNOPTIC SCALE
FORCING. THE DOWNSLOPE FLOW WILL SUPPORT WARMER TEMPERATURES...
WITH HIGHS SOLIDLY INTO THE MID 90S AWAY FROM THE IMMEDIATE COAST
WHERE THE SEA BREEZE COULD REMAIN PINNED.

FRIDAY...THE TROUGH AT THE SURFACE AND ALOFT WILL SLIP TOWARD THE
COASTLINE...AND EXPECT DECENT THUNDERSTORM COVERAGE AS A RESULT.
HAVE INDICATED RAIN CHANCES IN THE 30 TO 40 PERCENT RANGE TO
ACCOUNT FOR INCREASING DEEP LAYER MOISTURE. WEAKENING DOWNSLOPE
FLOW AND INCREASED CLOUD COVER COULD KEEP HIGH TEMPERATURES IN
THE LOW 90S AWAY FROM THE COAST.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
THE MID AND UPPER LEVEL TROUGH WILL WEAKEN OVER THE EASTERN UNITED
STATES OVER THE WEEKEND...AS RIDGING TRIES TO EXPAND SOUTH OF THE
REGION. THE UPPER TROUGH WILL THEN GET REINFORCED AND EXPAND
SOUTHWARD EARLY NEXT WEEK FROM ENERGY DROPPING ACROSS THE GREAT
LAKES REGION. AT THE SURFACE...ATLANTIC HIGH PRESSURE WITH A WEAK
TROUGH OF LOW PRESSURE INLAND WILL PREVAIL THROUGH THE
WEEKEND...BEFORE THE STRENGTHENING UPPER TROUGH DRIVES A COLD FRONT
TOWARD THE AREA FROM THE NORTHWEST EARLY NEXT WEEK. EXPECT MAINLY
DIURNAL SCATTERED SHOWERS AND THUNDERSTORMS OVER THE WEEKEND...BUT
COVERAGE COULD INCREASE EARLY NEXT WEEK AS THE FRONT NEARS AND
MOISTURE INCREASES. TEMPERATURES SHOULD BE NEAR NORMAL FOR MOST OF
THE LONG TERM PERIOD.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
THE WEATHER PATTERN SUGGESTS MAINLY VFR CONDITIONS WILL PERSIST
THROUGH 00Z THURSDAY. OVERNIGHT...BRIEF PERIODS OF MVFR CIGS ARE
POSSIBLE NORTH OF SAVANNAH AS LOW LEVEL SPEED CONVERGENCE IS
FORECAST TO INCREASE OVERNIGHT. SMALL CHANCE FOR MVFR CIGS AT THE
KCHS TERMINAL LASTING GREATER THAN AN HOUR. CANNOT RULE OUT SOME
LIGHT FOG OR LOW CLOUDS AT EITHER TERMINAL. ON WED...MODELS
INDICATE POTENTIAL FOR SEA BREEZE CONVECTION ALONG BY AFTERNOON
WITH LESSER CHANCES ALONG THE GEORGIA SEA BREEZE.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS EXPECTED TO PREVAIL.
BRIEF FLIGHT RESTRICTIONS POSSIBLE WITHIN SCATTERED MAINLY
AFTERNOON/EARLY EVENING SHOWERS AND THUNDERSTORMS. THE BEST COVERAGE
IS EXPECTED FRIDAY AND SATURDAY.

&&

.MARINE...
THE FLOW INCREASES OUT OF THE SOUTH TONIGHT AS THE TROUGH LIFTS
INLAND AND SOME NOCTURNAL JETTING TAKES PLACE. WINDS WILL RUN
10-15 KT WITH SEAS BUILDING AS HIGH AS 4 FT OVER OUTER WATERS.

ATLANTIC HIGH PRESSURE WILL BUILD OVER THE WATERS FROM MID WEEK
THROUGH THE WEEKEND...WHILE A TROUGH OF LOW PRESSURE LINGERS
INLAND. AS A RESULT...A GENERAL SOUTH/SOUTHWEST FLOW IS EXPECTED
TO PREVAIL. THE STRONGEST WINDS WILL OCCUR DURING THE
AFTERNOON/EARLY EVENING HOURS ALONG THE LAND/SEA INTERFACE DUE TO
THE SEA BREEZE...AND AS A NOCTURNAL SURGE DEVELOPS OVER THE
COASTAL WATERS DURING THE EVENING/LATE NIGHT HOURS. WINDS COULD
PEAK IN THE 15 TO 20 KT DURING THESE NIGHTTIME INCREASES...WITH
THE POTENTIAL FOR HIGHER GUSTS. SEAS WILL GENERALLY RANGE FROM 2
TO 4 FT.

&&

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

&&

$$

NEAR TERM...
SHORT TERM...WMS
LONG TERM...JAQ
AVIATION...
MARINE...






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