Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 221132
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
732 AM EDT WED OCT 22 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO GEORGIA AND SOUTH CAROLINA TODAY AND
THEN DOMINATE INTO NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
IN THE WAKE OF THE OVERNIGHT FRONTAL PASSAGE...STRONG SUBSIDENCE AND
A DEEP LAYERED DRY AIR MASS WILL ENCOMPASS GEORGIA AND SOUTH CAROLINA
TODAY WITH SUNSHINE ON TAP. SURFACE WINDS FROM THE N TO NNW WILL USHER
IN A COOLER AIR MASS...LOW LEVEL THICKNESS VALUES SUPPORTIVE OF AFTERNOON
TEMPS NEARLY 10 DEGREES COOLER THAN ON TUE. NO SIGNIFICANT CHANGES
TO THE FORECAST TODAY...HIGHS IN THE LOWER 70S WITH NNW WINDS 10
TO 15 MPH WITH GUSTS NEAR 20 MPH AT TIMES THROUGH EARLY AFTERNOON.

INLAND AREAS SHOULD DECOUPLE QUICKLY AFTER SUNSET THIS EVENING BUT
LIGHT NORTHERLY SURFACE WINDS COULD KEEP GOING INTO THE NIGHT RIGHT
ALONG THE COAST...INCLUDING BEACHES AND BARRIER ISLANDS. THIS WILL
ALLOW FOR STRONG RADIATIONAL COOLING WEST OF U.S. 17 WITH SOME
NORMALLY COLDER RURAL/INLAND AREAS NEARING 40 DEGREES BY DAWN ON
THURSDAY. LOW MOST AREAS IN THE LOW TO MID 40S AWAY FROM THE
OCEAN.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
THURSDAY...A DEEP LAYER RIDGE...CENTERED FROM THE GREAT LAKES SOUTHWARD
TO THE GULF COAST...WILL BE THE DOMINANT FEATURE. AT THE SURFACE...LIGHT
NORTH-NORTHWEST WINDS.THERE COULD BE A WEAK SEA BREEZE RIGHT AT THE
COAST BY LATE AFTERNOON. THE COOLEST TEMPERATURES OF THIS PERIOD WITH
HIGHS ONLY IN THE LOWER 70S AND LOWS IN THE LOWER TO MID 40S INLAND
TO THE LOWER 50S AT THE COAST.

FRIDAY...GLOBAL MODELS ALREADY HAVE SOME DIFFERENCES WITH THE
EVOLUTION OF THE NEXT UPPER TROUGH THAT MOVES DOWN IN THE UPPER
LEVEL NORTHWEST FLOW. THE ECMWF SEEMS TO BE THE OUTLIER WITH
PRODUCING A MUCH STRONGER SHORT WAVE THAT APPROACHES THE REGION BY
LATE DAY...WITH THE NAM AND THE GFS MUCH WEAKER/BROAD AND FURTHER NORTH.
HAVE GONE WITH THE WEAKER SOLUTIONS AND KEPT OUT ANY MENTION OF
PRECIP. AGAIN...LOW LEVEL FLOW WILL BE LIGHT NORTHWEST...WITH A LATE
DAY SEA BREEZE POSSIBLE NEAR THE COAST. NOTE: SEA BREEZES ARE
GETTING MORE DIFFICULT GIVEN TEMPERATURE DIFFERENCES BETWEEN THE
LAND AND WATER ARE BECOMING LESS...EVEN WITH HIGHS IN THE MID 70S.
FRIDAY NIGHT...LIGHT NORTHERLY LOW LEVEL FLOW WITH A SURFACE RIDGE
NORTHWEST OF THE AREA OVER THE TN RIVER VALLEY. EXPECT TEMPS TO
RADIATE DOWN TO THE MID 40S INLAND AND LOWER 50S COAST.

SATURDAY...CONTINUED BROAD NORTHWEST UPPER LEVEL FLOW WITH A SURFACE
RIDGE CENTERED WEST-NORTHWEST OF THE AREA. UPPER LEVEL HEIGHTS/TEMPS
MODERATE SOME. THUS...EXPECT SLIGHTLY WARMER MAX TEMPS IN THE MID TO
UPPER 70S WITH SUNNY SKIES.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
GLOBAL MODELS IN GOOD AGREEMENT THROUGH MONDAY THEN START TO
DIVERGE. A SPRAWLING DEEP LAYER RIDGE BUILDS IN FROM THE WEST SUNDAY
AND THEN MOVES JUST OFF SHORE BY LATER MONDAY AS AN ANOTHER UPPER
TROUGH TAKES SHAPE OVER THE CENTRAL U.S. THIS NEXT TROUGH IS WHERE
THE MODELS DIVERGE. THE ECMWF IS SLOWER AND MORE FULL LATITUDE IN
ITS EXTENT BY TUESDAY...WHILE THE GFS IS WEAKER AND FASTER...HOLDING
THE BULK OF THE ENERGY WELL NORTH OVER THE GREAT LAKES. ODDLY...
MODELS COME BACK TO CLOSER AGREEMENT BY WEDNESDAY AS BOTH SHOW A
BROAD TROUGH/NEARLY ZONAL FLOW OVER THE CENTRAL AND EASTERN U.S. AND A
DEEP LAYER RIDGE DEPARTING OVER THE ATLANTIC. THROUGH THIS
PERIOD...GLOBAL MODELS KEEP THE MAIN TROPICAL MOISTURE ASSOCIATED
WITH TD9...CURRENTLY OVER THE BAY OF CAMPECHE...WELL SOUTH OF THE
AREA.

EXPECT ABOVE NORMAL TEMPERATURES THROUGH THIS PERIOD AS A DEEP LAYER
RIDGE LARGELY DOMINATES. MONDAY THROUGH WEDNESDAY...LOW LEVEL FLOW
VEERS TO SOUTHEAST...WHICH WILL HELP TO ADVECT BETTER LOW LEVEL
MOISTURE INTO THE AREA. THUS...HAVE CONTINUED TREND OF SLIGHT CHANCE
POPS FOR SHOWERS OVER MAINLY THE COASTAL AND ATLANTIC WATERS.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
VFR. NORTH WINDS MAY BE A BIT GUSTY INTO EARLY AFTERNOON BEFORE
DIMINISHING AFTER MID AFTERNOON.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS EXPECTED TO PREVAIL THROUGH
THE REST OF THE WEEK AND INTO THE WEEKEND FOR BOTH KCHS AND KSAV.

&&

.MARINE...
COLDER LOW LEVEL AIR WILL ADVECT OVER THE WATERS THIS MORNING WITH
SURFACE WINDS VEERING NORTHERLY IN THE WAKE OF A DRY COLD FRONT
OVERNIGHT. A BRIEF 20 KT SURGE IS ANTICIPATED THIS MORNING WITH
OCCASIONAL HIGHER GUSTS FROM 09Z TO 15Z BUT THERE IS NOT ENOUGH
EVIDENCE IN FORECAST SOUNDINGS TO RAISE ANY SMALL CRAFT ADVISORIES
AT THIS STAGE. SEAS WILL BUILD TO 3 TO 4 FT NEAR SHORE AND 4-5 FT
BEYOND 20 NM OFF THE GEORGIA COAST LATER THIS MORNING BUT CAPPED
SEAS BELOW 6 FT OUT NEAR THE GULF STREAM. THE SURGE WILL BEGIN TO
EBB AFTER 18Z WITH ENOUGH PRES AND THERMAL GRADIENT TONIGHT TO
SUPPORT A SOLID 15 KT FOR TONIGHT.

THURSDAY THROUGH MONDAY...HIGH PRESSURE WILL REMAIN NORTHWEST OF
THE REGION THROUGH SUNDAY THEN SHIFT TO NORTH AND EAST OF THE AREA
BY LATER MONDAY. NO HIGHLIGHTS ARE EXPECTED THROUGH EARLY NEXT
WEEK WITH WINDS 15 KT OR LESS AND SEAS 4 FT OR LESS.

&&

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

&&

$$

NEAR TERM...
SHORT TERM...RFM
LONG TERM...RFM
AVIATION...
MARINE...RFM






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