Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 210230
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1030 PM EDT MON OCT 20 2014

.SYNOPSIS...
A TROUGH OF LOW PRESSURE WILL CROSS THE AREA AND WILL MOVE OFF THE
COAST OVERNIGHT. A COLD FRONT WILL MOVE THROUGH THE REGION TUESDAY
NIGHT...WITH HIGH PRESSURE BUILDING IN ITS WAKE THROUGH LATE IN
THE WEEK.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
PER ISOLATED SHOWERS DEVELOPING ACROSS INLAND COUNTIES...EXPANDED
SLIGHT CHANCE POPS INTO THESE AREAS FOR A FEW HOURS OVERNIGHT.
ADVECTION OF DRIER AIR WILL END THE CHANCE FOR ANY INLAND PRECIP
BY LATER TONIGHT.

LATE MONDAY EVENING...ISOLATED SHOWERS HAD DEVELOPED SOUTH OF I-16
AND WEST OF I-95...NEAR THE ALTAMAHA RIVER...WHERE LOW-LEVEL
CONVERGENCE COINCIDED WITH A PLUME OF ELEVATED SURFACE-850 MB
THETA-E/SURFACE LIFTED INDICES AROUND ZERO. LATEST HIGH RESOLUTION
GUIDANCE HAS CONVERGED ON A SOLUTION SUGGESTING THAT THESE SHOWERS
WILL EXPAND IN COVERAGE TOWARD THE N/E IN RESPONSE TO AN
APPROACHING/ AMPLIFYING SHORTWAVE TROUGH ALOFT AND THE PASSAGE OF
AN ASSOCIATED SURFACE TROUGH OVERNIGHT. FINE-TUNED POPS
ACCORDINGLY...TAPERED FROM CHANCE FAR SOUTH AND SOUTHERN/CENTRAL
COASTAL LOCATIONS AND ADJACENT COASTAL WATERS TO SLIGHT CHANCE
ELSEWHERE. SLIGHT CHANCE POPS LINGER THROUGH THE NIGHT ALONG THE
CHARLESTON COUNTY COAST...BUT POPS DROP OFF TO VIRTUALLY ZERO
INLAND AFTER THE SURFACE TROUGH PASSES LATER TONIGHT.

THE STRONG SUBSIDENCE INVERSION BASED AROUND 800 MB AS DEPICTED BY
THE 00Z KCHS AND KJAX SOUNDINGS WILL WEAKEN AS THE UPPER SHORTWAVE
TROUGH APPROACHES...BUT THIS FEATURE WILL PERSIST SUFFICIENTLY TO
LIMIT DEPTH/PERSISTENCE OF MOIST UPDRAFTS. THUS...A MENTION OF
THUNDER IS NOT JUSTIFIED OVER LAND.

MEANWHILE...PRECIPITATION WILL GRADUALLY SHIFT OFFSHORE LATE
TONIGHT INTO TUESDAY MORNING. HOWEVER...MODELS SUGGEST THAT A WEAK
SURFACE WAVE COULD DEVELOP OVER THE GULF STREAM LATE TONIGHT. THIS
FEATURE COULD PROLONG SHOWERS OVER COASTAL WATERS AND PERHAPS EVEN
ALONG THE IMMEDIATE COAST INTO TUESDAY MORNING.

OTHERWISE...TEMPERATURES WILL BOTTOM OUT IN THE 50S MOST AREAS
TONIGHT...ESPECIALLY AS W/NW WINDS PUSH DRIER AIR INTO THE REGION IN
THE WAKE OF THE SURFACE TROUGH PASSAGE LATE. ON THE BEACHES...
TEMPERATURES COULD HOLD IN THE 60S MOST OF THE NIGHT.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
TUESDAY...LIGHT RAIN/SHOWERS WILL CONTINUE TO LIFT NORTHEAST AND
FURTHER OFFSHORE FROM THE AREA EARLY AS MOISTURE ASSOCIATED WITH A
PARENT LOW PRESSURE SYSTEM SLOWLY SHIFTS OFF THE NORTHEAST COAST.
WEST/NORTHWEST FLOW ALONG THE SOUTHERN PERIPHERY OF THE LOW WILL
HELP PRODUCE FAIRLY WARM TEMPS AHEAD OF A DRY COLD FRONT APPROACHING
THE AREA LATE. LATEST 1000-850MB THICKNESS VALUES SUPPORT OVERALL
HIGH TEMPS NEAR 80S DEGREES AND GIVEN A DOWNSLOPING WIND COMPONENT
ALONG WITH MOSTLY SUNNY SKIES...HAVE MAINTAINED HIGH TEMPS IN THE
LOWER 80S FOR MOST LOCATIONS.

TUESDAY NIGHT INTO WEDNESDAY...A DRY COLD FRONT WILL SHIFT THROUGH
THE AREA FROM THE NORTH/NORTHWEST TUESDAY NIGHT...WITH LITTLE TO NO
IMPACT OVER THE SOUTHEAST IN REGARDS TO PRECIP. HOWEVER...COOLER
CONDITIONS ARE ANTICIPATED BEHIND THE FRONT AS A NORTH/NORTHWEST
FLOW DEVELOPS ALONG THE SOUTHEAST SIDE OF HIGH PRESSURE CENTERED
OVER THE MIDWEST. TUESDAY NIGHT TEMPS SHOULD REMAIN IN THE LOW/MID
50S FOR MOST AREAS...BUT TEMPS COULD DIP INTO THE UPPER 40S INLAND
WHERE FROPA OCCURS EARLIEST. HIGH TEMPS WILL BE SOME 5-10 DEGREES
COOLER THAN THE PREVIOUS DAY ON WEDNESDAY AS THE NORTH/NORTHWEST FLOW
PERSISTS BETWEEN HIGH PRESSURE CENTERED OVER THE MIDWEST AND A BROAD
LOW PRESSURE SYSTEM JUST OFF THE NORTHEAST COAST. IN GENERAL...HIGH
TEMPS SHOULD RANGE IN THE LOW/MID 70S...COOLEST OVER SOUTHEAST SOUTH
CAROLINA. WEDNESDAY NIGHT LOWS SHOULD ALSO BE THE COOLEST OF THE
WEEK...WITH PERHAPS A SMALL CONTRIBUTION FROM RADIATIONAL COOLING.
IN GENERAL...LOWS SHOULD DIP INTO THE MID 40S INLAND TO LOW 50S NEAR
THE COAST.

THURSDAY...VERY LITTLE CHANGE IS ANTICIPATED IN REGARDS TO THE DRY
WEATHER PATTERN...BUT SFC WINDS SHOULD GRADUALLY BACK TO NORTHWEST
OVER THE COURSE OF THE DAY. THIS SUPPORTS A GRADUAL MODIFICATION OF
TEMPS...WITH AFTERNOON HIGHS 1-2 DEGREES WARMER THAN WEDNESDAY...BUT
STILL IN THE LOW/MID 70S OVER MOST LOCATIONS.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
GLOBAL MODEL SOLUTIONS NOW VERY DIFFERENT FOR THE MIDDLE TO LATER
PART OF THE PERIOD. THE LATEST SOLUTIONS NOW SHOW THE DEEP/CLOSED
UPPER LOW OFF THE NEW ENGLAND COAST TO CONTINUE SLOWLY MOVING
EASTWARD FRIDAY AS A DEEP LAYER RIDGE DEVELOPS OVER THE SOUTHWESTERN
U.S. STATES BY FRIDAY. BETWEEN THESE TWO FEATURES...A SHORT WAVE UPPER
TROUGH DROPS SOUTHEASTWARD FROM THE GREAT LAKES FRIDAY...TO OFF THE
MID ATLANTIC COAST BY SATURDAY. THEN A DEEP LAYER RIDGE BUILDS EASTWARD
ACROSS THE SOUTH AND SOUTHEAST STATES SUNDAY AND MONDAY. THIS IS
DRASTICALLY DIFFERENT FROM SOLUTIONS 24 HOURS AGO...WHICH
FEATURED AN UPPER LOW OVER THE GULF STATES AND ASSOCIATED SURFACE
LOW MOVING UP FROM THE GULF ACROSS FL THEN INTO THE SOUTHWEST
ATLANTIC. THIS NEWER SOLUTION IS MUCH DRIER AND WARMER THAN
PREVIOUSLY EXPECTED. GIVEN THE EXTREME UNCERTAINTY...MADE ONLY MINOR
CHANGES TO TEMPERATURES THROUGH THE PERIOD...GENERALLY HOLDING THEM
NEAR TO SLIGHTLY ABOVE NORMAL. DID INTRODUCE SLIGHT CHANCE POPS FOR
MONDAY WITH SOME MOISTURE RETURN ON THE EAST SIDE OF THE RIDGE...BUT
CONFIDENCE QUITE LOW FOR POPS GIVEN ABOVE DISCUSSION.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
VFR THROUGH TUESDAY. LOW PROBABILITY FOR SHOWERS/BRIEF FLIGHT
RESTRICTIONS 03Z-06Z UNTIL 09-12Z...ESPECIALLY AT KSAV...BUT LIMITED
MENTION TO VCSH WITHIN 00Z TAFS.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED AT BOTH CHS
AND SAV TERMINALS THROUGH THIS WEEKEND.

&&

.MARINE...
OVERNIGHT...AHEAD OF AN APPROACHING SURFACE TROUGH/ON THE PERIPHERY
OF HIGH PRESSURE RETREATING OFFSHORE/AWAY FROM THE COAST...SE
WINDS OVER GA WATERS AND S/SW WINDS OVER SC WATERS...MAINLY LESS
THAT 15 KT....WILL VEER WITH TIME AND WILL EVENTUALLY TURN TOWARD
THE W/NW AS THE SURFACE TROUGH PASSES LATE TONIGHT. SEAS WILL HOLD AROUND
2-3 FT...HIGHEST ACROSS THE OUTER GA WATERS. SCATTERED SHOWERS
ARE EXPECTED...WITH GREATEST COVERAGE SOUTH OF AMZ350...AND ISOLATED
THUNDERSTORMS CANNOT BE RULED OUT LATE ESPECIALLY BEYOND 20 NM.

TUESDAY AND WEDNESDAY...CONDITIONS ARE EXPECTED TO BE WELL BELOW
SMALL CRAFT ADVISORY LEVELS TUESDAY AS A BROAD TROUGH OF LOW
PRESSURE BEGINS TO SLOWLY SHIFT OFF THE NORTHEAST COAST. IN
GENERAL...WESTERLY FLOW WILL REMAIN AT OR BELOW 15 KTS WITH SEAS NO
HIGHER THAN 3 FT. A DRY COLD FRONT WILL THEN APPROACH THE AREA AND
SHIFT OVER THE COASTAL WATERS FROM NORTH TO SOUTH TUESDAY
NIGHT...RESULTING IN A FAIR AMOUNT OF COLD AIR ADVECTION OVER THE
WATERS WHILE HIGH PRESSURE BUILDS FROM THE NORTHWEST. AS A
RESULT...WINDS/SEAS WILL BE ENHANCED POST FROPA LATE TUESDAY INTO
WEDNESDAY...BUT CONDITIONS SHOULD REMAIN JUST BELOW SMALL CRAFT
ADVISORY LEVELS. IN GENERAL...WEST WINDS WILL BECOME NORTH BETWEEN
15-20 KTS BEHIND THE FRONT WHILE SEAS BUILD TO 3-4 FT...HIGHEST IN
OFFSHORE GEORGIA WATERS.

WEDNESDAY NIGHT THROUGH SATURDAY...WINDS AND SEAS ARE EXPECTED TO
REMAIN BELOW ANY HIGHLIGHTS AS A BROAD AREA OF HIGH PRESSURE REMAINS
TO THE NORTHWEST OF THE REGION. BY SATURDAY...AN UPPER LEVEL
DISTURBANCE WILL MOVE OFF THE NORTH CAROLINA COAST. THIS FEATURE
WILL HELP TO INCREASE THE NORTHWEST WINDS...BUT STILL NOT EXPECTING
WINDS/SEAS TO REACH SMALL CRAFT ADVISORY LEVELS.

&&

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

&&

$$

NEAR TERM...SPR
SHORT TERM...
LONG TERM...
AVIATION...SPR
MARINE...SPR






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