Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 311930
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
330 PM EDT FRI OCT 31 2014

.SYNOPSIS...
A STRONG COLD FRONT WILL MOVE THROUGH LATE TONIGHT...FOLLOWED BY
UNSEASONABLY COLD HIGH PRESSURE INTO EARLY NEXT WEEK. THE HIGH WILL
EVENTUALLY SHIFT OFFSHORE DURING THE MIDDLE OF NEXT WEEK AS ANOTHER
COLD FRONT APPROACHES FROM THE NORTHWEST.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
THIS EVENING AND TONIGHT...RAIN-FREE CONDITIONS WILL PERSIST THIS
EVENING BETWEEN LOW PRESSURE LIFTING NORTHEAST OFFSHORE AND A LARGE
TROUGH OF LOW PRESSURE CURRENTLY TO OUR NORTHWEST. CONDITIONS WILL
THEN CHANGE TONIGHT AS A MID/UPPER LVL LOW CURRENTLY OVER THE
MIDWEST DIVES SOUTHEAST ALONG THE WESTERN EDGE OF THE LARGE
MID/UPPER LVL TROUGH...CAUSING AN IMPRESSIVE DIGGING/AMPLIFYING
TREND AS THE TROUGH APPROACHES THE SOUTHEASTERN UNITED STATES. AS
THIS PROCESS UNFOLDS...A SURFACE LOW WILL DEVELOP NEAR THE EASTERN
NORTH CAROLINA/SOUTH CAROLINA BORDER...HELPING A POWERFUL COLD FRONT
TO SWEEP THROUGH THE AREA FROM THE WEST. WRAP-AROUND MOISTURE
ASSOCIATED WITH THE DEVELOPING SURFACE LOW COULD PRODUCE A FEW
SHOWERS ACROSS PORTIONS OF SOUTHEAST SOUTH CAROLINA LATE...BUT THE
MAIN CONCERN WILL BE SURFACE WINDS RAPIDLY INCREASING LATE TONIGHT
WITH THE ONSET OF INTENSE COLD AIR ADVECTION BEHIND THE FRONT. IN
GENERAL...WINDS SHOULD GUST BETWEEN 15-20 MPH WITHIN A FEW HOURS OF
DAYBREAK SATURDAY MORNING. OVERNIGHT TEMPS WILL QUICKLY COOL OFF
POST FROPA...INTO THE LOW/MID 40S. WE COULD EVEN SEE A FEW TEMPS DIP
INTO THE UPPER 30S WELL INLAND.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
SATURDAY...SIGNIFICANT CHANGES ARE IN THE OFFING FOR THE AREA AS AN
INCREDIBLY COLD AND POWERFUL SYSTEM FOR EARLY FALL AFFECTS THE
EASTERN U.S. THIS WEEKEND. MODELS ARE SIMILAR IN SHOWING A POTENT
SHORTWAVE DIGGING SOUTH ACROSS THE MID MISSISSIPPI VALLEY TONIGHT
AND BRIEFLY CUTTING OFF ACROSS SOUTH CAROLINA ON SATURDAY AS A
STRONG 115 KT JET STREAK ROUNDS THE BASE OF THE MEAN TROUGH AXIS. AN
ARCTIC COLD FRONT WILL BE DRIVEN QUICKLY SOUTH VIA STRONG COLD AIR
ADVECTED NOTED IN THE WAKE OF THE SHORTWAVE...WHICH WILL QUICKLY
ENCOMPASS THE SOUTHEAST STATES OVER THE WEEKEND...BRING EXTREMELY
CHILLY CONDITIONS TO THE REGION FOR EARLY NOVEMBER. BY SATURDAY
AFTERNOON WHEN THE UPPER LOW IS OVERHEAD...500 HPA TEMPERATURES ARE
FORECAST TO DROP IN THE -22 TO -26C RANGE WITH 850 HPA TEMPERATURES
FALLING TO -2 TO -5C. IT SHOULD BE NOTED 850 HPA TEMPERATURES OF
THIS MAGNITUDE FOR EARLY NOVEMBER ARE ABOUT 12 STANDARD DEVIATIONS
BELOW NORMAL--CERTAINLY A TESTAMENT TO HOW COLD THIS AIRMASS WILL BE.

TEMPERATURES: CONSIDERABLE CLOUD COVER WITHIN THE ASSOCIATED UPPER
LOW/S COLD POCKET COUPLED WITH SUCH COLD LOW/MID-LEVEL THERMAL
PROFILES WILL SUPPORT HIGHS ONLY IN THE UPPER 40S ACROSS THE NORTH
TO THE MID 50S ACROSS THE SOUTH. IF SOME MODEL DATA SETS PROVE TO BE
CORRECT...SUCH AS THE NAM-12...AND/OR PRECIPITATION IS MUCH MORE
WIDESPREAD THAN EXPECTED...THE RESULTING DIABATIC COOLING COULD KEEP
TEMPERATURES IN THE 40S FOR ALL BUT THE FAR SOUTH WHERE LOWER 50S
COULD BE REALIZED. ITS CERTAINLY A TOUGH CALL ON HIGH TEMPERATURES
WITH THE EVENTUAL DIURNAL THERMAL CURVES BEING DRIVEN BY THE
AREA/INTENSITY OF ANY PRECIPITATION THAT DEVELOPS. IF THE CURRENT
FORECAST HOLDS...THE RECORD LOW MAXIMUM TEMPERATURE OF 56 /1993/ AT
THE CHARLESTON AIRPORT COULD FALL. SEE THE CLIMATE SECTION BELOW FOR
ADDITIONAL INFORMATION. LOWS SATURDAY NIGHT WILL RANGE FROM THE MID
30S ACROSS THE SOUTHWEST AREAS TO THE UPPER 30S/NEAR 40 ELSEWHERE.
THE ATMOSPHERE LOOKS A BIT TOO DRY AND THE WIND TOO HIGH TO SUPPORT
ANYTHING MORE THAN PATCHY FROST ACROSS THE FAR INTERIOR SOUTHEAST
GEORGIA...ROUGHLY FROM MILLEN SOUTH TO TATTNALL AND POINTS WEST. A
FROST ADVISORY IS NOT ANTICIPATED ATTM.

PRECIPITATION: MODELS ARE SIMILAR IN DEPICTING VARIOUS AMOUNT OF QPF
ACROSS MAINLY SOUTHEAST SOUTH CAROLINA SATURDAY AFTERNOON AS UVV
AHEAD OF THE UPPER LOW SPREADS ACROSS THE AREA. MOST OF THE GUIDANCE
KEEPS THE BULK OF THE PRECIPITATION TO THE NORTH ACROSS THE MIDLANDS
AND PEE DEE REGIONS...ONLY GIVING SOUTHEAST SOUTH CAROLINA A
QUICK...GLANCING BLOW. WILL LIMIT POPS TO 20-40 PERCENT ACROSS THE
CENTRAL AND NORTHERN PARTS OF THE FORECAST AREA FOR NOW...HIGHEST
ACROSS THE FAR NORTH...ROUGHLY NORTH OF I-26...BUT ANY SLIGHT
SOUTHWARD DEVIATION OF THE UPPER LOW WILL NECESSITATE A HIGHER POP
REGIME. THERE MAY BE JUST ENOUGH DIABATIC COOLING TO SUPPORT SOME
GRAUPEL/SMALL HAIL AT TIMES...MAINLY IN POCKETS OF HEAVIER RAIN
WHERE DIABATIC PROCESSES WILL BE MAXIMIZED. COULD ALSO HEAR A
RUMBLE OR TWO OF THUNDER ACROSS THE NORTH GIVEN THE INCREDIBLE LOW
LAPSE RATES...BUT THE RISK IS JUST TOO LOW TO MENTION JUST YET.

WINDS...BREEZY TO WINDY CONDITIONS ARE LIKELY SATURDAY WITH STRONG
COLD AIR ADVECTION EXPECTED. THE WINDIEST CONDITIONS WILL BE FOUND
SOUTH OF I-16 WHERE MIXING WILL BE MAXIMIZED DUE TO CONSIDERABLY
LESS CLOUD COVER. EXPECT WINDS OF 20-30 MPH WITH GUSTS TO 40-45 MPH
IN THIS AREA...SO A WIND ADVISORY WILL BE ISSUED FOR TATTNALL-EVANS-
BRYAN-CHATHAM-LIBERTY-LONG AND MCINTOSH COUNTIES...FROM 9AM-8PM
SATURDAY. THERE IS A POSSIBILITY WINDS COULD REACH ADVISORY LEVELS
FOR THE SOUTH CAROLINA COASTAL COUNTIES...BUT THE PRESENCE OF
EXTENSIVE CLOUD COVER LOWERS CONFIDENCE ENOUGH TO NOT ISSUE A WIND
ADVISORY FOR THOSE LOCATIONS WITH THIS FORECAST CYCLE. PLAN TO LIMIT
WINDS THERE TO 20-25 MPH WITH GUSTS 35 MPH...OR JUST BELOW WIND
ADVISORY THRESHOLDS.

SUNDAY...TEMPERATURES WILL BEGIN TO MODERATE SOME AS COLD AIR
ADVECTION WANES AND THE CENTER OF THE ARCTIC HIGH SETTLES DIRECTLY
OVERHEAD. HIGHS LOOK TO WARM INTO THE MID-UPPER 50S UNDER MOSTLY
SUNNY SKIES. IT WILL BE DOWN RIGHT COLD SUNDAY NIGHT WITH LOWS
RANGING FROM THE LOWER 30S TO THE MID-UPPER 30S AT THE COAST WITH
LOWER-MID 40S AT THE BEACHES. THERE WILL BE A RISK FOR FROST/FREEZE
CONDITIONS WITH SCATTERED TO WIDESPREAD FROST LIKELY ROUGHLY NORTH
OF A HUGER-SUMMERVILLE-HENDERSONVILLE-CLYO-METTER LINE...BUT AWAY
FROM THE SHORES OF LAKE MOULTRIE. A FROST ADVISORY WILL LIKELY BE
NEEDED FOR THESE AREAS. LOWS AROUND FREEZING ARE POSSIBLE ACROSS
PARTS OF JENKINS-SCREVEN-ALLENDALE AS WELL AS NORTHERN PARTS OF
BERKELEY COUNTY...BUT EXPECT ANY FREEZE DURATIONS TO REMAIN 1-2
HOURS AT BEST. A FREEZE WATCH AND EVENTUALLY A WARNING MAY BE NEEDED
IN LATER FORECAST CYCLES.

MONDAY...WARMER CONDITIONS MONDAY WITH HIGHS IN THE UPPER 60S WITH
LOWS IN THE LOWER 40S INLAND WITH MID-UPPER 40S AT THE COAST. DRY
CONDITIONS WILL PREVAIL.

LAKE WINDS...WINDS WILL BE STRONG AND GUSTY SATURDAY INTO EARLY
SUNDAY BEHIND A STRONG COLD FRONT MOVING THROUGH EARLY SATURDAY.
STRONG COLD AIR ADVECTION OVER THE WARMER LAKE WATERS WILL MAKE FOR
VERY UNSTABLE CONDITIONS WHICH WILL ALLOW STRONG LOW-LEVEL WINDS TO
MIX DOWN TO THE SURFACE...LIKELY AROUND 35 KT AT TIMES...POSSIBLY
CLOSE TO 40 KT. A LAKE WIND ADVISORY REMAINS IN EFFECT.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
HIGH PRESSURE LOOKS TO SLIDE OFFSHORE THROUGH MID WEEK WITH
MODERATING TEMPERATURES GETTING BACK ABOVE NORMAL TUESDAY. A COLD
FRONT LOOKS TO APPROACH LATER IN THE WEEK...POSSIBLY MOVING THROUGH
THURSDAY NIGHT. LIMITED MOISTURE WITH THE FRONT MEANS LITTLE TO NO
RAIN CHANCES HOWEVER.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
VFR CONDITIONS ARE EXPECTED TO PREVAIL AT KCHS AND KSAV THROUGH
18Z SATURDAY. HOWEVER...A STRONG COLD FRONT WILL SHIFT OVER BOTH
TERMINALS LATE TONIGHT. AS FROPA OCCURS...THERE WILL BE A LOW
CHANCE OF MVFR CIGS...MAINLY AT THE CHS TERMINAL. EXPECT STRONG
WINDS POST FROPA...WITH WEST WINDS BECOMING NORTHWEST BY DAYBREAK
SATURDAY AND GUSTING BETWEEN 25-30 KTS BY LATE MORNING INTO EARLY
AFTERNOON.

EXTENDED AVIATION OUTLOOK...MVFR CIGS LIKELY SATURDAY...MAINLY AT
KCHS...ALONG WITH SCATTERED SHOWERS. WEST TO NORTHWEST WINDS WILL BE
THE MAIN IMPACT HOWEVER...GUSTING AROUND 30 KT...ESPECIALLY AT KSAV.
NO IMPACTS EXPECTED SUN-WED.

&&

.MARINE...
THIS EVENING...WINDS/SEAS WILL REMAIN IN A SOMEWHAT RELAXED STATE
EARLY BETWEEN LOW PRESSURE NORTHEAST OF THE WATERS AND A LARGE
TROUGH OF LOW PRESSURE WELL INLAND. IN GENERAL...NORTH WINDS
WILL GRADUALLY BACK TO WEST AND REMAIN AT OR BELOW 15 KTS INTO EARLY
TONIGHT. SEAS SHOULD RANGE BETWEEN 2-4 FT.

CONDITIONS WILL THEN RAPIDLY DETERIORATE LATER TONIGHT AS A POWERFUL
COLD FRONT PUSHES OFFSHORE WITH STRONG COLD AIR ADVECTION AND WINDS
BEHIND IT. GALE FORCE WINDS/GUSTS ARE FORECAST FOR ALL WATERS BEHIND THE
FRONT AND THUS A GALE WARNING IS NOW IN EFFECT FOR ALL COASTAL
WATERS...INCLUDING THE CHS HARBOR BEGINNING AT 10Z SATURDAY. CONDITIONS
WILL LIKELY DETERIORATE OVER GEORGIA WATERS FIRST...AND THERE IS A
CHANCE THE GALE WARNING WILL NEED TO BE STARTED AN HOUR OR SO
EARLIER THAN SOUTH CAROLINA WATERS. REGARDLESS...BRIEF SMALL CRAFT
ADVISORY CONDITIONS SHOULD OCCUR OVER ALL WATERS BEFORE GALE
CONDITIONS OCCUR...BUT GIVEN THE QUICKLY CHANGING CONDITIONS HAVE
OPTED TO GO STRAIGHT INTO GALE WARNINGS FOR ALL WATERS. SEAS WILL
BUILD LATE TONIGHT...PEAKING BETWEEN 3-5 FT NEARSHORE TO 5-7 FT IN
OFFSHORE WATERS BY DAYBREAK.

SATURDAY...DANGEROUS CONDITIONS ARE EXPECTED OVER ALL WATERS
SATURDAY WITH THE POTENTIAL FOR SOLID GALES INCREASING. GALE
WARNINGS WILL BE ISSUED FOR ALL MARINE ZONES...INCLUDING THE
CHARLESTON HARBOR. EXPECT WINDS OF 30-35 KT WITH GUSTS TO 40 KT
NEARSHORE WATERS AND 35-40 KT WITH GUSTS TO 45 KT OFFSHORE WATERS.
SEAS WILL RANGE FROM 4-7 FT NEARSHORE...8-13 FT OFFSHORE. 1000 HPA
GEOSTROPHIC WINDS ARE FORECAST TO BE 50-60 KT...SO ITS ENTIRELY
POSSIBLE A FEW GUSTS TO STORM FORCE />=48 KT/ COULD OCCUR...
ESPECIALLY OVER THE WARMER OFFSHORE WATERS. ALTHOUGH NOT LIKELY
ATTM...A STORM WARNING MAY EVENTUALLY BE NEEDED FOR SOME
LEGS...ESPECIALLY SATURDAY AFTERNOON WHEN WINDS ARE FORECAST TO PEAK.

SATURDAY NIGHT THROUGH WEDNESDAY...IMPROVING CONDITIONS EXPECTED
LATER SATURDAY NIGHT INTO SUNDAY WITH WINDS DROPPING BELOW ADVISORY
LEVELS BY EARLY AFTERNOON...ALTHOUGH SEAS WILL TAKE A BIT LONGER TO
DO SO BEYOND 20 NM. NO ISSUES FROM SUNDAY NIGHT THROUGH WED ALTHOUGH
SEAS WILL BE BUILDING BACK UP LATER IN THE PERIOD GIVEN THE
PERSISTENT EAST WINDS ON THE SOUTH SIDE OF HIGH PRESSURE.

BLOWOUT TIDES...STRONG OFFSHORE WINDS ARE LIKELY TO PUSH TIDES INTO
THE -1 TO 0 FT MLLW SATURDAY INTO SUNDAY. ATTM IT DOES NOT APPEAR AS
THROUGH LEVELS WILL REACH LEVELS WHERE NAVIGATION PROBLEMS
OCCUR...BUT THIS WILL WATCHED CAREFULLY.

&&

.FIRE WEATHER...
VERY BREEZY TO WINDY CONDITIONS EXPECTED SATURDAY BEHIND A STRONG
COLD FRONT. WINDS COULD GUST NEAR 40-45 MPH...ESPECIALLY OVER
SOUTHEAST GEORGIA. THIS IS WHERE FUEL MOISTURES APPEAR TO BE LOWEST
GIVEN THE LACK OF RECENT RAINFALL. AT THIS TIME MINIMUM RELATIVE
HUMIDITIES ARE NOT EXPECTED TO REACH CRITICAL THRESHOLDS
/25 PERCENT/...BUT THIS COULD CHANGE IF THE AIR MASS IS A BIT WARMER
AND/OR DRIER THAN CURRENTLY EXPECTED. CONDITIONS COULD BE A BIT
DRIER SUNDAY ALTHOUGH WINDS WILL BE MUCH LOWER. IN ANY
EVENT...LAND MANAGERS ARE ENCOURAGED TO PAY ATTENTION TO THE LATEST
FORECASTS THIS WEEKEND. HEADLINES FOR CRITICAL WINDS AND NEAR
CRITICAL RH WILL BE ADDED TO THE FIRE WEATHER PLANNING FORECAST.

&&

.CLIMATE...
RECORD LOW MAX TEMPERATURES FOR SAT NOV 1...
KCHS 56 /1993/...
KSAV 52 /1925/...
KCXM 52 /1925/...

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...WIND ADVISORY FROM 9 AM TO 8 PM EDT SATURDAY FOR GAZ114>119-
     137>141.
SC...LAKE WIND ADVISORY FROM 6 AM EDT SATURDAY TO 11 AM EST SUNDAY
     FOR SCZ045.
MARINE...GALE WARNING FROM 6 AM EDT SATURDAY TO 5 AM EST SUNDAY FOR
     AMZ350-352-354-374.
     GALE WARNING FROM 9 AM TO 8 PM EDT SATURDAY FOR AMZ330.

&&

$$

NEAR TERM...DPB
SHORT TERM...ST
LONG TERM...RJB
AVIATION...DPB/ST
MARINE...DPB/ST
FIRE WEATHER...
CLIMATE...






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