Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 010228
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1028 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/...
WHAT A POTENT SYSTEM SO FAR...AND IT WILL ONLY GET STRONGER
OVERNIGHT AND SATURDAY. WE HAVE ACTUALLY SEEN A INDICATIONS OF
SMALL HAIL AS PER DUAL POL HYDROMETEORS AND AN EARLIER REPORT FROM
AIKEN COUNTY OF PEA-SIZED HAIL...WITH A 10 VIL! GIVEN DECENT LOW
AND MID LEVEL LAPSE RATES...SLIGHT SURFACE BASED INSTABILITY AND
ADEQUATE CAPE IN THE HAIL GROWTH ZONE...WE FORESEE ISOLATED TO
SCATTERED SHOWERS AND MAYBE A T-STORM OR TWO IN THE CHARLESTON
QUAD-COUNTY AREA THROUGH TIL 12-1 AM IN ASSOCIATION WITH A PRE-
FRONTAL TROUGH AND LARGE SCALE ASCENT IN ADVANCE OF THE CLOSED LOW
DIGGING ACROSS THE OHIO/TENN VALLEYS. IF IT/S DOING THIS
NOW...IMAGINE WHAT MAY TRANSPIRE SATURDAY AS THE COLDER AIR
ARRIVES AND STEEPER LAPSE RATES DEVELOP.

AS THE CURRENT CONVECTION PIVOTS NORTH OF THE SANTEE RIVER BY
ABOUT 05Z THERE IS A BREAK UNTIL LATE TONIGHT WHEN SOME
ADDITIONAL SHOWERS MOVE IN ALONG THE NW TIER OF SC ONCE THE DEEP
LAYERED LOW ALOFT HEADS OUR WAY. MOST AREAS THOUGH WILL NOT GET
ANY RAINFALL ROUGHLY SOUTH AND SE OF A LINE FROM HAMPTON TO
BEAUFORT...AND MUCH OF THE NIGHT AFTER 1 AM WILL BE RAINFREE.

MEANWHILE...THE ARCTIC COLD FRONT IS ENTERING OUR INTERIOR SE GA
ZONES EARLY AND WILL SWING QUICKLY OFF THE GA COASTAL ZONES AFTER
MIDNIGHT. IN SC THE FRONT IS A LITTLE SLOWER IN TRAVELING THROUGH
AS A WAVE OF LOW PRESSURE FORMS IN OR NEAR THE PEE DEE REGION.
THIS WILL DELAY THE PASSAGE OF THE COLD FRONT UNTIL AROUND 1-3 AM
OVER BEAUFORT AND COLLETON COUNTIES...AND THROUGH THE CHARLESTON
TRI-COUNTY SECTIONS THEREAFTER. COLD AIR IS QUITE IMPRESSIVE AND
AS IT STARTS TO SURGE IN IT WILL BREAK THE NOCTURNAL INVERSION AND
WITH PACKING OF THE GRADIENT IT WILL RESULT IN OCCASIONAL GUSTY
WEST/NW WINDS...AS HIGH AS 15-25 MPH ACROSS SE GA AND 10-20 MPH IN
SC.

TEMPS AT MIDNIGHT WILL BE LIKELY BE GREATER THAN WHAT TEMPS WILL
BE DURING THE DAY SATURDAY...AND BY MORNING WITH A CONTINUED
INFLUX OF COOLER CANADIAN AIR WE/LL SEE LOWS DOWN NEAR 40 FROM
HAMPTON AND ALLENDALE TO TATTNALL...LOWER AND MIDDLE 40S MOST
ELSEWHERE...EXCEPT FOR A FEW UPPER 40S OVER COASTAL CHARLESTON.
THIS WILL BE SOME 6-10 DEGREES BELOW TYPICAL NOVEMBER 1 LEVELS.

&&

.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 AIR MASS 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 /03Z SATURDAY THROUGH WEDNESDAY/...
KCHS...A FEW UPSTREAM SHRA IN ADVANCE OF A PRE-FRONTAL TROUGH WILL
MOVE THROUGH THE TERMINAL EARLY TONIGHT...OTHERWISE VFR TO
PREVAIL. THE COLD FRONT WILL SWING THROUGH OVERNIGHT AND AS COLDER
AIR STARTS TO RUSH IN AND MIXING HEIGHTS CLIMB WINDS WILL BECOME
STRONGER AND PROGRESSIVELY MORE GUSTY LATE TONIGHT AND MORE SO ON
SATURDAY. IN ADDITION...STEEP LAPSE RATES AND PLENTY OF LOW LEVEL
MOISTURE WILL CAUSE SCATTERED SHRA TO OCCUR THROUGH THE DAY
SATURDAY. UNTIL TRENDS CAN BE BETTER ASCERTAINED WE HAVE KEPT
CONDITIONS AT VCSH AND LOW-END VFR CEILINGS. HOWEVER...FLIGHT
RESTRICTIONS ARE POSSIBLE AS IS SMALL HAIL IN SOME OF THE HEAVIER
AND TALLER SHRA.

KSAV...VFR CONDITIONS EXPECTED IN ADVANCE OF THE COLD FRONT EARLY
TONIGHT...BEFORE FROPA GENERATES LOWERING CEILINGS /BUT STILL VFR
WEATHER/ AND INCREASING WESTERLY WINDS AFTER 06Z. WEST AND NW
WINDS WILL BECOME STRONGEST AND MOST GUSTY DURING THE DAY SATURDAY
WITH GOOD MIXING PROFILES AND A PACKED PRESSURE GRADIENT. THE BEST
CHANCE OF SHRA LOOKS TO STAY NORTH OF THE TERMINAL
SATURDAY...UNLESS WRAP-AROUND MOISTURE IS FURTHER SOUTH THAN NOW
ANTICIPATED. FOR NOW WE HAVE MAINTAINED LOW-END VFR CEILINGS.

EXTENDED AVIATION OUTLOOK...NO IMPACTS EXPECTED SUN-WED.

&&

.MARINE...
OVERNIGHT...MARINERS CAN ANTICIPATE A RAMPING UP OF WINDS AND
SEAS AS A STRONG ARCTIC COLD FRONT MOVES INTO AND THROUGH THE
LOCAL WATERS. COLD ADVECTION WILL BEGIN IN ERNEST IN WAKE OF THE
FRONT WHICH OCCURS STARTING AROUND 04-06Z ACROSS THE GA
WATERS...AND 06-09Z ACROSS THE SC WATERS. THAT ALONG WITH A TIGHT
PRESSURE GRADIENT IN RESPONSE TO THE PRESSURE DIFFERENCE BETWEEN
CANADIAN HIGH PRESSURE DROPPING INTO THE CENTRAL U.S. AND LOW
PRESSURE STARTING TO FORM NEAR THE SC/NC LINE WILL CAUSE A SHARP
RISE IN WINDS. WE/LL BE CLOSE TO GALES BY LATE TONIGHT ACROSS
AMZ354-374...THUS A START TIME OF 4 AM FOR THE GALE WARNING ON
THESE WATERS. CONDITIONS ON THE SC WATERS SHOULD HOLD NEAR OR JUST
BELOW ANY HEADLINE CRITERIA UNTIL CLOSER TO DAYBREAK
SATURDAY...WHEN WE HAVE GALES STARTING ON AMZ330-350-352. SEAS
WILL BE RESTRICTED SOME BY THE OFFSHORE FETCH BUT WILL STILL BUILD
FROM AROUND 2-4 FT EARLY UPWARDS TO 4-7 FT BY LATE...HIGHEST
ACROSS THE OUTER GA WATERS. IN ADVANCE OF THE COLD FRONT A FEW
T-STORMS WILL OCCUR ACROSS THE SC ATLANTIC WATERS WITH GUSTY WINDS
AND SMALL HAIL TIL ABOUT 12-1 AM.

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 4 AM EST SUNDAY FOR
     AMZ330-350-352.
     GALE WARNING FROM 4 AM EDT SATURDAY TO 5 AM EST SUNDAY FOR
     AMZ354-374.

&&

$$

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






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