Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 011155
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
755 AM EDT SAT NOV 1 2014

.SYNOPSIS...
A STRONG COLD FRONT WILL MOVE OFFSHORE EARLY THIS MORNING...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 PM THIS EVENING/...
A POWERFUL AND HIGHLY UNUSUAL STORM SYSTEM FOR EARLY NOVEMBER
WILL IMPACT THE REGION INTO TONIGHT. AS OF EARLY THIS
MORNING...WATER VAPOR IMAGERY DEPICTS A POTENT UPPER LEVEL LOW
DROPPING SOUTHEAST ALONG THE UPPER GEORGIA/SOUTH CAROLINA BORDER.
MEANWHILE AT THE SURFACE...A WAVE OF LOW PRESSURE HAS DEVELOPED
OVER THE PEE DEE WHILE AN ARCTIC COLD FRONT PUSHES OFFSHORE.

TODAY...THE CLOSED UPPER LOW WILL CONTINUE TO STRENGTHEN AS IT
TRACKS ALONG THE UPPER GEORGIA/SOUTH CAROLINA BORDER THIS MORNING AND
OFF THE CENTRAL SOUTH CAROLINA COAST THIS AFTERNOON. AS THIS
OCCURS...THE ARCTIC COLD FRONT WILL CONTINUE TO RAPIDLY SHIFT
OFFSHORE...WITH INCREDIBLY STRONG COLD AIR ADVECTION
OVERSPREADING THE AREA IN ITS WAKE. THE AIR MASS ALOFT WILL BE
EXTREMELY COLD...WITH 500 MB TEMPERATURES AS LOW AS -22 TO -28C
AND 850 MB TEMPERATURES AS LOW AS -3 TO -6C. IN FACT...THESE 850
MB TEMPERATURES WILL BE SOME OF THE COLDEST EVER FOR EARLY
NOVEMBER. NEEDLESS TO SAY...THIS SYNOPTIC PATTERN WILL HAVE
SIGNIFICANT IMPACTS ON TEMPERATURES...PRECIPITATION COVERAGE AND
TYPE...AND WINDS...ALL OF WHICH WILL BE DETAILED BELOW.

TEMPERATURES: AS THE COLD POOL ALOFT ASSOCIATED WITH THE UPPER
LOW OVERSPREADS THE AREA...CONSIDERABLE CLOUD COVER WILL
DEVELOP...ESPECIALLY OVER MUCH OF SOUTHEAST SOUTH CAROLINA. THIS
CLOUD COVER COMBINED WITH ANY DIABATIC COOLING THAT TAKES PLACE
DUE TO SHOWERS WILL RESULT IN VERY COOL TEMPERATURES...ESPECIALLY
OVER SOUTHEAST SOUTH CAROLINA AND SPECIFICALLY THE CHARLESTON TRI-
COUNTY AREA. THERE IS GOOD MODEL AGREEMENT...ESPECIALLY WITH THE NAM
AND ECMWF MOS-BASED GUIDANCE AND THE RAW GFS...NAM AN SREF OUTPUT
INDICATING HIGHS ONLY IN THE UPPER 40S ACROSS THE CHARLESTON TRI-
COUNTY AREA...AROUND 50 OR IN THE LOWER 50S NEAR THE SAVANNAH
RIVER VALLEY...AND IN THE MID 50S ALONG AND SOUTH OF THE I-16
CORRIDOR. THESE FORECAST VALUES WOULD RESULT IN RECORD LOW MAXIMUM
TEMPERATURES AND KCHS AND KCXM...AND WOULD COME CLOSE TO THE
RECORD AT KSAV. SEE BELOW FOR MORE DETAILED CLIMATE INFORMATION.

PRECIPITATION: INSTABILITY SHOWERS WILL INCREASE IN COVERAGE LATE
THIS MORNING INTO THIS AFTERNOON AS THE CORE OF THE COLD POOL
ALOFT SHIFTS OVER THE AREA AND STRONG DYNAMICAL FORCING TAKES
PLACE. THE BEST POTENTIAL FOR SHOWERS WILL BE ACROSS THE PEE DEE
AND NORTHERN MIDLANDS...BUT PRECIPITATION CHANCES WILL STILL RANGE
FROM 50-60 PERCENT IN THE CHARLESTON TRI-COUNTY AREA...TO 30-50
PERCENT ACROSS THE REMAINDER OF SOUTHERN SOUTH CAROLINA...TO 20-30
PERCENT IN SOUTHEAST GEORGIA NORTH OF THE I-16 CORRIDOR. A FEW
THUNDERSTORMS COULD ALSO DEVELOP...BUT COVERAGE WOULD BE ISOLATED
AT BEST. HAVE ADDED MENTION OF GRAUPEL/SLEET TO THE FORECAST FOR
MUCH OF SOUTHEAST SOUTH CAROLINA WITH MODEL SOUNDINGS SHOWING
MOISTENING OF THE -10 TO -12C LAYER /WHICH IS THE PRIME DENDRITIC
SNOW GROWTH REGION/...STRONG MID-LEVEL LAPSE RATES AND LOWERING OF
THE FREEZING LEVEL POSSIBLY TO BELOW 2500 FT.

WINDS: THE IMPRESSIVE COLD AIR ADVECTION DEVELOPING TODAY WILL
ALLOW FOR SIGNIFICANT DEEPENING OF THE MIXED LAYER...WHICH WILL
TAP INTO VERY STRONG WINDS ALOFT ON THE ORDER OF 45-55 KT WITHIN
5000 FT OF THE SURFACE. THE STRONGEST LOW LEVEL WIND FIELDS WILL
OCCUR ALONG THE SOUTHERN PERIPHERY OF THE UPPER LOW...WHICH MEANS
MOST OF SOUTHEAST GEORGIA AND PORTIONS OF THE SOUTH CAROLINA COAST
WILL EXPERIENCE WINDS OF 20 TO 30 MPH WITH GUSTS TO 40 MPH AT
TIMES THROUGH THIS AFTERNOON. AS A RESULT...THE WIND ADVISORY HAS
BEEN EXPANDED TO INCLUDE ALL OF SOUTHEAST GEORGIA...AND COASTAL
SOUTHEAST SOUTH CAROLINA THROUGH 8 PM THIS EVENING. A LAKE WIND
ADVISORY IS ALSO IN EFFECT FOR LAKE MOULTRIE WHERE THE WARM LAKE
WATER TEMPERATURES AND COLD AIR ADVECTION ALOFT WILL RESULT IN
DANGEROUS CONDITIONS FOR MARINERS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
SUNDAY...IMPROVING CONDITIONS EXPECTED AS THE LOW PULLS FARTHER AWAY
AND HIGH PRESSURE BUILDS IN. THE LINGERING PRESSURE GRADIENT WILL
MAKE FOR SOME BREEZY CONDITIONS IN THE MORNING...ESPECIALLY ACROSS
SOUTH CAROLINA. TEMPS WILL STILL BE WELL BELOW NORMAL...MAINLY MID
50S NORTH/UPPER 50S CENTRAL AND SOUTH. THE RECORD LOW MAX TEMP FOR
CHARLESTON OF 59 DEGREES WILL LIKELY BE BROKEN.

SUNDAY NIGHT...THE COLDEST NIGHT FOR MOST INLAND AREAS AS HIGH
PRESSURE MOVES OVERTOP THE AREA. EXPECT PRETTY GOOD RADIATIONAL COOLING
CONDITIONS...ESPECIALLY AWAY FROM THE COAST WHERE WINDS WILL HOLD UP
A BIT MORE. TEMPS SHOULD DIP INTO THE MID 30S MOST LOCALES AWAY FROM
THE COAST WITH SOME LOWER 30S POSSIBLE WELL INLAND IN THE NORMALLY
COLDER RURAL SPOTS LIKE JAMESTOWN...ALLENDALE...SYLVANIA AND MILLEN.
CONDITIONS WILL ALSO FAVOR FROST...MAINLY WEST OF HWY 17 IN SC AND
I-95 IN GA. THUS...FROST ADVISORIES AND FREEZE WATCHES/WARNINGS WILL
EVENTUALLY BE NEEDED FOR PART OF THE AREA.

MONDAY/TUESDAY...HIGH PRESSURE WILL REMAIN OVER THE AREA MONDAY AND
THEN SLIDE EAST AND OFFSHORE TUESDAY BUT STILL REMAIN THE DOMINANT
WEATHER FEATURE WITH RAIN-FREE WEATHER AND TEMPS SLOWLY MODERATING
THROUGH THE PERIOD...LIKELY GETTING BACK ABOVE NORMAL /LOWER 70S/ BY
TUESDAY.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
HIGH PRESSURE WILL MOVE OFFSHORE AND PERSIST THROUGH MID WEEK BEFORE
A COLD FRONT APPROACHES WED NIGHT INTO THU AND LIKELY PUSHES THROUGH
THU NIGHT. MOISTURE WILL BE LIMITED SO NOT MUCH IN THE WAY OF RAIN
IS EXPECTED. COOLER HIGH PRESSURE SHOULD THEN RETURN FOR LATE WEEK.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
KCHS...THE COLD FRONT HAS PUSHED THROUGH AND COLDER AIR HAS
STARTED TO PLUNGE IN...ALLOWING DEEPER MIXING TO OCCUR. W/NW
WINDS WILL BECOME STRONGER AND PROGRESSIVELY MORE GUSTY THROUGH
THE MORNING...WITH GUSTS PEAKING AROUND 30 KT IN THE AFTERNOON. IN
ADDITION...STEEP LAPSE RATES AND PLENTY OF LOW LEVEL MOISTURE WILL
CAUSE SCATTERED TO NUMEROUS SHRA TO OCCUR THROUGH THE DAY...AND
HAVE PREVAILING SHRA IN THE FORECAST FROM 16-22Z. SOME
GRAUPEL/SMALL HAIL COULD OCCUR AS WELL BUT CONFIDENCE NOT HIGH
ENOUGH TO HAVE MENTION IN THE TAF/S. AS FOR FLIGHT
RESTRICTIONS...MVFR CEILINGS SHOULD PREVAIL THROUGH ABOUT 22Z
BEFORE LIFTING TO VFR FOR THE REMAINDER OF THE FORECAST PERIOD.

KSAV...THE COLD FRONT HAS PUSHED THROUGH AND COLDER AIR HAS
STARTED TO PLUNGE IN...ALLOWING DEEPER MIXING TO OCCUR. W/NW
WINDS WILL BECOME STRONGER AND PROGRESSIVELY MORE GUSTY THROUGH
THE MORNING...WITH GUSTS PEAKING AROUND 37 KT IN THE AFTERNOON. THE
BEST CHANCE OF SHRA LOOKS TO STAY NORTH OF THE TERMINAL...UNLESS
WRAP-AROUND MOISTURE IS FURTHER SOUTH THAN NOW ANTICIPATED. VFR
CONDITIONS ARE FORECAST TO PREVAIL THROUGH 12Z SUNDAY.

EXTENDED AVIATION OUTLOOK...SOME GUSTS NEAR 20 KT SUN MORNING BUT
THEN NO IMPACTS EXPECTED THROUGH WED. LOW CHANCE FOR MVFR
CIGS/SHOWERS WITH A COLD FRONT THU.

&&

.MARINE...
TODAY AND TONIGHT...DANGEROUS CONDITIONS ARE EXPECTED OVER ALL WATERS
WITH GALE FORCE WINDS DEVELOPING THIS MORNING AND CONTINUING INTO
THIS EVENING BEFORE GRADUALLY DIMINISHING OVERNIGHT. GALE WARNINGS
ARE IN EFFECT FOR ALL MARINE ZONES...INCLUDING THE CHARLESTON
HARBOR. EXPECT WINDS OF 25-35 KT WITH GUSTS TO 40 KT NEAR SHORE
WATERS AND 30-40 KT WITH GUSTS TO 45 KT OFFSHORE WATERS. SEAS WILL
RANGE FROM 4-7 FT NEAR SHORE...AND 8-11 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...
MAINLY OVER THE WARMER OFFSHORE WATERS.

SUNDAY THROUGH THURSDAY...IMPROVING CONDITIONS EXPECTED SUN AS HIGH
PRESSURE BUILDS IN BEHIND DEPARTING LOW PRESSURE. WINDS/SEAS SHOULD DROP
BELOW ADVISORY LEVELS IN THE MORNING WITHIN 20 NM AND IN THE
AFTERNOON BEYOND 20 NM. NO BIG ISSUES FROM SUN NIGHT THROUGH THU.

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

&&

.FIRE WEATHER...
VERY BREEZY TO WINDY CONDITIONS EXPECTED TODAY BEHIND A STRONG COLD
FRONT. WINDS COULD GUST NEAR 40-45 MPH...ESPECIALLY OVER SOUTHEAST
GEORGIA AND COASTAL SOUTHEAST SOUTH CAROLINA. 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 DEGREES SET IN 1993
KSAV...52 DEGREES SET IN 1925
KCXM...52 DEGREES SET IN 1925

RECORD LOW MAX TEMPERATURES FOR SUN NOV 2...
KCHS...59 DEGREES SET IN 1993
KCXM...55 DEGREES SET IN 1895
KSAV...56 DEGREES SET IN 1925

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...WIND ADVISORY UNTIL 8 PM EDT THIS EVENING FOR GAZ087-088-
     099>101-114>119-137>141.
SC...WIND ADVISORY UNTIL 8 PM EDT THIS EVENING FOR SCZ047>051.
     LAKE WIND ADVISORY UNTIL 11 AM EST SUNDAY FOR SCZ045.
MARINE...GALE WARNING UNTIL 5 AM EST SUNDAY FOR AMZ330-350-352-354-374.

&&

$$

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






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