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Area Forecast Discussion

877
FXUS62 KCHS 231641
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1141 AM EST SUN NOV 23 2014

.SYNOPSIS...
A WARM FRONT WILL MOVE NORTH THROUGH THE AREA TODAY. A COLD FRONT
WILL THEN SHIFT TOWARD THE COAST AND OFFSHORE BY MONDAY NIGHT. THE
FRONT WILL MEANDER OFF THE SOUTHEAST COAST INTO EARLY WEDNESDAY...
BEFORE AN OFFSHORE LOW PRESSURE PULLS THE FRONT TO THE NORTHEAST AND
ALLOWS HIGH PRESSURE TO RETURN INTO THE HOLIDAY WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
FORECAST WAS PRETTY MUCH ON TARGET SO NO MAJOR CHANGES WERE MADE.
DID TREND RAIN CHANCES DOWN ACROSS SOUTHEAST GEORGIA AS IT APPEARS
THERE WILL BE A DECENT LULL IN THE RAIN COVERAGE THIS AFTERNOON AS
THE WARM FRONT LIFTS NORTH OF THAT AREA. ALSO ADDED MENTION OF
PATCHY FOG NEAR THE SOUTHERN SC/NORTHERN GA COASTAL AREAS AS THE
WARM/HUMID AIR MASS SHIFTS OVER THE COOLER NEAR SHORE WATERS.
OTHERWISE...WE DO EXPECT SOME INSTABILITY TO DEVELOP AS THE WARM
FRONT LIFTS THROUGH BUT SEVERE WEATHER PROSPECTS LOOK VERY LOW
OVER LAND GIVEN THE LIMITED INSTABILITY...MAINLY CONFINED TO
SOUTHEAST GEORGIA. DAMAGING WIND GUSTS ARE THE MAIN HAZARD BUT AN
ISOLATED TORNADO CANNOT BE RULED OUT AS SHEAR IS ENHANCED ALONG
THE FRONT.

HIGHS SHOULD REACH THE MID 70S SOUTH AND EAST BUT REMAIN CLOSER TO
70 NORTH AND WEST AS THOSE AREAS WILL BE IN THE LINGERING WEDGE
THE LONGEST.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
TONIGHT...MODELS SHOW THE WARM FRONT DISPLACED JUST TO THE NORTH
ACROSS THE SOUTHERN MIDLANDS AND PEE DEE AS A POWERFUL...
NEGATIVELY TILTED SHORTWAVE PIVOTS OVER THE SOUTHEAST STATES.
ALTHOUGH ONLY SCATTERED CONVECTIVE ACTIVITY WILL LIKELY BE IN
PROGRESS AT SUNSET...MESOSCALE MODELS HINT THAT AT A SOMEWHAT
ORGANIZED LINE OF STRONG TO SEVERE TSTMS...POSSIBLY IN THE FORM OF
A QLCS/SQUALL LINE...COULD BE APPROACHING THE FAR WESTERN ZONES.
THIS ACTIVITY APPEARS TO ORGANIZE ALONG THE LEADING EDGE OF A
CORRIDOR OF INTENSE UPPER FORCING ASSOCIATED WITH THE SHORTWAVE
ITSELF AS IT ENCOUNTERS AN INCREASINGLY UNSTABLE ATMOSPHERE ACROSS
SOUTH GEORGIA AND SOUTHEAST SOUTH CAROLINA IN THE WAKE OF THE WARM
FRONT. NAM12 INSTABILITY PROGS SHOW SBCAPE VALUES REACHING AS HIGH
AS 800-1200 J/KG WITHIN THE CORE OF THE WARM SECTOR WITH
IMPRESSIVE KINEMATIC PROFILES FEATURING 0-6 KM BULK SHEAR VALUES
OF 50-55 KT ALIGNED WITH A CORRIDOR OF SHERBS3 VALUES OF 1-1.25
UNITS. ALTHOUGH INSTABILITY IS ONLY WEAK TO MODEST AT
BEST...IMPRESSIVE UPPER DYNAMICS COULD BE ENOUGH TO COVER COME
THIS TO SUPPORT A CONTINUATION OR EVEN A STRENGTHENING OF THE
CONVECTIVE LINE AS IT CROSSES THE AREA THIS EVENING INTO THE EARLY
MORNING HOURS MONDAY. THE PRIMARY HAZARD WITH THIS LINE LOOKS TO
BE DAMAGING WINDS...ALTHOUGH THERE WILL BE A RISK FOR AN ISOLATED
TORNADO...ESPECIALLY ACROSS THE NORTHWEST TIER CLOSER TO THE WARM
FRONT. THE CONFIDENCE IN THIS SCENARIO IS ONLY MODERATE AT BEST AT
THIS POINT IN TIME AND FURTHER REFINEMENT WILL BE NEED THROUGHOUT
THE DAY.

POPS OF OF 30-50 PERCENT WILL BE DEPICTED TONIGHT WITH GRIDDED
POPS REACHING AS HIGH AS 60-70 PERCENT ALIGNED WITH THE EXPECTED
PLACEMENT OF THE CONVECTIVE LINE. IT WILL BE BE A WARM/HUMID NIGHT
WITH LOWS ONLY DROPPING INTO THE MID-UPPER 60S FOR MOST AREAS.
DESPITE IMPRESSIVE WIND FIELDS...GUIDANCE SUGGESTS WIDESPREAD
STRATUS AND EVENTUALLY FOG WILL FILL IN BEHIND THE SQUALL LINE.
IT IS UNCLEAR EXACTLY HOW THIS PART OF THE FORECAST WILL
UNFOLD GIVEN THE AMOUNT OF WIND THAT WILL BE IN PLACE...BUT ITS
CERTAINLY POSSIBLE THE FOG COULD BECOME DENSE AT TIMES. WILL SHOW
AREAS OF FOG IN THE GRIDS...ROUGHLY TIMED WITH THE PASSAGE OF THE
SQUALL LINE.

MONDAY...THE SOUTHEAST COAST WILL BECOME LOCATED BETWEEN RIDGING
OVER THE BAHAMAS AND THE AXIS OF AN UPPER TROUGH ACROSS THE CENTRAL
UNITED STATES. THE PROGRESSION OF A COLD FRONT WILL BE SLOW AND
STEADY MONDAY AND MONDAY NIGHT DUE TO ITS NEARLY PARALLEL
ORIENTATION TO THE UPPER FLOW. CONSIDERING MUCH OF THE LARGE SCALE
DYNAMICS AND FORCING WILL BE LIFTING OUT OF THE REGION...CONVECTION
APPEARS LIMITED TO A NARROW BAND OF DEEP MOISTURE AHEAD AND ALONG
THE APPROACHING BOUNDARY. WILL THUS KEEP RAIN CHANCES CAPPED IN THE
30 PERCENT RANGE...HIGHEST DURING THE AFTERNOON HOURS AND CLOSER TO
THE COAST...WHERE LOW LEVEL MOISTURE COULD POOL AHEAD OF THE FRONT.
TEMPERATURES WILL BECOME QUITE WARM MONDAY AFTERNOON CONSIDERING A
WARMER START TO THE DAY AND PERSISTENT SOLID SOUTH/SOUTHWEST FLOW.
EXPECT HIGHS TO REACH THE MID TO UPPER 70S...AND GIVEN THE
UNSEASONABLY WARM CONDITIONS...HAVE INCLUDED A SLIGHT CHANCE FOR
THUNDER. SHOWER POTENTIAL WILL DECREASE FROM WEST TO EAST DURING THE
EVENING AND NIGHTTIME HOURS...AS THE FRONT MOVES OFFSHORE AND DRIER
AIR APPROACHES IN ITS WAKE. LOW TEMPERATURES WILL BE NEARLY 10 TO 15
DEGREES COOLER THAN THE PREVIOUS NIGHT...FALLING INTO UPPER 40S FAR
INLAND TO THE LOW/MID 50S CLOSER TO THE COAST.

TUESDAY...THE COLD FRONT WILL STALL JUST OFF THE SOUTHEAST
COAST...AS HIGH PRESSURE STRUGGLES TO PUSH EASTWARD. STRONG
SOUTHERN STREAM SHORTWAVE ENERGY WILL SWEEP THROUGH THE SOUTHERN
PLAINS STATES AND ACROSS THE GULF COAST THROUGH TUESDAY
NIGHT...SUPPORTING THE DEVELOPMENT OF WAVES OF LOW PRESSURE ALONG
THE SOUTHERN END OF THE STALLED BOUNDARY. RAIN CHANCES WILL
CONTINUE DUE TO THE LACK OF A CLEAN FRONTAL PROGRESSION...AND
COVERAGE WILL BE HIGHLY DEPENDENT ON THE LOCATION OF THE
MEANDERING FRONT AND ASSOCIATED CONVERGENCE ZONE. BOTH THE 00Z
ECMWF AND 00Z GFS SUGGEST THAT RAIN COVERAGE WILL INCREASE TUESDAY
NIGHT...WHEN THE CORE OF THE SHORTWAVE ENERGY SWINGS TOWARD THE
AREA AND THE SURFACE WAVE LIFTS FROM THE GULF OF MEXICO TOWARD THE
SOUTHEAST COAST. HAVE INDICATED POPS IN THE CHANCE RANGE ALL AREAS
DURING THE DAYTIME HOURS...INCREASING TO LIKELY RAIN FOR THE
COASTLINE AND CHARLESTON TRI COUNTY AREA OVERNIGHT. TEMPERATURES
WILL BE NOTABLY COOLER ON THE BACK SIDE OF THE COLD FRONT AND LOW
PRESSURE SYSTEM...WITH HIGHS ONLY IN THE LOW 60S AND NIGHTTIME
MINIMUMS IN THE LOW 40S.

WEDNESDAY...LOW PRESSURE JUST OFFSHORE WILL STEADILY LIFT NORTH
UP THE COAST...AHEAD OF THE SHORTWAVE ENERGY AND UPPER TROUGH
AXIS MOVING INTO THE SOUTHEAST STATES BY MIDDAY. THE DAY WILL
BEGIN WITH A RATHER NOTABLE GRADIENT IN RAIN COVERAGE...WITH THE
CHARLESTON TRI COUNTY AREA SEEING NUMEROUS SHOWERS...AND THE
GEORGIA ZONES FARTHER SOUTH TOWARD THE ALTAMAHA RIVER SEEING
SCATTERED COVERAGE AT BEST. DRIER AIR WILL QUICKLY WRAP INTO THE
REGION FROM THE SOUTHWEST BEHIND THE DEPARTING SYSTEM...AND EXPECT
RAIN CHANCES TO FALL BELOW 15 PERCENT ACROSS THE FORECAST AREA BY
THE EVENING HOURS. THE REGION WILL BE LOCATED ON THE COLD SIDE OF
THE SYSTEM...AND COLD ADVECTION COMBINED WITH FALLING HEIGHTS
ALOFT WILL SUPPORT AN UNSEASONABLY COLD DAY...WITH HIGH
TEMPERATURES SUPPRESSED IN THE LOW TO MID 50S.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
DRIER HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE
WEST/SOUTHWEST LATE WEDNESDAY INTO THURSDAY. A STRONGER AREA OF
HIGH PRESSURE WILL THEN BUILD IN FROM THE NORTH LATE THURSDAY...
DESCENDING INTO THE SOUTHEAST STATES BY FRIDAY...BEFORE GRADUALLY
SHIFTING TOWARD THE COASTLINE AND NEARBY ATLANTIC WATERS OVER THE
WEEKEND. UNSEASONABLY COOL CONDITIONS WILL PREVAIL THROUGH THE
PERIOD. HIGH TEMPERATURES WILL ONLY REACH THE UPPER 50S TO LOWER
60S THURSDAY AND FRIDAY...WITH LOW TEMPERATURES FALLING INTO THE
30S. A GRADUAL WARMING TREND WILL OCCUR OVER THE WEEKEND AS THE
CENTER OF THE SURFACE HIGH SHIFTS TOWARD THE COASTLINE...WITH
HIGHS REACHING THE 60S BY SUNDAY AFTERNOON AND LOWS MODERATING
INTO THE UPPER 30S TO LOW 40S BY SUNDAY NIGHT. CONDITIONS APPEAR
DRY THROUGH THE EXTENDED PERIOD...AND WILL KEEP RAIN OUT OF THE
FORECAST.

&&

.AVIATION /16Z SUNDAY THROUGH THURSDAY/...
PREVAILING IFR LIKELY THIS AFTERNOON AS A WARM FRONT MOVES
NORTHWARD THROUGH THE AREA. THE STEADIEST RAIN AND GENERALLY WORSE
CONDS WILL BE AT KCHS WHICH WILL BE IN THE COOL SECTOR LONGEST. WINDS
WILL BECOME GUSTY AT BOTH TERMINALS BY LATE MORNING/EARLY
AFTERNOON WITH THE PASSAGE OF THE WARM FRONT WITH GUSTS TO 25 KT
LIKELY. LOW-LEVEL WIND SHEAR WILL REMAIN A CONCERN UNTIL THE FRONT
PASSES AND SURFACE WINDS PICK UP. THERE WILL BE ANOTHER ROUND OF
SHOWER/TSTMS POSSIBLE THIS EVENING...POSSIBLY IN THE FORM OF A
SQUALL LINE. FOR NOW LIMITED CONDITIONS TO MVFR WITH A MENTION FOR
TSRA. LOW STRATUS AND FOG ARE POSSIBLE TONIGHT ONCE THE SQUALL
LINE MOVES THROUGH. THERE REMAINS SOME QUESTIONS ON EXACTLY HOW
WIDESPREAD/DENSE THE STRATUS/FOG WILL BECOME...SO LIMITED
CONDITIONS TO JUST ABOVE AIRFIELD ALTERNATE MINIMUMS AT BOTH
TERMINALS FOR NOW.

EXTENDED AVIATION OUTLOOK...FLIGHT RESTRICTIONS WILL PREVAIL AT
BOTH TERMINALS INTO EARLY MONDAY AS A WARM FRONT LIFTS NORTH OF
THE AREA. THIS WILL RESULT IN MVFR OR LOWER CONDITIONS IN MODERATE
TO OCCASIONAL RAIN...ISOLATED TSTMS...AND GRADUALLY LOWERING
CEILINGS WITH POSSIBLE FOG/MIST. CONDITIONS WILL ALSO BE BREEZY
SUNDAY INTO MONDAY. PERIODIC FLIGHT RESTRICTIONS ARE STILL
POSSIBLE INTO EARLY WEDNESDAY...UNTIL A COLD FRONT PULLS FARTHER
OFFSHORE DURING MID WEEK.

&&

.MARINE...
TODAY...HAZARDOUS MARINE CONDITIONS WILL OCCUR OVER THE WATERS
TODAY A STRONG LOW-LEVEL JET DEVELOPS OVERHEAD AND A COASTAL FRONT
SHIFTS INLAND. MIXING WILL BE SOMEWHAT LIMITED IN THE WARM AIR
ADVECTION REGIME GIVEN THE COLD SHELF WATERS IN PLACE. THIS SHOULD
LIMIT WINDS TO 20-25 KT WITH GUSTS TO 30 KT. THE ONLY EXCEPTION
WILL BE OVER THE EASTERN PORTIONS OF THE GEORGIA OFFSHORE WATERS
WERE WATER TEMPERATURES ARE IN THE LOWER-MID 70S PER LATEST MODIS
SST IMAGERY. THIS WILL SUPPORT MUCH DEEPER MIXING PROFILES WHICH A
RISK FOR FREQUENT GUSTS TO 35-40 KT GALES. PER COLLABORATION WITH
THE OCEAN PREDICTION CENTER...A GALE WARNING WILL BE POSTED FOR
THE GEORGIA OFFSHORE WATERS THROUGH THIS EVENING. SMALL CRAFT
ADVISORIES WILL REMAIN FOR THE NEARSHORE WATERS AND WILL BE
EXPANDED TO INCLUDE THE CHARLESTON HARBOR. SEAS WILL BUILD TO 5-8
FT NEARSHORE WATERS...EXCEPT 6-10 FT CHARLESTON COUNTY WATERS AND
7-12 FT OVER THE GEORGIA OFFSHORE WATERS. WE ADDED PATCHY FOG TO
THE FORECAST AS WELL AS THE WARM/HUMID AIR MOVES IN OVER THE
COOLER NEAR SHORE WATERS ALONG THE SOUTHERN SC/NORTHERN GA COAST.

TONIGHT...HAZARDOUS MARINE CONDITIONS WILL PERSIST OVER THE WATERS
TONIGHT WITH THE AREA FIRMLY EMBEDDED WITHIN THE WARM SECTOR.
WINDS WILL DIMINISH SOME AFTER MIDNIGHT AS THE AXIS OF THE LOW-
LEVEL JET BEGINS TO MOVE OFF TO THE EAST/NORTHEAST...BUT BOTH
WINDS AND SEAS WILL LINGER WELL ABOVE SMALL CRAFT ADVISORY
THRESHOLDS. SEAS WILL DIMINISH TO 4-8 FT NEARSHORE WATERS...HIGHEST
OVER THE CHARLESTON COUNTY WATERS...WITH 7-9 FT OVER THE GEORGIA
OFFSHORE LEG.

MONDAY THROUGH WEDNESDAY...A SLOW MOVING COLD FRONT OVER THE
SOUTHEAST STATES ON MONDAY WILL MOVE INTO AND THROUGH THE WATERS
BY TUESDAY. LOW PRESSURE WILL THEN FORM ALONG THE LINGERING FRONT
JUST OUTSIDE OF THE MARINE AREA AND EVENTUALLY PULL THE FRONT AWAY
FROM THE REGION BY WEDNESDAY. ONGOING SMALL CRAFT ADVISORIES ARE
EXPECTED TO END MONDAY. HOWEVER...THE LOCATION AND MOVEMENT OF
THE DEVELOPING LOW PRESSURE SYSTEM COULD IMPACT MARINE CONDITIONS
THROUGH MID WEEK AND MAY SUPPORT ADDITIONAL ADVISORIES AT A LATER
TIME.

HIGH SURF...A HIGH SURF ADVISORY WILL BE ISSUED FOR THE SOUTHERN
SOUTH CAROLINA COAST FOR THIS AFTERNOON INTO EARLY MONDAY MORNING.
SEAS ARE FORECAST TO BUILD TO NEAR 12 FT AT BUOY 41004 WITH THE
HIGHEST SEAS NEAR THE COAST OCCURRING OFF THE CHARLESTON COUNTY
COAST. THIS COULD PRODUCE BREAKING WAVE HEIGHTS AROUND 5
FT...ESPECIALLY ALONG EAST AND SOUTHEAST FACING BEACHES OF
CHARLESTON COUNTY.

&&

.HYDROLOGY...
MOST AREAS HAVE PICKED UP ABOUT 0.5-1.5 INCHES OF RAIN WITH SOME
LOCALLY HIGHER AMOUNTS SO FAR. AN ADDITIONAL INCH OR SO IS
POSSIBLE THROUGH TONIGHT. THE RISK FOR FLASH FLOODING WILL BE
MAINLY CONFINED TO THE URBAN COASTAL AREAS DUE TO THE ADDED
INFLUENCE FROM THE TIDES.

&&

.CLIMATE...
RECORD PRECIPITATION FOR 23 NOVEMBER...
KCHS...0.70 INCHES SET IN 1961.
KCXM...1.17 INCHES SET IN 1942.
KSAV...2.11 INCHES SET IN 1948.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...HIGH SURF ADVISORY UNTIL 5 AM EST MONDAY FOR SCZ048>051.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 PM EST MONDAY FOR AMZ352-354.
     SMALL CRAFT ADVISORY UNTIL 1 AM EST TUESDAY FOR AMZ350.
     GALE WARNING UNTIL 11 PM EST THIS EVENING FOR AMZ374.
     SMALL CRAFT ADVISORY UNTIL 11 PM EST THIS EVENING FOR AMZ330.

&&

$$

NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
HYDROLOGY...
CLIMATE...






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