HAMweather.com Area Forecast Discussion for County Warning Area CHS

Thu, 16 Feb 2012 13:09:10 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
715 AM EST THU FEB 16 2012

.SYNOPSIS...
A WARM FRONT WILL LIFT NORTH OF THE AREA BY THIS AFTERNOON AS A
COLD FRONT APPROACHES FROM THE WEST. THE COLD FRONT WILL MOVE
OFFSHORE TONIGHT AND LINGER TO THE SOUTH THROUGH FRIDAY AS HIGH
PRESSURE BUILDS IN FROM THE NORTH. A LOW PRESSURE SYSTEM WILL THEN
DEVELOP ALONG THE GULF COAST ON SATURDAY...AND MOVE NORTHEASTWARD
THROUGH THE REGION SUNDAY. HIGH PRESSURE WILL RETURN TO THE AREA
EARLY NEXT WEEK.

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
NEARING-DAWN...CLOUDY SKIES AND SOME PATCHY FOG ACROSS OUR
FORECAST AREA. SHOWERS HAVE ALREADY MOVED INTO THE CSRA AND PARTS
OF OUR INLAND GEORGIA ZONES. LIGHTER RAINS AND DEVELOPING SHOWERS
OVER SOUTH CAROLINA WILL OVERSPREAD THE REGION TO THE W OF I-95
DURING THE NEXT COUPLE HOURS.

THIS MORNING...THE WINDOW FOR SIGNIFICANT AREAS OF FOG APPEARS 
TO BE SHRINKING AS LOW LEVEL WIND FIELDS INCREASING IN SE GEORGIA
AND A WEAK COASTAL TROUGH KEEPING THE WARM FRONT ANCHORED TO THE
S. RAIN IS INCREASING FROM THE WSW PRETTY QUICK THIS MORNING AND
IT LOOKS LIKE PRECIP TIMING ONSET IS BEFORE MIDDAY MOST AREAS.

A JUNKY WARM SECTOR DEVELOPING FOR OUR REGION TODAY AS CLOUDS AND
PRECIP ADVANCE INTO OUR REGION DOMINATED BY LAYERED CLOUDS AND 
TRICKY LOW LEVEL STABILITY PROFILES TYPICAL FOR WARM AIR ADVECTION
REGIMES THIS TIME OF YEAR. MODELS HAVE A COMMON THEME FOR INDICATING
THAT THE BEST FORCING AND LIFT WILL SPREAD FROM THE MIDLANDS TO
THE E HALF OF THE CAROLINAS TODAY AND THIS IS WHERE WE HAVE
HIGHEST POPS NEARING CATEGORICAL RANGE. MODEL MIXED LAYER
INSTABILITY IS FAIRLY MARGINAL FOR A FEW LIGHTNING STRIKES BUT
OVERALL CHANCES FOR TSTMS APPEAR PRETTY LOW.

WE MAINTAINED SIMILAR MILD HIGH TEMPS NEAR 70 SE SOUTH CAROLINA
AND LOW-MID 70S SE GEORGIA. AREAS ALONG AND W OF THE I-95 CORRIDOR
COULD SOAR INTO THE UPPER 70S IF ANY SUBSTANTIAL INSOLATION IS
REALIZED.

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
WE SPED PRECIP DIMINISHING TRENDS A BIT QUICKER FROM OUR EARLIER 
PACKAGE AND DIMINISHED POPS IN THE EVENING AS A COLD FRONT PROGRESSES
AT A GOOD CLIP THROUGH THE FORECAST AREA. COASTAL SE GEORGIA COULD
SEE SPORADIC SHOWERS OVERNIGHT AS THE BELT OF HIGHER 1000-500MB RH
SAGS S INTO FAR S GEORGIA LATE. EVENING CLEARING AND A FRONTAL
ZONE WITH LIGHTER WINDS ARE CONCERNS THAT WE MAY SEE A BOUT OF FOG
AFTER SUNSET...ESPECIALLY IF TENTH TO QUARTER INCH RAINS DO INDEED
FALL IN EASTERN SOUTH CAROLINA.

FRIDAY...THE DESCENDING FRONT WILL SINK SOUTH OF THE FORECAST AREA
ON FRIDAY...STALLING NEAR THE GEORGIA/FLORIDA BORDER BY MIDDAY.
SURFACE HIGH PRESSURE WILL BRIEFLY BUILD FROM THE NORTH...WHILE
STEADILY TRACKING TOWARD THE COASTLINE. SHOWER ACTIVITY WILL SHIFT
SOUTHWARD THROUGH THE MORNING HOURS AND BECOME CONFINED TO AREAS
MAINLY SOUTH OF INTERSTATE 16 IN SOUTHEAST GEORGIA BY THE
AFTERNOON. LACKING COLD ADVECTION BEHIND THE FRONT...HIGH
TEMPERATURES WILL BE JUST A DEGREE OR TWO COOLER THAN
THURSDAY...REACHING THE UPPER 60S TO LOWER 70S.

FRIDAY NIGHT...WAVES OF UPPER LEVEL ENERGY WILL SLIP EASTWARD
ACROSS THE GULF COAST STATES AND ALLOW THE BOUNDARY TO WAVER
NORTHWARD AS A WARM FRONT AFTER MIDNIGHT. HAVE INDICATED RAIN
CHANCES TRENDING UPWARD LATE FRIDAY NIGHT/EARLY SATURDAY MORNING
AS A RESULT...WITH INCREASING CLOUDS KEEPING LOW TEMPERATURES MILD
IN THE UPPER 40S INLAND TO THE MID 50S SOUTHEAST GEORGIA. 

SATURDAY....THERE IS STILL QUITE A BIT OF UNCERTAINTY WITH FORECAST
DETAILS REGARDING THE STRENGTH AND TRACK OF A GULF COAST LOW SYSTEM
OVER THE WEEKEND. LATEST MODEL SOLUTIONS ALL DEPICT DIFFERENT
SPEEDS WITH WHICH THE SURFACE LOW WILL LIFT NORTHEAST FROM THE
GULF COAST STATES INTO THE CAROLINAS AND MID ATLANTIC REGION
SATURDAY NIGHT. THESE DIFFERENCES GREATLY AFFECT SENSIBLE WEATHER
IMPACTS SUCH AS TIMING AND DURATION OF RAINFALL. THERE ARE SOME
GENERAL SIMILARITIES BETWEEN SOLUTIONS...SUCH AS THE SOUTHEAST
STATES REMAINING WITHIN THE WARM SECTOR FOR MUCH OF SATURDAY.
ADDITIONALLY...ALL MODELS ARE INDICATING DECENT RAIN ACCUMULATIONS
WITH THIS EVENT DUE TO ITS ACCESS TO ABUNDANT GULF MOISTURE.

HAVE THUS MAINTAINED LIKELY RAIN CHANCES ACROSS A MAJORITY OF THE
FORECAST AREA SATURDAY THROUGH SATURDAY NIGHT TO ACCOUNT FOR
HIGHER CONFIDENCE IN PRECIPITATION POTENTIAL. HIGH TEMPERATURES ON
SATURDAY WILL BE MITIGATED BY THICK CLOUD COVER AND NUMEROUS
SHOWERS...WITH TEMPERATURES PEAKING IN THE MID TO UPPER 60S. THERE
ARE SOME INDICATIONS IN THE MODELS THAT WEAK INSTABILITY COULD
DEVELOP ACROSS SOUTHEAST PORTIONS OF THE FORECAST AREA SATURDAY
AFTERNOON. LATER FORECAST SHIFTS MAY WANT TO EXAMINE MODEL TRENDS
AND DETERMINE WHETHER MENTION OF THUNDER SHOULD BE ADDED. PREFER
TO KEEP JUST SHOWERS IN THE FORECAST AT THIS TIME.

SATURDAY NIGHT AND SUNDAY...THE STRONG SURFACE LOW WILL BE LIFTING
NORTHEAST SATURDAY NIGHT...AND IF IT MAINTAINS A MORE INLAND
TRACK...THE DRY SLOT BEHIND THE SYSTEM COULD MOVE INTO THE
FORECAST AREA BY SUNDAY MORNING. STILL PREFER TO MAINTAIN AT LEAST
20 TO 30 PERCENT POPS THROUGH THE MORNING HOURS ON
SUNDAY...ACCOUNTING FOR SLOWER MODEL SOLUTIONS THAT COULD STILL
VERIFY. HOWEVER...THE GENERAL TREND WILL BE FOR SHOWERS TO END FROM
SOUTHWEST TO NORTHEAST AS THE DAY PROGRESSES...WITH POPS BELOW 15
PERCENT BY SUNDAY EVENING. ALTHOUGH THE SOUTHEAST STATES WILL BE
WITHIN THE COLD SECTOR OF THE SYSTEM ON SUNDAY...SIGNIFICANT
DOWNSLOPE FLOW COULD TEMPORARILY OFFSET THE COOLING TREND. WILL
THUS ADVERTISE HIGH TEMPERATURES STILL REACHING THE MID TO UPPER
60S SUNDAY AFTERNOON.

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
THE COOLING TREND BEHIND THE LIFTING LOW SYSTEM IN THE ATLANTIC
WILL BE APPARENT SUNDAY NIGHT...AS LOW TEMPERATURES FALL INTO THE
MID 30S INLAND TO AROUND 40 DEGREES NEAR THE COAST. EXPECT COOLER
HIGH TEMPERATURES ALSO ON MONDAY IN THE LOW 60S...DESPITE
ABUNDANT SUNSHINE WITHIN BUILDING SURFACE HIGH PRESSURE.

SURFACE HIGH PRESSURE AND UPPER LEVEL RIDGING WILL STEADILY
SHIFT TOWARD THE COASTLINE THROUGH TUESDAY. WILL MAINTAIN RAIN
FREE CONDITIONS SUNDAY EVENING THROUGH THE DAYTIME HOURS ON
TUESDAY AS A RESULT. ANOTHER LOW PRESSURE AND FRONTAL SYSTEM WILL
APPROACH FROM THE GULF OF MEXICO BY LATE TUESDAY...REINTRODUCING
RAIN CHANCES TUESDAY EVENING THROUGH WEDNESDAY AS IT LIFTS INTO
THE EAST COAST STATES. WILL INDICATE A STEADY WARMING TREND
THROUGH MID WEEK.

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
KCHS...AREAS OF MVFR CIGS AROUND THROUGH MID MORNING THEN A 
DEEP MOISTURE PROFILE FORECAST BY LATE MORNING WITH RAINS BOTH 
DEVELOPING AND SWEEPING IN FROM THE W. DURING THE RAINS THERE
COULD BE BRIEF IFR CONDITIONS WITH CIGS/VSBYS. SHOWERS SHOULD
END LATE AFTERNOON. THIS EVENING...THERE IS A POTENTIAL FOR
SOME LOW CLOUDS AND FOG IS THE COLD FRONT IS DELAYED. OUR 
CONFIDENCE IS VERY LOW AT THIS POINT.

KSAV...POCKETS OF IFR CIGS LINGER TO THE W OF THE TERMINAL THIS
MORNING AND IFR CONDITIONS ARE POSSIBLE UNTIL THE RAIN TO THE
W MOVES BY THE AREA BY MID AFTERNOON. BETTER CHANCES FOR VFR
BY THE MIDDLE OF THIS AFTERNOON. LIGHTER WINDS TONIGHT AND
INTRUSION OF DRIER AIR IN THE BOUNDARY LAYER MAY LEAD TO FOG
AND STRATUS DEVELOPMENT. DESPITE PESSIMISTIC MODEL TONIGHT WITH
IFR/LIFR GUIDANCE WE TREND INTO IT WITH MVFR VSBYS AND A CLOUD
LAYER BELOW 1 KFT AT 12Z.

BOTH TERMINALS SHOULD SEE LOWER CLOUDS BREAK UP LATE MORNING INTO
EARLY AFTERNOON BUT RISK FOR RAIN SHOWERS INCREASE DURING THE DAY.
FROM 00Z GUIDANCE...BEST RAIN CHANCES LOOK TO BE CLOSER TO KCHS
AND WE PREVAILED SOME SHOWERS IN.

AFTER SUNSET...THE FORECAST GETS VERY TRICKY ONCE AGAIN AS ZONE
OF LIGHTER WINDS MOVE IN AND A LAYER OF DRIER AIR ABOVE THE BOUNDARY
LAYER. IF RAINS FALL...FOG AND LOW CLOUDS MIGHT ARRIVE IN THE
00Z-06Z/17 TIME FRAME.

EXTENDED AVIATION OUTLOOK...
REDUCED CEILINGS/VISIBILITIES ARE POSSIBLE THURSDAY NIGHT AS A COLD 
FRONT MOVES THROUGH THE AREA. ANOTHER ROUND OF CEILING/VISIBILITY 
RESTRICTIONS IS POSSIBLE SATURDAY NIGHT AND SUNDAY AS A GULF OF 
MEXICO LOW SYSTEM IMPACTS PORTIONS OF THE AREA.

.MARINE...
THROUGH TONIGHT...THE LONE CONCERN SEEMS TO BE THE RISK FOR SEA
FOG OR TRAPPED ADVECTION FOG OVER THE COOL NEAR SHORE WATERS.
RESIDENCE TIMES FOR PURE SEA FOG CONDITIONS APPEARS MARGINAL
BUT MODELS DO HINT AT MID 60S LOW LEVEL DEW POINTS FOR A WHILE
LATER TODAY AND TONIGHT. UNTIL TRENDS BECOMES BETTER DEFINED
WE HAVE CONTINUED PATCHY FOG MENTIONS IN OUR FORECAST AND 
WILL CONTINUE THE BLURB IN OUR HAZARDOUS WX OUTLOOK. OTHERWISE...
POOR MIXING PROFILES SHOULD ENSURE FAIRLY LIGHT FLOW THROUGH
TONIGHT WITH SEAS 2-3 FT.

FRIDAY THROUGH MONDAY...SURFACE HIGH PRESSURE WILL BUILD FROM THE
NORTH ON FRIDAY...AS A FRONT LINGERS ACROSS THE GEORGIA/FLORIDA
BORDER. THIS BOUNDARY WILL LIFT NORTHWARD AS A WARM FRONT EARLY
SATURDAY...AHEAD OF A STRONG GULF LOW SYSTEM IMPACTING THE AREA
THROUGH SUNDAY. THE TRACK AND TIMING OF THE SYSTEM IS STILL VERY
UNCERTAIN...SO CONFIDENCE IN FORECAST DETAILS IS LOW AT THIS TIME.
GENERAL MODEL CONSENSUS INDICATES INCREASING SOUTHERLY FLOW
SATURDAY NIGHT INTO EARLY SUNDAY...BEFORE WINDS VEER OFFSHORE AS
THE LOW SYSTEM LIFTS TO THE NORTHEAST. SMALL CRAFT ADVISORY
CONDITIONS ARE POSSIBLE FOR PORTIONS OF THE WATERS AS EARLY AS
SATURDAY NIGHT...WITH BETTER POTENTIAL FOR HAZARDOUS MARINE
CONDITIONS WITHIN COLD ADVECTION BEHIND THE SYSTEM ON SUNDAY.
EXPECT WINDS AND SEAS TO SLOWLY IMPROVE AS HIGH PRESSURE BUILDS IN
THE WAKE OF THE LOW SYSTEM MONDAY.

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