Area Forecast Discussion
Issued by NWS Charleston, SC

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832
FXUS62 KCHS 120617
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
117 AM EST FRI FEB 12 2016

.SYNOPSIS...
WEAK LOW PRESSURE WILL MOVE EAST THROUGH THE AREA TONIGHT. THE LOW
WILL PULL AWAY FROM THE AREA FRIDAY...THEN AN ARCTIC COLD FRONT WILL
PUSH THROUGH EARLY SATURDAY. HIGH PRESSURE WILL THEN REMAIN IN CONTROL
UNTIL EARLY NEXT WEEK WHEN THE NEXT FRONTAL SYSTEM WILL IMPACT THE
REGION. MORE HIGH PRESSURE WILL RETURN THEREAFTER.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
WEAK LOW PRESSURE OVER CENTRAL ALABAMA WILL TRANSLATE EAST ALONG
A WEST-EAST ORIENTED STATIONARY FRONT AND REDEVELOP OFF THE SOUTH
CAROLINA COAST FRIDAY MORNING. GOES-EAST IR IMAGERY SHOWS CLOUDS
BEGINNING TO QUICKLY FILL IN AS ISENTROPIC ASSENT INTENSIFIES
AHEAD OF THE APPROACHING SURFACE LOW. WOULD NOT BE SURPRISED TO
SEE SOME LIGHT SPRINKLES DEVELOP AFTER MIDNIGHT GIVEN THE
STRENGTHEN OF THE ISENTROPIC LIFT...HOWEVER FORECAST SOUNDINGS
KEEP A VERY DRY 5000 FT SUB-CLOUD LAYER IN PLACE FOR MUCH OF THE
NIGHT WITH CONDENSATION PRESSURE DEFICITS HOLDING IN EXCESS OF 50
MB ALONG THE 285-295K SURFACES. THIS SHOULD BE ENOUGH TO KEEP ANY
PRECIPITATION THAT DEVELOPS AS VIRGA AND THUS NON-MEASURABLE.

TEMPERATURES HAVE LEVELED OFF AND HAD RISEN IN SOME AREAS. THERE
REMAINS MUCH UNCERTAINTY IN HOURLY TEMPERATURE FORECASTS AS ANY
CHANGE IN EXTENT OF THE CLOUD CANOPY WILL HAVE A BIG IMPACT ON
THE TEMPERATURE FORECAST.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/...
FRIDAY MORNING THE AREA WILL BE BISECTED BY A WEST TO EAST COLD
FRONT WHILE WEAK LOW PRESSURE DEVELOPS ALONG IT JUST OFF THE SC
COAST. ALTHOUGH THE BEST FORCING FOR ASCENT WILL REMAIN ALONG AND
EAST OF THE LOW PRESSURE CENTER...SOME ISENTROPIC ASCENT WILL
DEVELOP AROUND DAYBREAK ACROSS SOUTHERN SC AS THE FRONTAL ZONE
TIGHTENS UP AND THE LOW STRENGTHENS. WE INTRODUCED SLIGHT CHANCE
OF RAIN OVER OUR SC AND FAR EASTERN GA ZONES DURING FRIDAY
DAYTIME. THE FRONT WILL PRODUCE A WIDE RANGE OF HIGH TEMPS ON
FRIDAY WITH UPPER 60S FAR SOUTH TO UPPER 40S FAR NORTH.

THE COLD FRONT WILL DROP SOUTH OF THE AREA FRIDAY EVENING WITH
HIGH PRESSURE BUILDING IN AND COLD NORTHWEST FLOW DEVELOPING. LOWS
WILL DIP INTO THE MID 30S INLAND TO LOWER 40S SOUTH.

COLD ADVECTION ON SATURDAY WILL BE REINFORCED BY ANOTHER ARCTIC
COLD FRONT SATURDAY EVENING...RESULTING IN BELOW NORMAL
TEMPERATURES OVER THE WEEKEND. SATURDAY HIGHS WILL BE IN THE UPPER
40S TO LOWER 50S.

THE COMBINATION OF INCREASING NNE WINDS LATE SATURDAY NIGHT AND
STRONG COLD ADVECTION WILL NOT ONLY DROP TEMPERATURES INTO THE LOW
TO MID 20S...BUT WIND CHILL READINGS WILL BE IN THE TEENS. WE
CANNOT RULE OUT THE POTENTIAL FOR WIND CHILL ADVISORY CONDITIONS
SUNDAY MORNING. SUNDAY WILL ONLY SHOW HIGHS IN THE UPPER 30S TO
LOW/MID 40S.

LAKE WINDS...ANOTHER ROUND OF STRONG WINDS WILL BE POSSIBLE OVER
LAKE MOULTRIE LATE SATURDAY INTO SUNDAY. A LAKE WIND ADVISORY COULD
EVENTUALLY BE NEEDED.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
MODEL AGREEMENT REMAINS GOOD REGARDING THE MAIN FORECAST ISSUE IN
THE LONG TERM WHICH IS A SYSTEM EXPECTED TO PUSH THROUGH LATE
MONDAY THROUGH EARLY TUESDAY. THE PERIOD WILL START OFF WITH HIGH
PRESSURE OVER NEW ENGLAND AND A STRENGTHENING WEDGE INLAND AND A
SHARPENING COASTAL TROUGH OFFSHORE. LOW PRESSURE IS PROGGED TO
MOVE INLAND THROUGH CENTRAL GEORGIA AND THE CAROLINAS MONDAY
NIGHT. THE BEST TIME PERIOD FOR RAINFALL LOOKS TO BE DURING THIS
TIME AS THE DEEP MOISTURE ASSOCIATED WITH THE SYSTEM DOES NOT
PRECEDE IT BY MUCH. MODEL AGREEMENT IS GOOD ENOUGH TO GO WITH
LIKELY POPS...THOUGH IT SHOULDN/T BE A LONG DURATION EVEN THANKS
TO THE PROGRESSIVE NATURE OF THE MID/UPPER LEVEL TROUGH. BEHIND
THIS SYSTEM...DRY HIGH PRESSURE WILL RETURN. TEMPERATURES LOOK AS
THOUGH THEY WILL MODERATE THROUGH THE PERIOD...STARTING OFF BELOW
NORMAL MONDAY WITHIN THE WEDGE...THEN INCREASING THEREAFTER TO
NEAR NORMAL BY MID WEEK.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
VFR WILL PREVAIL AT BOTH TERMINALS FOR SEVERAL MORE HOURS. CURRENT
DATA SUPPORT CIGS DROPPING TO MVFR THRESHOLDS AFTER SUNRISE
FRIDAY...WHILE AT KSAV MVFR CIGS LOOK TO SETTLE IN BY 10Z-11Z
TONIGHT. THE BEST CHANCES FOR IFR CIGS STILL LOOK TO OCCUR AT
KSAV FRIDAY MORNING...BUT PROBABILITIES REMAIN TOO LOW TO JUSTIFY
AN INCLUSION. PATCHES OF LIGHT RAIN WILL LIKELY DEVELOP NEAR
KCHS LATE TONIGHT...BUT NO MEANINGFUL VSBY REDUCTIONS ARE EXPECTED
GIVEN THE DRY SUB-CLOUD LAYER. VFR WILL RETURN TO BOTH TERMINALS
BY LATE AFTERNOON AS LOW PRESSURE MOVES AWAY FROM THE AREA.

EXTENDED AVIATION OUTLOOK...A FAIRLY POTENT LOW PRES AREA IS
EXPECTED TO PRODUCE FLIGHT RESTRICTIONS AS IT PASSES THROUGH
THE REGION MONDAY INTO TUESDAY. GUSTY SURFACE WINDS ARE EXPECTED
ON TUESDAY.

&&

.MARINE...
OVERNIGHT...WEAK LOW PRESSURE ALONG A STATIONARY FRONT NEAR THE
SAVANNAH RIVER WILL SHIFT INTO THE WATERS FROM THE WEST BY DAWN.
MOSTLY SOUTHERLY WINDS THIS EVENING WILL BACK TO MORE EASTERLY
ACROSS THE SC WATERS AND VEER TO THE SOUTHWEST AFTER
MIDNIGHT...THEN BECOME SOUTHWEST FOR MOST OF THE WATERS EXCEPT
CLOSER TO THE SANTEE RIVER TOWARD DAYBREAK. WINDS COULD GUST NEAR
25 KT TOWARD THE GULF STREAM LATE BUT DO NOT EXPECT AN ADVISORY
FOR THE OVERNIGHT PERIOD. SEAS TO BUILD A BIT...UP TO 4 FT NEAR
THE GULF STREAM BUT MAINLY 2 FT OR LESS WITHIN 20 NM.

FRIDAY THROUGH MONDAY...WESTERLY WINDS INCREASE ON FRIDAY OVER
THE SOUTHERN HALF OF THE MARINE AREA DUE TO LOW-LEVEL JETTING
AHEAD OF A COLD FRONT. AN 8 TO 10 HOUR WINDOW OF 25 KT GUSTS IS
EXPECTED OVER OUTER PORTIONS OF THE OFFSHORE GA WATERS SO WE
ISSUED A SMALL CRAFT ADVISORY FOR THAT ZONE DURING FRIDAY DAYTIME.

ONCE THE WEAK LOW PRESSURE SYSTEM MOVES OFF TO THE NORTHEAST ON
FRIDAY THE NEXT SYSTEM WILL BE AN ARCTIC COLD FRONT MOVING THROUGH
SATURDAY. WINDS WILL TURN TO THE NORTH AND THEN NORTHEAST BEHIND A
SECONDARY SURGE SATURDAY NIGHT. THE SURGE BEHIND THE FRONT
SATURDAY NIGHT WILL RESULT IN SOLID SMALL CRAFT ADVISORY
CONDITIONS ACROSS ALL WATERS WHICH WILL CONTINUE THROUGH AT LEAST
SUNDAY MORNING. OTHERWISE...CONDITIONS SHOULD IMPROVE INTO MONDAY
WHEN A COASTAL TROUGH WILL DEVELOP AND EVENTUALLY LIFT NORTHWARD
AHEAD OF AN APPROACHING LOW PRESSURE SYSTEM.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM THIS MORNING TO 6 PM EST THIS
     EVENING FOR AMZ374.

&&

$$

SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...



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