Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 031813
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
113 PM EST TUE MAR 3 2015

.SYNOPSIS...
A COLD FRONT WILL STALL JUST SOUTH OF THE AREA THIS MORNING...THEN
LIFT BACK NORTH AS A WARM FRONT THIS AFTERNOON THROUGH TONIGHT. HIGH
PRESSURE WILL REMAIN CENTERED OVER THE ATLANTIC WEDNESDAY...WHILE
A COLD FRONT APPROACHES FROM THE NORTHWEST AND PASSES THROUGH THE
REGION THURSDAY. COLDER HIGH PRESSURE WILL BUILD OVER THE AREA INTO
EARLY SATURDAY...WITH A COASTAL TROUGH TO DEVELOP OFFSHORE INTO
SUNDAY. ANOTHER COLD FRONT COULD IMPACT THE AREA EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
EARLY THIS AFTERNOON...LIGHT SHOWERS HAVE DISSIPATED AS THEY HAVE
PROGRESSED TO THE EAST AND RETREATED FURTHER TO THE NORTH. VISIBLE
SATELLITE IMAGERY SHOWS THAT CLOUDS HAVE SCATTERED OUT FROM THE
SOUTH WITH MUCH OF SOUTHEAST GEORGIA NOW SEEING PLENTY OF
SUNSHINE. TEMPERATURES IN THESE AREAS HAVE WARMED INTO THE LOW 70S
WITH MID/UPPER 50S AND LOW 60S ELSEWHERE FURTHER NORTH. POPS HAVE
BEEN TRIMMED FROM THE SOUTH THIS AFTERNOON AND TEMPERATURES STILL
SEEM TO BE LARGELY ON TRACK. NO OTHER SIGNIFICANT CHANGES HAVE
BEEN MADE.

TONIGHT AS THE FRONT MOVES NORTH OF THE AREA...THE MAIN CONCERN
IS FOG AND WITH HIGHLY ELEVATED DEW POINTS STREAMING IN...THE
CONCERN IS SIGNIFICANT. SREF AND NAM FOG VSBY PROGS BOTH SHOW A
VERY BELIEVABLE PATTERN WHERE MARINE AND COASTAL FOG EXPANDS NORTH
AND WEST OVERNIGHT PRODUCING A FAVORABLE REGIME FOR WIDESPREAD
DENSE FOG POTENTIAL. ONE CAVEAT IS A MARKED INCREASE IN BOUNDARY
LAYER WINDS EARLY WEDNESDAY MORNING WHICH COULD TEND TO LIFT THE
STRATUS DECKS JUST A BIT. THE HIGHEST POTENTIAL IS ALONG AND E OF
I-95 WHERE FOG COULD ADVECT IN OR DEVELOP DURING THE EVENING
HOURS AND DENSE FOG ADVISORIES MAY BE REQUIRED.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
WEDNESDAY...SURFACE HIGH PRESSURE WILL REMAIN CENTERED OVER THE
ATLANTIC...WHILE A COLD FRONT MOVES EAST AND APPROACHES THE
APPALACHIANS. RIDGING ALOFT AND SOUTHERLY RETURN FLOW WILL HELP
BOOST TEMPERATURE WELL ABOVE NORMAL. HIGHS WILL MAINLY BE IN THE
UPPER 70S/AROUND 80 AWAY FROM THE LOCALLY COOLER COASTLINE.
MODELS ARE SPITTING OUT SOME LIGHT QPF...HOWEVER GIVEN LACK OF
SIGNIFICANT FORCING AND MEAGER MOISTURE HAVE OPTED TO KEEP A DRY
FORECAST IN TACT. WITH WARM MOIST AIRMASS IN PLACE...THERE IS A
POTENTIAL FOR FOG DEVELOPMENT WEDNESDAY NIGHT INTO THURSDAY
MORNING. THUS HAVE MAINTAINED PATCHY FOG IN THE FORECAST. LOW
TEMPERATURES WILL BE QUITE MILD IN THE UPPER 50S/AROUND 60.

THURSDAY...THE AFOREMENTIONED COLD FRONT WILL CONTINUE TO PROGRESS
EAST TOWARDS AND THROUGH THE FORECAST AREA IN THE AFTERNOON. THERE
ARE STILL SOME MODEL DISCREPANCIES ON TIMING WITH GFS/ECMWF A BIT
QUICKER THAN THE NAM. HAVE NUDGED TEMPERATURES UP A FEW DEGREES
SEEING THE SLOWER FRONTAL PASSAGE...HOWEVER FUTURE FORECASTS MAY
EVEN NEED TO BE TWEAK HIGHER THAN THE CURRENT FORECAST OF UPPER
60S/LOW 70S. SOME RAIN WILL ACCOMPANY THE FRONT BUT GIVEN ITS
WEAKENING STATE...QPF SHOULD LESS THAN A QUARTER OF AN INCH.
UNIMPRESSIVE LAPSE RATES AND INSTABILITY WILL KEEP THUNDER MENTION
OUT OF FORECAST. THURSDAY NIGHT...HIGH PRESSURE WILL BUILD IN BEHIND
THE DEPARTING FRONT. COOL NORTH/NORTHEAST FLOW WILL HELP TEMPS DROP
TO THE MID 30S/AROUND 40.

FRIDAY...SURFACE HIGH PRESSURE WILL BUILD IN TO THE NORTH WHILE THE
FRONT STALLS TO OUR SOUTH. WEAK MID LEVEL DISTURBANCE EMBEDDED
WITHIN SOUTHWEST FLOW ALOFT WILL CROSS SOUTHEAST GEORGIA AND COMBINE
WITH HIGHER MOISTURE TO SUPPORT SLIGHT CHANCE POPS ACROSS OUR FAR
SOUTHEAST ZONES. TEMPERATURES WILL BE MUCH COOLER THAN PREVIOUS
DAYS...WITH HIGHS ONLY PEAKING IN THE UPPER 40S/AROUND 50.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
THERE IS QUITE A BIT OF UNCERTAINTY IN THE LONG TERM PERIOD AS THERE
ARE SIGNIFICANT DIFFERENCES BETWEEN MODEL SOLUTIONS. THE GENERAL
SURFACE PATTERN WILL FEATURE HIGH PRESSURE CENTERED INLAND WHILE A
COASTAL TROUGH DEVELOPS OFFSHORE. THE TROUGH MAY CLOSE OFF INTO A
LOW BEFORE LIFTING NORTHEAST OF THE AREA LATE IN THE WEEKEND.
GENERALLY TEMPERATURES WILL BE COOLER THAN NORMAL INTO EARLY NEXT
WEEK...WITH SLIGHT CHANCE/CHANCE OF RAIN. ANOTHER FRONT MAY IMPACT
THE AREA EARLY NEXT WEEK.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
MVFR CEILINGS CONTINUE AT KCHS AND LIKELY WILL FOR THE NEXT FEW
HOURS. VFR CONDITIONS HAVE TAKEN HOLD AT KSAV AND THIS WILL LIKELY
CONTINUE THROUGH SUNSET. OVERNIGHT...THE ISSUE FOR BOTH TERMINALS
WILL BE THE POTENTIAL FOR FOG/STRATUS DEVELOPMENT AND ESPECIALLY
DENSE FOG. GUIDANCE CONTINUES TO HIT FLIGHT RESTRICTIONS QUITE
HARD WITH BOTH SITES GOING IFR FOR MUCH OF THE NIGHT AND MUCH OF
WEDNESDAY MORNING. THE PRIMARY QUESTION REVOLVES AROUND FOG
DEVELOPMENT AND THE CHANCES FOR DENSE FOG. THE OVERALL SETUP IS
GOOD WITH A WARM/MOIST AIRMASS OVERSPREADING THE AREA IN SOUTHERLY
FLOW WITHIN A STRONG SURFACE BASED INVERSION. THE MAIN ISSUE THAT
MAY KEEP DENSE FOG FROM BECOMING TOO WIDESPREAD IS THE INCREASING
LOW LEVEL FLOW. IN SOME WAYS THE STRONGER WINDS IN THE LOWEST 1
KFT MAY FAVOR MORE STRATUS OVER FOG...BUT IT IS LIKELY THAT THERE
WILL BE PLENTY OF FOG ONGOING OVER THE ADJACENT COASTAL WATERS.
THE EXPECTATION IS THAT THIS MARINE FOG WILL BE ADVECTED ONSHORE
AND IMPACT THE TERMINALS THROUGH AT LEAST DAY BREAK. IFR CEILINGS
WILL THEN STICK AROUND INTO MID MORNING WITH SOME IMPROVEMENT
TOWARDS THE END OF THE TAF PERIOD.

EXTENDED AVIATION OUTLOOK...FLIGHT RESTRICTIONS LIKELY MUCH OF
THE TIME THROUGH THURSDAY. POTENTIAL FOR SOME VFR CONDITIONS
WEDNESDAY AND AGAIN THURSDAY NIGHT AND FRIDAY.

&&

.MARINE...
TODAY...THE GRADIENT REMAINS A BIT PINCHED ALONG THE CHARLESTON
COUNTY WATERS BUT WINDS HAVE DIMINISHED ENOUGH TO ALLOW THE SMALL
CRAFT ADVISORY TO EXPIRE. WINDS WILL CONTINUE TO STEADILY DROP OFF
THROUGH THE AFTERNOON AND WILL GRADUALLY TURN MORE SOUTHEASTERLY
WITH TIME AS A WEAK WARM FRONT LIFTS NORTHWARD. WE WILL BE KEEPING
A CLOSE EYE ON THE POTENTIAL FOR SEA FOG DEVELOPMENT WHICH WILL
LIKELY BEGIN FIRST ALONG THE GEORGIA COAST AS INCREASINGLY MOIST
AIR IS USHERED IN BEHIND THE WARM FRONT. THE ONSET OF PATCHY FOG
HAS BEEN DELAYED A FEW HOURS UNTIL THE AFTERNOON.

TONIGHT...THE MAIN ISSUE WILL BE FOG DEVELOPMENT. THE ENVIRONMENT
TODAY WILL BE INCREASINGLY FAVORABLE FOR SEA FOG DEVELOPMENT OFF
THE GEORGIA COAST AND DENSE FOG WILL LIKELY BUILD NORTH UP THE
SOUTH CAROLINA COAST OVERNIGHT. IT IS NOT OUT OF THE QUESTION
MARINE FOG ADVISORIES WILL ISSUED AS EARLY AS THIS MORNING TO THE
SOUTH OF EDISTO BEACH GIVEN ELEVATED DEW POINTS ALONG WITH NEAR
SHORE STRATUS BUILD-DOWN.

WEDNESDAY THROUGH SATURDAY NIGHT...SURFACE HIGH PRESSURE WILL BE
CENTERED EAST OF THE WATERS WEDNESDAY INTO THURSDAY AHEAD OF AN
APPROACHING COLD FRONT. GIVEN WARM MOIST AIRMASS MOVING OVER THE
COOLER ...SEA FOG WILL LIKELY DEVELOP. VISIBILITIES MAY DROP TO 1
NM OR LESS AND DENSE FOG ADVISORIES MAY EVENTUALLY BE NEEDED. THUS
HAVE MAINTAINED AREAS OF FOG IN THE FORECAST WEDNESDAY INTO
THURSDAY. THE COLD FRONT WILL PUSH THROUGH THE WATERS THURSDAY
EVENING WITH WINDS/SEAS INCREASING BOTH AHEAD OF AND BEHIND THE
FRONT. SMALL CRAFT ADVISORIES WILL BE POSSIBLE FOR MOST MARINE
LEGS THURSDAY AFTERNOON INTO FRIDAY AFTERNOON. SURFACE HIGH
PRESSURE WILL BUILD INLAND FRIDAY WITH A COASTAL TROUGH DEVELOPING
ON SATURDAY.

&&

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

&&

$$

NEAR TERM...BSH
SHORT TERM...ECT
LONG TERM...ECT
AVIATION...BSH
MARINE...BSH/ECT


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