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Current Version Previous Versions: 1 2 3 4 5 6 7 8 9 Area Forecast Discussion469 FXUS62 KCHS 030226 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 1026 PM EDT WED OCT 2 2013 .SYNOPSIS... HIGH PRESSURE WILL PREVAIL UNTIL A COLD FRONT APPROACHES FROM THE WEST EARLY NEXT WEEK. HIGH PRESSURE WILL THEN RETURN TO THE REGION BY THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... HIGH PRESSURE AT THE SURFACE WILL CONTINUE TO PREVAIL OVER THE REGION TONIGHT...WHILE A MID LEVEL RIDGE AXIS SHIFTS OFF THE SOUTHEAST COAST. ON THE WESTERN PERIPHERY OF THE RIDGE AXIS...SOME MAINLY HIGH LEVEL CLOUD COVER SHOULD BEGIN TO ADVECT INTO THE REGION FROM THE SOUTHWEST BUT OVERALL EXPECT SKIES TO REMAIN MOSTLY CLEAR. WHILE RADIATIONAL COOLING COULD BE SOMEWHAT LIMITED BY ANY INCREASE IN CLOUD COVER...STILL EXPECT LOWS IN THE UPPER 50S TO AROUND 60 AWAY FROM THE IMMEDIATE COAST...WITH SOME MID 50S POSSIBLE IN WELL SHELTERED INLAND LOCATIONS. IT SHOULD BE NOTED THAT A FEW LOCATIONS COULD EXPERIENCE PATCHY SHALLOW GROUND FOG...MAINLY NEAR DAWN...BUT COVERAGE WILL REMAIN TOO LOW TO MENTION IN THE FORECAST AT THIS TIME. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... THURSDAY AND THURSDAY NIGHT...THE AXIS OF THE UPPER RIDGE ALOFT WILL MOVE OUT OVER THE ATLANTIC ALLOWING FOR THE PATTERN TO FLATTEN OUT A BIT DURING THE DAY. DRY HIGH PRESSURE WILL REMAIN IN CONTROL AT THE SURFACE WITH ITS CENTER POSITIONED OFF THE NC COASTLINE. MODEL TIME HEIGHTS AND CROSS SECTIONS SHOW A CONSIDERABLE AMOUNT OF DRY AIR THROUGH THE COLUMN...SUPPORTIVE OF PWATS AROUND AN INCH. THE DRY FORECAST HAS BEEN MAINTAINED AS A RESULT. THANKS TO THE RIDGE AND HIGHER HEIGHTS ALOFT...A SEASONALLY MILD DAY IS ON TAP. THICKNESSES SUPPORT TEMPS IN THE MID 80S WHICH IS ABOUT 5 DEGREES ABOVE CLIMO. FRIDAY THROUGH SATURDAY...THE FLATTENED UPPER RIDGE WILL REAMPLIFY AND BECOME INCREASINGLY CENTERED OVER THE REGION THROUGH THE FIRST PART OF THE WEEKEND. THIS RESULTS IN HIGH PRESSURE CONTINUING TO BE THE PRIMARY SURFACE FEATURE IN CONTROL ACROSS THE FORECAST AREA. THE DRY FORECAST CONTINUES THROUGH THIS PERIOD AS WELL THANKS TO THE PRESENCE OF NVA ALOFT...A PROMINENT SUBSIDENCE INVERSION...AND CONSIDERABLE DRY AIR IN THE MID/UPPER LEVELS. THERE WILL BE A BIT OF AN INCREASE IN MOISTURE IN THE 5 KFT RANGE THANKS TO THE ONSHORE EASTERLY FLOW...BUT THIS WILL PRIMARILY MANIFEST ITSELF AS A MODEST INCREASE IN MAINLY DIURNAL CLOUD COVER. MODEL THICKNESSES ACTUALLY INCREASE AS THE RIDGE AMPLIFIES EACH DAY...AND SOME HIGHS IN THE UPPER 80S WILL BE POSSIBLE EACH AFTERNOON. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... MEDIUM RANGE MODEL SOLUTIONS CONTINUE TO SHOW SIGNIFICANT DISCREPANCIES REGARDING THE EVOLUTION OF SYNOPTIC SCALE FEATURES INTO EARLY NEXT WEEK. AT THIS POINT...PREFER TO CONTINUE FAVORING THE LESS AGGRESSIVE ECMWF/WPC SCENARIOS THROUGH THE EXTENDED PERIOD. THE AXIS OF THE UPPER RIDGE WILL SLIP OFF THE EAST COAST ON SUNDAY...WHILE ATLANTIC SURFACE HIGH PRESSURE RETREATS AHEAD OF A SYSTEM MOVING INTO THE MISSISSIPPI VALLEY. THIS STRONG UPPER TROUGH WILL SUPPORT THE DEVELOPMENT AND EASTWARD MOVEMENT OF A COLD FRONT INTO THE OHIO/TENNESSEE VALLEYS BY EARLY MONDAY...BEFORE LIFTING WELL NORTH INTO THE GREAT LAKES REGION. WITH THE STRONGEST ENERGY ALOFT THUS BECOMING REMOVED FROM THE SOUTHERN EXTENT OF THE COLD FRONT...EXPECT FRONTAL PROGRESSION TO SLOW AS THE FEATURE RUNS INTO RESIDUAL RIDGING ALONG THE EAST COAST. FRONTAL PASSAGE COULD BECOME DELAYED AND/OR ILL-DEFINED BY EARLY NEXT WEEK...EVEN POTENTIALLY STALLING AND/OR WASHING OUT JUST WEST/NORTHWEST OF THE FORECAST AREA. HAVE REINTRODUCED RAIN CHANCES ON SUNDAY...AS RETURN FLOW AROUND THE ATLANTIC HIGH PRESSURE ALLOWS DEEPER MOISTURE TO SHIFT INTO THE REGION WITHIN WARM ADVECTION AHEAD OF THE FRONT. WILL THEN HIGHLIGHT MONDAY FOR THE BEST SHOWER/THUNDERSTORM POTENTIAL...WHEN CONVERGENCE IS MAXIMIZED AHEAD AND ALONG THE FRONTAL ZONE JUST UPSTREAM. PREFER TO MAINTAIN SLIGHT CHANCE POPS INTO TUESDAY TO ACCOUNT FOR THE STALLED...AND POSSIBLY DISSIPATING...FRONT IN THE VICINITY. CONSIDERING LITTLE SIGNIFICANT AIR MASS CHANGE IF THE FRONT DOES NOT PROGRESS INTO THE FORECAST AREA...HAVE INDICATED ONLY A SUBTLE COOLING TREND EARLY NEXT WEEK. HIGH TEMPERATURES WILL REACH THE LOW TO MID 80S SUNDAY AFTERNOON...THEN AVERAGE IN THE LOW 80S MONDAY THROUGH WEDNESDAY. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... VFR CONDITIONS WILL PREVAIL AT KCHS AND KSAV THROUGH 00Z FRIDAY. EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED TO PREVAIL. && .MARINE... TONIGHT...WINDS/SEAS WILL CONTINUE TO REMAIN WELL BELOW SMALL CRAFT ADVISORY LEVELS AS HIGH PRESSURE DOMINATES THE COASTAL WATERS WHILE WEAK LOW PRESSURE REMAINS POSITIONED WELL OFFSHORE IN THE WESTERN ATLANTIC. EAST WINDS BELOW 10 KT WILL GRADUALLY BECOME MORE NORTHEAST OVERNIGHT. SEAS WILL RANGE FROM 1-2 FT IN NEARSHORE WATERS TO 2-3 FT IN OFFSHORE WATERS. THURSDAY THROUGH MONDAY...TRANQUIL CONDITIONS ARE EXPECTED ACROSS THE WATERS THROUGH SATURDAY. HIGH PRESSURE WILL BE IN CONTROL ACROSS THE LOCAL WATERS RESULTING IN A PREDOMINANTLY EASTERLY FLOW. WIND SPEEDS WILL LESS THAN 15 KTS AND SEAS 1-3 FT...HIGHEST OVER THE OUTER WATERS. THERE WILL BE A SLIGHT SURGE IN EAST/SOUTHEAST FLOW BY SUNDAY...AS THE PRESSURE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. HOWEVER...CONDITIONS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH THE PERIOD. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...NONE. && $$ SYNOPSIS... NEAR TERM...JAQ SHORT TERM...BSH LONG TERM...WMS AVIATION...JAQ/BSH MARINE...JAQ/DPB/BSH |