141 FXUS62 KCHS 280909 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 509 AM EDT FRI MAR 28 2014 .SYNOPSIS... ATLANTIC HIGH PRESSURE WILL PREVAIL AS WEAK UPPER DISTURBANCES MOVE THROUGH THE AREA TODAY AND TONIGHT. A COLD FRONT WILL CROSS THE REGION SATURDAY AFTERNOON AND EVENING...FOLLOWED BY DRY HIGH PRESSURE THROUGH THURSDAY. A COLD FRONT MAY AFFECT THE AREA NEXT FRIDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... TODAY...SOUTHERLY RETURN FLOW WILL BECOME WELL ESTABLISHED TODAY AROUND HIGH PRESSURE SLOWLY DRIFTING ACROSS THE WESTERN ATLANTIC. THIS WILL ALLOW DEEPER MOISTURE TO ADVECT INTO THE REGION...WITH PRECIPITABLE WATER VALUES RISING FROM AROUND 1 INCH THIS MORNING TO 1.25-1.50 INCHES THIS AFTERNOON. ISOLATED TO SCATTERED SHOWERS AND PERHAPS A FEW THUNDERSTORMS WILL DEVELOP ALONG AN AXIS OF ENHANCED LOW LEVEL CONVERGENCE JUST OFF THE COAST THIS MORNING...WITH LOW LEVEL TRAJECTORIES SHIFTING THIS CONVECTION UP ALONG THE SC COAST AND INTO EASTERN PORTIONS OF THE CHARLESTON TRI-COUNTY AREA. THEN...THE POTENTIAL FOR SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE REST OF THE AREA WILL INCREASE THROUGH LATE AFTERNOON AS SHORT WAVE ENERGY EMBEDDED WITHIN THE SOUTHWEST FLOW ALOFT NEARS. SKIES WILL BECOME MOSTLY CLOUDY ACROSS THE AREA TODAY AS CIRRUS ASSOCIATED WITH A 110 KT UPPER JET OVERSPREADS THE AREA AND LOWER CLOUDS INCREASE IN COVERAGE AS MOISTURE DEEPENS. DESPITE THE CLOUD COVER AND INCREASING POTENTIAL FOR SHOWERS...THE RETURN SOUTHERLY FLOW SHOULD BE SUPPORTIVE OF HIGHS IN THE MID AND UPPER 70S ACROSS THE AREA AWAY FROM THE IMMEDIATE COAST. TONIGHT...ATLANTIC HIGH PRESSURE WILL PREVAIL AS A COLD FRONT APPROACHES FROM THE TENNESSEE VALLEY AND DEEP SOUTH. SOUTHERLY FLOW WILL CONTINUE TO ADVECT DEEP MOISTURE INTO THE REGION. THE COMBINATION OF THE DEEP LAYERED MOISTURE...FORCING FOR ASCENT ASSOCIATED WITH THE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET...AND A POTENT SHORT WAVE PASSING ALOFT WILL SUPPORT SCATTERED TO NUMEROUS SHOWERS ACROSS THE AREA...ESPECIALLY LATE THIS EVENING AND OVERNIGHT. IN ADDITION...INSTABILITY PARAMETERS/MID LEVEL LAPSE RATES ARE SUPPORTIVE OF AT LEAST ISOLATED THUNDERSTORMS AS WELL. TEMPERATURES WILL NOT FALL SIGNIFICANTLY GIVEN THE SOUTHERLY FLOW AND CLOUD COVER...WITH LOWS EXPECTED TO BE AROUND 60 IN MOST AREAS. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... A POTENT UPPER SHORTWAVE WILL MOVE INTO THE CENTRAL APPALACHIANS ON SATURDAY. SOUTHWEST FLOW WILL STRENGTHEN CONSIDERABLY AS THE DAY WEARS ON...WITH 0-6 KM WINDS 40-45 KT BY 00Z SUN. THIS WILL ALSO INCREASE MOISTURE ACROSS THE AREA WITH PWATS ABOVE 1.50 INCHES BY 18Z SAT. A COLD FRONT IS EXPECTED TO SWEEP THROUGH THE AREA SATURDAY EVENING. THERE REMAINS CONSIDERABLE UNCERTAINTY REGARDING THE DEGREE OF BOUNDARY LAYER DESTABILIZATION AHEAD OF THE FRONT. GIVEN THE EXTENSIVE LOW-LEVEL MOISTURE ADVECTING INTO THE REGION DURING THE DAY WE WOULD EXPECT TO HAVE QUITE A BIT OF LOW STRATOCUMULUS IN PLACE. HOWEVER SOME OF THE GUIDANCE IS DEPICTING A WEAK DRY SLOT DURING THE MIDDAY HOURS AFTER A BATCH OF MORNING PRECIP MOVES THROUGH. BOTH THE GFS AND NAM ARE SHOWING 1500 J/KG CAPES WITH LIFTED INDICES BELOW -4C DURING THE AFTERNOON ACROSS SOUTHEAST GA. THIS COINCIDES WITH 40-45 KT OF BULK SHEAR. IT IS ALSO WORTH NOTING THAT THE STORM PREDICTION CENTER STILL SHOWS OUR ENTIRE FORECAST AREA WITHIN THE DAY 2 SLIGHT RISK. WE PLAN TO ADD MENTION OF POSSIBLE SEVERE WEATHER TO THE HAZARDOUS WEATHER OUTLOOK. STRONG LOW-LEVEL WARM ADVECTION AND PRE-FRONTAL COMPRESSION ON SATURDAY WILL PUSH HIGH TEMPS INTO THE UPPER 70S. THIS COULD POTENTIALLY BE TOO COOL IF SOME BREAKS DEVELOP IN THE CLOUDS. CONSIDERABLE COVERAGE OF SHOWERS AND THUNDERSTORMS IS EXPECTED THROUGH SATURDAY EVENING BEFORE PRECIP TAPERS OFF BEHIND THE FRONT. A SLIGHT COOL DOWN IS EXPECTED FOR SUNDAY DUE TO COLD ADVECTION WITH THE HIGH BUILDING IN...HOWEVER DOWNSLOPE FLOW WILL ALLOW TEMPS TO REACH 70 OR THEREABOUTS. A 30-35 KT GEOSTROPHIC WIND FIELD AND DEEP MIXING WILL RESULT IN BREEZY CONDITIONS ESPECIALLY DURING THE HOURS OF PEAK HEATING. DRY WEATHER WITH MODERATING TEMPERATURES EXPECTED ON MONDAY WITH HIGHS REBOUNDING INTO THE LOWER TO MIDDLE 70S. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... A BROAD UPPER LEVEL RIDGE WILL PREVAIL MONDAY NIGHT THROUGH THURSDAY WITH DRY HIGH PRESSURE AT THE SURFACE. THIS WILL RESULT IN ABOVE NORMAL TEMPERATURES WITH HIGHS CLIMBING INTO THE UPPER 70S OR LOWER 80S AND LOWS MAINLY IN THE 50S. THE UPPER RIDGE BREAKS DOWN ON FRIDAY WITH A WEAK COLD FRONT POSSIBLY MOVING IN FROM THE WEST. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... VFR CONDITIONS SHOULD GENERALLY PREVAIL AT BOTH KCHS AND KSAV THROUGH AT LEAST THIS AFTERNOON. BRIEF/ISOLATED SHOWERS ARE POSSIBLE AROUND KCHS FROM JUST PRIOR TO DAYBREAK AND CONTINUING THROUGH MUCH OF THE MORNING...BUT GIVEN LIMITED COVERAGE AND OVERALL LOW CONFIDENCE...THERE WILL BE NO MENTION IN THE KCHS TAF. BREEZY CONDITIONS WILL DEVELOP THIS AFTERNOON WITH GUSTS UPWARDS OF 20 KT AT TIMES. INCREASING LOW LEVEL MOISTURE COULD RESULT IN PERIODIC CEILING RESTRICTIONS TO MVFR LEVELS AFTER 00Z. IN ADDITION... THE POTENTIAL FOR SCATTERED OR EVEN NUMEROUS SHOWERS WILL INCREASE AFTER 00Z THUS HAVE ADDED VICINITY SHOWERS TO THE FORECAST AT BOTH TERMINALS. EXTENDED AVIATION OUTLOOK...OCCASIONAL FLIGHT RESTRICTIONS POSSIBLE SATURDAY AFTERNOON AND EVENING IN SCATTERED SHOWERS AND THUNDERSTORMS. VFR CONDITIONS EXPECTED THEREAFTER. BREEZY CONDITIONS EXPECTED ON SUNDAY. && .MARINE... TODAY...A SOUTHERLY RETURN FLOW WILL BECOME WELL ESTABLISHED ACROSS THE COASTAL WATERS TODAY AS ATLANTIC HIGH PRESSURE PREVAILS. DESPITE SOME STRONGER WINDS ALOFT...MIXING WILL REMAIN LIMITED OVER THE COOLER NEAR SHORE WATERS THUS WINDS AT THE SURFACE SHOULD NOT EXCEED 10 TO 15 KT. HOWEVER...WINDS OVER THE OUTER GA WATERS AND IN CHARLESTON HARBOR ALONG THE LAND/SEA INTERFACE COULD REACH UPWARDS OF 15 TO 20 KT AT TIMES THIS AFTERNOON. A SOUTHEAST SWELL WILL KEEP SEAS ELEVATED IN THE 3-5 FT RANGE TODAY...WITH A SMALL POTENTIAL FOR SOME 6 FT SEAS TO ENCROACH UPON THE FAR REACHES OF THE OUTER GA WATERS. GIVEN LIMITED CONFIDENCE...HAVE OPTED TO NOT ISSUE A SMALL CRAFT ADVISORY...ALTHOUGH CONDITIONS COULD WARRANT OTHERWISE LATER TODAY. DEW POINTS SURGING INTO THE LOWER 60S WITHIN THE SOUTHERLY FLOW COULD SUPPORT THE DEVELOPMENT OF PATCHY SEA FOG LATER THIS AFTERNOON ACROSS THE NEAR SHORE WATERS. TONIGHT...THE SOUTHERLY FLOW WILL STRENGTHEN TO UPWARDS OF 15 TO 20 KT ACROSS THE COASTAL WATERS AS THE SURFACE PRESSURE GRADIENT TIGHTENS BETWEEN ATLANTIC HIGH PRESSURE AND A COLD FRONT WELL TO THE WEST. A SOUTHEAST SWELL WILL KEEP SEAS SOLIDLY IN THE 3-5 FT RANGE...HIGHEST ACROSS THE OUTER GA WATERS. THERE IS A SMALL POTENTIAL THAT MARGINAL SMALL CRAFT ADVISORY CONDITIONS FOR WINDS AND/OR SEAS COULD OCCUR OVER THE OUTER GA WATERS...BUT NOT ENOUGH CONFIDENCE TO RAISE AN ADVISORY AT THIS TIME. THE POTENTIAL FOR PATCHY SEA FOG WILL PERSIST TONIGHT ACROSS THE NEAR SHORE WATERS AND CHARLESTON HARBOR AS A WARM/MOIST SOUTHERLY FLOW PREVAILS. SATURDAY THROUGH TUESDAY...WIND FIELDS WILL INCREASE SATURDAY INTO SATURDAY NIGHT AS A STRONG COLD FRONT MOVES THROUGH. ON SATURDAY THE FLOW WILL BE OUT OF THE SOUTH AND CONDITIONS SHOULD REMAIN BELOW ADVISORY CRITERIA. BUT ONCE COLD ADVECTION CRANKS UP LATE SATURDAY EVENING AND OVERNIGHT AND GEOSTROPHIC WINDS INCREASE TO 35-40 KT...WE EXPECT SMALL CRAFT ADVISORY CONDITIONS ON MOST IF NOT ALL MARINE ZONES. CONDITIONS WILL QUICKLY IMPROVE ON SUNDAY AS THE HIGH PRESSURE CENTER MOVES CLOSER TO THE WATERS. FAIRLY QUIET WINDS/SEAS ANTICIPATED SUNDAY NIGHT THROUGH MID WEEK AS THE HIGH PRESSURE DOMINATES. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...NONE. && $$ SYNOPSIS... NEAR TERM...JAQ SHORT TERM...JRL LONG TERM...JRL AVIATION...JAQ/JRL MARINE...JAQ/JRL