606 FXUS61 KPHI 110159 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 959 PM EDT SUN MAR 10 2013 .SYNOPSIS... HIGH PRESSURE JUST OFF THE COAST WILL CONTINUE TO DRIFT EAST SLOWLY. A COLD FRONT WILL APPROACH FROM THE WEST AND CROSS THE AREA ON TUESDAY. A SECONDARY COLD FRONT FROM THE NORTHWEST WILL CROSS THE AREA AROUND WEDNESDAY, THEN HIGH PRESSURE SHOULD FOLLOW FOR WEDNESDAY NIGHT INTO FRIDAY. ANOTHER COLD FRONT FROM THE NORTHWEST IS FORECAST TO ARRIVE AROUND FRIDAY NIGHT. THE BOUNDARY MAY STALL TO OUR SOUTH DURING THE WEEKEND AS HIGH PRESSURE TRIES TO PUSH DOWN FROM THE NORTHWEST. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... WITH THE LATE EVENING UPDATE, SOME PATCHY FOG WAS ADDED TO THE FCST DURING THE EARLY MORNING HOURS ACROSS PORTIONS OF NORTH- CENTRAL NJ AND SOUTHERN NJ AS WE ANTICIPATE INCREASING LOW-LEVEL MOISTURE WILL GET TRAPPED UNDER A DEVELOPING INVERSION. IN ADDITION, SOME LOW STRATUS MAY ALSO DEVELOP OVER THE REGION, AND WE ADJUSTED THE SKY COVER SOME. HOURLY TEMPS/DEWPOINTS WERE ALSO ADJUSTED TO REFLECT CURRENT TRENDS USING MAINLY THE LAV/LAMP GUIDANCE. OTHERWISE, FAIR WEATHER WILL CONTINUE ACROSS THE AREA TONIGHT AS HIGH PRESSURE MOVES OFF THE COAST AND CONTINUES EASTWARD. SKY COVER WILL BE PARTLY CLOUDY THIS EVENING...BUT THEN MAY GO MOSTLY CLOUDY AS SOME CLOUDS OVER THE OCEAN MAY TRY TO MOVE IN FROM THE EAST. LOW TEMPERATURES WILL DROP INTO THE UPPER 20S TO LOW 30S IN MOST AREAS. WINDS WILL BE LIGHT. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... ANY LINGERING LOW CLOUDS EARLY WILL DIMINISH BY LATE MORNING. THERE WILL BE SCT-BKN AC CLOUDS MUCH OF THE REMAINDER OF THE DAY AS THE NEXT WEATHER SYSTEM WELL TO THE WEST BEGINS TO SEND CLOUDS OUR WAY. HIGH TEMPERATURES MON WILL REACH INTO THE UPPER 50S TO LOW 60S IN MOST AREAS. SOME MID 60S ARE POSSIBLE WELL TO THE SOUTH. WINDS WILL BE LIGHT FROM THE E OR SE. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... THE 12Z DETERMINISTIC GFS AND ECMWF ARE IN DECENT AGREEMENT INTO FRIDAY. THEY START WITH A MID LEVEL LOW MOVING THROUGH THE GREAT LAKES REGION, AND THAT LOW ESTABLISHES ITSELF AS A VORTEX OVER SOUTHEASTERN CANADA. THAT LOW ANCHORS A LONG WAVE TROUGH THAT GIVES VERY LITTLE GROUND FROM WEDNESDAY INTO FRIDAY. AT THE SURFACE, THE FIRST MANIFESTATION OF THE ABOVE IS THE COLD FRONT THAT STILL IS FORECAST TO MOVE ACROSS THE AREA ON TUESDAY. EVERYTHING WE SAW YESTERDAY STILL APPLIES. WE ALSO NOTED THAT THE MODELS (12Z ECMWF, GFS, NAM AND CANADIAN) ALL BRING A LITTLE ELEVATED CAPE EITHER INTO OR CLOSE TO OUR SOUTHERN ZONES, AND THAT WE APPEAR BE UNDER AN UPPER JET COUPLET AROUND 12Z TUESDAY. ALSO, THE H925 JET, THE AXIS OF WHICH RUNS FROM NORTHEASTERN NJ THROUGH THE DELMARVA AT 12Z TUESDAY, IS FORECAST TO RANGE FROM ABOUT 45 TO 55 KNOTS. WE ADDED A SLIGHT CHANCE OF THUNDER TO THE SOUTHERN ZONES. THERE IS A GREAT DEAL OF SHEAR, BUT THE CAPE IS REMOVED FROM THE SURFACE. WE EXPECT SOME TURBULENT MIXING TO OCCUR BEGINNING AHEAD OF THE FRONT LATER MONDAY NIGHT BECAUSE OF THE MAGNITUDE OF THE LOW LEVEL JET. THAT WOULD ALLOW FOR A NOTICEABLE SOUTHERLY BREEZE DESPITE THE STABLE NATURE OF THE SOUNDINGS NEAR THE SURFACE. WE THEREFORE CARRY A NON-DIURNAL TREND TO THE MONDAY NIGHT MINIMUM TEMPERATURES, WHICH ARE AT THE VERY HIGH END OF STAT GUIDANCE EVERYWHERE EXCEPT FOR THE MOST SHELTERED LOCATIONS. WINDS DIE OFF SOME BEHIND THE FIRST FRONT, THEN THE SECOND MANIFESTATION OF THE MID LEVEL VORTEX COMES THROUGH AS A REINFORCING COLD FRONT ON WEDNESDAY NIGHT. THE MODELS ARE NOT CONFINING Q-VECTOR CONVERGENCE, FRONTOGENESIS OR (ADMITTEDLY MINIMAL) MOISTURE TO THE NORTHERN ZONES ON WEDNESDAY, SO WE CARRY SOME SORT OF LOW CHANCE POP EVERYWHERE. WE CONTINUE TO CONFINE POPS TO THE NORTH ON WEDNESDAY NIGHT. TEMPERATURES ARE A GUIDANCE/CONTINUITY BLEND. WINDS PICK UP ONCE AGAIN WITH THE PASSAGE OF THE SECONDARY FRONT. THURSDAY INTO FRIDAY STILL LOOK DRY. WE USED THE WARMER ECMWF H925 TEMPERATURES (VIS-A-VIS THE GFS) TO ARRIVE AT SOME CHILLY TEMPERATURES AND HAVE GONE WITH THEM. BY LATE FRIDAY, THE MODELS CONTINUE TO DIVERGE ON THE STRENGTH OF SOME ENERGY THAT REVOLVES AROUND THE VORTEX AND INTO OUR AREA. THE ECMWF STILL DOWNPLAYS IT, AND THE GFS STILL BRINGS IN SOME PRECIPITATION LATE FRIDAY INTO FRIDAY NIGHT. WE HAVE TAKEN A 60/40 WEIGHT OF THE EMCWF AND GFS STAT GUIDANCE POPS AND FOUND THEY MAINTAIN CONTINUITY WITH THE PREVIOUS FORECAST, AND SO HAVE WE. AFTER THAT, AGREEMENT BETWEEN THE MODELS RAPIDLY BREAKS DOWN FROM WEST TO EAST, AND WE MAINTAIN CONTINUITY. THE ECMWF WOULD HAVE A PRECIPITATION EVENT AROUND SUNDAY WITH ANOTHER ON TUESDAY. THE LATTER COMES COMPLETE WITH A ROBUST CUTOFF LOW TO OUR SOUTH, WHICH IS NOT DEMONSTRATING GOOD RUN-TO-RUN CONTINUITY. THE GFS HAS A RIDGE WHERE THE ECMWF HAS THE CUTOFF. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THROUGH THE FIRST PART OF TONIGHT, VFR CONDITIONS WILL CONTINUE. WITH ONLY SCT TO PERHAPS BKN HIGH CLOUDS OVER THE REGION, SOME GUIDANCE INDICATES INCREASING LOW-LEVEL MOISTURE MAY GET TRAPPED UNDER A DEVELOPING INVERSION, LEADING TO SOME LOW STRATUS OR FOG. AS WE HAVE ONLY MODEST CONFIDENCE AT THIS TIME, WE GENERALLY LOWERED CONDITIONS TO MVFR DURING THE EARLY MORNING HOURS AT MOST OF THE TAF SITES, WITH THE LOWEST CONDITIONS EXPECTED FOR KACY AND KMIV. THESE SITES MAY LOWER FOR A TIME TO IFR. SLOW IMPROVEMENT IS THEN EXPECTED FOR ALL AREAS AFTER DAYBREAK MONDAY, WITH MOST SITES RETURNING TO VFR BY MID-MORNING. WINDS WILL REMAIN LIGHT FROM THE SOUTHEAST TONIGHT. WINDS WILL SHIFT MORE SRLY ON MONDAY. VFR SHOULD CONTINUE THROUGH THE REMAINDER OF MONDAY WITH MOSTLY BKN AC/AS CLOUDS THROUGH THE DAY. OUTLOOK... MONDAY NIGHT...STARTING VFR WITH DETERIORATING CONDITIONS AS SHOWERS SPREAD INTO OUR REGION FROM THE WEST. ALSO, LOW CLOUDS FROM THE OCEAN MAY DRIFT INLAND AT THAT TIME. LOW LEVEL WIND SHEAR MAY BECOME A CONCERN. CONFIDENCE IS MODERATE. TUESDAY...MVFR AND IFR CONDITIONS WITH RAIN SHOWERS BECOMING MODERATE TO HEAVY AT TIMES. LOW LEVEL WIND SHEAR MAY BE A CONCERN EARLY. CONFIDENCE IS MODERATE. TUESDAY NIGHT THROUGH FRIDAY...MAINLY VFR. A FAIRLY BRISK NORTHWEST FLOW CENTERED AROUND THURSDAY IS POSSIBLE. CONFIDENCE IS MODERATE. && .MARINE... WINDS WILL REMAIN MOSTLY E OR SE TONIGHT WITH HIGH PRESSURE MOVING E OF THE WATERS. WIND SPEEDS WILL BE MOSTLY 5 TO 10 KTS. SEAS WILL REMAIN ELEVATED IN A SWELL ASSD WITH THE SYSTEM WELL E OF THE WATERS. THE SCA FLAG WILL REMAIN IN PLACE TONIGHT AND MONDAY. OUTLOOK... THE SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS LIKELY WILL TRANSFORM INTO A GENERAL SMALL CRAFT ADVISORY BY DAYBREAK TUESDAY, AND IT LIKELY WILL BE EXTENDED INTO TUESDAY NIGHT. IF WE MIX DOWN 55 PERCENT OF THE H925 WIND OFF THE MOST ROBUST MODEL (THE GFS), WE WOULD HAVE SOME GUSTS APPROACHING GALE FORCE. WE DEEM THIS POSSIBLE BUT UNLIKELY, BECAUSE THE MARINE LAYER SHOULD BE PRETTY STRONG. WE ARE CONFINING MENTION OF ANY GALE FORCE GUSTS TO THIS DISCUSSION. AFTER TUESDAY NIGHT, WE WILL BE HARD-PRESSED TO CARVE OUT A 24 HOUR PERIOD WITHOUT AN ADVISORY THROUGH FRIDAY. && .TIDES/COASTAL FLOODING... WATER LEVELS FELL SHORT OF REACHING MINOR TIDAL FLOODING WITH THIS AFTERNOONS HIGH TIDE AT TOLCHESTER BEACH, AND DEPARTURES ARE CONTINUING TO SLOWLY FALL THERE. WE THEREFORE CANCELLED THE COASTAL FLOOD ADVISORY FOR THE UPPER EASTERN SHORE OF CHESAPEAKE BAY, NAMELY CECIL AND KENT COUNTIES. ELSEWHERE FOR QUEEN ANNES, TALBOT, AND CAROLINE COUNTIES, DEPERATURES ARE STILL ELEVATED ENOUGH TO WARRANT KEEPING THE COASTAL FLOOD ADVISORY IN PLACE THROUGH MONDAY MORNING. ELSEWHERE, CF.A FLAGS FOR THE NJ/DE OCEAN AND THE DEL BAY/RIVER ARE NOT EXPECTED WITH THE DEPARTURES CONTINUING TO DECREASE TONIGHT AND MONDAY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...COASTAL FLOOD ADVISORY UNTIL NOON EDT MONDAY FOR MDZ015-019- 020. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT TUESDAY FOR ANZ450>455. && $$ SYNOPSIS...DELISI/IOVINO NEAR TERM...KLINE/O'HARA SHORT TERM...O'HARA LONG TERM...DELISI AVIATION...DELISI/KLINE/O'HARA MARINE...DELISI/O'HARA TIDES/COASTAL FLOODING...O'HARA/KLINE