FXUS61 KPHI 200732 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 330 AM EDT SAT SEP 20 2008 .SYNOPSIS... A HIGH PRESSURE RIDGE EXTENDING SOUTHWESTWARD FROM THE NEW ENGLAND COASTAL WATERS WILL SLOWLY SLIDE TO THE EAST TODAY AND SUNDAY. A COLD FRONT APPROACHING THE NORTHERN GREAT LAKES TODAY WILL MOVE SLOWLY SOUTHEAST AND PASS THROUGH THE REGION AROUND SUNDAY EVENING. ANOTHER HIGH PRESSURE SYSTEM WILL BUILD SOUTHEAST FROM CENTRAL CANADA AND REACH NEW ENGLAND BY TUESDAY BEFORE ONLY SLOWLY EDGING OFFSHORE IN THE MIDDLE OF THE WEEK. A LOW PRESSURE SYSTEM IS THEN EXPECTED TO FORM OFF THE SOUTHEAST COAST THURSDAY AND SLOWLY MOVE NORTHEAST. && .NEAR TERM /THROUGH TODAY/... THE GFS INITIALIZATION LOOKED SLIGHTLY BETTER THAN THE WRF-NMM. BOTH MODELS WERE A BIT TOO WARM WITH THE CORE OF THIS AUTUMNAL AIR MASS. GIVEN THE GEOGRAPHIC AREA THAT THE NEXT FRONT HAS TO COVER WE LIKE THE GFS SOLUTION SINCE ITS A BIT SLOWER WITH THE TIMING. THIS IS ONE TIME WHERE WE WILL GO A BIT MORE PESSIMISTIC THAN MOS CLOUD GUIDANCE FOR TODAY AS LATEST SATL IMAGERY IS SHOWING PLENTY OF SC OVER AND EAST OF OUR CWA. MODEL GUIDANCE FCST WINDS AT 925MB CONTINUE TO ADVECT THESE CLOUDS TWD THE W. IN ADDITION AS THE 500MB FLOW RESUMES A MORE NORMAL FROM THE W ORIENTATION, CIRRUS HAS ARRIVED WITH MORE HEADING OUR WAY. WE WILL CONT THE WORDING OF A MOCLDY MORNING FOR COASTAL AREAS WITH IPVG CONDITIONS FOR THE AFTN BASED ON THE EVOLUTION OF THE FCST 925MB MOISTURE. TAKING IT A STEP FURTHER THE GFS BRINGS IN SOME LIGHT PCPN WHILE THE WRF-NMM BRINGS PCPN FROM A DEVELOPING OFSHR LOW TO THE DE COAST. FCST SOUNDINGS DO NOT SUPPORT THE FORMER AND THE SREF MEAN DOES NOT SUPPORT THE LATTER. AS THE ONSHR FLOW WEAKENS, THE SC SHOULD START TO DISSIPATE, BUT WE NOW HAVE A COMPARABLE WEAKER MARCH SUN OUT THERE AND THE SC WILL NOT GO EASY. THUS WE FAVOR COMPROMISING TOWARD THE LOWER ETA MOS FOR MAX TEMPS. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... WHILE THE ONSHORE FLOW WEAKENS TONIGHT, A SHORT WAVE IS FORECAST TO MOVE THRU OUR CWA IN THE RE-ESTABLISHED SW FLOW. THERE IS PLENTY OF CIRRUS UPWIND SO IT IS NOT DISCOUNTED. WAY BACK WHEN THIS WOULD BE A FAIR NIGHT, NOW WE WILL HEDGE TOWARD THE MOSTLY CLEAR SIDE. GFS MOS LOOKS BETTER FOR THE MINS AS IT BRINGS THEM CLOSER TO THE CURRENT AND EXPECTED DEW POINTS. COLD FRONT FCST TO BE APPROACHING OUR CWA ON SUNDAY. THE GFS DOES FCST A NARROW AXIS OF INSTABILITY WITH THIS FRONT NORTH OF OUR CWA. ATTM THE SO-CALLED PRECIP THREAT LOOKS HIGHER SUNDAY NIGHT THAN MONDAY FOR OUR CWA. THE GFS FCSTS THE NRN PART OF OUR CWA TO BE IN THE ENTRANCE REGION OF THE H2.5 JET. WE ARE SEEING FAIRLY HIGH TOTAL TOTALS FCST WITHOUT THE ASSISTANCE OF OUTRAGEOUS FCST H8 DEW POINTS. THERE IS ALSO SOME FCST WEAK WAA FCST AS WELL AS LLVL THETA E CONVERGENCE. MOST OF THIS THOUGH IS OCCURRING FARTHER TO THE NORTH AND THE INITIAL SURGE SHOULD BE ON THE DOWN SIDE AS IT APCHS OUR CWA. SO WE WILL LOWER POPS TO SLGT CHC AND REMOVE THEM FARTHER TO THE SOUTH WHERE THE ISSUE IS MORE OF A MONDAY DAY ONE. OTHERWISE WITH LESS OF AN ONSHR FLOW TEMPS SUNDAY WILL REBOUND. UPWIND OBSERVED 1000-850MB THICKNESSES OF 1400 HAVE BEEN PRODUCING LOWER 80S, WE GET TO 1392, SO THIS SUGGESTS TAKING ABOUT A CAT OFF OF GFS MOS FOR MAX TEMPS. && .LONG TERM /MONDAY THROUGH FRIDAY/... ANOTHER HIGH PRESSURE SYSTEM IS FORECAST TO TRACK ACROSS NEW ENGLAND THROUGH THURSDAY, BUT STILL EXTEND OVER THE REGION. WITHOUT ANY DYNAMICS ALOFT, THIS SHOULD MEAN MAINLY DRY WEATHER. THE GFS IS FORECASTING SOME LIGHT SHOWERS TO DEVELOP ON MONDAY ACROSS OUR ENTIRE CWA. BUT THIS IS BASED ON DEW POINTS RISING INTO THE MID 60S IN THE SOUTH. WE JUST DO NOT BELIEVE WILL OCCUR. IN ADDITION THE FORECAST SUPPORT WE SEE FOR SHRAS NORTH OF OUR CWA ON SUNDAY DAY IS NOT EXPECTED TO BE THERE ON MONDAY. WE HAVE LIMITED ANY MENTION TO THE FAR N WHERE CONSENSUS CURRENTLY EXISTS WITH THE ECMWF AND CAN GGEM. OTHERWISE ONSHORE FLOW SOUTH SHOULD ALLOW FOR PC SKIES SOUTH, BUT CONSIDERING THE POSITION OF THE HIGH, IT SHOULD BE MOSTLY CLEAR/MOSTLY SUNNY NORTH INTO THURSDAY. THEN THE HIGH IS FORECAST TO RETREAT ENOUGH ON FRIDAY TO ALLOW A NORTHWARD SHIFT OF THE ONSHORE FLOW AS LOW PRESSURE FORMS EAST OF FLORIDA AND THEN HEADS SLOWLY TO THE NORTHEAST. THE ONSHORE FLOW AND EVENTUALLY THE LOW WELL TO THE SOUTHEAST SHOULD ALLOW MOISTURE TO SPREAD INTO THE AREA WITH A THREAT OF RAIN ON FRIDAY IF THE LOW CAN COME CLOSE ENOUGH TO OUR CWA. THE LATEST ECMWF IS BACKING AWAY FROM SOME OF ITS PREVIOUS MORE AGGRESSIVE SOLUTIONS. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... A STRONG AREA OF HIGH PRESSURE LOCATED OVER NEW ENGLAND THIS MORNING WILL GRADUALLY SLIDE EASTWARD AND WEAKEN THROUGH TODAY. THIS HOWEVER WILL MAINTAIN A GENERAL ONSHORE FLOW ACROSS OUR AREA BUT SHOULD BE A BIT LIGHTER THAN YESTERDAY. THERE HAS BEEN A DECENT AMOUNT OF STRATOCUMULUS OVER THE OCEAN AND SOME OF THIS HAS MADE IT ONSHORE. IT HAS TENDED TO THIN OUT SOME AS IT MOVED INLAND, HOWEVER WITH LOW-LEVEL SATURATION BECOMING MAXIMIZED ESPECIALLY AROUND DAYBREAK, WE ARE EXPECTING SOME MORE OF THE STRATOCUMULUS TO HOLD TOGETHER AND SLIDE FARTHER INLAND. WE ARE EXPECTING CEILINGS TO REMAIN VFR HOWEVER WE DID GO WITH A TEMPO GROUP AT KMIV AND KACY FOR MVFR CEILINGS THROUGH ABOUT 12Z. THESE TWO TERMINALS SHOULD HAVE THE GREATER COVERAGE OF LOWER CLOUDS GIVEN THE MOISTURE WORKING ITS WAY INLAND. ELSEWHERE, A TOUCH OF STRATOCUMULUS AROUND THIS MORNING. KABE AND KRDG SHOULD HAVE LESS STRATOCUMULUS GIVEN THE LIGHTER GRADIENT HERE AND THE TRAJECTORY. THE MOISTURE APPEARS TO BE RATHER SHALLOW IN NATURE, THEREFORE WE ARE NOT ANTICIPATING ANY DRIZZLE OR SPRINKLES. AS DAYTIME HEATING GETS GOING, THE CEILINGS ARE EXPECTED TO LIFT SOME HOWEVER WE SHOULD GET SOME FILLING IN OF THE STRATOCUMULUS FOR A TIME. OUR CONFIDENCE IS LOWER REGARDING THE TRUE COVERAGE OF CLOUDS TODAY GIVEN THE WEAKENING OF THE PRESSURE GRADIENT OVER TIME. THERE IS SOME CIRRUS APPROACHING FROM OUR IMMEDIATE WEST AND IF THIS MOVES ACROSS THE AREA IT COULD HAVE AN IMPACT ON THE INTERACTION OF SURFACE HEATING AND STRATOCUMULUS DEVELOPMENT/DISSIPATION. THE MODEL GUIDANCE IS NOT AS ROBUST WITH CLOUD COVER THE FURTHER WEST ONE GOES, THEREFORE KACY AND KMIV MAY HAVE MUCH MORE STRATOCUMULUS WHILE KABE AND KRDG MIGHT JUST SEE MID TO HIGH LEVEL MOISTURE. THE NORTHEASTERLY WINDS WILL CONTINUE TODAY AND STRENGTHEN SOME AFTER SUNRISE, WITH THE STRONGEST SPEEDS PROBABLY AT KACY. THE SURFACE WINDS MAY TEND TO SHIFT TO THE SOUTHEAST AT SOME TERMINALS THIS AFTERNOON AS THE OVERALL PRESSURE GRADIENT RELAXES. ANY STRATOCUMULUS SHOULD DISSIPATE THIS EVENING AS THE ONSHORE FLOW WEAKENS EVEN SOME MORE. AS OF NOW, WE ARE NOT ANTICIPATING ANY FOG TONIGHT. OUTLOOK... A WEAK COLD FRONT IS EXPECTED TO MOVE THROUGH SUNDAY EVENING. WHILE A SHOWER CANNOT BE RULED OUT, ESPECIALLY THE FARTHER NORTH, IT LOOKS RATHER ISOLATED. ANOTHER AREA OF HIGH PRESSURE WILL THEN BUILD TO OUR NORTH MONDAY AND TUESDAY. INTERESTINGLY ENOUGH, SOME MODEL GUIDANCE TRIES TO DEVELOP SOME SHOWERS ON MONDAY AS THE ONSHORE FLOW STRENGTHENS. THE AFOREMENTIONED HIGH MAY BEGIN TO WEAKEN SOME ON WEDNESDAY. GIVEN THE POSITION OF THIS LARGE HIGH TO OUR NORTH EARLY NEXT WEEK, THE ASSOCIATED ONSHORE FLOW MAY PRODUCE STRATOCUMULUS AND PERHAPS POCKETS OF FOG. && .MARINE... AN AREA OF HIGH PRESSURE TO OUR NORTH WILL GRADUALLY WEAKEN THROUGH TODAY. HOWEVER, THE LOW-LEVEL FLOW WILL CONTINUE TO BE FROM A NORTHEASTERLY DIRECTION WITH THE LONGER FETCH AIMED AT OUR SOUTHERN WATERS. THE SEAS HAVE BEEN AROUND 9 FEET AT BUOY 44009, WHICH HAS BEEN WITHIN A FOOT OF THE 00Z WAVEWATCH GUIDANCE. DESPITE THE WEAKENING PRESSURE GRADIENT THROUGH TODAY, IT WILL TAKE SOME TIME FOR THE SEAS TO SUBSIDE BELOW 5 FEET. AS A RESULT, WE WILL CONTINUE THE SMALL CRAFT ADVISORY ON THE OCEAN THROUGH SUNDAY AFTERNOON. THE WIND GUSTS HAVE BEEN NEARING 25 KNOTS MAINLY OVER OUR SOUTHERN WATERS, AGAIN DUE TO A LONGER FETCH. AS THE HIGH WEAKENS AND MOVES FARTHER TO THE EAST, WE MAY BE ABLE TO GET SEAS BELOW 5 FEET FOR A TIME SUNDAY EVENING INTO MONDAY. A WEAK COLD FRONT THOUGH WILL CROSS THE WATERS SUNDAY NIGHT, WITH A LARGE AREA OF HIGH PRESSURE BUILDING ONCE AGAIN TO OUR NORTH. THIS HIGH WILL ESTABLISH A TIGHTENING PRESSURE GRADIENT, WHICH WILL ALLOW THE WINDS TO INCREASE AGAIN FROM A NORTHEASTERLY DIRECTION. THIS WILL BUILD SEAS BACK UP MONDAY NIGHT THROUGH WEDNESDAY TO HEIGHTS SIMILAR TO WHAT WE ARE CURRENTLY SEEING. WHILE SOME HIGHER SEAS WILL AFFECT THE MOUTH OF DELAWARE BAY EARLY NEXT WEEK, IT IS UNCERTAIN IF WE CAN GET 25 KNOT WINDS TO OCCUR THERE AS WELL. THIS WILL ALL SPELL FOR ANOTHER TIME FRAME THAT A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED FOR AT LEAST THE OCEAN ZONES. RIP CURRENT... HIGH PRESSURE REMAINS LOCATED TO OUR NORTH, ALTHOUGH GRADUALLY WEAKENING TODAY, WILL CONTINUE TO PRODUCE AND ONSHORE FLOW. UTILIZING OUR INHOUSE TOOLS, WE CAME UP WITH A HIGH END OF MODERATE TO HIGH RISK OF RIP CURRENTS FOR TODAY GIVEN THE HIGH SEAS, ONSHORE FLOW AND DOMINATE WAVE PERIOD. THE WAVE HEIGHTS NEARSHORE ARE RUNNING ABOUT 4 TO 5 FEET WITH A DOMINATE PERIOD OF ABOUT 10 SECONDS. AS OF NOW, WE WILL GO WITH A HIGH RISK OF RIP CURRENTS THROUGH TODAY. SINCE MANY AREA BEACHES ARE NO LONGER STAFFED WITH LIFE GUARDS, IT MIGHT BE BEST TO STAY OUT OF THE WATER TODAY. && .TIDES/COASTAL FLOODING... AN ONSHORE FLOW WILL BE MAINTAINED TODAY, HOWEVER AN OVERALL DIMINISHING TREND IS EXPECTED AS THE PRESSURE GRADIENT RELAXES. WE ARE STILL SEEING THE TIDAL DEPARTURES RUNNING ABOUT 0.5 TO 1.0 FEET ABOVE NORMAL ALONG THE COAST WITH A LITTLE OVER A FOOT UP DELAWARE BAY AND INTO THE DELAWARE RIVER. THE ASTRONOMICAL TIDES WILL BE LOWERING TODAY, HOWEVER GIVEN THAT THE 06Z DEPARTURES WERE RUNNING ABOVE THE GFS GUIDANCE AND A LITTLE UNDER THE NGM GUIDANCE COUPLED WITH STILL AN ONSHORE TRAJECTORY, WE ARE ANTICIPATING A FAIRLY SIMILAR TIDAL TREND COMPARED TO YESTERDAY. AS A RESULT, WE WILL GO WITH A COASTAL FLOOD ADVISORY FOR THE OCEAN AREAS TO COVER TODAY'S HIGH TIDE, WHICH IS CENTERED AROUND THE NOON HOUR FOR MOST PLACES. ELSEWHERE, LEVELS FOR MINOR TIDAL FLOODING ARE NOT EXPECTED TO BE ACHIEVED TODAY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...COASTAL FLOOD ADVISORY FROM 11 AM THIS MORNING TO 3 PM EDT THIS AFTERNOON FOR NJZ013-014-020-022>027. DE...COASTAL FLOOD ADVISORY FROM 11 AM THIS MORNING TO 3 PM EDT THIS AFTERNOON FOR DEZ003-004. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT SUNDAY FOR ANZ450>455. && $$ SYNOPSIS...GIGI NEAR TERM...GIGI SHORT TERM...GIGI LONG TERM...STAUBER AND GIGI AVIATION...GORSE MARINE...GORSE RIP CURRENT...GORSE TIDES/COASTAL FLOODING...GORSE