AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 410 PM EDT WED MAY 11 2011 .SYNOPSIS... AN OCEAN STORM WELL OFFSHORE WILL BRING GUSTY NORTHEAST WINDS... AREAS OF DRIZZLE AND UNSEASONABLY COOL TEMPERATURES TO EASTERN MASSACHUSETTS AND RHODE ISLAND THROUGH TONIGHT WITH SLOW IMPROVEMENT THURSDAY. WEAKENING HIGH PRESSURE WILL BUILD ACROSS THE REGION THURSDAY NIGHT THROUGH FRIDAY WITH DRY AND SEASONABLE CONDITIONS. A WEAK BACK DOOR FRONT WILL CROSS THE AREA SATURDAY WITH SOME SHOWERS POSSIBLE. AN UNSETTLED PATTERN WILL CONTINUE INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... INTERESTING FEATURES SEEN ON LATEST VISIBLE SATELLITE IMAGERY WITH A BREAK IN THE CLOUD COVER OVER COASTAL ME AND EXTENDING JUST OFFSHORE INTO MA BAY. THIS AREA OF CLEARING WAS SLIDING TOWARD EASTERN MA AT EARLY AFTERNOON. APPEARS THIS AREA OF CLEARING IS ASSOCIATED WITH SUBSIDENCE SANDWICHED BETWEEN TWO VORT LOBES...ONE OVER NEW ENGLAND AND THE OTHER MOVING ACROSS NOVA SCOTIA. IN ADDITION A STRONG JET STREAK IS ASSOCIATED WITH THE NEW ENGLAND VORT LOBE WITH ITS REAR LEFT QUAD OVER COASTAL ME AND JUST OFFSHORE...ENHANCING THE SUBSIDENCE ACROSS THIS AREA. BOTH THE 12Z NAM AND GFS BUFKIT SUGGEST THIS AREA OF CLEARING WILL OVERSPREAD EASTERN MA AND POSSIBLY INTO RI THIS AFTERNOON AND EVENING. ALTHOUGH AREAL COVERAGE OF CLEARING IS TRICKY AS MOIST NE FLOW SHOULD YIELD CLOUDS JUST INLAND FROM THE COAST GIVEN MOIST UPSLOPE COMPONENT ESPECIALLY INTO THE WORCESTER HILLS. THEREFORE HIGHEST PROBABILITY OF ANY PARTIAL CLEARING/SUNSHINE SHOULD BE ACROSS NORTHEAST MA. CLOUDS SHOULD REMAIN ENTRENCHED ALONG WITH SOME LIGHT RAIN/DRIZZLE ACROSS SOUTHEAST MA AS STRONG LOW LEVEL NE JET MOVES ACROSS THIS AREA LATER THIS AFTERNOON INTO THE EARLY EVENING. THIS AREA OF WET WEATHER MAY EXTEND INTO SE RI LATER THIS AFTERNOON AND EARLY EVENING. FARTHER WEST ACROSS THE CT RVR VLY CLOUDS SHOULD CONTINUE TO SLOWLY LIFT ALONG WITH A FEW BREAKS IN THE OVERCAST. GIVEN THE STRENGTH OF THIS LOW LEVEL JET AND BOUNDARY LAYER MIXING WILL CONTINUE WITH WIND ADVISORY ACROSS NANTUCKET AND KEEP SPEEDS JUST BELOW ADVISORY ACROSS CAPE COD AS ALL MODEL DATA SUPPORTS THIS AT THE MOMENT. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... THURSDAY... THIS WILL BE OUR TRANSITION DAY AS OCCLUDED LOW OFFSHORE BEGINS TO DRIFT FARTHER SEAWARD WITH MID LEVEL FLOW TRANSITIONING SLOWLY FROM CYCLONIC TO ANTICYCLONIC WITH MODELS VARYING ON SPEED OF TRANSITION. HOWEVER SUBSIDENCE INVERSION WILL LIKELY TRAP LOW LEVEL MOISTURE IN THE FORM OF LOW CLOUDS DURING THE MORNING HOURS BUT SHOULD LIFT AND ERODE SOMEWHAT DURING THE AFTERNOON YIELDING PARTIAL SUNSHINE FOR MOST OF THE AREA EXCEPT CAPE COD AND THE ISLANDS WHERE CLOUDS MAY REMAIN DOMINATE. NAM AND GFS BUFKIT SHOW THIS NICELY. AS FOR TEMPS SIDED WITH THE WARMER GFS MOS GIVEN THE EXPECTED PARTIAL SUNSHINE FOR MOST OF THE AREA THU AFTERNOON. WINDS WILL FINALLY SLACKEN TOMORROW ESPECIALLY AWAY FROM THE CAPE AND ISLANDS AS PRES GRADIENT RELAXES. THU NIGHT... QUIET WEATHER AS DEEP LAYER RIDGE WEST OF NEW ENGLAND BUILDS CLOSER TO THE AREA. EXPECTING MOSTLY CLEAR SKIES...LIGHT WINDS AND SEASONABLY COOL TEMPS. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... * DRY AND SEASONABLE CONDITIONS FRIDAY * MORE UNSETTLED WEATHER EXPECTED THIS WEEKEND AND INTO NEXT WEEK MODEL PREFERENCE... GOOD AGREEMENT AMONGST THE MODELS THROUGH SATURDAY WITH A FEW MORE SIGNIFICANT DIFFERENCES SUNDAY AND MONDAY. BY THE TIME WE REACH TUESDAY AND WEDNESDAY THERE ARE VERY DIFFERENT SOLUTIONS AMONG THE MODELS. GENERALLY SPEAKING WE WILL HAVE HIGH PRESSURE OVER THE REGION FRIDAY WITH THE POTENTIAL FOR A WEAK BACK DOOR FRONT MOVING ACROSS THE AREA SATURDAY. MOISTURE WITH THIS FRONT IS LACKING SO NOT EXPECTING A LOT OF RAIN WITH THIS FRONT...BUT COULD SEE SOME LIGHT SHOWERS FROM TIME TO TIME. SUNDAY AND MONDAY...HIGH PRESSURE MOVES OFFSHORE WHILE LOW PRESSURE IN THE GREAT LAKES/OH VALLEY APPROACHES THE AREA BUT THEN MOVES SOUTHWARD INTO THE SOUTHEAST CONUS. MODEL DIFFERENCES LAY IN HOW CLOSE THIS LOW PRES GETS TO SNE. WILL USE A BLEND OF THE ECMWF/GFS OR THE HPC GUIDANCE FOR THIS TIME PERIOD. TUESDAY AND WEDNESDAY IS WHEN WE SEE THE GREATEST DIFFERENCES BETWEEN THE MODELS. THE ECMWF TAKES THE LOW IN THE SOUTHEAST CONUS AND MOVES IT BACK UP INTO THE GREAT LAKES/OHIO VALLEY REGION WITH HIGH PRESSURE BUILDING ALONG THE COAST. MEANWHILE...THE GFS TAKES THE LOW AND MOVES IT UP THE COAST REACHING THE NJ COAST BY WEDNESDAY NIGHT. GIVEN THESE DIFFERENCES AND LOW CONFIDENCE IN ANY ONE SOLUTION...WILL STICK CLOSE TO WHAT WE ALREADY HAVE IN THE FORECAST. DETAILS... FRIDAY...HIGH PRESSURE BUILDS OVER THE REGION WITH EASTERLY WINDS ACROSS THE AREA. THIS ONSHORE FLOW WILL KEEP THE IMMEDIATE COAST COOL AND CLOUDY WHILE THE WARMEST TEMPERATURES WILL OCCUR INLAND ACROSS THE CONNECTICUT RIVER VALLEY. SATURDAY...A WEAK BACKDOOR FRONT WILL MOVE SOUTHWESTWARD ACROSS THE AREA. NOT A LOT OF PRECIPITATION IS EXPECTED WITH THIS FRONT...BUT IT CANNOT BE RULED OUT EITHER. WILL KEEP SLIGHT CHANCE POPS IN FOR THIS PERIOD TO ACCOUNT FOR THIS. OTHERWISE SLIGHTLY COOLER THAN NORMAL TEMPERATURES EXPECTED. SUNDAY THROUGH MONDAY...EASTERLY FLOW CONTINUES TO AFFECT SOUTHERN NEW ENGLAND AS LOW PRESSURE APPROACHES THE AREA AND HIGH PRESSURE MOVES OFFSHORE. COUPLED WITH WARM AIR ADVECTION...MORE RAIN IS EXPECTED...AND ALONG WITH IT MOSTLY CLOUDY TO OVERCAST SKIES. THIS LOW PRESSURE IS PROGGED TO MOVE SOUTHWARD INTO THE SOUTHEAST CONUS BY MONDAY NIGHT. TUESDAY AND WEDNESDAY...LOTS OF DISAGREEMENT AMONGST THE MODELS FOR THIS PERIOD. BEST FORECAST IS FOR MORE UNSETTLED WEATHER...WITH PRECIP AND CLOUDS FORECAST BY BOTH THE ECMWF AND THE GFS THOUGH THE DRIVING FORCES BEHIND SUCH WEATHER ARE A BIT DIFFERENT. CONTINUED WAA AND LOW PRES APPROACHING FROM THE OH VALLEY FOR THE ECMWF AND LOW PRESSURE MOVING UP THE COAST ON THE GFS. A LOW CONFIDENCE FORECAST FOR THIS TIME PERIOD TO BE SURE. && .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT MODERATE...30 PERCENT TO 60 PERCENT HIGH...GREATER THAN 60 PERCENT THROUGH 00Z... LOW CONFIDENCE FORECAST ON DETAILS BUT MODERATE TO HIGH CONFIDENCE ON TRENDS. CIGS WILL CONTINUE TO LIFT TO MVFR FOR MUCH OF THE REGION WITH VFR ACROSS WESTERN NEW ENGLAND...BUT ALSO ACROSS EXTREME EASTERN MA. THIS IMPROVING TREND WILL CONTINUE INTO THIS EVENING ALTHOUGH EXACT TIMING IS DIFFICULT. OTHER THAN SOME SPOTTY LIGHT DRIZZLE EARLY THIS AFTERNOON EXPECT MAINLY DRY RUNWAYS. LLWS POSSIBLE CAPE COD AND THE ISLANDS AS LOW LEVEL NE JET MOVES ACROSS THE AREA. AFTER 00Z... MVFR TO VFR CONDITIONS MUCH OF THE NIGHT WITH LOWEST CIGS OVER THE CAPE AND ISLANDS ALONG WITH PATCHY DRIZZLE. LLWS POSSIBLE ACROSS THIS REGION EARLY ON. FORECAST CONFIDENCE MODERATE. KBOS TERMINAL... VFR LIKELY LATE THIS AFTERNOON AND EARLY EVENING BEFORE POSSIBLY GOING BACK TO MVFR LATER THIS EVENING. DRY RUNWAYS SHOULD PREVAIL ALONG WITH A MODEST N-NE WIND. MVFR CIGS EARLY THU SHOULD BECOME VFR BY AFTN AND CONTINUE THU NIGHT. WINDS SLACKEN THU AS WELL. OUTLOOK...FRIDAY THROUGH MONDAY... FRIDAY...MEDIUM TO HIGH CONFIDENCE. VFR. SATURDAY...MEDIUM TO HIGH CONFIDENCE. MAINLY VFR. LOW PROBABILITY OF MVFR CONDITIONS IN ISOLD -SHRA. SUNDAY AND MONDAY...MEDIUM CONFIDENCE. MAINLY VFR WITH MVFR CONDITIONS OCCURRING IN LIGHT SHOWERS AND FOG. && .MARINE... THIS EVENING AND OVERNIGHT... EXPECT NE GALES TO CONTINUE FOR A GOOD PORTION OF TONIGHT ACROSS THE CAPE COD AND NANTUCKET WATERS...WITH SMALL CRAFT CONDITIONS ELSEWHERE. HAVE UPDATED TO INCREASE SEAS BY 1-2 FT. NOTED HIGHER THAN FORECAST SEAS AT THE BUOYS ESPECIALLY ON THE EASTERN WATERS AT 18Z-19Z. NOTED 8-10 FOOT SEAS AT BUOY 44013 AND 7 FOOTERS AT BOTH BUOY 44029 AND 44098. USED THE SWAN GFS MODEL WHICH SEEMED TO BEST CAPTURE THIS. EXPECT SEAS TO SLOWLY SUBSIDE OVERNIGHT...BUT WILL REMAIN WELL ABOVE 5 FT ESPECIALLY ON THE EASTERN WATERS. THU/THU NIGHT... OFFSHORE LOW MOVES SLOWLY SEAWARD WITH WINDS EASING ACROSS THE EASTERN NEW ENGLAND WATERS. HOWEVER...HAVE EXTENDED THE SMALL CRAFT THROUGH AT LEAST THURSDAY. EXPECT WINDS AND SEAS WILL REMAIN ABOVE SMALL CRAFT CRITERIA THROUGH A GOOD PORTION OF THE DAY. LARGE NE SWELLS WILL ALSO PERSIST. OUTLOOK...FRIDAY THROUGH MONDAY... FRIDAY...SEAS CONTINUE TO SLOWLY DIMINISH THOUGH REMAINING ABOVE 5 FEET ON THE OUTER WATERS. NORTH TO NORTHEASTERLY WINDS BELOW 25 KNOTS. SATURDAY...SEAS CONTINUE TO DIMINISH...FALLING BELOW 5 FEET DURING THE AFTERNOON. NORTHEASTERLY WINDS DIMINISH AND TURN TO THE SOUTHEAST. SUNDAY...SEAS REMAIN BELOW SCA THRESHOLDS DURING THE DAY THEN INCREASE OVERNIGHT. WINDS WILL REMAIN BELOW 25 KTS. MONDAY...SEAS INCREASE THROUGH MONDAY TO 5 TO 8 FEET. SOUTHEASTERLY WINDS REMAIN BELOW 25 KTS. && .TIDES/COASTAL FLOODING... PERSISTENT NORTH TO NORTHEAST WINDS AND LARGE SEAS OVER MULTIPLE TIDE CYCLES WILL RESULT IN SOME BEACH EROSION ON NORTH AND EAST FACING BEACHES ESPECIALLY ON THE OUTER CAPE AND NANTUCKET. SURGE VALUES WILL RANGE BETWEEN 1-1.5 FT /ADDED 0.5 FT TO STORM SURGE GUID/. HOWEVER TIDES REMAIN LOW ENOUGH TO PRECLUDE ANY COASTAL FLOODING. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...WIND ADVISORY UNTIL 7 PM EDT THIS EVENING FOR MAZ024. NH...NONE. RI...NONE. MARINE...GALE WARNING UNTIL 3 AM EDT THURSDAY FOR ANZ232-254-255. SMALL CRAFT ADVISORY UNTIL 6 PM EDT THURSDAY FOR ANZ231- 233>235-237-250-251-256. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ230- 236. && $$ SYNOPSIS...NOCERA/RLG