AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1012 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 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/... 10 PM UPDATE...MINOR UPDATES TO TEMPS/DEWPOINTS AND SKY COVER. OVERALL NO SIGNIFICANT CHANGES TO THE FORECAST. ONSHORE FLOW WILL KEEP CLOUDS ALONG THE MASS EAST COAST THROUGH THE NIGHT ALONG WITH PATCHY DRIZZLE ACROSS THE CAPE/ISLANDS/EXTREME SOUTHEAST. ALSO AN AREA OF CLOUDS OVER THE CT VALLEY AND CENTRAL HILLS WILL SLOWLY THIN OVERNIGHT. && .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 /02Z THURSDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT MODERATE...30 PERCENT TO 60 PERCENT HIGH...GREATER THAN 60 PERCENT TONIGHT...VFR CEILINGS ACROSS WESTERN WILL DIMINISH IN COVERAGE OVERNIGHT. VFR IN THE EAST WITH CEILINGS LOWERING TO MVFR...MAINLY ON THE CAPE/ISLANDS. FORECAST CONFIDENCE MODERATE. THURSDAY...MODERATE TO HIGH CONFIDENCE. MVFR CONDITIONS TO START IMPROVING TO VFR ACROSS THE WESTERN ZONES AND MVFR CONDITIONS THROUGH THE DAY ALONG THE COAST. GUSTY WINDS AT COASTAL TERMINALS. KBOS TERMINAL... VFR EARLY THIS EVENING BEFORE DIMINISHING TO MVFR LATE TONIGHT. 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 AFTN 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... OVERNIGHT...WINDS HAVE DIMINISHED ON BOSTON HARBOR AND NARRAGANSETT BAY...SMALL CRAFT ADVISORY FOR EACH HAS EXPIRED. GALES CONTINUE TO BE OBSERVED SURROUNDING NANTUCKET...AND WITH WINDS AT OR ABOVE 25 KNOTS OVER MOST OF THE REMAINING WATERS. WINDS WILL DIMINISH OVERNIGHT. SEAS WILL SLOWLY SUBSIDE AS THE WINDS DIMINISH. CONTINUE TO EXPECT GALES TO END OVERNIGHT...BUT SMALL CRAFT CONDITIONS SHOULD LINGER THROUGH THE NIGHT. 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...NONE. 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. && $$