AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 245 AM EDT SAT JUL 9 2011 .SYNOPSIS... SHOWERS AND THUNDERSTORMS WILL CONTINUE PARTICULARLY SOUTH OF THE MASS PIKE THROUGH THIS EVENING. THESE WILL MOVE EAST OF OUR AREA BY SATURDAY MORNING. HIGH PRESSURE THEN BUILDS FAIR AND LESS HUMID AIR OVER NEW ENGLAND FOR THE WEEKEND. A COLD FRONT WILL MOVE SLOWLY THROUGH THE REGION LATE MONDAY THROUGH TUESDAY...BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS. HIGH PRESSURE RETURNS WEDNESDAY INTO THE END OF THE WEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... HEAVIEST RAINFALL CONTINUES TO FALL ACROSS SOUTHEAST MA THIS EVENING. NO MAJOR CHANGES TO FORECAST. DENSE FOG ADVISORY CANCELLED AS VISIBILITY HAS IMPROVED SIGNIFICANTLY WITH ARRIVAL OF HEAVIER RAINFALL AND INCREASED SURFACE FLOW. MADE MINOR TWEAKS TO TEMPERATURES AND DEW POINTS BASED ON LATEST OBSERVATIONS. RAINFALL WINDING DOWN...AND SHOULD MOVE COMPLETELY OFFSHORE SHORTLY AFTER 12Z. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... SATURDAY AND SATURDAY NIGHT... HIGH PRESSURE BUILDS OVER THE REGION. EXPECT DRY WEATHER. 800 MB TEMPS ARE FORECAST AROUND 10-11C...FULLY MIXED THIS WOULD MEAN MAX TEMPS IN THE MID 80S. WE USED A BLEND THAT SHOWS MAX TEMPS IN THE LOW TO MID 80S. DEW POINTS EXPECT TO FALL INTO THE 50S DURING THE DAY...SO NIGHTTIME MIN TEMPS SHOULD REACH THE 50S EXCEPT LOWER 60S IN SOME OF THE LARGER CITIES. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... * COLD FRONT BRINGS SHOWERS AND THUNDERSTORMS MON AFTN THROUGH TUE * HIGH PRESSURE MOVES IN BEHIND FOR THE REST OF THE WEEK MODEL PREFERENCES... BETTER THAN AVERAGE MODEL AGREEMENT THROUGHOUT THE LONG TERM. WE WILL START OFF THE PERIOD WITH HIGH PRESSURE THEN TURN TO A SLOW MOVING COLD FRONT THAT SHOULD MOVE THROUGH SOUTHERN NEW ENGLAND LATE MONDAY INTO TUESDAY. THERE ARE SOME SLIGHT TIMING DISCREPANCIES ASSOCIATED WITH THE COLD FRONT WITH THE 00Z ECMWF MOVING IT INTO THE AREA A FEW HOURS EARLIER THAN THE 12Z GFS. BOTH MODELS HAVE THE FRONT MOVING OFFSHORE BY 06Z WEDNESDAY. THIS FRONT WILL LIKELY BRING SHOWERS AND THUNDERSTORMS TO THE REGION. AFTER THE COLD FRONT MOVES THROUGH...A COOL DAY WEDNESDAY FOLLOWED BY MODERATING TEMPERATURES AND BUILDING HIGH PRESSURE. DETAILS... SUNDAY...QUIET WEATHER WITH HIGH PRESSURE MOVING ACROSS OR JUST SOUTH OF SOUTHERN NEW ENGLAND. MOSTLY SUNNY SKIES EXPECTED WITH MID AND HIGH CLOUDS BUILDING LATE SUNDAY NIGHT AHEAD OF A COLD FRONT. 850MB TEMPS IN THE 13 TO 14C RANGE WITH DECENT MIXING SHOULD YIELD HIGHS AT OR A FEW DEGREES ABOVE NORMAL. MONDAY AND TUESDAY...SHOULD START OUT WITH MOSTLY CLEAR SKIES AND QUIET WEATHER. CLOUDS MOVE IN AND THICKEN DURING THE AFTERNOON AND EVENING HOURS AS THE COLD FRONT NEARS SOUTHERN NEW ENGLAND. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE AHEAD OF THE FRONT WITH DECENT INSTABILITY IN PLACE. LIMITING FACTOR WILL BE THE TIMING OF THE COLD FRONTS APPROACH WITH THE ECMWF BRINGING THE FRONT INTO WESTERN NEW ENGLAND BETWEEN 06 AND 12Z TUESDAY AND THE GFS NOT UNTIL AFTER 12Z TUESDAY. THIS TIMING /PARTICULARLY THE ECMWF TIMING/ WILL LIMIT THE AMOUNT OF INSTABILITY. BELIEVE TUESDAY WILL BE THE MORE LIKELY DAY FOR THUNDERSTORMS WITH THE FRONT MOVING ACROSS MUCH OF THE AREA DURING THE DAY. HOWEVER...THE LIMITING FACTOR HERE WILL BE THE CLOUD COVER THAT IS LIKELY TO BE IN PLACE AHEAD OF THE FRONT TUESDAY. THERE IS CERTAINLY SOME UNCERTAINTY WITH THIS PART OF THE FORECAST. REGARDLESS...THIS PERIOD HAS THE BEST CHANCE OF PRECIPITATION AND WILL CONTINUE CHANCE POPS IN THE FORECAST FOR THIS TIME. WEDNESDAY THROUGH FRIDAY...HIGH PRESSURE BUILDS INTO THE REGION WITH MOSTLY CLEAR TO CLEAR SKIES...QUIET WEATHER...AND TEMPERATURES RIGHT AT OR A FEW DEGREES BELOW NORMAL. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT MODERATE...30 PERCENT TO 60 PERCENT HIGH...GREATER THAN 60 PERCENT THROUGH 12Z...CHAOTIC CONDITIONS EARLY THIS MORNING...RANGING FROM VFR TO VLIFR. VERY DIFFICULT TO NAIL DOWN THE TIMING AT SPECIFIC LOCATIONS. TRENDS ARE VERY CLEAR THOUGH...WITH IMPROVEMENT TO VFR FROM WEST TO EAST STARTING IN EARNEST DURING THE PRE-DAWN HOURS. TODAY AND TONIGHT...HIGH CONFIDENCE VFR MOST LOCATIONS. POSSIBLE LINGERING IFR IN FOG ACROSS CAPE COD AND THE ISLANDS THROUGH MID- MORNING. PATCHY IFR IN FOG COULD REDEVELOP FOR A TIME THIS EVENING NEAR KACK...BUT ONLY MEDIUM CONFIDENCE. KBOS TERMINAL...LOW TO MEDIUM CONFIDENCE IN FIRST 6 HOURS OF TAF. HIGH CONFIDENCE AFTER THEN. OUTLOOK...SUNDAY THROUGH WEDNESDAY... SUNDAY THROUGH MONDAY MORNING...HIGH CONFIDENCE VFR. MONDAY AFTERNOON THROUGH TUESDAY...MEDIUM CONFIDENCE. MAINLY VFR WITH PERIODS OF MVFR/IFR CONDITIONS IN SHOWERS AND THUNDERSTORMS. WEDNESDAY...HIGH CONFIDENCE. VFR. && .MARINE... TONIGHT... WINDS AND SEAS REMAIN BELOW SMALL CRAFT LEVELS. POOR VSBYS FROM DENSE FOG ESPECIALLY AROUND CAPE COD AND THE ISLANDS. TSTMS MAY PRODUCE HEAVY RAIN AND GUSTY WINDS. SATURDAY AND SATURDAY NIGHT... SEAS MAY BUILD TO 5-6 FEET ON THE SOUTHERN WATERS...MOSTLY A SOUTH-SOUTHWEST SWELL. A SMALL CRAFT ADVISORY HAS BEEN ISSUED. OUTLOOK...SUNDAY THROUGH WEDNESDAY... SUNDAY...SEAS ON THE OUTER WATERS AROUND 5 FEET SLOWLY DIMINISH AS HIGH PRESSURE MOVES OVER THE WATERS. MONDAY...WINDS AND SEAS REMAIN BELOW SCA CRITERIA. TUESDAY...SEAS BUILD TO 5 TO 6 FEET ON THE OUTER WATERS WITH GUSTY SOUTHERLY WINDS SHIFTING TO THE WEST DURING THE AFTERNOON/EVENING HOURS AS A COLD FRONT MOVES OVER THE WATERS. WINDS MAY GUST TO NEAR 25 KTS AT TIMES. WEDNESDAY...NORTHWEST WINDS AND SEAS DIMINISH GRADUALLY AS HIGH PRESSURE BUILDS OVER THE WATERS. && .HYDROLOGY... FLASH FLOOD GUIDANCE IS GENERALLY AT 2-3 INCHES PER HOUR AND 3.5 TO 4.5 IN 3 HOURS. NOT EXPECTING FLASH FLOODING TONIGHT BUT COULD BE LOCAL URBAN/SMALL STREAM/POOR DRAINAGE FLOODING IN THESE AREAS IF ADDITIONAL HEAVY DOWNPOURS MOVE ACROSS THIS EVENING AND TONIGHT. HEAVIEST RAINFALL SHIFTING TOWARD CAPE COD AND THE ISLANDS...BUT THERE ARE STILL SEVERAL HOURS TO GO BEFORE THE RAINFALL INTENSITIES REALLY DIMINISH. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 7 AM THIS MORNING TO 5 AM EDT SUNDAY FOR ANZ235-254>256. && $$ SYNOPSIS...WTB/RLG