Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 031750 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 150 PM EDT SUN MAY 3 2015 .SYNOPSIS... CONDITIONS GRADUALLY WARM INTO MONDAY...WITH A CHANCE FOR A FEW SHOWERS THIS AFTERNOON. HIGH PRESSURE BUILDS OVER THE REGION DURING EARLY NEXT WEEK. A COLD FRONT SWEEPS SOUTH ACROSS THE REGION TUESDAY AND THEN STALLS SOUTH OF NEW ENGLAND MIDWEEK. HIGH PRESSURE REBUILDS WITH DRY AND WARMING WEATHER THE REMAINDER OF THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 145 PM UPDATE... SCATTERED SHOWERS HAVE FORMED IN WESTERN MA AND NORTHERN CT. OTHERS WERE MOVING SOUTH THROUGH SOUTHERN NH. INSTABILITY IS QUITE MARGINAL. A FEW OF THE STRONGER SHOWERS COULD ATTAIN SOME LIGHTNING LATER THIS AFTERNOON. BUT BY EVENING WITH SUNSET...THEY SHOULD BE RAPIDLY DIMINISHING. TEMPERATURES WERE ABOUT AS FORECAST WITH MID AND UPPER 70S IN THE FAR INTERIOR AND MUCH COOLER 50S AND 60S ADJACENT TO BAYS AND THE OCEAN. LOWERED TEMPERATURES IN BOSTON PROPER AS EASTERLY SEA BREEZES HAVE RESTRICTED TEMPERATURES TO NEAR 60 THUS FAR. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... TONIGHT... PRECIP WILL COME TO AN END FAIRLY RAPIDLY AS SUNSET APPROACHES. THE LOSS OF HEATING WILL DIMINISH ANY REMNANT INSTABILITY. HOWEVER...LEFTOVER HIGHER DWPTS AND CLOUDS WILL LEAD TO A WARMER NIGHT THAN PREVIOUS NIGHTS...MINS MAINLY IN THE UPPER 40S AND 50S. MON... PROBABLY THE WARMEST DAY WAVE EXPERIENCED THUS FAR. H85 TEMPS MAY EVEN EXCEED +10C...BUT ONCE AGAIN AFTERNOON MIXING SHOULD EXCEED THIS LEVEL. SW RETURN FLOW EXPECTED...SO WITH ANOTHER DOWNSLOPE COMPONENT...EXPECT MANY AREAS TO APPROACH OR EVEN EXCEED LOWER 80S THIS TIME AROUND...EVEN NEAR THE E COAST AS THE W COMPONENT MAY BE ENOUGH TO PROHIBIT SEA BREEZE DEVELOPMENT. HOWEVER THE S COMPONENT WILL KEEP SOUTHERN COAST REGION COOLER EVEN AWAY FROM THE COAST. GOOD MIXING SUGGESTS VERY DRY WEATHER AND A BUILDING PRES GRADIENT SUPPORTS WIND GUSTS APPROACHING 20-25 MPH...SEE THE FIRE WEATHER SECTION BELOW FOR CONCERNS. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... BIG PICTURE... UPPER RIDGE BUILDS OVER THE EASTERN USA DURING THE WEEK WHILE A TROUGH DIGS OVER THE WESTERN USA. ONE SHORTWAVE PASSES NORTH OF NEW ENGLAND TUESDAY...A SECOND APPROACHES ACROSS CANADA AT THE END OF THE WEEK. MODEL MASS FIELDS ARE SIMILAR THROUGH MOST OF THE FORECAST PERIOD. THE ECMWF IS A LITTLE FASTER THAN THE GFS WITH THE END OF WEEK WEATHER SYSTEM. WE USED A BLEND OF MODEL DATA. THE DAILIES... MONDAY NIGHT-TUESDAY... UPPER SHORTWAVE PASSES NORTH OF NEW ENGLAND. THIS WILL PUSH A COLD FRONT ACROSS SOUTHERN NEW ENGLAND DURING TUESDAY. WHILE MUCH OF THE SUPPORTING UPPER JET IS WELL TO THE NORTH...THERE IS ENOUGH LOW LEVEL CONVERGENCE ALONG THE COLD FRONT TO SUPPORT SHOWERS. TOTALS IN THE UPPER 40S SUGGEST THE AIRMASS IS MARGINALLY SUPPORTIVE FOR THUNDERSTORMS. WE WILL MENTION SHOWERS WITH A SLIGHT CHANCE OF THUNDER. THE FRONT MOVES SOUTH OF OUR AREA TUESDAY NIGHT WITH DRYING OVERNIGHT. WEDNESDAY THROUGH FRIDAY...HIGH PRESSURE BUILDS OVER THE REGION. TEMPS ALOFT SUPPORT MAX SFC TEMPS IN THE LOW TO MID 70S. BOTH THE GFS AND ECMWF SHOW THE UPPER FLOW BECOMING NORTHWEST WEDNESDAY AND THURSDAY. A SHORTWAVE MOVES THROUGH THIS FLOW AND COULD PUSH A BACKDOOR COLD FRONT INTO EASTERN MASS. IF SO THEN THIS WOULD BRING COOLER DAYTIME TEMPS IN THE EAST...PROBABLY 60S. SATURDAY...NORTHERN STREAM WEATHER SYSTEM MOVES ACROSS CANADA LATE WEEK. THIS DRIVES A SURFACE COLD FRONT TOWARD NEW ENGLAND LATER FRIDAY AND SATURDAY. MOST OF THE SUPPORT WITH THIS SYSTEM IS TO OUR NORTH...OUR NORTHERN AREAS WOULD HAVE THE BEST CHANCE OF ANY SHOWERS. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. THIS AFTERNOON...HIGH CONFIDENCE. VFR. SEA BREEZES AT BOTH COASTS CONTINUE THIS AFTERNOON...OTHERWISE MAINLY LIGHT SOUTHERLY FLOW. SCATTERED SHOWERS ESPECIALLY WESTERN AND CENTRAL PORTIONS OF THE FORECAST AREA. AN ISOLATED CLAP OF THUNDER CANNOT BE RULED OUT. BRIEF MVFR VSBY POSSIBLE IN ANY SHOWERS. TONIGHT INTO MONDAY...HIGH CONFIDENCE. VFR. WINDS BECOME MORE SW OVERNIGHT AND CONTINUE INTO MON...WHEN GUSTS AROUND 20 KT ARE POSSIBLE AT TIMES. KBOS TAF...HIGH CONFIDENCE IN TAF. LOW RISK OF A FEW AFTERNOON SHOWERS 19Z-23Z. SEA BREEZE CONTINUES THROUGH THE AFTERNOON. KBDL TAF...HIGH CONFIDENCE IN TAF. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY...MODERATE TO HIGH CONFIDENCE. MAINLY VFR. A COLD FRONT MOVES THROUGH SOUTHERN NEW ENGLAND ON TUESDAY AND MAY BRING SCATTERED SHOWERS...POSSIBLY A THUNDERSTORM. CIGS/VSBYS COULD BRIEFLY LOWER TO MVFR IN ANY SHOWERS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. .SHORT-TERM /THROUGH MONDAY/... THROUGH TONIGHT...HIGH CONFIDENCE. MAINLY QUIET BOATING WEATHER EXPECTED WITH HIGH PRES SLIDING E OF THE WATERS. ONSHORE SEA BREEZES NEAR THE COAST THIS AFTERNOON OTHERWISE WINDS GENERALLY TURN FROM S TO SW THIS AFTERNOON AND OVERNIGHT. MONDAY...MODERATE CONFIDENCE. SW FLOW MAY APPROACH 25 KT NEAR THE SE COAST OF MA...BUT REMAIN 20 KT OR LESS ON THE OPEN OCEAN. THIS STEADY SW FLOW COULD ALSO ALLOW A BUILDING SWELL IN THE GULF OF MAINE TO EXCEED 5 FT...WHICH COULD IMPACT THE NE WATERS. NOT CONFIDENT ENOUGH ON THESE POTENTIAL SMALL CRAFT CONDITIONS TO SUPPORT AN ADVISORY AT THIS TIME...BUT IT MAY BE NEEDED. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY...MODERATE TO HIGH CONFIDENCE. MONDAY NIGHT-TUESDAY...A COLD FRONT MOVES ACROSS THE WATERS WITH SHOWERS. WINDS GUST TO 20-22 KNOTS IN ADVANCE OF THE FRONT...THEN SHIFT NORTHWEST WITH THE FRONTAL PASSAGE. SEAS 5-6 FEET ON THE OUTER WATERS. A SMALL CRAFT ADVISORY MAY BE NEEDED FOR THE OUTER WATERS. WEDNESDAY-THURSDAY...WINDS AND SEAS WILL BE BELOW SMALL CRAFT LEVELS. && .FIRE WEATHER... STILL WATCHING FIRE WEATHER CONDITIONS FOR MONDAY. MINIMUM AFTERNOON RELATIVE HUMIDITY VALUES DROPPING TO 20-30 PERCENT WITH AFTERNOON WIND GUSTS OF 20 TO PERHAPS 25 MPH. THEREFORE...MARGINALLY CLOSE TO RED FLAG CONDITIONS ON MONDAY. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/DOODY NEAR TERM...FIELD SHORT TERM...DOODY LONG TERM...WTB AVIATION...FIELD/WTB/DOODY MARINE...FIELD/WTB/DOODY FIRE WEATHER...STAFF

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