Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 260727 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 327 AM EDT THU MAR 26 2015 .SYNOPSIS...
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HIGH PRESSURE OFFSHORE WILL DIRECT A FLOW OF MILDER AIR INTO SOUTHERN NEW ENGLAND TODAY. LOW PRESSURE MOVING UP THE OHIO VALLEY WILL BRING RAIN TO OUR REGION DURING THE AFTERNOON AND EVENING. THE LOW WILL THEN SWING A COLD FRONT THROUGH SOUTHERN NEW ENGLAND TONIGHT. A SECOND COLD FRONT WILL BRING COLDER TEMPERATURES LATER FRIDAY INTO THIS WEEKEND. WEAK LOW PRESSURE MAY BRING A PERIOD OF LIGHT SNOW FRIDAY NIGHT INTO SATURDAY MORNING. HIGH PRESSURE WILL PUSH S OF NEW ENGLAND SUNDAY. ANOTHER BATCH OF LIGHT SNOW IS POSSIBLE LATE SUNDAY NIGHT INTO MONDAY AHEAD OF A COLD FRONT.
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&& .NEAR TERM /THROUGH TODAY/...
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THROUGH 8 AM / 12Z A FEW LINGERING SHOWERS ALONG THE SOUTH COAST...OTHERWISE LOW CLOUDS/FOG/DRIZZLE EXPANDING OVER THE REGION. EXPECT FOG AND DRIZZLE TO LINGER UNTIL MORNING. TODAY... FOG AND LOW CLOUDS MAY LIFT A LITTLE THIS MORNING. BUT LOW PRESSURE MOVING NORTHEAST FROM ARKANSAS AND THROUGH THE OHIO VALLEY THIS MORNING. THE SHIELD OF ISENTROPIC LIFT LEADING THIS LOW IS FORECAST TO REACH WESTERN NEW ENGLAND AROUND 16Z AND OVERSPREAD OUR AREA BEFORE 18Z. A 70 KNOT LOW LEVEL JET WILL MOVE OVER OUR AREA THIS AFTERNOON AND MAINTAIN THE LIFT THROUGH EVENING. PRECIPITABLE WATER VALUES IN THE AIRMASS FEEDING OVER US CONTINUE TO BE ADVERTISED AT 1.0 TO 1.25 INCHES...NEAR 2 SD FOR LATE MARCH. SO THERE IS POTENTIAL FOR LOCALLY HEAVY DOWNPOURS. STABILITY PARAMETERS CONTINUE TO SHOW SOME POTENTIAL FOR THUNDER...LIKELY ELEVATED...OVER OUR AREA. SO THE FORECAST WILL CONTINUE TO FEATURE AFTERNOON RAIN AND WIDELY SCATTERED THUNDER. EXPECTED TEMPS IN THE 50S AND DEW POINTS IN THE 40S WILL CONTRIBUTE TO SNOWMELT. FOG WILL ALSO BE A CONCERN AS THE MOIST AIRMASS MOVES OVER THE REMAINING SNOWPACK. THE SOUTH COAST WILL ALSO BE OF CONCERN FOR FOG...AS THE MOIST AIR MOVES OVER 35-39 DEGREE WATER BEFORE REACHING LAND.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM FRIDAY/...
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TONIGHT... LOW PRESSURE MOVES OVER NEW ENGLAND AND DRAWS A COLD FRONT SOUTHEAST ACROSS THE REGION. THIS SYSTEM DEMONSTRATED IT HAD PLENTY OF INSTABILITY AS IT MOVED PAST OKLAHOMA WEDNESDAY. MODEL DATA SHOWS IT CONTAINING STRONG FGEN VALUES AS IT CROSSES NEW ENGLAND. THIS ALONG WITH THE HIGH PRECIP WATER VALUES SHOULD SUPPORT MORE RAIN...ALTHOUGH MORE OF A SHOWERY PRECIPITATION. TEMPERATURE PROFILES SUGGEST RAIN...BUT POSSIBLY A RAIN/SNOW MIX IN NORTHWEST MASS LATE AT NIGHT. FRIDAY... COLD FRONT DRIFTS FARTHER OFFSHORE WHILE UPPER TROUGH OVER THE GREAT LAKES MOVES EAST. A 150 KNOT JET CORE WILL BE IN PLACE OVER THE NORTHEAST CORRIDOR WITH SOUTHERN NEW ENGLAND UNDER THE RIGHT ENTRANCE REGION. MEANWHILE...A SECOND COLD FRONT MOVES SOUTH FROM THE ST LAWRENCE VALLEY. EXPECT AT LEAST SCATTERED PCPN WITH TEMPERATURE PROFILES FAVORING RAIN. TEMPS ALOFT ALSO FAVOR MAX TEMPS IN THE 40S.
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&& .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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DETAILS... FRIDAY NIGHT THROUGH SATURDAY NIGHT...MODERATE CONFIDENCE. SHORT RANGE MODELS SIGNALING THE H5 TROUGH CONTINUES TO DIG DOWN TO THE MID ATLC STATES...AND BECOMES A NEUTRAL TILT. A COUPLE OF MODELS /GFS AND TO A LESSER DEGREE THE ECMWF/ EVEN SHOWING SIGNS OF A CUTOFF FORMING WHILE REMAINING SLOWLY PROGRESSIVE DURING THIS TIMEFRAME. THIS WILL HELP THE SHORT WAVE WRAPPING AROUND THIS DIGGING TROUGH DEVELOP S OF NEW ENGLAND FRI NIGHT. STILL SOME QUESTION AS TO HOW CLOSE TO THE COAST THE PRECIP SHIELD WILL BE... BUT MOST MODELS AND ENSEMBLES HOLDING LIGHT PRECIP ACROSS THE REGION WITH THE BEST CHANCE GENERALLY NEAR OR S OF THE MASS PIKE. COLDER AIR WORKS IN BEHIND THE DEPARTING AND WEAKENING COLD FRONT. PRETTY GOOD LIFT AND FORCING...ALONG WITH COLD TEMPS ALOFT...SO WILL SEE PRECIP CHANGE BACK OVER TO LIGHT SNOW FRI NIGHT. EXPECT MAINLY LESS THAN AN INCH WITH THE BEST CHANCE ACROSS INTERIOR SECTIONS OF EASTERN AND CENTRAL MA/W RI INTO NE CT. WILL NEED TO MONITOR THIS SHORT WAVE AS IT SLOWLY MOVES OFFSHORE. LOWS FRI NIGHT WILL RANGE FROM THE LOWER-MID 20S INLAND TO AROUND 30 NEAR THE S COAST. HAVE CARRIED SLIGHT CHANCE TO LOW CHANCE POPS. SHOULD SEE PRECIP CHANGE BACK TO RAIN SAT AROUND MID MORNING BEFORE TAPERING OFF SAT AFTERNOON. TIMING OF THE EXIT STILL SOMEWHAT IN QUESTION...BUT MODELS AND ENSEMBLES IN PRETTY GOOD AGREEMENT. HIGHS SAT WILL BE IN THE MID 30S TO AROUND 40. WILL BE A BIT BLUSTERY SAT MAINLY ALONG THE IMMEDIATE COAST WITH SOME GUSTS UP TO AROUND 25 KT BUT SHOULD DIMINISH LATE IN THE DAY. SHOULD SEE CLEARING CONDITIONS MOVE IN SAT NIGHT AS HIGH PRES RIDGE WORKS E. SOME MODELS DO LINGER THE PRECIP INTO EARLY SAT NIGHT...SO SOMEWHAT LOWERED CONFIDENCE DURING THIS TIMEFRAME. N-NW WINDS WILL STIR AS TEMPS FALL BACK TO THE UPPER TEENS TO LOWER 20S WELL INLAND TO AROUND 30 ACROSS THE OUTER CAPE AND NANTUCKET. SUNDAY AND SUNDAY NIGHT...HIGH CONFIDENCE. RIDGING AT THE SURFACE AND ALOFT BUILDS ACROSS THE REGION. WILL SEE A GOOD AMOUNT OF SUN. HOWEVER...H85 TEMPS RANGE FROM ONLY -9C TO -11C EARLY SUN THEN ONLY SLOWLY RISE. HIGHS WILL BE IN THE UPPER 30S TO MID 40S...WELL BELOW SEASONAL NORMALS FOR LATE MARCH. CLOUDS WILL MOVE IN SUNDAY NIGHT AS FAST NW FLOW ALOFT BEGINS TO BRING IN HIGH LEVEL MOISTURE FROM NEXT APPROACHING SYSTEM. WINDS SHIFT TO SW OVERNIGHT...SO LOWS SUN NIGHT FALL BACK TO THE UPPER 20S TO LOWER 30S /ONLY SLIGHTLY BELOW SEASONAL NORMS/. MONDAY...LOW TO MODERATE CONFIDENCE. ANOTHER SHORT WAVE IN FAST FLOW ALOFT APPROACHES NORTHERN NEW ENGLAND DURING THIS TIMEFRAME. S-SW WINDS BRING MILDER TEMPS. LOOKS LIKE MOST OF THE ENERGY AND LIMITED MOISTURE WILL REMAIN ACROSS NORTHERN NEW ENGLAND...THOUGH COULD SEE SOME WIDELY SCT SHOWERS WITH HIGHS IN THE 40S WITH A FEW SPOTS POSSIBLY TOUCHING 50. CARRIED SLIGHT CHANCE POPS WITH THIS SYSTEM. THIS SYSTEM DOES MOVE ALONG...SO SHOULD SEE IMPROVEMENT MON EVENING. TUESDAY AND WEDNESDAY...LOW CONFIDENCE. WIDE VARIANCE IN MODEL SOLUTIONS LENDS TO LOW CONFIDENCE DURING THIS TIMEFRAME. FOR NOW...CARRIED DRY CONDITIONS ON TUESDAY AND WEDNESDAY WITH HIGH PRES BUILDING ACROSS. HOWEVER...NEXT SYSTEM MAY BEGIN TO APPROACH THE E SLOPES OF THE BERKSHIRES WED AFTERNOON.
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&& .AVIATION /06Z THURSDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. HIGH CONFIDENCE ON OVERALL FORECAST...BUT SOME UNCERTAINTY ON EXACT TIMING. TODAY... UNTIL 12Z... MOST OF THE SHOWERS HAVE MOVED AWAY BUT LINGERING LOW LEVEL MOISTURE SHOULD HOLD LOW CLOUDS IN PLACE. EXPECT MVFR CIGS TRENDING TO IFR/LIFR IN AREAS OF FOG AND DRIZZLE. AFTER 12Z... IFR/LIFR CIGS/VSBYS THROUGH THE DAY. DRIZZLE AND FOG IN THE MORNING WILL GIVE WAY TO AN AREA OF RAIN IN THE AFTERNOON. LOW PROBABILITY OF THUNDER. LOW LEVEL 70-KNOT SOUTHWEST JET AT 2000 FEET MOVES OVERHEAD LATE AFTERNOON/EVENING AND SHOULD GENERATE LOW LEVEL WIND SHEAR TONIGHT... COLD FRONT CROSSES DURING THE FIRST HALF OF THE NIGHT. SOUTHWEST WINDS IN THE EARLY NIGHT WILL SHIFT TO NORTHWEST WINDS AFTER MIDNIGHT. LOW CIGS/VSBYS IN SHOWERS AND SOME DOWNPOURS. LOW LEVEL WIND SHEAR AHEAD OF THE FRONT BUT MOVING OFF TO THE EAST WITH THE FRONTAL PASSAGE. FRIDAY... FOG AND LINGERING SHOWERS EARLY BUT TREND WILL BE MVFR EARLY AND VFR IN THE AFTERNOON. SOUTHEAST MASS/RI MAY LINGER AROUND 2500 FOOT CIG THROUGH EVENING. KBOS TAF...HIGH CONFIDENCE ON OVERALL TRENDS. KBDL TAF...HIGH CONFIDENCE ON OVERALL TRENDS. OUTLOOK...FRIDAY NIGHT THROUGH MONDAY...MODERATE TO HIGH CONFIDENCE FRIDAY NIGHT THROUGH SATURDAY...MVFR CIGS/VSBYS LINGERING THROUGH A GOOD PORTION OF THIS PERIOD. WILL SEE SCT -SHRA DURING FRI...CHANGING OVER TO -SHSN FRI NIGHT FROM N-S...THOUGH WILL LIKELY BE MIXED -RASN ALONG THE IMMEDIATE COAST. SATURDAY NIGHT INTO SUNDAY...VFR CONDITIONS LIKELY. SUNDAY NIGHT AND MONDAY...VFR CONDITIONS EARLY SUN NIGHT WILL LOWER TO MVFR TO LOCAL IFR IN ISOLD -SN MAINLY AROUND OR AFTER MIDNIGHT. EXPECT -SN TO CHANGE TO -RA MONDAY MORNING WITH CONTINUED MVFR CONDITIONS. SHOULD SEE CONDITIONS IMPROVE TO VFR FROM W-E MONDAY AFTERNOON/EVENING. && .MARINE...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. TODAY...INCREASING SOUTH TO SOUTHWEST WIND WITH GUSTS 25-33 KNOTS THIS AFTERNOON. SEAS BUILDING TO 5-8 FEET ESPECIALLY ON THE SOUTHERN WATERS. MOIST AIRMASS MOVING ACROSS THE 35-40 DEGREE WATER MAY CREATE LOW VSBYS IN FOG...WITH LOCALLY DENSE FOG POSSIBLE. RAIN MAINLY THIS AFTERNOON WITH AN ISOLATED TSTM ALSO POSSIBLE. SMALL CRAFT ADVISORY IS IN PLACE FOR MOST OF OUR WATERS. TONIGHT...A COLD FRONT CROSSES THE WATERS AFTER MIDNIGHT. SOUTH TO SOUTHWEST WINDS 25-30 KNOTS EARLY...SHIFTING NORTHWEST AND DIMINISHING AFTER MIDNIGHT. SEAS CONTINUE TO BUILD DURING THE SOUTHWEST WINDS AND MAY REACH 8 TO 12 FEET ON THE OUTER WATERS AND ON EXPOSED WATERS SUCH AS RI SOUND. LOCALLY DENSE FOG POSSIBLE DURING THE EARLY NIGHT...THINNING AFTER THE WIND SHIFT. FRIDAY... NORTH WINDS 15 TO 20 KNOTS. SEAS LINGER 5 TO 8 FEET MAINLY ACROSS THE OUTER WATERS. SMALL CRAFT HEADLINES WILL CONTINUE INTO THE DAY MAINLY ON THE OUTER WATERS. OUTLOOK...FRIDAY NIGHT THROUGH MONDAY... MODERATE CONFIDENCE FRIDAY NIGHT THROUGH MONDAY. FRIDAY NIGHT....LOW PROB OF GALE GUSTS FRI NIGHT. EXPECT SEAS TO REMAIN AOA 5 FT...MAINLY ACROSS THE OUTER WATERS. SATURDAY AND SATURDAY NIGHT...EXPECT NW WINDS TO CONTINUE TO GUST TO SMALL CRAFT LEVELS WITH SEAS BUILDING UP TO 6-9 FT ON THE OUTER WATERS THROUGH SAT NIGHT. SUNDAY THROUGH MONDAY...WINDS AND SEAS BRIEFLY SUBSIDE AS WINDS BACK TO SW SUN/SUN NIGHT...THOUGH SEAS MAY REMAIN AROUND 5 FT ON THE FAR OUTER WATERS. WINDS AND SEAS INCREASE AGAIN MONDAY AHEAD OF NEXT SYSTEM SO SMALL CRAFTS WILL LIKELY BE RENEWED.
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&& .HYDROLOGY...
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BASIN AVERAGE RAINFALL AMOUNTS RANGE FROM 0.5 TO 1.25 INCHES ACROSS THE REGION...POSSIBLY 1.50 IN SPOTS BUT NOT WIDESPREAD. NOHRSC MODELING ADDS 1 TO 3 INCHES OF WATER FROM MELTING SNOW DUE TO TEMPERATURES IN 40S/LOWER 50S COMBINED WITH DEWPOINTS RISING INTO 40S AND SW WINDS. THIS WILL BRING RISES ON RIVERS AND STREAMS TODAY AND TONIGHT...ESPECIALLY SMALLER ONES WHICH MAY APPROACH MINOR FLOOD STAGE. HOWEVER GIVEN RAINFALL IS SPREAD OUT OVER A LONG DURATION WITH MANY DRY PERIODS ALONG WITH DEW PTS ONLY BRIEFLY APPROACHING 50...RISK OF FLOODING IS TOO LOW FOR HEADLINES. IN FACT RFC ONLY HAS A FEW POINTS ENTERING ACTION STAGE WITH NONE IN MINOR FLOOD. THUS NO HEADLINES. A MORE LIKELY CONCERN WILL BE URBAN/POOR DRAINAGE FLOODING. THE CORE OF HIGHER RAINFALL IS EXPECTED ACROSS RI/SOUTHEAST MASS WITH HEAVIEST AMOUNTS ALONG THE SOUTH COAST. ALTHOUGH SNOW COVER IS LESS ALONG THE COAST THAN FARTHER NORTH/INLAND...THE FROZEN GROUND AND LACK OF VEGETATION WILL CONTRIBUTE TO GREATER RUNOFF. LATER SHIFTS WILL NEED TO MONITOR THIS FOR PITENTIAL SMALL STREAM/URBAN FLOOD ADVISORY.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 11 PM EDT THIS EVENING FOR ANZ231>237. SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ250. SMALL CRAFT ADVISORY UNTIL 6 AM EDT FRIDAY FOR ANZ254. SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 AM EDT FRIDAY FOR ANZ255-256. && $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB/EVT SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/EVT MARINE...WTB/EVT HYDROLOGY...

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