Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 261308 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 905 AM EDT THU MAR 26 2015 .SYNOPSIS... 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. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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***NUMEROUS SHOWERS WILL RE-DEVELOP THIS AFTERNOON*** 905 AM UPDATE... AREAS OF FOG WERE STILL LOCALLY DENSE ACROSS AREAS SOUTH OF THE MA TURNPIKE...MAINLY ALONG THE SOUTH COAST/CAPE/ISLANDS AND PORTIONS OF THE CONNECTICUT RIVER VALLEY. WE HAVE EXTENDED THE DENSE FOG ADVISORY UNTIL NOON...BUT MAY BE ABLE TO CANCEL IT EARLIER IN AREAS AWAY FROM THE THE SOUTH COAST. WE WILL CONTINUE TO MONITOR. OTHERWISE...WHILE IT WAS DRY THIS MORNING THE NEXT SHORTWAVE WILL APPROACH THE REGION BY AFTERNOON. IN RESPONSE...NUMEROUS SHOWERS WILL DEVELOP WITH BRIEF HEAVY RAINFALL AS PWATS IN EXCESS OF 1 INCH. MARGINAL ELEVATED INSTABILITY MAY RESULT IN AN ISOLATED THUNDERSTORM OR TWO...BUT NOT EXPECTING ANYTHING WIDESPREAD. HIGH TEMPERATURES REMAIN QUITE TRICKY THIS AFTERNOON GIVEN CLOUD COVER AND AREAS OF FOG. HIGHS PROBABLY TOP OUT IN THE UPPER 40S TO MIDDLE 50S FOR MOST LOCATIONS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... 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. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... HIGHLIGHTS... * SCT SNOW/RAIN SHOWERS ON SATURDAY * A WEAK COLD FRONT WILL MOVE THROUGH ON MONDAY BRINGING SCT SHOWERS * MODERATING SPRING-LIKE TEMPS INTO NEXT WEEK MODEL GUIDANCE... OVERALL AMPLIFIED TROUGH PATTERN WILL CONTINUE WITH 00Z GUIDANCE IN GOOD AGREEMENT. STILL SUBTLE DETAIL DIFFERENCES AT THE MESO LEVEL. BROAD UPPER TROUGH REMAINS OVER THE EAST COAST FRIDAY NIGHT INTO SATURDAY WITH THE TROUGH MOVING EAST OF THE REGION LATE SATURDAY NIGHT INTO SUNDAY. LOW PRESSURE SYSTEM WILL CROSS SRN CANADA AND BRING A TRAILING FRONT THROUGH THE AREA ON MONDAY. GUIDANCE STILL SHOWS PERSISTENT DIFFERENCES WITH SOUTHWARD EXTENT OF THE TRAILING FRONT AS THE GFS IS FARTHER SOUTH. GUIDANCE WAS SOMEWHAT CLOSER TO BEING EVENLY SPLIT 24 HRS AGO BUT THE PAST COUPLE UKMET/CMC RUNS TRENDED TO THE NRN CLUSTER AND EVEN THE 18Z/00Z GEFS MEANS HAVE STARTED TO TREND NWD OF THE OPERATIONAL GFS RUNS. SO TRENDED THIS PORTION TOWARDS THE EC/HPC. LASTLY THE DOMINATE NORTHERN STREAM FLOW BECOMES MORE PROGRESSIVE AS STRONG WESTERN RIDGE WEAKENS AS SEVERAL WAVES BEGIN TO MOVE THROUGH THE FLOW MIDDLE OF NEXT WEEK. THESE WILL NEED TO BE WATCHED CLOSELY FOR THE UPCOMING EASTER WEEKEND. DETAILS... * FRIDAY NIGHT INTO SATURDAY...MODERATE CONFIDENCE. COLD AIR WILL USHER ACROSS THE REGION FRIDAY NIGHT INTO SATURDAY BEHIND PASSING COLD FRONT. THE UPPER LEVEL TROUGH AXIS WILL BE OVERHEAD...COULD SEE SOME SCT SNOW SHOWERS DURING THE DAY ON SATURDAY. CONFIDENCE IS INCREASING COMPARED TO YESTERDAY AS MOST OF THE GUIDANCE SPITS OUT SOME QPF. SURFACE LOW PRESSURE WILL MOVE WELL SOUTH OF THE BENCHMARK FRIDAY NIGHT/SAT MORNING HOWEVER...GUIDANCE IS HINTING AT A WEAK SURFACE/INVERTED TROUGH OVER THE AREA ON SATURDAY. THIS COMBINED WITH LOW LEVEL MOISTURE AND VERY STEEP LAPSE RATES WILL ALLOW FOR SCT SNOW/RAIN SHOWERS TO DEVELOP. EXPECT MOSTLY CLOUDY SKIES SO TEMPS WILL STRUGGLE TO REACH INTO THE UPPER 30S...SO THINKING P-TYPE IS MORE SNOW. MODELS ARE ALSO HINTING AT POSSIBLE FRONTOGENESIS WHICH COULD INCREASE SNOWFALL RATES. LOW CONFIDENCE ON WHERE THIS MAY SET UP BUT WILL NEED TO WATCH FOR SOME AREA IN SOUTHERN NEW ENGLAND SEEING A SURPRISED 1-2 INCHES POSSIBLY. TEMPS OVERNIGHT WILL FALL WELL BELOW NORMALS WITH LOWS AROUND THE TEENS TO LOW 20S. TEMPS MAY BE SLIGHTLY COLDER AT WE COULD RADIATE OUT THANKS TO CLEARING SKIES AND LIGHT WINDS ACROSS THE INTERIOR. LOW PROBABILITY OF LINGERING OCEAN EFFECT SNOW ACROSS THE CAPE. * SUNDAY...HIGH CONFIDENCE. SUNDAY IS A TRANSITION DAY AS DEEP TROUGH BEGINS TO PULL OFFSHORE AND UPPER LEVEL RIDGE MOVES INTO THE REGION. TEMPS ON SUNDAY WILL WARM INTO THE MID 40S TO LOW 50S AS WARM AIR ADVECTION ADVANCES. EXPECT MOSTLY CLEAR SKIES IN THE MORNING BUT THEY WILL BEGIN TO CLOUD UP DURING THE AFTERNOON AS THE NEXT SYSTEM APPROACHES FROM THE WEST. MONDAY INTO WEDNESDAY...LOW CONFIDENCE. NEXT UPPER LEVEL DISTURBANCE WILL IMPACT SOUTHERN NEW ENGLAND LATE SUNDAY INTO MONDAY. STILL A GOOD AMOUNT OF SPREAD AMONGST THE GUIDANCE AS MENTIONED ABOVE...BUT TRENDED TOWARDS THE EC/HPC ON THIS PORTION OF THE FORECAST. SURFACE LOW ACROSS THE GREAT LAKES WILL PASS JUST NORTH OF SNE...DRAGGING ASSOCIATED COLD FRONT WITH IT. TEMPS AT THE ONSET LOOK TO BE COOL THEN WARM UP DURING THE DAY ON MONDAY PRIOR TO FRONTAL PASSAGE. TIMING OF THE FRONT WILL BE AN ISSUE IMPACTING HIGH TEMPS. EC KEEPS THEM COOL WITH A FASTER PASSAGE COMPARED TO THE GFS WHICH IS SLOWER BUT WARMS TEMPS UP INTO THE 50S. AT THE ONSET OF PRECIP EXPECT A FEW SNOW SHOWERS...BUT THEN TRANSITIONING TO RAIN FAIRLY QUICKLY AS TEMPS WARM. A FEW QUICK MOVING SYSTEMS WILL MOVE THROUGH THE FLOW DURING THE UPCOMING WEEK. FIRST ONE IS LATE TUESDAY INTO WED FOLLOWED BY ANOTHER THUS/FRIDAY. AT THE SURFACE...HIGH PRESSURE WILL BUILD ON TUESDAY FOLLOWED BY WEAK LOW ON WEDNESDAY AND A WARM FRONT ON THURSDAY. && .AVIATION /13Z 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... 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 CONFIDENCE. FRIDAY NIGHT THROUGH SATURDAY...MVFR CONDITIONS IMPROVING TO VFR FROM WEST TO EAST ON FRIDAY NIGHT. CONDITIONS MAY DETERIORATE FROM EAST TO WEST ON SATURDAY IN SCT SNOW SHOWERS. LOW CONFIDENCE ON ANY ACCUMS ON RUNWAYS BUT FEEL BEST SHOT IS ORH. SATURDAY NIGHT INTO SUNDAY...VFR CONDITIONS LIKELY. SCT MVFR ACROSS THE CAPE IN OCEAN EFFECT SNOW SHOWERS. MONDAY...VFR DROPPING TO POSSIBLE MVFR IN SCT RAIN SHOWERS. && .MARINE... 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 INTO MONDAY. FRIDAY NIGHT....WINDS INCREASE UP TO 25-30KTS BEHIND FRONTAL PASSAGE. SCA WILL BE NEEDED. 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. LOW PROB OF SCT SNOW/RAIN SHOWERS DURING THE DAY. 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. && .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 POTENTIAL SMALL STREAM/URBAN FLOOD ADVISORY.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...DENSE FOG ADVISORY UNTIL NOON EDT TODAY FOR CTZ002>004. MA...DENSE FOG ADVISORY UNTIL NOON EDT TODAY FOR MAZ008>013-017>024. RI...DENSE FOG ADVISORY UNTIL NOON EDT TODAY FOR RIZ001>008. MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 10 AM EDT FRIDAY FOR ANZ232>235-237. SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 2 AM EDT FRIDAY FOR ANZ231-236. SMALL CRAFT ADVISORY UNTIL 6 PM EDT FRIDAY FOR ANZ250-254>256.
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&& $$ SYNOPSIS...WTB/DUNTEN NEAR TERM...FRANK SHORT TERM...WTB LONG TERM...DUNTEN AVIATION...WTB/DUNTEN MARINE...WTB/DUNTEN HYDROLOGY...STAFF

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