Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 310900 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 500 AM EDT TUE MAR 31 2015 .SYNOPSIS...
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A QUIET WEATHER DAY IS FOLLOWED BY A CHANCE FOR RAIN/SNOW ACROSS THE SOUTH COAST OVERNIGHT. WARMER TEMPERATURES THURSDAY AND ESPECIALLY FRIDAY AHEAD A COLD FRONT. LOW PRESSURE DEVELOPS ALONG THE COLD FRONT FRIDAY NIGHT AND MOVES ACROSS THE REGION BY EARLY SATURDAY BRINGING LOCALLY HEAVY RAIN SHOWERS. MAINLY DRY AND MUCH COLDER SUNDAY. STILL COOL WITH A CHANCE OF A RAIN OR SNOW SHOWER ON MONDAY.
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&& .NEAR TERM /UNTIL 3 PM THIS AFTERNOON/... A FEW LOW-MID CLOUDS ACROSS THE REGION THIS MORNING AS A COLD FRONT APPROACHES THEN CROSSES THE REGION THIS MORNING. DRY WX PREVAILS THROUGH THE DAY. THE COLD ADVECTION ASSOCIATED WITH THE FRONT WILL LEAD TO FALLING H85 TEMPS...PREVENTING DAYTIME HIGHS FROM REACHING SEASONAL NORMALS. MAINLY THE MID-UPPER 40S ACROSS THE REGION. CLOUDS INCREASE FROM THE W-SW THIS AFTERNOON. && .SHORT TERM /3 PM THIS AFTERNOON THROUGH 6 PM WEDNESDAY/... THIS EVENING AND OVERNIGHT... A FAST MOVING CLIPPER WITH CP ORIGINS WILL BE RIDING STALLED BAROCLINIC ZONE S OF THE SRN NEW ENGLAND WATERS DURING THE EARLY OVERNIGHT HOURS. AT ODDS IN THE LAST COUPLE OF DAYS IS HOW FAR N THE PRECIP SHIELD ASSOCIATED WITH THIS CLIPPER WILL REACH. YESTERDAY/S RUNS WERE OFFSHORE. TONIGHT...A SHIFT BACK TO THE N...EVEN IN AVAILABLE MESO-SCALE GUIDANCE. NOTE A MODEST LOW-MID LVL F-GEN AXIS WHICH IS SUPPORTED BY BUFKIT PROFILES AS A CHANNEL OF NEGATIVE OMEGA BETWEEN H8 AND H6. DRY AIR WILL BE ENTRAINING INTO THE LOW-LVLS FROM THE N THROUGH THE SAME PERIOD. GIVEN THESE FACTORS...LOOKS LIKE A LIGHT PRECIP SHIELD WILL SLOWLY MOVE ACROSS THE REGION FROM SW THEN DUE E THROUGH THE EVENING- OVERNIGHT. AT THIS TIME...IT LOOKS LIKE THE DRY AIR WINS ANYWHERE S OF A LINE DRAWN ACROSS THE CT/RI BORDER WITH MA AND SE MA. THE CLOSER TO THE COAST THAT ONE GETS...THE BETTER CHANCE FOR MORE STEADY PRECIP...SO IT/S LIKELY SOME AREAS TOWARD THE EDGE OF THE SHIELD RECEIVE SPRINKLES/FLURRIES AT BEST. REGARDING P-TYPE...LOW-LVL TEMP PROFILES SUGGEST MAINLY A RAINY START IN CT THIS EVENING...GRADUALLY TRANSITIONING TO A MIX OF RAIN/SNOW AS THE PRECIP SHIELD SHIFTS E. THERE IS SOME MODERATE LIFT WITHIN THE DENDRITE ZONE ALOFT...SO IT/S POSSIBLE THE CHANGE OVER TO SNOW COULD OCCUR FASTER IN AREAS OF HEAVIER PRECIP THANKS TO DYNAMIC COOLING. OTHERWISE...EXPECT A CHANGE TO LIGHT SNOW BEFORE ENDING. ACCUMS WILL BE LIGHT TO NIL...AND MAINLY ON GRASSY SFCS. WEDNESDAY... COLD ADVECTION AND HIGH PRES FOLLOWS THE DEVELOPING CLIPPER OFFSHORE. SKIES CLEAR...BUT WITH H85 TEMPS FALLING BACK TO -8C TO -10C SUSPECT ANOTHER DAY WHERE HIGH TEMPS REMAIN BELOW SEASONAL NORMALS. MAINLY LOW-MID 40S EXPECTED...BREEZY WITH WIND GUSTS AROUND 20 MPH AT TIMES. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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HIGHLIGHTS... * TEMPERATURES RISING TO NEAR NORMAL THU AND ABOVE NORMAL FRI * STORM SYSTEM BRINGS SHOWERS THU NIGHT INTO EARLY SAT... WEDNESDAY NIGHT...HIGH PRESSURE CENTERED OFF THE MID ATLANTIC COAST WILL RIDGE NORTHWARD ACROSS SOUTHERN NEW ENGLAND PROVIDING CLEAR SKIES AND COLD TEMPERATURES. LOWS IN THE 20S. THURSDAY...TEMPERATURES BEGIN TO MODERATE AS HIGH PRESSURE MOVES OFFSHORE AND LOW PRESSURE MOVES ACROSS ONTARIO. SOUTHWEST FLOW WILL BOOST TEMPERATURES TO NEAR NORMAL LEVELS...IN THE LOWER 50S EXCEPT COOLER ON THE CAPE AND ISLANDS. LOW LEVEL JET WILL INCREASE LATE IN THE AFTERNOON...REACHING 50 KNOTS AT 925 MB. AT THE SURFACE...EXPECT WINDS TO GUST TO 20-25 MPH TOWARD EVENING. THURSDAY NIGHT AND FRIDAY...A COLD FRONT MOVES EASTWARD INTO SOUTHERN NEW ENGLAND AND STALLS SOMEWHERE ACROSS THE INTERIOR. THERE ARE TIMING DIFFERENCES IN THE MODELS...WITH THE GFS FASTEST AND ECMWF SLOWEST. NEVERTHELESS...IT WILL BE A CLOUDY PERIOD WITH A GOOD CHANCE OF SHOWERS. THE SHOWALTER INDEX DROPS TO BELOW ZERO THU NIGHT BUT OTHER PARAMETERS ARE NOT FAVORABLE FOR CONVECTION... SO WILL NOT MENTION ANY ELEVATED THUNDER AT THIS TIME. TEMPERATURES WILL HOLD IN THE 40S THU NIGHT...AND DESPITE CLOUDINESS..SHOULD RISE TO ACTUAL SPRINGLIKE READINGS...IN THE LOWER 60S FRI (UPPER 40S TO MID 50S CAPE AND ISLANDS) AS 850 MB TEMPS RISE TO NEAR +10C. GFS MEX GUIDANCE ACTUALLY GIVES 66 FOR BDL FRI BUT WITH CLOUDY SKIES AND SCATTERED SHOWERS...HAVE HELD CLOSE TO PREVIOUS FORECAST OF LOWER 60S. FRIDAY NIGHT INTO SATURDAY...A LOW PRESSURE STORM SYSTEM IS FORECAST TO MOVE EASTWARD FROM THE OHIO VALLEY AND INTENSIFY ALONG THE STALLED FRONT AS IT REACHES SOUTHERN NEW ENGLAND. THE MAIN IMPACT WILL BE A WIDESPREAD RAINFALL OF ABOUT 0.5 INCHES...BUT THERE IS THE POTENTIAL FOR POCKETS OF 1 INCH OF RAIN. THE GFS STRENGTHENS THE LOW TO 995 MB AND HAS IT MOVING INTO THE GULF OF MAINE WITH ENOUGH PRECIPITATION WRAPPING AROUND TO CAUSE A CHANGEOVER TO SNOW IN NORTHWEST PORTIONS OF MA. THE ECMWF HAS TRENDED COLDER...BUT NOT THAT COLD. YESTERDAY IT HAD AN INTENSE STORM OVER NORTHERN VERMONT AND THIS MORNING/S RUN HAS IT OVER SOUTHEAST NEW HAMPSHIRE...CLOSER TO THE GFS SOLUTION. HOWEVER... ANY LEFTOVER SNOW WOULD BE CONFINED TO AREAS NORTH AND WEST OF OUR FORECAST AREA. THAT IS HOW WE CURRENTLY PLAYED THIS. THE PRECIPITATION CLEARS OUT BY ABOUT NOON ON SATURDAY. HIGHS MAINLY IN THE 40S. SUNDAY...MAINLY SUNNY AND DRY BUT MUCH COLDER WITH HIGHS ONLY IN THE LOWER TO MID 40S...BELOW NORMAL AGAIN. CANNOT RULE OUT A BRIEF PASSING FLURRY IN THE MORNING AS A WEAK UPPER DISTURBANCE PASSES THROUGH. MONDAY...A WARM FRONT APPROACHES THE REGION IN ASSOCIATION WITH LOW PRESSURE MOVING THROUGH THE UPPER MIDWEST AND LOWER GREAT LAKES REGION. THIS COULD BRING ANOTHER CHANCE OF RAIN...OR POSSIBLY MIXED PRECIPITATION IN NORTHERN MA...BY LATE MONDAY. THE ECMWF IMPLIES THAT THIS COULD BE A LONG DURATION EVENT INTO THE MIDDLE OF NEXT WEEK BECAUSE STRONG HIGH PRESSURE BUILDS INTO NORTHERN NEW ENGLAND FROM CANADA. A LOT WILL DEPEND ON THE ORIENTATION OF THAT HIGH. ANYWAY...THAT IS A WHOLE WEEK AWAY.
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&& .AVIATION /08Z TUESDAY THROUGH SATURDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. .SHORT TERM /THROUGH WEDNESDAY/... THROUGH TODAY...HIGH CONFIDENCE. MAINLY VFR. EXPECT INCREASING CLOUDS THIS AFTERNOON WITH SOME W WINDS GUSTING 20+ AT TIMES ESPECIALLY E MA. THIS EVENING AND OVERNIGHT...MODERATE CONFIDENCE. A MIX OF MVFR/VFR CONDITIONS IN LIGHT RAIN/SNOW ESPECIALLY S OF AN HFD-IJD-PYM LINE. VFR TO THE N. CONDITIONS IMPROVE DURING EARLY MORNING HOURS. ANY SNOW ACCUMS WILL BE LIGHT...AND MAINLY ON GRASS RATHER THAN RUNWAYS. WEDNESDAY...HIGH CONFIDENCE. MAINLY VFR. KBOS TAF...HIGH CONFIDENCE IN TAF. KBDL TAF...MODERATE CONFIDENCE IN TAF...AT ISSUE IS THE CHANCE FOR A WINDOW OF MVFR CONDITIONS THIS EVENING. OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY... WEDNESDAY AND THURSDAY...HIGH CONFIDENCE. VFR. GUSTY SOUTHWESTERLY WINDS ARE POSSIBLE THURSDAY. THURSDAY NIGHT AND FRIDAY...MODERATE CONFIDENCE. VFR BECOMING MVFR CEILINGS AND VSBYS IN SHOWERS. LOW LEVEL WIND SHEAR EXPECTED THROUGHOUT THE REGION WITH SOUTHERLY SURFACE WINDS 10-20 KT INCREASING TO SOUTHWESTERLY AT 55-65 KT AT 5000 FT. FRIDAY NIGHT INTO SAT MORNING...HIGH CONFIDENCE. MVFR AND IFR CONDITIONS IN WIDESPREAD SHOWERS. AREAS OF FOG. SATURDAY AFTERNOON...HIGH CONFIDENCE. VFR.
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&& .MARINE...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. .SHORT TERM /TODAY THROUGH TUESDAY/...HIGH CONFIDENCE. THROUGH TODAY... W WINDS WILL GUST 20-25 KT THROUGH ABOUT MID DAY. THIS WILL ALLOW SEAS OFFSHORE TO GRADUALLY DIMINISH. THEREFORE...CURRENT ONGOING SMALL CRAFT ADVISORIES ARE LIKELY TO BE ALLOWED TO EXPIRE. TONIGHT INTO TOMORROW... LOW PRES WILL SLIDE S OF THE WATERS. WINDS WILL SHIFT FROM THE W TO N EARLY WED MORNING WITH GUSTS INCREASING AS THEY SHIFT WITH GUSTS AROUND 25 KT POSSIBLE. SEAS ALSO INCREASE SUCH THAT 5-7 FT SEAS ARE POSSIBLE DURING THE DAY ON WED. THEREFORE...AFTER A BRIEF LULL TODAY...SMALL CRAFT ADVISORIES ARE LIKELY NEEDED LATE TONIGHT...BUT WITH ONGOING HEADLINE WILL HOLD OFF FOR NOW OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY... WEDNESDAY NIGHT AND THURSDAY...SEAS DIMINISH AS HIGH PRESSURE BUILDS OVER THE WATERS. NORTHWESTERLY WINDS SHIFT TO THE SOUTHWEST DIMINISHING THROUGH THE PERIOD. OCCASIONAL 25 KT GUSTS ARE POSSIBLE ON THE OUTER WATERS AT TIMES. THURSDAY NIGHT THROUGH SATURDAY...SEAS INCREASE AHEAD OF A COLD FRONT WHICH STALLS OVER SOUTHERN NEW ENGLAND...AND THEN AS A STORM SYSTEM DEVELOPS ALONG THE FRONT AND MOVES INTO THE GULF OF MAINE. SOUTHWESTERLY WINDS 15 TO 25 KTS WITH GUSTS TO 30 KTS THROUGHOUT THE PERIOD...SHIFTING TO THE TO THE NORTHWEST SATURDAY MORNING. SMALL CRAFT ADVISORIES ARE LIKELY FOR BOTH WINDS AND SEAS AT LEAST ON THE OUTER WATERS...IF NOT ON THE INTERIOR BAYS AND SOUNDS AT TIMES. LOW PROBABILITY OF A GALE FORCE GUST OR TWO OVER THE OUTER WATERS.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ231-232-251. SMALL CRAFT ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR ANZ235- 237. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ250- 254-255. SMALL CRAFT ADVISORY UNTIL 5 PM EDT THIS AFTERNOON FOR ANZ256. && $$ SYNOPSIS...DOODY/GAF NEAR TERM...DOODY SHORT TERM...DOODY LONG TERM...GAF AVIATION...DOODY/GAF MARINE...DOODY/GAF

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