Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 042123 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 423 PM EST WED MAR 4 2015 .SYNOPSIS... WEAK LOW PRESSURE WILL PUSH ALONG THE STALLED FRONT WITH ANOTHER ROUND OF SNOW TONIGHT INTO THURSDAY. HIGH PRESSURE WILL BUILD IN FOR FRIDAY THROUGH THIS WEEKEND...BRINGING DRY CONDITIONS WITH COLDER THAN NORMAL TEMPERATURES. A WEAKENING FRONT MAY BRING SOME LIGHT SNOW SHOWERS ON MONDAY. ANOTHER COLD FRONT MAY APPROACH TOWARD THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 225 PM UPDATE... * TRENDING FORECAST A BIT LOWER FOR SNOWFALL TOTALS * WINTER STORM WARNING REMAINS POSTED FOR ISLANDS...CONVERTING WATCH TO WINTER WEATHER ADVISORY ALONG S COAST * NORTHERN EXTENT OF SNOW REMAINS QUESTIONABLE RADAR MOSAIC SHOWS PATCHES OF LIGHT RAIN /OR SPRINKLES/ HEADING ALONG S COAST THIS AFTERNOON. EXPECT THIS TO CONTINUE THROUGH THIS EVENING AS ADDITIONAL ACTIVITY ACROSS PA/NJ HEADS IN OUR DIRECTION. SOME BREAKS OR THINNING IN CLOUD COVER HAS ALLOWED TEMPERATURES TO REBOUND THIS AFTERNOON INTO 30S AND 40S...A TESTAMENT TO EARLY MARCH SUN WHICH WE OFTEN UNDERESTIMATE THIS TIME OF YEAR. IN FACT IT IS MORE REMINISCENT OF SPRING AS COOLEST TEMPERATURES ARE ALONG S COAST...CAPE COD AND ISLANDS WHERE FOG/ LOW CLOUDS PREVAIL. COLD FRONT CONTINUES TO MAKE SLOW PROGRESS THROUGH SOUTHERN NEW ENGLAND AND WILL HEAD OFF S COAST TONIGHT. THIS WILL SET STAGE FOR OUR NEXT ROUND OF SNOW AS COLUMN COOLS FROM NW TO SE DURING NIGHT. CONFIDENCE IS MEDIUM AT BEST GIVEN CONCERNS ABOUT HOW FAST THIS COOLING TAKES PLACE NEAR S COAST WHICH AFFECTS TIMING OF CHANGEOVER TO SLEET/SNOW AS WELL AS HOW MUCH CAN ACCUMULATE. OUR THINKING IS CHANGE TO SNOW WILL OCCUR FROM HARTFORD TO BOSTON BETWEEN 9 PM AND 11 PM...PROVIDENCE TO PLYMOUTH CLOSER TO MIDNIGHT...AND ON CAPE/ISLANDS AROUND 2 OR 3 AM. CROSS SECTIONS SHOW POTENTIAL FOR DECENT BURST OF SNOW OVERNIGHT...WHICH IS MAINLY FOCUSED S OF MASS PIKE /AND ESPECIALLY NEAR S COAST/. CONSENSUS OF 12Z MODELS HAVE NUDGED THINGS A BIT FARTHER S FROM EARLIER RUNS...ESPECIALLY HIGH-RES MODELS WHICH SHOW SHARP CUTOFF TO NORTHERN EDGE OF PRECIPITATION SHIELD WHICH HAS TO BE TAKEN INTO CONSIDERATION. 12Z ECMWF REMAINS A BIT FARTHER N WITH ITS AXIS OF QPF WHICH PREVENTS US FROM TAKING EVERYTHING TOO FAR OFFSHORE. IN COORDINATION WITH WPC AND NEIGHBORING OFFICES...WE WILL NUDGE SNOWFALL TOTALS DOWN A TAD WITH FOCUS OF HIGHEST AMOUNTS ALONG S COAST/CAPE COD AND ESPECIALLY ISLANDS. WE WILL MAINTAIN WINTER STORM WARNING FOR ISLANDS /4 TO 7 INCHES/. OUR HIGHEST CONFIDENCE IS ON LOWER END OF THAT RANGE BASED UPON MODEL CONSENSUS. WE WILL CONVERT WINTER STORM WATCH ON S COASTAL RI/MA TO WINTER WEATHER ADVISORY /2 TO 5 INCHES/ WITH HIGHER TOTALS FOCUSED ON COAST AND CAPE COD AND LOWER END OF RANGE CLOSER TO PROVIDENCE. THERE ARE SEVERAL RED FLAGS TO CONSIDER AGAINST GOING WITH OVERLY HIGH AMOUNTS INCLUDING BEING ABLE TO OVERCOME INITIALLY WARM LOW LEVEL TEMPERATURES...CONTINUED SOUTHWARD NUDGE ON MODELS AND FACT THAT BEST LIFT IN MAX SNOW GROWTH ZONE IS LIMITED TO LATE TONIGHT AND EARLY THU MORNING NEAR S COAST. FACT THAT HIGH-RES MODELS SHOW LITTLE IF ANY SNOWFALL N OF MASS PIKE MAKES SENSE GIVEN WE EXPECT A SHARP GRADIENT ON NORTHERN EDGE OF SYSTEM...SO IF ANYTHING SNOWFALL TOTALS ALONG AND N OF MASS PIKE MAY BE A BIT OVERDONE. NOTE PROBABILISTIC SNOW FORECASTS WILL SHOW RATHER LARGE RANGE /IE FEW INCHES TO NEARLY A FOOT ON NANTUCKET/ DUE TO UNCERTAINTY IN TEMPERATURE PROFILE AND TO SOME DEGREE HOW FAR CLOSE OR OFFSHORE DOES AXIS OF HEAVIEST QPF LIE. THIS LEADS US TO PLAY FORECAST MORE CONSERVATIVELY DUE TO REASONS MENTIONED ABOVE. FOR THOSE WONDERING ABOUT BOS SNOWFALL RECORD...WE NEED 1.9 INCHES TO TIE 1995-96. OUR LATEST FORECAST HAS ABOUT 0.7 INCH AT BOS. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... FOCUS FOR STEADIER SNOWFALL WILL BE OVER SE NEW ENGLAND THU MORNING WITH RAPID DRYING FROM NW BRINGING CLEARING TO INTERIOR BY AFTERNOON. EXPECT ADDITIONAL 2 TO 4 INCHES DURING DAY ACROSS S COASTAL RI/MA AND CAPE COD/ISLANDS WITH LESS THAN INCH AS FAR N AS MASS PIKE. DEFINITELY COLDER DAY AHEAD WITH HIGHS ONLY IN 20S EXCEPT NEAR 30 ON CAPE AND ISLANDS. CLEARING SETS IN ACROSS ALL OF REGION THU NIGHT AS SYSTEM HEADS FARTHER OUT TO SEA AND HIGH PRESSURE BUILDS IN. ANOTHER SHOT OF BITTERLY COLD AIR ARRIVES WITH LOWS FROM ABOUT 5 BELOW TO 5 ABOVE ACROSS INTERIOR TO TEENS CLOSER TO COAST. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... * HIGH PRESSURE ARRIVES FRIDAY * MOISTURE-STARVED COLD FRONT MOVES THROUGH THIS WEEKEND * UNCERTAIN FORECAST EARLY NEXT WEEK MODELS ARE IN FAIRLY GOOD AGREEMENT GOING INTO THIS WEEKEND. THERE ARE SOME MINOR DISCREPANCIES IN TIMING OF A COLD FRONT INTO THIS WEEKEND. MORE SIGNIFICANT DIFFERENCES DEVELOP SATURDAY NIGHT INTO SUNDAY. THE GFS IS VERY AGGRESSIVE IN DEVELOPING A SURFACE LOW NEAR THE GREAT LAKES...AND IS OFF ON ITS OWN IN DOING SO. AT THIS POINT...AM FAVORING A CONSENSUS BLEND OF THE OTHER GUIDANCE DUE TO FAIRLY BROAD MID-LEVEL TROUGH OVER THE NORTHEAST. HIGH PRESSURE SOUTH OF NEW ENGLAND IS THE MAIN THEME EARLY NEXT WEEK. THERE IS SOME QUESTION AS TO HOW CLOSE A COLD FRONT CAN GET TO SOUTHERN NEW ENGLAND TOWARD MID WEEK. FRIDAY...A HIGH PRESSURE BECOMES SUPPRESSED TO OUR SOUTH AS A LOW PRESSURE MOVES INTO QUEBEC. THIS WILL KEEP LOWER TEMPERATURES... WELL BELOW NORMAL FOR EARLY MARCH...IN PLACE FOR SOUTHERN NEW ENGLAND. THIS WEEKEND...A SHORTWAVE PUSHES LOW PRESSURE THROUGH QUEBEC...ALLOWING A COLD FRONT TO MOVE THROUGH SOUTHERN NEW ENGLAND. AT THIS POINT...THIS FRONTAL PASSAGE APPEARS TO BE FAIRLY MOISTURE- STARVED...SO LITTLE IF ANY PRECIP WILL ACCOMPANY THIS FRONT. TEMPERATURES MODERATE A BIT...BUT REMAIN WELL BELOW NORMAL. EARLY NEXT WEEK...MODELS CONTINUE TO SHOW SIGNIFICANT DIFFERENCES WITH THE EVOLUTION OF THE MID LEVEL FLOW. 04/12Z GFS IS FASTER TO WARM UP THE LOWER ATMOSPHERE THAN BOTH ITS ENSEMBLE MEAN AND THE 04/12Z ECMWF. WHILE THINKING TEMPERATURES WILL EVENTUALLY BECOME HIGHER...AM NOT YET SOLD ON THE GFS TIMING. THIS WILL HAVE IMPLICATIONS FOR PRECIPITATION TYPE. WILL CONTINUE TO FAVOR A CONSENSUS APPROACH FOR THIS TIME RANGE. && .AVIATION /21Z WEDNESDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY NIGHT/...MODERATE CONFIDENCE. MVFR/IFR PERSISTS ALONG S COAST...CAPE COD AND ISLANDS THROUGH THIS EVENING WITH ISOLATED LIGHT SHOWERS. CIGS MAY IMPROVE SLIGHTLY AFTER 00Z BUT OVERALL TREND IS TO MAINTAIN PERSISTENCE IN CONDITIONS. VFR CIGS ELSEWHERE. MVFR/IFR SPREADS N IN LIGHT SNOW TONIGHT...PROBABLY AS FAR N AS BDL-SFZ-BOS MAINLY DUE TO VSBY. LIGHT RAIN CHANGES TO SLEET AND SNOW CLOSER TO S COAST AFTER 06Z WHERE LIFR EXPECTED THROUGH DAYBREAK THU. VFR CIGS FARTHER N AND W. CONDITIONS SLOWLY IMPROVE THU FROM NW TO SE...WITH CAPE COD AND ISLANDS LAST TO IMPROVE 16Z-20Z. SNOW ACCUMULATIONS... BOS/BAF/BED/ORH...1 INCH BDL/PVD...2 INCHES FMH/HYA...3-4 INCHES ACK...5-7 INCHES KBOS TAF...HIGH CONFIDENCE. COORDINATED TAF WITH CWSU ZBW. KBDL TAF...HIGH CONFIDENCE. OUTLOOK...FRIDAY THROUGH MONDAY... MODERATE CONFIDENCE. MAINLY VFR THROUGH THIS PERIOD. BRIEF MVFR CONDITIONS ARE POSSIBLE SATURDAY NIGHT INTO MONDAY ACROSS THE NORTHWEST THIRD OF SOUTHERN NEW ENGLAND IN SCATTERED SNOW SHOWERS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY NIGHT/...MODERATE CONFIDENCE. MAINTAINING SCA ON OUTER WATERS AND BLOCK ISLAND/RI SOUNDS PRIMARILY DUE TO SEAS THROUGH THU OR THU NIGHT. COLD FRONT SLOWLY DROPS S TONIGHT WITH WIND SHIFT TO NW AND POSSIBLY A FEW GUSTS TO 25 KT. SPOTTY LIGHT RAIN WILL GIVE WAY TO SLEET AND SNOW LATE TONIGHT...WITH LOWEST VSBY FROM MIDNIGHT INTO THU MORNING. SNOW SHOULD MAINLY AFFECT S COASTAL WATERS THU BEFORE HEADING OFFSHORE THU NIGHT. HIGH PRESSURE BUILDING IN TO REGION MAY BRING PERIOD OF 25KT NW WIND GUSTS THU NIGHT...MAINLY ON OUTER WATERS. OUTLOOK...FRIDAY THROUGH MONDAY... HIGH CONFIDENCE. WINDS AND SEAS SLOWLY DIMINISH FRIDAY AS HIGH PRESSURE BUILDS OVER THE WATERS. THEY THEN INCREASE AGAIN...BUT ONLY MODESTLY OVER THIS WEEKEND AS A COLD FRONT APPROACHES...THEN CROSSES THE WATERS. SMALL CRAFT ADVISORIES WILL LIKELY BE NECESSARY ON THE OUTER WATERS FOR A PORTION OF THIS TIME. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 7 PM EST THURSDAY FOR MAZ023-024. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 PM EST THURSDAY FOR MAZ020>022. RI...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 7 PM EST THURSDAY FOR RIZ008. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 PM EST THURSDAY FOR RIZ003>007. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST FRIDAY FOR ANZ235-237-250- 254>256. && $$ SYNOPSIS...BELK/JWD NEAR TERM...JWD SHORT TERM...JWD LONG TERM...BELK AVIATION...BELK/JWD MARINE...BELK/JWD

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