Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 310829 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 329 AM EST SAT JAN 31 2015 .SYNOPSIS...
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BLUSTERY AND VERY COLD CONDITIONS CONTINUE THROUGH THE WEEKEND. A MAJOR WINTER STORM WILL AFFECT THE REGION SUNDAY NIGHT INTO MONDAY EVENING WITH POTENTIALLY HEAVY SNOW ACCUMULATION AND GUSTY WINDS. A FRIGID AIRMASS WILL FOLLOW MONDAY NIGHT WITH DANGEROUSLY COLD WIND CHILLS. MODERATING TEMPS WEDNESDAY THEN VERY COLD CONDITIONS WILL RETURN TOWARD THE END OF THE WEEK. A COASTAL STORM WILL PASS WELL SOUTH OF NEW ENG LATE IN THE WEEK BUT WILL HAVE TO BE MONITORED.
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&& .NEAR TERM /THROUGH TODAY/...
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MID LEVEL LOW CLOSING OFF NEAR CAPE COD WITH BANDS OF LIGHT SNOW ROTATING BACK ACROSS E MA. HIGHER REFLECTIVITIES ARE DEVELOPING ON RADAR ACROSS E COASTAL MA AND THE ADJACENT WATERS INDICATING STEADIER SNOW. MODEL GUIDANCE SUGGEST SOME QPF ENHANCEMENT OVER THE OUTER CAPE THROUGH THE MORNING WITHIN THE DEVELOPING COMMA HEAD. MAIN FOCUS FOR MINOR ACCUM THROUGH MID MORNING WILL BE ACROSS CAPE ANN AND THE OUTER CAPE WHERE 1-2 INCHES IS POSSIBLE. LOW PROB FOR ISOLD 3 INCH AMOUNTS OUTER CAPE. ELSEWHERE ACROSS E MA...MAINLY A COATING TO ONE HALF INCH. AREAS OF LIGHT SNOW WILL LINGER ACROSS E MA INTO THE MORNING...EXITING THE OUTER CAPE BY MIDDAY. CLEARING SKIES DEVELOP ACROSS E NEW ENG LATER THIS MORNING INTO THE AFTERNOON...WITH FULL SUNSHINE ACROSS THE WEST. STRONG NW WINDS WILL CONTINUE TODAY. GUSTS 35-45 MPH EXPECTED WITH A FEW GUSTS NEAR 50 MPH NEAR THE COAST. BITTER COLD WIND CHILLS DOWN TO -10 TO -20 THIS MORNING ACROSS CENTRAL AND W NEW ENG AND -5 TO -10 IN THE COASTAL PLAIN. AFTERNOON HIGH TEMPS ONLY IN THE TEENS MOST LOCATIONS BUT WITH THE STRONG WINDS...WIND CHILLS WILL ONLY RECOVER TO -5 TO +5.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM SUNDAY/...
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TONIGHT... WEAK SFC RIDGE MOVES INTO THE REGION AHEAD OF ARCTIC FRONT DROPPING INTO N NEW ENG. THIS WILL RESULT IN GRADUAL DIMINISHING WINDS TONIGHT...BUT REMAINING RATHER GUSTY OVER THE CAPE/ISLANDS THROUGH THE NIGHT. MIN TEMPS WILL DROP INTO THE SINGLE NUMBERS WITH TEENS ALONG THE IMMEDIATE COAST AND CAPE/ISLANDS. SUNDAY... ARCTIC FRONT WILL PUSH S INTO SNE REACHING THE S COAST BY EVENING. SUNSHINE WILL GIVE WAY TO INCREASING CLOUDS IN THE AFTERNOON AS OVERRUNNING MID/HIGH CLOUDS MOVE INTO THE REGION...ALONG WITH DEVELOPMENT OF SOME LOWER CLOUDS AS LOW LEVEL MOISTURE INCREASES. BUT REMAINING DRY THROUGH THE DAY. HIGH TEMPS MOSTLY IN THE MID/UPPER 20S BUT DROPPING BACK INTO THE TEENS TOWARD EVENING ACROSS N ZONES AS ARCTIC AIR BEGINS TO DRAIN SOUTH.
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&& .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... */ SATURDAY NIGHT THROUGH MONDAY NIGHT... HIGHLIGHTS... - PLOWABLE SNOW ANTICIPATED FOR SUNDAY NIGHT INTO MONDAY NIGHT - IMPACTS TO TRAVEL DURING THE MONDAY MORNING/AFTERNOON COMMUTE - ENOUGH CONFIDENCE FROM CONSENSUS TO GO WITH A WINTER STORM WATCH - WINTER STORM WATCH IN EFFECT FOR LOCALES ALONG AND S OF MASS-PIKE OVERVIEW... MODERATE CONFIDENCE FORECAST. AND HERE WE GO AGAIN WITH A STORM. GOING DOWN ALL THE GUIDANCE EVER KNOWN. LIKE A DRIFTER I AM LOST ABOUT THIS STORM. SO I`VE MADE UP MY MIND. I`M ENSEMBLE BLENDING THIS TIME. SO HERE WE GO AGAIN. WITH THIS FORECAST AM NOT GOING TO INVEST IN ONE INDIVIDUAL STOCK OF FORECAST GUIDANCE. WILL DIVERSIFY WITH A PORTFOLIO BLEND OF ENSEMBLE WEIGHTED GUIDANCE...EVALUATING RISKS AND POTENTIAL IMPACTS WHICH ARE OUTLINED IN THE DISCUSSION BELOW. NEUTRAL-TILT OPEN-WAVE TROUGH ABOVE H85 SWEEPS ACROSS S NEW ENGLAND SUNDAY NIGHT-MONDAY NIGHT...PROGRESSING TOWARDS A NEGATIVE-TILT LATE IN THE PERIOD. SURFACE LOW EMERGES FROM THE OHIO RIVER VALLEY MONDAY MORNING SWEEP S OF NEW ENGLAND MONDAY-MONDAY NIGHT AS IT INTENSIFIES IN RESPONSE TO THE ISALLOBARIC WIND ENHANCING THE BAROCLINIC ZONE IN OUR PROXIMITY AND THE TROUGH ALOFT UNDERGOING NEGATIVE-TILT. FOCUS IS WITHIN THE ANTICYCLONIC BRANCH OF THE WARM-CONVEYER-BELT /WCB/ WHERE A BAROCLINIC-LEAF SETUP IS ANTICIPATED WITH BROADSCALE ISENTROPIC/DEEP-LAYER FORCING BENEATH RRQ/LFQ JET COUPLING OF UPPER- LEVEL JET STREAKS. CONVERGENCE OF THE WCB ALONG N-S SLANTWISE ASCENT AGAINST TIGHTENING ISOTHERMAL PACKING /SUBSEQUENT OF THE ENHANCEMENT OF THE BAROCLINIC ZONE/ WILL LIKELY YIELD E-W MESOSCALE BANDING OUT AHEAD OF THE STORM AND NOTABLY WITHIN THE NE-QUADRANT OF THE H85 LOW IN REGIONS OF STRONG FRONTOGENESIS. NEIGHBORING -EPV /POTENTIAL INSTABILITY/ THERE IS THE INDICATION AS SUGGESTED BY SREF MEANS OF SNOWFALL RATES OF AROUND 1 INCH PER HOUR. YET UNCERTAINTY... BUT WHERE EXACTLY ALL THESE INGREDIENTS COME TOGETHER AND WHERE THE GREATEST AMOUNT OF FORCING LIES REMAINS SUSPECT. ASSOCIATED ENERGY IS JUST COMING ASHORE IN BRITISH COLUMBIA CANADA AND THERE IS SOME QUESTION AS TO THE S-STREAM ENERGY THAT IS CAPTURED FROM THE LOW CENTER OVER THE SW CONUS / MEXICO. LOTS OF UNCERTAINTY GIVEN BY THE LATITUDINAL / ENHANCEMENT SPREAD OF FORECAST GUIDANCE UPSTREAM OVER THE OHIO RIVER VALLEY. JUST LIKE THE RUN-UP TO THE RECENT BLIZZARD MODELS VARY IN PLACEMENT OF BEST E-W BANDING AND THERMAL PROFILES. SUBTLE SHIFTS EVEN ON THE ORDER OF 5 TO 10 MILES WILL RESULT IN SIGNIFICANT SNOWFALL AMOUNTS AND PRECIP-TYPES. EVALUATING SPC SREF PLUMES SHOW GRAPHICALLY JUST THAT EXTENT OF SPREAD OF POSSIBILITIES. ITS INCREDIBLY DIFFICULT TO NAIL THE SPECIFICS DOWN AT THIS TIME BUT FEEL THAT THERE IS ENOUGH WEIGHTING TO GO WITH A WINTER STORM WATCH. WISH TO BETTER INFORM/ALERT BOTH THE PUBLIC AND STATE / LOCAL GOVTS. FEEL MESSAGING THE THREAT PRIOR TO THE WEEKEND AND THE FACT THAT THERE IS A TON OF SNOW ON THE GROUND GIVES EVERYONE TIME TO PREPARE AND TO ACT ACCORDINGLY FOR THE POTENTIAL OF A SIGNIFICANT SNOWFALL. NO TWO STORMS ARE ALIKE JUST LIKE NO TWO SNOWFLAKES ARE ALIKE. YET WE CAN DRAW COMPARISONS FROM ANALOGS. NOTING CIPS-ANALOGS...FROM THE 60-HR NAM-FORECAST AND 72-HR GFS-FORECAST...BOTH KEY UPON A SWATH OF E-W SNOW ACROSS THE NE-CONUS WITH AT LEAST 60% OF ANALOGS AGREEING UPON STORM-TOTAL SNOWFALLS IN EXCESS OF 8-INCHES...AND YES NOTING THAT THE MEAN-MEDIAN E-W SNOWFALL IS N OF THE MASS-PIKE. WHAT IS IMPORTANT TO TAKE AWAY IS THAT IT IS THERE AND THE PROBABILITIES SUGGEST SEEING SNOWFALLS IN EXCESS OF WATCH-WARNING CRITERIA. OTHER- WISE ALONG THE S-FRINGE OF THE BANDING IS THE LIKELIHOOD OF SEEING MIXING WITH A FREEZING RAIN POTENTIAL. PERHAPS SOME STRONG GUSTS ACROSS THE CAPE / ISLANDS IN EXCESS OF 35 MPH...OTHERWISE MAJORITY OF ANALOGS SIGNAL NO ISSUE WITH WINDS. SNOW... MODELS DIFFER ON N-S PLACEMENT OF E-W BANDING. JUST TOO FAR OUT AND TOO MUCH UNCERTAINTY TO MAKE ANY SPECIFIC GUESSES. WENT WITH A BROAD SPREAD BASED ON ENSEMBLE MEANS AND ANALOGS. WOULD VENTURE TO BELIEVE THAT THE HEAVY SNOW POTENTIAL AND HIGHEST ACCUMULATIONS WILL EXIST AROUND AND S OF THE MASS-PIKE IN LINE WITH WPC-THINKING. AMOUNTS UP TO A FOOT ARE POSSIBLE...SOME OF THIS DEPENDENT ON THE FLUFF-FACTOR OF THE SNOW. SNOW-RATIOS ANTICIPATED TO BE HIGHER S TO N WITH LESSER INTRUSION OF WARMER AIR ALOFT AROUND H8. SO WOULD FIGURE A MORE WET- SNOW TO THE S...FLUFFIER N. CAN NOT RULE OUT THUNDERSNOW POTENTIAL BUT BELIEVE THE LESS CHANCES IN COMPARISON TO THE RECENT BLIZZARD. MAIN TAKE-AWAY: TRAVEL WILL BE IMPACTED DURING BOTH THE MORNING AND EVENING COMMUTE ON MONDAY. MOTORISTS SHOULD BE AWARE OF ADVERSE WEATHER CONDITIONS THAT WILL BE CHANGING THROUGH THE EVENT WITH RESPECT TO THE PACE OF SNOWFALL AND POSSIBLE NEAR-ZERO VISIBILITIES. PRECIPITATION-TYPE MAY ALSO CONTEND WITH A E-W MIXING LINE IN PROXIMITY TO THE S-SHORE. WARM INTRUSION AROUND H8 PUSHED N BY WCB MAY LEND TO A TRANSITION OF RAIN/SNOW WITH PERHAPS A WINTRY MIX BETWEEN OF FREEZING RAIN/SLEET ALBEIT THINKING VERY THIN. FOCUS OF THE NARROW BAND OF MIXING WOULD OCCUR WITH THE APPROACH AND PASSAGE OF THE LOW IN PROXIMITY TO S NEW ENGLAND DURING THE AFOREMENTIONED TIMEFRAME. FORECAST GUIDANCE SPLIT BUT QUESTION WHETHER A MICRO-CLIMATE AND THE ARCTIC AIR SPILLING S WILL KEEP US ALL SNOW. ALTOGETHER...MAIN FOCUS FOR POTENTIAL WINTRY MIX...IF ANY...IS ALONG THE IMMEDIATE S-SHORE. WINDS... BLUSTERY OUT OF THE N IN RESPONSE TO THE APPROACHING / DEEPENING LOW PRESSURE CENTER THROUGH THE DAY MONDAY INTO MONDAY EVENING. WILL SEE STRONG NW-WINDS IN WAKE OF THE STORM. COULD BE CONTENDING WITH GUSTS ON THE ORDER OF AROUND 20-30 MPH FOR SOME LOCATIONS...ESPECIALLY FOR THE SHORES. ADDING TO THE POTENTIAL FLUFF-FACTOR OF THE SNOW...THAT ADDS TO THE POTENTIAL OF BLOWING AND DRIFTING WHICH HAS THE IMPACT OF GENERATING NEAR-ZERO VISIBILITIES. TAKE-AWAY: AT THIS TIME IT APPEARS WINDS WILL REMAIN BELOW WIND-ADV CRITERIA. COASTAL FLOODING... MID-MORNING HIGH TIDES ARE NOT ASTRONOMICALLY HIGH AND LATE-EVENING TIDES ARE MUCH LOWER. ESTIMATING AROUND A FOOT OF SURGE IN RESPONSE TO THE STORM...LOW CONFIDENCE AT THIS TIME OF ANY COASTAL FLOODING. */ TUESDAY ONWARD... HIGHLIGHTS... - ANOTHER ROUND OF SNOW POSSIBLE THURSDAY-FRIDAY; LOW CONFIDENCE OVERVIEW... COLD HIGH PRESSURE IS FORECAST TO MOVE OVER NEW ENGLAND ON TUESDAY BEHIND THE DEPARTING STORM WITH HIGHS ONLY FORECAST TO MAKE IT INTO THE TEENS MOST LOCALES. NEXT IN THE SERIES OF SHORTWAVES IS SHOWN BY THE GLOBAL MODELS TO MOVE ONSHORE THE NW PACIFIC COAST TUE NIGHT. THIS LOOKS TO BE THE NEXT PIECE OF ENERGY TO WATCH IN THE LONG TERM. GFS/ECMWF SHOW COASTAL LOW DEVELOPMENT OCCURRING WED NIGHT OR THU /SLIGHTLY DELAYED FROM MODEL RUNS YESTERDAY/ AND THREATENING YET ANOTHER IMPACT TO NEW ENGLAND CENTERED ON THE THU-FRI TIMEFRAME. LARGE SPREADS IN THE MODELS/ENSEMBLES...NO SURPRISE 6-7 DAYS OUT IN TIME. THE MEAN SHOWS A WEAKER STORM COMPARED TO THE MONDAY ONE...WITH THE LATEST 30.12Z OPERATIONAL RUNS EITHER A GLANCING BLOW OR A COMPLETE MISS. TOO SOON THOUGH TO LEAN ON A HIT OR A MISS TO SOUTHERN NEW ENGLAND. BITTER COLD LOOKS TO FOLLOW IN THE WAKE OF THIS POTENTIAL LATE WEEK STORM. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM.../THROUGH SUNDAY/...HIGH CONFIDENCE. THROUGH TODAY...N-S BAND OF -SN WITH MVFR CONDITIONS WILL BE CONFINED TO E MA SHIFTING TO JUST CAPE COD AFT 12Z BEFORE ENDING BY MIDDAY OVER THE OUTER CAPE. OTHERWISE...VFR WITH CLEARING SKIES IN EASTERN NEW ENG. NW GUSTS TO 30-40 KT. TONIGHT...VFR WITH GRADUAL DIMINISHING WIND. SUNDAY...MAINLY VFR...BUT LOW PROB FOR AREAS OF MVFR CIGS DEVELOPING IN THE AFTERNOON. KBOS TAF...HIGH CONFIDENCE. MVFR VSBYS DUE TO LIGHT SNOW AND BLOWING SNOW EARLY THIS MORNING. IMPROVING CONDITIONS AFT 12Z. KBDL TAF...HIGH CONFIDENCE. OUTLOOK /SUNDAY NIGHT THROUGH TUESDAY/... SUNDAY NIGHT INTO MONDAY NIGHT...MODERATE CONFIDENCE. DETERIORATING CONDITIONS TO IFR-VLIFR WITH SNOW. BLUSTERY N-WINDS WITH GUSTS UP TO AROUND 30 KTS. CONDITIONS IMPROVE LATE AS WINDS BACK NW. TUESDAY...MODERATE CONFIDENCE. MAINLY VFR. MAY SEE GUSTY NW WINDS EARLY. WEDNESDAY...MODERATE CONFIDENCE. VFR. && .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 /THROUGH SATURDAY NIGHT/...HIGH CONFIDENCE. TODAY...GALE CENTER LIFTS INTO THE MARITIMES WITH NW GALES CONTINUING OVER THE WATERS. GUSTS TO 40-45 KT LIKELY WITH MODERATE FREEZING SPRAY LIKELY. SNOW SHOWERS REDUCE VSBY OVER EASTERN MA WATERS IN THE MORNING. TONIGHT...GALE CENTER PULLS FARTHER AWAY WITH WINDS DIMINISHING BELOW GALE 00-06Z...BUT GUSTS 25-30 KT WILL CONTINUE OVERNIGHT. MODERATE FREEZING SPRAY LIKELY CONTINUING...ESPECIALLY E MA COASTAL WATERS. SUNDAY...WINDS AND SEAS GRADUALLY DIMINISH THROUGH THE DAY. SUB SCA CONDITIONS DEVELOP OVER THE S COASTAL WATERS DURING THE MORNING...BUT SCA CONDITIONS WILL CONTINUE ACROSS THE OUTER EASTERN WATERS. LIGHT FREEZING SPRAY WILL PERSIST. OUTLOOK /SUNDAY NIGHT THROUGH TUESDAY/... SUNDAY NIGHT INTO MONDAY NIGHT...MODERATE CONFIDENCE. AREA OF LOW PRESSURE SWEEPING W-E ACROSS THE S-WATERS. WILL SEE WINDS OUT OF THE N INCREASE TO GALE-FORCE. WAVES INCREASING 10-12 FEET ON THE S/SE WATERS AS THE STORM INTENSIFIES TO THE E AND WINDS BACK OUT OF THE NW LATE IN THE PERIOD. TUESDAY...MODERATE CONFIDENCE. NW WINDS RELAX AROUND DEPARTING STORM WITH SEAS SUBSIDING... THOUGH STILL FORECAST TO REMAIN AT SMALL CRAFT ADVISORY LEVELS. WEDNESDAY....MODERATE CONFIDENCE. WINDS FORECAST TO TURN SW AND PICK UP WITH SEAS INTO SMALL CRAFT ADVISORY LEVELS AGAIN. FEW SNOW SHOWERS POSSIBLE.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...WINTER STORM WATCH FROM SUNDAY EVENING THROUGH LATE MONDAY NIGHT FOR CTZ002>004. WIND CHILL ADVISORY UNTIL 9 AM EST THIS MORNING FOR CTZ002-003. MA...WIND ADVISORY UNTIL 9 PM EST THIS EVENING FOR MAZ022>024. WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR MAZ007-015-016- 019>021. WINTER STORM WATCH FROM SUNDAY EVENING THROUGH LATE MONDAY NIGHT FOR MAZ009-011>013-015>022. WIND CHILL ADVISORY UNTIL 9 AM EST THIS MORNING FOR MAZ003-004- 010-011. WIND CHILL ADVISORY UNTIL 11 AM EST THIS MORNING FOR MAZ002- 008-009. WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR MAZ022. RI...WIND ADVISORY UNTIL 9 PM EST THIS EVENING FOR RIZ008. WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR RIZ005>007. WINTER STORM WATCH FROM SUNDAY EVENING THROUGH LATE MONDAY NIGHT FOR RIZ001>007. MARINE...FREEZING SPRAY ADVISORY UNTIL 6 AM EST SUNDAY FOR ANZ231-232- 250-251. GALE WARNING UNTIL 1 AM EST SUNDAY FOR ANZ231-232-250-251- 254>256. FREEZING SPRAY ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ233>235-237. GALE WARNING UNTIL 10 PM EST THIS EVENING FOR ANZ233>235-237. GALE WARNING UNTIL 9 PM EST THIS EVENING FOR ANZ230. GALE WARNING UNTIL 6 PM EST THIS EVENING FOR ANZ236.
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&& $$ SYNOPSIS...KJC NEAR TERM...KJC SHORT TERM...KJC LONG TERM...SIPPRELL AVIATION...KJC/SIPPRELL MARINE...KJC/SIPPRELL

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