Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 232340 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 640 PM EST FRI JAN 23 2015 .SYNOPSIS...
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A COASTAL STORM WILL IMPACT MUCH OF THE REGION SATURDAY INTO SATURDAY NIGHT WITH HEAVY SNOW AND A WINTRY MIX ACROSS PARTS OF THE AREA. THE NEXT STORM IS EXPECTED TO TRACK WELL TO THE SOUTH ON MONDAY WITH MAINLY DRY AND UNSEASONABLY COLD CONDITIONS EARLY NEXT WEEK...WITH SOME OCEAN EFFECT SNOW SHOWERS ACROSS THE CAPE/ISLANDS AND SOUTHEAST MASSACHUSETTS. HIGH PRESSURE BUILDS INTO THE REGION LATE WEDNESDAY AND THURSDAY FOLLOWED BY A COLD FRONT NEXT FRIDAY.
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&& .NEAR TERM /UNTIL 3 AM SATURDAY MORNING/...
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645 PM UPDATE... SOME HIGH CLOUDS MOVING INTO SW NEW ENG...OTHERWISE SKC. CURRENT FORECAST ON TRACK. PREVIOUS DISCUSSION... A BRIEF PERIOD OF RADIATIONAL COOLING THIS EVENING BEFORE HIGH AND MID CLOUDS BEGIN TO SPILL OVER AND BECOME BKN- OVC BY MIDNIGHT. LEANED SLIGHTLY ON THE COOL SIDE OF THE MOS TEMPS FOR THE MINS OVERNIGHT TONIGHT. WILL HAVE TO WATCH THIS CLOSELY...AS THE OVERNIGHT MINS WILL LIKELY SOMEWHAT DICTATE THE ABILITY TO WARM /OR NOT/ AS PRECIP OVERSPREADS THE REGION DURING THE EARLY MORNING HOURS. THIS MAY ALTER CURRENT THINKING IN WHERE THE RAIN/SNOW/MIX LINES ULTIMATELY LIE.
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&& .SHORT TERM /3 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... *** COASTAL STORM BRINGS MIXED PRECIP...WINDS AND COASTAL FLOODING EARLY TOMORROW INTO TOMORROW EVENING *** HIGHLIGHTS... * STILL A BIT OF UNCERTAINTY. * BEST CHANCE FOR HEAVY SNOW NORTH OF THE MASS PIKE AND WEST OF RT 128...MAINLY IN THE WORCESTER HILLS TO SOUTHEAST NH AWAY FROM THE COAST. * SOME ICE ACCUMULATION POSSIBLE ACROSS NORTHERN CT...RI AND SOUTHERN MA. * STRONG WINDS FOR THE SOUTHEAST MA TOMORROW EVENING. OVERVIEW AND UNCERTAINTY... MODELS CONTINUE TO INDICATE RAPIDLY DEEPENING LOW PRES...BOMBING FROM 980 AND HEADING TOWARD 960 AS IT MOVES NE OF THE BENCHMARK SAT EVENING. WHILE THE TRACK IS GENERALLY WELL AGREED UPON /SLIGHTLY INSIDE THE 40/70 MARK/ A RECENT NW SHIFT IN QPF...BUT COLDER OVERALL PROFILES HAS BEEN NOTED...AND MAY BE LIKELY DUE TO MODELS BETTER REALIZING THE CONVECTION NEAR THE GULF AND BETTER RESULTING DOWNSTREAM RIDGING. GIVEN THIS...HAVE TRENDED TOWARD LATEST ECMWF FOR THIS UPDATE...GIVEN IT SPLITS THE DIFFERENCE WELL IN SHOWING THE COLDER NAM AND WARMER GFS...WITH A SLIGHT WEIGHT TOWARD THE COLDER SOLUTION. THE PRIMARY UNCERTAINTY REMAINS THE THERMAL PROFILES THOUGH...GIVEN THE LACK OF BLOCKING HIGH PRES WITH COLD AIR TO THE N...AN EVER SO SLIGHT AND LIKELY MESO-SCALE WAVER IS GOING TO SHIFT THE AXIS OF RAIN/SNOW/MIXED WINTRY PRECIP SOMEWHAT. SO EVEN THOUGH HAVE TRENDED GRIDS TOWARD SLIGHTLY HIGHER SNOW TOTALS GIVEN THE HIGHER QPF AND COLDER TREND...WILL STILL NEED TO WATCH CLOSELY WHERE THE AXIS SETS UP...FOR NOW CONFIDENCE IS HIGHEST WHERE WARNINGS WILL BE ISSUED...FROM NRN CT INTO NE MA...WITH ADVISORIES TAPERED TO EITHER SIDE. PRECIPITATION TIMING... SNOW TO START...WILL OVERSPREAD BETWEEN 3AM IN CT...TO 7 AM AT THE BORDER WITH NH. THEN...EXPECT A GRADUAL CHANGE OVER FROM THE S COAST TO A WINTRY MIX...AND EVEN ALL RAIN BETWEEN 7 AM AND NOON. THE PRECIP WILL LIKELY THEN PIVOT AT OR NEAR THE MASS PIKE TO ROUTE 128...AND BEGIN TO TRANSITION BACK TO ALL SNOW LATE AFTERNOON...ENDING AS A BRIEF PERIOD OF HEAVY SNOW AND GUSTY WINDS DURING THE EVENING EVERYWHERE. STRONGEST WINDS TIMING... MAINLY DURING THE LATE AFTERNOON AND EVENING HOURS. PRECIPITATION TYPE /WINTRY MIX/... EXPECT SNOWS TO BEGIN AFTER MIDNIGHT TONIGHT GIVEN THE COLD START. THIS WILL OVERSPREAD FROM ABOUT 2-3AM TO ABOUT 7AM FROM S-N GIVEN THE FASTER TIMING NOTED BY THE PREVIOUS FORECASTER. THEN...WARMER AIR WILL FORCE A TRANSITION TO A WINTRY MIX...INCLUDING SLEET...FREEZING RAIN AND ALL RAIN FROM S-N FROM THE S COAST TO ABOUT THE MASS PIKE...TO WHERE THE MASS PIKE AND RT 128 MEET. AREAS CLOSER TO THE COAST WILL LIKELY SEE A PERIOD OF ALL RAIN BY LATE MORNING AND AFTERNOON...WHILE AREAS CLOSER TO THE PIKE WILL REMAIN IN A WINTRY MIX AND POSSIBLY TRANSITION BACK AND FORTH. FOR THESE AREAS...MAINLY NORTHEASTERN CT...NORTHERN RI...AND MA AROUND AND S OF THE PIKE...SLEET AND FREEZING RAIN COULD YIELD UP TO AN 0.1 INCHES OF ICE ACCRETION. N OF THE MASS PIKE AND MAINLY OUTSIDE OF W OF 128...HAS THE BEST CHANCE FOR ALL SNOW...WITH THE HEAVIEST BAND DURING THE MORNING AND AFTERNOON SETTING UP FROM EXTREME NE CT THROUGH THE WORCESTER HILLS AND INTO SE NH...IN ESSENCE JUST NW OF THE RAIN/SNOW LINE. NOTE THIS MAY SHIFT HOWEVER...GIVEN THE UNCERTAINTY. DO HOWEVER...HAVE FAIRLY HIGH CONFIDENCE OF A BRIEF HEAVY BAND OF ALL SNOW AS HEIGHTS CRASH AND THE LOW WRAPS UP TOMORROW EVENING...SO EXPECT A LAST MINUTE TRANSITION TO BRIEF HEAVY SNOW WITH GUSTY WINDS DURING THE EVENING...EVEN IN THOSE AREAS IN AN ADVISORY OR WITHOUT A CURRENT HEADLINE. THIS COULD LEAD TO A RAPID CHANGE IN ROAD CONDITIONS AND LOW VISIBILITY BEFORE IT COMES TO AN END. ALL IN ALL...THE BEST CHANCE FOR ALL SNOW...AND THE BEST CHANCE FOR BANDING ARE IN ROUGHLY THE AREA OF THE CURRENT WATCH...SO WILL BE UPGRADING TO A WARNING...STATING THE CHANCE FOR 6+ AND EVEN POTENTIALLY 8+ INCHES IN SPOTS. SNOW RATIOS WILL BE LOW WHERE THE HEAVIEST BAND SETS UP...SO EXPECT THAT IT WILL BE HEAVY AND WET. STAY TUNED TO LATEST UPDATES FOR ANY CHANGES IN SNOW AXES. STRONG WINDS... AS THE LOW RAPIDLY DEEPENS AND MAKES IT/S CLOSEST PASS TOMORROW EVENING. EXPECT AN INCREASE IN WINDS ESPECIALLY AS THEY SHIFT FROM THE N PRIMARILY...TO THE NW. AM NOTING A ROBUST N-NE LLJ EXCEEDING 50 KT SKIRTING THE SE PORTION OF MA. WITHOUT THE HIGH PRES TO THE N...IT WILL BE MORE DIFFICULT THAN NORMAL TO GET THIS MOMENTUM TO THE GROUND. HOWEVER...BETTER MIXING ALONG THE OUTER ARM OF CAPE COD AND THE ISLANDS THANKS TO MARINE INFLUENCE COULD ALLOW SOME OF THIS TO MIX...SO WIND GUSTS OF 50 MPH ARE NOT OUT OF THE QUESTION THERE. THEREFORE...WILL ALSO HOIST A WIND ADVISORY WITH THIS UPDATE...WHICH MAY NEED TO BE EXPANDED SOMEWHAT INLAND...BUT JUST DON/T HAVE THE CONFIDENCE WITH THIS UPDATE. COASTAL FLOODING... SEE THE COASTAL FLOOD SECTION BELOW. TOMORROW NIGHT... AFTER THE BRIEF BURST OF SNOW/WIND EXPECT A BREEZY AND COLD NIGHT BEHIND THE EXITING LOW PRES ESPECIALLY AFTER MIDNIGHT. DEPENDING ON HOW QUICKLY THE WINDS ARE ABLE TO DRY AREA ROADWAYS AND SIDEWALKS...MAY NEED TO WATCH FOR SOME LEFTOVER PATCHY BLACK ICE AS TEMPS FALL BACK INTO THE UPPER TEENS AND 20S BY DAYBREAK SUN. && .LONG TERM /SUNDAY THROUGH FRIDAY/... HIGHLIGHTS... * DRY AND SEASONABLE SUNDAY * MAINLY DRY AND UNSEASONABLY COLD MONDAY THROUGH WEDNESDAY. * OCEAN EFFECT SNOW SHOWERS ACROSS THE CAPE/ISLANDS AND SE MA MON/TUE * MODERATING TEMPS TOWARD THE END OF THE WEEK OVERVIEW... PATTERN FEATURES A RIDGE IN THE WESTERN CONUS AND ACROSS THE NORTH ATLANTIC WITH FULL LATITUDE TROF ACROSS EASTERN US WHICH WILL BRING A SURGE OF UNSEASONABLY COLD CONDITIONS THROUGH MIDWEEK...ALBEIT MAINLY DRY. DETERMINISTIC GUIDANCE KEEPING MON STORM SUPPRESSED AND WELL SOUTH OF NEW ENG WITH MAINLY DRY CONDITIONS...HOWEVER AT LEAST HALF OF GFS ENSEMBLE MEMBERS ARE FURTHER N AND BRING SNOW INTO SNE MON NIGHT INTO TUE. ODDS FAVOR A MOSTLY DRY FORECAST BUT STILL NEED TO WATCH THIS STORM CLOSELY AS IT COULD STILL TREND BACK N. BY THE MIDDLE OF THE WEEK...WESTERN RIDGE BEGINS TO BREAK DOWN WHICH WILL LEAD TO A MODERATING TREND TOWARD THE LATTER HALF OF THE WEEK AS MODIFIED PACIFIC AIR GETS ENTRAINED INTO THE FLOW. SUNDAY... DRY WITH SEASONABLE TEMPS EXPECTED...ALTHOUGH IT WILL BE BLUSTERY WITH GUSTY W/NW WINDS. MONDAY AND TUESDAY... MODEL CONSENSUS FAVOR A SUPPRESSED STORM PASSING WELL S OF NEW ENG MON/MON NIGHT...HOWEVER THERE ARE STILL ENOUGH GFS ENSEMBLE MEMBERS THAT ARE FURTHER N SO CANT ENTIRELY RULE OUT THIS STORM. THERE REMAINS A LOW PROBABILITY THAT THIS STORM COULD HAVE A LARGER IMPACT ON SNE...BUT ODDS FAVOR A GLANCING BLOW OR A MISS. EVEN IF STORM IS A MISS...IT APPEARS OCEAN EFFECT SNOW SHOWERS WILL AFFECT CAPE/ISLANDS INTO PORTIONS OF SE MA. VERY COLD AIR MOVING IN WITH STEEP LOW LEVEL LAPSE RATES OVER THE OCEAN AND NE FLOW SUGGEST SOME LIGHT ACCUMULATION POSSIBLE FOR CAPE/ISLANDS AND COASTAL SE MA. UNSEASONABLY COLD BOTH DAYS WITH 925 MB TEMPS -12 TO -15C. HIGHS WILL LIKELY BE IN THE TEENS TO MID 20S MON AND POSSIBLY A FEW DEGREES COLDER TUE. EXPECT LOTS OF CLOUDS MON AND TUE...BUT INCREASING SUNSHINE IN THE WEST TUE. GUSTY N/NE WINDS DEVELOPING LATE MON INTO TUE...ESPECIALLY NEAR THE COAST AS STORM INTENSIFIES TO THE EAST. SUBZERO WIND CHILLS LIKELY MON NIGHT. WEDNESDAY... SFC HIGH BUILDS IN FROM THE WEST WITH LOW LEVEL MOISTURE GRADUALLY MOVING EAST AND LOWERING SUBSIDENCE INVERSION LIKELY BRINGING AN END TO OCEAN EFFECT SNOW SHOWERS. STILL LOTS OF CLOUDS EXPECTED SE NEW ENG COAST...OTHERWISE MOSUNNY AND CONTINUED COLD WITH TEMPS SEVERAL DEGREES BELOW NORMAL. HIGHS IN THE 20S WITH TEENS HIGHER TERRAIN N AND W MA. THURSDAY AND FRIDAY... MODERATING TEMPS EXPECTED THU AS HIGH PRES MOVES TO THE EAST WITH MILDER SW FLOW DEVELOPING. NEXT CHANCE OF SNOW SHOWERS WILL BE SOMETIME THU NIGHT/FRI AS NEXT SHORTWAVE AND COLD FRONT APPROACHES. TIMING OF FRONT UNCERTAIN AT THIS TIME RANGE WHICH WILL AFFECT PRECIP TIMING AND TEMPS ON FRI. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SATURDAY NIGHT/... THROUGH MIDNIGHT...HIGH CONFIDENCE. MAINLY VFR. ALTHOUGH EXPECT BUILDING CLOUDS THROUGH THE EVENING AND OVERNIGHT HOURS. AFTER MIDNIGHT INTO THE DAY TOMORROW...MODERATE CONFIDENCE. ALTHOUGH HAVE SOMEWHAT HIGH CONFIDENCE IN THE OVERALL EXPECTATION TOMORROW...LOWER CONFIDENCE IN EXACT TIMING OR WHERE THE RAIN/SNOW/MIX LINE ENDS UP. EXPECT LOW PRES TO BRING SNOW TO START EARLY IN THE MORNING...WHICH WILL THEN TRANSITION TO A MIX OF SLEET AND FREEZING RAIN ESPECIALLY S AND E OF THE WORCESTER HILLS...MAINLY SNOW N. SOME AREAS WHERE IT REMAINS ALL SNOW...BUT CLOSE TO THE MIX LINE MAY SEE 6-8 INCHES OF ACCUMULATION BEFORE ITS ALL DONE. LESS ELSEWHERE. ICE ACCUMULATIONS OF A TENTH OF AN INCH OR LESS. WINDS SHIFT THROUGH THE DAY FROM THE E TO THE N...WITH GUSTS IN THE EVENING OF 20-30 KT. 30-45 KT AT TIMES ON CAPE COD AND ACK. THEN SHIFTING NW. SOME LLWS LIKELY. TOMORROW NIGHT...HIGH CONFIDENCE. CONDITIONS IMPROVE WITH WINDS SHIFTING NW. COULD BE A BURST OF SNOW AT ALL TAF SITES BRIEFLY BEFORE ENDING WITH LOW VSBYS AND QUICK ACCUMS DURING THE EVENING. AFTER ENDING EXPECT RAPID IMPROVEMENT TO VFR BUT WITH WIND GUSTS 20-30KT OUT OF THE NW. KBOS TAF...HIGH CONFIDENCE IN TAF TRENDS...LOWER CONFIDENCE IN EXACT TIMING OF MIXING. KBDL TAF...HIGH CONFIDENCE IN TAF TRENDS...LOWER CONFIDENCE IN EXACT TIMING OF MIXING. OUTLOOK /SUNDAY THROUGH WEDNESDAY/... OUTLOOK /SUNDAY THROUGH WEDNESDAY/... SUNDAY...HIGH CONFIDENCE. VFR. W/NW WIND GUSTS UP TO 25 KNOTS. MONDAY AND TUESDAY...MODERATE CONFIDENCE. MVFR CONDITIONS EXPECTED CAPE/ISLANDS AND PORTIONS OF SE MA WHERE SOME OCEAN SNOW SHOWERS ARE POSSIBLE. LOW PROB MVFR COULD BE MORE WIDESPREAD IF STORM WHICH IS PASSING TO OUT S ENDS UP FURTHER N. GUSTY N/NE WINDS TO 25-35 KT DEVELOPING SE NEW ENG COAST LATE MON/MON NIGHT...THEN SLOWLY DIMINISHING DURING TUE. WEDNESDAY...MODERATE CONFIDENCE. MAINLY VFR. SOME LINGERING MVFR POSSIBLE CAPE/ISLANDS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SATURDAY NIGHT/. THROUGH TONIGHT...HIGH CONFIDENCE. SWELLS DIMINISH THIS EVENING...GIVING WAY TO A SHORT PERIOD OF SUB HEADLINE CONDITIONS UNTIL PRECIP OVERSPREADS DURING THE EARLY MORNING HOURS. TOMORROW INTO TOMORROW NIGHT...HIGH CONFIDENCE. LOW PRES WILL RAPIDLY MOVE ACROSS THE SE WATERS AND INTENSIFY TOMORROW EVENING. THIS WILL MEAN THAT A PERIOD OF STRONG GALE FORCE WINDS ARE EXPECTED FIRST OUT OF THE N-NE...THEN SHIFTING TO THE NW BY LATE EVENING AS THE LOW MOVES OVER. EXPECT HEAVY RAIN AND FOG...POSSIBLY EVEN A LITTLE BIT OF SNOW CLOSER TO THE SHORE. THE GALES BEGIN DURING THE AFTERNOON. SEAS BUILD TO ABOUT 15 FT ON THE OUTER SE WATERS. SUNDAY...MODERATE CONFIDENCE. NW WINDS MAY APPROACH GALE FORCE AT TIMES...BUT SHOULD BE SUBSIDING EARLY...SUCH THAT AT LEAST SMALL CRAFT ADVISORIES ARE LIKELY TO BE NEEDED FOR ALL WATERS DURING THE REMAINDER OF THE DAY. OUTLOOK /SUNDAY THROUGH WEDNESDAY/... SUNDAY...HIGH CONFIDENCE. W/NW GUSTS TO 25-30 KT IN COLD ADVECTION PATTERN. MONDAY AND TUESDAY...MODERATE CONFIDENCE. LOW PRESSURE TRACKS SOUTH OF NEW ENGLAND...BUT SHOULD COME CLOSE ENOUGH TO BRING INCREASING N/NE WINDS AND BUILDING SEAS. GALE FORCE WIND GUSTS LIKELY DEVELOPING LATE MON INTO MON NIGHT AND LINGERING INTO EARLY TUE ACROSS SE WATERS. && .TIDES/COASTAL FLOODING... HAVE UPGRADED TO A COASTAL FLOOD ADVISORY FOR BOSTON HARBOR THROUGH CAPE COD...AND NANTUCKET FOR THE EARLY AFTERNOON HIGH TIDE CYCLE TOMORROW...WHICH IN BOSTON IS 11.4 FEET. THE FASTER PROGRESSION OF THIS STORM NOW SUGGESTS THAT MINOR COASTAL FLOODING /LOW PROBABILITY OF A FEW POCKETS OF MODERATE/ IS LIKELY IN THIS AREA FOR THAT HIGH TIDE. WILL STILL NEED TO WATCH CONDITIONS FOR THE OVERNIGHT HIGH TIDE AS WELL AS THE STORM MOVES OFFSHORE...BUT WINDS WILL HAVE A STRONG WESTWARD COMPONENT BY THAT TIME...IT IS JUST A MATTER AS TO WHETHER THE LEFTOVER SURGE WILL BE ABLE TO MAKE UP THE DIFFERENCE. NOTE THAT EVEN THOUGH IT IS NOT CURRENTLY OUT FOR THE NORTH SHORE AND CAPE ANN...IT IS POSSIBLE THAT THE SURGE WILL BE A BIT HIGHER THAN CURRENTLY FORECAST...SO IT MAY NEED TO BE ADDED THERE AS WELL. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 7 PM EST SATURDAY FOR CTZ002>004. MA...COASTAL FLOOD ADVISORY FROM NOON TO 4 PM EST SATURDAY FOR MAZ015-016-019-022-024. WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 7 PM EST SATURDAY FOR MAZ002-003-007>009-015>018-020-021. WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 7 PM EST SATURDAY FOR MAZ004>006-010>014-026. WIND ADVISORY FROM 3 PM SATURDAY TO MIDNIGHT EST SATURDAY NIGHT FOR MAZ022-024. RI...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 7 PM EST SATURDAY FOR RIZ002>006. WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 7 PM EST SATURDAY FOR RIZ001. MARINE...GALE WARNING FROM 1 PM SATURDAY TO 7 AM EST SUNDAY FOR ANZ231>235-237-250-251-254>256. SMALL CRAFT ADVISORY FROM 1 PM SATURDAY TO 7 AM EST SUNDAY FOR ANZ230-236. && $$ SYNOPSIS...KJC/DOODY NEAR TERM...KJC/DOODY SHORT TERM...DOODY LONG TERM...KJC AVIATION...KJC/DOODY MARINE...KJC/DOODY TIDES/COASTAL FLOODING...STAFF

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