Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 010958 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 458 AM EST SUN MAR 1 2015 .SYNOPSIS... A FAST MOVING LOW PRESSURE SYSTEM WILL BRING ACCUMULATING SNOW LATER TODAY AND ESPECIALLY TONIGHT WITH THE HIGHEST AMOUNTS EXPECTED SOUTH OF THE MASSACHUSETTS TURNPIKE.HIGH PRESSURE BRINGS DRY COLD AIR FOR THE EARLY WEEK. LOW PRESSURE FROM NORTHERN CANADA AND ASSOCIATED LOW FORMING OVER THE PLAINS MONDAY WILL MERGE...THEN PASS WEST AND NORTH OF NEW ENGLAND. THIS WILL SWING A COLD FRONT ACROSS THE REGION ON WEDNESDAY. DRY AND COLD WEATHER RETURNS FOR THE END OF THE WEEK. && .NEAR TERM /UNTIL 3 PM THIS AFTERNOON/... MID LEVEL CLOUDINESS WILL STREAM INTO SOUTHERN NEW ENGLAND AND THICKEN DURING THE MORNING HOURS IN ADVANCE OF APPROACHING LOW PRESSURE. SOUTHWEST FLOW ALOFT OVERRUNING THE COLD DOME AT THE SURFACE MAY ALLOW FOR SOME LIGHT SNOW/FLURRIES TO BREAK OUT ACROSS THE INTERIOR LATE THIS MORNING/EARLY AFTERNOON AND THEN FIND THEIR WAY TO THE COAST BY MID TO LATE AFTERNOON. THE LIFT THROUGH MID AFTERNOON IS FAIRLY WEAK...SO THE AREAS OF SNOW SHOULD BE RATHER LIGHT. ANY ACCUMULATIONS THAT OCCUR WILL PROBABLY BE A DUSTING TO LESS THAN 1 INCH THROUGH THAT THAT TIME. HIGH TEMPS WILL MAINLY BE IN THE UPPER 20S TO AROUND 30. && .SHORT TERM /3 PM THIS AFTERNOON THROUGH 6 AM MONDAY/... *** BULK OF THE ACCUMULATING SNOW OCCURS BETWEEN 3 PM AND 1 AM WITH THE HEAVIEST AMOUNTS SOUTH OF THE MA TURNPIKE *** 1) OVERVIEW AND TIMING: THE BULK OF THE ACCUMULATING SNOW WILL OCCUR BETWEEN 3 PM AND 1 AM ACROSS THE REGION. THE SNOW SHOULD TAPER OFF TO FLURRIES TOWARD DAYBREAK MONDAY. THE MODELS DO AGREE THAT THE BETTER FORCING WILL OCCUR TO THE SOUTH OF THE MA TURNPIKE. THIS A RESULT OF SECONDARY LOW PRESSURE NEAR THE SOUTH COAST...ALLOWING FOR SOME SURFACE CONVERGENCE AS WELL AS THE INTENSIFICATION OF THE LOW LEVEL JET. THE BIGGEST ISSUE IS THE MODELS ARE NOT IN AGREEMENT IN HOW INTENSE THE FORCING WILL BE ACROSS THE REGION THIS EVENING. THE RGEM/NAM ARE THE MOST ROBUST WITH QPF SOUTH OF THE MA TURNPIKE. THE NAM SHOWS A PERIOD OF FAIRLY STRONG LIFT OF 15 TO 20 MICROBARS PER SECOND WITHIN THE BEST SNOWGROWTH REGION THIS EVENING. THIS WOULD TRANSLATE TO A PERIOD OF 1+ INCH PER HOUR SNOWFALL RATES NEAR AND SOUTH OF THE MA PIKE. ON THE OTHER HAND...THE GFS ALSO HAS FAIRLY STRONG LIFT...BUT KEEPS IT SOUTHEAST OF OUR REGION OUT OVER THE OCEAN. THE SECONDARY LOW PRESSURE SYSTEM ON THE GFS IS WEAKER AND FURTHER SOUTHEAST...RESULTING IN THE LOW LEVEL JET BEING DISPLACED FURTHER EAST. THE ECMWF/UKMET SOLUTIONS SEEM TO BE THE MIDDLE GROUND WHICH WE WILL LEAN TOWARDS. 2) WINTER WEATHER HEADLINES AND SNOW ACCUMS: WITH THAT SAID...THE OTHER DILEMMA IS WHAT TO DO WITH THE CURRENT HEADLINES. THIS DOES NOT APPEAR TO BE THE TYPE OF SETUP WHERE WE ARE GOING TO RECEIVE WIDESPREAD WARNING SNOWFALL AMOUNTS. THE WINDOW FOR THE VERY STRONG LIFT/FORCING IS SHORT-LIVED AND REALLY WOULD LIKE TO SEE THE LOW LEVEL JET A BIT MORE BACKED TO TRANSPORT DEEPER MOISTURE NORTHWARD. THEREFORE...FEEL THAT FOR MOST OF THE REGION WINTER WEATHER ADVISORY/S FOR 3 TO 6 INCHES OF SNOW WILL COVER IT. HOWEVER...GIVEN THERE IS NICE OMEGA IN THE SNOW GROWTH REGION...WE MIGHT BE LOOKING AT SOME DECENT RATIOS. SO WE STILL CAN NOT RULE OUT THE LOW RISK OF REACHING WARNING AMOUNTS AND LATER SHIFTS WILL HAVE TO MONITOR CLOSELY...ESPECIALLY ACROSS NORTHERN CT AND NORTHWEST RI. WE DID UPGRADE A SMALL AREA FROM CENTRAL AND SOUTHERN RHODE ISLAND INTO SOUTHEAST MA INCLUDING THE SOUTH COAST TO A WINTER STORM WARNING. THE NOSE OF THE LOW LEVEL JET LOOKS TO TRANSPORT SOME DEEPER MOISTURE INTO THIS REGION. THERE ALSO COULD BE SOME ENHANCEMENT ALONG THE LAND/SEA INTERFACE AND A WEAK SURFACE BOUNDARY SO WENT WITH 4 TO 8 INCHES IN THIS REGION. 3) PTYPE AND IMPACTS: THE MODELS HAVE TRENDED COLDER OVER THE PAST 24 HOURS. THEREFORE...EXPECT THIS BE PRETTY MUCH A SNOW EVENT. IT DOES BECOME A VERY CLOSE CALL NEAR THE SOUTH COAST...BUT WERE LEANING TOWARDS IT STAYING MAINLY WET SNOW. IF PRECIPITATION LIGHTENS UP THAT MAY INCREASE THIS RISK WE SEE A BRIEF CHANGE OVER TO RAIN. MEANWHILE...WE WENT WITH A HIGH END WINTER WEATHER ADVISORY FOR THE CAPE BECAUSE THEY MAY CHANGE TO RAIN FOR A TIME...ESPECIALLY EAST OF HYANNIS. IF THE CHANGE OVER DOES NOT OCCUR...WE MAY NEED TO UPGRADE THEM TO A WINTER STORM WARNING ESPECIALLY NEAR THE CAPE COD CANAL GIVEN EXPECTED QPF. THE ONE THING WILL ALSO HAVE TO WATCH IS AREAS NEAR THE SOUTH COAST AND CAPE COD. LOOKS TO BE A WET SNOW DOWN THAT WAY AND ON GOING ROOF ISSUES MAY BE EXACERBATED...ESPECIALLY IF ANY AREAS THAT ARE ABLE TO EXCEED 6 INCHES OF WET SNOW. && .LONG TERM /MONDAY THROUGH SATURDAY/... HIGHLIGHTS... * BLUSTERY CONDITIONS ON MON WITH DRY WEATHER CONTINUING INTO TUE. * A STORM SYSTEM BRINGS MIXED PRECIP TUE INTO WED. * CONDITIONS IMPROVE THU BUT BECOMING COLD AGAIN. OVERVIEW AND MODEL PREFERENCES... A SPLIT FLOW MERGER WILL BE THE DEFINING FACTOR THROUGH THE LONG TERM FORECAST PERIOD. IN THE MID TERM...THE STREAMS MERGE THANKS TO PHASING OF NRN AND SRN STREAM SHORTWAVES UPSTREAM AS MERGING STRONG JET DEVELOPS ACROSS THE NE CONUS. THESE FEATURES WILL ALLOW LOW PRES TO GRADUALLY DEEPEN AND SLIDE THROUGH SRN ONTARIO AND QUEBEC...CREATING AN OVERRUNNING EVENT AS THE SYSTEM ATTEMPTS TO OCCLUDE. THIS IS THE MIXED PRECIP EVENT WE HAVE BEEN DISCUSSING FOR SOME TIME NOW. NOW THAT NAM HAS CAPTURED IT...IT APPEARS COLDER THAN MOST OF THE DETERMINISTIC GUIDANCE...WHILE THE ECMWF STARTS COLD AND SHIFTS TO THE WARMER SIDE OF THE ENVELOPE DUE TO THE FACT THAT IT IS MORE AMPLIFIED THAN OTHER MODELS. THE GFS...ECENS/GEFS MEANS ARE ACTUALLY A GOOD MIDDLE GROUND HERE. THIS BLEND WILL BE USED THROUGH THE REMAINDER OF THE LONG TERM AS WELL TO TAKE INTO ACCOUNT THE VARIOUS SOLUTIONS. DETAILS... MON INTO TUE... REMNANT SNOWFALLS WILL BE GRADUALLY COMING TO AN END THROUGH MID MORNING MON...ALTHOUGH FLURRIES MAY LINGER A BIT LONGER IN THE BERKSHIRES. STRONG HIGH PRES WILL THEN SLIDE ACROSS THE REGION THROUGH TUE...WITH MAINLY DRY WX. TEMPS LOOK TO REMAIN BELOW NORMAL GIVEN LITTLE CHANGE IN THE AIRMASS FROM PREVIOUS DAYS. TUE NIGHT INTO WED... OVERRUNNING EVENT EXPECTED AS WARM FRONT WILL ATTEMPT TO PUSH N ACROSS THE REGION BUT IS LIKELY TO STRUGGLE NEAR THE SFC DUE TO ENTRENCHED COLD AIR AND A DEEP SNOWPACK. HOWEVER...50-60 KT LLJ WITH STRONG SLY COMPONENT WILL ALLOW UPPER LVL WARMING TON CONTINUE UNIMPEDED. IN SPITE OF THE STRONG JET AT ONLY 3-5KFT ABOVE THE SFC...SNOWPACK WILL MAKE MIXING DIFFICULT SO NOT EXPECTING SIGNIFICANT WIND ISSUES AT THIS TIME. THE COLUMN STARTS COLD ENOUGH FOR SNOW AT ONSET TUE EVENING...AND LOOKS LIKE AS MUCH AS 0.40-0.60 OF THE TOTAL EVENT QPF FALLS AS SNOW INITIALLY EVERYWHERE...WITH GRADUAL CHANGEOVER DURING THE EARLY MORNING HOURS WED MORNING FROM S-N. THEREFORE...COULD SEE AT LEAST ADVISORY IF NOT LOW-END WARNING LVL SNOWFALLS THROUGH THE OVERNIGHT HOURS BEFORE A TRANSITION TO SLEET...THEN FREEZING RAIN. FREEZING RAIN COULD LOCK IN FOR SOME TIME AND GIVEN THAT H93 TEMPS /EVEN ON THE COLDEST GUIDANCE/ AN AVERAGE OF +4C DURING THE 08Z- 16Z TIMEFRAME...BUT SFC TEMPS MAY HOLD NEAR FREEZING FOR SOME TIME GIVEN THE DEEP SNOWPACK ACROSS THE AREA. HOWEVER...STRAIGHT RAIN FOR A TIME FROM ABOUT MID MORNING INTO THE AFTERNOON IS LIKELY UNTIL THE PRECIP COMES TO AN END. DEPENDING ON HOW QUICKLY 2M TEMPS REBOUND...AS MUCH AS A QUARTER INCH OF ICE CAN/T BE RULED OUT. AGREE WITH PREVIOUS FORECASTER THAT LEANING A BIT COLDER THAN MOS 2M TEMPS IS PROBABLY THE WAY TO GO. MODEST UPPER LVL INSTABILITY AS WARMING OCCURS IN THE MID LVLS COULD ALSO MEAN A PERIOD OF HEAVY PRECIP...BOTH SNOW AND RAIN. WITH THE RAIN...COMES A RISK FOR POOR DRAINAGE FLOODING ACROSS THE REGION AS SNOW MELTS AND DRAINS BECOME CLOGGED. PRECIP COMES TO AN END ACROSS MOST OF THE REGION BY AFTERNOON WED...BUT MAY LINGER A BIT NEAR THE S COAST...MORE ON THAT BELOW. WED NIGHT INTO THU... CONFIDENCE IN THE FORECAST CONTINUES TO DIMINISH HERE PARTIALLY DEPENDENT ON HOW FAST THE UPPER LVL JET EXITS TO THE EAST AND HOW AMPLIFIED THE PATTERN REMAINS IN THE WAKE OF THE LOW PRES. THE MORE AMPLIFIED GUIDANCE...LED BY THE ECMWF KEEPS THE COLD FRONT JUST OFFSHORE AND WITHIN THE EQUATORWARD ENTRANCE REGION OF THE UPPER LVL JET. THIS SUGGESTS S COASTAL AREAS COULD CONTINUE TO SEE PRECIP...POSSIBLY EVEN CHANGING BACK TO SNOW FOR A TIME WELL INTO THE DAY ON THU. THE MORE PROGRESSIVE GUIDANCE...LED BY THE GFS WOULD MOVE BOTH OF THESE FEATURES OFFSHORE SUCH THAT THU IS MAINLY DRY AND BECOMING QUITE COLD AS ANOTHER ARCTIC AIRMASS SETTLES IN. FOR NOW...WILL CONTINUE TO LEAN ON THE MORE PROGRESSIVE GFS BUT WITH THE ECENS/GEFS SLOWER MEMBERS BLENDED IN. THE FINAL ANSWER WILL LIKELY BE SOMEWHERE IN BETWEEN THE TWO SOLUTIONS. IN ANY CASE...MUCH COLDER AIRMASS EXPECTED TO MOVE IN. THU NIGHT INTO FRI NIGHT... COLD AIRMASS ACROSS THE REGION ASSOCIATED WITH YET ANOTHER 1035+ HPA HIGH PRES. WILL LIKELY SEE HIGHS ONLY MAKING THE TEENS AND 20S WITH LOWS BACK IN THE SINGLE DIGITS ABOVE AND BELOW ZERO. NEXT WEEKEND... SOME UNCERTAINTY HERE AS TO WHETHER YET ANOTHER WAVE WILL BE EFFECT THE REGION. WILL LEAN MAINLY DRY FOR NOW AS THE AIRMASS IN PLACE IS QUITE DRY AND THE WAVE ITSELF IS QUITE WEAK AND SHEARING OUT. && .AVIATION /09Z SUNDAY THROUGH THURSDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TODAY AND TONIGHT/... TODAY AND TONIGHT...MODERATE CONFIDENCE. VFR CONDITIONS THROUGH AT LEAST MID MORNING. SOME MVFR TO IFR CONDITIONS DEVELOP FROM WEST TO EAST LATE THIS MORNING AND THIS AFTERNOON IN AREAS OF LIGHT SNOW. HOWEVER...THE BULK OF THE MODERATE TO EVEN BRIEFLY HEAVY SNOW WILL OCCUR THIS EVENING WHEN WIDESPREAD IFR TO LIFR CONDITIONS OCCUR. THE LOWER CONDITIONS MOST LIKELY SOUTH OF THE MA TURNPIKE. PTYPE PRETTY MUCH ALL SNOW...EXCEPT FOR THE VERY IMMEDIATE SOUTH COAST/CAPE WHERE SNOW MAY MIX WITH OR CHANGE TO RAIN FOR A TIME. WHETHER OR NOT THAT HAPPENS IS UNCERTAIN...BUT WE DO THINK THAT AT LEAST THE ISLANDS WILL CHANGE TO RAIN. BULK OF SNOW ENDS BY 8 OR 9Z TONIGHT AND MUCH OF THE THE REGION SHOULD ALREADY HAVE VFR CONDITIONS BY 12Z MONDAY. KBOS TAF...CONFIDENT IN OVERALL TRENDS BUT EXACT TIMING IS MORE UNCERTAIN. WHILE SOME LIGHT SNOW IS POSSIBLE THIS AFTERNOON...BULK OF ACCUMULATING SNOW WITH WIDESPREAD IFR TO LIFR CONDITIONS EXPECTED THIS EVENING. KBDL TAF...CONFIDENT IN OVERALL TRENDS BUT EXACT TIMING IS MORE UNCERTAIN. WHILE SOME LIGHT SNOW IS POSSIBLE LATE THIS MORNING AND AFTERNOON...BULK OF ACCUMULATING SNOW WITH WIDESPREAD IFR TO LIFR CONDITIONS EXPECTED AFTER 3 OR 4 PM. OUTLOOK...MONDAY THROUGH THURSDAY... MONDAY...HIGH CONFIDENCE. IFR/MVFR IN REMNANT SNOWS END EARLY...WITH TRANSITION TO VFR EVERYWHERE BY AFTERNOON. W-NW WIND GUSTS UP TO AROUND 30 KT AT TIMES DURING THE AFTERNOON AND EVENING. MON NIGHT INTO TUE...HIGH CONFIDENCE. MAINLY VFR. WINDS DIMINISH MON NIGHT. TUE NIGHT INTO THU...MODERATE CONFIDENCE. A MESSY PERIOD. SNOW BEGINS EVERYWHERE LATE TUE INTO WED NIGHT WITH MODERATE ACCUMS POSSIBLE...THEN EXPECT GRADUALLY TRANSITION TO SLEET AND FREEZING RAIN DURING THE EARLY MORNING HOURS WED...THEN TO ALL RAIN DURING THE DAY ON WED. SOME ICE ACCUM POSSIBLE AS WELL. THE RAIN DIMINISHES LATE WED BUT MAY LINGER ALONG THE S COAST AND EVEN CHANGE TO SNOW INTO THE DAY ON THU. EXPECT PERIODS OF IFR/LIFR CONDITIONS THROUGHOUT THE PERIOD WITH SOME IMPROVEMENT FROM N-S ON THU. LLWS LIKELY ESPECIALLY TUE NIGHT AND EARLY WED. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TODAY AND TONIGHT/...HIGH CONFIDENCE. A WEAK WAVE OF LOW PRESSURE MOVES ACROSS THE WATERS LATER TODAY AND TONIGHT. WEAK PRESSURE GRADIENT SHOULD KEEP WINDS/SEAS BELOW SMALL CRAFT THRESHOLDS TODAY AND TONIGHT. THE SYSTEM REALLY INTENSIFIES AS IT MOVES INTO THE CANADIAN MARITIMES NEAR DAYBREAK MONDAY...SO WESTERLY WIND GUSTS MAY REACH 20 TO 25 KNOTS NEAR 12Z MONDAY. OTHERWISE...RAIN AND SNOW LATE TODAY AND ESPECIALLY TONIGHT WILL REDUCE VISIBILITIES AT TIMES FOR MARINERS. OUTLOOK...MONDAY THROUGH THURSDAY..MODERATE CONFIDENCE. MONDAY INTO MONDAY NIGHT...HIGH CONFIDENCE. WINDS BEGIN OUT OF THE SW THEN SHIFT TO W-NW IN THE AFTERNOON. WIND GUSTS REACH 35-40 KT DURING THE AFTERNOON AND OVERNIGHT SO WILL BE ISSUING A GALE WATCH. SEAS BUILD 10-12 FT ON THE OCEAN WATERS. SOME LIGHT FREEZING SPRAY POSSIBLE MON EVENING INTO TUE MORNING. TUE...HIGH CONFIDENCE. WINDS AND SEAS START AT OR AROUND SMALL CRAFT ADVISORY THRESHOLDS BUT THEN DROP DURING THE DAY SUCH THAT A PERIOD OF QUIET BOATING WEATHER IS LIKELY TUE AFTERNOON AND EVENING. TUE NIGHT INTO THU...MODERATE CONFIDENCE. LOW PRES PASSES WELL INLAND...WITH WINDS OUT OF THE S GRADUALLY SHIFTING TO THE W LATE WED INTO THU. PERIODS OF WIND GUSTS 25-30 KT EXPECTED ALTHOUGH GUSTS MAY APPROACH GALE FORCE WED EVENING. SEAS BUILD THROUGH WED TO AROUND 7-10FT ON THE OCEAN WATERS THEN DIMINISH THU. AT THE VERY LEAST SMALL CRAFT ADVISORIES ARE LIKELY DURING THIS PERIOD. PERIODS OF SNOW CHANGING TO RAIN EARLY WED WITH SOME LOW VSBYS IN RAIN AND FOG ON WED. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...WINTER WEATHER ADVISORY FROM NOON TODAY TO 7 AM EST MONDAY FOR CTZ002>004. MA...WINTER WEATHER ADVISORY FROM NOON TODAY TO 7 AM EST MONDAY FOR MAZ002>016-022>024-026. WINTER STORM WARNING FROM 3 PM THIS AFTERNOON TO 7 AM EST MONDAY FOR MAZ017>021. RI...WINTER WEATHER ADVISORY FROM NOON TODAY TO 7 AM EST MONDAY FOR RIZ001-008. WINTER STORM WARNING FROM 3 PM THIS AFTERNOON TO 7 AM EST MONDAY FOR RIZ002>007. MARINE...GALE WATCH FROM MONDAY MORNING THROUGH LATE MONDAY NIGHT FOR ANZ231>235-237-250-251-254>256. && $$ SYNOPSIS...FRANK/DOODY NEAR TERM...FRANK SHORT TERM...FRANK LONG TERM...DOODY AVIATION...FRANK/DOODY MARINE...FRANK/DOODY

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.