Area Forecast Discussion
Issued by NWS Boston, MA

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745 FXUS61 KBOX 051731 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1231 PM EST FRI FEB 5 2016 .SYNOPSIS... COLD FRONT STALLING OFFSHORE WILL PROVIDE A FOCUS FOR LOW PRESSURE TO TRAVEL ALONG AFTER SUNRISE. THIS LOW PRESSURE WILL DELIVER A MIX OF RAIN CHANGING TO HEAVY SNOW ACROSS THE REGION. HIGH PRESSURE BRINGS DRY WEATHER OVER THE WEEKEND...ALTHOUGH A WEAK COLD FRONT SUNDAY MAY BRING A FEW CLOUDS. A COMPLEX COASTAL STORM SHOULD AFFECT THE REGION LATER MONDAY INTO WEDNESDAY. && .NEAR TERM /UNTIL 2 PM THIS AFTERNOON/...
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1 PM UPDATE... CONTINUE TO REVISE SNOW MAP AS STRONG BANDING CONTINUES TO MOVE ACROSS BOTH ERN MA AND WESTERN/CENTRAL MA AT THIS TIME. HAVE REPORTS ALREADY EXCEEDING 8 INCHES IN SEVERAL SPOTS AS A RESULT OF THESE BANDS. RATIOS USED LIKELY TOO LOW IS PART OF THE ISSUE AS THE FEW REPORTS OF LIQUID EQUIVALENTS ARE ON TARGET WITH QPF. OTHERWISE...TIMING STILL LOOKS GOOD FOR ENDING LATER TODAY/THIS AFTERNOON. HAVE ADDED ADVISORIES FOR CAPE/VINEYARD AND ALSO HOISTED WIND ADVISORIES THERE AS WELL AS STRONG WINDS WILL CONTINUE AS THE LOW PRES MAKES IT/S CLOSEST PASS. PREVIOUS DISCUSSION... *** WESTWARD TREND IN THE SYSTEM HAS ALLOWED FOR WARNINGS AND ADVISORIES TO BE EXPANDED *** BUSY NIGHT AS WE CONTINUE TO EVALUATE THE LATEST DATA AND TRENDS FOR THIS UPCOMING WINTER SYSTEM. PRECIP SHIELD CONTINUES TO MOVE WESTWARD AS MID-LEVEL TROUGH STRENGTHENS. GULF MOISTURE CONTINUES TO POOL INTO THE REGION ALLOWING FOR PWATS TO BE CLOSE TO AN INCH. BIGGEST TREND BETWEEN THE 12Z AND 00Z RUNS IS THAT THE GUIDANCE CONTINUES ITS WESTWARD TREND. HEAVY PRECIP SWATH OVER NJ AND EASTERN PA WILL CONTINUE TO MOVE NORTHWARD AND IMPACT WESTERN MASSACHUSETTS. BECAUSE OF THIS UPSTREAM TREND...HAVE EXPANDED THE WINTER WEATHER ADVISORY TO INCLUDE ALL OF THE PIONEER VALLEY. ANY PRECIP THAT IS OR WILL FALL WILL BE SNOW ACROSS THE EAST SLOPE OF THE BERKS AS MESONET SITES ARE ALREADY REPORTING TEMPS INTO THE UPPER 20S TO LOW 30S EARLY THIS MORNING. THIS TREND IS IN LINE WITH THE LATEST HRRR AND RAP GUIDANCE. ASIDE FROM THE EXPANSION...NO MAJOR CHANGES TO HEADLINES AT THIS TIME. HAVE RECEIVED SEVERAL REPORTS OF EITHER SNOW...OR A WINTRY MIX ACROSS CENTRAL MASS AND INTO CT. THIS IS ALSO IN LINE WITH THE LATEST DUAL-POL DATA. HIGHER REFLECTIVITY ECHOES ARE STARTING TO MOVE INTO WINDHAM COUNTY...WHICH WILL BE EITHER A MIX OR JUST SNOW AS 925 MB TEMPS ARE ALREADY BELOW 32F PER SPC MESO DATA. ANTICIPATE THE NEXT SEVERAL HOURS TO BE FAIRLY BUSY WITH RAIN/SNOW MIX TRANSITIONING TO ALL SNOW AS UPPER LEVEL TROUGH APPROACHES FROM THE WEST AND SURFACE LOW NEARS. P-TYPE AND CHANGE OVER TIMING... MOISTURE WILL CONTINUE TO SPILL INTO SOUTHERN NEW ENGLAND AS COASTAL LOW MOVES ALONG STALLED COLD FRONT. AS MENTIONED EARLIER THE PRECIP SHIED HAS EXPANDED FARTHER WESTWARD THEN ORIGINALLY FORECAST...WHICH IS THE LATEST TREND IN ALL OF THE GUIDANCE...INCLUDING THE 06Z NAM. CHANGE OVER HAS ALREADY STARTED TO OCCUR ACROSS SEVERAL LOCATIONS AND EXPECT THIS TREND TO CONTINUE OVER THE NEXT SEVERAL HOURS. STILL CONCERNED ABOUT THE MORNING COMMUTE FOR MANY AREAS WEST OF THE I-95 CORRIDOR WHERE HEAVY WET SNOW WILL BE FALLING. ANTICIPATE THE CHANGE OVER TO MAKE IT TO SOUTHEASTERN MASS INCLUDING BOS AND PVD CLOSER TO THE 6-8 AM HOUR. THE CAPE AND ISLANDS WILL TAKE A BIT LONGER AS CAA WILL TAKE A BIT OF TIME TO REACH THEM. FEEL IT WILL BE CLOSER TO 10AM-NOON. ALTHOUGH SLEET MAY MIX IN DURING THE TRANSITION...BELIEVE MANY LOCATIONS WILL SWITCH FROM RAIN TO STRAIGHT SNOW. QPF AND SNOWFALL AMOUNTS... HAVE ADJUSTED THE SNOWFALL AMOUNTS SOME OVER THE PAST FEW HOURS. GENERALLY BELIEVE THAT LOCATIONS WITHIN THE WARNING WILL GET AT LEAST A SLOPPY 5-7 INCHES OF SNOW. HIGHER AMOUNTS ARE POSSIBLE ESPECIALLY ACROSS THE CENTRAL HILLS WITHIN TOLLAND...WINDHAM...WORCESTER AND PROVIDENCE COUNTIES. MOST OF THE GUIDANCE IS IN AGREEMENT FOR QPF. THE BIGGEST ISSUE IS THE BOUNDARY LAYER TEMPS AND THERMAL PROFILES. BELIEVE WE HAVE A GOOD TREND GOING AT THIS TIME. SOME AREAS IN QUESTION WHICH COULD BE UPGRADED WITHIN THE WARNING IS SOUTHERN BRISTOL AND PLYMOUTH COUNTIES. HOWEVER THESE LOCATIONS MAY BE STUCK IN THE MIX LONGER KEEPING SNOWFALL AMOUNTS LOW. HAVE GONE AHEAD AND UPGRADED THE EAST SLOPE OF THE BERK TO AN ADV AS SNOW IS ALREADY STARTING TO FALL PER WEBCAMS. THE PIONEER AND CONNECTICUT VALLEY MAY SEE LOWER AMOUNTS AS WELL THANKS TO SHADOWING. SO EVEN THOUGH SNOW AMOUNTS ARE OUT...THERE STILL COULD BE SOME CHANGES THANKS TO SOME MESOSCALE ISSUES. IMPACTS... DUE TO THE FACT THAT SNOW RATIOS WILL BE LOW WITH THIS STORM...AND BANDING WITH 1+ INCH/HR RATES ARE POSSIBLE...HEAVY WET SNOW MAY LEAD TO LOCALIZED POWER OUTAGES. THIS WILL BE EXACERBATED BY A LLJ AROUND 40 KT WITH THE POTENTIAL TO MIX DOWN SOME OF IT/S MOMENTUM. THEREFORE...THE COMBINATION OF WIND GUSTS 30-40 MPH AND HEAVY WET SNOW MAY INCREASE THE RISK. THE OTHER PRIMARY IMPACT IS THAT THE CHANGE-OVER AND HEAVIEST PRECIP/SNOW WILL BE OCCURRING DURING THE PEAK HOURS OF THE AM COMMUTE...WITH LOCALIZED VISIBILITY RESTRICTIONS AND SLIPPERY CONDITIONS POSSIBLE ON UNTREATED ROADWAYS.
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&& .SHORT TERM /2 PM THIS AFTERNOON THROUGH SATURDAY NIGHT/... THE MORE DYNAMIC NATURE OF THIS SYSTEM IN RELATION TO PREVIOUS PROGS SUGGEST A SLOWER END. ALTHOUGH THE NORTHERLY FLOW WILL BE DRYING THE LOW LEVELS...SO THERE COULD BE A LITTLE BIT OF SNOW LEFTOVER MID-LATE AFTERNOON ACROSS EASTERN MA BEFORE THINGS END BY EARLY EVENING. TEMPERATURES WILL BEGIN TO QUICKLY DROP OFF DURING THE LATE AFTERNOON HOURS. THIS MAY CAUSE ANY UNTREATED ROADS TO BE SLIPPERY FOR THE EVENING COMMUTE. && .LONG TERM /SUNDAY THROUGH THURSDAY/... BIG PICTURE... LONGWAVE SCALE CONTINUES TO SHOW BUILDING RIDGE IN THE WEST AND DIGGING TROUGH IN THE EAST...POINTING TO WARM TREND WEST AND COOLING EAST. SMALLER SCALE CONTINUES TO SHOW A THREE-RING CIRCUS OF SHORTWAVES EITHER AFFECTING OR WITH POTENTIAL TO AFFECT OUR WEATHER THROUGH THE LONG TERM PERIOD. THIS IS ESPECIALLY TRUE WITH TWO SHORTWAVES MOVING THROUGH THE EASTERN UPPER TROUGH TUESDAY-WEDNESDAY WHERE INTERACTION BETWEEN THE SHORTWAVES COULD OCCUR. MODEL MASS FIELDS ARE SIMILAR THROUGH THE WEEKEND. MODELS ALSO AGREE ON TWO WEATHER SYSTEMS...ONE WELL OFFSHORE MONDAY AND A SECOND CLOSE TO SHORE TUESDAY. BUT ALL SHOW DIFFERING SCENARIOS FOR HOW THESE SYSTEMS WILL AFFECT SOUTHERN NEW ENGLAND. BEST CONFIDENCE IN HANDLING THE EARLY WEEK SYSTEMS IS WITH THE GEFS /ENSEMBLES/ THE DAILIES... TONIGHT-SATURDAY...HIGH CONFIDENCE. COASTAL LOW MOVES OFF THROUGH NOVA SCOTIA AND HIGH PRESSURE BUILDS OVER THE EASTERN USA. EXPECT DRY WEATHER AND SEASONABLY COLD TEMPERATURES. CLEAR SKIES AND DIMINISHING WIND OVER FRESH SNOW COVER MAY LEAD TO COOLER TEMPS TONIGHT THAN INDICATED BY GUIDANCE. WITH DEW POINTS IN THE TEENS AND WINDS BECOMING LIGHT...WE BUMPED GUIDANCE DOWN A COUPLE OF DEGREES. ON SATURDAY WITH WINDS ALOFT SHIFTING SOUTHWEST...THE MIXED LAYER SHOULD REACH AROUND 950 MB. TEMPS AT THAT LEVEL WOULD SUPPORT MAX SFC TEMPS IN THE MID TO UPPER 30S. SUNDAY...MODERATE-HIGH CONFIDENCE. NORTHERN STREAM SHORTWAVE AND ASSOCIATED SURFACE COLD FRONT CROSS THE NORTHEAST USA. THE GFS PUSHES THE FRONT THROUGH SOUTHERN NEW ENGLAND LATE IN THE DAY WHILE THE ECMWF SEEMS TO LOSE THE FRONT IN NORTHERN NEW ENGLAND. LIMITED MOISTURE AND DYNAMICS SUGGEST JUST A FEW CLOUDS BUT NO PRECIP. HIGH PRESSURE BUILDS SOUTH FROM QUEBEC INTO NEW ENGLAND WITH COLDER AIR ARRIVING BY SUNDAY NIGHT. TEMPERATURES AHEAD OF THE FRONT SUPPORT MAX SFC TEMPS IN THE LOWER 40S. THE COLDER AIR ARRIVING SUNDAY NIGHT SHOULD BRING MIN TEMPS ROUGHLY 10 DEGREES COLDER THAN ON SATURDAY NIGHT. MONDAY THROUGH THURSDAY...LOW CONFIDENCE. SOUTHERN STREAM SHORTWAVE...AS PREVIOUSLY ADVERTISED...GENERATES A SURFACE LOW OFF THE SOUTHEAST USA COAST. THIS COASTAL LOW THEN MOVES NORTHEAST AND PASSES WELL OFFSHORE OF OUR AREA. NORMALLY THIS PATH WOULD KEEP PCPN OFFSHORE. HOWEVER WITH THE HIGH TO THE NORTH WE COULD DEVELOP SUFFICIENT MARINE FLOW OFF THE GULF OF MAINE TO BRING CLOUDS AND PCPN MONDAY ESPECIALLY IN THE COASTAL PLAIN. TEMPERATURE PROFILES WOULD SUPPORT MAINLY SNOW...BUT WITH POTENTIAL RAIN/SNOW MIX NEAR THE COAST. ANOTHER SHORTWAVE MOVES ASHORE FROM THE PACIFIC TONIGHT AND CROSSES TO THE GREAT LAKES OVER THE WEEKEND. THIS DIGS AN UPPER TROUGH OVER THE MIDWEST AND LEADS TO COASTAL LOW PRESSURE FORMING ALONG THE MID ATLANTIC COAST LATE MONDAY NIGHT. THE LOW THEN MOVES UP THE COAST TUESDAY AND PASSES OFFSHORE OF NEW ENGLAND. EACH MODEL HANDLES THIS COASTAL LOW DIFFERENTLY...SO CONFIDENCE IN ANY ONE SOLUTION IS LOW. CONFIDENCE SHOULD INCREASE OVER THE WEEKEND AS THE SHORTWAVE MOVES FEET-DRY ON THE PACIFIC COAST. BEST DYNAMICS UNDER THE LEFT EXIT REGION OF THE SUPPORTING UPPER JET MOVES OFF TOWARD NOVA SCOTIA TUESDAY EVENING/NIGHT...SO BEST CHANCE OF PCPN SHOULD BE ON TUESDAY THEN DIMINISH TO SHOWERS TUESDAY NIGHT/WEDNESDAY. PTYPE AGAIN FAVORS SNOW INLAND AND SNOW OR A RAIN/SNOW MIX ALONG THE COAST. UPPER TROUGH/COLD POOL FROM THE MIDWEST LINGERS OVER THE NORTHEAST USA THROUGH THURSDAY MAINTAINING SCATTERED TO WIDELY SCATTERED SNOW SHOWERS WEDNESDAY AND POSSIBLY INTO THURSDAY. && .AVIATION /17Z FRIDAY THROUGH TUESDAY/...
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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/... THROUGH 00Z...HIGH CONFIDENCE IN TRENDS...TIMING MAY BE OFF A BIT. AREAS OF LIFR/IFR IN HEAVY SNOW AND LOW CIGS CONTINUE THROUGH ABOUT 20Z EVERYWHERE...THEN GIVE WAY TO VFR FROM W-E THROUGH 00Z. STRONG N WINDS WITH GUSTS 20-30 KT OVER THE INTERIOR AND 30-40 KT ALONG THE CAPE/ISLAND. TONIGHT...HIGH CONFIDENCE. MAINLY VFR. ANY UNTREATED AND WET RUNWAYS WILL FREEZE AS TEMPERATURES DROP RAPIDLY. WIND GUSTS REMAIN N-NW BUT DIMINISH THROUGH THE OVERNIGHT HOURS. TOMORROW...HIGH CONFIDENCE. MAINLY VFR. WINDS SHIFT TO THE SW...BUT SHOULD REMAIN AROUND 10 KT OR LESS. KBOS TERMINAL...HIGH CONFIDENCE IN TRENDS...TIMING MAY BE OFF A BIT. KBDL TERMINAL...HIGH CONFIDENCE IN TRENDS....TIMING MAY BE OFF A BIT. OUTLOOK /SUNDAY THROUGH TUESDAY/... TONIGHT THROUGH SUNDAY...HIGH CONFIDENCE. VFR. MONDAY-TUESDAY...LOW CONFIDENCE. MVFR/IFR CONDITIONS IN SNOW OR RAIN/SNOW MIX. NORTHEAST WINDS GUSTING 20-30 KNOTS ALONG THE COAST.
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&& .MARINE... 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... NORTHERLY WIND GUSTS PICK UP THROUGH THE MORNING...WITH GUSTS BETWEEN 30 AND 35 KT ALONG THE SOUTHERN WATERS...AND 35-45 KT ON THE EASTERN WATERS. GALE WARNINGS HAVE BEEN ISSUED FOR MUCH OF THE DAY. SEAS BECOME HIGH...MAINLY 8-10 FT ON THE SE OCEAN WATERS. OTHERWISE...EXPECT A PERIOD OF RAIN/FOG ACROSS THE WATERS WITH A POSSIBLE CHANGE TO SNOW NEAR THE EASTERN SHORELINES. OUTLOOK /SUNDAY THROUGH TUESDAY/...MODERATE CONFIDENCE... TONIGHT...DIMINISHING NORTHWEST WINDS AROUND 30 KNOTS EARLY AND POPPING UNDER 25 KNOTS AFTER MIDNIGHT. SEAS AS HIGH AS 14 FEET ON THE OUTER WATERS WILL SUBSIDE OVERNIGHT TO 5-7 FEET BY MORNING. SMALL CRAFT ADVISORY WILL BE NEEDED FOR MOST WATERS DURING THE NIGHT. SATURDAY-SUNDAY...SOUTHWEST WINDS SATURDAY BELOW 25 KNOTS BUT GUSTING NEAR 25 KNOTS EAST OF CAPE ANN SATURDAY NIGHT. SEAS DIMINISH SATURDAY BUT THEN RETURN TO NEAR 5 FEET EAST OF CAPE ANN SATURDAY NIGHT. NORTHWEST WINDS SUNDAY BUT WINDS AND SEAS WILL BE BELOW SMALL CRAFT CRITERIA. MONDAY-TUESDAY...NORTH WINDS TURN NORTHEAST AND INCREASE TO AT LEAST NEAR 30 KNOTS EACH DAY. DEPENDING ON THE EVENTUAL BEHAVIOR OF THE TWO COASTAL LOW PRESSURE AREAS PASSING BY...THERE IS POTENTIAL FOR WINDS TO REACH 35-40 KNOTS AT THIS TIME. LOW CONFIDENCE FOR GALES AT THIS TIME...BUT THE POTENTIAL IS THERE. WINDS TURN BACK TO NORTHWEST TUESDAY NIGHT. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...WINTER STORM WARNING UNTIL 3 PM EST THIS AFTERNOON FOR CTZ002>004. MA...WINTER STORM WARNING UNTIL 5 PM EST THIS AFTERNOON FOR MAZ019>021. WINTER STORM WARNING UNTIL 3 PM EST THIS AFTERNOON FOR MAZ004>007-009-011>018-026. WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR MAZ002-003-008-010. WIND ADVISORY UNTIL 7 PM EST THIS EVENING FOR MAZ022>024. WINTER WEATHER ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR MAZ022. RI...WINTER STORM WARNING UNTIL 5 PM EST THIS AFTERNOON FOR RIZ007. WINTER STORM WARNING UNTIL 3 PM EST THIS AFTERNOON FOR RIZ001>006. MARINE...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR ANZ231>235-237- 250-254>256. SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ230- 236-251.
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&& $$ SYNOPSIS...WTB/DUNTEN NEAR TERM...DOODY SHORT TERM...DUNTEN LONG TERM...WTB AVIATION...WTB/DOODY MARINE...WTB/DUNTEN

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