Area Forecast Discussion
Issued by NWS Boston, MA

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715 FXUS61 KBOX 050630 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 130 AM EST FRI FEB 5 2016 .SYNOPSIS... COLD FRONT STALLING OFFSHORE WILL PROVIDE A FOCUS FOR LOW PRESSURE TO TRAVEL ALONG EARLY TOMORROW. 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 TUESDAY. && .NEAR TERM /UNTIL 1 PM THIS AFTERNOON/... 130 AM UPDATE... *** WESTWARD TREND IN THE SYSTEM HAS ALLOWED FOR WARNINGS AND ADVISORIES TO BE EXPANDED *** BUSY EVENING AS WE CONTINUE TO EVALUATE THE LATEST DATA AND TREND FOR THIS UPCOMING 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. STILL SOME UNCERTAINTY ON WHEN EXACTLY SWITCH OVER WILL TAKE PLACE FROM RAIN TO SNOW...BUT HAVE RECEIVED A FEW REPORTS IN WORCESTER AND DUAL-POL RADAR IS ALSO SHOWING A MIX OR WEST SNOW ACROSS WINDHAM COUNTY THANKS TO THE HEAVIER ECHOS. P-TYPE AND CHANGE OVER TIMING... MOISTURE WILL CONTINUE TO SPILL INTO SOUTHERN NEW ENGLAND TONIGHT AND INTO TOMORROW AS COASTAL LOW MOVES ALONG STALLED COLD FRONT. THIS PRECIP SHIED WILL EXPAND FARTHER WESTWARD THEN ORIGINALLY FORECAST...WHICH IS THE LATEST TREND IN ALL OF THE GUIDANCE. STILL SOME QUESTIONS ON THE EXACT TIMING OF CHANGE OVER FROM RAIN TO SNOW. A FEW LOCATIONS HAVE ALREADY REPORTED SOME SLEET OR SNOW MIXING IN. SOUNDINGS AND SOME HI- RES GUIDANCE SUGGEST THAT SOME LOCATIONS IN THE HIGHER ELEVATIONS WILL CHANGE OVER AROUND 7-9Z. WHILE THE REST OF WESTERN AND CENTRAL MASS AND CT WILL CHANGE CLOSE TO 10-11Z. AGREE WITH THE TIMES HEAVIER BANDS OF PRECIP SHOULD BE MOVING THROUGH AND WILL DRAG THE COOLER AIR ALOFT DOWN TO THE SURFACE. VERY 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. ALSO CONCERNED ABOUT THE EAST SLOPE OF THE BERKSHIRES. FIRST RUN AT THE SNOW AMOUNTS BUT THEM CLOSE TO 3 INCHES. HOWEVER BEING ON THE EDGE...DRY AIR MAY ERODE THE PRECIP SHIELD AND LIMIT HOW MUCH TRULY FALLS ON THEM. WILL HAVE TO CONTINUE TO WATCH. ALSO 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. && .SHORT TERM /1 PM THIS AFTERNOON THROUGH 6 PM SATURDAY/... THE MORE DYNAMIC NATURE OF THIS SYSTEM IN RELATION TO PREVIOUS PROGS SUGGEST A SLOWER END AS WELL. 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. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... HIGHLIGHTS... * DRY WEATHER THIS WEEKEND * ANOTHER COASTAL STORM WILL AFFECT THE REGION MONDAY OR TUESDAY * DRY WEATHER RETURNS THE MIDDLE OF NEXT WEEK FRIDAY NIGHT INTO SUNDAY...MODERATE CONFIDENCE. HIGH PRESSURE BUILDS OVER REGION FRIDAY NIGHT INTO SATURDAY WITH DRY WEATHER EXPECTED. LOW PRESSURE TRACKING ACROSS EASTERN CANADA WILL SWING A COLD FRONT THROUGH SOUTHERN NEW ENGLAND SUNDAY...BUT THE BEST DYNAMICS/MOISTURE REMAIN FAR ENOUGH TO OUR N THAT WE SHOULD REMAIN DRY. HOWEVER...THE FRONT WILL BRING COLDER AIR INTO OUR REGION BY SUNDAY NIGHT WHICH SETS STAGE FOR POTENTIALLY STORMY WEATHER EARLY NEXT WEEK. MONDAY INTO TUESDAY...LOW CONFIDENCE. MODELS CONTINUE TO STRUGGLE WITH THE STORM POTENTIAL FOR EARLY NEXT WEEK. BOTH MODELS CONTINUE TO INDICATE A STORM OCCURRING DURING THIS TIME FRAME BUT DIFFER ON HOW THEY HANDLE THE STORM. EXPECT THIS STORM TO COME MORE INTO FOCUS IN THE NEXT DAY OR TWO AS THE SHORTWAVES MOVE ON TO THE WEST COAST AND ARE BETTER SAMPLED. HAVE HIGH CONFIDENCE IN SOME SORT OF STORM OCCURRING DURING THIS TIME FRAME. HOWEVER...THE DETAILS ARE STILL VERY UNCERTAIN. 12Z ECMWF PRODUCES TWO COASTAL STORMS...ONE OF WHICH WILL PASS WELL SOUTHEAST OF THE BENCHMARK ON MONDAY /WITH LITTLE EFFECT ON SOUTHERN NEW ENGLAND/...AND THE SECOND OF WHICH PASSES DIRECTLY OVER THE BENCHMARK ON TUESDAY. 12Z GFS PRODUCES A SINGLE COASTAL SYSTEM THAT DEVELOPS OVER THE TRI-STATE AREA AND MOVES OVER SOUTHERN NEW ENGLAND TUESDAY. THIS WOULD RESULT IN WIDELY DIFFERENT TEMPERATURE PROFILES THAN THE ECMWF. DUE TO THE WIDE VARIATIONS IN THESE DETERMINISTIC SOLUTIONS...WE ARE BASING FORECAST MORE ON ENSEMBLES AND WILL UTILIZE CONSENSUS BLEND TO WORK OUT DETAILS FOR NOW. THIS RESULTS IN SNOW DEVELOPING LATE MON INTO TUE...BUT DESPITE COLD TEMPERATURES ALOFT WE WILL PROBABLY BE DEALING WITH WARMTH IN BOUNDARY LAYER WHICH WILL GIVE US ISSUES WITH RAIN/SNOW MIX OR EVEN RAIN...PRIMARILY FROM PROVIDENCE AND BOSTON TO CAPE COD AND ISLANDS. SETUP RIGHT NOW FAVORS HIGHER SNOWFALL AMOUNTS ACROSS INTERIOR...BUT AGAIN...CONFIDENCE IS LOW AND THERE COULD BE SIGNIFICANT ADJUSTMENTS TO FORECAST IN COMING DAYS. FOR NOW...THE POTENTIAL IS THERE BUT WE NEED TO SEE HOW THESE TWO SHORT WAVES EVOLVE AS THEY ENTER WEST COAST AND WORK THEIR WAY ACROSS COUNTRY. WEDNESDAY...LOW CONFIDENCE. AGAIN MODEL SPREAD IS HIGH AT THIS TIME RANGE GIVEN UNCERTAINTIES IN HOW MON/TUE EVOLVES. BUT WE DO EXPECT TO SEE DRYING IN WAKE OF SYSTEM WITH SEASONABLE TEMPERATURES. THURSDAY...MODERATE CONFIDENCE. WHILE SOMEWHAT DEPENDENT ON HOW THE EARLY WEEK SYSTEM PLAYS OUT...THERE IS AGREEMENT AMONGST THE MODELS ON HIGH PRESSURE BUILDING INTO SOUTHERN NEW ENGLAND. EXPECT SEASONABLE TEMPERATURES. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SATURDAY/... THROUGH 18Z...MODERATE CONFIDENCE. THE RAIN SHIELD CONTINUES TO EXPAND NORTHWEST...COVERING MOST OF SRN NEW ENGLAND BY ABOUT 10-12Z. THIS WILL ALSO BRING ABOUT MVFR/IFR CONDITIONS DUE TO LOW CIGS/VSBYS. THEN...AFTER 09Z ESPECIALLY THE RAIN WILL CHANGE TO SNOW FROM NW- SE UNTIL IT/S ALL SNOW AWAY FROM THE ISLANDS BY ABOUT 16Z. SOME ACCUMULATION IS POSSIBLE...ESPECIALLY ON GRASSY SFCS. HOWEVER RUNWAYS MAY RECEIVE A PLOWABLE AMOUNT MAINLY E OF AN IJD- ORH-BVY LINE. THIS WILL BE ACCOMPANIED BY MAINLY IFR CONDITIONS. AFTER 18Z TOMORROW...MODERATE CONFIDENCE. SNOWS/RAIN COME TO AN END AND VERY QUICK IMPROVEMENT TO VFR EXPECTED. KBOS TERMINAL...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN TIMING OF PRECIP AND CHANGE TO SNOW EARLY THIS MORNING. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF DUE TO UNCERTAINTY IN PRECIP TIMING. OUTLOOK /SATURDAY NIGHT THROUGH TUESDAY/... FRIDAY NIGHT THROUGH SUNDAY...HIGH CONFIDENCE. VFR. MONDAY AND TUESDAY...LOW CONFIDENCE. MVFR/IFR POSSIBLE IN RAIN OR SNOW...ESPECIALLY LATE. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SATURDAY/...HIGH CONFIDENCE. THROUGH TONIGHT... WINDS GRADUALLY SHIFT MAINLY TO THE N THROUGH THE NIGHT...BUT WITH BOTH SEAS AND GUSTS BELOW SCA THRESHOLDS. THEREFORE...LEFTOVER SMALL CRAFT ADVISORIES WILL BE DROPPED BUT IN FAVOR OF A GALE WARNING...MORE ON THAT BELOW. TOMORROW... 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 /SATURDAY NIGHT THROUGH TUESDAY/...MODERATE CONFIDENCE... FRIDAY NIGHT...HIGH CONFIDENCE. WINDS AND SEAS DIMINISH AS HIGH PRESSURE STARTS TO BUILD OVER THE WATERS. SCA LIKELY NEEDED FOR LINGERING SEAS. SATURDAY INTO SUNDAY...MODERATE CONFIDENCE. WINDS AND SEAS MAINLY BELOW SCA. LINGERING 5 FOOT SEAS SATURDAY MORNING. MONDAY AND TUESDAY...LOW CONFIDENCE. EXPECT INCREASING N/NE WINDS AHEAD OF COASTAL LOW. SCA CONDITIONS LIKELY WITH 25-30KT GUSTS AND SEAS BUILDING TO 5 FT OR HIGHER. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...WINTER STORM WARNING UNTIL 3 PM EST THIS AFTERNOON FOR CTZ003- 004. WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR CTZ002. MA...WINTER WEATHER ADVISORY FROM 7 AM THIS MORNING TO 3 PM EST THIS AFTERNOON FOR MAZ019>022. WINTER STORM WARNING UNTIL 3 PM EST THIS AFTERNOON FOR MAZ004>007-012>018-026. WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR MAZ003-010-011. RI...WINTER WEATHER ADVISORY FROM 7 AM THIS MORNING TO 3 PM EST THIS AFTERNOON FOR RIZ007. WINTER STORM WARNING UNTIL 3 PM EST THIS AFTERNOON FOR RIZ001>006. MARINE...GALE WARNING FROM 7 AM THIS MORNING TO 7 PM EST THIS EVENING FOR ANZ231>235-237-250-254>256. SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 7 PM EST THIS EVENING FOR ANZ230-236-251. && $$ SYNOPSIS...DOODY/RLG NEAR TERM...DUNTEN SHORT TERM...DUNTEN LONG TERM...RLG AVIATION...DUNTEN/RLG MARINE...DOODY/RLG

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