Area Forecast Discussion
Issued by NWS Boston, MA

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044 FXUS61 KBOX 040008 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 708 PM EST WED FEB 3 2016 .SYNOPSIS... A SLOW MOVING COLD FRONT WILL MOVE ACROSS THE REGION TONIGHT. AHEAD OF THE FRONT...EXPECT WIDESPREAD RAIN WITH POSSIBLY A RUMBLE OF THUNDER. THE COLD FRONT WILL STALL JUST OFF THE COAST THURSDAY...THEN LOW PRESSURE WILL DEVELOP ALONG THE MID ATLC COAST THU NIGHT AND TRACK ALONG THE FRONT PASSING SOUTH AND EAST OF NANTUCKET FRIDAY. THIS STORM WILL LIKELY BRING ACCUMULATING SNOW TO SOUTHEAST NEW ENG LATE THU NIGHT INTO FRIDAY. HIGH PRESSURE BRINGS DRY WEATHER OVER THE WEEKEND. A COASTAL STORM SHOULD AFFECT THE REGION LATER MONDAY INTO TUESDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 7 PM UPDATE... WIDESPREAD SHOWERS ACROSS SNE THIS EVENING ASSOCD WITH STRONG WARM ADVECTION AND ENHANCED BY LOW LEVEL CONVERGENCE ALONG THE NOSE OF THE LOW LEVEL JET. MODELS INDICATING SOME DRYING ALOFT MOVING INTO WESTERN NEW ENG THIS EVENING WHICH WILL RESULT IN RAIN DECREASING WHILE ACTIVITY BECOMES FOCUSED ACROSS SE NEW ENG ALONG THE AXIS OF THE SLOW MOVING LOW LEVEL JET. ADJUSTED POPS TO REFLECT THIS THINKING. WARM FRONT HAS LIFTED TO THE N OF THE REGION AS TEMPS HAVE SOARED INTO AND THROUGH THE 50S. WILL LIKELY SEE TEMPS REACH 60 DEGREES IN THE COASTAL PLAIN OVERNIGHT. COLD FRONT MOVES INTO W NEW ENG LATE TONIGHT WITH TEMPS COOLING INTO THE 40S HERE TOWARD DAYBREAK...BUT REMAINING IN THE 50S ELSEWHERE. AXIS OF LOW LEVEL JET WILL MOVE TO E NEW ENG THIS EVENING THEN ACROSS SE NEW ENG COAST OVERNIGHT. STRONG LOW LEVEL INVERSION IN PLACE WHICH WILL LIMIT STRONGER GUSTS FROM REACHING THE SURFACE. FOR THE MOST PART...EXPECTING WINDS TO GUST UP TO 30-40 MPH WITH THE STRONGEST WINDS SHIFTING TO THE CAPE/ISLANDS OVERNIGHT. IF ANY HEAVIER RAIN OR ISOLATED THUNDERSTORMS ARE ABLE TO TAP INTO THE STRONGER WINDS ALOFT...WE MAY SEE A FEW HIGHER GUSTS IN AND AROUND THOSE STORMS TONIGHT. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... THE COLD FRONT STALLS OFF THE SOUTH COAST OF SOUTHERN NEW ENGLAND THURSDAY MORNING. THIS WILL KEEP SOME SHOWERS ON THE SOUTH COAST THROUGH MUCH OF THE DAY. THE BIG STORY FOR THURSDAY WILL BE THE TEMPERATURES. AFTER STARTING OUT WITH MINS WARMER THAN OUR NORMAL MAXES...TEMPS WILL CLIMB QUICKLY THROUGH THE MORNING INTO THE 50S TO EVEN AROUND 60 ON THE COASTAL PLAIN. AS WINDS SHIFT TO THE NORTHWEST DURING THE AFTERNOON...EXPECT TEMPERATURES TO COOL BACK INTO THE 40S. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... HIGHLIGHTS... * RAIN CHANGING TO ACCUMULATING SNOW LATE THU NIGHT INTO FRIDAY ACROSS SE NEW ENG * DRY WEATHER THIS WEEKEND * ANOTHER COASTAL STORM MAY AFFECT THE REGION SOMETIME MONDAY OR TUESDAY THURSDAY NIGHT INTO FRIDAY... ** WINTER STORM WATCH ISSUED FOR FAR SE MA AND CAPE COD AND MARTHAS VINEYARD *** DIFFICULT FORECAST WITH RESPECT TO TIMING OF CHANGEOVER FROM RAIN TO SNOW AND POTENTIAL SNOW ACCUMULATIONS NEAR THE COAST LATE THU NIGHT INTO FRIDAY. MODELS ALL SHOW A SHARP MID LEVEL TROF AXIS BACK TO THE WEST WITH RATHER POTENT MID LEVEL SHORTWAVE ROUNDING THE BASE OF THE TROF AND LIFTING NE OFF THE MID ATLC COAST. THIS WILL INDUCE A FRONTAL WAVE DEVELOPING ALONG THE EXISTING BAROCLINIC ZONE OFF THE COAST AND TRACKING SE OF THE BENCHMARK FRIDAY. THE DIFFICULTY WITH THE FORECAST INVOLVES THE WESTWARD EXTENT OF SIGNIFICANT QPF MOVING INTO SNE AND TIMING OF CHANGEOVER FROM RAIN TO SNOW AS THE COLUMN COOLS FROM WEST TO EAST WITH THE APPROACH OF THE MID LEVEL TROF. ALSO THERE IS A SHARP QPF GRADIENT ON THE NW FRINGE OF THE PRECIP FIELD WHICH ADDS TO THE UNCERTAINTY. TIMING OF CHANGEOVER... PRECIP COMES IN AS RAIN ALONG THE COAST THU EVENING. MODELS ARE IN REASONABLE GOOD AGREEMENT ON TIMING OF CHANGEOVER WITHIN A FEW HOURS WITH ECMWF LATER THAN NAM/GFS BUT IT IS ALSO HEAVIER WITH QPF. WE USED A BLEND OF PARTIAL THICKNESS DATA WHICH SUGGESTS CHANGEOVER 06- 09Z SE MA/RI AND 09-12Z CAPE/ISLANDS. QPF... UKMET IS ON THE WESTERN EDGE OF THE MODEL ENVELOPE AND BRINGS SIGNIFICANT QPF INTO SNE WITH AMOUNTS 1-2 INCHES ACROSS E NEW ENG BUT IS A WARMER SOLUTION. ECMWF ALSO QUITE ROBUST WITH 0.50 INCHES TO WEST OF I95 CORRIDOR AND 1 INCH TO WEST OF THE CAPE COD CANAL AND A GOOD CHUNK OF THIS FALLS AFTER THE CHANGEOVER WHICH WOULD RESULT IN A LARGE SWATH OF GREATER THAN 6 INCHES SNOW ACCUM FOR MUCH OF HE COASTAL PLAIN. 12Z GFS AND NAM ARE ON THE EASTERN ENVELOPE...CONFINING HEAVY QPF TO CAPE/ISLANDS WITH LIGHT AMOUNTS BACK TO THE I95 CORRIDOR...BUT 18Z NAM HAS TRENDED EAST AND IS A SHUTOUT FOR BOS/PVD WITH ONLY LIGHT QPF AFTER CHANGEOVER FOR CAPE/ISLANDS. VERY DIFFICULT FORECAST SO WE ARE LEANING TOWARD A BLEND OF AVAILABLE GUIDANCE AS WELL AS ECMWF EPS MEAN. GIVEN SHARPNESS OF THE UPPER TROF AND STRENGTH OF THE SHORTWAVE EXPECT THIS TO BACK FLOW ENOUGH TO PUSH HEAVIER QPF ACROSS CAPE/ISLANDS AND POSSIBLY FAR SE MA NEAR THE CANAL BUT MUCH LESS CONFIDENCE GETTING FURTHER NW. SNOWFALL... HIGHEST CONFIDENCE OF 6 INCHES ACCUM IS THE AREA NEAR THE CAPE COD CANAL SO WE ISSUED A WATCH FOR FAR SE MA AND CAPE COD...INCLUDING MARTHAS VINEYARD. SNOW COULD BE HEAVY AT TIMES VERY LATE THU NIGHT INTO FRI MORNING WHICH MAY AFFECT THE MORNING COMMUTE. DESPITE MORE QPF FOR NANTUCKET...WE EXPECT LESS SNOWFALL THERE DUE TO LATER TIMING OF CHANGEOVER AND MARGINAL BOUNDARY LAYER WHICH WILL LEAD TO SOME MELTING. OBVIOUSLY WITH SHARP MOISTURE/QPF GRADIENT ON THE NW FRINGE OF THE PRECIP SHIELD THERE IS BIG BUST POTENTIAL. FURTHER EAST AND ITS JUST MINOR ACCUM FOR CAPE COD...BUT FURTHER WEST AND HEAVY SNOW COULD EXTEND BACK ACROSS BOS/PVD WITH MORE RAIN FOR THE CAPE/ISLANDS. OUR PROBABILISTIC SNOWFALL MAPS AND BEST/WORST CASE SCENARIOS TRY TO COMMUNICATE THE EXPECTED RANGE OF EXPECTATIONS. WATCH WAS BASED ON A 50 PERCENT PROBABILITY OF 6 INCHES WITH LIKELIHOOD OF AT LEAST ADVISORY LEVEL SNOW FOR THIS AREA. INTERESTING TO NOTE THAT THERE ARE MANY ECMWF EPS MEMBERS WITH SIGNIFICANT SNOWFALL BACK ACROSS COASTAL PLAIN. THIS MAY BE TOO AGGRESSIVE...BUT 51 MEMBER ECMWF EPS HAS 50 PERCENT PROBS FOR 6 INCHES SE MA AND 90 PERCENT FOR 3 INCHES. IMPACTS... THIS WILL BE A WET SNOW AND IF HEAVY SNOW MATERIALIZES THERE WILL BE POTENTIAL FOR POWER OUTAGES DUE TO ACCUMULATION ON TREES AND POWER LINES. SATURDAY INTO SUNDAY...MODERATE CONFIDENCE. HIGH PRESSURE BUILDS OVER REGION SAT WITH DRY WEATHER EXPECTED. CLIPPER LOW TRACKING ACROSS EASTERN CANADA WILL SWING A COLD FRONT THROUGH SOUTHERN NEW ENGLAND SUN...BUT BEST DYNAMICS/MOISTURE REMAIN FAR ENOUGH TO OUR N THAT WE SHOULD REMAIN DRY. HOWEVER FRONT WILL BRING COLDER AIRMASS INTO REGION BY SUN NIGHT WHICH SETS STAGE FOR POTENTIALLY STORMY WEATHER EARLY NEXT WEEK. MONDAY INTO TUESDAY...LOW CONFIDENCE. MODELS CONTINUE TO STRUGGLE WITH HANDLING OF TWO SHORTWAVES CURRENTLY OVER PACIFIC...WHICH IS TO BE EXPECTED UNTIL THU OR FRI WHEN THESE FEATURES BECOME BETTER SAMPLED. SO EXPECT TO SEE WOBBLES OR EVEN WILD SWINGS IN THESE DETERMINISTIC SOLUTIONS UNTIL THEN. 12Z ECMWF NOW PUTS MORE EMPHASIS ON FIRST SHORT WAVE...WHICH RESULTS IN COASTAL LOW AFFECTING SOUTHERN NEW ENGLAND MON BUT IS MORE OF A GLANCING BLOW DUE TO A MORE OFFSHORE TRACK. 12Z GFS PUTS MORE FOCUS ON SECOND SHORT WAVE AND AS A RESULT ITS COASTAL LOW HAS MORE OF AN IMPACT ON SOUTHERN NEW ENGLAND TUE. DUE TO 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 MOVING INTO REGION LATER 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. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY/...MODERATE CONFIDENCE. TONIGHT...MVFR/IFR CONDITIONS CONTINUE WITH RAIN SLOWLY DIMINISHING FROM NORTHWEST TO SOUTHEAST. RAIN WILL LIKELY CONTINUE THROUGH THE NIGHT ALONG THE SOUTH COAST...CAPE...AND ISLANDS. WILL SEE SOME IMPROVEMENT TO VFR ACROSS THE NORTHWESTERN TERMINALS TOWARDS 12Z. POTENTIAL FOR ISOLD TSRA ALONG THE SOUTH COASTS OF RI/MA CONTINUES. AREAS OF LLWS ACROSS SNE THIS EVENING...SHIFTING TO SE NEW ENG OVERNIGHT. THURSDAY...QUICK IMPROVEMENT TO VFR ACROSS THE REMAINDER OF THE AREA THROUGH 15Z THOUGH CLOUDS WILL LINGER THROUGH MUCH OF THE DAY. KBOS TERMINAL...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN TIMING OF WINDS/PRECIP. KBDL TERMINAL...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN TIMING OF WINDS/PRECIP. OUTLOOK /THURSDAY NIGHT THROUGH MONDAY/...MODERATE CONFIDENCE THU NIGHT INTO FRIDAY...HIGH CONFIDENCE IN IFR/LIFR DEVELOPING SE NEW ENG AND CAPE/ISLANDS WITH RAIN CHANGING TO ACCUMULATING SNOW LATE THU NIGHT INTO FRI MORNING...IMPROVING FRI AFTERNOON. MAINLY VFR FURTHER INTO THE INTERIOR. LOW CONFIDENCE ON WHERE TRANSITION FROM IFR TO VFR OCCURS. SATURDAY AND SUNDAY...VFR. MONDAY...MVFR 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 THURSDAY/...HIGH CONFIDENCE. TONIGHT...MODERATE CONFIDENCE. STRONG SOUTHERLY WINDS WILL CONTINUE TO BUILD THROUGH THE EVENING AND INTO TONIGHT. HAVE UPGRADED THE SOUTHERN INNER WATERS TO GALE WARNINGS FOR THIS AFTERNOON AND INTO TONIGHT. SEAS INCREASE TO 6 TO 10 FEET ON THE OUTER WATERS AS A COLD FRONT MOVES ACROSS THE WATERS LATE TONIGHT INTO EARLY THURSDAY MORNING. THURSDAY...MODERATE CONFIDENCE. SEAS DIMINISH SLOWLY...ESPECIALLY ON THE EASTERN WATERS WHERE THE FRONT WILL MOVE THROUGH EARLIER. THE COLD FRONT STALLS ACROSS THE SOUTHERN WATERS WHICH WILL SLOW THE DIMINISHING OF THE SEAS. SMALL CRAFT ADVISORIES WILL NEED TO CONTINUE FOR SEAS ON MOST OF THE OUTER WATERS. SOUTHERLY WINDS WILL SLOWLY SHIFT TO THE NORTHWEST DURING THE AFTERNOON...REMAINING BELOW SMALL CRAFT CRITERIA. OUTLOOK /THURSDAY NIGHT THROUGH MONDAY/...MODERATE CONFIDENCE... THU NIGHT INTO FRIDAY...INCREASING N WINDS LATE THU NIGHT INTO FRI WITH GUSTS TO 25 KT POSSIBLE OVER S WATERS. VSBYS REDUCED IN RAIN...WHICH WILL CHANGE TO SNOW LATE THU NIGHT AND FRI MORNING. SAT INTO SUN...WINDS AND SEAS REMAIN BELOW SCA. MON...CONFIDENCE IS LOW BUT EXPECT INCREASING N/NE WINDS AHEAD OF COASTAL LOW. SCA CONDITIONS POSSIBLE WITH 25-30KT GUSTS AND SEAS BUILDING TO 5 FT OR HIGHER ON OUTER WATERS. && .CLIMATE... RECORD HIGHS FOR FEB 4TH... BOS...64/1991 BDL...64/1991 PVD...66/1991 ORH...61/1991 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...WINTER STORM WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY AFTERNOON FOR MAZ018>023. RI...NONE. MARINE...GALE WARNING UNTIL 4 AM EST THURSDAY FOR ANZ231-232-255-256. GALE WARNING UNTIL 1 AM EST THURSDAY FOR ANZ233>237. SMALL CRAFT ADVISORY UNTIL 4 AM EST THURSDAY FOR ANZ230. GALE WARNING UNTIL 7 AM EST THURSDAY FOR ANZ250-254. SMALL CRAFT ADVISORY UNTIL 1 PM EST THURSDAY FOR ANZ251. && $$ SYNOPSIS...KJC/RLG NEAR TERM...KJC/RLG SHORT TERM...RLG LONG TERM...KJC/JWD AVIATION...KJC/RLG MARINE...KJC/RLG CLIMATE...

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