Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 220607 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 107 AM EST THU JAN 22 2015 .SYNOPSIS... A STRENGTHENING COASTAL LOW WILL PASS SOUTHEAST OF THE BENCHMARK TONIGHT INTO TOMORROW. ANTICIPATE ACCUMULATING SNOWFALL ACROSS THE CAPE AND THE ISLANDS WITH THIS SYSTEM. HIGH PRESSURE WILL THEN BUILD INTO NEW ENGLAND THURSDAY NIGHT AND FRI BRINGING MORE DRY...SEASONABLE CONDITIONS. A SIGNIFICANT COASTAL STORM IS APPEARING MORE LIKELY SATURDAY INTO SATURDAY NIGHT...BUT THE RAIN/SNOW LINE AND NORTHWEST EXTENT OF HEAVY PRECIPITATION REMAINS HIGHLY UNCERTAIN. DRY WEATHER FOLLOWS SUNDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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PROFILE HAS MOISTEN UP OVER THE PAST FEW HOURS ALLOWING FOR SNOW TO FALL ACROSS THE SOUTHERN HALF OF THE REGION. WATCHING 2 AREAS OF BANDING...ONE OVER NEWPORT/LITTLE COMPTON REGION AND THE OTHER OVER SOUTHWESTERN CONNECTICUT. BOTH OF THESE BANDS CAN DROP A QUICK INCH OF SNOW AND LOWER VSBYS BELOW 1 SM. OTHERWISE SNOW IS OVERSPREADING ACROSS THE CAPE AND ISLAND PER WEBCAMS AND OBSERVATIONS. EXPECT SNOW TO CONTINUE THROUGH THE MORNING HOURS ACROSS THE CAPE AND THE ISLANDS AS COASTAL LOW MOVING SOUTH OF THE BENCHMARK. THIS LOW IS BEGINNING TO STRENGTHEN AND WILL PULL BULK OF THE PRECIP OFFSHORE OVER THE NEXT FEW HOURS. INVERTED TROUGH WILL SET UP AS THE LOW PULLS OFFSHORE. THIS WILL ALLOW FOR LINGERING SNOW SHOWERS TO MOVE ONTO THE MASS EAST COASTLINE. SOME GUIDANCE MEMBERS PUSHED PRECIP ALL THE WAY TO THE WORCESTER HILLS. WILL CONTINUE TO MONITOR THE CURRENT SNOWFALL.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... THURSDAY...COASTAL LOW MOVES OFF TO THE EAST. NO STRONG HIGH IN POSITION OVER LAND AND SO MOST OF THE PRESSURE GRADIENT STARTS THE DAY OFFSHORE WITH THE LOW. IT MAY BE BREEZY FIRST THING IN THE MORNING WHEN THE COASTAL LOW IS CLOSEST...BUT LESS WIND IN THE AFTERNOON. WITH THE SHIFTING OF THE WIND...EXPECT SNOW TO TAPER OFF IN THE MORNING WITH AT LEAST PARTIAL CLEARING IN THE AFTERNOON. WIND SPEEDS MAY BE BRIEFLY FAVORABLE FOR OCEAN EFFECT SNOW SHOWERS THURSDAY MORNING. BUT PROJECTED TEMPERATURE PROFILES ARE MARGINAL AT BEST. BASED ON TEMPS ALOFT...PROJECT MAX SFC TEMPS WILL BE IN THE 30S. THURSDAY NIGHT...UPPER SHORTWAVE/SECONDARY FRONT SWINGS THROUGH. BUT THE AIRMASS LOOKS RATHER DRY SO WE HAVE TRENDED TO CLEARING SKIES. TEMPS ALOFT COOL BY 3C-4C COMPARED WITH TONIGHT...SO HAVE MIN TEMPS 5-10F COOLER THAN TONIGHT. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... HIGHLIGHTS... * COASTAL STORM EXPECTED SAT INTO SAT NIGHT * RAIN VS. WET SNOW LINE SAT/SAT NIGHT UNCERTAIN * TRACK SUGGESTS SNOW POTENTIAL A BIT FURTHER WEST * STRONG TO DAMAGING WINDS POSSIBLE SOUTHEAST NEW ENGLAND SAT NIGHT * ANOTHER SHOT AT SNOW LATER MONDAY INTO TUESDAY OVERVIEW AND MODEL PREFERENCES... THE KEY TO THE EXTENDED FORECAST PERIOD CONTINUES TO BE THREAT FOR COASTAL STORM WITH SOME MODERATE TO POTENTIALLY HIGH IMPACT SAT AND SAT NIGHT. MODELS ARE ALL CONTINUING TO CONVERGE ON THE TRACK OF A BOMBING LOW PRES CENTER EXPECTED TO MOVE WITHIN ABOUT 50 NM OF THE 40/70 BENCHMARK. LATEST RUNS SUGGEST SLIGHTLY INSIDE WITH BETTER CLUSTERING IN THE ECENS AND GEFS MEMBERS INSIDE THAN OUT /EVEN THOUGH THE OPERATIONAL GFS AT 12Z SLID SLIGHTLY TO THE SE/. SO WHILE CONFIDENCE IS CERTAINLY HIGH IN SOME IMPACTS...THE QUESTION REMAINS EXACTLY HOW MUCH AND WHERE. AT ISSUE IS THE LACK OF A BLOCKING HIGH PRES TO THE N WITH THIS FEATURE...AND ENSEMBLES CONTINUE TO INDICATE A POSITIVE TREND IN NAO AND AO SUGGESTING A PROGRESSIVE STORM DESPITE THE RAPID INTENSIFICATION. THE LACK OF BLOCKING WILL ALLOW WARMER AIR INTO TO REACH FURTHER N OF THE SYSTEM...AND MITIGATE MID LVL FRONTOGENESIS FOR BANDING SOMEWHAT. GIVEN THIS UNCERTAINTY...BUT THE SLIGHT W TREND...WILL ADJUST THERMAL PROFILES JUST SLIGHTLY WARMER...BUT NOT BY MUCH WITH THIS UPDATE. THIS STILL KEEPS THE HIGHEST SNOWFALL POTENTIAL CLOSE TO THE I-95 CORRIDOR. BEYOND THE WEEKEND...A BLEND OF GFS/ECMWF AND PERSISTENCE WILL BE USED AS A BASELINE. DETAILS... FRI AND FRI NIGHT... BRIEF RIDGE OF HIGH PRES NOSES ACROSS THE REGION FROM THE S THROUGH THE PERIOD. HIGHS REMAIN WITHIN A FEW DEGREES OF THE FREEZING MARK...WHILE OVERNIGHT MINS ARE EXPECTED TO BE SLIGHTLY WARMER...WITH INCREASING CLOUDS BETWEEN THE NRN AND SRN STREAM SYSTEMS. SAT INTO EARLY SUN... AS MENTIONED ABOVE...THREAT FOR COASTAL STORM WITH POTENTIAL WINTER HEADLINES AS RAPIDLY DEEPENING LOW PRES HEADS SUB 980 HPA AND MAKES IT/S CLOSEST PATH NEAR THE BENCHMARK AT AROUND 00Z SUN. THERMAL PROFILES ARE GOING TO BE KEY HERE...AND HAVE MADE ONLY SLIGHT UPWARD /AND WESTWARD/ SHIFT IN THE TEMP PROFILE. NOTE MODERATE OVERALL LIFT IN THE WARM CONVEYOR...BUT THE LACK OF UPSTREAM BLOCKING SUGGESTS THAT MID LVL BAROCLINICITY WILL BE LACKING. STILL NOTE MODERATE OMEGA WITHIN THE DENDRITE ZONE ON SOUNDINGS...SO THE SYSTEM WILL BE PRODUCING SOME BANDED SNOW...THE QUESTION WILL BE WHERE THE LOWEST LVLS ARE ABLE TO CONTINUALLY SUPPORT SNOW GROWTH/SUPPORT TO THE SFC AS TEMP PROFILES INTO THE WORCESTER HILLS ARE ISOTHERMAL AND VERY CLOSE TO 0C. BANDING COULD SUPPORT SOME DYNAMIC COOLING. POTENTIAL IMPACTS... SNOWFALL... WITH THE SLIGHT W ADJUSTMENT IN TEMP PROFILES /READ AS WARMER TO THE SE/ SUGGEST BEST OVERLAPPING OF THERMAL SUPPORT AND DYNAMICS TO REMAIN NEAR TO SLIGHTLY W OF THE I-95 CORRIDOR WITH THIS UPDATE...SOME SLIGHT ENHANCEMENT DUE TO OROGRAPHIC IS POSSIBLE ACROSS W RI AND OUTSIDE OF I-495. IN THIS REGION...WILL CONTINUE TO SUGGEST AT LEAST LOW END WINTER STORM TOTALS WITH A RAPID DECLINE TO THE N AND E SUCH THAT PORTIONS OF NW MAY REMAIN AT OR BELOW ADVISORY LEVEL. CURRENT CIPS ANALOGS ARE BASED OFF OF A SLIGHTLY COLDER SOLUTION WITH BETTER COLD BLOCKING HIGH TO THE N...SKEWING THE SNOW IMPACT GRAPHICS A BIT. FEEL THAT RATIOS WILL BE A LITTLE BIT LOWER...WITH THE NUMBER 1 ANALOG SUPPORTING A BETTER SOLUTION WITH PEAK SNOWS FROM THE I-84 CORRIDOR TO NEAR BOS. STAY TUNED FOR MORE UPDATES AS THE WEEK PROGRESSES AS THE SNOW AXIS IS LIKELY TO CONTINUE TO SHIFT SOMEWHAT. WINDS... WITH THE STORM RAPIDLY INTENSIFYING TO NEAR 970 HPA AS IT MOVES NE OF THE BENCHMARK SAT NIGHT...SUSPECT WE WILL SEE STRONG TO POTENTIALLY EVEN DAMAGING WINDS IN SOME LOCATIONS. H92 WINDS ARE NEAR 40 KT E OF 495 AND CLOSER TO 50+ KT NEAR ACK. COMBINE THIS WITH WHAT COULD BE A FAIRLY HEAVY SNOW /LOW RATIOS GIVEN THE WARMER PROFILE/ IN SPOTS...AND COULD SEE LOCALIZED POWER OUTAGES DUE TO DOWNED LIMBS/SMALL TREES. COASTAL FLOOD THREAT: THANKFULLY...THE HIGHEST ASTRO TIDES WILL HAVE ALREADY OCCURRED ON THU AND FRI...WITH BOS PROJECTED TO REACH 11 FT AT PEAK TIDE AROUND 230 AM ON SUN MORNING NEAR WHERE THE LOW IS CLOSEST. WILL REITERATE THE PREVIOUS FORECASTER/S SENTIMENTS IN THAT SUBTLE TRACK/TIMING CHANGES ARE KEY HERE...BUT GIVEN THE SOMEWHAT HIGHER TIDE AND DEEPENING LOW PRES...SOME MINOR OR EVEN A FEW POCKETS OF MODERATE COASTAL FLOODING CAN/T BE RULED OUT MAINLY FOR THIS HIGH TIDE CYCLE. REST OF SUN INTO MON... COLDER HIGH PRES WILL BE MOVING IN FROM THE N BEHIND THE EXITING LOW PRES. EXPECT GRADUAL CLEARING THROUGH SUN WITH COLDER BLUSTERY CONDITIONS INTO SUN NIGHT. DRY WX PREVAILS MOST OF MON. MON EVENING INTO TUE... LOW CONFIDENCE HERE GIVEN THE MODELS SUGGESTION OF LACK OF BLOCKING WITH PROGRESSIVE FLOW IN THE NRN ATLANTIC. LATEST TREND HAS BEEN TO STRENGTHEN THE HIGH PRES ACROSS NRN NEW ENGLAND SOMEWHAT...SHUNTING LOW PRES TOO FAR OFFSHORE FOR IMPACTS TO SRN NEW ENGLAND. EVEN NEWEST OPERATIONAL ECMWF IS SUGGESTING THIS NOW. DUE NOTE A SIGNAL FOR INVERTED TROF HOWEVER...SO COULD STILL SEE SOME PRECIP ACROSS THE FAR SE EXTREMITIES /CAPE ISLANDS/. STILL SOME TIME ON THIS FEATURE YET. WED... LOW CONFIDENCE FORECAST AT THIS POINT. ISSUE REGARDING THE PROGRESSIVENESS OF SYSTEMS AT THAT POINT. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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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 THURSDAY NIGHT/... BEFORE 00Z...MODERATE CONFIDENCE. VFR OUR WEST WITH MVFR EAST OF THE WORCESTER HILLS. BEST CHANCE FOR ANY LOW END MVFR OR IFR VSBYS IN HEAVIER SNOW AT ACK/HYA/FMH/UUU. THE SNOW THREAT CONTINUES THROUGH THE MORNING. TODAY...HIGH CONFIDENCE. MVFR TRENDING TO VFR IN THE MORNING. LOW PRESSURE MOVES OFF TO THE EAST WHICH WILL TURN TURN THE EAST WIND BACK TO NORTH. ANY SNOW SHOULD TAPER OFF WITH THE WIND SHIFT. WINDS ALONG THE COAST WILL GUST NEAR 25 KNOTS. TONIGHT AND TOMORROW. HIGH CONFIDENCE. VFR. KBOS TAF...HIGH CONFIDENCE IN TAF TRENDS. MODERATE CONFIDENCE ON TIMING. KBDL TAF...HIGH CONFIDENCE IN TAF. OUTLOOK /FRIDAY THROUGH MONDAY/... FRIDAY INTO EARLY SATURDAY...HIGH CONFIDENCE. IN MAINLY VFR CONDITIONS. SATURDAY AFTERNOON AND SATURDAY NIGHT...MODERATE CONFIDENCE. COASTAL STORM WILL BRING PERIOD OF RAIN AND SNOW MIXING EAST OF IJD-ORH-MHT LINE WITH SOME LIGHTER SNOW WEST THIS WILL RESULT IN MVFR- IFR CONDITIONS. A PERIOD OF STRONG WIND GUSTS OF 40 TO 50 KNOTS ARE POSSIBLE SATURDAY NIGHT FROM THE NORTH THEN NORTHWEST ALONG THE SOUTHEAST NEW ENGLAND COAST. SUNDAY AND MONDAY...MODERATE TO HIGH CONFIDENCE. MAINLY VFR CONDITIONS EXPECTED WITH WEST TO NORTHWEST WIND GUSTS OF 20 TO 30 KNOTS...MAINLY ON SUN.
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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 THURSDAY NIGHT/...HIGH CONFIDENCE. STRENGTHENING COASTAL LOW WILL BRING INCREASING NORTHEAST WIND TO THE WATERS...WITH SPEEDS AROUND 25 KNOTS OVERNIGHT. AS THE COASTAL LOW MOVES OFF ON THURSDAY THE WINDS WILL BECOME NORTH WITH SIMILAR SPEEDS IN THE MORNING BEFORE DIMINISHING IN THE AFTERNOON. SEAS LINGER AT 5-6 FEET ON THE OUTER WATERS THURSDAY NIGHT. SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR MOST OF THE WATERS FOR SEAS AND GUSTS TONIGHT AND THURSDAY. SMALL CRAFT HEADLINES REMAIN ON THE OUTER WATERS THURSDAY NIGHT DUE TO CONTINUED ROUGH SEAS. OUTLOOK /FRIDAY THROUGH MONDAY/... FRIDAY INTO EARLY SATURDAY...HIGH CONFIDENCE. NORTHWEST WIND GUSTS UP TO AROUND 20 KNOTS. 2 TO 5 FOOT SEAS EXPECTED. SATURDAY AND SATURDAY NIGHT... MODERATE CONFIDENCE. WINDS INCREASE LATE SATURDAY AND SATURDAY NIGHT AS LOW PRESSURE RAPIDLY MOVES NORTHEAST NEAR 40N/70W AND INTENSIFIES. HIGH CONFIDENCE IN AT LEAST STRONG GALE FORCE WIND GUSTS WITH A MODERATE PROBABILITY FOR A PERIOD OF STORM FORCE WIND GUSTS SAT NIGHT. WINDS WILL BE FROM THE NORTH NORTHEAST AND THEN SHIFT TO THE NORTHWEST. SEAS BUILD TO BETWEEN 10 AND 15 FEET ACROSS EASTERN OUTER-WATERS. SUNDAY AND MONDAY...MODERATE CONFIDENCE. STRONG SCA TO MARGINAL GALE FORCE NORTHWEST WIND GUSTS BEHIND DEPARTING LOW PRESSURE SYSTEM. CONDITIONS IMPROVE SOMEWHAT BY MON. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...WINTER WEATHER ADVISORY UNTIL 7 AM EST THIS MORNING FOR MAZ024. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL NOON EST TODAY FOR ANZ231>235-256. SMALL CRAFT ADVISORY FROM 4 AM EARLY THIS MORNING TO 5 AM EST FRIDAY FOR ANZ250. SMALL CRAFT ADVISORY FROM 4 AM EARLY THIS MORNING TO 1 PM EST THIS AFTERNOON FOR ANZ251. SMALL CRAFT ADVISORY UNTIL 5 AM EST FRIDAY FOR ANZ254-255.
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&& $$ SYNOPSIS...WTB/DOODY NEAR TERM...DUNTEN SHORT TERM...WTB LONG TERM...DOODY AVIATION...DOODY/DUNTEN MARINE...WTB/DOODY

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