Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 010259 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1059 PM EDT FRI OCT 31 2014 .SYNOPSIS... AN INTENSIFYING COASTAL STORM WILL MOVE UP THE COAST SATURDAY AND PASS OFFSHORE SATURDAY NIGHT AND EARLY SUNDAY POTENTIALLY BRINGING DAMAGING WINDS AND RAIN TO THE REGION. HIGH PRESSURE BUILDS OVER THE EASTERN USA EARLY NEXT WEEK. ONE OR TWO COLD FRONTS MAY CROSS SOUTHERN NEW ENGLAND WEDNESDAY THROUGH FRIDAY. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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1040 PM UPDATE... BANDS OF LIGHT RAIN AND SHOWERS CONTINUE TO FAN ACROSS CT INTO W RI AT 02Z. MAIN BAND OF RAIN REMAINS JUST OFF THE OUTER CAPE AND NANTUCKET COAST. HAVE ADJUSTED THE POP FORECAST JUST A BIT TO INDICATE A FEW MORE BREAKS THROUGH 06Z-07Z DUE TO WIDE TEMP/DEWPT SPREADS CONTINUING ACROSS THE MID AND LOWER CT VALLEY...THEN SHOULD BECOME STEADIER AS DEWPTS BEGIN TO RISE AS THE LOWER LEVELS BECOME MORE SATURATED. LOOKING AT RADAR TRENDS DOWN THE COAST...LOOKS LIKE STEADIER RAIN TRYING TO DEVELOP E OF THE MID ATLC COAST WHILE SPOTTY SHOWERS CONTINUE TO DEVELOP OFF THE NJ COAST TO LONG ISLAND. THIS APPEARS TO BE ON TRACK FROM THE PREVIOUS FORECAST...AND SHOULD CONTINUE TO SEE THIS FILL IN OVERNIGHT. HAVE ADJUSTED FORECAST TO BRING CURRENT TO CURRENT TRENDS. PREVIOUS DISCUSSION... STRONG HIGH PRESSURE IN THE GREAT LAKES WILL COMBINE WITH LOW PRESSURE MOVING NORTHEAST TOWARDS SOUTHERN NEW ENGLAND TO RESULT IN WINDS CONTINUING TO INCREASE OVERNIGHT. NORTHEASTERLY WINDS WILL PICK UP TO AROUND 15 MPH BY EARLY SATURDAY MORNING. WITH THE INCREASING ONSHORE FLOW...EXPECT TEMPS NOT TO FALL...THOUGH WILL LOWER A FEW MORE DEGREES THROUGH DAYBREAK.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY/...
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***STRONG TO DAMAGING WINDS ARE LIKELY WITH AN INTENSIFYING COASTAL STORM SATURDAY NIGHT AND SUNDAY*** 31/12Z MODELS ARE IN FAIRLY GOOD AGREEMENT ON AN INTENSIFYING LOW PRESSURE SYSTEM MOVING UP THE COAST FROM NORTH CAROLINA AND PASSING JUST OUTSIDE THE 40/70 BENCHMARK SATURDAY NIGHT. THIS IS ASSOCIATED WITH A DIGGING TROUGH MOVING EASTWARD FROM THE GREAT LAKES AND A COUPLE OF SHORTWAVES ROTATING AROUND THE EAST SIDE OF THE TROUGH. THIS COMBINED WITH A STRONG HIGH PRESSURE SYSTEM THAT WILL MOVE FROM THE NORTHERN PLAINS INTO THE GREAT LAKES REGION WILL RESULT IN A TIGHT PRESSURE GRADIENT ACROSS SOUTHERN NEW ENGLAND. WIND: THIS IS A FAIRLY HIGH CONFIDENCE FORECAST FOR WIND. THE TIGHT PRESSURE GRADIENT...ALONG WITH A NORTHEASTERLY 50 KT LOW LEVEL JET BRINGING MUCH COLDER AIR OVER THE RELATIVELY WARM OCEAN WATERS WILL RESULT IN STRONG TO DAMAGING WIND GUSTS ACROSS MUCH OF SOUTHERN NEW ENGLAND SATURDAY NIGHT INTO SUNDAY. THE COLDER AIR WILL ALLOW LAPSE RATES TO STEEPEN AND WINDS TO EASILY MIX DOWN TO THE SURFACE. THE MOST LIKELY LOCATION FOR WIND GUSTS TO REACH 58 MPH OR GREATER IS ACROSS COASTAL PLYMOUTH COUNTY...THE CAPE...AND ISLANDS WHERE WE HAVE ISSUED A HIGH WIND WARNING. EXPECT THAT MUCH OF EASTERN MASSACHUSETTS AND RHODE ISLAND WILL LIKELY HAVE WINDS GUSTING TO AT LEAST 50 MPH AND THAT WITH PARTIALLY TO FULLY LEAVED TREES... DAMAGE MAY BE DONE TO TREES AND POWER LINES. HAVE KEPT THE HIGH WIND WATCH UP FOR THESE AREAS AND ALLOW THE NEXT SHIFT TO EVALUATE ANOTHER ROUND OF MODEL DATA BEFORE DECIDING HOW TO UPGRADE. THE WIND IN THESE AREAS IS EXPECTED TO PICK UP SATURDAY EVENING AND CONTINUE THROUGH MUCH OF SUNDAY. ACROSS THE REMAINDER OF SOUTHERN NEW ENGLAND /CONNECTICUT...SOUTHERN NEW HAMPSHIRE...AND WESTERN AND CENTRAL MASSACHUSETTS/ EXPECT WIND GUSTS TO REACH UP TO 45 MPH. HOWEVER...RATHER THAN BEING ASSOCIATED WITH THE LOW LEVEL JET...THESE WINDS WILL BE MORE A RESULT OF STRONG COLD ADVECTION INTO THE REGION ON SUNDAY. WIND ADVISORIES WILL LIKELY BE NEEDED FOR THESE AREAS BUT GIVEN THAT WINDS ARE NOT EXPECTED TO INCREASE UNTIL SUNDAY...FELT WE COULD WAIT FOR ANOTHER MODEL RUN. COASTAL FLOODING: PLEASE SEE TIDES/COASTAL FLOODING SECTION BELOW FOR MORE INFORMATION. RAIN: MODERATE CONFIDENCE. EXPECTING RAINFALL AMOUNTS OF GENERALLY AN INCH OR LESS WEST OF INTERSTATE 95. AMOUNTS MAY BE A BIT HIGHER EAST OF 95 BUT SHOULD STILL REMAIN UNDER 2 INCHES. THERE IS A POSSIBILITY THAT DRIER AIR MAY WORK ITS WAY IN AT THE MID LEVELS AND CUT OFF PRECIPITATION FOR A PERIOD AND THAT WOULD UNDERCUT RAIN TOTALS A BIT. SNOW: LOW CONFIDENCE. WHILE NOT A HIGH PROBABILITY...THERE IS A POSSIBILITY THAT OUR RAIN WILL END AS A BRIEF PERIOD OF SNOW SUNDAY MORNING IN SOME AREAS. THE MOST LIKELY LOCATION FOR THIS IS ACTUALLY ALONG THE INTERSTATE 95 CORRIDOR WHERE THE COLD CONVEYOR BELT WRAPS AROUND THE LOW PRESSURE SUNDAY MORNING. THIS MAY PROVIDE ENOUGH DYNAMIC COOLING TO RESULT IN SOME WET SNOWFLAKES FALLING. IF IT WERE ABLE TO ACCUMULATE AT ALL...IT WOULD BE A COATING TO LESS THAN AN INCH. THERE IS ALSO A POSSIBILITY THAT SOME SNOW MAY FALL IN THE HIGHER TERRAIN OF THE MONADNOCKS AND WORCESTER HILLS. THIS IS ALSO A LOW PROBABILITY BUT IF IT OCCURS COULD RESULT IN ONE TO MAYBE TWO INCHES OF ACCUMULATION. AGAIN THIS WOULD ONLY BE AT THE HIGHER ELEVATIONS.
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&& .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... BIG PICTURE... THE LONG TERM PERIOD STARTS WITH A CLOSED LOW OVER THE NORTHEAST USA A TROUGH OVER THE ROCKIES...AND A RIDGE IN BETWEEN. THE CLOSED LOW LIFTS NORTHEAST INTO THE MARITIMES EARLY IN THE WEEK. THE RIDGE AND TROUGH TO OUR WEST MOVE EAST...BUT THE OVERALL FLOW BECOMES MORE ZONAL WITH TIME WITH A DETACHED SOUTHERN STREAM WAVE NEAR THE MEXICAN BORDER. HEIGHTS START THE PERIOD BELOW NORMAL DUE TO THE CLOSED LOW...THEN CLIMB TO NORMAL OR A LITTLE ABOVE NORMAL IN THE ZONAL FLOW. DEPENDING ON TIMING...COULD BE COOLING BACK TO BELOW NORMAL LATE IN WEEK. THIS SUGGESTS A COLD START TO THE WEEK BUT QUICKLY TRENDING BACK TO NORMAL MID WEEK...THEN COOLING AT END OF WEEK. ONCE THE UPPER FLOW BECOMES ZONAL...CONFIDENCE IN THE TIMING OF INDIVIDUAL WAVES IN THE FLOW AND THEIR ASSOCIATED SURFACE SYSTEMS WILL BE REDUCED. THE DAILIES... SUNDAY NIGHT-MONDAY-TUESDAY... THE AXIS OF THE UPPER LOW AND COLD POOL START SUNDAY NIGHT OVERHEAD AND MOVE OFF THROUGH THE MARITIMES BY MONDAY. DRIER AIR MOVES IN AT ALL LEVELS SUNDAY NIGHT AND REMAINS OVERHEAD MONDAY. FAIR MIXING SHOULD REACH TO AROUND 900 MB. TEMPS OF ZERO TO -1C AT THAT LEVEL TRANSLATE TO MAX SFC TEMPS IN THE UPPER 40S AND AROUND 50. THE HIGH MOVES OFF TO THE EAST TUESDAY WITH MILDER AIR MOVING IN ESPECIALLY ALOFT. CROSS SECTIONS SHOW INCREASING MOISTURE AT MID AND HIGH LEVELS...SO EXPECT SOME MID AND HIGH CLOUDS TOGETHER WITH THE SUN. TEMPS WARM UP A LITTLE BUT MIXING WILL BE SHALLOWER...950 MB TEMPS SUPPORT MAX TEMPS MID 50S. WEDNESDAY THROUGH FRIDAY... TWO SHORTWAVES MOVE ACROSS THE NORTHEAST AND EASTERN CANADA DURING MID TO LATE WEEK. THE FIRST WAVE LIFTS THROUGH QUEBEC WITH LIMITED CURVATURE IN NEW ENGLAND. THE SECOND WAVE DIGS DEEPER OVER THE GREAT LAKES AND SWEEPS ACROSS NEW ENGLAND 24-36 HOURS LATER THAN THE FIRST. AS THE UPPER FLOW IS ROUGHLY ZONAL...EXACT TIMING OF THE TWO PASSAGES IS LOW CONFIDENCE AT THIS TIME. WITH THE FIRST WAVE DIRECTED THROUGH CANADA AND THE UPPER FLOW REMAINING SOUTHWEST...THERE IS A GOOD CHANCE THE SURFACE FRONT STALLS OVER OR NEAR SOUTHERN NEW ENGLAND. THE SECOND DEEPER WAVE TURNS THE UPPER FLOW NORTHWEST AND SHOULD PUSH A COLD FRONT WELL OFFSHORE WITH COLDER AIR THEN FLOWING IN. WE WILL GO WITH CHANCE POPS NORTH OF THE PIKE LATE WEDNESDAY/NIGHT WITH THE FIRST WAVE AND FRONT...THEN MORE WIDESPREAD CHANCE POPS THURSDAY WITH THE SECOND WAVE AND FRONT. TIMING ON THIS WILL LIKELY CHANGE SOMEWHAT WITH SUCCESSIVE MODEL RUNS. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SUNDAY/... TONIGHT...HIGH CONFIDENCE IN EVENTS...MODERATE CONFIDENCE IN TIMING. VFR TO START...BUT CONDITIONS DETERIORATE THROUGH THE NIGHT TO MVFR-IFR FROM SOUTH TO NORTH WITH LOWEST CONDITIONS ALONG THE COAST. EXPECT SCATTERED SHOWERS SOUTH OF THE MASS PIKE WITH THE GREATEST CHANCE OF STEADIER RAINFALL ALONG THE SOUTH COAST. SATURDAY THROUGH SUNDAY...MODERATE TO HIGH CONFIDENCE. MVFR/IFR CONDITIONS CONTINUE THROUGH 12Z SUNDAY WHEN CEILINGS START TO RISE FROM WEST TO EAST AS LOW PRESSURE PULLS AWAY FROM SOUTHERN NEW ENGLAND. NORTHEASTERLY WINDS INCREASE THROUGH THE PERIOD...PEAKING IN THE 40 TO 50 KT RANGE SATURDAY NIGHT INTO SUNDAY MORNING FOR THE EASTERN TERMINALS. WINDSPEEDS WILL BE LOWER ACROSS THE WESTERN TERMINALS BUT STILL GUSTING UP TO 35 TO 45 KTS PEAKING MORE ON SUNDAY. WIDESPREAD RAIN EXPECTED THROUGH SUNDAY MORNING MOST LOCATIONS AND CONTINUING ON THE EAST COAST...CAPE...AND ISLANDS INTO SUNDAY AFTERNOON. KBOS...HIGH CONFIDENCE IN TAF TRENDS. LOWER CONFIDENCE ON EXACT TIMING OF ONSET OF RAIN AND HIGHER WINDS. KBDL...HIGH CONFIDENCE IN TAF TRENDS. LOWER CONFIDENCE ON EXACT TIMING OF ONSET OF RAIN AND HIGHER WINDS. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...MODERATE CONFIDENCE SUNDAY NIGHT THROUGH TUESDAY...VFR. NORTHWEST WINDS MONDAY WILL GUST 25 TO 30 KNOTS DURING THE DAY. WEDNESDAY...VFR. POSSIBLE BRIEF MVFR CIGS/VSBYS IN SHOWERS LATE IN THE DAY AND AT NIGHT. && .MARINE...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. ***DANGEROUS COASTAL STORM FOR MARINERS EXPECTED THIS WEEKEND*** HIGH CONFIDENCE THROUGH SUNDAY. NORTHEASTERLY WINDS WILL INCREASE...REACHING 25 KTS AFTER MIDNIGHT. THE WIND WILL CONTINUE TO STEADILY INCREASE THROUGH SATURDAY AND SATURDAY NIGHT AS AN INTENSIFYING LOW PRESSURE PASSES SE OF NANTUCKET. WINDS ARE EXPECTED TO INCREASE TO STORM FORCE... PARTICULARLY ON THE WATERS EAST OF MASSACHUSETTS. HAVE UPGRADED THE STORM WATCH TO A STORM WARNING ON THOSE WATERS. LESS CONFIDENT ON THE POTENTIAL FOR STORM FORCE WINDS SOUTH OF NEW ENGLAND. THEREFORE HAVE KEPT THE STORM WATCH WITH THE PEAK OF THE WINDS EXPECTED SATURDAY NIGHT INTO SUNDAY. THIS WILL LIKELY NEED TO BE UPGRADED TO EITHER A STORM WARNING OR POSSIBLY HIGH END GALES DEPENDING ON THE TRACK OF THE LOW. WITH NORTHEASTERLY WINDS GUSTING TO 50 KTS...SEAS WILL INCREASE SUBSTANTIALLY REACHING 15 TO 20 FEET EASILY ON THE EASTERN COASTAL WATERS. THERE IS A POSSIBILITY THAT THEY INCREASE TO AS MUCH AS 25 FEET EAST OF CAPE COD. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...MODERATE CONFIDENCE. SUNDAY NIGHT AND MONDAY...GUSTY NORTHWEST WINDS AT GALE FORCE EARLY SUNDAY NIGHT. WINDS THEN DIMINISH BUT REMAIN 25 TO 30 KNOTS THROUGH MONDAY. SEAS DIMINISH SUNDAY NIGHT BUT LINGER 5 TO 10 FEET THROUGH MONDAY. TUESDAY...WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT LEVELS. WEDNESDAY...SEAS WILL REMAIN BELOW 5 FEET. SOUTHWEST WINDS WILL INCREASE WITH FREQUENT GUSTS 20 TO 25 KNOTS.
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&& .TIDES/COASTAL FLOODING... A COASTAL FLOOD WATCH CONTINUES FOR THE SATURDAY EVENING AND EARLY SUNDAY MORNING HIGH TIDE CYCLES FOR THE EASTERN MA COAST...INCLUDING THE NORTH FACING PORTION OF CAPE COD AND NANTUCKET. THIS IS FOR THE POTENTIAL OF MINOR TO ISOLATED POCKETS OF MODERATE COASTAL FLOODING POSSIBLE ALONG WITH BEACH EROSION. ASTRONOMICAL HIGH TIDES ARE RATHER LOW SATURDAY EVENING AND AGAIN EARLY SUNDAY MORNING. HOWEVER...STRONG NORTH TO NORTHEAST WIND GUSTS UP TO 50 KNOTS MAY RESULT IN SEAS BUILDING TO AROUND 20 FEET OVER THE OPEN WATERS. STILL SOME UNCERTAINTY AS TO HOW STRONG THE WINDS WILL GET...BUT THE POTENTIAL IS THERE FOR A 2 TO 2.5 STORM SURGE ALONG WITH SIGNIFICANT WAVE ACTION. BASED ON THE LATEST DATA...WE ARE MOST CONCERNED ABOUT THE SATURDAY EVENING HIGH TIDE CYCLE. THE WINDS APPEAR STRONGEST AT THAT TIME WITH A LITTLE MORE OF AN EASTERLY COMPONENT TO THE WIND. THE HIGHEST RISK AREAS APPEAR TO BE HULL AND SCITUATE. WE ALSO HAVE TO BE CONCERNED WITH THE TYPICAL HOT SPOTS...SUCH AS SALISBURY AND PLUM ISLAND WHICH ARE VERY SUSCEPTIBLE TO BEACH EROSION. FINALLY... WILL ALSO HAVE TO KEEP AN EYE ON NANTUCKET HARBOR...AS STRONG NORTHERLY WINDS CAN CAUSE ISSUES FOR THEM. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...HIGH WIND WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY MORNING FOR MAZ005>007-013>018-020. HIGH WIND WARNING FROM 5 PM EDT SATURDAY TO 4 PM EST SUNDAY FOR MAZ019-021>024. COASTAL FLOOD WATCH FROM SATURDAY EVENING THROUGH SUNDAY MORNING FOR MAZ007-015-016-019-022-024. NH...NONE. RI...HIGH WIND WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY MORNING FOR RIZ001>008. MARINE...STORM WATCH FROM 6 AM EDT SATURDAY THROUGH SUNDAY AFTERNOON FOR ANZ232>237-255-256. STORM WARNING FROM 6 PM EDT SATURDAY TO 5 PM EST SUNDAY FOR ANZ230-231-250-251-254. && $$ SYNOPSIS...WTB/RLG NEAR TERM...WTB/RLG/EVT SHORT TERM...RLG LONG TERM...WTB AVIATION...WTB/RLG MARINE...WTB/RLG/EVT TIDES/COASTAL FLOODING...STAFF

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