Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 310840 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 440 AM EDT FRI OCT 31 2014 .SYNOPSIS...
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DRY AND SEASONABLE CONDITIONS WILL CONTINUE TODAY AS HIGH PRESSURE MOVES ACROSS NORTHERN NEW ENGLAND. A DEVELOPING COASTAL STORM WILL MOVE UP THE COAST SATURDAY AND PASS OFFSHORE SATURDAY NIGHT AND EARLY SUNDAY. HIGH PRESSURE BUILDS OVER THE EASTERN U.S. FOR EARLY NEXT WEEK. ONE OR TWO COLD FRONTS MAY CROSS SOUTHERN NEW ENGLAND WEDNESDAY AND THURSDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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AREA OF LOW TO MID LEVEL CLOUDS REMAIN ACROSS CENTRAL AND EASTERN AREAS AT 07Z...THOUGH NOTING SOME CLEARING ACROSS THE CT VALLEY AS WELL AS ALONG THE S COAST ON LATEST IR SATELLITE LOOP. NAM AND GFS BUFKIT SOUNDINGS INDICATING THAT THE 5-6KFT CEILINGS MAY BREAK UP BRIEFLY AROUND MID TO LATE MORNING BEFORE REDEVELOPING AS NE WINDS BRING IN INCREASING LOW LEVEL MOISTURE DURING THE AFTERNOON... AGAIN ACROSS CENTRAL AND EASTERN AREAS. LOW PRES MOVES SE OUT OF THE GREAT LAKES...THEN SECONDARY DEVELOPMENT BEGINS OFF THE MID ATLC COAST. LOOKS LIKE MOST OF THE DEEP MOISTURE WITH THE CYCLOGENESIS WILL REMAIN S OF THE REGION SO HAVE KEPT A DRY FORECAST GOING. MAY SEE SOME SPRINKLES AND PATCHY DRIZZLE DEVELOP LATE IN THE DAY ALONG THE E COAST...BUT NOT ENOUGH TO MENTION AT THIS POINT. EXPECT TEMPS TO ONLY RISE TO THE UPPER 40S ACROSS THE HIGHER INLAND TERRAIN...THEN MAINLY IN THE 50S ELSEWHERE WITH THE FRESHENING E-NE WINDS ESPECIALLY DURING THE AFTERNOON.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
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TONIGHT...SHORT RANGE MODELS APPEAR TO BE IN BETTER AGREEMENT IN THE DEVELOPMENT OF NOT ONE BUT TWO CENTERS OF LOW PRES AS H5 LONG WAVE TROUGH DIGS ACROSS THE SE U.S. NOTING TWO STRONG UPPER LEVEL JETS MOVING AROUND THE BASE OF THIS DIGGING TROUGH...THE FIRST 90-100 KT H3 JET AXIS WORKS NE OVERNIGHT. THIS WILL HELP INTENSIFY THE FIRST LOW OFF THE MID ATLC COAST AROUND 12Z SAT. AREA OF RAIN WILL WORK STEADILY NORTHWARD...ESPECIALLY AROUND OR AFTER MIDNIGHT. WILL ALSO SEE NE WINDS INCREASE ALONG THE COAST WITH GUSTS UP TO 25-30 KT...HIGHEST ALONG THE S COAST...CAPE COD AND THE ISLANDS. BEST SHOT FOR PRECIP WILL BE ACROSS RI/E MA. EXPECT OVERNIGHT LOWS TO RANGE FROM THE UPPER 30S OVER SW NH TO BETWEEN 45 AND 50 ALONG THE COAST.
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&& .LONG TERM /SATURDAY THROUGH THURSDAY/...
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BIG PICTURE... DEEP AMPLITUDE TROUGHS ON BOTH COASTS SATURDAY WITH A RIDGE IN BETWEEN. SHORTWAVE MOVING THROUGH THE EASTERN TROUGH GENERATES A CUTOFF UPPER LOW WITH TWO JET STREAMS...A NORTHERN STREAM ALONG THE CANADIAN BORDER AND A SOUTHERN STREAM MOVING WITH THE SHORT WAVE. THE PATTERN SHIFTS EAST DURING THE WEEK WITH THE RIDGE BUILDING OVER NEW ENGLAND. THE PATTERN THEN TRANSFORMS TO A MORE ZONAL FLOW. REMAINS OF THE PACIFIC COAST TROUGH MOVE ACROSS NEW ENGLAND MIDWEEK. COLDER THAN NORMAL HEIGHTS WITH THE EASTERN TROUGH THIS WEEKEND. HEIGHTS INCREASE TO NORMAL OR A LITTLE ABOVE NORMAL BY MIDWEEK. THIS POINTS TO A COLDER THAN NORMAL WEEKEND...TRENDING TO NORMAL TEMPERATURES BY MIDWEEK. 31/00Z GUIDANCE SUITE REMAINS IN DECENT OVERALL AGREEMENT. THERE ALSO REMAIN SOME DIFFERENCES WITH TRACK...INTENSITY AND TIMING. AT THIS POINT IT APPEARS SNOWFALL IS MOSTLY OFF THE TABLE AWAY FROM A VERY BRIEF PERIOD LATE SATURDAY NIGHT ACROSS THE HIGHER TERRAIN. EVEN THEN...IT WILL NOT AMOUNT TO MUCH. FAVORED A BLEND TO SMOOTH OVER SOME OF THE MORE MINOR DIFFERENCES. THIS RESULTED IN VERY GOOD CONTINUITY WITH THE PREVIOUS FORECAST. THE DAILIES... SATURDAY-SUNDAY... COASTAL STORM CONTINUES TO BE INDICATED FOR SATURDAY AND EARLY SUNDAY. SUPPORT COMES FROM TWO SETS OF FORCING MECHANISMS... SUGGESTING A TWO-PART EVENT. INITIAL FORCING COMES FROM RIGHT ENTRANCE REGION OF NORTHERN STREAM JET SATURDAY MORNING. THIS WILL SEND A COASTAL WAVE OF LOW PRESSURE PAST SOUTHERN NEW ENGLAND DURING THE DAY SATURDAY. THE SECOND FORCING COMES FROM LEFT EXIT REGION OF JET SUPPORTING A POTENT SHORTWAVE ROUNDING THE BASE OF THE EASTERN TROUGH LATE SATURDAY/SATURDAY NIGHT. EVEN SO...MOST OF THE FRONTOGENETIC FORCING WITH EACH SEGMENT IS FOCUSED OFFSHORE INTO THE MARITIMES AND MAINE. THE WESTERN EDGE OF THIS FORCING SHOULD EXTEND INTO SOUTHERN NEW ENGLAND WITH THE FIRST...AND POSSIBLY THE SECOND...OF THE SEGMENTS. WE EXPECT RAIN SATURDAY AND SATURDAY NIGHT WITH HIGHEST POPS OVER CAPE COD AND THE ISLANDS...LESSER VALUES NORTH AND WEST. STRONG PRESSURE GRADIENT AT THE SURFACE AND A 50 KNOT LOW LEVEL JET WILL CONTRIBUTE TO WINDY CONDITIONS. THE STRONGEST WINDS WILL BE OVER THE EASTERN/SOUTHEAST WATERS. STRONGEST LAND WINDS WILL BE OVER THE OUTER CAPE AND ISLANDS...DIMINISHING FARTHER WEST. HAVE FEATURED 45 KNOTS FOR THE STRONGEST WINDS AND 20-25 KNOTS IN THE INTERIOR. A COASTAL STORM WILL PASS US IN PIECES SATURDAY AND LATER SATURDAY NIGHT...AS NOTED ABOVE. EXPECT PRECIPITATION TO DIMINISH WEST TO EAST AFTER MIDNIGHT AND END ON THE MA EAST COAST AFTER SUNRISE SUNDAY MORNING. TEMPERATURES THROUGH MOST OF THIS STORM SHOULD REMAIN FAVORABLE FOR ALL RAIN. AS THE WINDS SHIFT FROM NORTHEAST TO NORTHWEST SATURDAY NIGHT...COLDER AIR WILL BE DRAWN IN WHICH COULD CHANGE THE LAST SHOWERS OVER TO SNOW ACROSS THE HIGHER TERRAIN. ANY ACCUMULATIONS SHOULD NOT BE MUCH MORE THAN A TRACE...WHERE IT SNOWS AT ALL. DRIER AIR SUNDAY WILL BRING CLEARING SKIES. COLD ADVECTION WILL PROMOTE MIXING THROUGH AT LEAST 850 MB. WINDS IN THIS LAYER WILL BE 35 TO 40 KNOTS...SO EXPECT NORTHWEST GUSTS TO AT LEAST THE LOWER END OF THIS RANGE. WINDS DIMINISH SUNDAY NIGHT AS THE STORM MOVES FARTHER AWAY. MONDAY-TUESDAY... HIGH PRESSURE BUILDS OVER THE REGION. MONDAY SHOULD BE SUNNY AS THIS HIGH MOVES OVERHEAD. MIXING WILL AGAIN BRING INCREASED WIND GUSTS DURING THE AFTERNOON. WINDS IN THE MIXED LAYER ARE EXPECTED AROUND 30 KNOTS WITH POTENTIAL FOR A LITTLE STRONGER SPEEDS. WINDS WILL DIMINISH WITH SUNSET. THIS HIGH PRESSURE MOVES OFFSHORE TUESDAY. THIS WILL MAKE ROOM FOR A WARM FRONT TO SWING PAST. SUFFICIENT LIFT AND MOISTURE TO SUPPORT MID AND HIGH CLOUDS...BUT THE BEST WARM FRONTAL LIFT WILL REMAIN TO OUR NORTH AND WEST SO EXPECT AT LEAST SOME SUN THROUGH THE DAY. WEDNESDAY-THURSDAY... LOW CONFIDENCE ON MIDWEEK WEATHER. AT LEAST ONE TROUGH IN THE ZONAL FLOW WILL SWING ACROSS THE REGION DURING THIS TIME. GFS AND ECMWF ARE HINTING AT ONE ON WEDNESDAY...BUT SHOWING A MORE SUBSTANTIAL TROUGH PASSING ON THURSDAY. THE FORECAST WILL HAVE CLOUDS AND LOW-END CHANCE OR SLIGHT CHANCE POPS.
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&& .AVIATION /08Z 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 TONIGHT/... THROUGH 12Z...MAINLY VFR. LOCAL MVFR-IFR VSBYS IN PATCHY FOG IN NORMALLY PRONE AREAS. TODAY...HIGH CONFIDENCE. VFR. ANY LEFTOVER MVFR VSBYS IN PATCHY FOG WILL IMPROVE BY 14Z. TONIGHT...MODERATE CONFIDENCE. CONDITIONS DETERIORATE THROUGH THE NIGHT TO MVFR-IFR FROM SOUTH TO NORTH WITH LOWEST CONDITIONS ALONG THE COAST. EXPECT LIGHT RAIN ALONG THE S COAST AND INTO SE MA AROUND OR AFTER MIDNIGHT...MOVING INTO THE REMAINDER MOST OF THE REGION TOWARD DAYBREAK. KBOS...HIGH CONFIDENCE IN TAF. KBDL...HIGH CONFIDENCE IN TAF. OUTLOOK...SATURDAY THROUGH TUESDAY...MODERATE CONFIDENCE. SATURDAY-SUNDAY...IFR CIGS AND MVFR OR IFR VSBYS IN PERIODS OF RAIN SATURDAY AND SATURDAY NIGHT. VFR AND DRIER WEATHER MOVE IN FROM WEST TO EAST EARLY SUNDAY. NORTHEAST WINDS SATURDAY GUSTING 35-45 KNOTS ON THE CAPE AND ISLANDS AND 25-35 KNOTS ACROSS THE COASTAL PLAIN. WINDS SHIFT TO NORTH SATURDAY NIGHT AND NORTHWEST SUNDAY. GUSTS 40- 45 KNOTS ON THE CAPE AND ISLANDS...WITH 25-35 KNOTS ELSEWHERE ACROSS SOUTHERN NEW ENGLAND. MONDAY...VFR. DAYTIME WIND GUSTS WILL INCREASE TO NEAR 30 KNOTS INLAND AND 35 KNOTS CAPE AND ISLANDS...DIMINISHING TOWARD EVENING. TUESDAY...VFR WITH INCREASING HIGH CLOUDS.
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&& .MARINE...
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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 TONIGHT/...HIGH CONFIDENCE. TODAY...WINDS AND SEAS REMAIN BELOW SMALL CRAFT CRITERIA. WINDS WILL VEER TO E-NE DURING THE DAY AND BEGIN TO PICK UP. GUSTS UP TO 20 KT REACH THE SOUTHERN OUTER WATERS BY LATE IN THE DAY. SEAS REMAIN BELOW 5 FT. TONIGHT...E-NE WINDS INCREASE WITH GUSTS UP TO 25-30 KT. SMALL CRAFTS REMAIN IN EFFECT FOR MOST OF THE WATERS...BUT NOT QUITE THERE FOR BOSTON HARBOR AND MASS/IPSWICH BAYS. SEAS WILL ALSO BUILD ESPECIALLY ON THE SOUTHERN OPEN WATERS DURING THE NIGHT. OUTLOOK...SATURDAY THROUGH TUESDAY...MODERATE CONFIDENCE. SATURDAY...STRONG POTENTIAL FOR HIGH END GALES...WITH LOW POTENTIAL FOR STORM FORCE WINDS. ON THE OUTER WATERS...EXPECT GUSTS TO AT LEAST 45 KNOTS. EXPECT RAIN WITH INCREASING NORTHEAST WINDS. GALE FORCE GUSTS EXPECTED ON MOST OF THE WATERS. RIGHT ON THE EDGE OF GALE FORCE WINDS IN BOSTON HARBOR AND NARRAGANSETT BAY. GALE WATCHES POSTED FOR ALL WATERS. KEPT IT SIMPLE FOR NOW...BUT WILL DEFINITELY NEED TO REFINE THE TIMING FOR THE NEAR SHORE WATERS WITH LATER FORECASTS. SUNDAY...RAIN MOVES OFF TO THE EAST. WINDS SHIFT NORTHWEST WITH GALE FORCE GUSTS UP TO 45 KNOTS. EXPECTING THESE WINDS TO DIMINISH BELOW GALE FORCE SUNDAY NIGHT. WITH THE WIND SHIFT...ROUGH SEAS WILL TRANSITION FARTHER OFFSHORE WITH DIMINISHING SEAS CLOSER TO SHORE. GALE WARNINGS WILL LIKELY LINGER INTO THE EVENING HOURS. MONDAY...GUSTY NORTHWEST WINDS WITH WIND GUSTS APPROACHING GALE FORCE AGAIN DURING THE DAY. WINDS DIMINISH TOWARD EVENING. SEAS WILL LINGER AT 5-9 FEET...ESPECIALLY ON THE OUTER WATERS. SMALL CRAFT ADVISORY IS LIKELY...LOW END CHANCE THAT GALES MAY BE NEEDED ON SOME OF THE WATERS. TUESDAY...WINDS AND SEAS SHOULD REMAIN BELOW SMALL CRAFT ADVISORY LEVELS.
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&& .TIDES/COASTAL FLOODING...
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ASTRONOMICAL HIGH TIDES ARE RATHER LOW SATURDAY EVENING AND AGAIN EARLY SUNDAY MORNING. HOWEVER...STRONG NORTHERLY WINDS AND HIGH SEAS WILL HAVE THE POTENTIAL TO RESULT IN MINOR COASTAL FLOODING AND BEACH EROSION ALONG THE EASTERN MA COAST...PARTICULARLY THE NORTH SIDE OF CAPE COD AND NANTUCKET HARBOR DURING BOTH HIGH TIDE CYCLES. THE MAIN UNCERTAINTY REVOLVES AROUND WHEN AND HOW STRONG THE WINDS/SEAS WILL GET. THE MODELS SEEM TO BE SHOWING TWO PULSES OF WIND WITH TWO WAVES OF LOW PRESSURE. THE FIRST ONE APPEARS TO BE SATURDAY EVENING WITH THE SECOND ONE SUNDAY MORNING. THE POTENTIAL CONTINUES FOR WIND GUSTS UP TO 50 KNOTS AND SEAS BUILDING TO 20 FEET ACROSS THE OPEN WATERS EAST OF MASSACHUSETTS. THE TREND OF THE 12Z GUIDANCE HAS BEEN TO SHOW THE STRONGEST WINDS/HIGHEST SEAS WITH THE SATURDAY EVENING PULSE. WILL HAVE TO WAIT AND SEE HOW THE MODELS TREND...BUT STILL FEEL BOTH HIGH TIDE CYCLES ARE AT RISK WITH A 1 TO 2 FOOT STORM SURGE. AREAS OF GREATEST CONCERN APPEAR TO BE THE NORTH SIDE OF CAPE COD...SUCH AS SANDWICH...BARNSTABLE...DENNIS...BREWSTER AND POSSIBLY EASTHAM. OTHER TYPICAL HOT SPOTS WILL BE SALISBURY AND PLUM ISLAND...HULL...SCITUATE AND PERHAPS SANDWICH HARBOR AND NANTUCKET HARBOR. AGAIN...THE MAIN CONCERNS WILL BE MINOR COASTAL FLOODING AS WELL AS BEACH EROSION.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...GALE WATCH FROM SATURDAY MORNING THROUGH LATE SUNDAY NIGHT FOR ANZ230>237-250-251-254>256. SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EDT SATURDAY FOR ANZ231>234-250. SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 6 AM EDT SATURDAY FOR ANZ235-237-254>256.
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&& $$ SYNOPSIS...WTB/EVT NEAR TERM...EVT SHORT TERM...EVT LONG TERM...WTB AVIATION...WTB/EVT MARINE...WTB/EVT TIDES/COASTAL FLOODING...BELK

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