Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 230901 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 501 AM EDT TUE SEP 23 2014 .SYNOPSIS...
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HIGH PRESSURE WILL BRING DRY WEATHER ALONG WITH MILD DAYS AND COOL NIGHTS THROUGH WEDNESDAY. COASTAL LOW PRESSURE WELL SOUTH OF THE REGION MAY GRAZE SOUTH COASTAL AREAS WITH A LOW RISK FOR FEW SHOWERS THURSDAY AFTERNOON INTO FRIDAY MORNING. HIGH PRESSURE RETURNS FRIDAY INTO EARLY NEXT WEEK WITH DRY WEATHER AND UNSEASONABLY WARM AFTERNOONS. IT IS POSSIBLE A FEW RECORD HIGH TEMPERATURES MAY BE CHALLENGED THIS WEEKEND.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... CANCELLED THE FROST ADVISORY EARLY. LOW LEVEL DRY AIR DID NOT ARRIVE QUICKLY ENOUGH TO PERMIT WIDESPREAD AREAS OF FROST. THERE WERE A FEW SPOTS IN SOUTHERN NH AND NORTHWEST MA WHICH ARE CLOSE TO THE FROST FORMATION TEMPERATURES ALREADY THIS MORNING. SO WE CANNOT COMPLETELY RULE OUT AT LEAST SOME FROST THIS MORNING. TODAY... HIGH PRESSURE CRESTS ACROSS SOUTHERN NEW ENGLAND. THIS MEANS MOSTLY SUNNY SKIES AND A PREDOMINANTLY LIGHT WEST WIND. SOME OF THE HIGH RESOLUTION GUIDANCE IS HINTING AT A SEABREEZE DEVELOPING ALONG THE COAST THIS AFTERNOON. THE LATEST RUNS OF THE RAP...ALONG WITH BOTH CORES OF THE HI-RES NAM DO DECREASE WINDS WHERE A SEABREEZE WOULD BE POSSIBLE...BUT KEEP THE BOUNDARY JUST OFF THE EAST COAST. THE ONLY MODEL/GUIDANCE SOURCE WHICH HAS CONSISTENTLY DEVELOPED A SEABREEZE IS THE HRRR. LIKE THE PREVIOUS FORECASTER...AM WARY ABOUT THE POSSIBILITY OF A SEABREEZE DEVELOPING. WITH THE HIGH PRESSURE ARRIVING LATER IN THE DAY...AM THINKING THE OFFSHORE PRESSURE GRADIENT SHOULD REMAIN JUST STRONG ENOUGH TO HOLD IT OFFSHORE...BUT IT WILL BE SOMETHING WHICH WILL NEED TO BE WATCHED. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... TUESDAY NIGHT... HIGH PRESSURE BUILDS TO THE NORTH WITH A CONTINUATION OF CLEAR SKIES AND A LIGHT NE WIND DEVELOPING OVERNIGHT. WE USED A BLEND OF THE GUIDANCE WHICH YIELDS MIN TEMPERATURES MOSTLY IN THE 40S. WENT HIGHER ALONG THE EAST COAST OF MA AS WELL AS THE LARGER URBAN CENTERS. WEDNESDAY... LARGE HIGH PRESSURE CENTERED OVER NORTHERN NEW ENGLAND WILL RESULT IN DRY/PLEASANT WEATHER FOR LATE SEPTEMBER. GIVEN THE POSITIONING OF THIS HIGH PRESSURE...STILL EXPECTING EASTERLY WINDS AT THE SURFACE. SO LOWEST TEMPERATURES WILL BE FOUND NEAR THE EASTERN MA COAST. HIGHS SHOULD RANGE FROM MAINLY THE 60S...TO PERHAPS NEAR 70 IN THE LOWER CT RIVER VALLEY. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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HIGHLIGHTS... * LOW RISK OF A FEW SHOWERS NEAR THE SOUTH COAST THU INTO FRI MORNING * UNSEASONABLY WARM AFTERNOONS THIS WEEKEND * DRY WITH NO APPRECIABLE RAINFALL IN SIGHT OVERVIEW AND MODEL PREFERENCES... MEDIUM RANGE OPERATIONAL MODELS START OFF IN PRETTY GOOD AGREEMENT...THEN HAVING DIFFICULTIES RESOLVING LOW PRES OFF THE MID ATLC COAST AND ITS POSSIBLE SHIFT TO THE N SOMETIME DURING THE THURSDAY INTO FRIDAY TIMEFRAME. QUESTION IS WHETHER E-W ORIENTED RIDGE AXIS ACROSS CENTRAL NEW ENGLAND LIFTS FAR ENOUGH N TO ALLOW MOISTURE TO WORK INTO AT LEAST SOUTHERN PORTIONS OF THE REGION. DUE TO THE DIFFERENCES...USED A BLEND OF AVAILABLE GUIDANCE AND ENSEMBLES TO INCORPORATE WIDE RANGE OF POSSIBILITIES...THOUGH LEANED TOWARD A DRIER SOLUTION. BEYOND THIS...MODEL TRENDS CONTINUE TO SHOW HIGH AMPLITUDE H5 RIDGE CENTERED ACROSS THE CENTRAL U.S. WITH MAIN STORM TRACK ACROSS HUDSON BAY THROUGH MOST OF THE WEEK. NOTING A H5 SHORT WAVE IN THIS FLOW DURING NEXT WEEKEND...WITH RIDGING POSSIBLY RETROGRADING TO THE PLAINS STATES WHILE THE SHORT WAVE WORKS INTO THE GULF OF ST. LAWRENCE AND SOUTHERN TIP OF GREENLAND. HAVE NOTED THAT THE CPC NAO GUIDANCE CURRENTLY HAS POSITIVE NAO THAT STARTS TO TREND MORE NEGATIVE TOWARD THE END OF THE MONTH...AROUND THE TIMEFRAME OF THIS SHORT WAVE. H5 HEIGHTS MAY LOWER NEXT WEEKEND...WITH A POSSIBLE COLD FRONT TRYING TO SHIFT S OUT OF QUEBEC. TOWARD THE END OF THE FORECAST...CONTINUED TO USE A BLEND OF AVAILABLE GUIDANCE INTO THE WEEKEND...THEN TRENDED TOWARD THE ENSEMBLE MEANS. DETAILS... WEDNESDAY NIGHT... E-W RIDGE AXIS REMAINS CLOSE TO THE MA/NH/VT BORDER DURING THE NIGHT WITH GENERAL E-SE WIND FLOW IN PLACE. QUESTION AT THIS POINT WILL WHETHER MOISTURE STARTS TO WORK N FROM LOW PRES NEAR THE DELMARVA PENINSULA. MODELS HAVING A VERY DIFFICULT TIME HANDLING THIS FEATURE...THOUGH 00Z GFS/GGEM ARE MORE AGGRESSIVE IN BREAKING DOWN THE RIDGE AND PUSHING PRECIP IN...WHILE 00Z ECMWF HOLDS PRECIP TO THE S. LEANED MORE TOWARD THE DRIER SOLUTION AND HOLDING THE RIDGE IN. DO INCREASE THE CLOUDS DURING THE NIGHT THOUGH. EXPECT OVERNIGHT LOWS MAINLY IN THE 40S...THOUGH HOLDING IN THE LOWER-MID 50S ALONG THE IMMEDIATE COAST. THURSDAY THROUGH FRIDAY... CONTINUE TO KEEP A WEARY EYE ON THE PERSISTENT LOW PRES NEAR THE DELMARVA PENINSULA DURING THIS TIMEFRAME. GFS/GGEM REMAIN AGGRESSIVE IN BRINGING GOOD SLUG OF PRECIP ACROSS THE REGION DURING THIS TIMEFRAME. WITH THIS RUN...THE EC IS ALSO BRINGING SOME PRECIP IN ACROSS SOUTHERN AREAS...BUT KEEPING HEAVIEST QPF TO THE S. ALL MODELS KEEP THE LOW RATHER WEAK AND NEAR OR S OF 40N LATITUDE. AGREE WITH PREVIOUS FORECAST...WITH A RATHER WEAK UPPER FLOW IN PLACE WILL BE TOUGH TO BRING APPRECIABLE PRECIP INTO THE REGION. ANOTHER ASPECT TO CONSIDER WILL BE THE POSSIBILITY OF INCREASING E TO NE WINDS WITH BROAD INVERTED TROUGH THAT MAY DEVELOP AS THE LOW PASSES. FOR NOW...KEPT STRONGEST WINDS MAINLY OVER THE COASTAL WATERS...BUT COULD ALSO SHIFT N WITH THE PRECIP. DID BRING SLIGHT CHANCE POPS INTO N CT/RI/SE MA FOR NOW...BUT AGAIN WILL NEED TO MONITOR THE PROGRESS OF THIS SYSTEM. WITH THE COOL ONSHORE FLOW...EXPECT HIGHS ONLY IN THE 60S TO AROUND 70 ON THURSDAY...THOUGH COULD WARM TO THE LOWER-MID 70S AWAY FROM THE COAST ON FRIDAY DEPENDING UPON WHEN THE LOW PASSES AND WINDS BACK TO A LIGHT NORTHERLY DIRECTION. LOWS THU NIGHT WILL RANGE FROM THE MID 40S WELL INLAND TO THE MID-UPPER 50S ALONG THE SHORE. FRIDAY NIGHT THROUGH MONDAY... HIGH AMPLITUDE H5 RIDGE REMAINS ACROSS THE EASTERN AND CENTRAL U.S. THROUGH MOST OF THIS PERIOD. EXPECT DRY CONDITIONS WITH MILD TEMPERATURES ESPECIALLY DURING THE WEEKEND. MAY SEE RECORD HIGHS ON SATURDAY AND/OR SUNDAY. MODELS TRY TO LOWER H5 HEIGHTS ACROSS CENTRAL AND SOUTHERN QUEBEC INTO THE REGION DURING MONDAY ALONG WITH A COLD FRONT...BUT TIMING IS IN QUESTION. DID HOLD TEMPS BACK A BIT FOR NOW...MAINLY IN THE 70S. ONLY QUESTION WILL BE ON MONDAY...AS MODELS TRY TO PUSH A COLD FRONT OUT OF QUEBEC TOWARD THE REGION. TIMING IS IN QUESTION THOUGH. RECORD HIGH TEMPS THIS WEEKEND INTO NEXT MONDAY... SAT 9/27... SUN 9/28... MON 9/29... BOS...86...1998 BOS...90...1881 BOS...88...1952 BDL...88...1998 BDL...83...1959 BDL...86...1945 PVD...86...1998 PVD...84...1943 PVD...87...1945 ORH...85...1933 ORH...84...1916 ORH...84...1952
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&& .AVIATION /09Z TUESDAY THROUGH SATURDAY/...
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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 WEDNESDAY/... HIGH CONFIDENCE VFR. LOW PROBABILITY OF A SEABREEZE THIS AFTERNOON. KBOS TERMINAL...HIGH CONFIDENCE. LOW PROBABILITY OF A SEABREEZE THIS AFTERNOON. KBDL TERMINAL...HIGH CONFIDENCE. OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY... HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THE PERIOD. MAY SEE TYPICAL BRIEF LATE NIGHT/EARLY MORNING PATCHY GROUND FOG IN THE TYPICALLY PRONE LOCALES. THERE IS A LOW RISK FOR A BRIEF PERIOD OF MVFR CONDITIONS NEAR THE SOUTH COAST...CAPE AND ISLANDS LATE WED NIGHT INTO FRIDAY MORNING. THIS WILL DEPEND UPON WHETHER A FEW SHOWERS CAN MAKE IT INTO THAT PORTION OF THE REGION WITH OFFSHORE LOW PRESSURE.
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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 TUESDAY NIGHT/...HIGH CONFIDENCE. WINDS AND SEAS CONTINUE TO DIMINISH ACROSS ALL COASTAL WATERS TODAY AS HIGH PRESSURE MOVES IN. MADE SOME TWEAKS TO TIMING OF SMALL CRAFT ADVISORIES THIS MORNING BASED ON OBSERVED TRENDS. RATHER TRANQUIL BOATING CONDITIONS EXPECTED THROUGH WEDNESDAY. SEAS MAY BUILD ABOVE 5 FEET ACROSS THE SOUTHERN OUTER COASTAL WATERS LATE WEDNESDAY...BUT THE TIMING IS NOT CERTAIN. OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY... WEDNESDAY NIGHT...HIGH CONFIDENCE. WINDS AND SEAS BELOW SMALL CRAFT...THOUGH MAY BEGIN TO BUILD LATE WED NIGHT ON SOUTHERN OUTER WATERS. THURSDAY THROUGH FRIDAY...MODERATE CONFIDENCE. LOW PRES WILL PASS S OF THE 40N/70W BENCHMARK LATE THU NIGHT OR FRI MORNING. LOOKS LIKE E TO NE WINDS WILL GUST UP TO 25 KT MAINLY ON THE OUTER WATERS FROM E OF CAPE COD TO THE SOUTHERN WATERS. SWELLS MAY BUILD UP TO 6-8 FT. THIS IS DEPENDENT UPON HOW FAR N THE LOW WILL PUSH BEFORE MOVING OFFSHORE. FRIDAY NIGHT-SATURDAY...HIGH CONFIDENCE. WINDS BACK TO N AND DIMINISH. LEFTOVER SEAS OF AROUND 5 FT FRI NIGHT SHOULD SUBSIDE.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EDT THIS MORNING FOR ANZ250. SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR ANZ254>256. && $$ SYNOPSIS...BELK/EVT NEAR TERM...BELK SHORT TERM...BELK LONG TERM...EVT AVIATION...BELK/EVT MARINE...BELK/EVT

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