Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 290806 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 406 AM EDT MON SEP 29 2014 .SYNOPSIS...
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SUMMERLIKE WARMTH WILL COME TO AN END THIS AFTERNOON AS A FRONT MOVES SOUTH ACROSS THE REGION...DROPPING TEMPERATURES...BRING CLOUDS AND PATCHY DRIZZLE TO THE AREA TONIGHT. A COOLER NORTHEAST WIND WILL CONTINUE THROUGH THE REMAINDER OF THE WEEK AND ONE OR TWO WEAK LOW PRESSURE CENTERS MAY YIELD A CHANCE OF SHOWERS FOR THE REGION. A FRONT AND POSSIBLY SECONDARY LOW PRESSURE AREA WILL LIKELY AFFECT SOUTHERN NEW ENGLAND FRIDAY NIGHT AND SATURDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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PREDAWN HOURS... PATCHY FOG ACROSS THE INTERIOR CT VALLEY THIS MORNING AND THE I-495 CORRIDOR OF EASTERN MA. THIS FOG WILL BURN OFF A FEW HOURS AFTER SUNRISE. ELSEWHERE QUIET AND MILD WEATHER PREVAILS AS DEW PTS IN THE U50S AND L60S ALONG WITH HIGH CLOUDS AND LIGHT WSW WIND PRECLUDE COOLER TEMPS. AFTER SUNRISE... 1032 MB ANTICYCLONE OVER ONTARIO AND QUEBEC EARLY THIS MORNING BUILDS SOUTHEAST INTO ATLANTIC CANADA LATER TODAY. THIS SENDS A BACKDOOR COLD FRONT AND A MUCH COOLER AIRMASS ACROSS THE AREA THIS AFTERNOON OVER NORTHEAST MA AND SOUTHEAST NH...THEN ACROSS THE REMAINDER OF THE AREA THIS EVENING. BEFORE THE FRONTAL PASSAGE IT WILL ONCE AGAIN BE A WARM DAY GIVEN THE MILD START THIS MORNING. HOWEVER NOT QUITE AS WARM AS PREVIOUS DAYS WITH HIGHS TODAY 75 TO 80 BEFORE TEMPS DROP THIS AFTERNOON THRU THE 70S AND INTO THE 60S. THIS WILL BE A TYPICAL BACKDOOR FRONT WITH WINDS SHIFTING TO THE ENE AND GUSTING UP TO 25 MPH OR SO. NOT QUITE AS STRONG AS A SPRING BACKDOOR FRONT AS WATER TEMPS IN THE GULF OF MAINE REMAIN IN THE L60S...COMPARED TO WATER TEMPS IN THE 40S AND 50S DURING THE SPRING. COULD BE A BRIEF PERIOD OF PATCHY DRIZZLE IMMEDIATELY BEHIND THE FRONT GIVEN LOW LEVEL MOISTURE PROFILES.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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TONIGHT... POST FRONTAL AIRMASS OVERSPREADS THE ENTIRE REGION ALONG WITH ONSHORE FLOW STRENGTHENING. THIS RESULTS IN INCREASING LOW LEVEL MOISTURE IN THE FORM OF LOW CLOUDS AND AREAS OF DRIZZLE POSSIBLE. COOLER WITH LOWS DIPPING INTO THE 50S. TUESDAY... LEAD SHORT WAVE TROUGH MOVES ACROSS THE REGION. WEAK MID LEVEL CYCLONIC FLOW COUPLED WITH MOIST ONSHORE FLOW SHOULD YIELD THE RISK OF A FEW LOW TOP SHOWERS AND/OR AREAS OF DRIZZLE...WITH HIGHEST RISK ACROSS RI AND EASTERN MA. CLOUDS AND ONSHORE FLOW WILL RESULT IN A MUCH COOLER AFTERNOON WITH HIGHS ONLY IN THE 60S. COULD TURN OUT TO BE COOLER AS 2 METER TEMPS FROM NAM/GFS AND SREF ALL INDICATE MAX TEMPS ONLY IN THE U50S OVER NORTHEAST MA AND SOUTHWEST NH.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... HEADLINES... * BELOW AVERAGE CONFIDENCE IN THE FORECAST FOR THIS TIME PERIOD WITH A RISK OF SHOWERS TUESDAY...WEDNESDAY AND THE FIRST PART OF THE WEEKEND OVERVIEW... CONFIDENCE FOR MOST OF THIS FORECAST PERIOD IS BELOW AVERAGE. GENERAL AGREEMENT IN THE MEDIUM RANGE MODELS AND ENSEMBLES OF A WEAK TROF AND AREA OF HIGH MOISTURE THREATENING SOUTHERN NEW ENGLAND HEADING INTO TUESDAY BUT MODELS VARY CONSIDERABLY IN LOCATION AND STRENGTH. SIMILARLY...MEDIUM RANGE MODELS DEPICT CLOSED LOW MOVING ACROSS SOUTHERN NEW ENGLAND DURING MID WEEK BUT LOW CONFIDENCE ON DETAILS AND CHANCES OF MEASURABLE RAIN. A RELATIVELY HIGH AMPLITUDE NEGATIVELY TILT TROF IS ALSO SHOWN BY MEDIUM RANGE MODELS TO CROSS NEW ENGLAND NEXT WEEKEND WITH POSSIBLY A TRIPLE POINT LOW. THERE IS CONSIDERABLE VARIATION AND ENOUGH RUN TO RUN INCONSISTENCY TO HAVE LOW CONFIDENCE ON THE AMOUNT AND DISTRIBUTION OF RAFL WITH THIS SYSTEM. DETAILS... TUESDAY...THE 12Z GFS RUN DEPICTS A FAIR AMOUNT OF RAFL ALONG THE S COAST TUESDAY IN ASSOCIATION WITH A WEAK LEAD SHORT WAVE TROF AHEAD OF THE MORE PRONOUNCED CLOSED LOW...BUT THIS FEATURE IS NOT REFLECTED NEARLY SO MUCH IN THE NAM AND ENSEMBLES. THE 12Z ECMWF DOES PICK UP ON THIS FEATURE BUT NOT TO NEARLY THE DEGREE OF THE GFS. WILL INDICATE CHANCE POPS SOUTHERN ZONES AND SLIGHT CHANCE MOST OTHER ZONES WITH RELATIVELY LOW CONFIDENCE ON JUST HOW THIS FEATURE WILL MANIFAST ITSELF. WEDNESDAY...WEAK UPPER CLOSED LOW IS PROJECTED TO CROSS THE REGION DURING THE WEDNESDAY AND WEDNESDAY NIGHT TIMEFRAME BUT THE MODELS VARY IN STRENGTH AND NEARNESS OF SURFACE LOW REFLECTION WITH THE ECMWF BEING MORE ROBUST THAN THE GFS IN THIS CASE. THE GFS DOES DEPICT A FAIRLY PRONOUNCED COLD POOL ALOFT WITH TOTAL TOTALS RISING TO NEAR 48. THERE IS CORRESPONDING VARIATIONS IN THE QPF. WILLHIGH CLOUDS SHOULD HELP MINIMIZE ANY DENSE FOG PATCHES BUT TEMP/DEWPOINT SPREADS WILL LIKELY CLOSE ENOUGH FOR PATCHY 3-5 MILES IN FOG. TEMPERATURES DROPPING A LITTLE FASTER THAN FORECAST AS OF 7 PM BUT FORECAST MINIMUMS STILL LOOK GOOD. LIGHT WINDS EXPECTED OVERNIGHT. 4 PM UPDATE... NO MAJOR CHANGES TO THE FORECAST FOR THE REMAINDER OF THE AFTERNOON. BOTH PVD AND BDL HAVE BROKEN THEIR RECORDS AND LOGAN WARMED UP TO 87F. DEFINITELY A MORE SUMMER LIKE FEEL OUT THERE TODAY. PUT CHANCE POPS UP TO MASSPIKE AND SLIGHT CHANCE NORTH OF THERE BUT CONFIDENCE IS RELATIVELY LOW. THURSDAY AND FRIDAY...CHANCE RAIN THURSDAY MORNING WITH DEPARTING LOW ACROSS CAPE AND ISLANDS BUT OTHERWISE MODELS HAVE SIMILAR TIMING WITH SURFACE AND UPPER RIDGE OVERING ACROSS REGION THURSDAY AFTERNOON THROUGH FRIDAY. FRIDAY NIGHT AND SATURDAY...FAIRLY LARGE AMPLIFIED TROF THAT MAY TAKE ON A NEGATIVE TILT APPROACHES REGION PER ALL MEDIUM RANGE MODELS. THERE IS A SUGGESTION OF A TRIPLE POINT LOW MOVING ACROSS SOUTHERN NEW ENGLAND FRIDAY NIGHT OR SATURDAY MORNING. ACTUAL DURATION OF RAIN IS LIKELY TO BE LESS THAN GRID POPS MIGHT IMPLY ONCE WE ARE ABLE TO BETTER DEFINE THE TIMING. ENOUGH MODEL DIFFERENCE IN THE DETAILS TO MAKE THE QPF VERY UNCERTAIN AT THIS TIME. SUNDAY...LOOKS LIKE SYSTEM WILL BE EXISTING THE REGION WITH DRIER AND COOLER AIR MOVING INTO SOUTHERN NEW ENGLAND. ALTHOUGH IT LOOKS DRY NOW...THERE IS ENOUGH COMPLEXITY WITH THE SITUATION WITH MULTIPLE SHORT WAVE TROFS TO KEEP THE DOOR OPEN FOR SIGNIFICANT CHANGES IN THE SUNDAY FORECAST. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...HIGH CONFIDENCE ON TRENDS BUT LOWER CONFIDENCE ON EXACT TIMING. THRU 12Z... LOCALIZED IFR/LIFR IN PATCHY FOG DURING THE PREDAWN HOURS WILL BURN OFF A FEW HOURS AFTER SUNRISE. ELSEWHERE VFR WILL PREVAIL. TODAY AND TONIGHT...A BACKDOOR COLD FRONT DROPS S ACROSS REGION SHIFTING THE WINDS TO THE N/NE THIS AFTERNOON. VFR CIGS AHEAD OF FRONT BUT EXPECT CIGS TO LOWER TO MVFR BEHIND IT...CLOSER TO 00Z. POST FRONTAL MOISTURE IS SHALLOW SO EXPECT MORE DRIZZLE TONIGHT RATHER THAN SHOWERS. EASTERLY/ONSHORE FLOW WILL INCREASE TONIGHT WHICH WILL ALLOW FOR MOISTURE TO INCREASE AND DROP CIGS TO MVFR WITH ISOLATED IFR. ENE WINDS WILL ALSO GUST BETWEEN 15-25 KTS OVERNIGHT ESP ACROSS THE MERRIMACK VALLEY. TUE...NOT MUCH CHANGE WITH ONSHORE FLOW. IFR IN THE MORNING WILL TREND UP TOWARD MVFR. SPOTTY LIGHT RAIN/DRIZZLE POSSIBLE. KBOS TERMINAL...HIGH CONFIDENCE IN TAF TRENDS BUT LOWER CONFIDENCE ON EXACT TIMING. KBDL TERMINAL...HIGH CONFIDENCE IN TAF TRENDS BUT LOWER CONFIDENCE ON EXACT DETAILS. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... LOW TO MODERATE CONFIDENCE TUESDAY THROUGH WEDNESDAY AND MODERATE CONFIDENCE THURSDAY AND FRIDAY. TUESDAY THROUGH WEDNESDAY...WIDESPREAD MVFR CIGS AND AREAS OF MVFR VSBYS IN SHOWERS. AREAS OF IFR CIGS AND VSBYS POSSIBLE ACROSS EAST COASTAL SECTIONS FOR TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. THURSDAY AND FRIDAY...GENERALLY VFR CONDITIONS EXPECTED. && .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...HIGH CONFIDENCE THROUGH TUE. TODAY...BACKDOOR FRONT MOVES ACROSS THE NORTHERN MA WATERS FROM LATE MORNING INTO THE AFTERNOON HOURS. ELSEWHERE FRONT WILL WAIT UNTIL LATE IN THE DAY OR THIS EVENING. EXPECT A WIND SHIFT TO THE NE ALONG WITH A BRIEF BURST OF 20-25 KT IMMEDIATELY BEHIND THE FRONT. GREATEST RISK OF 25 KT ACROSS THE CAPE ANN WATERS. THUS SMALL CRAFT ADVISORY POSTED FOR THOSE WATERS. TONIGHT...VSBY MAY LOWER IN AREAS OF DRIZZLE IN THE POST FRONTAL AIRMASS. NE WINDS SLACKEN AS THE NIGHT PROGRESSES. LARGEST SEAS ACROSS THE CAPE ANN WATERS NORTHWARD TOWARD MAINE COASTAL WATERS. TUESDAY...MODEST ENE WINDS. VSBY MAY BE LIMITED IN AREAS OF DRIZZLE AND FOG. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... THIS WEEK MAY FEATURE A FAIRLY PERSISTENT EAST TO NORTHEAST FLOW. SMALL CRAFT ADVISORY SEAS POSSIBLE TUESDAY MORNING BEHIND BACKDOOR COLD FRONT. FOR WEDNESDAY AND WEDNESDAY NIGHT...THERE IS A FAIRLY STRONG SIGNAL FOR E TO NE WIND GUSTS ABOVE SMALL CRAFT ADVISORY THRESHOLDS AS WELL AS SEAS IN ZONES EXPOSED TO AN EASTERLY FETCH ABOVE SMALL CRAFT ADVISORY THRESHOLDS. HAVE UPPED SEAS ABOVE WAVE WATCH GUIDANCE BASED ON EXPERIENCE WITH NE FLOW AND SYNOPTIC PATTERN RECOGNITION. IF THE MEDIUM RANGES MODELS HAVE A FAIR IDEA ON THE MID WEEK SYNOPTIC PATTERN...THEN WOULD NOT BE SURPRISED TO SEE SEAS BUILD TO NEAR 10 FEET EAST OF CAPE COD AND NANTUCKET BY LATE WEDNESDAY. MAY EXPERIENCE A STORM SURGE OF 1 TO 1.5 FEET DURING MIDWEEK BUT THE ASTRONOMICAL TIDES ARE NOT ALL THAT HIGH.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 11 AM EDT TUESDAY FOR ANZ250-251.
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&& $$ SYNOPSIS...NOCERA NEAR TERM...NOCERA SHORT TERM...NOCERA LONG TERM...THOMPSON AVIATION...NOCERA/THOMPSON MARINE...NOCERA/THOMPSON

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