Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 171822 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 222 PM EDT THU APR 17 2014 .SYNOPSIS...
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UNSEASONABLY COOL WEATHER WILL PREVAIL THROUGH FRIDAY AS HIGH PRESSURE BUILDS OVER THE REGION. LOW CLOUDS AND PATCHY DRIZZLE WILL AFFECT COASTAL AREAS DUE TO THE ONSHORE FLOW. TEMPERATURES WILL MODERATE THIS WEEKEND. SLOW MOVING LOW PRESSURE COULD BRING SHOWERS FROM LATE MONDAY NIGHT INTO WEDNESDAY OF NEXT WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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220 PM UPDATE... BACK EDGE TO LOWER CLOUD DECK AFFECTING SE MA IS MAKING WESTWARD PROGRESS AS SEEN ON SATELLITE...SO IT DOES LOOK LIKE THESE AREAS WILL SEE CLEARING LATER THIS AFTERNOON AND EVENING. MODEL CROSS SECTIONS SHOW A RATHER DEEP LAYER OF LOW LEVEL MOISTURE RETURNING TO COASTAL AREAS LATER TONIGHT...SO WE CONTINUED THEME OF LOW CLOUDS AND PATCHY DRIZZLE OVERNIGHT. FARTHER INLAND...SOME OF THIS MOISTURE SHOULD ALSO BE PREVALENT FOR A TIME OVERNIGHT. EXPECT TO SEE PATCHY LOW CLOUDS CENTERED AROUND DAYBREAK SAT... BUT LOW LEVELS SHOULD BE DRY ENOUGH TO PREVENT ANY FOG/DRIZZLE. TEMPERATURES WILL DROP OFF QUICKLY EARLY TONIGHT...ESPECIALLY ACROSS INTERIOR...BEFORE CLOUDS ARRIVE LATE. LOWS ARE A BLEND OF GFS/NAM MOS WHICH YIELDS 20S TO LOWER 30S.
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&& .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
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HIGH PRESSURE BUILDS OVER SOUTHERN NEW ENGLAND FRI. LOW LEVEL MOISTURE SHOULD BE EASILY TRAPPED BENEATH SUBSIDENCE INVERSION... ESPECIALLY NEAR COAST PER MODEL CROSS SECTIONS. EXPECT EARLY MORNING CLOUDS TO SCOUR OUT ACROSS INTERIOR...BUT HOLD FIRM CLOSER TO COASTLINE WHERE MARINE LAYER SHOULD ALSO BE DEEP ENOUGH TO SUPPORT PATCHY MORNING DRIZZLE. CONTINUED E/NE WINDS WILL KEEP TEMPERATURES BELOW AVERAGE BUT A LITTLE MILDER THAN TODAY. USED BLEND OF BIAS-CORRECTED GFS/NAM MOS SINCE THEY HAVE BEEN RUNNING A LITTLE TOO COOL WHICH GIVES HIGHS IN 40S COAST TO 50S INTERIOR. COULD COME CLOSE TO 60 ACROSS CT VALLEY. FLOW TURNS MORE W/SW FRI NIGHT AS HIGH MOVES OFFSHORE. MODELS MAINTAIN LOW LEVEL MOISTURE EARLY ON NEAR COAST BUT ERODE IT OVERNIGHT AS MID/HIGH LEVEL MOISTURE STREAMS INTO REGION AHEAD OF WEAKENING COLD FRONT. EXPECT TO HAVE LOW CLOUDS/PATCHY FOG EARLY ESPECIALLY NEAR CAPE COD AND ISLANDS. THIS MAY THIN OUT AS THICKER MID/HIGH CLOUDS ARRIVE BUT CONFIDENCE IS LOW. SHOULD BE A BIT MILDER WITH LOWS MAINLY IN 30S.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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HIGHLIGHTS... * DRY AND SEASONABLE THROUGH MONDAY * SHOWERS A GOOD BET FOR TUE INTO WED IN GENERAL THERE IS VERY GOOD MODEL AGREEMENT THROUGH THE EXTENDED FORECAST PERIOD. FROM LATE IN THE WEEK THROUGH EARLY NEXT WEEK...UPPER LEVEL SPLIT FLOW EXISTS ACROSS THE EASTERN USA. SOUTHERN NEW ENGLAND IS INFLUENCED BY THE NORTHERN STREAM AND A CUTOFF LOW OVER THE SOUTHEAST STATES SNEAKING HARMLESSLY OUT TO SEA WELL TO OUR SOUTH. ON TUE...A NEW UPPER TROUGH OVER THE GREAT LAKES DEEPENS...FORMING A CUTOFF LOW OFF OF CAPE COD BY WED. DETAILS... SATURDAY... A WEAK SURFACE TROUGH WILL PASS ACROSS SOUTHERN NEW ENGLAND EARLY SAT. WHILE A SHOWER CANNOT BE RULED OUT...ITS MAIN IMPACT WILL BE TO PUT AN END TO THE ONSHORE FLOW...WITH LIGHT WEST TO NORTHWEST WINDS BECOMING ESTABLISHED AND SUNSHINE RETURNING FOR MOST OF THE DAY. THIS WILL ALLOW HIGHS TO REACH THE UPPER 50S TO NEAR 60. SUNDAY AND MONDAY... HIGH CONFIDENCE OF REMAINING DRY THROUGH SUNDAY AND MONDAY. VERY STRONG HIGH PRESSURE BECOMES CENTERED OVER NEW ENGLAND SUNDAY AND MOVES OFFSHORE MONDAY. SUNDAY WILL BE BRIGHT AND SUNNY WITH HIGHS AGAIN IN THE UPPER 50S TO LOWER 60S...COOLER NEAR THE COAST THOUGH. LIGHT SOUTHWEST FLOW AROUND THE DEPARTING HIGH ON MONDAY WILL GIVE TEMPERATURES ANOTHER BOOST. 925 MB TEMPS ARE FORECAST TO REACH +8C TO +10C BY MONDAY EVENING. HAVE INCREASED FORECAST MAX TEMPERATURES A FEW DEGREES ABOVE GUIDANCE...REACHING THE MID TO PERHAPS UPPER 60S EXCEPT 50S AT THE IMMEDIATE COAST. SUNSHINE WILL FADE BEHIND INCREASING MID AND HIGH LEVEL CLOUDINESS MONDAY AFTERNOON. HOWEVER THERE NO LONGER IS ANY RISK FOR PRECIPITATION DURING THE DAY. MONDAY NIGHT THROUGH WEDNESDAY... THIS IS AN UNSETTLED PERIOD. MODELS AGREE THAT ANOTHER UPPER LEVEL TROUGH IN THE NORTHERN STREAM MOVES FROM THE GREAT LAKES EASTWARD AND AMPLIFIES TUE...EVENTUALLY BECOMING A CUTOFF UPPER LOW SOMEWHERE OFF THE NEW ENGLAND COAST. MODEL CONSENSUS IS THAT THIS OCCURS EAST OF CAPE COD/NANTUCKET ON WED ALTHOUGH THE GFS OPERATIONAL RUN IS FARTHER NORTH OFF OF NEW HAMPSHIRE. MILD WITH SHOWERS A GOOD BET FROM LATE MON NIGHT THROUGH AT LEAST TUE NIGHT. HAVE EXTENDED THIS CHANCE OF SHOWERS THROUGH WED BASED ON THE 00Z ECMWF MODEL RUN. THERE IS A CHANCE THAT THIS COULD TURN INTO A SOAKING RAIN... ESPECIALLY TUE INTO TUE NIGHT...BUT THIS FAR OUT IN TIME OUR PROBABILITIES ONLY REFLECT 30-40 PERCENT CHANCES OF RAIN. MODEL GUIDANCE SHOWS HIGHS IN THE MID 60S TUE AND UPPER 50S TO NEAR 60 WED. HAVE GONE WITH THIS...HOWEVER THE ECMWF 850 MB TEMPS ARE ONLY +4C...WHICH IS COLDER THAN THE GFS +8C...SO IT IS POSSIBLE THE WED MAX TEMPS MAY NEED TO BE ADJUSTED DOWNWARD.
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&& .AVIATION /18Z THURSDAY THROUGH TUESDAY/... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 1730Z UPDATE... HIGH CONFIDENCE THROUGH FRI...MODERATE CONFIDENCE FRI NIGHT. MVFR CIGS PRIMARILY ACROSS SE MA THROUGH THIS EVENING WITH VFR CIGS /035/ POSSIBLE INTO PVD/BOS FOR A TIME. CONTINUED NE FLOW SHOULD BRING LOWER MVFR CIGS INTO MUCH OF REGION TONIGHT... ESPECIALLY NEAR COAST. IFR CIGS EXPECTED ACROSS CAPE COD AND ISLANDS AS WELL AS HIGHER TERRAIN INLAND OVERNIGHT. PATCHY DRIZZLE ALSO POSSIBLE BUT MAINLY NEAR COAST. CIGS SLOWLY LIFT FRI BUT COASTAL AREAS SHOULD REMAIN MVFR FOR MUCH OF DAY. LOWER CONFIDENCE FRI NIGHT AS W/SW FLOW SHOULD ERODE LOWER CLOUD COVER...BUT MVFR/IFR CIGS COULD ONCE AGAIN IMPACT COASTAL SITES. KBOS TERMINAL...HIGH CONFIDENCE. PERIOD OF MVFR CIGS /035/ SOUTH OF AIRPORT THIS AFTERNOON. KBDL TERMINAL...HIGH CONFIDENCE. OUTLOOK...SATURDAY THROUGH MONDAY... SATURDAY THROUGH MONDAY...HIGH CONFIDENCE VFR. && .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 FRIDAY NIGHT/...HIGH CONFIDENCE. NE WINDS WILL DIMINISH THROUGH THIS EVENING. SEAS WILL TAKE THEIR TIME TO SUBSIDE HOWEVER GIVEN PERSISTENT NE FLOW THROUGH FRI. EXTENDED SCA PRIMARILY FOR SEAS MAINLY ON OUTER WATERS. THIS WILL ALSO RESULT IN LOW CLOUDS/PATCHY DRIZZLE ON WATERS LATER TONIGHT INTO FRI MORNING. SHOULD SEE MORE IN WAY OF FOG DEVELOPMENT FRI NIGHT...ESPECIALLY ON S COASTAL WATERS AS FLOW BECOMES MORE W/SW BUT IS LIGHT. SEAS SHOULD REMAIN ABOVE 5 FT ON OUTER WATERS. OUTLOOK...SATURDAY THROUGH MONDAY... SATURDAY...A BRIEF PERIOD OF NW FLOW BEHIND A WEAK LOW PRES TROUGH. SEAS MAY SUBSIDE BRIEFLY TO BELOW 5 FT OVER THE OUTER WATERS. SUNDAY...HIGH PRESSURE AND A RETURN OF NORTHEAST WIND FLOW. SEAS ONCE AGAIN BUILDING TO JUST ABOVE THE 5 FT THRESHOLD. MONDAY...AS THE HIGH MOVES OFFSHORE...WINDS SHIFT TO THE SOUTHWEST AND BECOME GUSTY...ESPECIALLY OVER THE WATERS EAST OF MA. THEY COULD REACH 20 TO 25 KT AT TIMES. SEAS EXPECTED TO REMAIN ON THE ORDER OF 3 TO 5 FT.
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&& .HYDROLOGY... MINOR FLOODING CONTINUES ALONG PORTIONS OF THE MAIN STEM CT RIVER. CREST HAS REACHED NORTHAMPTON AND IS FORECAST TO REACH THOMPSONVILLE THIS AFTERNOON AND HARTFORD TONIGHT. MODERATE FLOODING IS FORECAST ON LOWER REACHES NEAR MIDDLE HADDAM. FLOOD WARNINGS REMAIN POSTED ALONG CT RIVER AT... MONTAGUE NORTHAMPTON THOMPSONVILLE HARTFORD MIDDLE HADDAM IN ADDITION...PAWCATUCK RIVER IN RI WAS NEARING CREST AT WESTERLY AND WOOD RIVER JUNCTION. IT IS FORECAST TO CREST JUST BELOW FLOOD STAGE LATER TODAY AND EARLY TONIGHT. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ231>234. SMALL CRAFT ADVISORY UNTIL 6 AM EDT FRIDAY FOR ANZ235-237-251. SMALL CRAFT ADVISORY UNTIL 6 AM EDT SATURDAY FOR ANZ250-254- 255. SMALL CRAFT ADVISORY UNTIL 2 PM EDT FRIDAY FOR ANZ256.
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&& $$ SYNOPSIS...EVT/JWD NEAR TERM...JWD SHORT TERM...JWD LONG TERM...GAF AVIATION...EVT/JWD MARINE...EVT/JWD HYDROLOGY...

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