Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 181122 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 722 AM EDT THU SEP 18 2014 .SYNOPSIS... A WEAK COLD FRONT WILL CROSS THE AREA TODAY...BUT MOISTURE IS LIMITED SO IT WILL COME THROUGH DRY. COLD HIGH PRESSURE BUILDS INTO NEW ENGLAND TONIGHT AND FRIDAY...POSSIBLY BRINGING A TOUCH OF FROST TO THE INTERIOR. THE HIGH WILL MOVE OFFSHORE THROUGH THE WEEKEND RESULTING IN A WARMUP. A COLD FRONT MOVES THROUGH ON MONDAY...FOLLOWED BY COOLER WEATHER TUESDAY AND WEDNESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
7 AM UPDATE... ONLY MINOR ADJUSTMENTS TO THE FORECAST THIS MORNING. NORMALLY COOLER AREAS HAVE DIPPED INTO THE LOW 40S AND EVEN UPPER 30S IN A FEW SPOTS UNDER GOOD RADIATIONAL COOLING CONDITIONS. IN THE MEANTIME CLOUDS FROM AN APPROACHING COLD FRONT NW AND CI TO THE SE CONTINUE TO ENCROACH. CURRENT FORECAST PARAMETERS REFLECT THIS. PREVIOUS DISCUSSION... SKIES REMAIN CLEAR ACROSS REGION EARLY THIS MORNING AND WILL REMAIN THAT WAY THROUGH SUNRISE. EXPECT PATCHY FOG IN LOW LYING AREAS DUE TO GOOD RADIATIONAL COOLING CONDITIONS. LOWS WILL BOTTOM OUT IN 40S AND 50S. WEAK COLD FRONT REMAINS DRAPED ACROSS ST LAWRENCE VALLEY AND WILL HEAD SE...CROSSING SOUTHERN NEW ENGLAND THIS MORNING. CROSS SECTIONS SHOW MOISTURE IS LIMITED WITH FRONT...SO ONLY EXPECTING A PERIOD OF CLOUDINESS AS IT MOVES THROUGH ESPECIALLY DUE TO PASSAGE OF UPPER TROUGH. COULD BE BRIEF SPRINKLE BUT RADAR TRENDS SUGGEST KEEPING FORECAST DRY. HIGHS WILL TOP OUT IN 60S AND LOWER 70S...WHICH IS BLEND OF MOS GUIDANCE. NAM MOS SEEMS A BIT TOO WARM WITH HIGHS REACHING MID 70S NEAR S COAST CONSIDERING EXPECTED CLOUD COVER.
-- End Changed Discussion --
&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... CLEARING WILL TAKE PLACE THIS EVENING FROM N TO S AS CANADIAN HIGH PRESSURE BUILDS ACROSS NEW ENGLAND AND SUBSIDENCE INCREASES BEHIND DEPARTING UPPER TROUGH. THIS WILL SET STAGE FOR A COLD NIGHT AS LOWS DROP BACK INTO 30S AND 40S...WITH TOUCH OF FROST POSSIBLE ACROSS PARTS OF NW MA AND SW NH. PER COLLABORATION WITH NEIGHBORING OFFICES THERE ARE A FEW CONCERNS WHICH MAY LIMIT WIDESPREAD FROST...INCLUDING HOW FAST CLEARING OCCURS AND DO WINDS DROP OFF ENOUGH TO ALLOW FROST FORMATION. GIVEN THESE CONCERNS WE WILL HOLD OFF ON ISSUING ADVISORIES AND ALLOW DAY SHIFT TO GET A BETTER LOOK. HIGH PRESSURE REMAINS IN CONTROL FRI. ONSHORE FLOW COMBINED WITH COOLER AIRMASS IN PLACE SHOULD KEEP AFTERNOON HIGHS IN 50S ALONG IMMEDIATE COAST AND HIGHER TERRAIN TO MID 60S ELSEWHERE. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... OVERVIEW AND MODEL PREFERENCES... LONG RANGE IS LIKELY TO BE DEFINED BY UPPER LVL LONGWAVE TROF AND ASSOCIATED CUTOFF LOW PRES EXTENDING OUT OVER HUDSON BAY AND BAFFIN ISLAND. INITIALLY...THIS TROF IS SHUNTED TO THE N OF NEW ENGLAND...AS MID LVL RIDGE MOVES TO THE E...YIELDING ZONAL FLOW. THIS IS THE WEEKEND TIMEFRAME...AND THE RISING HEIGHTS AND MODEST SW LOW LVL FLOW WILL LEAD TO MODERATE WARMING THROUGH SAT AND SUN. HOWEVER...STRONG COLD SHORTWAVE ASSOCIATED WITH CP AIRMASS NEAR ALASKA...WILL ONCE AGAIN DIG AND DEEPEN THE TROF ACROSS THE E EARLY MID NEXT WEEK...LEADING TO ANOTHER ROUND OF COOLER TEMPS ACROSS THE REGION. FOR THE MOST PART...THESE SYNOPTIC SCALE FEATURES ARE REASONABLY WELL AGREED UPON...AND THE 18.00Z GFS IS NOW MORE IN LINE WITH ECMWF TIMING OF THE COLD FRONT ASSOCIATED WITH THE EARLY WEEK WAVE. THEREFORE...FEEL A BLEND OF DETERMINISTIC GUIDANCE IS A GOOD STARTING POINT. DETAILS... FRI NIGHT THROUGH SUN... HIGH PRES WILL HOLD FAST ACROSS THE REGION...YIELDING AN INVERTED RIDGE AS THE CENTER SHIFTS OFFSHORE THANKS TO CONFLUENT ZONAL FLOW ALOFT. FRI NIGHT...WEAK PRES GRADIENT AND NEAR SKC SKIES MAY LEAD TO ENOUGH RADIATIONAL COOLING IN NW MA AND SW NH VALLEYS FOR FROST DEVELOPMENT. SOMETHING TO WATCH OVER THE NEXT 24-36 HOURS. FOR THE REST OF THE WEEKEND...MODEST RETURN FLOW AND WARM ADVECTION LEAD TO INCREASING H85 TEMPS FROM +11C SAT TO +14C SUN. THEREFORE...HIGHS RANGE IN THE LOW-MID 70S SAT...THEN MID 70S TO AROUND 80 ON SUN. PWAT VALUES LOOK TOO LOW AT THIS POINT TO SUPPORT THE LIGHT QPF GFS CONTINUES TO SHOW EACH AFTERNOON...AND WITH SUBSIDENCE IN PLACE BENEATH THE INVERTED RIDGE...WILL OPT TO MAINTAIN A DRY FORECAST THROUGH MOST OF THE DAY SUN. SUN NIGHT INTO MON... COLD FRONT IS EXPECTED TO CROSS THE REGION AS LOW PRES MOVES THROUGH SRN ON AND QC. MODEST PWAT VALUES AROUND 1.5 IN...RIGHT EQUATORWARD REGION OF UPPER LVL JET STREAK AND MODEST LOW LVL F-GEN ALL SUPPORT THE POSSIBILITY OF SHOWERS ACROSS THE REGION AS THIS FRONT MOVES THROUGH. MODELS STARTING TO LINE UP ON TIMING...MOVING IT THROUGH GENERALLY DURING THE AM HOURS MON. THIS TIMING WILL LIMIT CONVECTIVE POTENTIAL AND SOUNDINGS LOOK RELATIVELY STABLE...EVEN K VALUES REMAIN MOSTLY BELOW 30. THEREFORE...SUSPECT MAINLY JUST WIDESPREAD -SHRA ACTIVITY TO MOVE THROUGH DURING THE MORNING HOURS WITH GRADUAL IMPROVEMENT LATE DAY MON. THIS TIMING WILL ALSO KEEP COASTAL LOW PRES OFFSHORE...SO QPF VALUES SHOULD GENERALLY REMAIN BELOW A HALF INCH GIVEN CURRENT THINKING. TUE INTO THU... THIS COLD FRONT WILL ALLOW MODERATELY COOL AIRMASS TO BEGIN TO BUILD IN EARLY NEXT WEEK. IN FACT...GUIDANCE SUGGESTS THAT BY TUE...546DM THICKNESS VALUES MAY APPROACH THE NW CORNER OF THE FORECAST AREA ALONG WITH H85 TEMPS AROUND +2C. THEREFORE...UNDER THE COOL NW FLOW AND COLD ADVECTION...HIGHS TUE MAY STRUGGLE TO BREAK OUT OF THE 60S...WITH SOME 50S POSSIBLE. GRADUAL MODERATION IS EXPECTED INTO WED AND THU...BUT WITH TEMPS STILL LEANING SLIGHTLY BELOW NORMAL. THE HIGH MAY NOT CREST ACROSS THE REGION UNTIL WED...ONLY MOVING SLIGHTLY E BY THU...SO SUSPECT MAINLY DRY CONDITIONS PREVAIL. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH FRIDAY/...HIGH CONFIDENCE. ONLY MINOR ADJUSMENTS WITH THE 12Z UPDATE. MAINLY VFR TODAY WITH SCT-BKN040-060 DEVELOPING AROUND MIDDAY. WEAK COLD FRONT BRINGS WIND SHIFT TO N/NE ACROSS MOST OF AREA BY LATE MORNING OR EARLY AFTERNOON. POSSIBILITY OF BRIEF SPRINKLE BUT PROBABLY NOT MUCH MORE THAN THAT AND NOT ENOUGH TO WET RUNWAYS. CLEARING SKIES TONIGHT. POSSIBILITY OF PATCHY FROST ACROSS VALLEYS OF NW MA AND SW NH. VFR FRI WITH E/NE FLOW. KBOS TERMINAL...HIGH CONFIDENCE IN TAF...INCLUDING TIMING OF WIND SHIFT TODAY. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...SATURDAY THROUGH MONDAY... SATURDAY AND SUNDAY...HIGH CONFIDENCE. MAINLY VFR THROUGH THE PERIOD ALTHOUGH SOME GROUND FOG IS POSSIBLE SAT MORNING AND SUN MORNING AT TYPICALLY PRONE AIRPORTS. WINDS MAINLY S-SW...WITH GUSTS AROUND 20 KT POSSIBLE SUN. SUN NIGHT INTO MON...MODERATE CONFIDENCE. COLD FRONT CROSSES THE REGION DURING THE MORNING HOURS MON. SHOWERS AND POSSIBLY MVFR/IFR CONDITIONS MAY MOVE THROUGH WITH THIS FRONT. OTHERWISE...IMPROVING BACK TO VFR BY LATE DAY MON.
-- End Changed Discussion --
&& .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH FRIDAY/...HIGH CONFIDENCE. WEAK COLD FRONT CROSSES WATERS LATER THIS MORNING WITH WIND SHIFT TO N/NE. SWELL FROM OFFSHORE HURRICANE EDOUARD SHOULD BRING 3-4 FT SEAS TO OUTER WATERS BUT CONDITIONS EXPECTED TO REMAIN BELOW SCA. SHOULD SEE BRIEF SURGE IN N/NE WINDS TONIGHT AS COOLER AIR ARRIVES... MAINLY FROM MERRIMACK RIVER TO CAPE COD/ISLANDS WHERE 25KT GUSTS LIKELY AS SEEN ON FORECAST SOUNDINGS. SCA BEING POSTED FOR ALL WATERS EXCEPT BOSTON HARBOR... NARRAGANSETT BAY AND BLOCK ISLAND SOUND. WINDS AND SEAS DIMINISH FRI AS HIGH PRESSURE BECOMES CENTERED OVER GULF OF MAINE...BUT WILL MAINTAIN SCA FOR OUTER WATERS WHERE SEAS WILL TAKE TIME TO DROP BELOW 5 FT. OUTLOOK...SATURDAY THROUGH MONDAY...MODERATE CONFIDENCE. SATURDAY-SUNDAY...WINDS SWING AROUND TO SOUTHWEST WITH DAYTIME GUSTS AROUND 20 KNOTS...POSSIBLY NEAR 25 KNOTS SUNDAY. SEAS WILL REMAIN 2-4 FEET. A COLD FRONT APPROACHES LATE SUNDAY WITH A CHANCE OF SHOWERS SUNDAY NIGHT. MONDAY... A COLD FRONT CROSSES THE WATERS EARLY IN THE DAY. WEST WINDS BEHIND THE FRONT WILL REMAIN LESS THAN 20 KNOTS. SEAS WILL BUILD TO 5-7 FEET ON THE OUTER AND EXPOSED WATERS...AS A SOUTH SWELL INCREASES TO 3-5 FEET. SMALL CRAFT ADVISORIES MAY BE NEEDED. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EDT FRIDAY FOR ANZ231>235-251-256. SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM EDT FRIDAY FOR ANZ250-254-255. && $$ SYNOPSIS...DOODY/JWD NEAR TERM...DOODY/JWD SHORT TERM...JWD LONG TERM...WTB AVIATION...DOODY/JWD MARINE...DOODY/JWD

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.