Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 131059 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 659 AM EDT SUN APR 13 2014 .SYNOPSIS... A WARM FRONT WILL LIFT NORTH ACROSS THE REGION TODAY BRINGING EVEN MILDER TEMPERATURES INTO MONDAY. A SLOW MOVING COLD FRONT WILL BRING A SOAKING RAIN TUESDAY INTO TUESDAY NIGHT FOLLOWED BY DRY AND MUCH COOLER CONDITIONS FOR THE MIDDLE AND END OF THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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700 AM UPDATE... HAVE UPDATED THE FORECAST TO ACCOUNT FOR CURRENT TRENDS. WARM FRONT CURRENTLY STATIONED ACROSS THE MASS PIKE WILL LIFT NORTHWARD TODAY. HEAVIEST PRECIP WILL RESIDE NORTH OF THE PIKE...HOWEVER SOUTH OF THE PIKE A FEW SCT SHOWERS WILL DEVELOP. THIS IS NOTED BY THE SHOWERS IN BETHEL NY...WHICH LOOK LIKE THEY WILL HOLD INTO CT. HI-RES GUIDANCE PUSHES THE SHOWERS THROUGH THE REGION BETWEEN 12Z TO 16Z. OTHERWISE TEMPS AND WIND FORECAST IS ON TRACK FOR TODAY. PREVIOUS DISCUSSION... WARM FRONT LIFTS NORTH INTO NORTHERN NEW ENGLAND. BEST/DEEPEST MOISTURE AND LIFT WILL BE ALONG AND NORTH OF THE WARM FRONT. BUT MODELS DO SHOW SOME QPF INTO AT LEAST NORTHERN MASS. THE ECMWF ACTUALLY FORECASTS PCPN SOUTH TO THE COAST. SUFFICIENT MOISTURE AND INSTABILITY TO SUSPECT A FEW SCATTERED OR WIDELY SCATTERED SHOWERS FARTHER SOUTH. WE WILL CONTINUE TO FEATURE SLIGHT CHANCE POPS IN NORTHERN MASS AND LOW- END CHANCE POPS IN SOUTHERN NH. MIXING PROFILES SUGGEST MIXING TO 925 MB. BUT MODEL VALUES CAN UNDERESTIMATE THE DEPTH A LITTLE. ALSO...WARM ADVECTION BEHIND THE WARM FRONT COULD MAKE 18Z VALUES UNREPRESENTATIVE OF LATE AFTERNOON TEMPERATURES. TEMPS AT 18Z AT THE TOP OF THE MIXING RANGE WOULD SUPPORT MID TO UPPER 60S...BY 00Z IT WOULD BE MID 70S. WE WILL GO IN BETWEEN WITH UPPER 60S TO MID 70S...EXCEPT COOLER ALONG THE COASTLINE ESPECIALLY THE SOUTH COAST WITH MAX TEMPS IN THE 50S. WINDS IN THE MIXED LAYER ARE FORECAST AT 25 KNOTS...POSSIBLY 30 KNOTS. WILL GO WITH SOUTH GUSTS TO 25 KNOTS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... TONIGHT...WARM FRONT REMAINS WELL TO OUR NORTH WITH WARM SECTOR AIR IN PLACE OVER SOUTHERN NEW ENGLAND. DEWPOINTS IN THIS AIRMASS ARE EXPECTED TO BE IN THE MID 40S TO AROUND 50. MEANWHILE THE OCEAN TEMPS SOUTH OF THE SOUTH COAST ARE 40-44 DEGREES. THIS WILL HAVE A REFRIDGERATING EFFECT ON THE AIRMASS AS IT APPROACHES NEW ENGLAND...AND CAUSE LOW LEVEL SATURATION AND FOG/STRATUS FORMATION. THE MODELS HINT AT THIS BUT MOST BARELY SHOW A SMALL AREA OF 50 PCT SKY COVER. WE WILL MANUALLY EDIT A MUCH HIGHER SKY COVER ALIGNING WITH THE 46+ DEGREE DEWPOINTS. ALSO ADDED DRIZZLE TO THE FOG. WITH DEWPOINTS 46-50...EXPECT MIN TEMPS IN THE UPPER 40S AND LOWER 50S. MONDAY... FOG AND DRIZZLE IN THE MORNING ESPECIALLY ACROSS RI AND SOUTHEAST MASS. POSSIBLY IN THE CT VALLEY AS WELL. THE AIR ABOVE THE LOW LEVEL CLOUDS/FOG LOOKS DRY ENOUGH FOR THE FOG TO BURN OFF IN THE MORNING...LATEST AROUND THE CAPE AND ISLANDS. FULL SUN WILL AGAIN BRING MIXING...WITH POTENTIAL REACHING TO 900 MB AND POSSIBLY A LITTLE HIGHER. AFTERNOON TEMPS AT THIS LEVEL WILL BE EQUIV TO 7-10C AT 850 MB...WHICH SUGGESTS MAX TEMPS IN THE 70S. IF WE ACTUALLY MIX TO 850 MB THEN THERE IS POTENTIAL FOR 80 DEGREES WITH THE BEST CHANCE IN THE MERRIMACK VALLEY. MEANWHILE SOUTH WINDS OFF THE OCEAN WILL KEEP THE SOUTH COAST MUCH COOLER...WE WENT WITH 60S. WINDS IN THE MIXED LAYER WILL BE STRONG WITH 40-50 KNOT SOUTHWESTERS AT 2000-5000 FEET. EXPECT SOME OF THIS DRAWN TO THE SURFACE IN GUSTS. WE WILL GO WITH 30 KNOTS...BUT MINDFUL THAT STRONGER WINDS WILL BE OVERHEAD. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... HIGHLIGHTS... * STRONG COLD FRONTAL PASSAGE ON TUESDAY INTO WEDNESDAY MORNING * BELOW AVERAGE TEMPS FOR THE REMAINDER OF THE WORK WEEK * MODERATING TEMPS FRIDAY MODELS AND CONFIDENCE... OVERALL 00Z MODEL GUIDANCE IS IN GOOD AGREEMENT FOR THE DIGGING TROUGH AND POTENT COLD FRONT WHICH WILL MOVE ACROSS THE REGION TUESDAY INTO TUESDAY NIGHT. THE ONLY MAJOR OUTLIER IS THE NAM MODEL WHICH SLOWS DOWN THE PROGRESSION OF THE SYSTEM MAKING IT BECOME MORE NEGATIVELY TILT. HOWEVER BELIEVE THAT THIS FRONT WILL MOVE ACROSS AND BE OUT OF THE REGION BY WED DUE TO THE STRONG HIGH PRESSURE IN ITS WAKE. THEREFORE DID NOT USE THE NAM MODEL IN THIS FORECAST. THE NEXT FEATURE TO FOCUS ON IS ANOTHER TROUGH ALOFT PROGRESSING ACROSS THE LOWER 48 BY THE END OF THE WEEK. GUIDANCE HAS BEEN INDICATING MULTIPLE UNCERTAINTIES WITH THIS FEATURE INCLUDING DISTRIBUTION OF ENERGY WITHIN THE FLOW...THE TIMING AS WELL AS THE ENERGY BEHIND THE TROUGH. HOWEVER AS THIS SYSTEM DIGS INTO THE CONUS...STRONG RIDGING WILL BUILD EAST OF THE REGION. INCREASING CONFIDENCE IN THE FORECAST WITH HIGH CONFIDENCE THAT WET WEATHER WILL OCCUR ON TUESDAY...WITH A LOWER CONFIDENCE ON THE EXACT TIMING. THERE IS STILL SOME UNCERTAINTY ON WHERE THE HEAVIEST PRECIP WILL OCCUR. OTHERWISE MODERATE CONFIDENCE THAT HIGH PRESSURE WILL DOMINATE THE REMAINDER OF THE WEEK WITH LOW CONFIDENCE ON POTENTIAL WET WEATHER FOR NEXT WEEKEND. DETAILS... MONDAY NIGHT INTO WEDNESDAY.... GUIDANCE IS BEGINNING TO CLUSTER MORE TOGETHER ON THE TIMING AND INTENSITY OF THE APPROACHING COLD FRONTAL SYSTEM. THE LATEST 00Z MODELS INDICATE THAT SEVERAL WAVES WILL DEVELOP ALONG THE SLOW MOVING COLD FRONT ALLOWING FOR MULTIPLE CHANCES FOR HEAVY RAINFALL. AN AMPLIFYING LONGWAVE TROUGH OVER THE CENTRAL CONUS WILL SEND A COLD FRONT TOWARD NEW ENGLAND TUESDAY INTO TUESDAY NIGHT...EXITING THE REGION BY WED MORNING. A FEW SHOWERS MAY DEVELOP AHEAD OF THE FRONT MONDAY NIGHT...BUT BELIEVE THAT GUIDANCE IS PICKING UP MORE ON THE FOG AND DRIZZLE POTENTIAL DUE TO THE MARITIME AIR BEING ADVECTED ONSHORE. THE COLD FRONT SHOULD APPROACH THE REGION BY LATE TUESDAY MORNING PUSHING HEAVY PRECIP FROM WEST TO EAST THROUGHOUT THE DAY. EXPECT RAINFALL TO BE HEAVY AT TIMES AS A SOUTHERLY LLJ TRANSPORTS ATLANTIC/GULF MOISTURE WITH PW NEAR 1.5 INCHES INTO THE REGION. ANTICIPATE THAT THE EVENING COMMUTE WILL BE IMPACTED ACROSS THE REGION DUE TO THE HEAVY RAIN AND LOWER VSBYS. FINALLY THERE IS THE POSSIBILITY THAT A FEW RUMBLES OF THUNDER COULD DEVELOP ALONG THE LINE...BUT DUE TO LOW CONFIDENCE KEPT IT OUT OF THE FORECAST FOR NOW. COLDER AIR WILL FILTER IN VERY LATE TUE NIGHT INTO WED AS THE FRONT PASSES TO THE EAST...WITH ANY LINGERING SHOWERS MIXING WITH OR CHANGING BRIEFLY TO SNOW. VERY LITTLE IF ANY ACCUMULATION IS EXPECTED. WEDNESDAY AFTERNOON INTO FRIDAY... STRONG COLD FRONT WILL MOVE OFFSHORE BY WED MORNING. FOLLOWED BY STRONG SUBSTANCE AND A BUILDING HIGH PRESSURE SYSTEM. ANOTHER UPPER LEVEL DIGGING TROUGH WILL BEGIN TO DEVELOP ACROSS THE WESTERN CONUS...ALLOWING FOR A STRONG RIDGE TO DEVELOP ACROSS THE NORTH ATLANTIC. THIS RIDGE WILL PUSH THE BUILDING HIGH OVER NEWFOUNDLAND AND LABRADOR YIELDING TO EASTERLY FLOW FOR THE REGION. OVERALL ANTICIPATE DRY WEATHER WITH WELL BELOW AVG TEMPS FOR WED AND THURS. FRIDAY TEMPS WILL BE MODERATING DUE TO BUILDING THERMAL RIDGE TRYING TO PUSH INTO THE REGION. HOWEVER ALONG THE IMMEDIATE MASS COASTLINE TEMPERATURES WILL STRUGGLE ON ALL THREE DAYS TO GET ABOVE 50F DUE TO THE ONSHORE WIND. SATURDAY... GUIDANCE AS WELL AS THERE ENSEMBLES ARE INDICATING A WAVE MOVING ACROSS THE GREAT LAKES REGION LATE FRIDAY AND INTO SATURDAY RESULTING IN A SYSTEM MOVING TOWARDS NEW ENGLAND. THIS COULD RESULT IN A SOGGY AND COOLER WEEKEND. HOWEVER THIS FAR OUT...HAVE LOW CONFIDENCE. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH MONDAY/... TODAY...HIGH CONFIDENCE. MAINLY VFR. COULD BE BRIEF MVFR CIGS/VSBYS IN LIGHT SHOWERS NORTH OF MASS ROUTE 2 LATE MORNING/EARLY AFTERNOON. AREA OF LOW CLOUDS/FOG MAY APPROACH SOUTH COAST INCLUDE CAPE COD/ISLANDS AFTER 21Z. SOUTH WINDS WILL GUST TO 25 KNOTS DURING THE MIDDAY/AFTERNOON. TONIGHT...MODERATE CONFIDENCE. LOW CLOUDS/FOG/DRIZZLE WILL BRING IFR CIGS/VSBYS ACROSS RI AND SOUTHEAST MASS. SOME OF THIS COULD SNEAK UP THE COAST INTO BOSTON. ALSO A CONCERN OF IFR IN THE CT VALLEY. SOUTH COAST LOCATIONS SUCH AS NANTUCKET/HYANNIS/FALMOUTH COULD SEE VSBYS DROP TO 1/4 MILE AT TIMES OVERNIGHT. MEANWHILE...WINDS AT 2000 FEET INCREASING TO 40-45 KNOTS WILL PRODUCE LOW LEVEL WIND SHEAR. MONDAY...MODERATE CONFIDENCE. INITIAL IFR CIGS/VSBYS IN RI AND SE MASS...AND THE CT VALLEY. CONDITIONS IMPROVE TO VFR BY MIDDAY AND THROUGH THE AFTERNOON. SOUTH-SOUTHWEST WINDS WILL INCREASE WITH GUSTS TO 30 KNOTS. CONTINUED SOUTHWEST WINDS 40-50 KNOTS AT 2000 FEET ABOVE SURFACE. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY... TUESDAY-WEDNESDAY...MODERATE CONFIDENCE. EXPECT MVFR CONDITIONS TO DEVELOP FROM W-E DURING TUE MORNING IN RAIN SHOWERS. PERIODS OF HEAVY RAIN POSSIBLE TUE AFTERNOON/EVENING ACROSS CENTRAL AND WESTERN AREAS WITH AREAS OF IFR. PRECIP MAY MIX WITH LIGHT SNOW AND/OR SLEET ACROSS S NH/W MA BEFORE ENDING LATE TUE NIGHT OR WED MORNING. CONDITIONS SHOULD IMPROVE TO VFR FROM W-E DURING WED. THURSDAY...MODERATE CONFIDENCE. VFR. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SUNDAY NIGHT/...HIGH CONFIDENCE. TODAY...INCREASING WINDS AND SEAS...REACHING 25 KNOTS AND/OR 5 FEET EARLY THIS AFTERNOON. A SMALL CRAFT ADVISORY IS BEING ISSUED FOR ALL WATERS. AREAS OF FOG AND LOW VSBYS WILL DEVELOP LATE THIS AFTERNOON OVER THE SOUTHERN WATERS AS HIGHER DEWPOINT AIR MOVES NORTH OVER THE 40-44 DEGREE WATER. TONIGHT...FOG AND DRIZZLE AND LOW VISIBILITY EXPECTED. HIGHEST LIKELIHOOD WILL BE OVER THE SOUTHERN WATERS UP TO THE SHORE. VISIBILITY MAY LOWER TO 1/4 MILE OR LESS. MONDAY...AREAS OF FOG AND DRIZZLE MAY LINGER INTO MID MORNING...BUT EXPECT IMPROVING VSBYS BY MIDDAY. SOUTH TO SOUTHWEST WINDS MAY GUST 20-25 KNOTS. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY... MONDAY NIGHT...HIGH CONFIDENCE. FOG WILL DEVELOP ACROSS THE WATERS. STRONG LLJ WILL RESULT IN BUILDING SEAS AND BELIEVE THAT A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED. TUESDAY INTO THURSDAY...MODERATE CONFIDENCE. STRONG COLD FRONT WILL MOVE ACROSS THE WATERS TUESDAY INTO WEDNESDAY. EXPECTING GUSTY WINDS BEHIND THIS FRONT DUE TO STRONG COLD AIR ADVECTION. SEAS WILL BUILD IN RESPONSE AND MAY START RELAXING LATE WEDNESDAY INTO THURSDAY. THERE IS A LOW PROBABILITY OF GALES TUESDAY EVENING INTO THE OVERNIGHT HOURS. SMALL CRAFT ADVISORIES WILL LIKELY BE NEEDED. && .HYDROLOGY... NERFC FORECASTS BRING LOWER CT RIVER FROM HARTFORD THROUGH MIDDLE HADDAM INTO MINOR FLOOD STARTING LATER TODAY...BASED ON WATER BEING ROUTED DOWNSTREAM FROM THE UPPER CT BASIN. FLOOD WARNINGS CONTINUE FOR THE CT RIVER AT HARTFORD AND AT MIDDLE HADDAM. THOSE WITH INTERESTS ALONG LOWER REACHES OF CT RIVER SHOULD PAY ATTENTION TO THE LATEST FORECASTS AND CURRENT WATER LEVELS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 8 PM EDT MONDAY FOR ANZ230>237-250-251-254>256. && $$ SYNOPSIS...WTB/DUNTEN NEAR TERM...WTB/DUNTEN SHORT TERM...WTB LONG TERM...DUNTEN AVIATION...WTB/DUNTEN MARINE...WTB/DUNTEN HYDROLOGY...STAFF

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