Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 210239 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1039 PM EDT MON APR 20 2015 .SYNOPSIS... A WIND SWEPT SOAKING RAIN IS EXPECTED THROUGH THIS EVENING...WITH EVEN A FEW THUNDERSTORMS POSSIBLE TONIGHT. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ALONG WITH MILD TEMPS TUESDAY MORNING GIVES WAY TO A DRYING TREND DURING THE AFTERNOON. A COLD FRONT WILL BRING SCATTERED SHOWERS AND PERHAPS EVEN AN ISOLATED THUNDERSTORM OR TWO WEDNESDAY AFTERNOON AND EVENING. UNSEASONABLY COOL WEATHER FOLLOWS THURSDAY THROUGH THIS WEEKEND WITH JUST A SPOT SHOWER FROM TIME TO TIME. && .NEAR TERM /UNTIL MIDNIGHT TONIGHT/...
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1030 PM UPDATE... NO MAJOR CHANGES TO ONGOING FORECAST THIS EVENING. DID TWEAK THE NEXT SEVERAL HOURS TO REFLECT THE LATEST OBSERVED TRENDS. THE MAIN CONCERN OVERNIGHT REMAINS THE POTENTIAL FOR CONVECTION. LATEST RUNS OF THE HRRR REMAIN BULLISH ON PRE-DAWN THUNDERSTORM POTENTIAL ACROSS RI AND SOUTHEAST MA...INCLUDING THE CAPE AND ISLANDS. WILL NEED TO CONTINUE TO MONITOR PROGRESS OF THUNDERSTORM CLUSTER OVER PA/NY THIS EVENING...SINCE THIS IS WHERE THE ENERGY WILL COME FROM. NOT EXPECTING SEVERE WEATHER AT THIS TIME. HEAVY RAINFALL IS NOT OUT OF THE QUESTION THOUGH. DEPENDING ON WHERE THIS HAPPENS...AND HOW FAST...WE COULD SEE SOME FLOODING ISSUES LATE TONIGHT. MAINLY EXPECTING NUISANCE FLOODING...BUT COULD BE MORE IF THE HEAVY RAINFALL OCCURS WITHIN SOME URBAN AREAS...SUCH AS FALL RIVER AND NEW BEDFORD. PREVIOUS DISCUSSION... THESE HEAVIER SHOWERS WERE BLOSSOMING ON THE NOSE OF THE LOW LEVEL JET/DRY SLOT ALLOWING FOR INCREASED INSTABILITY. GIVEN SHOWALTER INDICES DROPPING BELOW ZERO AND SOME ELEVATED CAPE...A FEW EMBEDDED THUNDERSTORMS ARE POSSIBLE THIS EVENING. WE PROBABLY WILL SEE A BIT OF A LULL IN THE ACTIVITY SOMETIME LATER THIS EVENING UNTIL THE NEXT BATCH OF ACTIVITY DEVELOPING ACROSS THE EASTERN GREAT LAKES/MID ATLANTIC TRACKS NORTHEAST. WHILE SEVERE WEATHER IS NOT EXPECTED...THIS MAY POSE A HIGHER RISK OF SCATTERED THUNDERSTORMS WITH HEAVY RAINFALL TOWARD DAYBREAK. THIS IS DISCUSSED FURTHER IN THE NEXT SECTION. FINALLY...AREAS OF FOG MAY BECOME LOCALLY DENSE. BEST CHANCE FOR THIS WILL BE LATER THIS EVENING WHEN WILL LIKELY SEE A LULL IN THE ACTIVITY AND WINDS DIMINISH A BIT. CONFIDENCE AND AREAL COVERAGE NOT HIGH ENOUGH TO ISSUE A DENSE FOG ADVISORY...BUT LATER SHIFTS WILL HAVE TO MONITOR.
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&& .SHORT TERM /MIDNIGHT THROUGH 6 PM TUESDAY/... OVERNIGHT...THE WARM FRONT WILL MOVE NORTH OVER SOUTHERN NEW ENGLAND AND THE SOUTHERN PARTS OF THE AREA LOOK TO WARM SECTOR DURING THE EARLY MORNING HOURS. THIS WOULD INCLUDE RHODE ISLAND...SOUTHEASTERN MASSACHUSETTS...AND POSSIBLY PORTIONS OF NORTHERN CONNECTICUT. THIS WILL NOT ONLY BRING TEMPERATURES UP THROUGH THE NIGHT...BUT WILL ALSO ALLOW THE ATMOSPHERE TO FURTHER DESTABILIZE. K INDICES INCREASE AND SHOWALTER INDICES DECREASE AND ALONG WITH THE TOTAL TOTALS IN THE 50S THIS WILL RESULT IN SOME SURFACE BASED INSTABILITY ALONG WITH THE ELEVATED INSTABILITY ALREADY IN PLACE. THIS WILL PROVIDE A BETTER CHANCE OF THUNDER EARLY TUESDAY MORNING AS THE SHORTWAVE AND ATTENDANT COLD FRONT MOVE THROUGH THE REGION. EXPECT RAPID CLEARING BEHIND THE FRONT WITH TEMPERATURES SOARING INTO THE UPPER 60S TO NEAR 70 MOST LOCATIONS. WESTERLY WINDS WILL ALLOW EVEN THE COASTAL LOCATIONS TO GET IN ON THE WARM TEMPERATURES...UNLIKE SATURDAY. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... HIGHLIGHTS... * SCATTERED SHOWERS WED WITH A LOW RISK OF THUNDER/SMALL HAIL * SEASONABLY MILD TEMPERATURES WED * UNSEASONABLY COOL THU-SUN WITH A SPOT SHOWER OR TWO AT TIMES DETAILS... TUESDAY NIGHT... A SHORTWAVE WILL BE APPROACHING FROM THE WEST TUE NIGHT. MODELS DO NOT SHOW MUCH QPF AS INSTABILITY IS RATHER LIMITED. MAY SEE A FEW SPOT SHOWERS ESPECIALLY NORTH OF THE MA PIKE...BUT MUCH OF THE NIGHT SHOULD FEATURE DRY WEATHER IN A GIVEN LOCATION. LOW TEMPS WILL BOTTOM OUT IN THE 30S TO THE LOWER 40S. WEDNESDAY AND WEDNESDAY NIGHT... A FAIRLY STRONG SHORTWAVE AND ASSOCIATED COLD FRONT WILL CROSS THE REGION WED AFTERNOON AND EVENING. HIGH TEMPS SHOULD STILL REACH INTO INTO THE UPPER 50S TO MIDDLE 60S AHEAD OF THE FRONT. WE WILL SEE SCATTERED SHOWERS WITH THE FRONT GIVEN DECENT FORCING AND SOME MARGINAL INSTABILITY. MOST LIKELY TIME FRAME IS WED AFTERNOON AND EARLY EVENING. ITS QUITE COLD ALOFT AND MID LEVEL LAPSE RATES ARE VERY IMPRESSIVE AROUND 8C/KM! IF WE CAN MUSTER A FEW HUNDRED J/KG OF CAPE...MAY EVEN SEE AN EMBEDDED THUNDERSTORM OR TWO. CONFIDENCE ON THUNDER IS LOW AT THIS POINT...BUT GIVEN COLD POOL ALOFT THERE IS AT LEAST THIS RISK FOR SOME GRAUPEL/SMALL HAIL AND PERHAPS EVEN GUSTY WINDS IN THE HEAVIEST SHOWERS. THIS ACTIVITY SHOULD WIND DOWN BY WED EVENING. THURSDAY THROUGH MONDAY... ANOMALOUS CLOSED UPPER LEVEL LOW SETS UP ACROSS NORTHERN NEW ENGLAND AND INTO QUEBEC. THE RESULT WILL BE BELOW NORMAL HEIGHTS AND COOLER THAN NORMAL TEMPS IN SOUTHERN NEW ENGLAND. OVERALL...HIGH TEMPS WILL RANGE FROM THE UPPER 40S TO MIDDLE 50S MUCH OF THE TIME BUT SOME MODERATION IS POSSIBLE BY MONDAY. AS FOR PRECIP CHANCES...THE VAST MAJORITY OF THE TIME SHOULD FEATURE DRY WEATHER. HOWEVER...GIVEN COLD POOL ALOFT A FEW SPOT SHOWERS WILL BE POSSIBLE AT TIMES...ESPECIALLY IN NORTHERN SECTIONS DURING THE AFTERNOON HOURS. LOW RISK FOR EVEN A FEW WET SNOW FLAKES TO MIX IN FOR A TIME ACROSS THE HIGHER TERRAIN...BUT WOULD BE OF NO IMPACT. THERE IS ONE FLY IN THE OINTMENT. WE WILL HAVE TO WATCH A MORE SIGNIFICANT LOW PRESSURE SYSTEM SAT NIGHT/SUN. MOST OF THE MODEL GUIDANCE KEEPS THAT SYSTEM WELL TO OUR SOUTH. THE 12Z ECMWF IS A BIT CLOSER THEN THE REST OF THE GUIDANCE...BUT EVEN THAT WOULD KEEP US DRY. AGAIN...ODDS STRONGLY FAVOR KEEPING THIS SYSTEM SOUTH OR OUR REGION GIVEN ANOMALOUS CLOSED LOW SITTING JUST TO OUR NORTH. && .AVIATION /02Z 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 TUESDAY/... TONIGHT...IFR TO LIFR CONDITIONS CONTINUE. NUMEROUS SHOWERS WITH HEAVY RAINFALL EXPECTED. LULL FROM RAINFALL LIKELY SHORTLY AFTER MIDNIGHT...WHERE SOME LOCALLY DENSE FOG IS POSSIBLE. ANOTHER BATCH OF SHOWERS WITH A HIGHER RISK OF THUNDERSTORMS MOVES IN TOWARD DAYBREAK. E/SE-WINDS DIMINISHING. LLWS LIKELY INTO EARLY TUESDAY MORNING. TUESDAY...CONDITIONS IMPROVING TO VFR BY MIDDAY. COLD FRONT MOVES THROUGH WITH WINDS SHIFTING W/SW. KBOS TAF...MODERATE CONFIDENCE. CONCERNED ABOUT A PERIOD OF ONE HALF MILE OR LESS VISIBILITY OVERNIGHT BUT TIMING UNCERTAIN. IT MIGHT AFFECT THE MORNING PUSH. ALSO LOW RISK OF A THUNDERSTORM BETWEEN 8 AND 12Z. KBDL TAF...MODERATE CONFIDENCE. CONCERNED ABOUT A PERIOD OF ONE HALF MILE OR LESS VISIBILITY OVERNIGHT BUT TIMING UNCERTAIN. LOW RISK OF AN ISOLATED THUNDERSTORM OUTLOOK...TUESDAY NIGHT THROUGH SATURDAY... TUE NIGHT...HIGH CONFIDENCE IN MAINLY VFR CONDITIONS DESPITE THE RISK FOR A SPOT SHOWER OR TWO. WED...MODERATE CONFIDENCE. A COLD FRONT WILL BRING A ROUND OF SCATTERED SHOWERS MAINLY WED AFTERNOON/EARLY EVENING. LOW RISK FOR EVEN A FEW RUMBLES OF THUNDER AND PERHAPS SMALL HAIL/GRAUPEL WITH THE HEAVIEST SHOWERS. THU/FRI/SAT...HIGH CONFIDENCE. MAINLY VFR DESPITE THE RISK FOR A BRIEF DIURNALLY DRIVEN SHOWER OR TWO.
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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/... HIGH CONFIDENCE. GALE WARNINGS REMAIN IN PLACE FOR ALL THE WATERS OUTSIDE BOSTON HARBOR AND NARRAGANSETT BAY. CURRENT PLAN IS TO REPLACE SOME OF THE GALE WARNINGS WITH SMALL CRAFT ADVISORIES TOWARD MIDNIGHT...WHICH IS RIGHT ON SCHEDULE WITH PREVIOUS FORECAST. THIS IS FOR WIND GUSTS UP TO 35 KTS THROUGH THIS EVENING AND INTO THE NIGHT FOR THE OUTER WATERS. RAIN EXPECTED TO CONTINUE WITH STEADY RAIN COMING TO AN END LATE THIS EVENING AND TURNING MORE SHOWERY THROUGH MIDDAY TUESDAY. A FEW ISOLATED RUMBLES OF THUNDER ARE POSSIBLE THIS EVENING...WITH A BETTER CHANCE EARLY TUESDAY MORNING. VISIBILITIES MAY BE LIMITED AT TIMES. OUTLOOK...TUESDAY NIGHT THROUGH SATURDAY... TUESDAY NIGHT AND WEDNESDAY...HIGH CONFIDENCE. MODEST WEST TO SOUTHWEST FLOW EXPECTED AHEAD OF A COLD FRONT...BUT SPEEDS SHOULD REMAIN BELOW SMALL CRAFT THRESHOLDS. A FEW SHOWERS WED AFTERNOON AND EVENING WITH A LOW RISK OF AN ISOLATED THUNDERSTORM WITH SMALL HAIL. THURSDAY THROUGH SATURDAY...HIGH CONFIDENCE. MODEST WESTERLY FLOW AS A RESULT OF CLOSED LOW PRESSURE ACROSS QUEBEC. ENOUGH COLD ADVECTION OVER THE WATERS WILL BE PRESENT TO GENERATE PERIODS OF 25 KNOT WIND GUSTS. MARGINAL SCA SEAS EXPECTED ACROSS THE OUTER-WATERS AT TIMES...BUT WITH GOOD VISIBILITY.
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&& .TIDES/COASTAL FLOODING... EAST TO SOUTHEAST WINDS WILL INCREASE THROUGH TONIGHT. GUIDANCE CONTINUES TO TRACK STRONGEST WINDS ACROSS NEW ENGLAND EARLY THIS EVENING...BEFORE HIGH TIDE OCCURS ALONG THE SOUTH COAST /AROUND 03Z/ AND EAST COAST /ABOUT 06Z/. THIS RESULTS IN WINDS BEGINNING TO SLACKEN AS HIGH TIDE APPROACHES. ALSO SYSTEM IS FAIRLY PROGRESSIVE SO DURATION OF ONSHORE WINDS IS LIMITED. ESTOFS CONTINUES TO BE MORE ROBUST AND REALISTIC THAN ETSS WITH SURGE VALUES 1.0-1.5 FT AT THE TIME OF HIGH TIDE. SEAS ALSO BUILDING TO 10-15 FT JUST OFFSHORE. THIS SHOULD BE SUFFICIENT TO GENERATE AREAS OF MINOR COASTAL FLOODING AND SPLASH OVER. THUS WILL CONTINUE WITH A COASTAL FLOOD ADVISORY FOR THESE LOCATIONS DURING THIS EVENING AND EARLY TUE MORNING HIGH TIDES. WINDS DO NOT LOOK STRONG ENOUGH AT THE TIME OF HIGH TIDE FOR A MODERATE COASTAL FLOOD EVENT. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...COASTAL FLOOD ADVISORY UNTIL 4 AM EDT TUESDAY FOR MAZ007-015- 016-019-022-024. COASTAL FLOOD ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR MAZ020- 021. RI...COASTAL FLOOD ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR RIZ002- 004>007. MARINE...GALE WARNING UNTIL MIDNIGHT EDT TONIGHT FOR ANZ231>235-237-251. SMALL CRAFT ADVISORY UNTIL 4 AM EDT TUESDAY FOR ANZ230-236. GALE WARNING UNTIL 4 AM EDT TUESDAY FOR ANZ250-254>256.
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&& $$ SYNOPSIS...FRANK/RLG NEAR TERM...BELK/FRANK SHORT TERM...RLG LONG TERM...FRANK AVIATION...BELK/FRANK/RLG MARINE...BELK/FRANK/RLG TIDES/COASTAL FLOODING...

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