Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 200816 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 416 AM EDT MON APR 20 2015 .SYNOPSIS...
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A WIND SWEPT SOAKING RAIN IS EXPECTED THIS AFTERNOON AND EVENING... WITH EVEN A FEW THUNDERSTORMS POSSIBLE LATE TONIGHT. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ALONG WITH MILD TEMPS TUESDAY MORNING GIVES WAY TO A DRYING TREND DURING THE AFTERNOON. A COLD FRONT WED WILL BE ACCOMPANIED BY SCATTERED SHOWERS FOLLOWED BY MUCH COOLER WEATHER THU INTO NEXT WEEKEND.
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&& .NEAR TERM /UNTIL EARLY EVENING/...
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LOW- TO MID-LEVEL WARM FRONT LIFTING NE ACROSS THE REGION COLLOCATED WITH SYNOPTIC-FRONTOGENETICAL FORCING OF DEEP-LAYER MOISTURE BROUGHT N BY STRONG LOW-LEVEL SE-FLOW. ANOMALOUS PWATS NEARLY 1.5-INCHES /+2 STANDARD DEVIATIONS ABOVE-NORMAL FOR THE MONTH OF APRIL/. WILL SEE LIGHT RAIN SPREAD ACROSS S NEW ENGLAND DURING THE MORNING BECOMING HEAVIER BY MIDDAY CONTINUING INTO EARLY EVENING AS THE CONVERGENT NOSE OF THE LOW-LEVEL JET AND DEEP-LAYER MOISTURE COMBINE ALONG THE WARM-FRONT ALOFT. EXPECTATION OF A BROAD SWATH OF RAIN WITH EMBEDDED HEAVIER SHOWERS...AND POSSIBLE CONVECTION DISCUSSED BELOW. THERE IS THE POSSIBILITY OF LATE DAY INTO EARLY EVENING CONVECTION AS AN ELEVATED CONDITIONALLY UNSTABLE ENVIRONMENT LIFTS ACROSS THE REGION WITH THE AFOREMENTIONED STRONG PUNCH OF WARM-MOIST AIR ALOFT. CONVECTIVE THRESHOLDS NOTEWORTHY WITH NEGATIVE SHOWALTERS AND DECENT TOTAL-TOTALS AND K-INDICES. FORECAST SOLUTIONS VARY AS TO HOW MUCH INSTABILITY IS PRESENT AND THAT ANY INSTABILITY IS ELEVATED AND NOT SURFACE-BASED. ALSO AWARE OF DECENT TURNING WITHIN THE LOW-LEVELS OF THE ATMOSPHERE. NEVERTHELESS AN EVALUATION OF CIPS ANALOGS...AND NOTING THE E/SE-ONSHORE FLOW WOULD LIKELY RESULT IN A STABLE LOW- LEVEL PROFILE AS BUFKIT PROFILES SUGGEST...HAVE LOW CONFIDENCE WITH RESPECT TO A SEVERE WEATHER THREAT. THUNDER NOT OUT OF THE QUESTION BUT INGREDIENTS HAVE TO BE JUST RIGHT TO GET SEVERE OUTCOMES. CIPS ANALOGS AGREE ON BULK OF SEVERE WEATHER THREATS TO OUR SW. CAN NOT RULE OUT SMALL HAIL...AND WITH ANY HEAVY RAIN THERE IS THE POTENTIAL FOR PRECIP-DRAG TO BRING GUSTY WINDS TO THE SURFACE. BUT AGAIN THINK THERE IS A LOW-RISK AND THUS HAVE LOW CONFIDENCE. WILL STILL MONITOR FOR THE POTENTIAL. SEE MORE ON THINKING WITH RESPECT TO FLOODING FURTHER DOWN IN THE DISCUSSION. A CHILLY DAMP DAY. EXPECTING LOW-CLOUDS AND REDUCED VISIBILITIES FOR SOME AREAS...ESPECIALLY WITH HEAVY RAIN BUT COULD ALSO SEE MARINE IMPACTS WITH PROLONGED ONSHORE E/SE-FLOW. SUCH FLOW YIELDING COOLER THAN AVERAGE CONDITIONS WITH HIGHS AROUND THE UPPER-40S.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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OVERNIGHT INTO MIDDAY TUESDAY... A LULL IS EXPECTED INITIALLY WITH A WARM-SECTOR DRY-SLOT FOLLOWING THE ELEVATED PUNCH OF WARM-MOIST AIR COLLOCATED WITH THE WARM FRONT ALOFT. AS THE COLD FRONT APPROACHES...MOISTURE RETURNS WITHIN THE CONTINUED CONDITIONALLY UNSTABLE ENVIRONMENT BENEATH DIFFLUENCE ALOFT WHICH SHOULD RESULT IN RENEWED SHOWER ACTIVITY WITH THUNDER CHANCES. ECHO THE CONVECTION DISCUSSION OF PRIOR OF LOW RISK / LOW CONFIDENCE SEVERE WEATHER. HEAVY RAIN AND GUSTY WINDS REMAIN POSSIBLE. ACTIVITY CONCLUDES DURING THE MORNING HOURS PRIOR TO THE COLD FRONT SWEEPING THROUGH THE REGION. BY THIS POINT STORM-TOTAL AMOUNTS ARE FORECAST TO BE IN THE 1.0- TO 1.5-INCH RANGE. CONSIDERING MUCH OF THE ACTIVITY TAKING PLACE WITHIN A 12- TO 18-HOUR PERIOD...AND THE PROGRESSIVE FLOW WITHIN H85-3... HAVE LOW CONFIDENCE CONCERNING WIDESPREAD FLOODING. NUISANCE POOR- DRAINAGE FLOODING IS NOT OUT OF THE QUESTION AS EMBEDDED HEAVIER SHOWERS AND CONVECTION ARE ANTICIPATED. COULD SEE SHORT-DURATION LOCALIZED HEAVY RAINFALL...BUT OVERALL SREF PROBABILITIES REMAIN LOW FOR 1-INCH OF PRECIPITATION WITHIN 12-HOURS. 1-HOUR FLASH FLOOD GUIDANCE IS AROUND 1.75-INCHES. MMEFS SUGGESTS THAT WITH ANTICIPATED RAINFALL THE CT-RIVER MAY REMAIN SWOLLEN FOR SLIGHTLY LONGER. TUESDAY MIDDAY TOWARDS EVENING... COLD AIR ADVECTION PROCEEDING ALLOWING FOR STEEP LAPSE RATES ON UP TO H7. EXPECTING TO BREAK OUT ESPECIALLY WITHIN THE DRY-SLOT REGION WHICH SHOULD ALLOW FOR SUNSHINE TO WARM TEMPERATURES TO NEAR 70- DEGREES. SOME QUESTION AS TO WHETHER LOW-TOPPED CONVECTION COULD DEVELOP. BUT THE ATMOSPHERIC PROFILE BEING SO DRY AS INDICATED BY THE NEGATIVE K-INDEX VALUES LEADS TO A QUIET WEATHER PERIOD TO CLOSE OUT THE EARLY-WEEK.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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HIGHLIGHTS... * PRECIP - GREATEST RISK FOR WIDESPREAD SHOWERS WED AND WED NGT * TEMPS - MILD WED THEN COOLER THAN NORMAL THURSDAY THRU SUN SYNOPTIC OVERVIEW AND MODEL PREFERENCES... ANOMALOUS CLOSED LOW OVER THE NORTHERN GREAT LAKES WED/THU BECOMES THE MAIN WEATHER FEATURE FOR OUR AREA THIS PERIOD. BY FRI MID LEVEL LOW DRIFTS ACROSS NEW ENGLAND THEN EAST OF THE AREA BY NEXT WEEKEND BUT STILL CLOSE ENOUGH FOR AT LEAST SOME IMPACT. DETERMINISTIC AND ENSEMBLE GUIDANCE IN GOOD AGREEMENT INTO THU THEN GFS AND ITS ENSEMBLES GEFS TRACK MID LEVEL LOW FARTHER NORTH INTO QUEBEC. MEANWHILE THE ECMWF/UKMET AND ECENS DIG MID LEVEL LOW FARTHER SOUTH INTO NEW ENGLAND FRI THEN SOUTH OF NOVA SCOTIA SAT. GIVEN THE EVOLVING BLOCKY PATTERN AND SUPPORT FROM -NAO/AO AND EPO TELECONNECTIONS WE WILL FAVOR THE MORE AMPLIFIED AND SUPPRESSED EC/UKMET AND ECENS SOLUTION THIS PERIOD. THIS FLOW REGIME WILL SUPPORT TEMPS COOLER THAN NORMAL THURSDAY THRU SUNDAY ALONG WITH GREATEST RISK FOR WIDESPREAD SHOWERS WED/WED NIGHT ASSOCIATED WITH IMPRESSIVE COLD FRONT. DAILY DETAILS... WED...SOME UNCERTAINTY ON EXACT TIMING AND AMPLITUDE OF NORTHERN STREAM SHORT WAVE BUT GOOD MODEL AGREEMENT ON QPF FOR A PERIOD OF SHOWERS WED INTO WED NIGHT AS FAIRLY VIGOROUS SHORT WAVE AND ATTENDING COLD FRONT SWEEP ACROSS THE AREA. STILL MILD AHEAD OF THE FRONT WITH MULTI MODEL 2M TEMPS IN GOOD AGREEMENT ON HIGHS 60-65! ENJOY AS PATTERN CHANGE WILL USHER IN MUCH COOLER WEATHER THU/FRI AND THIS WEEKEND. THURSDAY AND FRI...MID/UPPER LEVEL LOW OVER NORTHERN GREAT LAKES BEGINS TO DRIFT TOWARD AND OVER NEW ENGLAND BY FRI. LOWER HEIGHTS ALOFT CORRESPONDS TO COLDER TEMPS AT THE SURFACE. THUS BIG COOL DOWN THIS PERIOD WITH HIGHS ONLY 50-55...POSSIBLY ONLY U40S HIGH TERRAIN WELL INLAND. 850 MB TEMP ANOMALY INDICATES TEMPS ABOUT -1 STANDARD DEVIATION BELOW CLIMO. MAINLY DRY BUT CAN`T RULE OUT AN ISOLATED AFTERNOON OR EARLY EVENING SHOWER. SATURDAY AND SUNDAY...MID/UPPER LEVEL LOW FINALLY EXITS NORTH AND EAST OF THE REGION. THUS TEMPS WARM SOMEWHAT ALOFT AND LOWERS THE RISK FOR AFTN/EARLY EVENING SHOWERS.
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&& .AVIATION /08Z MONDAY THROUGH FRIDAY/...
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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/... TODAY...CONDITIONS DETERIORATING TO IFR-LIFR. WIDESPREAD RAIN WITH EMBEDDED +RA. CHANCE TSRA LATE. BLUSTERY E-FLOW WITH GUSTS UP TO 35 KTS ALONG THE E-COAST. LLWS WITH 50-60 KT SE-JET 2 KFT AGL BEGINNING AROUND MIDDAY. TONIGHT...IFR-LIFR CONTINUING. -SHRA WITH CHANCE TSRA. E/SE-WINDS DIMINISHING. LLWS WITH A 50-60 KT SE-JET 2 KFT AGL INITIALLY... LESSENING LATE 40-50 KTS PRIOR TO CONCLUDING. TUESDAY...CONDITIONS IMPROVING TO VFR RATHER QUICKLY...ESPECIALLY BY MIDDAY. COLD FRONT SWEEPING THE TERMINALS WITH WINDS SHIFTING W/SW. KBOS TAF...MODERATE CONFIDENCE. IFR MARINE STRATUS MAY IMPACT THE TERMINAL EARLIER THAN FORECAST. KBDL TAF...MODERATE CONFIDENCE. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... TUE NIGHT...HIGH CONFIDENCE FOR VFR WITH MODEST SSW WINDS. MAINLY DRY TOO. WED...MODERATE CONFIDENCE. COLD FRONT INCREASES THE RISK FOR WIDESPREAD SHOWERS. CONDITIONS MAY DIP TO MVFR IN TIMES OF SHOWERS. THU AND FRI...HIGH CONFIDENCE. MAINLY VFR. ISOLATED AFTERNOON / EVENING SHOWER POSSIBLE.
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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/... TODAY...CONDITIONS DETERIORATING AS WIDESPREAD RAIN WITH EMBEDDED HEAVIER SHOWERS SPREAD W TO E ACROSS THE WATERS. LIKELY TO SEE VISIBILITY RESTRICTIONS. CHANCE OF THUNDERSTORMS LATE. INCREASING E-FLOW WITH GALE FORCE GUSTS OVER THE E/SE-WATERS WHERE CONFIDENCE IS HIGHEST. SMALL- CRAFT ADVISORIES ELSEWHERE WITH THE POSSIBILITY OF AN INTERMITTENT GALE- FORCE GUST. SEAS BUILDING UP AROUND 10 TO 12 FEET ON THE OUTER WATERS. TONIGHT...CONDITIONS IMPROVE THROUGH THE PERIOD W TO E. WINDS DIMINISH ALLOWING SEAS TO BEGIN TO SUBSIDE AS RAINS WITH CHANCE THUNDERSTORMS PUSH E/NE. EXPECT SEAS INITIALLY AROUND 10 TO 12 FEET ON THE OUTER WATERS. ANY VISIBILITY ISSUES TO LIFT. TUESDAY...CONDITIONS IMPROVING RATHER QUICKLY...ESPECIALLY BY MIDDAY. COLD FRONT SWEEPS THE WATERS WITH WINDS SHIFTING W/SW. WAVES CONTINUING TO DIMINISH DOWN TO AROUND 6 TO 8 FEET ON THE OUTER WATERS. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... TUE NIGHT...HIGH CONFIDENCE FOR MODEST SSW WINDS. LEFTOVER SE SWELLS CONTINUE. WED/WED NIGHT...COLD FRONT SWEEPS ACROSS THE REGION AND WILL BE ACCOMPANIED BY SCATTERED SHOWERS. MODEST SSW WIND SHIFT TO WNW. THU AND FRI... MODEST WNW WINDS AS LOW PRES MEANDERS OVER MAINE OR NEW BRUNSWICK.
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&& .TIDES/COASTAL FLOODING...
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EAST TO SOUTHEAST WINDS WILL INCREASE TODAY INTO 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.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...COASTAL FLOOD ADVISORY FROM MIDNIGHT TONIGHT TO 4 AM EDT TUESDAY FOR MAZ007-015-016-019-022-024. COASTAL FLOOD ADVISORY FROM 8 PM THIS EVENING TO MIDNIGHT EDT TONIGHT FOR MAZ020-021. RI...COASTAL FLOOD ADVISORY FROM 8 PM THIS EVENING TO MIDNIGHT EDT TONIGHT FOR RIZ002-004>007. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT TUESDAY FOR ANZ231>235-237- 255-256. SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 4 AM EDT TUESDAY FOR ANZ230-236. GALE WARNING FROM NOON TODAY TO 4 AM EDT TUESDAY FOR ANZ250- 251-254.
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&& $$ SYNOPSIS...NOCERA/SIPPRELL NEAR TERM...SIPPRELL SHORT TERM...SIPPRELL LONG TERM...NOCERA AVIATION...NOCERA/SIPPRELL MARINE...NOCERA/SIPPRELL TIDES/COASTAL FLOODING...WFO BOX STAFF

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