Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 192323 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 723 PM EDT SUN APR 19 2015 .SYNOPSIS... A WIND SWEPT SOAKING RAIN IS EXPECTED MONDAY AND MONDAY NIGHT...WITH EVEN A FEW THUNDERSTORMS POSSIBLE AT NIGHT. SCATTERED SHOWERS AND MILD TEMPS TUESDAY MORNING GIVE WAY TO A DRYING TREND DURING THE AFTERNOON. THEN MUCH COOLER WEATHER OVERSPREADS THE AREA MID TO LATE NEXT WEEK ALONG WITH THE RISK OF SCATTERED SHOWERS...ESPECIALLY DURING THE AFTERNOON AND EVENING. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 7 PM UPDATE... GRADIENT SOUTHEASTERLY FLOW ALREADY DEVELOPING ON THE FAR NORTHERN PERIPHERY INFLUENCE OF A WARM FRONT. THIS FLOW HAS LED TO ANOTHER WIDE SPREAD IN AFTERNOON AND EVENING TEMPERATURES MAINLY OF COURSE DUE TO MARINE INFLUENCE. OTHERWISE...EXPECT EXPANDING HIGH AND MID CLOUDS THROUGH THE OVERNIGHT HOURS WHICH WILL LIMIT DIURNAL COOLING SOMEWHAT STILL EXPECT MINS A BIT COOLER THAN LAST NIGHT GIVEN THE COOLER START AND BULK OF THE RAINFALL HOLDS OFF UNTIL MAINLY 12Z AND AFTER. SPEAKING OF THIS RAINFALL...TIMING OF POPS/WX LOOKS GOOD SO NO PLANNED CHANGES WITH THIS UPDATE. PREVIOUS DISCUSSION... A WIDE RANGE IN TEMPS AGAIN LATE THIS AFTERNOON...ALTHOUGH NOT NEARLY AS EXTREME AS YESTERDAY. LATE AFTERNOON READINGS RANGED FROM THE UPPER 40S TO LOWER 50S ALONG THE IMMEDIATE COAST AND LOWER 60S IN THE CT RIVER VALLEY. TEMP RANGE WILL BEGIN TO NARROW AFTER SUNSET...AS THE DRY AIR IN PLACE ALLOWS THE INTERIOR TO BEGIN TO RADIATE OUT. HIGH PRESSURE NEAR THE CANADIAN MARITIMES WILL VERY SLOWLY SHIFT EAST TONIGHT...AS LOW PRESSURE APPROACHES FROM THE MIDWEST. WHILE IT WILL REMAIN DRY TONIGHT...MID/HIGH LEVEL CLOUDINESS WILL INCREASE FROM THE WEST AND THICKEN AFTER MIDNIGHT. LOW TEMPS WILL BOTTOM OUT MAINLY IN THE UPPER 30S AND LOWER 40S. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... MONDAY... A WAVE OF LOW PRESSURE APPROACHES FROM THE WEST WITH HIGH PRESSURE RETREATING ACROSS THE EASTERN CANADIAN MARITIMES. THIS WILL GENERATE A CHILLY EAST WIND AT THE SURFACE WITH A SOUTHERLY LOW LEVEL JET JUST OFF THE DECK. THE RESULT WILL BE WIDESPREAD RAIN WHICH WILL WORK ACROSS THE REGION FROM WEST TO EAST. THE RAIN SHOULD ARRIVE ACROSS WESTERN MA/NORTHERN CT BETWEEN 7 AND 10 AM...REACHING EASTERN MA/RI BETWEEN 10 AM AND 1 PM. THE RAIN WILL INITIALLY BE LIGHT...BUT SHOULD PICKUP IN INTENSITY FROM WEST TO EAST DURING THE MID TO LATE AFTERNOON HOURS...BECOMING MODERATE TO HEAVY AT TIMES. IT WILL BE UNSEASONABLY CHILLY WITH TEMPS MAINLY IN THE 40S TO NEAR 50 MONDAY AFTERNOON. IN ADDITION...INCREASING PRESSURE GRADIENT WILL RESULT IN EASTERLY WIND GUSTS OF 25 TO 35 MPH ALONG THE COAST. THIS WILL RESULT IN WIND CHILL VALUES IN THE MIDDLE 30S TO THE LOWER 40S! MONDAY NIGHT... WAVE OF LOW PRESSURE WILL LIFT NORTHEAST AND MOVE NEAR OR NORTHWEST OF THE I-95 CORRIDOR. THIS SHOULD ALLOW RHODE ISLAND AND AT LEAST SOUTHEAST MA TO WARM SECTOR...ALLOWING TEMPS TO RISE INTO THE 50S. LOW LEVEL JET OF 50 KNOTS COMBINED WITH PWATS OF 1 TO 1.5 INCHES WILL ALLOW FOR NUMEROUS SHOWERS...ESPECIALLY DURING THE FIRST PART OF THE NIGHT. IN ADDITION...SHOWALTER INDICES DROPPING BELOW ZERO MAY RESULT IN A FEW ELEVATED THUNDERSTORMS. THE HIGHEST RISK OF ANY CONVECTION WILL BE ACROSS RHODE ISLAND/SOUTHEAST MA ON THE NOSE OF THE LOW LEVEL JET...BUT ITS POSSIBLE ACROSS THE ENTIRE REGION. GIVEN RELATIVELY HIGH PWATS AND GOOD FORCING...BRIEF HEAVY RAIN MAY RESULT IN TYPICAL NUISANCE POOR DRAINAGE STREET FLOODING. HOWEVER...NO SIGNIFICANT FLOODING PROBLEMS ARE EXPECTED AS WE ARE ONLY LOOKING AT BETWEEN 1 AND 2 INCHES OF TOTAL RAINFALL. THE ONE AREA WE MAY HAVE TO WATCH IS ACROSS EASTERN CT/RI/SOUTHEAST MA. A FEW OF OUR MESOSCALE MODELS ARE INDICATING THE POTENTIAL FOR 2+ INCHES OF RAIN WITH PERHAPS SOME CONVECTION. AGAIN THOUGH...THIS REALLY LOOKS LIKE TYPICAL BRIEF NUISANCE POOR DRAINAGE STREET FLOODING EVENT. && .LONG TERM /TUESDAY THROUGH SUNDAY/... HIGHLIGHTS... * TUE...SCATTERED MORNING SHOWERS THEN AN AFTERNOON DRYING TREND * WED-SAT...COOLER WITH PERIODS OF SHOWERS...MAINLY DIURNAL SYNOPTIC OVERVIEW AND MODEL PREFERENCES... AMPLIFYING NORTHERN STREAM PHASES WITH SOUTHERN PLAINS CUTOFF LOW TODAY TO FORM AN ANOMALOUS LOW/VORTEX OVER THE GREAT LAKES TUE. THEREAFTER THIS UPPER LOW WILL BE VERY SLOW TO MOVE AS HIGH LATITUDE BLOCKING DEVELOPS WITH POSITIVE HEIGHT ANOMALY EVOLVING OVER THE SOUTHERN DAVIS STRAIT. THIS RESULTS IN A VERY SLOW MOVING VORTEX FROM THE NORTHERN GREAT LAKES WED TO ONLY ADVANCING EASTWARD INTO MAINE BY NEXT WEEKEND! WHILE THIS SEEMS EXTREME IT/S DOES HAVE SUPPORT FROM TELECONNECTIONS AS AO/NAO AND EPO AS ALL THREE INDICES GO NEGATIVE. GIVEN GOOD MODEL AGREEMENT A BLEND OF OPERATIONAL GUIDANCE WILL WORK BEST AS A BASELINE FOR THIS PORTION OF THE FORECAST. DAILY DETAILS... TUESDAY...TRAILING SHORT WAVE TROUGH AND ATTENDING COLD FRONT ALONG WITH TRIPLE POINT LOW WILL BE MOVING ACROSS THE AREA DURING THE MORNING. THIS WILL LIKELY YIELD A ROUND OF SHOWERS TO THE REGION. INSTABILITY ALOFT MAY BE SUFFICIENT FOR ELEVATED THUNDER. IF NOT AT THE VERY LEAST THIS INSTABILITY WILL ENHANCE SHOWER INTENSITY AND ASSOCIATED DOWNPOURS. BY AFTERNOON DRY SLOT WILL BE WORKING ITS WAY AROUND THE SYSTEM AND INTO THE REGION. SO SUSPECT WITH DEEPENING DRY LAYER AND COLD ADVECTION TUE AFTERNOON WILL FEATURE A DRYING TREND FROM SOUTH TO NORTH. IN ADDITION...MILD START TO THE DAY COMBINED WITH BREAKS OF AFTERNOON SUNSHINE POSSIBLE AND WEAK COLD AIR ADVECTION HIGHS WILL WARM INTO THE 60S. WED AND THU...WHILE BOTH ENSEMBLES AND DETERMINISTIC GUIDANCE ARE IN VERY GOOD AGREEMENT ON THE TIMING AND TRACK OF MID LEVEL CLOSED LOW...AS EXPECTED MODELS ARE STRUGGLING WITH THE AMPLITUDE AND TIMING OF INDIVIDUAL SHORT WAVES CIRCULATE AROUND THE VORTEX. THUS LOW CONFIDENCE ON TIMING SHOWER THREAT THIS PERIOD. TRENDING COOLER AS MID LEVEL LOW AND ASSOCIATED COLD POOL ALOFT ADVECT EASTWARD INTO THE REGION. COOLER THU THAN WED. FRIDAY AND SATURDAY...ECENS/EPS SUGGEST CORE OF COLD AIR ALOFT SETTLES OVER THE AREA AS MID LEVEL LOW TRACKS ACROSS NORTHERN NY STATE AND NORTHERN NEW ENGLAND WITH 850 TEMPS COOLING TO -2C TO -5C! RISK OF SHOWERS TOO GIVEN COLD AIR AND CYCLONIC FLOW ALOFT. NOT OUT OF THE QUESTION THAT SCATTERED RAIN SHOWERS MIX WITH SOME SNOW AT TIMES ACROSS THE HIGHER TERRAIN! && .AVIATION /00Z MONDAY THROUGH FRIDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. .SHORT-TERM /THIS AFTERNOON THROUGH MONDAY NIGHT/... NO SIGNIFICANT CHANGES WITH THE 00Z TAFS. TONIGHT...HIGH CONFIDENCE IN VFR CONDITIONS DESPITE INCREASING MID LEVEL CLOUDINESS. MONDAY...MODERATE TO HIGH CONFIDENCE. CONDITIONS DETERIORATE TO MVFR FROM WEST TO EAST MONDAY MORNING INTO MID AFTERNOON IN WIDESPREAD RAIN. IFR CONDITIONS MAY DEVELOP BY MID TO LATE AFTERNOON FROM WEST TO EAST...AS HEAVIER RAIN WORKS INTO THE REGION. THIS IN RESPONSE TO WIDESPREAD RAIN WORKING IN FROM THE WEST. EASTERLY WINDS WILL ALSO GUST TO 30 KNOTS ALONG THE COAST BY AFTERNOON. MONDAY NIGHT...MODERATE TO HIGH CONFIDENCE. MAINLY LOW END MVFR TO IFR CONDITIONS. PERIODS OF SHOWERS CONTINUE MONDAY NIGHT AS AT LEAST THE SOUTHERN HALF OF THE REGION PROBABLY ENTERS THE WARM SECTOR. A FEW EMBEDDED THUNDERSTORMS ARE ALSO POSSIBLE...WITH THE HIGHEST RISK ON THE SOUTH COAST NEAR THE NOSE OF THE LOW LEVEL JET BUT THEY ARE POSSIBLE ACROSS THE ENTIRE REGION. WHILE SOUTHEAST WINDS MAY GUST TO 30 KNOTS ALONG THE COAST...LLWS OF 50 TO 60 KNOTS EXPECTED AT 2000 THOUSAND FEET WITH DEVELOPING LOW LEVEL JET. KBOS TAF...HIGH CONFIDENCE THROUGH 14Z MONDAY IN VFR CONDITIONS. MVFR CONDITIONS IN SOME RAIN ARE EXPECTED TO REACH THE TERMINAL BETWEEN 15Z AND 18Z...SOME IFR TO FOLLOW. KBDL TAF...HIGH CONFIDENCE THROUGH 11 OR 12Z MONDAY IN VFR CONDITIONS. MVFR CONDITIONS IN SOME RAIN ARE EXPECTED TO REACH THE TERMINAL BETWEEN 12Z AND 14Z. OUTLOOK...TUESDAY THROUGH FRIDAY... TUE INTO EARLY WED...HIGH CONFIDENCE. CONDITIONS IMPROVE TO VFR EARLY TUE. ALTHOUGH LINGERING CLOUDS AND SHOWERS ARE POSSIBLE. THE VFR CONDITIONS CONTINUE INTO EARLY WED W WINDS ON TUE GIVE WAY TO SW WINDS ON WED...WITH A FEW GUSTS TO AROUND 20 KT POSSIBLE. WED EVENING INTO EARLY THU...MODERATE CONFIDENCE. COLD FRONT INCREASES THE RISK FOR MORE WIDESPREAD SHOWERS. CONDITIONS MAY DIP TO MVFR/IFR AT TIMES DURING THE OVERNIGHT HOURS. REST OF THU AND FRI...HIGH CONFIDENCE. MAINLY VFR. CHANCE FOR AFTERNOON/EVENING SHOWERS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH MONDAY NIGHT/... TONIGHT...HIGH CONFIDENCE WINDS/SEAS REMAIN BELOW SCA THRESHOLDS THROUGH AT LEAST 8 OR 9Z WITH RELATIVELY WEAK PRESSURE GRADIENT IN PLACE. MONDAY AND MONDAY NIGHT...MODERATE TO HIGH CONFIDENCE. HIGH PRESSURE OVER THE CANADIAN MARITIMES AND AN APPROACHING LOW PRESSURE SYSTEM FROM THE WEST WILL RESULT IN AN INCREASING PRESSURE GRADIENT. PERSISTENT EAST TO SOUTHEAST WIND GUSTS OF 25 TO 35 KNOTS DEVELOP BY MONDAY AFTERNOON AND CONTINUE INTO MONDAY EVENING. WE HOISTED GALES FOR OUR EASTERN OUTER-WATERS WITH BETTER MIXING EXPECTED AND HAVE STRONG SCA POSTED ELSEWHERE. HOWEVER...BRIEF SOUTHEAST GALE FORCE WIND GUSTS CAN NOT BE RULED OUT ANYWHERE MONDAY NIGHT ESPECIALLY IF WE CAN GENERATE ANY CONVECTION. SEAS WILL BUILD TO BETWEEN 10 AND 15 FEET WITH LONG EASTERLY FETCH ACROSS OUR EASTERN WATERS. SHOWERS...A FEW THUNDERSTORMS AND PATCHY FOG WILL ALL CONTRIBUTE TO REDUCED VISIBILITIES FOR MARINERS AT TIMES. OUTLOOK...TUESDAY THROUGH FRIDAY... TUE AND WED...HIGH CONFIDENCE. ALTHOUGH W-SW WINDS WILL BE DIMINISHING DURING THE DAY ON TUE...LINGERING LARGE SWELL OF 10+ FT ON THE OCEAN WATERS EXPECTED. THIS SWELL REMAINS ABOVE THE 5 FT THRESHOLD ON WED AS WELL. THEREFORE...SMALL CRAFT ADVISORIES ARE LIKELY TO CONTINUES. THU AND FRI... WINDS SHIFT BACK TO THE SW ON THU AHEAD OF A COLD FRONT...WITH THE POSSIBILITY OF MAINTAINING SWELLS ON S WATERS. WINDS BACK TO THE W BY FRI. COULD SEE PERIOD GUSTS TO AROUND 25 KT EACH AFTERNOON...SO WITH THE LEFTOVER SEAS AND PERIODIC GUSTS...SOME SMALL CRAFT ADVISORIES MAY BE NEEDED AT TIMES. && .TIDES/COASTAL FLOODING... VERY HIGH ASTRONOMICAL TIDES OCCUR LATE THIS EVENING AND JUST AFTER MIDNIGHT. WHILE WE CAN NOT RULE OUT SOME VERY MINOR SPLASH OVER...DID NOT THINK IT WAS WORTH ANY HEADLINES. LATER SHIFTS WILL HAVE TO MONITOR CLOSELY. EAST TO SOUTHEAST WINDS WILL INCREASE MONDAY INTO MONDAY EVENING. CURRENT GUIDANCE SUGGESTS THE STRONGEST WINDS OCCUR MONDAY AFTERNOON AND EARLY EVENING AND NOT COINCIDE WITH THE HIGHEST ASTRONOMICAL TIDE. HOWEVER...THE HIGH TIDE WERE CONCERNED ABOUT OCCURS LATE MONDAY EVENING ALONG THE SOUTH COAST AND VERY EARLY TUE MORNING ALONG THE EASTERN MA COAST. WE PROBABLY ARE LOOKING AT A 1 TO 1.5 FOOT STORM SURGE ALONG WITH 10 TO 15 FOOT SEAS OFFSHORE. THIS SHOULD BE ENOUGH TO GENERATE POCKETS OF MINOR COASTAL FLOODING AND SPLASH OVER. THEREFORE...DECIDED TO HOIST A COASTAL FLOOD ADVISORY FOR THESE LOCATIONS DURING THEIR LATE MONDAY 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... CT...NONE. MA...COASTAL FLOOD ADVISORY FROM MIDNIGHT MONDAY NIGHT TO 4 AM EDT TUESDAY FOR MAZ007-015-016-019-022-024. COASTAL FLOOD ADVISORY FROM 8 PM MONDAY TO MIDNIGHT EDT MONDAY NIGHT FOR MAZ020-021. RI...COASTAL FLOOD ADVISORY FROM 8 PM MONDAY TO MIDNIGHT EDT MONDAY NIGHT FOR RIZ002-004>007. MARINE...SMALL CRAFT ADVISORY FROM 5 AM MONDAY TO 8 AM EDT TUESDAY FOR ANZ231>235-237. SMALL CRAFT ADVISORY FROM 10 AM MONDAY TO 4 AM EDT TUESDAY FOR ANZ230-236. GALE WARNING FROM NOON MONDAY TO MIDNIGHT EDT MONDAY NIGHT FOR ANZ250-251-254. SMALL CRAFT ADVISORY FROM 2 AM MONDAY TO 8 AM EDT TUESDAY FOR ANZ255-256. && $$ SYNOPSIS...FRANK/DOODY NEAR TERM...FRANK/DOODY SHORT TERM...FRANK LONG TERM...DOODY AVIATION...FRANK/DOODY MARINE...FRANK/DOODY TIDES/COASTAL FLOODING...

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