Area Forecast Discussion
Issued by NWS Boston, MA

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486 FXUS61 KBOX 061423 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1023 AM EDT FRI MAY 6 2016 .SYNOPSIS... CLOUDY DREARY COOL WEATHER CONTINUES TODAY WITH RAIN RE-DEVELOPING ACROSS MUCH OF THE AREA THIS MORNING INTO AFTERNOON AS LOW PRESSURE TRACKS FROM THE MID ATLANTIC TO NJ. DESPITE SCATTERED SHOWERS THIS WEEKEND THERE WILL BE MANY HOURS OF DRY WEATHER ALONG WITH MODERATING TEMPERATURES. ALL OF THIS MOVING OUT SUNDAY AHEAD OF A SWEEPING COLD FRONT BEHIND WHICH COOL TEMPERATURES FOLLOW WITH BREEZY W/NW WINDS. SEE-SAW OF DRY WEATHER FOLLOWED BY QUICK BOUTS OF WET WEATHER NEXT WEEK WITH NEAR OR BELOW SEASONABLE TEMPERATURES. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1015 AM UPDATE... RAIN BANDS CONTINUE TO ROTATE ACROSS MID ATLC REGION THIS MORNING WITH EASTERN EXTENT ACROSS PORTIONS OF W CT. THIS ACTIVITY ASSOCD WITH ANOMALOUS CLOSED LOW SOUTH OF DELMARVA WHICH IS FORECAST TO SLOWLY DRIFT NORTH TODAY. BEST FORCING ALONG THE NOSE OF THE LOW LEVEL JET AND DEEPEST MOISTURE WILL REMAIN FOCUSED NORTH AND WEST OF THE MID LEVEL LOW WHICH WILL KEEP STEADIEST RAINFALL SOUTH AND WEST OF NEW ENG TODAY. HOWEVER...OCCASIONAL SHOWERS WILL SPILL INTO WESTERN MA/CT BASED ON HI-RES GUIDANCE AND WILL HAVE HIGHEST POPS IN THIS REGION WITH POPS DECREASING TO THE EAST. IN FACT MOST OF THE DAY MAY REMAIN DRY ACROSS E MA. LATE TODAY AND MORE LIKELY INTO THE EVENING WE MAY SEE A BAND OF SHOWERS MOVE NORTH ACROSS SNE AHEAD OF VORT LOBE ROTATING AROUND UPPER LOW. REMOVED THUNDER FROM FORECAST FOR TODAY AS INSTABILITY WILL BE CONFINED ACROSS THE MID ATLC REGION UNDER THE UPPER LOW...BUT THUNDER CHANCES WILL INCREASE TONIGHT AS MID LEVEL TEMPS COOL WITH INCREASING TOTAL TOTALS. A FEW BREAKS OF SUN POSSIBLE BUT GIVEN EXTENT OF LOW LEVEL MOISTURE ANY BREAKS WILL LEAD TO CLOUDS FILLING BACK IN. TEMPS NOT AS COOL AS YESTERDAY WITH HIGHS MAINLY IN THE 50S EXCEPT POSSIBLY LOW 60S CT VALLEY IN W MA. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... TONIGHT ... GREATEST RISK OF SHOWERS APPEARS TO BE EARLY IN THE EVENING BEFORE SHORT WAVE/PV ANOMALY LIFTS NORTHWEST OF THE REGION. HIGHEST POPS ACROSS CT INTO WESTERN MA WHERE DEEPEST MOISTURE AND LIFT TRACK. COLD TEMPS ALOFT COMBINED WITH STRONG DEEP LAYER SHEAR WILL SUPPORT POTENTIAL FOR A FEW T-STORMS ACROSS CT AND WESTERN-CENTRAL MA. STILL A RISK OF A FEW SHOWERS FARTHER EAST INTO RI AND EASTERN MA. FOR THE REMAINDER OF THE NIGHT SHOWERS EXIST GIVEN DEEP MOIST CYCLONIC FLOW PERSIST ACROSS THE AREA IN RESPONSE TO VERTICALLY STACKED LOW SETTING UP OVER EASTERN PA. AS THE NIGHT PROGRESSES AREAS OF FOG AND DRIZZLE MAY DEVELOP AS WELL. SATURDAY ... VERTICALLY STACKED LOW OVER EASTERN PA BECOMES AN OPEN WAVE AND MOVES ACROSS THE AREA. THUS CYCLONIC FLOW CONTINUING ACROSS THE MAY YIELD ISOLATED TO WIDELY SCATTERED SHOWERS. IN ADDITION MID LEVELS DRY OUT A BIT AND RESULT IN MID LEVEL LAPSE RATES ON THE ORDER OF 7C/KM. DILEMMA HERE IS ARE MID LEVELS TOO DRY TO SUPPORT CONVECTION? IF ANY SHOWERS CAN DEVELOP -21C TEMPS AT H5 COMBINED WITH DEEP LAYER SHEAR WILL SUPPORT THE POTENTIAL FOR A FEW T-STORMS. OTHERWISE MANY HOURS OF DRY WEATHER SAT AND POSSIBLY BREAKS OF SUNSHINE IN THE AFTERNOON ACROSS CT/RI AND SOUTHEAST MA. THIS MAY PUSH TEMPS INTO THE L60S IN THIS REGION...WITH 50S ELSEWHERE. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... */ HIGHLIGHTS... - RAIN LIKELY SUNDAY MORNING AHEAD OF A SWEEPING COLD FRONT - COOLER AND BREEZY SUNDAY AFTERNOON AND AGAIN MONDAY - SEE-SAW PATTERN OF WET AND DRY WEATHER MID TO LATE WEEK */ DISCUSSION... CONTINUING AN ENSEMBLE FORECAST APPROACH WITH A BROAD VIEW TOWARDS MID-UPPER LEVEL FLOW. N-STREAM PACIFIC / POLAR ENERGY KICKS OUT THE DYING REMNANTS OF THE CLOSED LOW OVER THE DELMARVA. THE SUBSEQUENT CONCLUSION OF THE BLOCKY PATTERN ALLOWS WEATHER SYSTEMS TO SHIFT E AS EVIDENT IN THE SHORT-LIVED NEGATIVE PACIFIC NORTH AMERICAN /PNA/ PATTERN. HEREAFTER FORECAST SOLUTIONS IN AGREEMENT OF PNA RETURNING POSITIVE WITH A STRONGLY NEGATIVE EAST PACIFIC OSCILLATION /EPO/ AND NEAR NEUTRAL AO/NAO TRENDS. SO WITH CERTAINTY RIDGING EXTENDS ACROSS THE NW PACIFIC / W COASTAL N AMERICA YIELDING A FAVORABLE TROUGHING ENVIRONMENT OVER THE N-CENTRAL CONUS WITH PREVALENT RIDGING E. BUT NOT ABSOLUTELY CONFIDENT ON DOWNSTREAM OUTCOMES. DOES APPEAR THAT A PROGRESSIVE FLOW PATTERN EVOLVES E OF N-CENTRAL CONUS TROUGHING CONSIDERING THE NEAR NEUTRAL AO/NAO TREND AND AS THE N ATLANTIC RIDGE DEAMPLIFIES. A STRONG -EPO SIGNAL...FAVOR ENSEMBLE MEANS MAINTAINING TROUGHING OVER THE N-CENTRAL CONUS WITH RIDGING E. TAKING THESE TWO POINTS TOGETHER ALONG WITH N-STREAM INFLUENCES AND INHERENT UNCERTAINTIES...BELIEVE EITHER A CONFLUENT MID-UPPER LEVEL FLOW OR RIDGING PATTERN PREVAILS ACROSS THE NE-CONUS THROUGH WHICH ANY ENERGY FROM THE N-CENTRAL CONUS SLIPPING E UNDERGOES STRETCHING AND WEAKENING BUT STILL RESULTS IN POTENTIAL WET WEATHER OUTCOMES. DO NOT FAVOR THE QUICKNESS OF DETERMINISTIC SOLUTIONS IN A PATTERN BREAKDOWN FURTHER OUT IN TIME SHIFTING IT FURTHER E. SO HIGH CONFIDENCE DREARY DRIZZLY CONDITIONS EMERGE SATURDAY NIGHT BENEATH WEAK RIDGING AHEAD OF N-STREAM ENERGY AND TRAILING COLD FRONT SWEEPING NEW ENGLAND SUNDAY MORNING. LIKELY POPS WITH STRONG LOW-MID LEVEL FORCING OF A FAIRLY MOIST COLUMN UP TO H6. DECENT PRESSURE COUPLING. BREEZY S WINDS BUT STRONGER W/NW FLOW IMMEDIATELY BEHIND THE COLD FRONT AS A COLD POOL DROPS S AND DAYTIME CLEARING / HEATING ALLOWS LAPSE RATES TO STEEPEN UP TO H8 ALLOWING THE MIX-DOWN OF FASTER MOMENTUM AND DRIER AIR. QUIET-DRY OVERNIGHT AS SCATTERED TO BROKEN MID LEVEL CLOUD DECKS WRAP ACROSS THE AREA WITHIN THE CYCLONIC FLOW. BELOW AVERAGE TEMPERATURE TREND. INTO THE WEEK LESSER CONFIDENCE WITH CHALLENGES IN FORECAST MODELS IN HANDLING THE MORPHOLOGY OF INDIVIDUAL WAVES FROM THE W AND ANY N- STREAM INFLUENCES. LOOKING AT A SEE-SAW OF WEATHER OUTCOMES. BRIEF PERIODS OF DRY WEATHER ARE FOLLOWED BY WEAK OVER-RUNNING RAINFALL EVENTS THAT YIELD LIGHT TO MODERATE RAIN OUTCOMES AROUND A QUARTER OF AN INCH. ENSEMBLE WEIGHTING THAT LOOKS OVERALL MARGINAL. NOTHING APPEARING ROBUST NOR A SOAKER. TEMPERATURES NEAR OR BELOW SEASONABLE WILL FOLLOW CLOSE TO ENSEMBLE MEANS / PROBABILITY PREDICTIONS. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 12Z UPDATE... SHORT TERM /THROUGH SATURDAY/... TODAY...MODERATE CONFIDENCE. IFR / MVFR MIXING OUT INTO MIDDAY TOWARDS THE S/W WHERE -RA IS DOMINANT. N/E EVOLVES TO A MIX OF MVFR TO LOW-END VFR. CAN NOT RULE OUT SOME CLEARING. BUT AS AN AREA OF LOW PRESSURE SPINS ACROSS THE DELMARVA...LIKELY TO SEE IFR RETURN FROM S TO N. E WINDS PREVAILING AROUND 10 TO 15 KTS. TONIGHT...MODERATE CONFIDENCE. MVFR LOWERING IFR. TRYING NOT TO BE TOO PESSIMISTIC WITH N/E TERMINALS KEEPING LOWEST CONDITIONS S/W WITH CONTINUED LIKELIHOOD OF RAIN AND ISOLATED TSRA THREATS. -RA/-DZ LIKELY TO LEAD TO SOME VISIBILITY ISSUES. SATURDAY...LOW CONFIDENCE. LOW CONDITIONS IN THE MORNING WITH -DZ/FG GRADUALLY IMPROVING THROUGH THE DAY. NOT ABSOLUTELY SURE HOW THIS EVOLVES BUT THERE IS CONFIDENCE THAT CIGS SHOULD LIFT TOWARDS LATE. KBOS TERMINAL...MVFR CIGS POSSIBLY MIXING OUT TO VFR THIS AFTERNOON...THEN LOWERING INTO EVENING AND OVERNIGHT. CONTINUED E WIND. WILL HOLD MAJORITY -RA JUST TO THE S/W BUT CAN NOT RULE OUT SOME -RA MOVING IN LATE TODAY OR THIS EVENING. KBDL TERMINAL...MAINLY MVFR TO LOW END VFR WITH -RA AND ISOLATED -TSRA THIS EVENING. MAIN THEME FOR MUCH OF TODAY INTO TONIGHT. SHOULD LOWER IFR INTO THIS EVENING. OUTLOOK /SATURDAY NIGHT - TUESDAY NIGHT/...MODERATE CONFIDENCE. VFR TO BEGIN LOWERING TO IFR TOWARDS SUNDAY MORNING WITH -RA AHEAD OF A SWEEPING COLD FRONT. BEHIND THIS CONDITIONS QUICKLY IMPROVE VFR WHILE W/NW WINDS IMMEDIATELY GUST AROUND 25 TO 35 KTS MIDDAY SUNDAY INTO EVENING. A LULL OVERNIGHT SUNDAY...VFR AND BREEZY W/NW WINDS CONTINUE MONDAY AND TUESDAY. CIGS LOWER AND CONDITIONS DETERIORATE AS -RA MOVES BACK IN TUESDAY NIGHT INTO WEDNESDAY MORNING. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 7 AM UPDATE...NO MAJOR CHANGES TO THE FORECAST. TODAY...SCA FOR NNE WINDS BECOMING EAST THIS AFTERNOON. ROUGH SEAS FOR THE OCEAN WATERS GIVEN THE LONG WIND FETCH. RAIN LIKELY RI WATERS LATE MORNING INTO THE AFTERNOON. TONIGHT...MODEST EAST WIND BUT NE SWELLS PERSIST ACROSS THE OCEAN WATERS. VSBY LOWERING IN AREAS OF DRIZZLE/FOG AND SCATTERED SHOWERS. SATURDAY...WINDS BECOMING SSW WHICH WILL RESULT IN IMPROVED VSBYS. LOW RISK OF SCATTERED SHOWERS WITH ISOLATED T-STORM POSSIBLE. OUTLOOK /SATURDAY NIGHT - TUESDAY NIGHT/...MODERATE CONFIDENCE. 5 TO 6 FOOT WAVES AND S FLOW LINGER SATURDAY NIGHT AHEAD OF A COLD FRONT SWEEPING THE WATERS DURING THE EARLY HALF SUNDAY. MAIN CONCERN IS BEHIND THE FRONT WITH W/NW GALES CONTINUING INTO MONDAY. ACTIVITY DIMINISHES MONDAY NIGHT INTO TUESDAY PRIOR TO ANOTHER WET WEATHER SYSTEM AND THE RETURN OF S FLOW TUESDAY NIGHT INTO WEDNESDAY MORN. && .TIDES/COASTAL FLOODING... VERY HIGH ASTRO TIDES TONIGHT /AROUND MIDNIGHT/ WITH BOSTON 12.3 FT AT 1146 PM. MODEST ONSHORE WINDS AND SURFACE PRES ONLY AROUND 1010MB SHOULD RESULT IN SURGE AROUND 0.5 FT. THAT/S SUFFICIENT FOR A MODERATE TO HIGH RISK OF MINOR COASTAL FLOODING ENTIRE EASTERN MA COASTLINE. THUS A COASTAL FLOOD ADVISORY HAS BEEN POSTED FOR THE ENTIRE EASTERN MA COASTLINE FROM 10 PM TONIGHT THRU 2 AM SATURDAY. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...COASTAL FLOOD ADVISORY FROM 10 PM THIS EVENING TO 2 AM EDT SATURDAY FOR MAZ007-015-016-019-022-024. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ231>235-237-250-251. SMALL CRAFT ADVISORY UNTIL 6 AM EDT SATURDAY FOR ANZ254>256. && $$ SYNOPSIS...NOCERA/SIPPRELL NEAR TERM...KJC/NOCERA/SIPPRELL SHORT TERM...NOCERA LONG TERM...SIPPRELL AVIATION...NOCERA/SIPPRELL MARINE...NOCERA/SIPPRELL TIDES/COASTAL FLOODING...

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