Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 041121 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 721 AM EDT SAT JUL 4 2015 .SYNOPSIS... A LOW PRESSURE RACES SOUTH OF NEW ENGLAND TODAY AND MAY BRINGING SOME LIGHT RAIN TO SOUTH COASTAL AREAS. HIGH PRESSURE RETURNS SUNDAY AND LINGERS THROUGH MONDAY. A TRANSITION PERIOD IS LIKELY MID NEXT WEEK...WITH A CHANCE FOR SHOWERS AND THUNDERSTORMS. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 7 AM UPDATE... THE FIRST OF SOME REMNANT SHOWERS FROM UPSTREAM SHORTWAVE ARE JUST SPILLING INTO SRN NEW ENGLAND WITHIN THE LAST COUPLE OF HOURS...BUT ARE QUICKLY DIMINISHING AS THEY MOVE E. LIKELY JUST A SPRINKLE HITTING THE GROUND IN CT AND W MA AT THIS POINT. THIS SAME PATTERN WILL CONTINUE THROUGH MUCH OF THE DAY AS THE LARGER BAND OF RAIN TO THE W TRIES TO MOVE INTO THE REGION BUT GRADUALLY DISSIPATES AS IT DOES SO. CURRENT POPS REFLECT THIS THINKING RATHER WELL...SO ONLY UPDATES WERE TO BRING POPS UP A LITTLE BIT IN THE W EARLIER THIS MORNING WITH THE SHOWERS ONGOING. OTHERWISE...INCREASED TEMPS A BIT ACROSS THE E WHICH WILL LIKELY SEE SOME FILTERED SUNSHINE FOR A TIME THIS MORNING. PREVIOUS DISCUSSION... LOW PRESSURE ALONG THE MID ATLANTIC COAST RACES SOUTH OF OUR AREA ON SATURDAY. THE LOW WILL BE SUPPORTED BY AN UPPER SHORTWAVE LATEST GUIDANCE IS SPLIT INTO TWO CAMPS. THE MORE GLOBAL MODELS ARE MOSTLY DRY ACROSS SOUTHERN NEW ENGLAND. WHILE THE HI- RESOLUTION GUIDANCE IS MORE AGGRESSIVE IN BRINGING RAINFALL TO WESTERN MA...AS WELL AS CAPE COD AND THE ISLANDS. BASED ON THE OVERALL PATTERN...AM THINKING SCATTERED SHOWERS WILL MOVE INTO WESTERN MA AS A MID LEVEL SHORTWAVE CROSSES OUR REGION. THE HIGHEST RAINFALL CHANCES WILL BE SOUTH OF THE MASS PIKE...AND ESPECIALLY ACROSS CAPE COD AND THE ISLANDS. THE MAIN ISSUE WILL BE THE AMOUNT OF LOW LEVEL DRY AIR TO OVERCOME. GIVEN THE TIMING... AM THINKING THE DRIEST CONDITIONS WILL BE TOWARD NORTHEAST MA... WHICH IS THE FARTHEST AWAY FROM THE LOW TO THE SOUTH. THIS SOLUTION IS A COMPROMISE BETWEEN THE TWO AFOREMENTIONED CAMPS. THERE IS NOT A LOT OF INSTABILITY...SO NOT THINKING THUNDERSTORMS WILL BE AN ISSUE TODAY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... THE COASTAL LOW MOVES FARTHER OFFSHORE THIS EVENING...MOVING SOUTH OF NOVA SCOTIA LATE TONIGHT. THIS SHOULD BRING ANY RAINFALL TO AN END LATE THIS EVENING. THE SUPPORTING UPPER TROUGH MOVES EAST OF US BY MORNING. THIS SHOULD BRING A CLEARING TREND AFTER MIDNIGHT WITH WINDS TURNING NORTHWEST. WEAK HIGH PRESSURE MOVES INTO SOUTHERN NEW ENGLAND FROM THE SOUTH SUNDAY. THIS SHOULD MEAN DRY WEATHER WITH HIGHER TEMPERATURES. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... HIGHLIGHTS... * HIGH PRESSURE AND WARMING CONDITIONS INTO EARLY NEXT WEEK. * UNSETTLED CONDITIONS RETURN MID-LATE NEXT WEEK. OVERVIEW AND MODEL PREFERENCES...WITH 04.00Z MODEL GUIDANCE COMING IN...THERE IS BETTER AGREEMENT WITH THE MID AND LONG TERM THAN PREVIOUS RUNS...ALTHOUGH TYPICAL UNCERTAINTY REMAINS IN THE LONG TERM. STRONG RIDGING EARLY IN THE WEEK WILL GIVE WAY TO MAINLY ZONAL FLOW ON THE SW QUADRANT OF A STRONG NRN STREAM VORTEX DEVELOPING ACROSS N CENTRAL CANADA. THE FLATTENING WAVE WILL ARRIVE MID WEEK...WITH HIGH PWATS AND INSTABILITY IN TOW WHICH MAY NEED TO BE WATCHED. THERE ARE TIMING ISSUES...ESPECIALLY REGARDING THE INFLUENCE OF THE RIDGE OF HIGH PRES FOR TUE...BUT WITH BETTER AGREEMENT IN THIS ROUND OF GUIDANCE A BLEND OF OPERATIONAL MODELS WILL WORK WELL AS A BASELINE. DETAILS... SUN NIGHT INTO MON NIGHT...WARM RIDGING BUILDS ACROSS SRN NEW ENGLAND WITH HIGH PRES AT THE SFC. MAINLY DRY WX PREVAILS WITH MODERATING HIGHS/LOWS AS H85 TEMPS INCREASE TO BETWEEN +12C AND +14C BY LATE MON. THIS SUGGESTS HIGHS MAINLY IN 80S ACROSS THE REGION. TUE...UPPER LVL WAVE WILL BE APPROACHING FROM THE W. MODELS INDICATE INCREASING MOISTURE AS PWATS APPROACH 2 STD DEVIATIONS ABOVE NORMAL WITH K-VALUES OVER 30. A WARM FRONT WILL BE THE INITIAL SFC REFLECTION OF THIS WAVE. HOWEVER...SOUNDINGS SUPPORT THE POSSIBILITY OF HIGH PRES REMAINING IN CONTROL THROUGH MUCH OF TUE. THEREFORE...CHANCE FOR AFTERNOON SHRA/T-STORM WITH THE WARM FRONTAL APPROACH MAY BE QUITE LOW TO NEAR ZERO THE FURTHER E ONE GOES. IN FACT...THE BEST AXIS OF SFC CAPE/THETA-E RIDGE IS MAINLY W OF THE MA/NY BORDER. THEREFORE...CHANCE POPS W WILL BE LOWERED TO SLIGHT CHANCE TO NIL POPS FURTHER E. WILL INCLUDE THUNDER WITH THIS FORECAST GIVEN THE FAVORABLE PARAMETERS. WED...AS PREVIOUS FORECASTER NOTED...THIS IS WHERE THE MODEL SOLUTION DIVERGENCE BEGINS TO SHOW MORE SIGNIFICANTLY. MAINLY WITH THE TIMING OF A COLD FRONTAL PASSAGE. GFS REMAINS PROGRESSIVE WHILE ECMWF/CMC CONTINUES TO LINGER AS THE FRONT BEGINS TO PARALLEL THE ZONAL FLOW DEVELOPING ALOFT. WILL CONTINUE WITH THE CHANCE AND SLIGHT CHANCE POPS FROM THE THE PREVIOUS FORECAST SINCE THE CONVERGENT BOUNDARY REMAINS IN PLACE. SOUNDINGS DO SUPPORT SOME SFC BASED CAPE EXCEEDING 1000J/KG AND HIGH K-VALUES...SO WILL CONTINUE TO INCLUDE TS...BUT GIVEN THE LACKING SHEAR...REMAIN SOMEWHAT DUBIOUS OF SEVERE CHANCES AT THIS TIME. THU...THE UNCERTAINTY REMAINS AS THE COLD FRONT CONTINUES TO PUSH FURTHER SOUTHEAST...ALBEIT SLOWLY. WILL GRADUALLY REDUCE POPS FROM N-S DURING THE DAY...BUT WILL HAVE TO WAIT BEFORE WE CAN NAIL DOWN TIMING FOR THE LATE WEEK. FRI AND SAT...UNCERTAINTY REMAINS BUT WITH ZONAL FLOW...A SERIES OF RIDGE/TROUGH COUPLETS IS LIKELY TO YIELD PERIODS OF DRY/POTENTIALLY WET PERIODS ARE LIKELY. INTERESTINGLY...WITH SRN NEW ENGLAND ON THE RIDGE PERIPHERY MAY NEED TO MONITOR FOR MCS STEERING FLOW AS WELL. STILL WAY TOO MANY VARIABLES TO NAIL ANYTHING DOWN...BUT SEASONABLE TEMPS AND LOW TO NIL POPS SHOULD COVER THE SPREAD. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH FRIDAY NIGHT/... TODAY...HIGH CONFIDENCE. MAINLY VFR. A SPOT SHOWER IS POSSIBLE THROUGH EARLY EVENING...WITH THE HIGHEST RISK BEING ALONG THE IMMEDIATE S COAST LATER TODAY. VERY LOW CHANCE OF BRIEF MVFR CONDITIONS IN THESE SHOWERS. WINDS WILL BE GENERALLY LIGHT...WITH SEA BREEZES LIKELY ON COASTLINES. TONIGHT...HIGH CONFIDENCE. RAIN OVER SOUTHEAST MASS/RI SHOULD TAPER OFF DURING THE FIRST PART OF THE NIGHT. MVFR CONDITIONS POSSIBLE IN ANY AREAS OF RAIN/FOG...OTHERWISE VFR WITH CLOUD BASES LIFTING/CLEARING. SUNDAY...HIGH CONFIDENCE. VFR. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/... SUN NIGHT INTO MON...HIGH CONFIDENCE. VFR WITH HIGH PRES. SEA BREEZES LIKELY MON. TUE AND WED...MODERATE CONFIDENCE. FIRST A WARM FRONT TUE...THEN A COLD FRONT WED MAY PROVIDE A FOCUS FOR OCCASIONAL SHOWERS AND THUNDERSTORMS EACH DAY WITH PERIODIC MVFR OR LOWER CONDITIONS. OTHERWISE VFR. SOME FOG POSSIBLE DURING THE OVERNIGHTS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. MODERATE CONFIDENCE TODAY AND TONIGHT...HIGH CONFIDENCE SUNDAY. LOW PRESSURE DEVELOPING ALONG THE MID ATLANTIC COAST WILL PASS OVER OR SOUTH OF THE SOUTHERN OUTER WATERS THIS AFTERNOON AND EVENING. THIS WILL BRING LOWER VSBYS IN RAIN TO THE SOUTHERN WATERS WITH EAST WINDS INCREASING TO 15-20 KNOTS. FARTHER NORTH THE WINDS WILL BECOME EAST...BUT WITH LIGHTER SPEEDS. AS THIS LOW PRESSURE MOVES OFF TO THE EAST...WINDS WILL DIMINISH AND TURN NORTH OVERNIGHT. WEAK HIGH PRESSURE BUILDS OVER THE WATERS SUNDAY. PERSISTENT WINDS WILL BUILD SEAS ACROSS THE OUTER SOUTHERN COASTAL WATERS. THERE HAS BEEN A PERSISTENT SIGNAL THE PAST FEW DAYS FOR 5 FT SEAS. WHILE MARGINAL...DECIDED TO ISSUE A SMALL CRAFT ADVISORY DUE TO THIS PERSISTENT SIGNAL. OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/... SUN NIGHT INTO MON...HIGH CONFIDENCE. ANY LINGERING SWELL RECEDES BELOW 5 FT SUN NIGHT. HIGH PRES THEN BRINGS QUIET BOATING WEATHER TO THE WATERS THROUGH MON. TUE AND WED...MODERATE CONFIDENCE. A WARM FRONT ON TUE...THEN A COLD FRONT ON WED WILL BE APPROACHING FROM THE W. WHILE WINDS SHOULD GENERALLY REMAIN OUT OF THE S-SE...WIND SPEEDS SHOULD REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS. SEAS IS ALSO LIKELY TO REMAIN BELOW SMALL CRAFT THRESHOLDS. SOME SHOWERS/THUNDERSTORMS AND/OR FOG ARE POSSIBLE OVER THE WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 AM TO 5 PM EDT SUNDAY FOR ANZ254. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 8 PM THIS EVENING TO 5 PM EDT SUNDAY FOR ANZ255. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 5 PM THIS AFTERNOON TO 5 PM EDT SUNDAY FOR ANZ256. && $$ SYNOPSIS...BELK/DOODY NEAR TERM...BELK/DOODY SHORT TERM...BELK LONG TERM...DOODY AVIATION...BELK/DOODY MARINE...BELK/DOODY

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