Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 050807 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 407 AM EDT SUN JUL 5 2015 .SYNOPSIS...
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HIGH PRESSURE RETURNS TODAY...AND LINGERS THROUGH MONDAY. BECOMING MORE HUMID TUESDAY AND WEDNESDAY. A SERIES OF FRONTS WILL BRING A RISK FOR SHOWERS AND THUNDERSTORMS TUESDAY AND WEDNESDAY. A FRONT WILL STALL SOUTH OF THE AREA ON THURSDAY AND FRIDAY.
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&& .NEAR TERM /THROUGH TODAY/...
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HIGH PRESSURE FROM THE PLAINS BUILDS EAST OVER NEW ENGLAND. AS NOTED BY PREVIOUS FORECASTER...MODEL CROSS SECTIONS OF RH SHOW A VERY SHALLOW LAYER OF MOISTURE NEAR 800 MB. THIS SUGGESTS THE POSSIBILITY OF SOME DIURNAL CUMULUS DEVELOPING. PLENTY OF SUNSHINE TODAY WILL MEAN MUCH HIGHER TEMPERATURES THAN WHAT WE SAW ON INDEPENDENCE DAY. WEAK PRESSURE GRADIENT WILL LEAD TO THE DEVELOPMENT OF SEABREEZES...MAINLY THIS AFTERNOON.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM MONDAY/...
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FAIR SKIES TONIGHT WITH LIGHT WINDS AND RADIATIONAL COOLING. DEW POINTS RISE TO AROUND 60...SO TEMPERATURES SHOULD NOT BE AS LOW AS THEY HAVE BEEN THE PAST FEW DAYS. THIS MAY ALSO SUPPORT PATCHES OF FOG DEVELOPING LATE AT NIGHT...ESPECIALLY ACROSS WESTERN MA. HIGH CONFIDENCE FOR DRY CONDITIONS MONDAY...AS DEEP HIGH PRESSURE SHOULD BE IN PLACE NEAR SOUTHERN NEW ENGLAND. WARMER STILL...WITH THE HIGHER STARTING POINT. DEW POINTS CONTINUE TO SLOWLY INCREASE AS WELL. WEAK PRESSURE GRADIENT SHOULD LEAD TO MORE SEABREEZES.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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HIGHLIGHTS... * SHOWERS AND THUNDERSTORMS ON TUESDAY AND WEDNESDAY * UNSETTLED WEATHER MAY CONTINUE INTO LATE WEEK OVERVIEW AND MODEL PREFERENCES...GRADUAL TRANSITION PERIOD IS EXPECTED THROUGH THE LONG TERM...AS RIDGING ACROSS THE NE CONUS GIVES WAY TO NEAR ZONAL FLOW THANKS TO PINWHEELING SHORTWAVES AROUND A CENTRALIZED VORTEX IN N CENTRAL CANADA. ALTHOUGH SRN NEW ENGLAND REMAINS ON THE SRN PERIPHERY OF THE MEAN JET WITHIN THIS ZONAL FLOW /EVEN H5 HEIGHT ANOMALIES ARE NEAR TO ABOVE NORMAL/ THIS FLOW MAKES NAILING DOWN TIMING OF WEAK RIDGE/TROUGH COUPLETS DIFFICULT FOR LATE IN THE WEEK. THIS DIFFICULTY IS EXACERBATED BY A STALLED FRONTAL BOUNDARY NOT TOO FAR TO THE S...WHICH WILL PROVIDE A NEAR SFC BAROCLINIC ZONE FOR THESE WAVES TO WORK UPON. THEREFORE...EXACTLY HOW UNSETTLED THE LATE WEEK PERIOD WINDS UP BEING REMAINS IN FLUX...BUT GIVEN FAIR AGREEMENT ON AT LEAST THE SYNOPTIC SCALE BETWEEN OPERATIONAL/ENSEMBLE GUIDANCE A BLEND WILL BE A GOOD STARTING POINT WITH THIS UPDATE. DETAILS... MON NIGHT INTO TUE...HIGH PRES WILL SHIFT OFFSHORE OF THE REGION...ALLOWING FOR RETURN FLOW AND WARM ADVECTION IN INCREASE. THIS WILL LEAD TO THE SLOW APPROACH OF A WEAKENING WARM FRONT DURING THE DAY ON WED. BUFKIT DATA DOES SHOW SFC INSTABILITY IS AVAILABLE...MAINLY IN THE FORM OF THIN-PROFILED 500-1000 J/KG OF CAPE AND PWATS NEARLY 1.5 STD DEVIATIONS ABOVE NORMAL. SPEED- SHEAR IS MINIMAL BUT STILL NOTE TYPICAL STRONG VEERING OF THE PROFILE IN THE LOWEST LEVELS AHEAD OF THE FRONT. THEREFORE... THUNDER WILL STILL BE INCLUDED IN THE FORECAST FOR TUE AFTERNOON...BUT SEVERE POTENTIAL WILL BE MAINLY DEPENDENT ON SHEAR...WHICH IS BETTER FURTHER N...BUT NON-ZERO HERE. TEMPS WILL BE DICTATED BY CLOUD COVER...BUT WILL LIKELY SEE MID-UPPER 80S WHERE ANY SUNNY BREAKS ARE OBSERVED. WED...AFTER A BRIEF PERIOD WITHIN THE WARM SECTOR...A COLD FRONT WILL BE SLOWLY CROSSING THE REGION BY DAY ON WED. HOW MUCH INSTABILITY IS AVAILABLE WILL DEPEND UPON HOW DEEP IN THE WARM SECTOR WE GET AND HOW MANY BREAKS OF SUN ARE ALLOWED BEFORE THE FRONT ARRIVES /LOOKS LIKE AROUND MID DAY/. SFC DWPT/TEMPS PROMOTE A BIT MORE POTENTIAL FOR CAPE VALUES TO EXCEED 1000 J/KG BUT ONCE AGAIN SHEAR IS A LIMITING FACTOR. PWATS ARE HIGH...ABOUT 2.0 INCHES OR 2 STD DEVIATIONS ABOVE NORMAL. THEREFORE...AGREE WITH PREVIOUS FORECASTERS ASSESSMENT OF HEAVY RAIN BEING THE MOST LIKELY THREAT. WILL CONTINUE TO INCLUDE THIS IN THE HWO. THU AND FRI...UNCERTAINTY PEAKS DURING THIS PERIOD PRIMARILY DUE TO THE STALLING FRONTAL BOUNDARY OFF THE S COAST AS ZONAL STEERING FLOW BEGINS TO PARALLEL. THIS ZONAL FLOW WILL ALSO FEATURE SEVERAL WEAK SHORTWAVES LEAVING THE CONFINES OF A STRONG VORTEX TO THE NW. THEREFORE...DEPENDING ON HOW CLOSE THIS WAVE STAYS...PERIODIC SHOWERY WEATHER IS LIKELY FOR THE END OF THE WEEK. STUDIES ALSO SUGGEST THIS IS A GOOD CONDUIT FOR UPSTREAM MCS DEVELOPMENT WHICH WILL NEED TO BE MONITORED. NOT A TRUE RING-OF- FIRE HERE...BUT ANY REMNANTS OF UPSTREAM CONVECTION WILL CERTAINLY NEED TO BE WATCHED. IN ANY CASE...NOT A WASHOUT HERE AS THERE IS LIKELY TO BE SOME DRY PERIODS AS WELL. TEMPS ARE LIKELY TO BE NEAR OR SLIGHTLY ABOVE NORMAL...AS H85 TEMPS ARE IN THE +12C TO +14C RANGE AS AN ENSEMBLE MEAN. NEXT WEEKEND...THERE ARE A COUPLE OF DIFFERENT CAMPS TO FOLLOW. WITH THE ROBUST VORTEX ELONGATED AND SHIFTING E...RIDGING IS EXPECTED TO BUILD AHEAD....WHICH COULD PROVIDE ENOUGH OF A BLOCK TO YIELD MAINLY DRY CONDITIONS. HOWEVER...THE APPROACH OF THIS VORTEX COULD ALSO SIGNIFY CONTINUING THE UNSETTLED PATTERN WITH COOLING UPPER LVL TEMPS AND INCREASED MOISTURE. FEEL THAT LOW END POPS WILL COVER THE SPREAD FOR NOW...BUT WITH ENSEMBLES IN BOTH CAMPS HAVE A HARD TIME GOING WITH ANY ONE SOLUTION AT THIS TIME.
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&& .AVIATION /08Z SUNDAY THROUGH THURSDAY/...
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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 MONDAY/... HIGH CONFIDENCE VFR MOST OF THE TIME. WEAK PRESSURE GRADIENT WILL LEAD TO SEA BREEZE DEVELOPMENT BOTH TODAY AND MONDAY. PATCHY IFR IN FOG TONIGHT...MAINLY IN THE CT RIVER VALLEY OF MA. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/... MON NIGHT INTO WED...MODERATE CONFIDENCE. A SERIES OF FRONTS WILL CROSS THE WATER...WITH THE THREAT FOR DAYTIME THUNDERSTORMS AND NIGHTTIME FOG. S WINDS SHOULD REMAIN BELOW SCA THRESHOLDS...AS SHOULD SEAS. THU...MODERATE CONFIDENCE. A FRONT WILL STALL NEAR THE SOUTH COAST. WHILE PERIODIC SHOWERS AND FOG ARE LIKELY...THERE MAY BE A BUILDING SWELL REACHING NEAR SMALL CRAFT ADVISORY THRESHOLDS. HOWEVER...THIS IS UNCERTAIN AT THIS TIME.
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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. HIGH CONFIDENCE THROUGH MONDAY. LATEST MODEL WAVE GUIDANCE IS TOO HIGH COMPARED TO LATEST OBSERVATIONS. WOUND UP SUBTRACTING 1 FOOT FROM THE FORECAST GUIDANCE. NO LONGER EXPECTING SEAS TO REACH 5 FT THROUGH MONDAY. WITH WEAK WINDS ALREADY IN PLACE. CANCELED THE SMALL CRAFT ADVISORY FOR THE SOUTHERN OUTER COASTAL WATERS. OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/... MON NIGHT THROUGH WED...MODERATE CONFIDENCE. A SERIES OF FRONTS WILL MOVE ACROSS THE AREA TUE AND WED. THIS WILL LEAD TO SHOWERS AND THUNDERSTORMS POSSIBLE BY DAY...AND FOG BY NIGHT. THEREFORE... VFR BY DAY WITH PERIODIC MVFR/IFR IN SHOWERS/STORMS. WITH THE POSSIBILITY MVFR/IFR IN FOG AT NIGHT. THU...MODERATE CONFIDENCE. TRANSITIONING TO MORE WIDESPREAD VFR. BUT SHOWERS WILL LINGER.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. RI...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...BELK/DOODY NEAR TERM...BELK SHORT TERM...BELK LONG TERM...DOODY AVIATION...BELK/DOODY MARINE...BELK/DOODY

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