Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 290658 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 258 AM EDT FRI AUG 29 2014 .SYNOPSIS... HIGH PRESSURE CENTERED OVER THE GREAT LAKES WILL BUILD OVER NEW ENGLAND WITH DRY WEATHER AND LOW HUMIDITY TODAY AND SATURDAY. ROUGH SURF AND RIP CURRENTS WILL DIMINISH BY TONIGHT. A FRONT WILL SLOWLY MOVE ACROSS NEW ENGLAND LATE SUNDAY AND MONDAY BRINGING SCATTERED SHOWERS AND THUNDERSTORMS. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... HIGH PRESSURE BUILDS OVER NEW ENGLAND AT THE SURFACE AND ALOFT WHILE YESTERDAY/S UPPER TROUGH MOVES OFF THROUGH THE MARITIMES. WHILE THERE WILL BE SOME LINGERING PRESSURE GRADIENT THIS MORNING...THIS SHOULD BECOME LIGHT AS THE HIGH MOVES OVERHEAD. THE LIGHT GRADIENT WILL ALLOW FOR SEA BREEZES DEVELOPING LATER THIS MORNING AND THIS AFTERNOON ALONG ALL COASTLINES. CROSS SECTIONS OF RELATIVE HUMIDITY SHOW A LAYER OF HIGH MOISTURE ALSO LINGERING BETWEEN 800 AND 850 MB. MIXING WILL REACH TO AT LEAST THE BASE OF THAT LAYER. EXPECT ANOTHER ROUND OF DIURNAL CUMULUS...BUT WITH INCREASING SUBSIDENCE THE SKY COVER SHOULD BE LESS THAN YESTERDAY. TEMPS AT 850 MB WILL BE 8-10C WHICH SUPPORTS MAX SFC TEMPS IN THE 70S...POSSIBLY NEAR 80 IN A FEW WARM SPOTS SUCH AS THE LOWER CT VALLEY. SEA BREEZES WILL BUFFER COASTAL TEMPS...WATER TEMPS ARE IN THE 60S EAST OF MASS AND AROUND 70 ALONG THE SOUTH COAST. SO COASTAL TEMPS SHOULD BE IN THE 60S AND LOWER 70S. A 5 FOOT SOUTH SWELL LINGERS ON THE SOUTHERN WATERS THIS MORNING...BUT SHOULD BE TRENDING LOWER THROUGH THE DAY. WE WILL CONTINUE THE HIGH SURF ADVISORY THROUGH THE MORNING BUT BRING THE ENDING TIME FORWARD TO 2 PM. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... HIGH PRESSURE MOVES OFFSHORE TONIGHT AND REMAINS IN PLACE TO OUR EAST ON SATURDAY. THIS WILL BRING INCREASING FLOW FROM THE SOUTH...EXCEPT SOUTHEAST NEAR THE EAST MASS COAST. DEW POINTS WILL START TO RISE...BUT THIS TREND MAY HOLD OFF UNTIL THE FLOW PICKS UP ON SATURDAY. AT THAT POINT...DEW POINT VALUES WILL CLIMB THROUGH THE 50S TO NEAR 60 BY SATURDAY EVENING. TONIGHT... THE LIGHT WIND/FAIR SKIES WILL ALLOW ANOTHER COOL NIGHT TONIGHT WITH SURFACE TEMPS IN THE UPPER 40S AND 50S. THIS WILL BE CLOSE ENOUGH TO SATURATION FOR PATCHY FOG. BEST CHANCES WOULD BE IN THE CT VALLEY AND IN THE LOW SPOTS OF EASTERN MASS. SATURDAY... SUNSHINE THROUGH CIRRUS ON SATURDAY WILL MEAN A PLEASANT DAY. THE SUNSHINE WILL BE FILTERED A LITTLE...BUT TEMPS IN THE MIXED LAYER WILL BE A LITTLE MILDER THAN TODAY. SO SFC TEMPS SHOULD BE AT LEAST THE SAME AS TODAY AND PROBABLY A LITTLE MILDER. BASED ON A MIXED LAYER TO 900 MB OR A LITTLE ABOVE...WE WENT WITH MAX TEMPS 75 TO 80. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... */ HIGHLIGHTS... - HOT AND HUMID WEEKEND - BEST CHANCE OF WET-WEATHER LATE SUNDAY INTO MONDAY - COLD FRONT ACROSS THE REGION TUESDAY - DRY AND SEASONABLE FORECAST FOR THE REST OF THE WEEK */ OVERVIEW AND MODEL PREFERENCE... NOTING ENSEMBLE SIGNALS OF A NEGATIVE TO NEAR-NEUTRAL NAO AND PNA PATTERN...PREFER A ZONAL FLOW WITH HIGHER HEIGHTS AND WEAK RIDGING ACROSS THE NE-CONUS INTO EARLY SEPTEMBER. BROADLY SPEAKING OVER THE LONG-TERM FORECAST PERIOD...AM EXPECTING SEASONABLE TO ABOVE-AVERAGE TEMPERATURES AND MUGGIER CONDITIONS. LIKELY THERE WILL BE PERIODS IN WHERE MORE REFRESHING AIR WILL DIVE S OUT OF CANADA...YET AVERAGING OVER THE FORECAST PERIOD WILL LIKELY YIELD ANOMALOUSLY HIGHER VALUES OF TEMPERATURE AND MOISTURE AS HINTED BY ENSEMBLE MEMBERS. BUT ALSO ANTICIPATE A SUBDUED WEATHER PATTERN. ANY PACIFIC ENERGY TROUGHING ACROSS W N-AMERICA SHOULD BE KEPT WELL N OF THE REGION IF NOT STRETCHED THROUGH THE CONFLUENT ZONAL-FLOW PATTERN...AGAIN N OF THE REGION. WHILE CONVECTIVE PERIODS ARE EXPECTED...STRETCHED MID- LEVEL IMPULSES AND LESS AMPLIFIED PATTERN SHOULD YIELD LIMITATIONS IN CONVECTIVE SEVERITY...AS WELL AS KEEP CONVECTIVE EPISODES MAINLY CONFINED DURING THE DAYTIME PERIODS...DIFFUSING OVERNIGHT...HEAT AND MOISTURE BEING THE MAIN FUEL TO THE FIRE. HAVE HIGH PRAISE FOR THE ECMWF / ECENS WHICH HAS REMAINED FAIRLY CONSISTENT RUN-TO-RUN OVER THE PAST THREE DAYS. THOUGH NOT IGNORING OUTCOMES FROM OTHER MODEL SOLUTIONS...WILL PLACE GREATER WEIGHT ON THE ECMWF / ECENS TOWARDS THE FORECAST. HIGHLIGHTS/CONFIDENCE ARE BROKEN DOWN IN THE DAILY DISCUSSION BELOW. */ DAY-TO-DAY DETAILS... SATURDAY NIGHT... QUIET UNDER LIGHT S-FLOW. INCREASING SURFACE MOISTURE. SOME QUESTION AS TO WHETHER LOW CLOUDS SEEP IN FROM THE S OR RATHER MORE CLEAR CONDITIONS ALLOW FOR THE DEVELOPMENT OF PATCHY FOG...OR A COMBINATION OF BOTH. DRIZZLE POSSIBLE WITH INCREASING MOISTURE CONTENT UNDERGOING WEAK UPSLOPE? COULD NOT RULE IT OUT ALONG THE S- SHORE. MILD NIGHT WITH LOWS AROUND THE MID-60S. SUNDAY... A BUILDING CONVECTIVE ENVIRONMENT. FALLING HEIGHTS IN A REGION OF MID-LEVEL ASCENT PER DIFFERENTIAL VORTICITY ADVECTION WITHIN DECENT H85-7 LAPSE RATES...ABOVE COLLOCATED LOW-LEVEL MOIST-INSTABILITY AXES INTO THE LOWER HUDSON VALLEY / SW NEW ENGLAND. WHILE BETTER LOW- LEVEL WIND PROFILES / FRONTOGENESIS / H3 JET DYNAMICS RESIDES N AND W...SIGNALS OF MID-LEVEL MOIST-CONVERGENCE IN AN AREA OF FAVORABLE ASCENT SHOULD YIELD SOME ACTIVITY. MODEST INSTABILITY AND 0-6 KM BULK SHEAR. ALSO WOULD EXPECT OROGRAPHIC LIFT ALONG S/W-SLOPES OF HIGH TERRAIN AIDING WITH ASCENT. EXPECT CONVECTION TO DEVELOP N/W SLIDING SE WITH TIME. NO CONFIDENCE AS TO SPECIFICS NOR STORM SEVERITY...BUT DO EXPECT THE BRUNT OF IT TO REMAIN N/W OF THE FORECAST REGION PARENT WITH BETTER DYNAMICS. WHILE A WARM-SECTOR IS EXPECT THROUGH THE INTERIOR WITH HIGHS INTO THE UPPER-80S...CLOUDS MAY BE A HINDERANCE ALONG THE S/SE COASTLINE ESPECIALLY DURING THE MORNING PERIOD...HOPEFULLY ERODING WITH AN INCREASE IN SW-WINDS...BLUSTERY AT TIMES. SUNDAY NIGHT... WITH DAYTIME HEATING CONCLUDING AND THE BULK OF MID-LEVEL ENERGY STRETCHED / SHEARED TO THE N...EXPECT ACTIVITY TO WEAKEN SE WITH TIME. APPROACHING SURFACE FRONTAL BOUNDARY BECOMING DIFFUSE AGAINST THE DOMINANT W-ATLANTIC RIDGE. YET BETTER LOW-LEVEL MOISTURE ALONG WITH COLLOCATED MID-LEVEL LAPSE RATES AHEAD OF THE FRONT SHOULD YIELD SOME ASCENT TO ALLOW SCATTERED SHOWERY WEATHER TO CONTINUE. ABUNDANCE OF CLOUDS AND MOISTURE UNDER SW-FLOW...A VERY MILD NIGHT WITH LOWS DOWN TO AROUND THE UPPER-60S. MONDAY INTO MONDAY NIGHT... COOLER AIR DIGGING SE INTO THE NE-CONUS YIELDING CONDITIONALLY UNSTABLE MID-LEVEL PROFILES ABOVE A WELL-MIXED BOUNDARY LAYER... SHOULD SEE SUBSEQUENT DAYTIME LIFT OF AVAILABLE MOISTURE YIELDING SCATTERED SHOWERS MAYBE EVEN A THUNDERSTORM. MINOR INSTABILITY AND WEAK SHEAR...ANY STORMS WOULD APPEAR TO BE AIRMASS RELATED BENEATH THE WEAK COLD POOL. BEST ACTIVITY MAY OCCUR ACROSS HIGH TERRAIN WITH W-WINDS UNDERGOING OROGRAPHIC LIFT PROVIDING FAVORABLE ASCENT. OTHERWISE SCATTERED TO BROKEN CUMULUS. MILD DAY WITH HIGHS AROUND THE LOW-80S. TURNING QUIET AND COOLER OVERNIGHT AS HIGH PRESSURE IS ANTICIPATED TO SETTLE ACROSS THE REGION. LIGHT WINDS AND MOSTLY CLEAR CONDITIONS MAY ALLOW FOR EFFECTIVE RADIATIONAL COOLING. TUESDAY... EXPECTING A COLD FRONT TO PUSH INTO THE REGION AHEAD OF WHICH MODEST INSTABILITY / WEAK SHEAR COLLOCATED WITH A SW-PLUME OF HIGH MOISTURE RESIDES OVER S NEW ENGLAND. ONCE AGAIN...WITH BETTER DYNAMICS N/W OF THE REGION...ANTICIPATE TRAILING SCATTERED SHOWERS AND THUNDERSTORMS OVER THE FORECAST AREA. ZONAL-FLOW AND WEAK RIDGING SHOULD SUPPRESS ACTIVITY TO SOME DEGREE IN ADDITION TO THE LACKING DYNAMICS... POTENTIALLY DIFFUSE MORE SO SHOULD THE FRONT SWEEP THE REGION DURING THE EVENING PERIOD. HIGHS AGAIN AROUND THE LOW-80S WITH A MILD NIGHT WITH LOWS AROUND THE MID-60S. WEDNESDAY INTO FRIDAY... FAVOR THE ECMWF WITH THE ZONAL-FLOW PATTERN OF HIGHER HEIGHTS. SHALL PREVAIL WITH HIGH PRESSURE. EXPECTING CONDITIONS AROUND SEASONABLE LEVELS AND OVERNIGHT PERIODS WHICH MAY TURN COOL WITH EFFECTIVE RADIATIONAL COOLING AT TIMES UNDER LIGHT WINDS. WEAK IMPULSES THROUGH THE ZONAL FLOW WILL NEED TO BE MONITORED FOR THE POTENTIAL OF LIKELY CLOUDS AND POSSIBLE SHOWERS...BUT SO LATE IN THE FORECAST PERIOD...JUST TOO DIFFICULT TO SUGGEST OUTCOMES. && .AVIATION /07Z FRIDAY THROUGH TUESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /TODAY THROUGH SATURDAY/...HIGH CONFIDENCE. VFR. PATCHY IFR FOG POSSIBLE ACROSS THE CT-RIVER VALLEY EARLY THIS MORNING. PATCHY IFR FOG AGAIN LATER TONIGHT/EARLY SATURDAY IN THE CT VALLEY AND IN THE LOW SPOTS OF EASTERN MASSACHUSETTS. LIGHT WINDS LATE THIS MORNING AND AFTERNOON WILL ALLOW SEA BREEZES TO DEVELOP ALL COASTS. THIS WILL DIMINISH TOWARD EVENING. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. SEA BREEZES DEVELOP INITIALLY TURNING NORTHEAST LATE MORNING...THEN SOUTHEAST BY MID AFTERNOON AND SOUTH AT SUNSET. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...SATURDAY NIGHT THROUGH TUESDAY... SATURDAY NIGHT INTO SUNDAY...MODERATE CONFIDENCE. VFR. BREEZY S/SW WINDS. MVFR-IFR CIGS / VSBYS POSSIBLE ALONG THE S-COAST SATURDAY NIGHT. SHRA/TSRA POSSIBLE FOR N/W NEW ENGLAND LATE SUNDAY. SUNDAY NIGHT INTO MONDAY...LOW CONFIDENCE. MIX OF LOW-END VFR TO MVFR. WIDESPREAD SHRA ACROSS THE TERMINALS. POSSIBLE TSRA ACROSS THE INTERIOR MONDAY. CONTINUED S/SW WINDS. TUESDAY...MODERATE CONFIDENCE. COLD FRONT SWEEPING ACROSS THE TERMINALS. LOW-END VFR. CHANCE OF SHRA/TSRA ACROSS THE INTERIOR. WINDS BACKING OUT OF W BEHIND THE FRONT. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /TONIGHT THROUGH FRIDAY NIGHT/...HIGH CONFIDENCE. TODAY...HIGH PRESSURE BUILDS OVER THE WATERS. THIS MEANS NORTH WINDS WILL DIMINISH AND BECOME LIGHT. LIGHT WINDS WILL ALLOW SEA BREEZES TO DEVELOP NEAR SHORE. A 5 FOOT SOUTH SWELL FROM CRISTOBAL LINGERS ON THE EXPOSED WATERS BUT IS SHOWING A LOWERING TREND. WE WILL CONTINUE THE SMALL CRAFT ADVISORY FOR A FEW MORE HOURS...ENDING IT ON THE SOUNDS BY 8 AM...AND ON ALL OUTER WATERS BY 2 PM. TONIGHT...SEAS WILL BE BELOW 5 FEET AND WINDS LIGHT. SATURDAY...WINDS INCREASE FROM THE SOUTH...BUT SEA WILL REMAIN BELOW 5 FEET. OUTLOOK...SATURDAY NIGHT THROUGH TUESDAY... SATURDAY NIGHT INTO SUNDAY...MODERATE CONFIDENCE. INCREASING S/SW-WINDS. PROLONGED FETCH LENDING TO WAVE HEIGHTS IN EXCESS OF 5-FEET ACROSS THE S/SE WATERS ON SUNDAY. FOG POSSIBLE DURING THE OVERNIGHT HOURS...ESPECIALLY ALONG THE S-COAST. SUNDAY NIGHT INTO MONDAY...MODERATE CONFIDENCE. BREEZY S/SW WINDS CONTINUING. SEAS OF 5-FEET ON THE S/SW WATERS. SHOWERS IMPACTING THE WATERS. PATCHY DENSE FOG POSSIBLE DURING THE OVERNIGHT PERIOD...BUT WITH BRISK WINDS...HAVE GREATER CONFIDENCE TOWARDS LOW CLOUDS. WET WEATHER CLEARING OUT LATE IN THE DAY ON MONDAY. TUESDAY...MODERATE CONFIDENCE. EXPECTING A PERIOD OF QUIET WEATHER OVER THE WATERS WITH BREEZY S- WINDS AHEAD OF A COLD FRONT EXPECTING TO SWEEP THE WATERS TOWARDS WEDNESDAY MORNING. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...HIGH SURF ADVISORY UNTIL 8 AM EDT THIS MORNING FOR MAZ020-023. HIGH SURF ADVISORY UNTIL 4 PM EDT THIS AFTERNOON FOR MAZ022- 024. NH...NONE. RI...HIGH SURF ADVISORY UNTIL 8 AM EDT THIS MORNING FOR RIZ006>008. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 AM EDT THIS MORNING FOR ANZ235-237. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 AM EDT THIS MORNING FOR ANZ250. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM EDT THIS AFTERNOON FOR ANZ254>256. && $$ SYNOPSIS...WTB/SIPPRELL NEAR TERM...WTB/SIPPRELL SHORT TERM...WTB LONG TERM...SIPPRELL AVIATION...WTB/SIPPRELL MARINE...WTB/SIPPRELL

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