Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 280630 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 230 AM EDT THU AUG 28 2014 .SYNOPSIS... A COLD FRONT MOVES OFFSHORE THIS MORNING. HIGH PRESSURE BUILDS IN WITH DRIER WEATHER AND LESS HUMIDITY FOR TODAY AND FRIDAY. HURRICANE CRISTOBAL WILL PASS WELL OFFSHORE TODAY BRINGING DANGEROUS SURF AND RIP CURRENTS TO SOUTH FACING OCEAN BEACHES OF RI AND MA. PLEASANT WEATHER LINGERS INTO SATURDAY...THEN A FRONT WILL SWEEP ACROSS NEW ENGLAND LATE SUNDAY INTO MONDAY BRINGING UNSETTLED CONDITIONS. && .NEAR TERM /THROUGH TODAY/... THROUGH 8 AM... AT 1 AM THE COLD FRONT WAS OVER SOUTHEAST MASS AND MOVING OFFSHORE. WIDELY SCATTERED SHOWERS LED THE FRONT. THESE WILL MOVE OFFSHORE BY SUNRISE. CLEARING SKIES MOVING INTO WESTERN NEW ENGLAND WILL TREND EAST TO THE COAST BY MORNING. PATCHY FOG LINGERS NEAR NANTUCKET...AND SHOULD LINGER UNTIL FROPA. THE WIND SHIFT SHOULD THEN START MOVING THE FOG OUT TO SEA. TODAY... DRIER AIR AT THE SURFACE BUT A LAYER OF 80 PCT RH LINGERS BETWEEN 800 AND 850 MB. UPPER TROUGH AND COLD POOL MOVE ACROSS NEW ENGLAND...ALTHOUGH MOST OF THIS IS FOCUSSED ON NORTHERN NEW ENGLAND. DAYTIME HEATING IN THE MOSTLY CLEAR SKIES SHOULD REACH 850 MB OR A LITTLE HIGHER...TAPPING THIS MOISTURE AND FORMING DIURNAL CLOUDS LATE MORNING AND AFTERNOON...ESPECIALLY ALONG AND NORTH OF THE MASS PIKE. THE MIXING WILL ALSO TAP A DEEP LAYER OF 20 KNOT NORTHWEST WINDS CREATING GUSTS TO THAT SPEED DURING THE MIDDAY AND AFTERNOON. TEMPS AT THE TOP OF THE MIXED LAYER WILL BE EQUIV TO 10-12C...SUPPORTING MAX SFC TEMPS IN THE MID 70S TO LOWER 80S. WITH DEWPOINTS FALLING INTO THE 50S...THIS WILL MEAN A PLEASANT BREEZY DAY. HURRICANE CRISTOBAL WILL PASS ABOUT 375 MILES SOUTHEAST OF NANTUCKET TODAY. TROPICAL STORM FORCE WINDS ONLY EXTEND ABOUT 205 MILES OUT FROM THE STORM. SWELL ALREADY TRANSMITTED NORTH THROUGH THE OCEAN HAS REACHED OUR WATERS WITH A 13-15 SECOND PERIOD OBSERVED ON BOTH THE SOUTHERN AND EASTERN WATERS...AND A 7 FOOT HEIGHT HAS BEEN OBSERVED AT THE BUOY SOUTHEAST OF BLOCK ISLAND. WAVE MODEL DATA SHOWS A 7-8 FOOT SWELL LINGERING ON OUR SOUTHERN EXPOSED WATERS THROUGH THE DAY AND THEN DIMINISHING TONIGHT. CALCULATIONS SUGGEST BREAKERS OF 6-12 FEET ON SOUTH-FACING OCEAN BEACHES. WE WILL CONTINUE THE HIGH SURF ADVISORY AND EXTEND IT THROUGH EARLY FRIDAY. && .SHORT TERM /TONIGHT THROUGH 6 PM FRIDAY/... TONIGHT...HIGH PRESSURE BUILDS OVER THE REGION AND SHOULD BRING DIMINISHING WIND WITH DECOUPLING IN THE INTERIOR. DEWPOINTS WILL FALL TO 45-55 MOST AREAS. THIS WILL ALLOW TEMPERATURES INLAND TO FALL TO THE UPPER 40S AND 50S. OCEAN INFLUENCE WILL KEEP COASTAL AREAS AROUND 60 OR LOW 60S. FRIDAY... HIGH PRESSURE SURFACE AND ALOFT BUILDS OVERHEAD. THIS WILL MEAN FAIR SKIES AND LIGHT WINDS...AS WELL AS SEABREEZES ALONG THE COASTS. TEMPS ALOFT 8-10C SHOULD SUPPORT MAX TEMPS IN THE 70S. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... */ HIGHLIGHTS... - HOT AND HUMID CONDITIONS THROUGH THE WEEKEND - THUNDERSTORMS POSSIBLE ACROSS N/W NEW ENGLAND SUNDAY - WET WEATHER ANTICIPATED SUNDAY NIGHT INTO MONDAY NIGHT - COULD REMAIN WARMER THAN AVERAGE INTO NEXT WEEK */ OVERVIEW AND MODEL PREFERENCE... BETTER AGREEMENT AMONG ENSEMBLE MEMBERS WOULD SUGGEST A ZONAL FLOW REGIME WITH SOME WEAK RIDGING AS BOTH THE NAO/PNA REMAIN NEGATIVE TO NEAR-NEUTRAL. EXPECTING AN ABOVE AVERAGE TEMPERATURE PATTERN AS THE ECENS/GEFS/NAEFS/CPC WOULD SUGGEST INTO EARLY SEPTEMBER...ANOMALOUS ON THE ORDER OF +2-3 STANDARD DEVIATIONS. WITH ANTICIPATED WARMER CONDITIONS SUBSEQUENT OF RIDGING...EXPECTING PROLONGED S-FLOW TO ADVECT MUGGY CONDITIONS N. LOOKING TO BE A WARM AND HUMID TIMEFRAME. FOR THE FORECAST PERIOD OVER THE NEXT WEEK BEGINNING FRIDAY...EXPECT THE W-ATLANTIC RIDGE TO BE THE DOMINANT INFLUENCE OVER THE REGIONS WEATHER. FAVOR THE ECMWF WITH THE CONFLUENT FLOW SETUP AND ATTENDANT SURFACE FRONTAL POSITION BETWEEN THE NE-CANADA TROUGH AND W-ATLANTIC RIDGE REMAINING N OF THE REGION PARENT WITH BETTER JET-DYNAMICS AND SHEARED MID-LEVEL ENERGY. ONLY AS A C-CONUS DISTURBANCE INVOKES A WEAK-WAVE LOW ALONG THE FRONT WILL WET-WEATHER SHIFT INTO OUR AREA AROUND MONDAY BASED ON A CONSENSUS OF MODEL DATA. DESPITE MODEL VARIANCE...A BROAD SIGNAL IS DISCERNIBLE OF A BRIEF PERIOD OF DRY WEATHER AFTER PASSAGE OF THE WEAK-WAVE LOW...FOLLOWED BY A SHARP COLD FRONT AND PERHAPS THE RETURN OF MORE SEASONABLE CONDITIONS. LOW CONFIDENCE AT THIS TIME AS ENSEMBLE MEANS WOULD SUGGEST THE PROPENSITY FOR ZONAL-FLOW WITH WEAK RIDGING. FAVOR THE DETERMINISTIC ECMWF WITH POSSIBLE OUTCOMES. HIGHLIGHTS/CONFIDENCE ARE BROKEN DOWN IN THE DAILY DISCUSSION BELOW. */ DAY-TO-DAY DETAILS... SATURDAY... SURFACE WARM FRONT LIFTING NE ACROSS NEW ENGLAND LATE...JOINING WITH A TRAILING COLD FRONT FROM A LOW DISTURBANCE OVER NE-CANADA. AS THE RIDGE SUBSEQUENTLY ENHANCES AHEAD OF THE FRONTAL DISTURBANCE AND A WEAKER DISTURBANCE OVER THE C-CONUS...BELIEVE WET-WEATHER ACTIVITY WILL BE PUSHED WELL N OF THE REGION BY THE INFLUENCE OF THE RIDGE. THUS WILL GO WITH A DRY-WEATHER FORECAST. EXPECT PREVAILING S-FLOW TO BEGIN USHERING WARMER / HUMID CONDITIONS ACROSS THE REGION. WILL SEE HIGHS WARM INTO THE LOW-80S AS A WELL- MIXED BOUNDARY LAYER ALLOWS FOR SCATTERED CUMULUS ALONG WITH THE MIX- DOWN OF BREEZY S/SW FLOW. FEEL THIS WILL RESTRICT SEA-BREEZES...SO EXPECT INTERIOR WINDS TO PUSH THE WARM / HUMID CONDITIONS ALL THE WAY TO THE E-SHORES. MILD AND DRY OVERNIGHT. WITH A LINGERING DRY-SUBSIDENCE INVERSION... HIGHER DEWPOINT AIR ADVECTING N COULD LEND TO LOW CLOUDS / FOG ALONG THE S-SHORE. EXPECTING LOWS AROUND THE LOW- TO MID-60S. SUNDAY... WARM-FRONT WELL-DEFINED TO THE N. PUSH OF H85 +16-18C AIR ACROSS THE REGION. EXPECT S NEW ENGLAND TO BE WITHIN THE WARM-SECTOR OF A HOT AND HUMID AIRMASS. COLLOCATED WITHIN A WELL-MIXED BOUNDARY LAYER... BREEZY S/SW-FLOW DURING THE DAY SHOULD ALLOW FOR INTERIOR WINDS ONCE AGAIN TO RESTRICT SEA-BREEZES AND PUSH FORECAST HIGH TEMPERATURES AROUND THE UPPER-80S TO THE E-SHORES. HEIGHTS FALL AS THE C-CONUS DISTURBANCE SHIFTS E WITHIN THE QUASI- ZONAL FLOW REGIME. SHOWERS / THUNDERSTORMS ARE CERTAINLY PLAUSIBLE N AND W WITHIN MODEST INSTABILITY AND SHEAR...CLOSER TO REGIONS OF FAVORABLE DYNAMICS / ASCENT AS WELL AS THE CONVERGENT NOSE OF HIGHER THETA-E AIR AHEAD OF THE FRONT. LIKELY THE MAJORITY OF ACTIVITY IS ACROSS THE E GREAT LAKES INTO NY/PA...BUT ITS POSSIBLE THAT ACTIVITY DEVELOPS INTO N/W NEW ENGLAND LATE. THIS WOULD POSSIBLY BE THE CASE AS THE CONVECTIVE TEMPERATURE IS MET SUCH THAT ANY INVERSION WOULD ERODE AND BOTH SURFACE-BASED INSTABILITY AND EFFECTIVE SHEAR COULD BE UTILIZED. CAN NOT RULE OUT STRONG STORMS...ESPECIALLY ACROSS S/W FACING SLOPES OF HIGH TERRAIN OVER NW CT / W MA / S NH AS OROGRAPHIC PROCESSES AID IN LIFTING THE WARM / JUICY AIRMASS ALOFT. BUT IT IS POSSIBLE THAT THE RIDGE WINS OUT. STILL A FORECAST WAY OUT IN TIME AND AS WE HAVE SEEN JUST IN THE PAST SEVERAL MODEL RUNS THERE HAS BEEN A FAIR AMOUNT OF VARIABILITY. HAVE MODERATE CONFIDENCE WITH THIS FORECAST TIMEFRAME. RIDGE AND SUBSIDENCE INVERSION LINGERS FOR THE S/E SO WILL KEEP WITH A DRY-FORECAST FOR THOSE AREAS. SUNDAY NIGHT THROUGH MONDAY NIGHT... WEAK-WAVE LOW ALONG THE FRONT THROUGH THE QUASI-ZONAL FLOW PUSHES E AND ACROSS THE REGION. THOUGH APPEARING AS A NOCTURNAL PASSAGE...THE COLLOCATION OF DEEP-LAYER MOISTURE...MINOR INSTABILITY AND SHEAR... AND FORCING ALONG THE FRONTAL BOUNDARY WILL LIKELY YIELD WIDESPREAD SHOWERS WITH THE POSSIBILITY OF HEAVY RAIN AND THUNDERSTORMS. THOUGH IT APPEARS THE BETTER FORCING DYNAMICS SHIFT N/E...SHUNTED BY THE RIDGING PATTERN AND BERMUDA HIGH REMAINING DOMINANT. LOW CONFIDENCE FORECAST AS THE CONSENSUS OF MODEL SOLUTIONS CONTAINS A FAIR AMOUNT OF VARIABILITY. WILL PREVAIL WITH SLIGHTLY ABOVE- AVERAGE CONDITIONS. TUESDAY ONWARD... A LULL IN ACTIVITY IS POSSIBLE BEHIND THE WEAK-WAVE DISTURBANCE. A SHARPER COLD FRONT INTO MIDWEEK FOLLOWED BY HIGH PRESSURE. NOT ALL ENTIRELY CONVINCED ON SUCH OUTCOMES BASED ON ENSEMBLE TRENDS. WOULD ANTICIPATE RIDGING TO REMAIN DOMINANT WITH TEMPERATURES BEING ABOVE- AVERAGE FOR THE TIMEFRAME. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /TODAY THROUGH FRIDAY/...HIGH CONFIDENCE. VFR THROUGH THE PERIOD. NORTHWEST WINDS WILL BECOME GUSTY NEAR 20 KNOTS LATE THIS MORNING AND AFTERNOON...THEN DIMINISH TOWARD EVENING. LIGHT WINDS FRIDAY WILL ALLOW SEA BREEZES TO DEVELOP ALONG THE COAST LATE MORNING AND AFTERNOON. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. NORTHWEST WINDS GUST TO 20 KNOTS MIDDAY AND AFTERNOON. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...FRIDAY NIGHT THROUGH MONDAY... SATURDAY INTO SUNDAY...MODERATE CONFIDENCE. VFR. BREEZY S/SW WINDS. SCT CIGS 4-6 KFT SATURDAY. 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. CONTINUED S/SW WINDS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /TONIGHT THROUGH THURSDAY/...HIGH CONFIDENCE. TONIGHT... SOUTH SWELLS FROM CRISTOBAL CONTINUE TO INCREASE. A FEW SHOWERS POSSIBLE OVERNIGHT. SSW WINDS BECOME NW TOWARD SUNRISE AS COLD FRONT APPROACHES FROM THE WEST. THURSDAY... SWELLS PEAK AT 5 TO 11 FT TOMORROW ACROSS THE SOUTH COAST WATERS. ADDING TO THE ROUGH SEAS WILL BE A DEVELOPING NW WIND WAVE BEHIND THE FRONTAL PASSAGE. OTHERWISE DRY WEATHER WITH GOOD VSBY. HOWEVER A FEW SHOWERS MAY LINGER EARLY IN THE MORNING ACROSS THE SOUTH COASTAL WATERS. THURSDAY NIGHT... NW WINDS BECOME N-NE LATE. GOOD VSBY AND DRY WEATHER. OUTLOOK...FRIDAY THROUGH MONDAY... FRIDAY...HIGH CONFIDENCE. HIGH PRESSURE IN CONTROL. LIGHT WINDS. DIMINISHING SEAS WITH ONLY THE S/SE OUTER WATERS EXPERIENCING WAVE HEIGHTS IN EXCESS OF 5-FEET BY MORNING. GOOD BOATING WEATHER. SATURDAY INTO SUNDAY...MODERATE CONFIDENCE. INCREASING S-WINDS. PROLONGED S-FETCH LENDING TO WAVE HEIGHTS IN EXCESS OF 5-FEET ACROSS THE S/SE WATERS. FOG POSSIBLE DURING THE OVERNIGHT HOURS...ESPECIALLY ALONG THE S-COAST. MONDAY...MODERATE CONFIDENCE. CONTINUED S-WINDS. WET-WEATHER MOVING ACROSS THE WATERS. FOG MAY REMAIN AN ISSUE OVER THE WATERS...ESPECIALLY DURING OVERNIGHT PERIODS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...HIGH SURF ADVISORY UNTIL 8 PM EDT THIS EVENING FOR MAZ020- 022>024. NH...NONE. RI...HIGH SURF ADVISORY UNTIL 8 PM EDT THIS EVENING FOR RIZ006>008. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT FRIDAY FOR ANZ235-237-254>256. && $$ SYNOPSIS...WTB/SIPPRELL NEAR TERM...WTB/SIPPRELL SHORT TERM...WTB LONG TERM...SIPPRELL AVIATION...WTB/SIPPRELL MARINE...NOCERA/SIPPRELL

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