Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 272322 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 722 PM EDT WED AUG 27 2014 .SYNOPSIS...
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SHOWERS AND THUNDERSTORMS AHEAD OF A COLD FRONT WILL CONTINUE TO SWEEP ACROSS SOUTHERN NEW ENGLAND OVERNIGHT. DRIER AND LESS HUMID AIR OVERSPREADS THE REGION THURSDAY AND FRIDAY YIELDING MILD DAYS AND COOL NIGHTS. HURRICANE CRISTOBAL WILL PASS WELL OFFSHORE LATE TONIGHT INTO THURSDAY 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.
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&& .NEAR TERM /THROUGH THURSDAY/...
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730 PM UPDATE... LINE OF SHOWERS / THUNDERSTORMS DIMINISHING AS IT PROGRESSES SE ENCOUNTERING A LESS UNSTABLE AIRMASS. WITHIN AN ENVIRONMENT OF LESS FAVORABLE SHEAR...MAIN THREATS WITH ANY STORMS WILL BE HEAVY RAIN /PWATS AROUND 1.50-1.75 INCHES/ AND GUSTY WINDS SUBSEQUENT AS NOTED BY THE PREVIOUS FORECASTER BY INVERTED-V SOUNDINGS. FEEL SUCH THREATS WILL ONLY LAST INTO THE EARLY EVENING. THEREAFTER A LINE OF SHOWERS IS EXPECTED TO BE MAINTAINED BY THE MID-LEVEL TROUGH AND ATTENDANT SYNOPTIC SCALE FORCING OF AVAILABLE MOISTURE CONVERGENT ALONG AND AHEAD OF THE PARENT FRONTAL BOUNDARY. FEEL THE LATEST HRRR / RAP FORECAST SOLUTIONS HAVE THE BEST HANDLE ON THE PRESENT SITUATION. HAVE MODELED FORECAST TRENDS ACCORDINGLY. LIKELY LOW CLOUDS AND FOG AHEAD OF THE FRONT WILL IMPACT SE MA THAT INCLUDE CAPE COD AND THE ISLANDS INTO THE MORNING HOURS. LOWS AROUND THE LOW-60S WITH THE WARM SPOTS SE AND COOLEST AREAS NW.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH 6 PM THURSDAY/...
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THURSDAY... POST FRONTAL AIRMASS OVERSPREADS THE REGION AS COLD FRONT DEPARTS THE SOUTH COAST DURING THE EARLY MORNING. MID LEVEL FLOW REMAINS CYCLONIC AS MEAN TROUGH AXIS ALOFT REMAINS OVER NEW ENGLAND. HOWEVER STRONG DRYING THROUGH THE COLUMN WITH NEGATIVE K-INDICES OVERSPREADING THE REGION ALONG WITH DEW PTS TUMBLING INTO THE 50S AND POSSIBLY THE U40S. HOWEVER GIVEN THE COOL TEMPS ALOFT AND CYCLONIC FLOW SHOULD SEE SCT-BKN CU/SCU DURING THE PEAK HEATING HOURS OF THE AFTERNOON. NEVERTHELESS A SPECTULAR DAY WITH LOW HUMIDITY...A REFRESHING NW BREEZE OF 10 TO 20 MPH AND TEMPS NOTICEABLY COOLER WITH HIGHS 75 TO 80. HIGH SURF.... HURRICANE CRISTOBAL PASSES WELL OFFSHORE BUT WNA AND THE HURRICANE VERSION OF THE WNA YIELDS 5-10 FT SWELLS ENTERING THE NEAR SHORE WATERS AND UP TO 12 FT WELL SOUTH OF MVY AND ACK. OUR IN HOUSE SURF CALCULATION SUGGEST BREAKERS OF 6-12 FT AT SOUTH FACING OCEAN BEACHES TOMORROW. THUS VERY DANGEROUS SURF AND RIP CURRENTS. OBVIOUSLY WILL CONTINUE THE HIGH SURFACE ADVISORY WHICH MAY HAVE TO BE EXTENDED INTO FRI AS THE WAVE MODELS TYPICALLY ERODE SWELL ENERGY TOO QUICKLY. SURF AND RIP CURRENTS WILL NOT BE AS DANGEROUS ALONG THE EASTERN MA COAST AS THE SWELL ENERGY WILL BE PARALLEL TO THIS COASTLINE. THURSDAY NIGHT... CORE OF COOL AIRMASS MOVES OVER THE REGION WITH 850 MB AND 925 MB TEMPS ABOUT +1 SD COOLER THAN NORMAL. N-NE WINDS WILL PRECLUDE EASTERN MA FROM COOLING OFF TOO /L60S/ MUCH GIVEN OCEAN WIND TRAJECTORY. HOWEVER INTERIOR VALLEYS THAT DECOUPLE COULD SEE MINS IN THE MU40S WITH 50S ELSEWHERE.
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&& .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
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*/ HIGHLIGHTS... - SEASONABLE AND DRY WEATHER FOR FRIDAY...ENJOY IT! - 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... FRIDAY... HIGH PRESSURE. LIGHT/VARIABLE WINDS. SEA-BREEZES ALONG THE COASTS. SEASONABLE AND MOSTLY CLEAR CONDITIONS...SLIGHTLY COOLER ALONG THE SHORES...WITH HIGHS AROUND THE MID-70S. MID- TO HIGH-LEVEL CLOUDS POSSIBLE AHEAD OF AN ENCROACHING WARM-FRONT FROM THE SW. ALONG WITH WINDS TURNING S OVERNIGHT AS HIGH PRESSURE SHIFTS E...EXPECT MILDER CONDITIONS WITH LOWS AROUND THE MID-50S. 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.
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&& .AVIATION /00Z THURSDAY THROUGH MONDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /TODAY THROUGH THURSDAY/...MODERATE CONFIDENCE. TSRA CONCLUDING TOWARDS 2Z EVOLVING INTO A SHRA-LINE PROGRESSING SE TOWARDS ACK BY MORNING. VFR REARWARD OF THE LINE UNDER NW WINDS...WITH POSSIBLE IFR-LIFR CIGS / VSBYS ALONG AND AHEAD UNDER S/SW FLOW...ESPECIALLY FOR S-COASTAL TERMINALS. VFR INTO THURSDAY WITH GUSTY NW WINDS UP TO 20 KTS. SCT-BKN CIGS AROUND 5 KFT DURING THE DAY...CLEARING OVERNIGHT WITH WINDS WEAKENING TOWARDS FRIDAY MORNING. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. WILL HOLD VFR WITH SHRA UNTIL 1Z. THEREAFTER...WINDS REVERTING NW AS CIGS LIFT. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. SHRA SHOULD MOVE OUT. NW WINDS AND VFR PREVAIL. CIGS LIFTING. OUTLOOK...FRIDAY THROUGH MONDAY... FRIDAY...HIGH CONFIDENCE. VFR. LIGHT WINDS. SEA-BREEZES ALONG THE SHORES. SKC. 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.
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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. SHORT-TERM /TONIGHT THROUGH THURSDAY/...HIGH CONFIDENCE. TONIGHT... SOUTH SWELLS FROM CRISTOBAL CONTINUE TO INCREASE. A FEW SHOWERS POSSIBLE THIS EVENING AND 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.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...AIR QUALITY ALERT UNTIL 9 PM EDT THIS EVENING FOR CTZ002>004. MA...HIGH SURF ADVISORY UNTIL 8 PM EDT THURSDAY FOR MAZ020-022>024. NH...NONE. RI...HIGH SURF ADVISORY UNTIL 8 PM EDT THURSDAY FOR RIZ006>008. AIR QUALITY ALERT UNTIL 11 PM EDT THIS EVENING FOR RIZ001>005. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT FRIDAY FOR ANZ235-237-254>256.
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&& $$ SYNOPSIS...NOCERA/SIPPRELL NEAR TERM...NOCERA/SIPPRELL SHORT TERM...NOCERA LONG TERM...SIPPRELL AVIATION...NOCERA/SIPPRELL MARINE...NOCERA/SIPPRELL

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