Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 272019 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 419 PM EDT WED AUG 27 2014 .SYNOPSIS... A COLD FRONT APPROACHING THE REGION WILL TRIGGER A FEW SHOWERS AND THUNDERSTORMS THIS EVENING AND OVERNIGHT. THE FRONT MOVES OFFSHORE EARLY THU MORNING WITH DRIER AND LESS HUMID AIR OVERSPREADING SOUTHERN NEW ENGLAND THU AND FRI...YIELDING MILD DAYS AND COOL NIGHTS. HURRICANE CRISTOBAL WILL PASS WELL OFFSHORE LATE TONIGHT INTO THURSDAY...BUT WILL BRING DANGEROUS SURF AND RIP CURRENTS TO SOUTH FACING OCEAN BEACHES OF RI AND MA. PLEASANT WEATHER LINGERS INTO SAT...THEN A FRONT MAY STALL ACROSS NEW ENGLAND SUN INTO MON BRINGING UNSETTLED CONDITIONS. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 4 PM UPDATE... LATEST RUNS OF NAM...12Z ECMWF ALONG WITH HRRR AND RAP13 HAVE BEEN TRENDING TOWARD LESS CONVECTIVE QPF THIS EVENING AND OVERNIGHT. DESPITE MODEST INSTABILITY BEING OBSERVED ON SPC MESOANALYSIS OF 1000-1500 J/KG FROM CENTRAL MA WESTWARD INTO EASTERN NY...THE LACK OF SHEAR AND SURFACE CONVERGENCE IS KEEPING CONVECTION ISOLATED TO WIDELY SCATTERED SO FAR. GIVEN THE ARRIVAL OF THE MID LEVEL TROUGH AND ASSOCIATED DEEP LAYER SHEAR IS AFTER PEAK HEATING /00Z- 06Z/...NOT EXPECTING MUCH IF ANY SEVERE STORMS. HOWEVER CAN/T COMPLETELY RULE OUT AN ISOLATED STRONG STORM OVER WESTERN CT/MA WITH GUSTY WINDS GIVEN INVERTED / SOUNDING SIGNATURE AND BRIEF HEAVY RAIN WITH PWATS UP TO 1.7 INCHES OVER THE LOWER HUDSON VALLEY. CONVECTION WILL WEAKEN AFTER 00Z GIVEN BOUNDARY LAYER COOLING AND WEAK MID LEVEL LAPSE RATES. HOWEVER MODEST SYNOPTIC SCALE FORCING FOR ASCENT AND INCREASING DEEP LAYER SHEAR MAY BE SUFFICIENT FOR A BROKEN LINE OF SHOWERS TO TRAVERSE TO THE COAST LATER THIS EVENING. GIVEN THE LATER TROUGH ARRIVAL COLD FRONTAL PASSAGE NOT EXPECTED TO CLEAR OUR REGION UNTIL OVERNIGHT AND PROBABLY NOT UNTIL SUNRISE FOR THE SOUTH COAST INCLUDING CAPE COD AND THE ISLANDS. THUS ANOTHER WARM NIGHT. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... 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. THU 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. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... */ 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 DISCERNABLE 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-FROECAST 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 /20Z WEDNESDAY THROUGH MONDAY/... 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. THRU 00Z...ANY -TSRA NOT FIRING UNTIL 20Z/21Z WESTERN NEW ENGLAND WITH CHANCES FARTHER EAST FADING TOWARD 00Z. ACTIVITY WILL BE ISOLATED OR WIDELY SCATTERED. VFR PREVAILS WITH LOW RISK OF BRIEF MVFR IN -TSRA. AFTER 00Z...ISOLATED TO WIDELY SCATTERED SHOWERS TIL 06Z THEN MOVING OFFSHORE WITH FRONTAL PASSAGE AND WIND SHIFT FROM SW TO NW 06Z-12Z FROM NW TO SE. VFR PREVAILS WITH BRIEF MVFR POSSIBLE IN ANY HEAVIER SHOWERS. LOW RISK OF BRIEF IFR SOUTH COAST UNTIL FRONTAL PASSAGE 06Z-12Z. THURSDAY...VFR. NORTHWEST WINDS MAY GUST TO 20 KNOTS WITH SCATTERED TO BROKEN SKY COVER AROUND 5000 FEET FROM MIDDAY TO EVENING. THU NIGHT...VFR AND DRY WITH A MODEST NW WIND 10-20 KT DIMINISHING TOWARD MORNING. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. ISOLATED -SHRA/-TSRA 22Z- 04Z POSSIBLE. GIVEN LIMITED AREAL COVERAGE DECIDED NOT TO INCLUDE VCTS AND JUST GO WITH VCSH...THE HIGHER PROBABILITY. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. ISOLATED -SHRA/-TSRA 21Z-03Z. GIVEN LIMITED AREAL COVERAGE DECIDED NOT TO INCLUDE VCTS AND JUST GO WITH VCSH...THE HIGHER PROBABILITY. OUTLOOK...FRI 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. && .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 THIS EVENING AND OVERNIGHT. SSW WINDS BECOME NW TOWARD SUNRISE AS COLD FRONT APPROACHES FROM THE WEST. THU... 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 MORNIGN ACROSS THE SOUTH COASTAL WATERS. THU 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...AIR QUALITY ALERT UNTIL 9 PM EDT THIS EVENING FOR CTZ002>004. MA...HIGH SURF ADVISORY FROM 8 PM THIS EVENING TO 8 PM EDT THURSDAY FOR MAZ020-022>024. NH...NONE. RI...HIGH SURF ADVISORY FROM 8 PM THIS EVENING TO 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. && $$ SYNOPSIS...NOCERA/SIPPRELL NEAR TERM...NOCERA SHORT TERM...NOCERA LONG TERM...SIPPRELL AVIATION...NOCERA/SIPPRELL MARINE...NOCERA/SIPPRELL

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.