Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 271815 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 215 PM EDT WED AUG 27 2014 .SYNOPSIS...
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HIGH PRESSURE OFFSHORE WILL DRAW WARMER AIR ACROSS NEW ENGLAND TODAY WITH HIGHS AROUND 90 FOR MANY LOCATIONS. A COLD FRONT WILL THEN SWEEP THROUGH DURING THE LATE AFTERNOON AND EARLY NIGHT...BRINGING WIDELY SCATTERED SHOWERS AND THUNDERSTORMS. DRY AND COOLER CONDITIONS RETURN THURSDAY AND FRIDAY BEHIND THE FRONT. HURRICANE CRISTOBAL WILL PASS WELL OFFSHORE LATE TONIGHT INTO THURSDAY MORNING...BUT WILL BRING LARGE SURF AND DANGEROUS RIP CURRENTS TO SOUTH FACING OCEAN BEACHES. A FRONT MAY STALL ACROSS NEW ENGLAND...BRINGING UNSETTLED CONDITIONS SUNDAY INTO EARLY NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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2 PM UPDATE... TEMPERATURES... FINALLY HIT 90 DEGREES AT LOGAN AT 139 PM THIS AFTERNOON. LAST OCCURRENCE WAS 7/23 WHEN IT WAS 92. NOT MUCH CHANGE FROM PREVIOUS FORECAST OTHER THAN INCREASING HIGHS BY A FEW DEGS. A MODEST SW WIND 10 TO 20 MPH IS HELPING TO TAKE THE EDGE OFF THE HEAT ALONG WITH DEW PTS REMAINING BELOW 70. CONVECTION... 12Z NAM ALONG WITH LATEST HRRR AND RAP13 HAVE REALLY BACKED OFF ON CONVECTIVE QPF AND HAVE DIMINISHED THE EASTWARD TREND...KEEPING THE BULK OF ANY ACTIVITY ACROSS WESTERN NEW ENGLAND LATER THIS AFTERNOON AND EVENING. THIS SEEMS REASONABLE GIVEN MARGINAL INSTABILITY /500-1000J-KG/ ALONG WITH DEEP LAYER SHEAR AND JET DYNAMICS ARRIVING 00Z-06Z...WELL AFTER PEAKING HEATING. THIS MAY BE ABLE TO SUSTAIN SOME SHOWERS INTO THE COASTAL PLAIN THIS EVENING BUT THUNDER NOT LIKELY. WORSE CASE SCENARIO REMAINS AN ISOLATED STRONG T-STORM POSSIBLE WESTERN CT/MA WITH BRIEF GUSTY WINDS AND HEAVY DOWNPOURS. HIGH SURF... FIRST SET OF SWELLS /SWELL FRONT/ APPEAR TO BE ON THE EDGE OF ENTERING SOUTHERN NEW ENGLAND WATERS...WITH BUOY 44097 SOUTHEAST OF BLOCK ISLAND NOW REPORTING 4 FT SWELLS EVERY 12 SECONDS. THIS SHOULD RESULT IN SURF BUILDING RAPIDLY LATER THIS AFTERNOON AND ESPECIALLY TOWARD SUNSET AT SOUTH AND SOUTHEAST FACING OCEAN BEACHES.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... TONIGHT... CONSENSUS OF THE MODEL SOLUTIONS BRINGS THE COLD FRONT TO THE COASTAL PLAIN AROUND SUNSET AND OFFSHORE EARLY TONIGHT. EXPECT LINGERING SHOWER/TSTM THROUGH 10 PM IN RI AND EASTERN MASS...AND THROUGH MIDNIGHT CAPE AND ISLANDS. WINDS TURN NORTHWEST BEHIND THE COLD FRONT AND DRAW COOLER DRIER AIR DOWN FROM CANADA. THIS WILL MEAN CLEARING SKIES AND DEW POINTS IN THE 50S AND LOWER 60S. SWELL FROM HURRICANE CRISTOBAL CONTINUES TO INCREASE...WITH 5 FOOT SWELL MOVING INTO OUR SOUTHERN WATERS EARLY TONIGHT. WE HAVE ISSUED A HIGH SURF ADVISORY STARTING TONIGHT. THURSDAY... UPPER SHORTWAVE MOVES ACROSS NEW ENGLAND WITH BRIEF COOLING ALOFT. MOISTURE FIELDS SHOW LINGERING 80 PCT RH VALUES BETWEEN 800 AND 900 MB. THIS SUGGESTS DIURNAL CUMULUS WILL FORM DURING THE DAY. MIXING WILL REACH TO 850 MB WHERE TEMPS OF 10-12C WOULD SUPPORT MAX SFC TEMPS IN THE UPPER 70S AND LOW 80S. WINDS ALOFT WITHIN THE MIXED LAYER ARE FORECAST AT 20 KNOTS...WHICH MAY GET MIXED TO THE SURFACE IN GUSTS. HIGH SURF WILL CONTINUE THROUGH THE DAY AS CRISTOBAL PASSES WELL OFFSHORE. THE HIGH SURFACE ADVISORY WILL CONTINUE THROUGH THE DAY. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... HIGHLIGHTS... * COOL AND DRY WEATHER UNDER HIGH PRESSURE FRIDAY * WARM AND HUMID CONDITIONS INTO THE WEEKEND * SCT SHOWERS/THUNDERSTORMS SUNDAY INTO EARLY NEXT WEEK OVERVIEW AND MODEL PREFERENCES... MEDIUM RANGE MODELS AND THEIR ENSEMBLES ALL CONTINUE TO SIGNAL A LOW AMPLITUDE UPPER LEVEL PATTERN ACROSS THE NORTHERN TIER STATES... WHICH GENERALLY MEANS A FAST MOVING PATTERN IN PLACE. NOTING A DECENT SHORT WAVE DEVELOPING ACROSS THE GREAT LAKES LATE THIS WEEK...THEN PUSHING ALONG IN THE GENERAL W-NW UPPER FLOW TOWARD NEW ENGLAND. A FRONT ALSO TRIES TO SHIFT S...BUT BECOMES PARALLEL TO THIS UPPER FLOW...SO MAY SEE UNSETTLED CONDITIONS MOVE IN FOR SUNDAY AND LABOR DAY. NOTING INCREASING VARIANCE AMONGST THE OP MODEL RUNS EARLY NEXT WEEK IN TRYING TO CLEAR THE SHORT WAVE...WITH POSSIBLY ANOTHER WEAKER ONE MOVING IN. LEANED TOWARD A BLEND OF AVAILABLE MODELS FOR THE EARLY PORTION OF THE FORECAST...WHICH SHOWED GOOD CONTINUITY AND RUN TO RUN CONSISTENCY OVER THE LAST SEVERAL MODEL RUNS...THEN TRENDED TOWARD THE GFS/EC ENSEMBLES BEGINNING SUNDAY THROUGH TUESDAY. DETAILS... THURSDAY NIGHT THROUGH FRIDAY NIGHT... EXPECT DRY AND COOL CONDITIONS AS LARGE HIGH PRES BUILDS OUT OF THE GREAT LAKES...SHIFTING E IN THE BROAD UPPER LEVEL WESTERLY WIND FLOW. WILL MAINLY CLEAR SKIES THU NIGHT AND WINDS BECOMING LIGHT/VRBL MAINLY AFTER MIDNIGHT...TEMPS WILL TUMBLE...WITH READINGS AWAY FROM THE IMMEDIATE COAST AND URBAN CENTERS DROPPING TO THE MID 40S TO AROUND 50. SOME DIURNAL CLOUDS WILL DEVELOP DURING FRIDAY...BUT IT WILL REMAIN COOL WITH HIGHS MAINLY IN THE LOWER-MID 70S. NW WINDS MAY GUST UP TO AROUND 20 KT DURING THE AFTERNOON. CONDITIONS WILL REMAIN DRY FRI NIGHT...BUT THE HIGH WILL CREST ACROSS THE REGION OVERNIGHT. EXPECT SOME MID AND HIGH LEVEL CLOUDS WORKING IN WITH LOWS IN THE 50S. SATURDAY... TRANSITION DAY AS H5 SHORT WAVE MOVES OUT OF THE GREAT LAKES. TEMPS WILL REBOUND AS W-SW WINDS KICK IN...BRINGING IN THE MILDER CONDITIONS WITH INCREASING HUMIDITY ESPECIALLY LATE IN THE DAY INTO SAT NIGHT. A FRONT WILL BEGIN TO SLOWLY SHIFT S OUT OF QUEBEC AND S ONTARIO...SO MAY START TO SEE SOME SHOWERS MOVE INTO WESTERN AREAS SAT NIGHT. CARRIED ONLY LOW CHANCE POPS AT THIS POINT. HIGHS WILL BE IN THE 70S...UP TO AROUND 80 IN THE CT AND MERRIMACK VALLEYS. SUNDAY THROUGH MONDAY... WITH THE HIGH ANCHORED OFF THE MID ATLC AND SE U.S. COAST...ALONG WITH GENERAL W WIND FLOW ALOFT...THE FRONT THAT TRIES TO PUSH S WILL GET HUNG UP IN THIS UPPER FLOW. THE SHORT WAVE WILL MOVE ALONG THE FRONT...SO WILL SEE SCT SHOWERS PUSH ACROSS SUNDAY INTO THE HOLIDAY...WITH BEST SHOT SUNDAY NIGHT AND MON MORNING. DEWPTS ALSO INCREASE. PWATS WILL ALSO INCREASE...ON ORDER OF 1.7 TO 1.8 INCHES /ABOUT +2 SD FOR LATE AUGUST/. SOME MARGINAL INSTABILITY ALSO WORKS IN...SO CAN NOT RULE OUT SOME THUNDERSTORMS. MAY ALSO SEE A FEW PRODUCING LOCALLY HEAVY RAINFALL. TEMPS WILL RISE TO THE UPPER 70S TO MID 80S...MILDEST ON SUNDAY...WITH DEWPTS RISING TO THE MID 60S BOTH DAYS. TUESDAY... SOME QUESTION AS TO TIMING OF EXIT OF PRECIP...AND WHETHER ANOTHER SHORT WAVE DEVELOPS AND PUSHES TOWARD THE REGION. FOR NOW...EXPECT MAINLY DRY BUT WARM CONDITIONS...BUT NOT A LOT OF CONFIDENCE FOR THIS PORTION OF THE FORECAST. && .AVIATION /18Z WEDNESDAY 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. 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 SUNDAY... FRIDAY...HIGH CONFIDENCE. VFR WITH SKC THURSDAY NIGHT INTO FRIDAY. LIGHT WINDS. PATCHY FOG AFTER 06Z FRI WITH LOCAL MVFR TO IFR CONDITIONS POSSIBLE IN NORMALLY PRONE AREAS. SEA BREEZES FRIDAY. SATURDAY INTO SUNDAY...MODERATE CONFIDENCE. VFR. INCREASING S-SW WINDS. BETTER CHANCES FOR SHRA/TSRA SUNDAY ACROSS THE INTERIOR.
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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 /TODAY THROUGH THURSDAY/...HIGH CONFIDENCE. 2 PM UPDATE... 3-5 FT SOUTHERLY SWELLS WITH A PERIOD OF 12 SECONDS AT BUOY 44097 SOUTHEAST OF BLOCK ISLAND. THUS SWELLS FROM CRISTOBAL HAVE ENTERED SOUTHERN NEW ENGLAND WATERS. EARLIER DISCUSSION BELOW. ============================================================ TODAY...HIGH PRESSURE OVER THE WATERS WILL SHIFT FARTHER OFFSHORE. EXPECT LIGHT WINDS/PATCHY FOG FIRST THING THIS MORNING...OTHERWISE GOOD VSBY WITH SOUTHWEST WINDS 10-15 KNOTS. AN APPROACHING COLD FRONT MAY BRING SCATTERED SHOWERS/TSTMS TOWARD EVENING. TONIGHT...INCREASING SOUTH SWELL FROM HURRICANE CRISTOBAL. THE SOUTHERN WATERS WILL EXPERIENCE A 5 FOOT SWELL IN THE EARLY NIGHT AND 6 TO 8 FOOT SWELL BY MORNING. THURSDAY...SOUTH SWELL CONTINUES THROUGH THE DAY WITH 6 TO 9 FOOT SEAS...MAINLY SWELL...ON THE SOUTHERN WATERS. NORTHWEST WIND WILL BE GUSTY NEAR SHORE WITH MAXIMUM GUSTS AROUND 20 KNOTS. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY... THURSDAY NIGHT...HIGH CONFIDENCE. EXPECT S SWELL FROM HURRICANE CRISTOBAL TO CONTINUE THROUGH THE NIGHT...THOUGH MAY START TO SUBSIDE LATE. SEAS UP TO 7-9 FT ON THE OUTER WATERS. N-NW WIND GUSTS UP TO 20 KT ON THE EASTERN OUTER WATERS. FRIDAY...HIGH CONFIDENCE. N WINDS GUSTING TO 20 KT EARLY...THEN WILL VEER TO E-NE AND DIMINISH DURING THE DAY. SEAS MAY LINGER AT AROUND 5 FT ON THE OUTER WATERS DURING THE DAY BEFORE SUBSIDING. SATURDAY AND SUNDAY...MODERATE CONFIDENCE. WINDS BECOME S-SW DURING SAT AND CONTINUE THROUGH SUN. GUSTS SHOULD REMAIN BELOW SMALL CRAFT CRITERIA...BUT SEAS MAY BUILD UP TO AROUND 5 FT ON THE SOUTHERN OUTER WATERS.
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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 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 FROM 5 PM THIS AFTERNOON TO 8 PM EDT THURSDAY FOR ANZ235-237-254>256.
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&& $$ SYNOPSIS...WTB/EVT NEAR TERM...NOCERA SHORT TERM...WTB LONG TERM...EVT AVIATION...NOCERA/EVT MARINE...WTB/EVT

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