Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 100621 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 221 AM EDT THU JUL 10 2014 .SYNOPSIS... SCATTERED THUNDERSTORMS WILL BE POSSIBLE TONIGHT AS A COLD FRONT MOVES THROUGH SOUTHERN NEW ENGLAND. THE FRONT MAY STALL JUST SOUTH OF THE CAPE AND ISLANDS DURING THURSDAY WHICH WILL BRING A LINGERING CHANCE OF SHOWERS THERE. HIGH PRESSURE BUILDS OVER NEW ENGLAND WITH DRY WEATHER FOR FRIDAY AND SATURDAY. A WARM FRONT MOVES NORTH ACROSS THE REGION SUNDAY NIGHT OR EARLY MONDAY. A COLD FRONT THEN SWINGS THROUGH LATER TUESDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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230 AM UPDATE... COLD FRONT CONTINUES TO SLOWLY MOVE ACROSS SOUTHERN NEW ENGLAND OVERNIGHT. LOOKING AT SURFACE OBS DEWPOINTS...FRONT IS STRADDLED OVER KGHG DOWN TO KGON. AS THE LOW LEVEL JET CONTINUES TO INCREASE...SHOWERS AND THUNDERSTORMS HAVE BEGUN TO FESTER. ALTHOUGH THERE IS A LACK OF STRONG INSTABILITY...THE DEEP LAYER MOISTURE AS NOTICED IN K VALUES COMBINED WITH STRONG SHEAR AS ALLOWED THESE STORM TO GROW. BELIEVE SEVERE WEATHER POTENTIAL IS LOW...CANNOT RULE OUT SOME STRONG STORMS WITH GUSTY WINDS AND LIGHTNING. BECAUSE THE FRONT IS SLOWING UP...AND SOUTHERLY FLOW RIDING ALONG THE FRONT WILL ALLOW FOR SMALL TEMP/DEWPOINT SPREAD AND THUS THE FOG DEVELOPMENT ACROSS THE CAPE AND ISLANDS. AS THE SHOWERS AND THUNDERSTORMS CONTINUE TO MOVE OVER THE SOUTHERN WATERS BELIEVE FOG AND LOW CLOUDS WILL MIX OUT AND LIFT WITHIN THE NEXT HOUR OR TWO. NORTH OF THE FRONT...DRY AIR IS MOVING INTO THE REGION ALLOWING FOR MORE COMFORTABLE CONDITIONS AND TEMPS INTO THE MID 60S.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... THURSDAY... FRONT BECOMES NEARLY STATIONARY...AND WILL LIKELY CONTINUE TO LINGER ALONG OR JUST SOUTH OF THE CAPE AND ISLANDS. THIS WILL ALLOW FOR SOME CLOUDINESS AND A SLIGHT CHANCE FOR SHOWERS IN THAT VICINITY. OTHERWISE ACROSS THE REMAINDER OF THE AREA...WITH LARGE HIGH PRESSURE CENTERED TO OUR NW...DRY AIR WILL LIKELY CONTINUE TO WORK INTO THE REGION ALLOWING FOR MOSTLY SUNNY SKIES. TEMPERATURES WILL ALSO BE A TAD COOLER WITH HIGHS REACHING ONLY IN THE LOW TO MID 80S...WITH SOME 70S ALONG THE COASTLINE WITH LIGHT FLOW ALLOWING FOR SEABREEZE DEVELOPMENT. THURSDAY NIGHT... MODELS INDICATE THAT THE NEARLY STATIONARY FRONT LINGERS JUST SOUTH OF THE CAPE AND ISLANDS FOR THE NIGHT. MAY STILL HAVE SOME CLOUDINESS FROM THE FRONT IN THAT AREA...AND A SLIGHT CHANCE OF SHOWERS. AGAIN ACROSS THE REMAINDER OF THE AREA...HIGH PRESSURE KEEPS DRY AIR OVER THE AREA WITH MOSTLY CLEAR SKIES ANTICIPATED. LOWS IN THE UPPER 50S TO MID 60S. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... BIG PICTURE... UPPER LOW PRESSURE LIFTS NORTHEAST THROUGH THE MARTIMES FRIDAY. UPPER HEIGHTS BUILD OVER NEW ENGLAND DURING THE WEEKEND. ANOTHER CLOSED LOW DEVELOPS OVER CENTRAL CANADA OVER THE WEEKEND AND DROPS SOUTH THROUGH THE GREAT LAKES EARLY NEXT WEEK...THEN SHIFTS EAST ACROSS NEW ENGLAND MIDWEEK. EXPECT SEASONABLY WARM TEMPERATURES THROUGH THE WEEKEND...WITH A COOLING TREND BY MIDWEEK. THE DAILIES... FRIDAY...HIGH PRESSURE BUILDS OVER THE REGION FRIDAY. STALLED FRONT LINGERS TO THE SOUTH...WITH THE RIGHT ENTRANCE REGION OF THE UPPER JET LOCATED OVER RI/EASTERN MASS. THIS BRINGS SOME CONCERN THAT CLOUDS AND SHOWERS MAY EXPAND ONSHORE FROM THE SOUTH DURING THE DAY. CROSS SECTIONS SHOW MOISTURE IS LIMITED AT THE SURFACE WITH DEWPOINTS IN THE 50S. WILL RETAIN SOME SKY COVER WITH HIGHEST VALUES NEAR THE SOUTH COAST...BUT POPS BELOW 15 PERCENT. TEMPS AT 850 MB WILL BE 12-13C...WHICH WOULD SUPPORT MAX TEMPS 80-84. FAIR AND DRY FOR FRIDAY NIGHT WITH LIGHT WIND AND POTENTIAL FOR RADIATIONAL COOLING TO NEAR DEWPOINT. WILL INCLUDE PATCHY FOG. SATURDAY-SUNDAY... HIGH PRESSURE REMAINS IN PLACE SATURDAY...THEN SHIFTS OFFSHORE SUNDAY WITH A DEVELOPING SOUTH-SOUTHWEST WIND. THIS WILL MAKE ROOM FOR INCREASING MID AND HIGH CLOUDS SUNDAY ESPECIALLY IN THE AFTERNOON. TEMPS ALOFT SLOWLY WARM TO 13-15C...SO MAX SFC TEMPS SHOULD TREND TOWARD THE MID 80S. SUNDAY NIGHT-MONDAY...CLOSED LOW IN FORMS IN CENTRAL CANADA OVER THE WEEKEND...THE PRODUCT OF ONE SHORTWAVE FROM THE WESTERN ARCTIC AND A SECOND SHORTWAVE MOVING EAST FROM NORTHERN BRITISH COLUMBIA. BY SUNDAY NIGHT THIS FEATURE IS MOVING SOUTH/EAST...NUDGED ALONG BY A 95-105 KNOT JET. THE LEADING PART OF THIS JET APPROACHES NEW ENGLAND SUNDAY NIGHT AND MAY PROVIDE UPPER SUPPORT FOR LIFT...WHILE A WARM FRONT MOVES UP FROM THE SOUTHWEST BRINGING WARMER MORE HUMID AIR MOVES BACK INTO OUR AREA. THIS MAY PRODUCE A FEW SHOWERS IN SOUTHERN NEW ENGLAND. BUT MOST OF THE DYNAMIC SUPPORT WITH THE JET LOOKS TO BE FOCUSSED TO OUR WEST AND NORTH. THE 300-310K ISENTROPIC SURFACES SHOW SOME LOW LEVEL LIFT IN OUR AREA...BUT WITH BETTER ISENTROPIC LIFT MOVING ACROSS NORTHERN NY AND VT-NH. WE WILL BRING CHANCE POPS SUNDAY NIGHT WITH THE APPROACH OF THE FRONT AND CONTINUE CHANCE POPS MONDAY IN THE WARM SECTOR. STABILITY PARAMETERS ARE MARGINAL SUNDAY NIGHT FOR THUNDER...BUT MOST FAVORABLE IN THE NORTHWEST. FAVORABLE FOR THUNDER ALL AREAS MONDAY AS WE WILL BE IN THE WARM SECTOR. PRECIPITABLE WATER VALUES WILL BE 1.75 TO 2.0 INCHES...SO WE WILL EXPECT LOCALLY HEAVY DOWNPOURS ESPECIALLY ON MONDAY. TUESDAY... COLD FRONT SWEEPS THROUGH ON TUESDAY. UPPER JET WILL BE IN POSITION JUST TO OUR WEST WITH UPPER LOW OVER ONTARIO AND RIGHT ENTRANCE REGION OF THE JET OVER SOUTHERN NEW ENGLAND. EXPECT SHOWERS/TSTMS ALONG OR AHEAD OF THE COLD FRONT. WE WILL CONTINUE TO MENTION LOCALLY HEAVY DOWNPOURS DUE TO THE SAME AIRMASS BEING IN PLACE WITH HIGH PRECIP WATER VALUES. WEDNESDAY... COLD FRONT MOVES OFFSHORE AS UPPER LOW PASSES NORTH OF NEW ENGLAND. RH CROSS SECTIONS SHOW DRY AIR ABOVE 800 MB AND PATCHY MOISTURE BELOW...SUPPORTING MOSTLY SUNNY SKIES. THE UPPER SYSTEM/S COLD POOL WILL ADVECT IN DURING THE DAY AND WILL WORK TO DESTABILIZE THE AIRMASS ESPECIALLY WITH APPRECIABLE SUNSHINE. AS SUCH...THE FORECAST MAY BE A TAD OPTIMISTIC. DIURNAL CLOUDS AND SCATTERED SHOWERS MAY BE POSSIBLE...AND THIS POTENTIAL WILL NEED TO BE MONITORED. && .AVIATION /06Z 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 /THROUGH FRIDAY/... BEFORE 12Z...VFR ACROSS MANY SITES HOWEVER ACROSS THE CAPE AND ISLANDS...SHOWERS AND THUNDERSTORMS WILL CONTINUE TO FESTER. THIS COULD DROP CONDITIONS TO MVFR WITHIN ANY TSRA. TODAY...HIGH CONFIDENCE. VFR CONDITIONS EXPECT ACROSS THE CAPE AND ISLAND WHERE LINGERING MVFR CLOUDS AND FOG MAY OCCUR WITHIN ANY SHOWERS. SEA BREEZES ALONG BOTH COASTLINES. TONIGHT...HIGH CONFIDENCE. VFR CONDITIONS EXCEPT POSSIBLE MVFR CIGS CAPE AND ISLANDS. FRIDAY...MODERATE CONFIDENCE. VFR CONDITIONS. LOW PROB OF MVFR CIGS ACROSS THE INTERIOR. KBOS TAF...HIGH CONFIDENCE IN TAF. MODERATE CONFIDENCE ON SEA BREEZE TIMING. KBDL TAF...HIGH CONFIDENCE IN TAF. OUTLOOK...FRIDAY NIGHT THROUGH MONDAY...MODERATE CONFIDENCE. FRIDAY NIGHT THROUGH SUNDAY... VFR. AREAS OF IFR/LIFR CIGS/VSBYS IN EARLY MORNING FOG. SUNDAY NIGHT-MONDAY...VFR BUT WITH AREAS OF MVFR OR BRIEF IFR IN SHOWERS/TSTMS. LOCALLY HEAVY DOWNPOURS POSSIBLE IN ANY THUNDERSTORMS MONDAY.
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&& .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TODAY THROUGH THURSDAY/...MODERATE TO HIGH CONFIDENCE. TONIGHT...SCA HEADLINES FOR OUTER COASTAL WATERS AND RI/BI SOUNDS CONTINUE AS LONG SOUTHWEST FETCH WILL ALLOW PERSISTENT 4 TO 7 FOOT SEAS. IN ADDITION...AREAS OF FOG ARE EXPECTED AGAIN LATE TONIGHT INTO THURSDAY MORNING ACROSS THE SOUTHERN WATERS. THERE ALSO IS A LOW RISK OF THUNDERSTORMS WITH GUSTY WINDS ACROSS THE EASTERN WATERS INTO THE OVERNIGHT HOURS. THURSDAY AND THURSDAY NIGHT...A COLD FRONT WILL STALL OUT NEAR OR OVER THE SOUTHERN COASTAL WATERS DURING THIS TIMEFRAME. WINDS ARE EXPECTED TO BE BELOW 25 KT. HOWEVER...SCA HEADLINES CONTINUE FOR ROUGH SEAS ACROSS THE SOUTHERN OUTER COASTAL WATERS. ELSEWHERE...SEAS SHOULD SUBSIDE TO BELOW SCA THRESHOLDS FOR THURSDAY. OUTLOOK...FRIDAY THROUGH MONDAY...MODERATE CONFIDENCE. FRIDAY THROUGH SUNDAY...HIGH PRESSURE BUILDS OVER THE WATERS...THEN SHIFTS OFFSHORE SUNDAY. QUIET BOATING WEATHER MUCH OF THE TIME WITH LIGHT WINDS AND SEAS. WINDS TREND FROM THE SOUTH SUNDAY AFTERNOON BUT REMAIN BELOW 20 KNOTS. SUNDAY NIGHT-MONDAY...A WARM FRONT MOVES NORTH ACROSS THE WATERS. SOUTH TO SOUTHWEST WINDS WILL INCREASE A LITTLE BUT SHOULD REMAIN BELOW 25 KNOTS. THESE WINDS WILL DRIVE SEAS A LITTLE HIGHER WITH 5 FOOT HEIGHTS POSSIBLE...MAINLY ON THE OUTER WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ254>256. SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR ANZ235-237.
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&& $$ SYNOPSIS...WTB/NMB NEAR TERM...DUNTEN SHORT TERM...NMB LONG TERM...WTB AVIATION...WTB/DUNTEN MARINE...WTB/NMB

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