Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 270659 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 159 AM EST THU NOV 27 2014 .SYNOPSIS... STRONG LOW PRESSURE JUST SOUTH OF NANTUCKET WILL CONTINUE TO DEEPEN AS IT MOVES TOWARD NOVA SCOTIA OVERNIGHT. THE VARIETY OF WEATHER IMPACTS FROM THIS STORM WILL DIMINISH OVERNIGHT...WITH CONDITIONS IMPROVING FOR THANKSGIVING DAY. HIGH PRESSURE BUILDS OVER NEW ENGLAND FRIDAY...THEN SHIFTS OFFSHORE OVER THE WEEKEND. A WARM FRONT MOVES ACROSS THE REGION SATURDAY NIGHT. A COLD FRONT THEN SWINGS THROUGH NEW ENGLAND LATE SUNDAY NIGHT OR MONDAY. ANOTHER WARM FRONT APPROACHES NEXT WEDNESDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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130 AM UPDATE... LOW PRES CONTINUES TO SHIFT NE INTO THE GULF OF MAINE AT 06Z. AREA OF MIXED RAIN/SNOW ALSO MOVES SLOWLY NE...BUT NOTING THAT IT HAS TENDED TO FILL IN ACROSS CENTRAL-W MA/S NH OVER THE LAST FEW HOURS. AS COLDER AIR WORKS IN ON DIMINISHING N WINDS...COULD SEE A LITTLE BIT MORE ACCUMULATION ESPECIALLY ACROSS S NH. ALSO...AS TEMPS FALL BACK OVERNIGHT TO THE MID TO UPPER 20S ACROSS THE INTERIOR WHERE THE HEAVIER SNOW HAS FALLEN...ANY AREAS THAT ARE STILL WET OR SNOW COVERED WILL FREEZE UP ESPECIALLY ON UNTREATED SURFACES. ALSO STILL NOTING N WINDS GUSTING UP TO 30-40 KT ACROSS CAPE COD AND THE ISLANDS AS LAST OF PRES GRADIENT AND LOW LEVEL JET MOVES OUT. HAVE UPDATED NEAR TERM FORECAST TO BRING CONDITIONS CURRENT. SHOULD SEE PRECIP TAPER OFF FROM SW-NE THROUGH REMAINDER OF THE OVERNIGHT.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 AM FRIDAY/... SEE LONG TERM SECTION. && .LONG TERM /TODAY THROUGH WEDNESDAY/...
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BIG PICTURE... THANKSGIVING STARTS WITH A TWO-STREAM TROUGH OVER THE EASTERN USA AND A RIDGE OVER THE WEST. SHORTWAVE IN THE SOUTHERN STREAM MOVES OVER NEW ENGLAND THURSDAY...QUICKLY FOLLOWED BY A NORTHERN STREAM SHORTWAVE ON FRIDAY. THE FLOW GOES ZONAL OVER THE WEEKEND. A SHORTWAVE IN THE NORTHERN STREAM DROPS SOUTH FROM NORTHERN CANADA AND MOVES ALONG THE BORDER EARLY NEXT WEEK. A SECOND NORTHERN SHORTWAVE WILL DEEPEN OVER THE GREAT LAKES MIDWEEK DRAWING MILDER AIR NORTH OVER NEW ENGLAND. MODEL UPPER CONTOURS ARE SIMILAR THROUGH THE WEEKEND. THE GGEM EDGES FASTER EARLY NEXT WEEK. THE ECMWF BECOMES SHARPER WITH THE GREAT LAKES SHORTWAVE NEXT MIDWEEK BUT HAS A SIMILAR AXIS LOCATION AS THE GFS. WE FAVORED A BLEND OF THE MODEL DATA. THE DAILIES... THURSDAY-FRIDAY....SOUTHERN AND NORTHERN STREAM SHORTWAVES MOVE ACROSS NEW ENGLAND. THIS MAINTAINS SOME WEAK LIFT IN AN AIRMASS THAT MAINTAINS DEEP MOISTURE THROUGH FRIDAY MORNING BEFORE DRYING. WITH THIS COMBINATION WE HELD ON TO CHANCE POPS THURSDAY ACROSS MUCH OF MASS AND NH. THE AIRMASS DRIES FRIDAY SO LAND AREAS SHOULD SEE A CLEARING TREND. OVER WATER THERE WILL BE AN 18C AIR-WATER TEMP DIFFERENCE...AN EQUILIBRIUM LEVEL OF 6400 FEET...AND A 12-14 KNOT NORTHWEST WIND. THIS SHOULD SUPPORT OCEAN EFFECT RAIN/SNOW SHOWERS. THE NORTHWEST FETCH WILL FAVOR MAINLY OFFSHORE SHOWERS ALTHOUGH PROVINCETOWN AND TRURO MIGHT GET CLIPPED. SATURDAY-SUNDAY...HIGH PRESSURE AXIS SHIFTS OFFSHORE. CLOUDS INCREASE IN THE WARM ADVECTION...BUT LIFT IS RATHER WEAK. WE INDICATED SLIGHT CHANCE POPS SATURDAY AS A WARM FRONT LIFTS NORTHEAST THROUGH THE REGION. DECREASING CLOUDS AND POPS SUNDAY AS THE WARM FRONT SHIFTS NORTH OF US. MONDAY...GREAT LAKES SHORTWAVE/SURFACE LOW SWINGS A COLD FRONT THROUGH NEW ENGLAND. THERE IS UNCERTAINTY AS TO TIMING OF THE FRONT...BUT LIMITED SUPPORT FOR LIFT AND SHOWERS FROM THE RIGHT ENTRANCE REGION OF A TRAILING UPPER JET. WE INDICATED CHANCE POPS AND STRETCHED THE TIME FROM EARLY MORNING THROUGH THE EVENING. TUESDAY-WEDNESDAY...HIGH PRESSURE MOVES ACROSS THE REGION TUESDAY AND BRINGS COOLER TEMPS. THE NEXT SHORTWAVE APPROACHES WEDNESDAY WITH WARM ADVECTION RUNNING OVER THE TOP OF THOSE COOLER TEMPS. WE USED CHANCE POPS FROM EARLY MORNING THROUGH THE DAY. TEMPERATURE PROFILES SUGGEST A MIX OF PCPN AT THE START ESPECIALLY NORTH/WEST OF BOSTON...BUT TEMPS WARM ENOUGH ON WEDNESDAY FOR RAIN.
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&& .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 TONIGHT/...MODERATE CONFIDENCE. THROUGH 12Z...AREAS OF MVFR-IFR CIGS/VSBYS WILL CONTINUE THROUGH 08Z-10Z THEN SHOULD SLOWLY IMPROVE ACROSS N CT/RI INTO W MA TOWARD DAYBREAK. N WINDS GUSTING TO 30-35 KT THROUGH 08Z ACROSS CAPE COD AND THE ISLANDS THEN SHOULD DIMINISH. TODAY...LEFTOVER MVFR-IFR CIGS/VSBYS ACROSS CENTRAL/N MA INTO S NH SHOULD IMPROVE TO VFR BY MID MORNING. MAY SEE MVFR REDEVELOP ACROSS N CT/RI/SE MA DURING THE AFTERNOON ALONG THE E COAST ALONG WITH MORE CLOUDS MOVING NE INTO N CT/RI/S COASTAL MA. TONIGHT...MVFR CIGS MOVE ACROSS THE REGION. PRECIP DEVELOPS ACROSS E MA INTO RI...POSSIBLY AS FAR W AS KORH-KIJD...AS INVERTED TROUGH TAKE SHAPE NEAR THE COAST. AREAS OF MVFR-IFR VSBYS DEVELOP IN RAIN AND/OR SNOW. VSBYS SHOULD REMAIN MAINLY VFR ACROSS CENTRAL AND WESTERN AREAS...THOUGH PATCHY FOG MAY FORM LATE AT NIGHT. KBOS TERMINAL...HIGH CONFIDENCE TODAY...LOWER CONFIDENCE TONIGHT IN EXACT TIMING AS PRECIP DEVELOPS. KBDL TERMINAL...HIGH CONFIDENCE. OUTLOOK...FRIDAY THROUGH MONDAY...MODERATE CONFIDENCE. FRIDAY...MVFR CIGS/VSBYS ACROSS CENTRAL AND EASTERN AREAS IN RAIN AND/OR SNOW THROUGH EARLY AFTERNOON THEN WILL SLOWLY IMPROVE. MAINLY VFR WEST OF THE WORCESTER HILLS. NORTHWEST WINDS GUSTING 15-20 KNOTS. SATURDAY-SUNDAY...INCREASING SKY COVER BUT MAINLY VFR. LOW POTENTIAL FOR MVFR CIGS MOVING NORTH OFF THE OCEAN INTO CAPE COD AND ISLANDS. INCREASING SOUTHWEST WINDS AT 2000 FEET AGL...REACHING 35-40 KNOTS...WITH LIGHTER SOUTHWEST WINDS AT SURFACE. THIS WOULD MEAN POTENTIAL FOR LOW LEVEL WIND SHEAR SUNDAY. MONDAY...COLD FRONT MOVES ACROSS NEW ENGLAND WITH SCATTERED SHOWERS. BRIEF MVFR CIGS/VSBYS IN ANY SHOWERS. CONTINUED SOUTHWEST WINDS AHEAD OF THE FRONT WITH 35-40 KNOTS AT 2000 FEET AGL AND POTENTIAL LOW LEVEL WIND SHEAR.
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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 /THROUGH TONIGHT/... TONIGHT...HIGH CONFIDENCE. GALE CENTER TRACKS JUST SOUTH OF NANTUCKET AND EAST OF OUTER CAPE COD BY MIDNIGHT. NE GALE FORCE WINDS WILL PUSH NE BETWEEN 05Z-07Z THEN WILL BACK TO N-NW THROUGH THE REMAINDER OF THE NIGHT AS THEY DIMINISH. SEAS APPEAR TO HAVE MAXED OUT AT 10-15 FT ON THE OPEN WATERS INCLUDING MASS AND IPSWICH BAYS AND UP TO 6 FT ON THE SOUTHERN OPEN SOUNDS...WHICH SHOULD SLOWLY SUBSIDE THROUGH THE REMAINDER OF THE NIGHT. LOW VSBYS IN RAIN EARLY...THEN WILL SLOWLY IMPROVE AS PRECIP WEAKENS. PRECIP WILL MIX WITH OR CHANGE TO SNOW SHOWERS BEFORE ENDING ACROSS THE SOUTHERN WATERS BY AROUND 08Z- 09Z...BUT COULD LINGER ON THE EASTERN WATERS THROUGH SUNRISE. OUTLOOK...THURSDAY THROUGH MONDAY...MODERATE CONFIDENCE. THURSDAY...NORTHWEST WINDS GUST NEAR 25 KNOTS EARLY BUT DIMINISH THROUGH THE DAY. SEAS START THE DAY ROUGH...WITH HEIGHTS 8 TO 12 FEET ON THE EXPOSED WATERS...THEN DIMINISH THROUGH THE DAY. SMALL CRAFT ADVISORY WILL BE NEEDED ON MOST WATERS. FRIDAY... LINGERING 5 TO 6 FOOT SEAS ON THE OUTER WATERS. NORTHWEST WINDS WILL GUST NEAR 20 KNOTS. A SMALL CRAFT ADVISORY MAY BE NEEDED ON SOME OF THE WATERS. SATURDAY-SUNDAY... SOUTHWEST WINDS GUSTING TO 20 TO 25 KNOTS SATURDAY AND AROUND 25 KNOTS SUNDAY. SEAS WILL BE LESS THAN 5 FEET SATURDAY AND THEN BUILD TO 5 TO 6 FEET ON THE EXPOSED WATERS SUNDAY. A SMALL CRAFT ADVISORY MAY BE NEEDED SUNDAY. MONDAY...SOUTHWEST WINDS GUSTING 20 TO 25 KNOTS UNTIL THE COLD FRONT MOVES THROUGH. WINDS THEN SHIFT TO WEST-NORTHWEST BEHIND THE FRONT WITH SIMILAR GUSTS. SEAS ON THE EXPOSED WATERS WILL BE 5 TO 8 FEET. A SMALL CRAFT ADVISORY MAY BE NEEDED. && .TIDES/COASTAL FLOODING... HIGH TIDE OF CONCERN IS SHORTLY AFTER MIDNIGHT TONIGHT. STRONGEST WINDS AND PRESSURE FALLS OCCUR DURING LOW TIDE THIS EVENING WITH WINDS AND SURGE EASING TOWARD HIGH TIDE. THUS IMPACTS WILL BE LIMITED WITH VERY MINOR EROSION AND TIDAL FLOODING. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...WINTER STORM WARNING UNTIL 7 AM EST THIS MORNING FOR MAZ002>004-008>011-026. WIND ADVISORY UNTIL 3 AM EST EARLY THIS MORNING FOR MAZ019- 022>024. NH...WINTER STORM WARNING UNTIL 7 AM EST THIS MORNING FOR NHZ011- 012-015. RI...NONE. MARINE...GALE WARNING UNTIL 5 AM EST EARLY THIS MORNING FOR ANZ230>237. GALE WARNING UNTIL 7 AM EST THIS MORNING FOR ANZ250-251- 254>256.
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&& $$ SYNOPSIS...WTB/RLG NEAR TERM...WTB/EVT SHORT TERM...RLG LONG TERM...WTB AVIATION...WTB/EVT MARINE...WTB/RLG/EVT TIDES/COASTAL FLOODING...STAFF

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