Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 270814 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 414 AM EDT FRI MAR 27 2015 .SYNOPSIS...
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COLD FRONT OFFSHORE HAS AN AREA OF SHOWERS MOVING ALONG IT UP THE COAST INTO NEW ENGLAND. THIS WILL MOVE OFFSHORE LATER THIS MORNING. A SECOND COLD FRONT IN THE ST LAWRENCE VALLEY WILL MOVE ACROSS NEW ENGLAND TODAY AND OFFSHORE TOWARD EVENING. WEAK LOW PRESSURE MOVING UP THE COAST MAY BRING SOME LIGHT SNOW TO SOUTHERN NEW ENGLAND TONIGHT AND SATURDAY. HIGH PRESSURE WILL PUSH SOUTH OF NEW ENGLAND SUNDAY. ANOTHER BATCH OF PRECIPITATION IS POSSIBLE LATE SUNDAY NIGHT INTO MONDAY AHEAD OF A COLD FRONT.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... THIS MORNING... AREA OF SHOWERS MOVING UP THE FRONT ALIGNS WELL WITH THE RIGHT ENTRANCE REGION OF THE UPPER JET. THIS JET MOVES OFF INTO THE MARITIMES BY AFTERNOON...SO THIS AREA OF RAIN/SHOWERS SHOULD MOVE OFF BY MIDDAY. TIMING FROM THE REGIONAL RADAR MOSAIC WOULD SUGGEST THE SHOWERS MOVE OFF AROUND MID MORNING...WHICH LINES UP WELL WITH THE MODEL DYNAMICS. THIS AFTERNOON... AIRMASS DRIES OUT A BIT DURING THE AFTERNOON. MODEL CROSS SECTIONS SHOW THE DRIER AIR AROUND 700 MB WHILE MOIST AIR LINGERS BELOW 850 MB. SO WE EXPECT LINGERING CLOUDS BUT PCPN TAPERING OFF MOST AREAS. EXCEPTION IS ALONG THE SOUTH COAST AND ISLANDS WHERE THERE WOULD BE A LINGERING CHANCE. TEMPS AT 950 MB SUPPORT MAX TEMPS IN THE 40S. THIS EVENING... ANOTHER UPPER JET MAX APPROACHES UP THE EAST COAST WITH SOUTHERN NEW ENGLAND IN THE LEFT EXIT REGION. THIS ALONG WITH A WEAKENING OF THE DRY LAYER WOULD SUGGEST AN RE-EXPANDING CHANCE OF PCPN IN SOUTHERN NEW ENGLAND. WE HAVE SHOWN CHANCE POPS RETURNING IN RI AND CT BY 00Z. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... UPPER TROUGH OVER THE GREAT LAKES SHIFTS EAST DURING THIS TIME. THIS BRINGS COLD ADVECTION ALOFT DESTABILIZING THE AIRMASS. THE UPPER JET INITIALLY PROVIDES UPPER VENTING AND LIFT TONIGHT. ALL OF THIS SUGGESTS A CHANCE OF PCPN DURING THE NIGHT AND LINGERING INTO SATURDAY MORNING. THE MODELS CONTINUE TO SHOW A WAVE OF LOW PRESSURE FORMING ALONG THE COLD FRONT WELL OFFSHORE. THEY ALSO SHOW AN INVERTED TROUGH EXTENDING UP ALONG THE EAST MASSACHUSETTS COAST. WE SAW THIS DURING THE SNOW BLITZ LAST MONTH...INDICATING AN INCREASED CHANCE OF SNOW SHOWERS IN EASTERN MASS OVERNIGHT AND SATURDAY MORNING. MODEL MOISTURE FIELDS ARE MARGINAL. TEMPERTURES FAVOR SNOW DURING THIS TIME...ALTHOUGH MORE MARGINAL FOR SNOW THAN OUR PREVIOUS EXPERIENCE. ALL-IN-ALL MOST PLACES SHOULD SEE LESS THAN AN INCH OF SNOW. BUT THE EXTRA SUPPORT FROM THIS TROUGH COULD YIELD A SLUSHY 1-2 INCHES ACCUMULATION. TEMPERATURES OF 25-35 ARE BORDERLINE FOR THIS ACCUMULATION...SO CONFIDENCE IN THOSE NUMBERS IS LOW- MODERATE. TEMPS WILL WARM A LITTLE DURING SATURDAY MORNING AND SHOULD BE ENOUGH TO CHANGE ANY SNOW OVER TO RAIN BY MIDDAY. TEMPS ALOFT SUPPORT MAX TEMPS IN THE 30S. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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HIGHLIGHTS... * OCEAN ENHANCED SNOW SHOWERS SATURDAY NIGHT * A WEAK COLD FRONT WILL MOVE THROUGH ON MONDAY BRINGING SCT SHOWERS * MODERATING SPRING-LIKE TEMPS INTO NEXT WEEK * ALBERTA CLIPPER MOVES THROUGH TUESDAY NIGHT INTO WED OVERVIEW... UNFORTUNATELY AN ACTIVE PATTERN APPEARS TO BE SETTING UP OVER SOUTHERN NEW ENGLAND BEGINNING THIS WEEKEND INTO NEXT WEEK. DEEP TROUGH WILL MOVE OVER SOUTHERN NEW ENGLAND ON SATURDAY PUSHING THE CAROLINA LOW SOUTH OF THE BENCHMARK AND TOWARDS THE MARITIMES. A QUICK MOVING RIDGE AND ASSOCIATED HIGH WILL FOLLOW ON SUNDAY BEFORE NORTHWEST FLOW SETS UP AS RIDGE BUILD OVER THE ROCKIES. THIS WILL ALLOW FOR SEVERAL WAVES TO PUSH THROUGH WITH THE FIRST MOVING FROM THE GREAT LAKES INTO NORTHERN NEW ENGLAND DRAGGING A COLD FRONT WITH IT ON MONDAY. NEXT AN ALBERTA CLIPPER WILL DIVE INTO SOUTHERN NEW ENGLAND BY LATE TUESDAY INTO WEDNESDAY. LASTLY A NORTHERN AND SOUTHERN STREAM MERGER APPEARS TO APPROACH BY LATE THURSDAY INTO FRIDAY. OVERALL GUIDANCE IS IN GOOD AGREEMENT UNTIL DAY 7 WHERE THEY ARE SPLIT IN TIMING ON THE THURSDAY SYSTEM AS THE EC IS MORE PROGRESSIVE THAN THE AMPLIFIED GFS. STILL MESO SCALE DETAILS AND THERMAL PROFILES TO WORK OUT BUT IT DOES LOOK LIKE THERE IS THE POTENTIAL FOR SOME SNOW SHOWERS INTO NEXT WEEK. DETAILS... * SATURDAY NIGHT...MODERATE CONFIDENCE. TEMPS OVERNIGHT WILL FALL WELL BELOW NORMAL WITH LOWS AROUND THE TEENS TO LOW 20S WITH THE COOLEST SPOTS OUT WEST AS SKIES WILL BEGIN TO CLEAR AS HIGH PRESSURE BEGINS TO BUILD IN. MAIN FOCUS ON SATURDAY NIGHT IS THE SNOW POTENTIAL. NAM/GFS ARE VERY BULLISH IN THEIR QPF COMPARED TO THE CONSERVATIVE EC. INVERTED TROUGH WILL BEGIN TO SLIDE EASTWARD DURING THE EVENING HOURS AS SURFACE LOW MOVES TOWARDS THE MARITIMES. HOWEVER SECONDARY SHORTWAVE WILL CONTINUE TO TRIGGER LIFT ALOFT AND WITH DELTA TS NEAR 20 DEGREE DIFFERENCE EXPECT OCEAN EFFECT SNOW SHOWERS TO DEVELOP/ENHANCE ONGOING SNOW SHOWERS. THIS IS ALSO SUPPORTED BY NORTH/NORTHEAST WINDS AND VERY STEEP LAPSE RATES. WENT WITH HPC QPF TO PLAY CONSERVATIVE BUT GENERALLY COULD SEE 1-2 INCHES ADDITIONAL FROM WHAT FALLS DURING THE DAY ON SATURDAY. WILL NEED TO WATCH THIS SET-UP CLOSELY AS WE COULD HAVE A SURPRISE 3 TO 4 INCH AMOUNTS SOMEWHERE ALONG THE EAST MASS COASTLINE. * SUNDAY...HIGH CONFIDENCE. SUNDAY IS A TRANSITION DAY AS DEEP TROUGH BEGINS TO PULL OFFSHORE AND UPPER LEVEL RIDGE MOVES INTO THE REGION. WARM AIR ADVECTION WILL BEGIN TO PUSH IN LATE IN THE DAY ALLOWING FOR TEMPS TO EVENTUALLY WARM INTO THE MID 40S. EXPECT MOSTLY CLEAR SKIES IN THE MORNING BUT THEY WILL BEGIN TO CLOUD UP DURING THE AFTERNOON AS THE NEXT SYSTEM APPROACHES FROM THE WEST. * MONDAY INTO TUESDAY...MODERATE CONFIDENCE. NEXT UPPER LEVEL DISTURBANCE WILL IMPACT SOUTHERN NEW ENGLAND LATE SUNDAY INTO MONDAY. STILL SOME SPREAD AMONGST THE GUIDANCE FOR TIMING WITH THE GFS BEING 6HRS FASTER THEN REST OF THE GUIDANCE. THEREFORE TRENDED TOWARDS EC/HPC ON THIS PORTION OF THE FORECAST. SURFACE LOW ACROSS THE GREAT LAKES WILL PASS JUST NORTH OF SNE...DRAGGING ASSOCIATED COLD FRONT WITH IT. TEMPS AT THE ONSET LOOK TO BE COOL THEN WARM UP DURING THE DAY ON MONDAY PRIOR TO FRONTAL PASSAGE. AT THE ONSET OF PRECIP...EXPECT A FEW SNOW SHOWERS...BUT THEN TRANSITIONING TO RAIN FAIRLY QUICKLY AS TEMPS WARM UP. MOISTURE IS MARGINAL SO COVERAGE MAY BE MORE SCT ALONG THE FRONT. * TUESDAY NIGHT INTO THURSDAY...LOW CONFIDENCE. NEXT SHORT WAVE WILL QUICKLY DIVE THROUGH THE FLOW FROM CANADA AND MOVE ACROSS OR JUST SOUTH OF SOUTHERN NEW ENGLAND. THE EC IS MORE AMPLIFIED/STRONGER WITH THIS SYSTEM CUTTING OFF THE 850 MB LOW COMPARED TO THE GFS WHICH KEEPS AN OPEN WAVE. TIMING IS ALSO AN ISSUE AS IF IT PASS OVERNIGHT THEN TEMPS WILL BE COOL ENOUGH FOR SNOW SHOWERS...VS A DAYTIME PASSAGE. STILL A GOOD AMOUNT OF TIME TO WATCH THIS SYSTEM BUT DEPENDING ON THE PLACEMENT OF THE LOW...WE COULD SEE ANOTHER 1-2 INCHES OF SNOW ACROSS THE AREA. WEAK RIDGE WILL FOLLOW BEHIND THE SYSTEM BEFORE NEXT LOW PRESSURE IMPACT SOUTHERN NEW ENGLAND EITHER THURSDAY OR FRIDAY. EC IS LESS AMPLIFIED AND MORE PROGRESSIVE COMPARED TO THE GFS. STILL PLENTY OF TIME TO WATCH THIS SYSTEM AS WELL.
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&& .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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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 AND FRIDAY... TODAY...MODERATE CONFIDENCE. RAIN SHOWERS THIS MORNING WILL TAPER OFF THIS AFTERNOON. OBSERVED VALUES LIFR IN THE EAST AND MIXED VFR/MVFR IN CT AND WESTERN MASS. EXPECT THE LIFR TO LINGER IN THE EAST WITH MVFR IN CT AND WESTERN MASS. CONDITIONS IMPROVE THIS AFTERNOON WITH VFR IN THE WEST AND MVFR CIGS IN THE EAST. TONIGHT AND SATURDAY...MODERATE CONFIDENCE... ANOTHER AREA OF SHOWERS MOVES IN WITH MVFR CIGS AND MVFR/IFR VSBYS. TEMPERATURES COOL ENOUGH DURING THE NIGHT TO CHANGE ANY RAIN TO SNOW. MOST OF THE IFR VSBYS SHOULD BE CONCENTRATED IN EASTERN MASS AND POSSIBLY RI. THIS CONTINUES INTO SATURDAY MORNING. TEMPERATURES SATURDAY SHOULD WARM INTO THE 30S WHICH SHOULD CHANGE THE SNOW TO RAIN IN THE COASTAL PLAIN...WHILE THE INTERIOR REMAINS SNOW. KBOS TAF...MODERATE CONFIDENCE IN TAF. KBDL TAF...MODERATE CONFIDENCE IN TAF. OUTLOOK...SATURDAY NIGHT THROUGH TUESDAY...HIGH CONFIDENCE. SATURDAY NIGHT INTO SUNDAY...VFR CONDITIONS LIKELY. SCT MVFR ALONG AND SOUTHEAST OF I-95 DUE TO OCEAN EFFECT SNOW SHOWERS. VSBYS MAY BE REDUCE IF HEAVY BAND OF SNOW SETS-UP. MONDAY...VFR DROPPING TO POSSIBLE MVFR IN SCT RAIN SHOWERS AS WEAK COLD FRONT MOVES THROUGH. TUESDAY...VFR.
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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 AND FRIDAY...MODERATE CONFIDENCE. TODAY... NORTH WINDS 10 TO 15 KNOTS WITH GUSTS TO 20 KNOTS. LINGERING SEAS OF 5 TO 9 FEET ON THE OUTER WATERS AND RHODE ISLAND/BLOCK ISLAND SOUNDS. SMALL CRAFT ADVISORY CONTINUES ON THESE WATERS. TONIGHT...NORTH WINDS PICK UP AS COLDER AIR MOVES SOUTH AND A DISTUBANCE PASSES WELL OFFSHORE. EXPECT WINDS GUSTING TO 25 KNOTS ON THE OUTER WATERS WITH SEAS LINGERING AT 5-6 FEET. SATURDAY...CONTINUED GUSTY WINDS REACHING 25 KNOTS ON THE OUTER WATERS. CONTINUED ROUGH SEAS 5-7 FEET ON THE OUTER WATERS. THERE IS POTENTIAL FOR WINDS GUSTING TO 25 KNOTS ON CAPE COD BAY AND NANTUCKET SOUND AS WELL. SMALL CRAFT ADVISORIES FOR THE OUTER WATERS AND RI WATERS HAVE BEEN EXTENDED UNTIL SATURDAY EVENING. OUTLOOK...SATURDAY NIGHT THROUGH TUESDAY... MODERATE CONFIDENCE INTO TUESDAY. SATURDAY NIGHT...SURFACE LOW WILL PASS WELL SOUTH AND EAST OF THE BENCHMARK. HOWEVER THIS WILL INCREASE WINDS UP TO 25-30 KTS AND BUILD SEAS THROUGH THE NIGHT. SCA WILL BE NEEDED. SUNDAY THROUGH MONDAY...HIGH PRESSURE QUICKLY BUILDS IN ON SUNDAY ALLOW FOR WINDS AND SEAS BRIEFLY SUBSIDE. BY SUNDAY NIGHT...WINDS BACK TO SW AND WITH APPROACHING COLD FRONT ON MONDAY WILL SEE SEAS INCREASE IN RESPONSE. THIS WILL ALLOW FOR SCA TO CONTINUE THROUGH THE PERIOD. TUESDAY...WEAK LULL IN BETWEEN SYSTEMS HOWEVER WINDS WILL BE GUSTY ON THE BACKSIDE OF THE FRONT REACHING NEAR 30KTS. THIS WILL KEEP SEAS UP ABOVE SCA.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT SATURDAY FOR ANZ235-237- 250-254>256.
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&& $$ SYNOPSIS...WTB/DUNTEN NEAR TERM...WTB SHORT TERM...WTB LONG TERM...DUNTEN AVIATION...WTB/DUNTEN MARINE...WTB/DUNTEN

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