Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 270756 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 356 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 MORNING. 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/...
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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.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
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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.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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HIGHLIGHTS... * WEAK COLD FRONT WILL MOVE THROUGH ON MONDAY BRINGING SCT SHOWERS * MODERATING TEMPS BY THE MIDDLE OF NEXT WEEK OVERVIEW AND MODEL PREFERENCES... LONG TERM AMPLIFIED UPPER LEVEL PATTERN CONTINUES INTO THE EARLY PORTION OF THE LONG TERM FORECAST. BEYOND THIS WEEKEND...MEDIUM RANGE MODELS AND ENSEMBLES CONTINUE TO SIGNAL THE LONG WAVE TROUGHING THAT HAS BEEN NEARLY A CONSTANT OVER THE LAST COUPLE OF MONTHS ACROSS THE EASTERN U.S. WILL SHIFT SLOWLY E...BUT WILL BRING A FAST NW FLOW ALOFT EARLY NEXT WEEK. THIS WILL BRING FAST MOVING WEAK SYSTEMS ACROSS NEW ENGLAND. TIMING IS IN QUESTION DUE TO FAST MOVEMENT LENDING TO WIDE OPERATIONAL MODEL VARIANCE ALONG WITH LOWERED CONFIDENCE FROM LATE TUESDAY THROUGH THURSDAY. USED A BLEND OF AVAILABLE GUIDANCE THROUGH TUESDAY...THEN LEANED TOWARD THE SUPERBLEND ALONG WITH SOME BLENDING WITH THE ENSEMBLE MEANS TO TRY AND RESOLVE TIMING OF SYSTEMS TOWARD THE END OF THE FORECAST PERIOD. MODELS AND ENSEMBLES CONTINUE TO SIGNAL FAST FLOW ALOFT WITH MORE WAVES MOVING ALONG INTO FAST FLOW ALOFT INTO EASTER WEEKEND WHICH WILL NEED TO BE MONITORED. DETAILS... SATURDAY NIGHT...CONDITIONS WILL IMPROVE SATURDAY NIGHT FOR MOST AREAS...THOUGH SOME LEFTOVER LIGHT SNOW SHOWERS MIGHT LINGER ALONG THE S COAST. N WINDS WILL BE GUSTY...ESPECIALLY ACROSS THE CAPE AND ISLANDS. OVERNIGHT LOWS WILL FALL TO THE MID AND UPPER TEENS INLAND RANGING TO THE UPPER 20S ON THE OUTER CAPE AND NANTUCKET. SUNDAY-SUNDAY NIGHT...HIGH CONFIDENCE. AS UPPER TROUGH FINALLY MOVES OFFSHORE...EXPECT HIGH PRES RIDGING AT THE SURFACE AND ALOFT WILL BRING SUNSHINE ACROSS THE REGION. AS FAST NW FLOW ALOFT SETS UP...RIDGE WILL BUILD E DURING THE AFTERNOON AND CLOUDS WILL BEGIN TO FILTER IN. WILL SEE SOME WARM AIR ADVECTION WORK IN AS WINDS BACK TO W-SW...BUT NOT IN TIME FOR TEMPS TO RECOVER SO HIGHS WILL ONLY BE IN THE UPPER 30S TO MID 40S. TEMPS WILL DROP A FEW DEGS SUN NIGHT AS CLOUDS CONTINUE TO INCREASE. NEXT FAST MOVING SHORT WAVE IN THE UPPER FLOW APPROACHES. TIMING IS AN ISSUE...THOUGH LOOKS LIKE MOST OF THE MODEL SUITE HOLDS PRECIP OFF UNTIL MONDAY EXCEPT FOR POSSIBLY A FEW ISOLD SNOW SHOWERS TOWARD DAYBREAK ACROSS THE E SLOPES OF THE BERKSHIRES. MONDAY-MONDAY NIGHT...MODERATE CONFIDENCE. SHORT WAVE MOVES ACROSS BRINGING A PERIOD OF SNOW SHOWERS EARLY...CHANGING TO RAIN SHOWERS BY MIDDAY AS THE FRONT CROSSES THE REGION. TEMPS WILL MODERATE AHEAD OF THE FRONT. EXPECT HIGHS MAINLY IN THE MID 40S TO AROUND 50. SOME LEFTOVER RAIN SHOWERS WILL LINGER ACROSS CENTRAL AND EASTERN AREAS MON NIGHT BEFORE PUSHING OFFSHORE AS FRONT CLEARS THE COAST. UPPER LEVEL SHORT WAVE ALSO PUSHES E WITH NW FLOW KICKING BACK IN. HOWEVER...CORE OF H85 COLD AIR REMAINS N OF THE REGION. WILL STILL SEE COOLER TEMPS...BUT LOWS WILL ONLY FALL BACK TO THE UPPER 20S TO MID 30S AS SKIES BECOME PARTLY CLOUDY AFTER MIDNIGHT. TUESDAY THROUGH THURSDAY...LOW CONFIDENCE. FAST FLOW ALOFT CONTINUES...BRINGING ONE SYSTEM ACROSS. WITH WIDE TIMING ISSUES AMONGST INDIVIDUAL MODELS...HAVE RATHER LOW CONFIDENCE. FOR NOW...EXPECT DRY CONDITIONS TUE...THEN POSSIBLE SHOWERS TUE NIGHT INTO WED. LOOKS TO DRY OUT AGAIN BY MIDDAY WED. WARM FRONT MAY BRING CLOUDS AND THE CHANCE FOR PRECIP WED NIGHT/THU.
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&& .AVIATION /07Z 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...MODERATE CONFIDENCE. SATURDAY NIGHT...LOCAL MVFR CIGS/VSBYS ACROSS N CT/RI/SE MA EARLY IN SCT SNOW SHOWERS BEFORE ENDING FROM N-S BY MIDNIGHT. SUNDAY AND SUNDAY NIGHT...VFR CONDITIONS. CLOUDS INCREASE FROM W-E SUN NIGHT...MAY BRIEFLY DROP TO MVFR ACROSS HIGHER TERRAIN OF W MA. MONDAY-TUESDAY...MAINLY VFR. LOCAL MVFR CIGS/VSBYS IN SCT RAIN SHOWERS. CHANCE OF -SHSN ACROSS CENTRAL-W MA/N CT THROUGH MIDDAY MONDAY. CONDITIONS IMPROVE FROM W-E MONDAY NIGHT...VFR ON TUESDAY.
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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. SATURDAY NIGHT...BRIEF LIGHT FREEZING SPRAY POSSIBLE ON PORTIONS OF EASTERN AND SOUTHERN OUTER WATERS SAT NIGHT. SUNDAY...EXPECT WINDS AND SEAS TO BRIEFLY DIMINISH BELOW SMALL CRAFT CRITERIA AS WINDS BACK FROM NW TO SW SUNDAY NIGHT. SEAS ALSO SUBSIDE BELOW 5 FT. MONDAY-TUESDAY...SW WINDS PICK UP DURING MONDAY...GUSTING TO 25 KT WITH SEAS BUILDING TO 5-7 FT. WINDS SHIFT TO W MON NIGHT-TUE WITH LOCAL GUSTS TO 25 KT ON THE OUTER WATERS. SEAS REMAIN AOA 5 FT ON THE SOUTHERN WATERS AS WELL AS PORTIONS OF THE EASTERN WATERS.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR ANZ232>234. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ235- 237-250-254>256.
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&& $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/EVT MARINE...WTB/EVT

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