Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 270011 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 811 PM EDT THU MAR 26 2015 .SYNOPSIS... AN APPROACHING COLD FRONT WILL BRING PERIODS OF SHOWERS INTO FRIDAY MORNING. WEAK LOW PRESSURE MAY BRING SCATTERED SNOW SHOWERS FRIDAY NIGHT 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. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 745 PM UPDATE... MOST OF THE CONVECTION THAT CROSSED NE CT/RI/E MA OVER THE LAST COUPLE OF HOURS HAS MOVED OFFSHORE. NOTING ANOTHER LINE OF SHOWERS/TSTMS ACROSS E PA ON LATEST NE REGIONAL 88D RADAR WHICH WILL TRAVERSE NE NEAR OR AHEAD OF APPROACHING COLD FRONT. HOWEVER...WITH PREVIOUS CONVECTION TENDING TO STABILIZE THE AIRMASS...A COUPLE OF TSTMS MAY MAKE IT ACROSS BUT NOT AS ORGANIZED AS CURRENTLY DEPICTED ON RADAR. APPEARS THAT COLD FRONT HAS WORKED INTO S NH AND W MA...THOUGH NOTING TWO MORE WAVES WILL MOVE ALONG THIS FRONT...ONE OUT OF SE PA ASSOCIATED WITH ORGANIZED CONVECTION AND THE SECOND FROM W VA/W NC. THIS WILL BRING A COUPLE MORE AREAS OF SHOWERS WITH LOCALIZED HEAVY DOWNPOURS. NOTING PATCHY DENSE FOG REPORTED ACROSS PORTIONS OF THE CT VALLEY AS WELL AS ACROSS THE WORCESTER HILLS AS WINDS ARE EITHER LIGHT N-NW OR CALM THERE. VSBYS RANGING FROM 1/4SM TO 1SM...NOT STEADILY REDUCED SO NOT PLANNING ON EXPANDING DENSE FOG ADVISORY THERE AT THIS TIME. WILL CONTINUE TO MONITOR. VSBYS APPEAR TO BE IMPROVING WITH STEADY SW WINDS ALONG THE S COAST...CAPE COD AND THE ISLANDS...THOUGH WHEN THE WINDS DIMINISH SOMEWHAT THE VSBYS LOWER AGAIN. WILL HANG ON TO THE ADVISORY THERE FOR NOW. HAVE UPDATED NEAR TERM FORECAST TO BRING CONDITIONS CURRENT CONSIDERING FLUCTUATING VSBYS/FOG AND AREAS OF SHOWERS MOVING ACROSS. PREVIOUS DISCUSSION... WILL SEE A BIT OF A LULL IN THE ACTIVITY...BUT COLD FRONT DROPPING DOWN INTO SOUTHERN NEW ENGLAND WILL ALLOW ADDITIONAL SHOWERS TO REDEVELOP. BRIEF LOCALLY HEAVY RAINFALL MAY RESULT IN TYPICAL POOR DRAINAGE NUISANCE STREET FLOODING...BUT NO SIGNIFICANT FLOODING PROBLEMS ARE EXPECTED. PRETTY GOOD BAND OF MID LEVEL FRONTOGENESIS NOTED BEHIND THE ACTUAL SURFACE COLD FRONT. THEREFORE...EXPECT RAIN TO PERSIST THROUGH THE OVERNIGHT HOURS ACROSS MUCH OF THE REGION. IN FACT...COLDER AIR WILL BEGIN TO WORK INTO THE REGION FROM THE NORTHWEST. IF PRECIPITATION INTENSITY IS ENOUGH...DYNAMIC COOLING MAY ALLOW RAIN TO CHANGE TO A BRIEF PERIOD OF WET SNOW ACROSS THE HIGH TERRAIN OF INTERIOR MASS TOWARD DAYBREAK. MOST OF THE GUIDANCE SUGGESTS JUST A DUSTING TO LESS THAN 1 INCH OF SNOW...WHICH IS IN LINE WITH OUR CURRENT THINKING. HOWEVER...THE NAM MODEL IS MOST ROBUST WITH IT ACTUALLY SHOWING THE POTENTIAL FOR A NARROW SWATH OF 2 TO 3 INCHES OF SNOW ACROSS THE WORCESTER HILLS. GIVEN THAT BOUNDARY LAYER IS MARGINAL...FEEL THAT IS A LOW PROBABILITY BUT WE CAN NOT COMPLETELY RULE IT. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... FRIDAY... MID LEVEL FRONTOGENESIS BEHIND THE ACTUAL COLD FRONT WILL ALLOW FOR RAIN TO CONTINUE ACROSS EASTERN NEW ENGLAND FRIDAY MORNING. AS WE MENTIONED IN THE PREVIOUS SECTION...IT MAY BECOME JUST COLD ENOUGH ACROSS THE HIGHER TERRAIN OF MASS FOR A CHANGE TO WET SNOW BEFORE PRECIPITATION ENDS. THINGS SHOULD DRY OUT FOR MOST OF THE REGION BY AFTERNOON AS BEST FORCING DEPARTS...BUT SOME LINGERING SHOWERS WILL REMAIN POSSIBLE OVER THE SOUTHEAST NEW ENGLAND COAST. ACROSS THE REST OF THE REGION...PLENTY OF CLOUDS WILL LINGER EVEN THOUGH THE RAIN WILL HAVE COME TO AN END. HIGH TEMPS MAINLY IN THE 40S. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... HIGHLIGHTS... * SCT SNOW/RAIN SHOWERS FRIDAY NIGHT INTO SATURDAY EVENING * 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... FRIDAY NIGHT THROUGH SATURDAY NIGHT...MODERATE CONFIDENCE. COLD FRONT WORKS THROUGH EARLY FRIDAY NIGHT AS FRONT WEAKENS. HOWEVER...STILL GOOD LIFT AND FORCING AS UPPER TROUGH WORKS E OUT OF NY STATE OVERNIGHT. THIS...ALONG WITH COLD POOL ALOFT...WILL CAUSE LIGHT RAIN SHOWERS TO CHANGE TO SNOW SHOWERS OVERNIGHT. GENERALLY A TENTH OF A INCH OR LESS OF QPF EXPECTED...SO NOT EXPECTING MUCH IN THE WAY OF ACCUMULATIONS AT THIS POINT. HOWEVER... MOST MODELS AND ENSEMBLES CONTINUE TO SIGNAL DEVELOPMENT OF INVERTED TROUGH LATE FRI NIGHT THROUGH MIDDAY SATURDAY AS ANOTHER LOW PASSES WELL S OF THE 40N/70W BENCHMARK. WITH THE LOW LEVEL MOISTURE IN PLACE ALONG WITH STEEP LAPSE RATES WILL ALLOW FOR ENHANCEMENT OF RAIN/SNOW SHOWERS. EXPECT PRECIP TO REMAIN MAINLY AS LIGHT SNOW... THOUGH TEMPS MIGHT RISE ENOUGH /MID-UPPER 30S/ TO MIX/CHANGE TO RAIN AROUND MIDDAY BUT CHANGE BACK SNOW BEFORE TAPERING OFF FROM N-S LATE IN THE DAY OR SAT EVENING. BIG QUESTION AT THIS POINT WILL BE WHETHER AND...IF SO WHERE... THE INVERTED TROUGH WILL SET UP TO FOCUS THE INSTABILITY AND PRECIP. GENERALLY...EXPECT LESS THAN AN INCH. BUT...IF THIS DOES SET UP...SOME LOCATIONS MIGHT SEE A SLUSHY 1-2 INCH ACCUMULATION. LOW CONFIDENCE WITH THIS ASPECT BUT SOMETHING TO DEFINITELY KEEP AN EYE ON. OVERNIGHT LOWS FRI NIGHT WILL BE DROP TO THE LOWER-MID 30S ACROSS THE HIGHER INLAND TERRAIN...RANGING TO AROUND FREEZING ALONG THE S COAST. HOWEVER...WITH COLD AIR ADVECTION ALONG WITH PRECIP...TEMPS WILL NOT RISE MUCH ON SAT. HIGHS WILL ONLY RISE TO THE MID AND UPPER 30S...MORE TYPICAL OF JANUARY RATHER THAN THE END OF MARCH. 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. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...TONIGHT AND FRIDAY... TONIGHT...MODERATE CONFIDENCE. EXPECT PERIODIC SHOWERS THROUGH THE NIGHT WITH MAINLY IFR CONDITIONS. LOW CLOUDS WILL LINGER...AREAS OF FOG AS WELL. NOTING AREAS OF VLIFR VSBYS ALONG S COAST...CAPE COD AND ISLANDS WITH SPOTTY VSBYS AOB 1/2SM AT TIMES ACROSS CT VALLEY INTO CENTRAL MA MAINLY ACROSS THE WORCESTER HILLS. WILL SEE SLOW IMPROVEMENT BUT REMAINING AT LEAST MVFR OVERNIGHT ACROSS THE REGION. LLWS WILL CONTINUE AS SW LOW LEVEL JET AT 60-65 KNOTS ACROSS N CT/RI/E MA WILL MOVE OFFSHORE BETWEEN 07Z AND 09Z. FRIDAY...MODERATE TO HIGH CONFIDENCE. RAIN SHOWERS SHOULD COME TO AN END FOR MOST OF THE REGION DURING THE MORNING...ALTHOUGH MAY LINGER A BIT LONGER ACROSS THE FAR SOUTHEAST MA COAST. PTYPE MAY ACTUALLY CHANGE TO A BIT OF WET SNOW BEFORE ENDING ACROSS THE HIGHER TERRAIN...BUT ODDS OF ANY REAL ACCUMULATIONS ON RUNWAYS ARE RATHER LOW. OTHERWISE...CONDITIONS SHOULD IMPROVE TO MAINLY VFR BY AFTERNOON ALTHOUGH SOME MARGINAL MVFR CIGS MAY PERSIST AT TIMES. KBOS TAF...MODERATE CONFIDENCE IN TAF. KBDL TAF...MODERATE CONFIDENCE IN TAF. OUTLOOK...FRIDAY NIGHT THROUGH TUESDAY...MODERATE CONFIDENCE. FRIDAY NIGHT AND SATURDAY...MAINLY MVFR CIGS/LOCAL MVFR-IFR VSBYS IN RAIN AND/OR SNOW SHOWERS FRI NIGHT. EXPECT LIGHT SNOW FRI NIGHT AFTER MIDNIGHT INTO SATURDAY MORNING. LESS THAN AN INCH OF SLUSHY SNOW ACCUMULATION EXPECTED...BEST CHANCE AT KORH AS WELL AS REMAINDER OF WORCESTER HILLS. PRECIP BRIEFLY CHANGES TO -SHRA AROUND MIDDAY...THEN BACK TO -SHSN TOWARD NIGHTFALL. 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. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...TONIGHT AND FRIDAY... TONIGHT...MODERATE CONFIDENCE. SOUTH TO SOUTHWEST WIND GUSTS OF 20 TO 30 KNOTS EXPECTED THIS EVENING AHEAD OF AN APPROACHING COLD FRONT. HIGH DEWPOINT AIR WILL ALSO RESULT IN AREAS OF DENSE FOG. SEAS WILL BUILD TO BETWEEN 5 AND 9 FEET ACROSS THE OUTER-WATERS. WINDS SHIFT TO THE NORTH BEHIND THE COLD FRONT BETWEEN 6 AND 12Z. FRIDAY...MODERATE TO HIGH CONFIDENCE. NORTHERLY WINDS OF 10 TO 15 KNOTS WITH GUSTS TO 20 KNOTS EXPECTED BEHIND THE COLD FRONT. LEFT OVER SOUTH TO SOUTHEAST SWELL WILL KEEP SEAS ABOVE SMALL CRAFT THRESHOLDS ACROSS MOST OPEN WATERS THROUGH FRI AFTERNOON. OUTLOOK...FRIDAY NIGHT THROUGH TUESDAY... MODERATE CONFIDENCE. FRIDAY NIGHT....N-NW WINDS GUSTING UP TO AROUND 25 KT BEHIND FRONTAL PASSAGE. SEAS ALSO BUILD UP TO 6-8 FT ON THE OUTER WATERS. SMALL CRAFTS NEEDED. SATURDAY AND SATURDAY NIGHT...NW WIND GUSTS MAY APPROACH 30 KT ON THE EASTERN OUTER WATERS DURING SAT...THEN SLOWLY DIMINISH SAT NIGHT. SEAS MAY APPROACH 10 FT ON THE EASTERN OUTER WATERS SAT...THEN WILL SLOWLY SUBSIDE BUT REMAIN AOA 5 FT. 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. && .HYDROLOGY... BASIN AVERAGE RAINFALL AMOUNTS WILL RANGE FROM 0.5 TO 1.25 INCHES ACROSS THE REGION THROUGH FRIDAY MORNING. NOHRSC MODELING ADDS 1 TO 2 INCHES OF WATER FROM MELTING SNOW DUE TO DEWPOINTS IN THE 40S TO NEAR 50. THIS WILL BRING RISES ON RIVERS AND STREAMS THROUGH FRIDAY... ESPECIALLY SMALLER ONES WHICH MAY APPROACH BANKFULL. HOWEVER... GIVEN RAINFALL HAS BEEN SPREAD OUT OVER A LONG DURATION WITH MANY DRY PERIODS DO NOT EXPECT ANY SIGNIFICANT FLOODING PROBLEMS. BRIEF HEAVY RAINFALL IN SHOWERS MAY RESULT IN TYPICAL NUISANCE POOR DRAINAGE STREET FLOODING TONIGHT...BUT AGAIN NOTHING SIGNIFICANT EXPECTED. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...DENSE FOG ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR MAZ020>024. RI...DENSE FOG ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR RIZ005>008. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT FRIDAY FOR ANZ232>234. SMALL CRAFT ADVISORY UNTIL 2 AM EDT FRIDAY FOR ANZ231-236. SMALL CRAFT ADVISORY UNTIL 8 PM EDT FRIDAY FOR ANZ235-237-250- 254>256. && $$ SYNOPSIS...FRANK/EVT NEAR TERM...FRANK/EVT SHORT TERM...FRANK LONG TERM...EVT AVIATION...FRANK/EVT MARINE...FRANK/EVT HYDROLOGY...FRANK

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