Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 171720 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1220 PM EST WED DEC 17 2014 .SYNOPSIS...
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DRY WEATHER WILL PREVAIL THROUGH THE AFTERNOON...BUT ANOTHER DISTURBANCE WILL TRIGGER A BRIEF PERIOD OF SCATTERED RAIN AND HIGH TERRAIN SNOW SHOWERS TONIGHT. HIGH PRESSURE BUILDING IN FROM THE WEST WILL BRING DRY WEATHER FOR MOST OF THURSDAY AND FRIDAY. LOW PRESSURE MAY IMPACT SOUTHERN NEW ENGLAND EARLY NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1220 PM UPDATE... GETTING SOME BREAKS IN CLOUD COVER ACROSS SOUTHERN NEW ENGLAND THIS AFTERNOON. DESPITE DEVELOPING W/NW FLOW...EXPECT ANY BREAKS TO BE SHORT LIVED DUE TO LEFTOVER MOISTURE AND PRESENCE OF UPPER TROUGH STILL OVER REGION. HIGH-RES MODELS KEEP THINGS ESSENTIALLY DRY UNTIL LATE AFTERNOON WHEN WE SHOULD BEGIN TO SEE SCATTERED RAIN SHOWERS DEVELOP ACROSS INTERIOR...MIXED WITH SNOW SHOWERS ACROSS HIGHER TERRAIN. FORECAST HIGHS WERE TRIMMED DOWN A BIT GIVEN EXTENT OF CLOUD COVER...MAINLY IN 40S WITH LOWER 50S ACROSS SE NEW ENGLAND.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... TONIGHT... A POTENT SHORTWAVE WILL SWEEP ACROSS NEW ENGLAND TONIGHT. COLD POOL ALOFT SHOULD GENERATE FAIRLY STEEP LAPSE RATES ACROSS NORTHERN NEW ENGLAND ALONG WITH SOME LEFT OVER LOW LEVEL MOISTURE. WHILE THE BETTER FORCING/INSTABILITY MAY BE JUST NORTH OF OUR COUNTY WARNING AREA...THERE SHOULD BE ENOUGH FOR AT LEAST A PERIOD OF SCATTERED RAIN/SNOW SHOWERS MAINLY NORTH OF THE MA TURNPIKE. BOUNDARY LAYER SHOULD BE WARM ENOUGH FOR MAINLY RAIN SHOWERS OR JUST A MIXTURE OF RAIN/SNOW SHOWERS ALONG THE COASTAL PLAIN. ACROSS THE INTERIOR HIGH TERRAIN IT SHOULD TURN COLD ENOUGH FOR SNOW SHOWERS. IN FACT...TOTAL TOTALS OVER 50 MAY EVEN RESULT IN A LOCALIZED HEAVY SNOW SQUALL OR TWO WITH BEST SHOT NORTH OF ROUTE 2. ACCUMS MAINLY A COATING TO LESS THAN 1 INCH ACROSS HIGH TERRAIN. LOW PROBABILITY FOR AN INCH OR SO OF SNOW IN A FEW NEIGHBORHOODS NEAR THE NEW HAMPSHIRE BORDER IF A SQUALL OR TWO IS ABLE TO DEVELOP. THURSDAY... A LEFT OVER RAIN/SNOW SHOWER POSSIBLE EARLY IN THE MORNING...BUT GENERALLY DRY WEATHER EXPECTED WITH A MIXTURE OF CLOUDS AND SUN. HIGH TEMPS IN THE UPPER 30S TO THE MIDDLE 40S. LOW PRESSURE OVER THE CANADIAN MARITIMES AND HIGH PRESSURE ACROSS THE GREAT LAKES WILL RESULT IN BREEZY TO WINDY CONDITIONS ACROSS THE REGION. NORTHWEST WIND GUSTS OF 25 TO 35 MPH ARE EXPECTED. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... HIGHLIGHTS... * DRY WEATHER AND AT OR BELOW AVG TEMPS FRIDAY INTO SAT * WEAK WAVE OF LOW PRESSURE ON SUNDAY INTO MONDAY * ANOTHER SYSTEM POSSIBLE NEXT WED OR THURSDAY OVERVIEW... OVERALL 00Z GUIDANCE IS IN AGREEMENT SYNOPTICALLY. ACTIVE SPLIT-FLOW PATTERN OVER THE CONUS WILL TRANSITION TO A MORE AMPLIFIED RIDGE/TROUGH WITH A POSSIBLE NEGATIVELY TILT TROUGH SETTING UP OVER THE GREAT LAKES BY CHRISTMAS EVE. THIS IS THE BEGINNING OF THE PATTERN SHIFT WHICH COULD PUT THE REGION IN A MORE ACTIVE PATTERN FOR THE END OF THE MONTH. GUIDANCE TENDS TO HAVE ISSUES WITH THE PATTERN SHIFT AS WELL AS PHASING SO TIMING ON ANY SYSTEMS MAY SLOW DOWN OR EVEN SPEED UP. WHILE WE ARE IN TRANSITION...RIDGING WILL MOVE INTO THE REGION FRIDAY INTO SATURDAY. DIGGING SHORTWAVE ACROSS THE TENNESSEE VALLEY WILL DEVELOP A WEAK LOW PRESSURE SYSTEM BRINGING PRECIP TO THE AREA SUNDAY INTO MONDAY. ANOTHER STRONG TROUGH WILL DIG INTO THE SOUTHERN CONUS BRINGING ANOTHER LOW PRESSURE TOWARDS NEW ENGLAND AROUND THE CHRISTMAS TIMEFRAME. FOR NOW TRENDED TOWARDS THE ENSEMBLES FOR THIS FORECAST BECAUSE OF THE AMOUNT OF UNCERTAINTY. DETAILS... FRIDAY INTO SATURDAY...HIGH CONFIDENCE. AS UPPER LEVEL LOW SPINS INTO THE MARITIMES...HIGH PRESSURE WILL BUILD INTO SOUTHERN NEW ENGLAND. THIS WILL ALLOW FOR QUIET AND DRY WEATHER. TEMPERATURES WILL HOVER NEAR AVERAGE DURING THIS TIME PERIOD. ONSHORE FLOW SATURDAY NIGHT WITH APPROACHING SYSTEM FROM THE SOUTH MAY LEAD TO SOME DRIZZLE/FOG MOVING IN FROM THE OCEAN TO THE EAST MASS COASTLINE. SUNDAY INTO MONDAY...LOW CONFIDENCE. MAIN FOCUS OF THE FORECAST WAS ON THIS TRICKY TIME PERIOD. THE MODELS/ENSEMBLES HAVE OFFERED A VARIETY OF SOLUTIONS OVER THE PAST FEW DAYS FROM A VERY LOW AMPLITUDE AND FLAT WAVE MOVING THROUGH THE SOUTHEAST TO A WRAPPED UP SFC LOW HUGGING THE COAST INTO NEW ENGLAND. 00Z MODELS CONTINUE TO DO A SLIGHT SHIFT IN DEVELOPING THIS SYSTEM FAR ENOUGH OFFSHORE TO HAVE LOW IMPACTS ALONG THE COAST... BUT COULD THROW SOME LIGHT RAIN/SNOW BACK INTO THE MID- ATLANTIC/NORTHEAST AS IT EXITS INTO THE ATLANTIC. WILL NEED TO CONTINUE TO MONITOR THIS SYSTEM AS A FEW MEMBERS OF THE GEFS AS WELL AS THE CANADIAN AND ECMWF ENSEMBLES STILL SHOW THIS STORM NEAR THE BENCHMARK. RIGHT NOW APPEARS THAT MOISTURE WILL STREAM INTO THE REGION ON SUNDAY ALLOWING FOR LIGHT PRECIP WITH A CHANCE FOR MORE SHOWERS LATE SUNDAY INTO MONDAY. STILL A LOW CONFIDENCE AS EXACT TIMING OF THIS SYSTEM REMAINS IN QUESTION DUE TO HIGH MODEL SPREAD. TUESDAY AND BEYOND...LOW CONFIDENCE. ANTICIPATE DRY AIR TO WORK ITS WAY INTO THE REGION BEHIND THE DEPARTING SYSTEM ON TUESDAY. STRONG SHORTWAVE WILL DIG WELL INTO THE SOUTHERN CONUS EARLY NEXT WEEK DEVELOPING A STRONG LOW PRESSURE SYSTEM BY WEDNESDAY. WE COULD BEGIN TO SEE IMPACTS FROM THIS SYSTEM BY WEDNESDAY BUT EXACT DETAILS REMAIN UNCERTAIN. && .AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...
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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 THURSDAY NIGHT/...MODERATE CONFIDENCE. IFR CIGS/VSBYS HANGING TOUGH ACROSS E MA BUT SHOULD SLOWLY IMPROVE TO MVFR CIGS AS FOG DISSIPATES BY 21Z. ELSEWHERE MVFR CIGS SHOULD PREVAIL THROUGH EVENING. CIGS LIFT TO VFR ACROSS MOST OF AREA TONIGHT WITH INCREASING W/NW WINDS...GUSTING TO 25KT ESPECIALLY NEAR COAST. ALSO EXPECT SCATTERED RAIN/SNOW SHOWERS ESPECIALLY ACROSS NORTHERN MA WITH BRIEF MVFR CIGS/VSBYS. VFR CIGS DOMINATE THU AFTER LEFTOVER MVFR CIGS DURING MORNING... PERHAPS SCATTERED RAIN/SNOW SHOWERS ACROSS NE MA. NW WINDS GUST AS HIGH AS 25-30KT. KBOS TERMINAL...MODERATE CONFIDENCE. TIMING OF IMPROVEMENT TO MVFR MAY BE A LITTLE FAST...BUT WITH INCREASING NW FLOW SHOULD IMPROVE BEFORE EVENING PUSH /20-21Z/. KBDL TERMINAL...HIGH CONFIDENCE. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY... FRIDAY THROUGH SATURDAY...HIGH CONFIDENCE. VFR CONDITIONS EXPECTED. SUNDAY...LOW CONFIDENCE. DEVELOPING MVFR CONDITIONS ESP ACROSS THE EASTERN MASS COASTLINE.
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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. LOW PRESSURE WILL MOVE ACROSS SOUTHEAST NEW ENGLAND THIS MORNING AND LIFT INTO THE CANADIAN MARITIMES BY THURSDAY. THE RESULT WILL BE NORTHWEST WIND GUSTS OF 20 TO 30 KNOTS DEVELOPING THIS AFTERNOON AND CONTINUING INTO THURSDAY. A PERIOD OF 35 KNOT WIND GUSTS IS POSSIBLE ACROSS OUR EASTERN WATERS LATE TONIGHT INTO THU MORNING. WE FELT IT WAS TOO MARGINAL TO HOIST GALE WARNINGS AT THIS TIME...BUT LATER SHIFTS WILL HAVE TO RE-EXAMINE. OUTLOOK...THURSDAY NIGHT INTO SUNDAY...MODERATE TO HIGH CONFIDENCE. ANTICIPATE DIMINISHING WINDS AND SEAS SUBSIDING LATE THU NIGHT INTO SATURDAY LEADING TO BELOW SMALL CRAFT ADVISORY LEVELS. CONTINUE TO MONITOR THE POTENTIAL FOR A COASTAL STORM FOR SUNDAY INTO MONDAY. THERE IS A LARGE UNCERTAINTY IN THE TRACK AND INTENSITY OF THIS SYSTEM AND ANY CORRESPONDING IMPACT ON WINDS AND SEAS IN THE COASTAL WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST THURSDAY FOR ANZ232>235- 237. SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 7 PM EST THURSDAY FOR ANZ230-236. SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 7 PM EST THURSDAY FOR ANZ231-251. SMALL CRAFT ADVISORY UNTIL 7 PM EST THURSDAY FOR ANZ250- 254>256.
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&& $$ SYNOPSIS...FRANK/DUNTEN NEAR TERM...JWD SHORT TERM...FRANK LONG TERM...DUNTEN AVIATION...JWD MARINE...FRANK/DUNTEN

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