Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 271744 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1244 PM EST THU NOV 27 2014 .SYNOPSIS... SCATTERED LIGHT SNOW SHOWERS OR FLURRIES WILL DEVELOP THROUGH THIS AFTERNOON ACROSS THE REGION. A TROUGH OF LOW PRESSURE MAY PRODUCE ACCUMULATING SNOW ACROSS EASTERN MA INCLUDING THE BOSTON AREA LATE TONIGHT INTO FRI. ELSEWHERE JUST LIGHT SNOW OR FLURRIES ARE EXPECTED. DRY BUT COLD WEATHER FOLLOWS FRI NIGHT INTO SAT BEFORE MORE LIGHT SNOW OR FLURRIES SAT NIGHT. DRY AND MILDER WEATHER ARRIVES SUN AND INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1245 PM UPDATE...FLURRIES AND SNOW SHOWERS ARE A BIT SLOWER TO MOVE INTO SOUTHERN NEW ENGLAND THAN PREVIOUSLY THOUGHT BUT ARE STILL EXPECTED TO MOVE INTO THE REGION LATER ON THIS AFTERNOON. OTHERWISE...ONLY MINOR UPDATES WERE MADE. PREVIOUS DISCUSSION BELOW... LEFTOVER LIGHT SNOW FROM THE EXITING LOW PRES HEADING NE OUT OF THE GULF OF MAINE CONTINUES ACROSS S NH/N CENTRAL AND E MA WHILE A MIX OF LIGHT RAIN AND SNOW REPORTED ON CAPE COD AND THE ISLANDS AT 09Z. NE REGIONAL 88D RADAR SHOWING THE LIGHT PRECIP MOVING INTO NORTHERN NEW ENGLAND...THOUGH A FEW SPOTS HANGING IN ACROSS E MA. SHOULD SEE PRECIP END OVER THE NEXT FEW HOURS. FOR TODAY...EXPECT A BRIEF BREAK IN THE ACTION AS WEAK HIGH PRES RIDGE BUILDS ACROSS BY AROUND MIDDAY. MAY SEE SOME BRIGHTENING OF THE SKY AS LOWER CLOUDS MOVE OUT. HOWEVER...H5 LONG WAVE TROUGH REMAINS W OF THE REGION AND WILL BEGIN TO SHIFT E THIS AFTERNOON. WEAK SURFACE REFLECTION OF AN H5 S/W MOVING AROUND THE BASE OF THE LONG WAVE TROUGH ACROSS WESTERN NC/VA WILL ROTATE OFF THE COAST THIS AFTERNOON THEN PUSH NE. AS IT MOVES ACROSS THE ATLC...WILL PICK UP SOME MOISTURE ALONG WITH THE ASSOCIATED LIFT AND BRING THEM INTO THE REGION. BY SUNSET...NOTING THE TROUGH IS SHOWING SOME GOOD CYCLONIC SPIN AS IT APPROACHES NEW ENGLAND WITH NEGATIVE TILT TROUGHING ON THE BACKSIDE. HAVE MENTIONED SLIGHT CHANCE TO LOW CHANCE POPS FOR THIS AFTERNOON BUT NOT A LOT OF QPF ASSOCIATED WITH THIS SO WILL SEE LIGHT RAIN AND/OR SNOW SHOWERS. COLDER AIR CONTINUES TO FILTER ACROSS...WITH H85 TEMPS DROPPING TO -5C TO -8C BY THE END OF THE DAY. EXPECT HIGHS ONLY IN THE MID 30S TO LOWER 40S.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... TONIGHT... NEG TILT TROUGHING SHIFTS E DURING THE NIGHT AS LONG WAVE TROUGH APPROACHES...KEEPING LOW LEVEL CLOUDS AND MOISTURE ACROSS THE REGION. THIS TROUGH WILL BEGIN TO SET UP ACROSS CENTRAL AND EASTERN AREAS...SO LOOKS LIKE DECENT SHOT FOR PRECIP THOUGH REMAINS LIGHT ACROSS WESTERN AREAS. DEPENDING UPON WHERE THIS TROUGH SETS UP...IT COULD BRING IN SOME MORE LOW LEVEL MOISTURE OFF THE OCEAN. 00Z AND 06Z NAM AND GFS BOTH SHOWING THIS RATHER WELL. MAY SEE JUST ENOUGH LOW LEVEL CONVERGENCE TO BRING ROUND OF LIGHT RAIN AND/OR SNOW ESPECIALLY ACROSS E MA/RI. BIG QUESTION WILL BE HOW MUCH MOISTURE WILL WORK IN. 06Z GFS SHOWING ABOUT 1/4 INCH QPF SO...DEPENDING UPON HOW MUCH ENERGY GETS GOING DUE TO THE COLD AIR WORKING OVER THE ABOVE NORMAL COASTAL WATERS...COULD SEE A PERIOD OF DECENT SNOWFALL MAINLY AFTER MIDNIGHT IN THE AREA OF CONVERGENCE. THIS SITUATION WILL BE MONITORED VERY CLOSELY. MORE DETAILS ON THIS IN THE LONG TERM SECTION. COLD AIR CONTINUES TO FILTER IN...WITH LOWS DROPPING TO THE 20S...THOUGH HOLDING BETWEEN 30 AND 35 ON THE OUTER CAPE AND NANTUCKET CLOSER TO THE MILDER WATERS. && .LONG TERM /FRIDAY THROUGH THURSDAY/... UPDATED 430 AM *** ACCUMULATING SNOW POSSIBLE LATE TONIGHT INTO EARLY FRI AFTERNOON ACROSS EASTERN MA FROM CAPE ANN TO BOSTON TO CAPE COD *** FRIDAY... INTERESTING SETUP FOR POSSIBLE NORLUN TYPE TROUGH ALONG THE EASTERN MA COASTLINE FROM CAPE ANN SOUTHWARD THROUGH THE CITY OF BOSTON... PLYMOUTH COUNTY TO CAPE COD TONIGHT INTO EARLY FRI AFTERNOON. ROBUST NORTHERN STREAM TROUGH MOVES ACROSS THE AREA TONIGHT AND FRI... INDUCING AN INVERTED TROUGH FROM OFFSHORE LOW NORTHWESTWARD BACK INTO EASTERN NEW ENGLAND. THE MID LEVEL TROUGH WILL PROVIDE MODEST SYNOPTIC SCALE LIFT AND WILL COMBINE WITH MESOSCALE FRONTAL SCALE FORCING FROM THE INVERTED TROUGH TO YIELD A NARROW BAND OF MODEST/APPRECIABLE QPF. BOTH THE NAM /00Z AND 06Z/ AND GFS HAVE AN AXIS OF QPF UP TO 0.25 INCHES FROM CAPE ANN SOUTHWARD INTO BOSTON AND THROUGH COASTAL PLYMOUTH COUNTY. EMBEDDED IN THIS AREA OF QPF IS A BULLSEYE OF 0.50 TO 0.60 INCHES OVER THE OUTER CAPE. ABOVE AVERAGE CONFIDENCE IN THIS QPF AS LOW LEVEL STREAMLINE ANALYSIS INDICATES STRONG CONVERGENCE VICINITY OF THE INVERTED TROUGH ALONG WITH STEEP LAPSE RATES AND NEARLY SATURATED WITHIN AND ABOVE THE AREA OF ASCENT. THUS THE FORCING SHOULD HAVE A STRONG RESPONSE AS INSTABILITY WILL BE REALIZED. IN ADDITION BUFKIT TIME SECTIONS FROM THE NAM AND GFS BOTH SUGGEST AT LEAST SOME OF THE LIFT WILL OCCUR IN THE DENDRITIC SNOW GROWTH REGION WHICH MAY PROVIDE A BIT OF BOOST TO SNOW TO LIQUID RATIOS...SAY 12-1 TO 15-1. PTYPE WILL BE SNOW AS TEMPS ALOFT ARE COLD FAIRLY COLD...-8C AT 850 MB BY 12Z FRI. HOWEVER ACROSS THE OUTER CAPE /EAST OF HYA/... DESPITE A NNE WIND BACKING TO NNW THIS SURFACE WIND TRAJECTORY WILL BE CROSSING OVER WATER TEMPS OF 45-50. BUFKIT SOUNDINGS INDICATE THIS BLYR WARMTH...WHICH MAY PARTIALLY ERODE VIA MODERATE TO HEAVY PRECIP /DYNAMICAL AND DIABATIC COOLING/. HOWEVER SNOW MAY STRUGGLE TO ACCUMULATE ON PAVED SURFACES HERE. SO WITH ALL OF THIS IN MIND THERE IS A MODERATE RISK /30-60 PERCENT/ OF ACCUMULATING SNOW ACROSS EASTERN MA LATE TONIGHT INTO EARLY FRI AFTERNOON. GIVEN MODEL QPF EARLY INDICATIONS ARE FOR A MODERATE RISK OF 2-4 INCHES OF SNOW...EXCEPT LESS ON THE OUTER CAPE GIVEN MARGINAL SURFACE TEMPS. LOW RISK /LESS THAN 30 PERCENT/ OF UP TO 6 INCHES OR SO IF INVERTED TROUGH LINGERS LONG ENOUGH OVER EASTERN MA. HOWEVER THESE INVERTED/NORLUN TROUGHS ARE VERY DIFFICULT TO PINPOINT ESPECIALLY 30-42 HRS IN ADVANCE. FOR EXAMPLE IF THE INVERTED TROUGH SHIFTS 25 MILES OR SO FARTHER EAST MOST OF THE SNOW WILL REMAIN OFFSHORE. THUS BIG BUST POTENTIAL. FORECAST CONFIDENCE NOT HIGH ENOUGH TO ISSUE A WINTER STORM WATCH AND STILL TOO MUCH UNCERTAINTY FOR AN ADVISORY. THUS TO HEIGHTEN PUBLIC AWARENESS AND CONVEY THE UNCERTAINTY WILL ISSUE A SPECIAL WEATHER STATEMENT. IT WON/T TAKE MUCH FOR THIS EVENT TO HAVE SOME IMPACT GIVEN THE NUMBER OF HOLIDAY TRAVELERS/SHOPPERS ON THE ROADS TONIGHT AND FRIDAY MORNING. SO STAY TUNED TO LATER FORECASTS AND DISCUSSIONS. THIS WEEKEND... QUIET AND COLD EARLY SAT THEN INCREASING CLOUDS WITH A CHANCE OF LIGHT SNOW OR FLURRIES LATE IN THE DAY OR AT NIGHT AS WEAK WAA PATTERN SETS UP. BY SUNDAY WARM FRONT LIFTS NORTH OF THE AREA WITH MILDER TEMPS...U40S TO L50S. NEXT WEEK... MILD TO START THE WEEK WITH HIGHS 50-55 MONDAY AHEAD OF AN APPROACHING COLD FRONT. CHANCE OF SHOWERS LATE MON/MON NIGHT AHEAD OF POLAR FRONT. MUCH COLDER TUE WITH 1040 MB HIGH OVER QUEBEC. NEXT CHANCE OF PRECIP MIDDLE OF NEXT WEEK AS WAA PATTERN SETS UP. COULD BE SOME MIXED PRECIP AS COLD AIRMASS MAY BE SLOW TO ERODE/DISLODGE. && .AVIATION /18Z THURSDAY 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 /THROUGH FRIDAY/...MODERATE CONFIDENCE. THROUGH 00Z...A MIX OF CIGS ACROSS THE AREA THOUGH MOSTLY VFR/MVFR. IFR CIGS ON THE OUTER CAPE. -SHSN MOVE INTO SOUTHERN NEW ENGLAND FROM NYS THROUGH THE AFTERNOON. TONIGHT...MVFR CIGS MOVE ACROSS THE REGION. PRECIP DEVELOPS ACROSS E MA INTO RI...POSSIBLY AS FAR W AS KORH-KIJD...AS INVERTED TROUGH TAKES SHAPE NEAR THE COAST AFTER 06Z. 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. FRIDAY...SNOW/RAIN SHOWERS WILL CONTINUE THROUGH MID-MORNING ALONG THE E COAST OF MASS...POSSIBLY AS FAR INLAND AS ORH-IJD. PRECIP COMES TO AN END AFTER NOON AND CONDITIONS WILL IMPROVE TO VFR BY FRIDAY EVENING. KBOS TERMINAL...HIGH CONFIDENCE TODAY...LOWER CONFIDENCE TONIGHT IN EXACT TIMING AS PRECIP DEVELOPS. KBDL TERMINAL...HIGH CONFIDENCE. OUTLOOK...SATURDAY THROUGH MONDAY...MODERATE CONFIDENCE. SATURDAY-SUNDAY...VFR WITH POTENTIAL MVFR LATE SAT/SAT NIGHT IN A PERIOD OF LIGHT SNOW OR FLURRIES. ALSO 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/...MODERATE TO HIGH CONFIDENCE. TODAY...EXPECT LIGHT WINDS BUT SEAS WILL REMAIN HIGH. SMALL CRAFT ADVISORIES ARE UP FOR SEAS THROUGH TONIGHT. TONIGHT...LEFTOVER SMALL CRAFT SEAS SHOULD SUBSIDE...THOUGH MAY LINGER ON THE OUTER WATERS. VSBYS WILL LOWER IN AREAS OF SNOW AND/OR RAIN WITH SOME PATCHY FOG. OUTLOOK...FRIDAY THROUGH MONDAY...MODERATE CONFIDENCE. UPDATED 430 AM FRIDAY...LOW VSBY POSSIBLE IN SNOW ACROSS EASTERN MA WATERS. SNOW NEAR SHORE WITH RAIN OFFSHORE. VSBY IMPROVING IN THE AFTERNOON AND ESPECIALLY AT NIGHT. 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. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR ANZ231- 232. SMALL CRAFT ADVISORY UNTIL 9 PM EST THIS EVENING FOR ANZ235- 237. SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR ANZ250-251. SMALL CRAFT ADVISORY UNTIL 6 AM EST FRIDAY FOR ANZ254>256. && $$ SYNOPSIS...NOCERA/EVT NEAR TERM...NOCERA/RLG/EVT SHORT TERM...EVT LONG TERM...NOCERA AVIATION...NOCERA/RLG/EVT MARINE...NOCERA/EVT

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