Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 240805 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 305 AM EST WED DEC 24 2014 .SYNOPSIS... STRONG LOW PRESSURE TRACKING ACROSS THE GREAT LAKES WILL BRING HEAVY RAIN...GUSTY WINDS AND MINOR COASTAL FLOODING TODAY INTO CHRISTMAS MORNING. DRY WEATHER WITH ABOVE NORMAL TEMPERATURES WILL FOLLOW FROM CHRISTMAS AFTERNOON INTO SAT. A COLD FRONT MAY BRING A FEW RAIN OR SNOW SHOWERS SUNDAY. ANOTHER STORM MAY AFFECT US LATE MONDAY INTO TUESDAY. && .NEAR TERM /THROUGH TODAY/... HIGH AMPLITUDE TROF OVER MS VALLEY LIFTS NE TO THE GT LAKES TODAY WITH DEEP SOUTHERLY FLOW ADVECTING ANOMALOUSLY HIGH PWATS EXCEEDING 1.5" INTO SNE BY EVENING. THIS IS 4-5 SD ABOVE NORMAL WHICH IS QUITE IMPRESSIVE. DEVELOPING LOW LEVEL JET 50-60 KT MOVES INTO SNE THIS AFTERNOON WHICH WILL RESULT IN AREAS OF DRIZZLE AND LIGHT RAIN THIS MORNING TRANSITIONING TO HEAVIER RAINFALL DURING THE AFTERNOON AS LOW LEVEL MOISTURE TRANSPORT/CONVERGENCE INCREASES. DESPITE THE LOW LEVEL JET...STRONG LOW LEVEL INVERSION N OF THE WARM FRONT WILL PREVENT STRONGER WINDS FROM MIXING DOWN WITH LIGHT NE WINDS IN THE INTERIOR. WINDS WILL GRADUALLY SHIFT TO SOUTH AFT 18Z ALONG THE S COAST AND COASTAL PLAIN AS THE WARM FRONT LIFTS NWD AND MAY SEE SOME GUSTY WINDS DEVELOP LATE IN THE DAY OVER THE ISLANDS AND IMMEDIATE S COAST. TEMPS WILL RISE THROUGH THE 50S ALONG THE S COAST AND COASTAL PLAIN THROUGH LATE AFTERNOON...BUT REMAIN IN THE 40S ACROSS THE DISTANT INTERIOR. && .SHORT TERM /TONIGHT/... *** LOCALLY HEAVY RAINFALL...ISOLATED TSTMS AND STRONG GUSTY WINDS IN THE COASTAL PLAIN *** PERIODS OF RAIN...LOCALLY HEAVY AT TIMES WILL CONTINUE TONIGHT BUT OF MORE CONCERN IS THE POTENTIAL FOR A FINE LINE OF CONVECTION ALONG THE COLD FRONT TO MOVE ACROSS SNE LATE TONIGHT TOWARD DAYBREAK CHRISTMAS MORNING WHICH WOULD BRING LOCALLY HEAVY RAINFALL RATES...STRONG WINDS AND ISOLATED TSTMS. MODELS SHOW A SECONDARY STRONGER LOW LEVEL JET MOVING UP FROM THE SOUTH LATE TONIGHT AHEAD OF THE COLD FRONT WHILE FORCING FROM UPPER LEVEL JET MOVES IN FROM THE WEST. INSTABILITY IS MARGINAL BUT NAM IS SHOWING SWI DROPPING NEAR OR SLIGHTLY BELOW ZERO AND THIS COMBINED WITH FRONTAL FORCING AND A LOW LEVEL JET SUGGESTS A POSSIBLE FINE LINE OF CONVECTION. SOME OF THE HI-RES MODELS ALSO SIGNALING A FINE LINE. RAINFALL... EXPECT 1-2 INCHES OF RAIN ACROSS THE REGION THROUGH CHRISTMAS MORNING. BUT GIVEN HIGH PWAT AIRMASS AND THE POTENTIAL FOR A FINE LINE WITH LOCALLY HEAVY CONVECTIVE ELEMENTS...COULD SEE LOCALIZED 3 INCH RAINFALL AMOUNTS. WE WILL CONTINUE THE FLOOD WATCH WITH MAIN THREAT BEING URBAN AND POOR DRAINAGE FLOODING. WE DO NOT ANTICIPATE ANY RIVER FLOODING. WIND THREAT... SECONDARY LOW LEVEL JET MOVES ACROSS MAINLY SE NEW ENGLAND 06-12Z. NAM IS STRONGEST WITH 65-70 KT DOWN TO 925 MB BUT GFS/ECMWF OVER 60 KT. NAM IS A BIT SLOWER WITH THE TIMING OF THE LLJ EXITING CAPE/ISLANDS THU MORNING. SOUNDINGS SHOW PRONOUNCED LOW LEVEL INVERSION OVER THE WATERS WHICH WILL LIKELY PREVENT STRONGER WINDS FROM MIXING DOWN NEAR THE IMMEDIATE S COAST AND ISLANDS. HOWEVER...LATER TONIGHT INVERSION WEAKENS WITH NEAR ISOTHERMAL PROFILE IN THE LOW LEVELS JUST INLAND FROM THE COAST. BEST CHANCE FOR SEEING GUSTS TO 40-50 MPH WILL BE ACROSS SE MA AND PORTIONS OF RI WHERE TEMPS WILL LIKELY RISE INTO LOWER 60S OVERNIGHT ENHANCING MIXING POTENTIAL. IN ADDITION...ANY FINE LINE LATE TONIGHT WOULD HELP TO BRING DOWN STRONGER WIND GUSTS. WE ISSUED A WIND ADVISORY FOR LATER TONIGHT FOR SE RI AND SE MA INCLUDING THE CAPE/ISLANDS. TEMPS RISE THROUGH THE 50S TONIGHT AND INTO THE LOWER 60S FOR PORTIONS OF RI AND SE MA. MAY EVEN SEE DEWPOINTS NEAR 60 DEGREES IN SE MA OVERNIGHT WHICH IS PRETTY REMARKABLE FOR LATE DECEMBER. && .LONG TERM /THURSDAY THROUGH TUESDAY/... HIGHLIGHTS... * DRY AND WINDY CHRISTMAS AFTERNOON WITH GUSTS TO 45 MPH POSSIBLE * CONTINUED DRY WITH ABOVE NORMAL TEMPERATURES FRI AND SAT * A STORM MAY AFFECT THE REGION SUNDAY NIGHT INTO MON...BUT CONFIDENCE IS LOW OVERVIEW... MODELS CONTINUE TO EXHIBIT GOOD OVERALL AGREEMENT INTO FRIDAY. AFTER THAT TIME..THE ECMWF CONTINUES TO MAINTAIN A SHARPER MID LEVEL TROUGH OVER THE CENTRAL USA, THIS TROUGH WOULD RESULT IN A STORM TRACK CLOSER TO SOUTHERN NEW ENGLAND EARLY NEXT WEEK. THAT SAID...JUST ABOUT ALL GUIDANCE IS INDICATING AT LEAST SOME POTENTIAL FOR A PERIOD OF WET WEATHER EARLY NEXT WEEK. HAVE LOW CONFIDENCE IN THE DETAILS OF STORM TRACK EARLY NEXT WEEK. WILL KEEP A CHANCE OF SHOWERS IN THE FORECAST LATE SUNDAY INTO MONDAY UNTIL THIS CRITICAL DETAIL CAN COME INTO BETTER FOCUS. CHRISTMAS DAY...HEAVY RAIN WILL LIKELY BE ONGOING CHRISTMAS MORNING ACROSS THE COASTAL PLAIN. RAIN THEN MOVES OUT BY MIDDAY WITH SKIES BECOMING CLEARER IN THE AFTERNOON. GUSTY SOUTHWEST WINDS IN THE MORNING NEAR THE COAST ASSOCIATED WITH THE LOW-LEVEL JET AND HEAVIER RAINFALL. ALL AREAS WILL SEE STRONG WEST WIND GUSTS IN THE AFTERNOON AS COLD ADVECTION DEVELOPS WITH STEEPENING LOW LEVEL LAPSE RATES. WIND GUSTS TO 45 MPH WILL BE POSSIBLE AND WIND ADVISORIES MAY BE NEEDED. MAX TEMPERATURES IN THE 50S TO NEAR 60 DEGREES WILL OCCUR IN THE MORNING...WITH TEMPS FALLING DURING THE AFTERNOON. FRIDAY INTO SAT... HIGH PRESSURE CENTERED TO OUR SOUTH BRINGS DRY WEATHER WITH ABOVE NORMAL TEMPERATURES. THE MILDER DAY WILL BE SATURDAY. SUNDAY INTO TUESDAY...LOW CONFIDENCE FORECAST. A COLD FRONT MAY BRING A FEW RAIN/SNOW SHOWERS SUNDAY. WE WILL THEN HAVE TO WATCH FOR POSSIBLE FRONTAL WAVE SUNDAY NIGHT INTO MONDAY. THIS WAVE MAY END UP TOO FAR SOUTH BUT WILL KEEP LOW POPS IN THE FORECAST. SOME OF THE GUIDANCE...MOST NOTABLY THE ECMWF...KEEPS A LOW PRESSURE NEAR OUR REGION INTO TUESDAY MORNING. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TONIGHT/...MODERATE CONFIDENCE. THROUGH 12Z...WIDESPREAD IFR/LIFR CONDITIONS IN STRATUS...DRIZZLE AND FOG. TODAY AND TONIGHT...WIDESPREAD IFR/LIFR CONDITIONS CONTINUE WITH RAIN OVERSPREADING THE REGION LATER THIS MORNING THROUGH THE AFTERNOON AND CONTINUING TONIGHT. A BAND OF LOCALLY HEAVY SHOWERS AND ISOLATED THUNDERSTORMS WITH POTENTIALLY STRONG WINDS MAY MOVE ACROSS THE REGION 09-12Z. LOW LEVEL WIND SHEAR WILL DEVELOP LATE TODAY AND THIS EVENING AS 2000 FT WINDS INCREASE TO 40-50 KT. THE LLWS WILL SHIFT TO SE NEW ENGLAND LATE TONIGHT WITH 2000 FT WINDS INCREASING TO 60 KT. KBOS TERMINAL...HIGH CONFIDENCE IN IFR/LIFR CONDITIONS. KBDL TERMINAL...HIGH CONFIDENCE IN IFR/LIFR CONDITIONS. OUTLOOK...THURSDAY THROUGH SUNDAY... CHRISTMAS...MODERATE CONFIDENCE. IFR IN RAIN TO START...THEN CONDITIONS IMPROVE TO VFR IN THE AFTERNOON FROM WEST TO EAST. WEST WIND GUSTS TO 35-40 KT POSSIBLE IN THE AFTERNOON. FRIDAY AND SATURDAY...HIGH CONFIDENCE. VFR. SUNDAY...MODERATE CONFIDENCE. MAINLY VFR. SCATTERED MVFR IN SHOWERS AS A COLD FRONT PASSES THROUGH. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TONIGHT/...HIGH CONFIDENCE. TODAY...SOUTH WINDS GRADUALLY INCREASE LATER THIS AFTERNOON WITH GUSTS POSSIBLY REACHING 25-30 KT BY LATE IN THE DAY...MAINLY FOR S COASTAL WATERS. POOR VSBYS IN RAIN AND FOG. TONIGHT...LOW LEVEL JET STRENGTHENS OVERNIGHT BUT VERY STRONG LOW LEVEL INVERSION WILL LIKELY PREVENT THESE WINDS FROM MIXING DOWN TO THE OCEAN SURFACE. IN FACT...WINDS WILL LIKELY REMAIN BELOW GALE FORCE ACROSS THE WATERS WITH GUSTS TO 30 KT. HOWEVER...WE DO EXPECT GALE FORCE GUSTS IN NARRAGANSETT BAY WHERE MIXING WILL BE BETTER SO WE ISSUED A GALE WARNING HERE. POOR VSBYS IN RAIN AND FOG WITH ISOLATED TSTMS POSSIBLE OVERNIGHT. OUTLOOK...THURSDAY THROUGH SUNDAY...MODERATE CONFIDENCE CHRISTMAS...WINDS SHIFT TO SW/W WITH GALE FORCE GUSTS POSSIBLE. IMPROVING VSBYS IN THE AFTERNOON AS RAIN MOVES OUT. FRI AND SAT...EXPECT WEST WINDS BELOW SMALL CRAFT ADVISORY LEVELS FRI. INCREASING SOUTHWEST WINDS SAT WITH GUSTS TO 25 KT. SUNDAY...WEST TO NORTHWEST WINDS MAY GUST TO 25 KT ACROSS THE OUTER COASTAL WATERS. MAY ALSO SEE 5 FOOT SEAS ACROSS THE OUTER COASTAL WATERS AS WELL. && .TIDES/COASTAL FLOODING... EASTERN MASSACHUSETTS COAST... HIGH TIDE AT BOSTON WILL BE 11.7 FT AROUND MIDDAY WITH A SURGE OF AROUND 1.0 FT WHICH WILL LIKELY RESULT IN MINOR SPLASHOVER. A COASTAL FLOOD ADVISORY REMAINS IN EFFECT FOR THE MIDDAY HIGH TIDE. SOUTH COAST: WE DO NOT EXPECT MUCH IF ANY COASTAL FLOODING ALONG THE SOUTH COAST. SURGE OF 1 TO 1.5 FT EXPECTED FOR THIS EVENINGS HIGH TIDE WHICH FALLS SHORT OF WHAT IS NEEDED TO BEGIN COASTAL FLOODING. FOR THE CHRISTMAS MORNING HIGH TIDE...WINDS ARE SHIFTING TO SW/W AND SURGE IS DECREASING SO THREAT IS MINIMAL. && .CLIMATE... RECORD HIGHS FOR DEC 24 / DEC 25... BOS...61 IN 1996 / 65 IN 1889 PVD...60 IN 1990 / 63 IN 1964 BDL...59 IN 1996 / 64 IN 1964 ORH...57 IN 1996 / 60 IN 1964 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...FLOOD WATCH FROM THIS AFTERNOON THROUGH THURSDAY MORNING FOR CTZ002>004. MA...FLOOD WATCH FROM THIS AFTERNOON THROUGH THURSDAY MORNING FOR MAZ002>022-026. WIND ADVISORY FROM 10 PM THIS EVENING TO 7 AM EST THURSDAY FOR MAZ013-016>021. COASTAL FLOOD ADVISORY FROM 9 AM THIS MORNING TO 4 PM EST THIS AFTERNOON FOR MAZ007-014>016-019-022. WIND ADVISORY FROM 1 AM TO 9 AM EST THURSDAY FOR MAZ022>024. RI...FLOOD WATCH FROM THIS AFTERNOON THROUGH THURSDAY MORNING FOR RIZ001>007. WIND ADVISORY FROM 10 PM THIS EVENING TO 7 AM EST THURSDAY FOR RIZ002-004-005-007. MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM EST THURSDAY FOR ANZ231>234. GALE WARNING FROM 10 PM THIS EVENING TO 7 AM EST THURSDAY FOR ANZ236. SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 6 AM EST THURSDAY FOR ANZ235-237. SMALL CRAFT ADVISORY UNTIL 6 AM EST THURSDAY FOR ANZ250-251- 254>256. && $$ SYNOPSIS...KJC/JWD NEAR TERM...KJC SHORT TERM...KJC LONG TERM...JWD AVIATION...KJC/JWD MARINE...KJC/JWD TIDES/COASTAL FLOODING...KJC CLIMATE...STAFF

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