Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 240808 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 308 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 /UNTIL 6 PM THIS EVENING/... 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 /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... *** 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/... * CLEARING...WINDY AND MILD CHRISTMAS DAY. * REMAINING DRY WITH ABOVE NORMAL TEMPERATURES FRI AND SAT. * POTENTIAL FOR SOME RAIN OR SNOW EARLY NEXT WEEK. CHRISTMAS DAY...HIGH CONFIDENCE. COLD FRONT WILL BE PUSHING OFFSHORE FIRST THING IN MORNING AND TAKING ANY LEFTOVER SHOWERS WITH IT. EXPECT RAPID DRYING ON INCREASING W/SW WINDS BY AFTERNOON WHICH WILL BRING CLEARING SKIES...BUT STEEPENING LAPSE RATES WILL ALSO BRING ROUND OF GUSTY WINDS. FORECAST SOUNDINGS FROM NAM AND GFS SHOW POTENTIAL 35-40 MPH GUSTS WHICH IS SHORT OF WIND ADVISORY CRITERIA. BEST MIXING OCCURS THU AFTERNOON. AIRMASS BEHIND FRONT IS FROM PACIFIC SO WE WILL NOT SEE ANY KIND OF COOL DOWN...AND IN FACT DOWNSLOPE W FLOW SHOULD LEAD TO SOME ADDITIONAL WARMING NEAR COAST WHICH WOULD OFFSET ANY COOL ADVECTION. NONETHELESS HIGHS SHOULD OCCUR IN MORNING BEFORE TEMPERATURES DROP OFF A BIT IN AFTERNOON. FRIDAY AND SATURDAY...MODERATE CONFIDENCE. HIGH PRESSURE BUILDS TO MID ATLANTIC COAST. DRY WEATHER WILL PREVAIL WITH LIGHTER WINDS. TEMPERATURES WILL REMAIN ABOVE AVERAGE WITH HIGHS IN 40S BOTH DAYS AND LOWS MAINLY IN 30S. SUNDAY THROUGH TUESDAY...LOW CONFIDENCE. MODELS DROP A WEAK COLD FRONT THROUGH SOUTHERN NEW ENGLAND SUN. MOISTURE APPEARS TO BE LIMITED AND CONVERGENCE RATHER WEAK...SO ONLY EXPECTING WIDELY SCATTERED RAIN SHOWERS AS IT MOVES THROUGH. TEMPERATURE PROFILES MAY BE COLD ENOUGH FOR SOME WET SNOW TO MIX IN ACROSS HIGHER TERRAIN IN W MA. FROM THERE...MODELS STRUGGLE WITH STRENGTH AND POSITION OF UPPER TROUGH HEADING E FROM SOUTHERN PLAINS. RIDGE OFF SE COAST HOLDS ITS OWN AND LEADS TO DIFFICULTIES IN HOW NORTHERN AND SOUTHERN STREAMS INTERACT ACROSS CENTER OF COUNTRY. 00Z ECMWF MAINTAINS MORE SOUTHERN STREAM ENERGY AND MAINTAINS MORE SEPARATION THAN GFS WHICH HAS BROADER TROUGH BY MIDDLE OF NEXT WEEK. THIS HAS IMPACT ON DEVELOPMENT OF LOW PRESSURE ALONG FRONT TO OUR S...NAMELY HOW FAR N IT BRINGS ITS PRECIPITATION SHIELD. MODELS HAVE CERTAINLY SHOWN SIGNIFICANT RUN-TO-RUN VARIATION OVER PAST DAY OR TWO EITHER COMPLETELY SUPPRESSING SYSTEM TO OUR S OR BRINGING IT DIRECTLY OVER SOUTHERN NEW ENGLAND. THERE HAVE ALSO BEEN VARIATIONS IN HAVING ONE LOW PRESSURE SYSTEM OR A SERIES OF TWO WEAKER LOWS. LEANED TOWARD MODEL BLEND TO HELP IRON OUT THESE DIFFERENCES FOR NOW WHICH BRINGS CHANCE POPS TO MOST OF AREA...ESPECIALLY S OF MASS PIKE. THERMAL PROFILES SUGGEST AT LEAST SOME LIGHT SNOW IN MON/TUE TIMEFRAME WITH RAIN MORE LIKELY CLOSER TO S COAST. ALTHOUGH THIS IS SEVERAL DAYS AWAY AND CONFIDENCE IS LOW IN DETAILS...LOW LEVEL TEMPERATURES LOOK A BIT WARM FOR ANY SIGNIFICANT ACCUMULATIONS...ESPECIALLY FROM MASS PIKE TO S COAST. BUT WE NEED TO SEE HOW LARGER SCALE FEATURES WILL BE RESOLVED OVER NEXT FEW DAYS. && .AVIATION /08Z 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. THURSDAY...MODERATE CONFIDENCE. CONDITIONS IMPROVE TO VFR BY AFTERNOON. W WINDS GUST TO 35KT THU AFTERNOON. FRIDAY AND SATURDAY...HIGH CONFIDENCE. VFR. SUNDAY...MODERATE CONFIDENCE. MVFR POSSIBLE IN ISOLATED RAIN SHOWERS. && .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. COLD FRONT PUSHES OFFSHORE THU MORNING FOLLOWED BY INCREASING W/SW WINDS...WHICH SHOULD PEAK AT GALE FORCE /35KT/ FROM LATE MORNING INTO THU EVENING. GALE WATCHES HAVE BEEN POSTED FOR ALL WATERS. WINDS GRADUALLY DIMINISH THU NIGHT AND FRI WITH SEAS ALSO SUBSIDING DURING THAT TIME AS HIGH PRESSURE BUILDS OVER MID ATLANTIC STATES. WEAKENING COLD FRONT MAY BRING AN ISOLATED SHOWER AS IT DROPS THROUGH NEW ENGLAND SUN...BUT WINDS AND SEAS SHOULD REMAIN BELOW SCA. && .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 TODAY / CHRISTMAS DAY 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...GALE WATCH FROM THURSDAY MORNING THROUGH THURSDAY EVENING FOR ANZ232>235-237-254>256. SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 10 AM EST THURSDAY FOR ANZ231>234. GALE WATCH FROM THURSDAY MORNING THROUGH THURSDAY EVENING FOR ANZ230-231-250-251. GALE WARNING FROM 10 PM THIS EVENING TO 7 AM EST THURSDAY FOR ANZ236. SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 10 AM EST THURSDAY FOR ANZ235-237. SMALL CRAFT ADVISORY UNTIL 10 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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