Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 230858 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 358 AM EST TUE DEC 23 2014 .SYNOPSIS... WEAK LOW PRESSURE MOVING UP THE COAST WILL BRING PERIODS OF RAIN TODAY AND EARLY TONIGHT. A MUCH STRONGER STORM TRACKING ACROSS THE GREAT LAKES WILL BRING HEAVY RAIN...GUSTY WINDS AND MINOR COASTAL FLOODING WEDNESDAY 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 THEN A STORM MAY AFFECT THE REGION SUN NIGHT INTO MON...BUT IT COULD ALSO PASS WELL TO THE SOUTH. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 4 AM UPDATE... RAIN LIFTING NE LOOKS MUCH MORE FRAGMENTED THAN WHAT MOST OF 00Z MODELS INDICATED...IN FACT HIGH-RES MODELS MAY HAVE RIGHT IDEA THAT WE WILL SEE MORE IN WAY OF PERIODS OF RAIN TODAY RATHER THAN ALL-DAY SOAKING. TEMPERATURES ACROSS INTERIOR HAVE ALREADY RISEN ABOVE FREEZING SO WE ARE NO LONGER CONCERNED ABOUT POTENTIAL OF ANY ICING. OTHERWISE CLOUDY DAY IN STORE WITH INCREASING E WINDS NEAR COAST...GUSTING TO 25 MPH AT TIMES. SHOULD SEE PATCHES OF RAIN DIMINISH LATER THIS AFTERNOON AS LOW PRESSURE APPROACHES S COAST BUT EXPECT AREAS OF FOG AND PATCHY DRIZZLE TO PERSIST. HIGHS TODAY WILL RANGE FROM AROUND 40 IN NW MA TO MID/UPPER 40S ELSEWHERE. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... WEAK LOW PRESSURE TRACKS THROUGH SE NEW ENGLAND TONIGHT. MODELS SHOW MOST OF LIFT REMAINING TO OUR N AND W BUT WITH CONTINUED ONSHORE FLOW AND DEEP MOISTURE...EXPECT AREAS OF FOG/DRIZZLE THROUGH MOST OF NIGHT. TEMPERATURES SHOULD ONLY FALL BACK FEW DEGREES...INTO UPPER 30S NW TO MID 40S SE. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... HIGHLIGHTS... * RAIN...HEAVY AT TIMES AND UNSEASONABLY MILD WEDNESDAY INTO CHRISTMAS MORNING WITH GUSTY SOUTH WINDS IN THE COASTAL PLAIN WED NIGHT * DRY AND WINDY CHRISTMAS AFTERNOON WITH GUSTS TO 45 MPH POSSIBLE * CONTINUED DRY WITH ABOVE NORMAL TEMPS FRI AND SAT * A STORM MAY AFFECT THE REGION SUN NIGHT INTO MON...BUT CONFIDENCE IS LOW OVERVIEW... HIGH AMPLITUDE TROF OVER THE MS VALLEY ON WED LIFTS NE THROUGH THE GT LAKES AND INTO CANADA BY CHRISTMAS DAY. DEEP SOUTHERLY FLOW AND ANOMALOUS PWAT AIRMASS AHEAD OF THE TROF WILL BRING A PERIOD OF HEAVY RAINFALL TO THE REGION WED AND WED NIGHT BEFORE DRYING OUT CHRISTMAS AFTERNOON. BEYOND CHRISTMAS...MODELS IN AGREEMENT ON ANOMALOUSLY STRONG MID LEVEL RIDGE OVER THE SE US FRI THROUGH THE WEEKEND WHICH WILL RESULT IN CONTINUED MILD CONDITIONS. BY SUNDAY...NORTHERN STREAM SHORTWAVE DELIVERS A COLD FRONT...THEN THERE IS QUITE A BIT OF UNCERTAINTY REGARDING A SOUTHERN STREAM SHORTWAVE EJECTING NE FROM SOUTHERN PLAINS TROF WITH POSSIBLE FRONTAL WAVE SUN NIGHT INTO MON. PREVIOUS RUNS OF THE ECMWF SHOWED A MORE AMPLIFIED SHORTWAVE AND FRONTAL WAVE...BUT LATEST RUN OF THE ECMWF HAS TRENDED FLATTER AND MORE SUPPRESSED ALTHOUGH IT STILL BRINGS SOME SNOW SUN NIGHT INTO MON. GFS CONTINUES TO BE WELL SUPPRESSED WITH THE WAVE WITH HIGH PRES DOMINATING. DUE TO UNCERTAINTY...WE USED A BLEND OF ECMWF/GFS WEDNESDAY INTO WEDNESDAY NIGHT... DEEP SOUTHERLY FLOW WILL BRING ANOMALOUS HIGH PWAT AIRMASS INTO SNE BY WED NIGHT WITH PWATS NEARING 1.75" AND 850 MB DEWPOINTS NEAR 12C WHICH IS PRETTY REMARKABLE FOR LATE DECEMBER. PWATS ARE 4-5 SD ABOVE NORMAL WHICH IS QUITE IMPRESSIVE AND SIGNALS THREAT FOR HEAVY RAINFALL. HOWEVER...850 MB WIND ANOMALIES ARE NOT AS IMPRESSIVE...NEAR 2 SD ABOVE NORMAL WHICH WILL LIKELY BE A LIMITATION TO EXCESSIVE RAINFALL THREAT. IN ADDITION INDIVIDUAL GEFS MEMBERS ARE ALL BELOW 2" QPF. WE ARE EXPECTING ADDITIONAL RAINFALL WED INTO CHRISTMAS MORNING OF 1-2" WHICH IS LINE WITH GFS/ECMWF/NAM QPF...BUT CANT RULE OUT ISOLD AMOUNTS OF 3 INCHES GIVEN ANOMALOUS PWAT AIRMASS AND POTENTIAL FOR SOME ELEVATED CONVECTION. THIS WILL CAUSE TYPICAL URBAN AND POOR DRAINAGE FLOOD PROBLEMS BUT RIVER FLOODING IS NOT ANTICIPATED. THERE WILL LIKELY BE MULTIPLE PULSES OF HEAVY RAIN WED AFTERNOON INTO WED NIGHT AS SW LOW LEVEL JET MOVES INTO THE REGION. ELEVATED INSTABILITY INDICES ARE MARGINAL BUT CANT RULE OUT AN ISOLD TSTM WED AFTERNOON AND NIGHT...PARTICULARLY AS THE LOW LEVEL JET STRENGTHENS ACROSS THE REGION. WIND THREAT...LOW LEVEL JET AT 925 MB PEAKS AROUND 70 KT LATE WED NIGHT ACROSS THE COASTAL PLAIN. HOWEVER...SOUNDINGS INDICATE A RATHER STRONG INVERSION WHICH WILL LIKELY LIMIT STRONGER WINDS FROM MIXING TO SURFACE. GIVEN WARM TEMPS ALOFT...PROBABLY NEED SFC TEMPS TO REACH MID 60S TO MIX SOME OF THIS WIND DOWN TO THE SURFACE. WHILE WE DO EXPECT TEMPS TO REACH 60+ IN THE COASTAL PLAIN WED NIGHT...THERE IS JUST A LOW PROB OF MID 60S SO THINK MOST OF THE GUSTS WILL FALL SHORT OF WIND ADVISORY CRITERIA. IF A FINE LINE OF CONVECTION CAN DEVELOP AHEAD OF THE FRONT... THIS COULD HELP TO BRING DOWN STRONGER GUSTS WITH THE TIMING OF THIS BEING 06-12Z. MAX TEMPS WED WILL BE MOSTLY IN THE 40S INTERIOR AND 50S COASTAL PLAIN...RISING THROUGH THE 50S WED NIGHT AND LIKELY LOWER 60S ACROSS PORTIONS OF RI AND SE MA. DEWPOINTS MAT APPROACH 60 WED NIGHT IN THE COASTAL PLAIN. CHRISTMAS... HEAVY RAIN WILL LIKELY BE ONGOING CHRISTMAS MORNING IN THE COASTAL PLAIN...THEN RAIN MOVES OUT BY MIDDAY WITH SKIES BECOMING PTSUNNY IN THE AFTERNOON. GUSTY SW WINDS IN THE MORNING NEAR THE COAST ASSOCD WITH THE LLJ...THEN 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 TEMPS IN THE 50S TO NEAR 60 DEGREES WILL OCCUR IN THE MORNING...WITH TEMPS FALLING IN THE AFTERNOON. FRIDAY INTO SAT... HIGH PRES BRINGS DRY WEATHER WITH ABOVE NORMAL TEMPS. THE MILDER DAY WILL BE SATURDAY WITH TEMPS REACHING INTO THE 50S AS THE HIGH SLIDES TO SE WITH SW FLOW DEVELOPING. SUNDAY INTO MONDAY... LOW CONFIDENCE FORECAST. A COLD FRONT MAY BRING A FEW RAIN/SNOW SHOWERS SUNDAY...THEN WILL HAVE TO WATCH FOR POSSIBLE FRONTAL WAVE SUN NIGHT INTO MON. THIS WAVE MAY END UP TOO FAR SOUTH BUT WILL KEEP LOW POPS IN THE FORECAST. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TONIGHT/...MODERATE CONFIDENCE. MVFR/IFR CIGS BECOME MORE WIDESPREAD THROUGH DAYBREAK AS PATCHES OF RAIN LIFT NE ACROSS REGION. MOST OF RAIN WILL FALL FROM EARLY THIS MORNING INTO AFTERNOON BEFORE TAPERING OFF TO SPOTTY DRIZZLE LATER IN DAY. INCREASING E WINDS NEAR COAST WHERE 25KT GUSTS EXPECTED. WINDS DIMINISH THIS EVENING BUT WIDESPREAD IFR/LIFR EXPECTED IN FOG AND SPOTTY DRIZZLE. KBOS TERMINAL...MODERATE CONFIDENCE. ONSET OF LOWER CEILINGS THIS MORNING MAY BE 2-3 HOURS TOO FAST...BUT FAIRLY CONFIDENT IN IFR BY 12Z. KBDL TERMINAL...MODERATE CONFIDENCE. OUTLOOK...WEDNESDAY THROUGH SATURDAY... WEDNESDAY AND WED NIGHT...HIGH CONFIDENCE. IFR CONDITIONS IN WIDESPREAD RAIN. LLWS IS LIKELY PARTICULARLY WEDNESDAY AFTERNOON AND NIGHT AS S/SW LOW LEVEL JET STRENGTHENS ACROSS THE REGION. CHRISTMAS...MODERATE CONFIDENCE. IFR IN RAIN TO START...THEN CONDITIONS IMPROVE TO VFR IN THE AFTERNOON. WEST WIND GUSTS TO 35-40 KT POSSIBLE IN THE AFTERNOON. FRIDAY AND SATURDAY...HIGH CONFIDENCE. VFR. && .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. SCA REMAINS POSTED FOR INCREASING E WINDS AND BUILDING SEAS THROUGH THIS EVENING...AS LOW PRESSURE HEADS UP THE COAST FROM MID ATLANTIC AND BRINGS PERIODS OF RAIN AND PATCHY FOG. WINDS DIMINISH QUICKLY THIS EVENING AS LOW PRESSURE REACHES S COAST OF NEW ENGLAND...BUT FOG SHOULD BECOME MORE WIDESPREAD WITH VSBYS 1-3 NM AND SPOTTY DRIZZLE. SEAS WILL REMAIN AOA 5 FT ON OUTER WATERS. OUTLOOK...WEDNESDAY THROUGH SATURDAY...MODERATE CONFIDENCE WED AND WED NIGHT...SOUTHERLY LOW LEVEL JET MOVES INTO THE WATERS LATE WED AND WED NIGHT BUT STRONG LOW LEVEL INVERSION WILL LIKELY PREVENT THESE WINDS FROM MIXING DOWN TO THE SURFACE. EXPECT GUSTS TO 25-30 KT WED NIGHT. VSBYS REDUCED IN RAIN AND FOG. 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 SCA FRI...THEN INCREASING SW WINDS SAT WITH GUSTS TO 25 KT. && .TIDES/COASTAL FLOODING... EASTERN MASSACHUSETTS COAST: HIGH TIDE AT BOSTON WILL BE 11.6 FT AT MIDDAY TODAY AND 11.7 FT AT MIDDAY WED WITH A SURGE OF 1.0 TO 1.5 FT. SHOULD SEE SOME MINOR COASTAL FLOODING AT MORE VULNERABLE LOCATIONS ON BOTH HIGH TIDE CYCLES...BUT CERTAINLY NOTHING SIGNIFICANT AS WINDS AND SEAS ARE NOT FAVORABLE. COASTAL FLOOD ADVISORY REMAINS POSTED FOR TODAY AND WILL PROBABLY NEED TO BE ISSUED LATER FOR WED HIGH TIDE. SOUTH COAST: WE DO NOT EXPECT MUCH IF ANY COASTAL FLOODING ALONG THE SOUTH COAST. NOT ENOUGH WIND OR SURGE FOR THE WED EVENING HIGH TIDE. HIGHEST SURGE OF 1-2 FEET LIKELY TO OCCUR DURING LOW TIDE LATE WED NIGHT WITH THE SURGE AND SEAS DECREASING DURING THE CHRISTMAS MORNING HIGH TIDE. WORST CASE IS MINOR SPLASHOVER FOR THE CHRISTMAS MORNING HIGH TIDE BUT EVEN THIS IS NOT LOOKING FAVORABLE. && .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...NONE. MA...COASTAL FLOOD ADVISORY FROM 9 AM THIS MORNING TO 3 PM EST THIS AFTERNOON FOR MAZ007-015-016-019-022. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ231- 232. SMALL CRAFT ADVISORY UNTIL 10 AM EST THIS MORNING FOR ANZ233- 234. SMALL CRAFT ADVISORY UNTIL 6 AM EST WEDNESDAY FOR ANZ235-237- 250-251-254>256. && $$ SYNOPSIS...KJC/JWD NEAR TERM...JWD SHORT TERM...JWD LONG TERM...KJC AVIATION...KJC/JWD MARINE...KJC/JWD TIDES/COASTAL FLOODING...KJC CLIMATE...JWD

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