Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 250706 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 206 AM EST TUE NOV 25 2014 .SYNOPSIS... A WEAK COLD FRONT WILL MOVE ACROSS THE REGION OVERNIGHT. THIS WILL ALLOW FOR A QUIET AND MILD TUESDAY WITH SOME GUSTY SW WINDS. NOR`EASTER FOR WEDNESDAY INTO THURSDAY. GRADUALLY TURNING COLDER INTO THE WEEKEND. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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245 AM UPDATE... TEMPS HAVE ACTUALLY SPIKED TO THE MID AND UPPER 60S OVER THE LAST FEW HOURS ACROSS THE CT VALLEY INTO CENTRAL MA ON STEADY SW WINDS. ALONG THE S COAST...PATCHY DENSE FOG HAS MOVED ASHORE ALONG WITH GUSTY WINDS ACROSS CAPE COD AND THE ISLANDS. NOTED A GUST UP TO 30 KT AT 04Z AT KFMH. RATHER SHARP DEWPT DROP BEHIND THE FRONT INTO CENTRAL NY EVEN WITH WINDS REMAINING FROM THE SW. MID AND HIGH CLOUDS HAVE PUSHED ACROSS THE REGION ON THE SW WIND FLOW AT THE SURFACE AND ALOFT. QUESTION AT THIS POINT WILL BE WHEN THE COLD FRONT WILL PUSH ACROSS THE REGION CONSIDERING THE LONG WAVE TROUGH TO THE W AND PERSISTENT SW FLOW AT THE SURFACE AND ALOFT INTO THE MID MORNING HOURS. WILL CONTINUE TO MONITOR FOR DEWPT DROPS MOVING E OVER THE NEXT FEW HOURS. HAVE UPDATED TEMPS/DEWPTS TO KEEP THEM MILDER THAN PREVIOUS FORECAST. REMAINDER OF FORECAST LOOKS OK.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY/...
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TUESDAY INTO TUESDAY NIGHT... HIGH PRESSURE WILL BEGIN TO SLIDE IN ON TUESDAY ALLOWING FOR A QUIET WEATHER DAY. STILL A DESCENT JET ALOFT SO WILL CONTINUE TO SEE GUSTY WINDS AROUND 15-25 MPH DURING THE DAY. CAA WILL BEGIN TO POOL IN SO TEMPS WILL BE COOLER THAN TODAY WITH HIGHS IN THE MID 50S TO LOW 60S...STILL SLIGHTLY ABOVE AVERAGE. QUIET OVERNIGHT. WEDNESDAY THROUGH THURSDAY MORNING... */ HIGHLIGHTS... - NOR`EASTER WILL IMPACT NEW ENGLAND WEDNESDAY INTO WEDNESDAY NIGHT - SIGNIFICANT IMPACTS WHICH WILL DISRUPT TRAVEL - PLOWABLE SNOWS ACROSS THE INTERIOR - POTENTIAL HEAVY RAIN ACROSS SE NEW ENGLAND /CAPE COD - ISLANDS/ - STRONG NE WINDS ACROSS E MA / CAPE COD / ISLANDS */ OVERVIEW AND MODEL CONSENSUS... OVERVIEW... INDIVIDUAL MODEL SOLUTIONS NARROWING IN ON A FOCUS OF A STORM TRACK AROUND THE 40N/70W BENCHMARK. BUT IT CONTINUES TO BE DIFFICULT TO RESOLVE SPECIFIC DETAILS ACROSS THE REGION. AGAIN...WE REALLY MAY NOT KNOW THE TRUE OUTCOMES TILL JUST A DAY OR TWO PRIOR. WEIGHED PREFERENCE UPON THE 24.15Z SREF / 24.12Z GFS ... AND NOW THE 24.12Z ECMWF HAS FINALLY COME ABOARD...HOORAY! NOW WITH A CONSISTENT STORM-TRACK...IMPACTS BEGIN WEDNESDAY MORNING...INCREASING INTO THE EVENING WITH THE HEIGHT OF THE STORM. MODEL CONSENSUS HAS THE STORM WINDING DOWN THURSDAY MORNING. SYNOPTICALLY... BASED ON A PREFERRED MODEL CONSENSUS ABOVE: LOW PRESSURE INTENSIFIES FROM THE GULF TUESDAY NE ACROSS THE 40N/70W BENCHMARK S OF NANTUCKET AROUND MIDNIGHT THURSDAY. ACCOMPANYING H85 LOW PASSES NE IN THE VICINITY OF THE CAPE COD CANAL TO NW OF THE 40N/70W BENCHMARK. DURING WEDNESDAY...BAROCLINIC LEAF / OVER-RUNNING PATTERN OF BROAD- SCALE ASCENT YIELDS TOP-DOWN MOISTENING DYNAMICALLY COOLING WITH TIME. WITH SURFACE INTERIOR N-FLOW WITH COASTAL NE-FLOW...AND DRIER AIR N/W...AM EXPECTING WETBULBING TOWARDS THE DEWPOINT TO AROUND THE FREEZING MARK THE DIVISION OF WHICH MAY BE ALONG A POSSIBLE COASTAL FRONT SETUP IMMEDIATELY N/W OF THE I-95 CORRIDOR. EXPECT INITIAL RAINS FOR INTERIOR LOCALES CHANGING OVER TO SNOW THROUGH THE DAY... AS TO THE TIMING OF THAT TRANSITION REMAINS UNCERTAIN AT THIS TIME. INTO WEDNESDAY NIGHT...INTENSIFYING LOW SWEEPS NE AROUND THE 40N/70W BENCHMARK S OF NANTUCKET. WITH A PROGRESSIVE FLOW-PATTERN /+NAO/ AND ABSENCE OF A CLOSED-LOW ABOVE H85 /MORE EMPHASIS OF AN ANTI-CYCLONIC BRANCH OF THE WARM CONVEYER BELT/...WITH LOW PRESSURE TROUGHING OVER THE GREAT LAKES ASSOCIATED WITH A STRONG POLAR-LOW HOLDS ARCTIC AIR REARWARD ACROSS C-CANADA /+AO/...EXPECTING THERMAL PROFILES AROUND THE FREEZING MARK OVER INTERIOR S NEW ENGLAND...WHILE MILD OVER THE IMMEDIATE COAST WITH CONTINUED THINKING OF MAINTAINED COASTAL-FRONT SETUP PRIOR TO STORM PASSAGE. PRECIPITATION OUTCOMES... A FRONT-END THUMP IS ANTICIPATED WITH SLANTWISE FORCING PER FRONTO- GENESIS NW OF H85 LOW EXTENDED E...ALONG WITH INDICATIONS OF WEAK TROWALING TOWARD THE NW-QUADRANT OF THE H85 LOW. BENEATH ENHANCED ASCENT PER MID-LEVEL IMPULSE AND RRQ OF THE UPPER-LEVEL-JET...STRONG DEEP-LAYER LIFT THROUGH MOIST DENDRITIC ZONES SHOULD YIELD A NW-SE PRECIPITATION GRADIENT ACROSS S NEW ENGLAND WITH HEAVIEST PRECIP IMMEDIATELY NW OF THE SURFACE LOW WHICH AGAIN SWEEPS NE AROUND THE 40N/70W BENCHMARK. COULD BE TALKING STORM-TOTAL PRECIPITATION AMOUNTS AROUND 1.5-2.0 INCHES FOR SE NEW ENGLAND WITH LESSENING AMOUNTS N/W WITH UP TO AROUND 0.75-INCHES FOR NW MA AND SW NH. SEE DETAILS BELOW IN THE THERMAL SETUP DISCUSSION THAT BREAKDOWN WHAT THOSE AMOUNTS COULD EQUATE TO IN TERMS OF SNOW. AGAIN...INITIAL PRECIP WILL LIKELY START OUT AS RAIN FOR SOME INTERIOR LOCATIONS BEFORE CHANGING TO SNOW. F-GEN SW-NE BANDING IS EVIDENT NW OF THE H85 LOW YET WITH MINOR INDICATIONS OF STATIC/INERTIAL INSTABILITY PER -EPV. CAN NOT RULE OUT THE POSSIBILITY OF SW-NE BANDS OF HEAVIER RETURNS PER WSR-88D RADAR DURING THE EVENT THAT WILL YIELD LOCALLY HIGHER PRECIPITATION AMOUNTS. ITS LIKELY WE WILL HAVE BETTER HANDLE IN ANALYZING SUCH OUTCOMES WHEN NEAR-TERM HIGH RESOLUTION GUIDANCE BECOMES AVAILABLE. THERMAL SETUP / SNOWFALL AMOUNTS... IF A COASTAL FRONT SETUP EMERGES BENEATH NEAR-ISOTHERMAL PROFILES AROUND -5C UP TO H7 THEN WOULD EXPECT SNOW-TO-LIQUID RATIOS RANGING FROM 10:1 TO 15:1 AS SREF METEOGRAMS SUGGEST ACROSS THE INTERIOR... WITH COASTAL RAINS. QUITE A RANGE THAT HAS SIGNIFICANT IMPLICATIONS ON SNOWFALL AMOUNTS. CHALLENGES OF SNOWFALL RATES DURING THE TIME OF DAY /LIKELY WILL SEE DIFFICULTY IN ACCUMULATING SNOWS DURING THE DAY WITH MARGINALLY COLD SURFACE TEMPERATURES/...ALSO WET-BULBING TO EQUILIBRIUM WITHIN THE FIRST 1 KFT ABOVE THE SURFACE...AND WHERE WE WILL EFFECTIVELY WET- BULB AND/OR WHERE AREAS ARE OVERCOME BY HEAVY SNOWFALL RATES. SO IN ADDITION TO THE INITIAL START/CHANGEOVER TO SNOW...SPEED OF THE SYSTEM AND IMPACTS TO PRECIPITATION AMOUNTS...AND RANGE OF SNOW- TO-LIQUID RATIOS...IT IS AN INCREDIBLY HUGE CHALLENGE TO NAIL DOWN SNOWFALL AMOUNTS. ONE KEY TO THIS ENTIRE FORECAST IS THE TRACK OF THE H85 LOW ALONG WITH H925 TEMPERATURES AT OR BELOW -2C. THE DIVIDING FREEZING LINE IS VARIED AMONG PREFERRED MODEL SOLUTIONS BUT NARROWING DOWN IN VICINITY OF THE AREA BETWEEN THE CT I-395 TO THE I-90/I-290/I-495 MA CORRIDOR TO THE I-95 CORRIDOR. SO AFTER PULLING OUT ALL MY HAIR...INTANGIBLES NOTED ABOVE MAKE THE SNOWFALL FORECAST TEDIOUS. FEEL DURING THE DAY SNOW ACCUMULATIONS WILL OCCUR AT 32-DEGREES OR BELOW WITH SNOW OCCURRING AT 36-DEGREES OR LOWER. THIS LOWERED SNOWFALL AMOUNTS FROM THE PRIOR SHIFT. IN COLLABORATION WITH WPC...BROAD AREA OF 6+ INCHES WITHIN THE WATCH AREA W OF NW MA TO NW RI ENCOMPASSING ALL OF CT EXCEPT COASTAL COMMUNITIES. AMOUNTS AROUND 8-10 INCHES POSSIBLE ACROSS THE HIGHER ELEVATIONS WITH LOCALLY HIGHER AMOUNTS. CONTINUED THINKING THAT THERE WILL LIKELY BE WIGGLE ROOM OF THE RAIN- SNOW BAND DUE TO UNCERTAINTY IN THERMAL PROFILES IN THE FORECAST. EXPECT CHANGES WITHIN SNOWFALL AMOUNTS ALONG THE GRADIENT ADVERTISED AROUND THE AREA IMMEDIATELY W OF THE I-95 CORRIDOR. WINDS... CONSISTENT NE-FLOW OVER E MA INCLUDING CAPE COD AND THE ISLANDS. GUSTS EXCEEDING 45 MPH ARE POSSIBLE BUT DEPENDENT ON HOW STRONG THE STORM ACTUALLY GETS...WHICH AGAIN IS UNCERTAIN. WIND ADVISORY HEAD- LINES MAY BE NEEDED...BUT IF THEY ARE WOULD EXPECT THAT IT WOULD BE ON THE LOW-END OF CRITERIA WITH GUSTS AROUND 50 MPH. COASTAL FLOODING... FORECAST TIDES OF 10 FEET EXPECTED AT BOSTON SHORTLY AFTER MIDNIGHT THURSDAY. ANTICIPATING A SHORT-RESIDENCY TIME OF THE STORM...PERHAPS A MINOR SURGE AND MAYBE SOME SPLASHOVER IF THE NE-WINDS DISCUSSED ABOVE VERIFY.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/... THURSDAY NIGHT THROUGH MONDAY... MEDIUM RANGE MODELS IN GOOD AGREEMENT THAT SERIES OF WEAK SHORTWAVES WILL ROTATE AROUND BROAD TROUGH IN PLACE OVER EASTERN STATES. THIS WILL MAINTAIN DRY WEATHER AND BELOW AVERAGE TEMPERATURES INTO WEEKEND...ALTHOUGH EXPECT SOME CLOUDINESS FROM TIME TO TIME. WE SHOULD SEE BRIEF MODERATION IN TEMPERATURES SUN AS SW FLOW DEVELOPS AHEAD OF NEXT COLD FRONT...WHICH WILL BRING REINFORCING SHOT OF COLD NEXT MON. MAY SEE FEW SHOWERS WITH PASSAGE OF FRONT SUN NIGHT/MON MORNING...BUT SHOULD BE ISOLATED AT BEST. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/...
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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 TONIGHT/...MODERATE CONFIDENCE. THROUGH 12Z...MAINLY VFR CIGS. S COAST OF RI/MA...IFR-LIFR CIGS/VSBYS IN FOG AND PATCHY -RA...WHICH MAY MOVE AS FAR N AS KPVD-KTAN-KPYM FOR A FEW HOURS PRIOR TO SUNRISE. SW WIND GUSTS UP TO 25-30 KT ACROSS CAPE COD AND THE ISLANDS SHOULD DIMINISH BY 10Z. TODAY...IFR TO LOCALLY LIFR CIGS/VSBYS SHOULD IMPROVE BY AROUND 15Z. OTHERWISE...EXPECT VFR CIGS AOA 10KFT. MAY SEE PATCHY CLOUDS AROUND 5-6KFT DURING THE AFTERNOON ACROSS RI/SE MA. SW WIND GUSTS UP TO 20-25 KT THROUGH MIDDAY ALONG S COAST. TONIGHT...EXPECT VFR CONDITIONS THROUGH THE NIGHT. LOW PROB OF MVFR-IFR CIGS AFTER 09Z ALONG S COAST. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. OUTLOOK...WEDNESDAY THROUGH FRIDAY... WEDNESDAY INTO THURSDAY...MODERATE CONFIDENCE. NOR`EASTER ANTICIPATED. SIGNIFICANT ACCUMULATION SNOWS OVER INTERIOR TERMINALS IMMEDIATELY W OF THE I-95 CORRIDOR. +SN POSSIBLE. AROUND 40 KT NE-WINDS ACROSS E MA / CAPE COD / ISLANDS...ALONG WITH +RA. MIX OF IFR-VLIFR CONDITIONS. FRI...VFR. MODERATE CONFIDENCE.
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&& .MARINE...
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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 TOMORROW/...MODERATE CONFIDENCE. HAVE ENDED THE SMALL CRAFT FOR BOSTON HARBOR/NARRAGANSETT BAY AT 10 PM AS WINDS/SEAS HAVE DIMINISHED. WINDS HAVE ALSO DROPPED BELOW GALE ON THE EASTERN OUTER WATERS...BUT EXPECT WINDS TO INCREASE TO GALE FORCE AGAIN WED. HAVE ISSUED GALE WATCH FOR THOSE WATERS. PREVIOUS DISCUSSION... SOUTHERLY FLOW WILL CONTINUE OVERNIGHT WITH GUSTS AROUND 25 TO 30 KTS. WEAK COLD FRONT WILL SWEEP THE WATERS TOWARDS TUESDAY MORNING SWITCHING THE WINDS TO SW. SEAS REMAINING CHOPPY. SOUTHWEST WINDS WILL CONTINUE TOMORROW AS HIGH PRESSURE BUILDS. YET WITH WEAK CAA ALOFT EXPECT GUSTS TO REMAIN UP TO 20-25 KTS. SEAS WILL BE SLOW TO RESPONSE. SO SCA WILL LIKELY BE NEEDED. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... WEDNESDAY INTO THURSDAY...MODERATE CONFIDENCE. NOR`EASTER ANTICIPATED PASSING NE AROUND THE 40N/70W BENCHMARK S OF NANTUCKET MIDNIGHT THURSDAY. LIKELY NE GALES OVER E MA / CAPE COD / ISLANDS...AND ALL WATERS. HEAVY RAIN LENDING TO REDUCED VISIBILITIES AT TIMES. FRI...MODERATE CONFIDENCE. SCA CONDITIONS SHOULD PERSIST ON OUTER WATERS DUE TO 25KT GUSTS AND 5 FT SEAS.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY MORNING FOR CTZ002>004. MA...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY MORNING FOR MAZ002>006-008>012-026. NH...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY MORNING FOR NHZ011-012-015. RI...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY MORNING FOR RIZ001. MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST EARLY THIS MORNING FOR ANZ232>234-251. SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ235- 237-255-256. GALE WATCH FROM LATE TONIGHT THROUGH LATE WEDNESDAY NIGHT FOR ANZ250-254.
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&& $$ SYNOPSIS...DUNTEN/SIPPRELL NEAR TERM...EVT SHORT TERM...DUNTEN/SIPPRELL LONG TERM...JWD AVIATION...SIPPRELL/EVT/JWD MARINE...SIPPRELL/EVT/JWD

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