Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 192107 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 507 PM EDT SUN OCT 19 2014 .SYNOPSIS... GUSTY NORTHWEST WINDS WILL BRING COLDER AIR TO SOUTHERN NEW ENGLAND TONIGHT. HIGH PRESSURE MOVES OVER THE REGION ON MONDAY. A DISTURBANCE DROPPING THROUGH THE GREAT LAKES WILL GENERATE A LONG DURATION COASTAL STORM TUESDAY THROUGH FRIDAY WITH PERIODS OF HEAVY RAIN. CONDITIONS LOOK TO IMPROVE SLOWLY BY NEXT WEEKEND. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... REMAINDER OF THIS AFTERNOON... UPPER TROUGH OVERHEAD WILL MOVE OFF TO THE EAST BY THIS EVENING. TEMPERATURES AT 500 MB HAVE BEEN RUNNING AROUND -22C WHICH IS COLD ENOUGH TO DESTABILIZE THE AIRMASS...ESPECIALLY COMBINED WITH ANY SOLAR HEATING OF THE SURFACE. EXPECT PLENTY OF DIURNAL CLOUDS AND POSSIBLY A FEW LIGHT SHOWERS. OBSERVED WINDS ALOFT BELOW 850 MB ARE 25 KNOTS. MIXING WILL TAP THESE WINDS AND SUPPORT NORTHWEST GUSTS OF 25-30 MPH. TONIGHT... HIGH PRESSURE BUILDS OVER THE REGION WITH CLEARING SKIES AND DIMINISHING WIND. THE LIGHT WIND AND CLEAR SKIES WILL ALLOW FOR RADIATIONAL COOLING ESPECIALLY AWAY FROM THE COAST. OBSERVED AFTERNOON DEW POINTS ARE IN THE 30S WITH 20S UPSTREAM IN ONTARIO AND WESTERN NY. WITH THIS VALUES ADVECTING OVER NEW ENGLAND...EXPECT PLENTY OF ROOM FOR TEMPERATURES TO FALL BELOW FREEZING IN INTERIOR SOUTHERN NEW ENGLAND WHILE COASTAL AREAS FALL INTO THE 30S. EXPECTED VALUES ARE SIMILAR TO THE PREVIOUS TWO FORECASTS. WE WILL CONTINUE THE FREEZE WARNING FOR MUCH OF SOUTHERN NEW ENGLAND WITH FROST ADVISORY ALONG NARRAGANSETT BAY AND THE MASS EAST COAST. MODELS START TO BRING HIGH CLOUDS IN LATE AT NIGHT. WITH SUFFICIENT THICKNESS...THESE CLOUDS COULD SLOW THE COOLING AND KEEP SOME OF THE INTERIOR ABOVE FREEZING. BUT WE EXPECT THE INITIAL CLOUDS TO BE THIN ENOUGH TO HAVE LITTLE EFFECT. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... MONDAY... HIGH PRESSURE CRESTS OVER THE REGION. WINDS WILL SHIFT AROUND TO SOUTHWEST DURING THE AFTERNOON. EXPECT SOME INCREASE IN MID AND HIGH CLOUDS BUT OVERALL A FAIR WEATHER DAY. MIXING SHOULD REACH TO 925 MB...POSSIBLY A LITTLE HIGHER. TEMPS EQUIVALENT TO -1C/-3C AT 850 MB...SUPPORTS MAX TEMPS IN THE 50S. MONDAY NIGHT... RIDGE MOVES OFF TO THE EAST WHILE A TROUGH DIGS OVER THE GREAT LAKES. THIS TURNS OUR UPPER FLOW INTO A SOUTHWEST FLOW. WEAK HINTS IN THE MODEL DATA OF A 70-KNOT JET OVERHEAD OF THE NORTHEAST USA. THE RIGHT ENTRANCE REGION OF THIS POSSIBLE JET IS LOCATED SOUTH OF THE REGION SUGGESTING THE BEGINNING OF CYCLOGENESIS ALONG THE MID ATLANTIC COAST. MEANWHILE THE SOUTHWEST FLOW WILL BE TRANSPORTING MOISTURE UP THE COAST IN CLOUDS. EXPECT INCREASING AND THICKENING CLOUDS THROUGH THE NIGHT WITH POTENTIAL FOR INCREASING LIFT. THE MOISTURE AND LIFT WOULD LEAD TO A CHANCE OF RAIN LATE AT NIGHT. TEMPS WILL INITIALLY COOL IN THE EVENING WITH ENOUGH TIME TO DROP 10-15 DEGREES FROM DAYTIME HIGHS. WE USED A RANGE OF MIN TEMPS IN THE UPPER 30S AND 40S. && .LONG TERM /TUESDAY THROUGH SUNDAY/... HIGHLIGHTS... * A LONG DURATION COASTAL STORM WILL IMPACT NEW ENGLAND FROM TUE THROUGH AT LEAST THU. PERIODS OF HEAVY RAIN APPEAR TO BE THE PRIMARY THREAT. A BRIEF PERIOD OF GUSTY WINDS ARE ALSO POSSIBLE TUE NIGHT AND WED ALONG THE IMMEDIATE NE MASS COAST. * THE LOW LOOKS TO PUSH SLOWLY NE DURING THU...THOUGH INCLEMENT WEATHER MAY LINGER INTO FRI AS THE UPPER LOW SLOWLY MOVES AWAY. * EXPECT GENERALLY DRY WEATHER NEXT WEEKEND...THOUGH MAY SEE A FEW SHOWERS LATE SAT NIGHT/SUN AS COLD FRONT PASSES. OVERVIEW AND MODEL PREFERENCES... OVERALL 12Z OP MODELS AS WELL AS ENSEMBLE GUIDANCE CONTINUE TO SIGNAL DEVELOPMENT OF H5 CUTOFF LOW PRES ACROSS NORTHEAST AND MID ATLC STATES DURING MOST OF THIS TIMEFRAME. BY THE BEGINNING OF THIS TIMEFRAME...THE UPPER LOW ALREADY TAKING SHAPE OVER THE APPALACHIANS...PUSHING OFF THE NJ/DELMARVA COASTLINE BY MID WEEK. QUESTION WILL BE WHERE THE SURFACE FEATURE FORMS AND EVENTUALLY SETS UP SHOP. ANOTHER ISSUE WILL BE DEVELOPING STRONG E-NE LOW LEVEL JET AND HOW CLOSE THIS WILL COME TO THE E COAST...OR IF IT REMAINS N OF THE REGION LATE TUESDAY INTO WEDNESDAY. THE UPPER SYSTEM AND SURFACE LOW MEANDER THROUGH LATE THU...THEN LOOKS TO SLOWLY EXIT TO NOVA SCOTIA...THOUGH STILL SOME TIMING ISSUES NOTED ON OPERATIONAL MODELS. GENERAL SIGNAL ON DETERMINISTIC AND ENSEMBLE MODELS SIGNALING IMPROVED CONDITIONS BY NEXT WEEKEND. USED A BLEND OF AVAILABLE GUIDANCE INTO THURSDAY...THEN TRANSITIONED OVER TO ENSEMBLE GUIDANCE WHERE HIGHER TIMING UNCERTAINTY STILL IN PLAY. DAILIES... TUESDAY... VIGOROUS H5 SHORT WAVE TROUGH CONTINUES TO DIG AS IT SHIFTS SE OUT THE EASTERN LAKES EARLY TUE. QUICKLY DEEPENING TROUGH TAKES SHAPE LATE TUE/TUE NIGHT...WHILE SURFACE LOW STARTS TO FORM TUE NIGHT SOMEWHERE OFF THE DELMARVA/NJ COAST. AREA OF RAIN CONTINUES TO DEVELOP AND EXPAND FROM E-W ACROSS THE REGION. NOTING BAND OF HEAVIER RAINFALL OFFSHORE...BUT QUESTION WILL BE WHETHER SOME OF THIS WILL WORK INLAND. AT THIS POINT...SHOULD REMAIN OFFSHORE BUT SOMETHING TO MONITOR. MAY SEE SOME HEAVIER PRECIP MAKE IT INTO NE MA/S CENTRAL NH OVERNIGHT TUE NIGHT. QUESTION REMAINS ABOUT STRONGER E-NE WINDS THAT MAY TRY TO WORK ONSHORE WITH THE STRONG LOW LEVEL JET WORKING AROUND THE DEVELOP CUTOFF UPPER LOW. AT THIS POINT...STILL LOOKS LIKE THEY WILL HAVE A TOUGH TIME MIXING DOWN AS LAPSE RATES REMAIN LOW /AROUND 2-3C/KM/ BUT COULD SEE SOME GUSTY WINDS WORK DOWN WITH ANY HEAVIER RAINFALL TUE NIGHT MAINLY ACROSS NE COASTAL MA. HIGHS ON TUE WILL MAKE IT TO BETWEEN 60 AND 65 ALONG THE COAST...BUT ONLY THE MID-UPPER 50S ACROSS THE HIGHER TERRAIN. TUESDAY NIGHT THROUGH THURSDAY NIGHT... EXACT TIMING AND STORM IMPACTS REMAIN UNCERTAIN...THOUGH DOES LOOK LIKE THE MAIN THREAT WILL BE PERIODS OF HEAVY RAINFALL. USING A BLEND OF AVAILABLE MODEL GUIDANCE...QPF TOTALS FOR THIS TIMEFRAME LOOK TO BE A BIT LESS THAN PREVIOUS FORECAST...GENERALLY AROUND 1.25 INCHES ON THE S COAST RANGING UP TO 1.75 TO AROUND 2 INCHES ACROSS NE MA INTO S NH. QPF COULD INCREASE IF HEAVIER RAIN BANDS MOVE ACROSS...THOUGH. EXPECT STEADY RAIN FROM TUE NIGHT INTO THU NIGHT...THEN SHOULD BEGIN TO TRANSITION TO SHOWERS ACROSS THE CT VALLEY AFTER MIDNIGHT THU NIGHT AS THE SURFACE LOW LOOKS TO SLOWLY HEAD NE WHILE THE UPPER LEVEL SYSTEM LINGERS ACROSS THE REGION. MODELS CONTINUE TO SIGNAL THE STRONG WIND THREAT TO REMAIN N OF THE REGION...BUT CAN NOT TOTALLY RULE OUT SOME GUSTS UP TO 25 KT OR SO ACROSS NE MA INTO S CENTRAL NH DEPENDING UPON POSITION OF JET AXIS DURING TUE NIGHT INTO WED. SOMETHING TO MONITOR. WITH STRONGEST E-NE WINDS PUSHING N OF THE REGION...THREAT FOR COASTAL FLOODING REMAINS LOW. SEAS DO BUILD OFF THE E MA COAST AND COULD SEND SOME HIGHER SWELLS TOWARD THE SHORE BY WED/THU...AND WILL CONTINUE TO MONITOR THE LOW LEVEL HIGH WIND AXIS TO SEE IF IT SHIFTS FURTHER S. WITH INCREASING SWELLS...RISK CONTINUES FOR COASTAL BEACH EROSION WITH THE WAVE ACTION OVER SEVERAL HIGH TIDE CYCLES. FRIDAY... QUESTION AT THIS POINT IS HOW QUICKLY WILL THE SURFACE LOW DEPART DURING FRIDAY. MODELS HAVE DIFFERENT TIMING ON THIS...BUT GENERALLY LOOKS TO PUSH TOWARD NOVA SCOTIA BY LATE FRIDAY. HOWEVER...COULD STILL SEE SOME LINGERING SHOWERS ON BACK SIDE INTO FRI NIGHT ACROSS E MA/S CENTRAL NH AS UPPER LEVEL SYSTEM SLOWLY PUSHES E. AT THIS POINT...SHOULD SEE IMPROVING CONDITIONS OVERNIGHT FRI. NEXT WEEKEND... LOOKS TO BE A DRY SEASONABLE WEEKEND AS NW WINDS AT THE SURFACE AND ALOFT TAKE OVER. SOME QUESTION AS TO APPROACH OF FAST MOVING H5 SHORT WAVE AS ASSOCIATED SURFACE COLD FRONT QUICKLY CROSSING THE REGION SAT NIGHT/EARLY SUN. NOT MUCH MOISTURE AT SURFACE...FOR NOW...BUT COULD SEE A FEW SHOWERS ACROSS S NH/N MA AS THE FRONT PASSES. && .AVIATION /21Z SUNDAY THROUGH FRIDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH MONDAY/...HIGH CONFIDENCE. THROUGH 00Z/8 PM... VFR WITH CLOUD BASES AROUND 4500 FEET. NORTHWEST WINDS GUSTING 25-30 KNOTS...DIMINISHING IN THE EVENING. TONIGHT AND MONDAY...VFR. CLEARING SKIES WITH LIGHT WINDS. MONDAY NIGHT...VFR MOST OF THE NIGHT. PATCHES OF MVFR CIGS IN LIGHT RAIN POSSIBLE LATE AT NIGHT. KBOS...HIGH CONFIDENCE IN TAF. KBDL...HIGH CONFIDENCE IN TAF. OUTLOOK...TUESDAY THROUGH FRIDAY... TUESDAY THROUGH THURSDAY...HIGH CONFIDENCE OVERALL AS CONDITIONS LOWERING TO MVFR-IFR IN DEVELOPING RAIN DURING TUE...BUT LOW CONFIDENCE ON EXACT TIMING OF DETAILS. LOW PROB OF E-NE WIND GUSTS REACHING 20-25 KT ACROSS NE MA COAST TUE NIGHT/WED. CONDITIONS SHOULD START TO IMPROVE OVER WESTERN AREAS THU NIGHT. FRIDAY...MODERATE CONFIDENCE. EXPECT CONDITIONS TO IMPROVE TO VFR ACROSS WESTERN AND CENTRAL AREAS BY MIDDAY. ACROSS E MA/S CENTRAL NH...MVFR CONDITIONS IN LOW CLOUDS AND SCATTERED LINGERING SHOWERS MAY CONTINUE INTO FRI NIGHT BEFORE IMPROVING. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TODAY THROUGH MONDAY/...HIGH CONFIDENCE. THROUGH 8 PM/00Z... WIND GUSTS 25 TO 30 KNOTS CONTINUE. SEAS LINGER AT 5-6 FEET ON THE OUTER WATERS. PLENTY OF CLOUDS MOVING OFF LAND WITH SPRINKLES POSSIBLE. SMALL CRAFT ADVISORY LINGERS THROUGH THIS EVENING. TONIGHT...HIGH PRESSURE APPROACHES FROM THE WEST. EXPECT NORTHWEST WINDS TO DIMINISH OVERNIGHT WITH GUSTS 15 TO 20 KNOTS AFTER MIDNIGHT. LINGERING 5 FOOT SEAS ON THE OUTER WATERS...BUT WITH A DIMINISHING TREND OVERNIGHT. SMALL CRAFT ADVISORY LINGERS THROUGH EARLY TONIGHT...THEN DIMINISHES TO JUST THE OUTER WATERS LATE AT NIGHT. MONDAY... HIGH PRESSURE BUILDS OVER THE WATERS. DIMINISHING NORTHWEST WINDS BECOME SOUTHWEST IN THE AFTERNOON. SEAS DIMINISH BELOW 5 FEET DURING THE MORNING. MONDAY NIGHT... HIGH PRESSURE MOVES OFFSHORE. WINDS TURN SOUTHWEST BUT REMAIN BELOW SMALL CRAFT THRESHOLDS. SEAS BUILD A LITTLE BUT REMAIN BELOW 5 FEET. LIGHT RAIN MOVES UP FROM THE MID ATLANTIC COAST LATE AT NIGHT. OUTLOOK...TUESDAY THROUGH FRIDAY... TUESDAY...HIGH CONFIDENCE. EXPECT SOUTHERLY WINDS TO GRADUALLY BACK AROUND TO E-SE BY TUESDAY EVENING. WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT CRITERIA. TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...MODERATE CONFIDENCE. EXPECT E-NE WIND GUSTS TO AROUND 25 KT MAINLY ACROSS THE EASTERN OUTER WATERS N OF BOSTON TO CAPE ANN. LOW PROB OF GUSTS TO 30 KT OR EVEN TO GALE FORCE LATE THU NIGHT AND WED. SEAS WILL BUILD ON THE EASTERN OPEN WATERS TO 5-8 FT BY EARLY WED...WITH THE HIGHEST SEAS ON THE FAR OUTER WATERS...THEN UP TO 5 FT ON THE SOUTHERN OUTER WATERS WED. WINDS SHOULD BEGIN TO DIMINISH WED NIGHT THOUGH SEAS WILL REMAIN AOA 5 FT. PERIODS OF HEAVY RAIN AND PATCHY FOG WILL REDUCE VSBY. THURSDAY AND FRIDAY...MODERATE CONFIDENCE. WINDS SHIFT TO N-NW ON THU BUT REMAIN BELOW SMALL CRAFT CRITERIA. MAY SEE WIND GUSTS UP TO 20 KT DURING FRI. SEAS REMAIN HIGH ESPECIALLY ON THE EASTERN OPEN WATERS...BUT SHOULD SUBSIDE THU NIGHT AND FRI. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT MONDAY FOR CTZ002>004. MA...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM EDT MONDAY FOR MAZ007-015-016-019-022-023. FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT MONDAY FOR MAZ005-006-009>014-017-018-020-021. NH...NONE. RI...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM EDT MONDAY FOR RIZ002-004-005-007. FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT MONDAY FOR RIZ001-003-006. MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT MONDAY FOR ANZ231>234-251. SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ230- 235>237. SMALL CRAFT ADVISORY UNTIL 11 AM EDT MONDAY FOR ANZ250-254. SMALL CRAFT ADVISORY UNTIL 8 AM EDT MONDAY FOR ANZ255. SMALL CRAFT ADVISORY UNTIL 4 AM EDT MONDAY FOR ANZ256. && $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/EVT MARINE...WTB/EVT

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