Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 230611 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 111 AM EST SUN NOV 23 2014 .SYNOPSIS... A SIGNIFICANT WARM UP IS ON TAP SUNDAY AND ESPECIALLY MONDAY...BUT WITH A PERIOD OF RAIN SUNDAY NIGHT INTO MONDAY MORNING. QUIET AND MILD TUESDAY. A COASTAL STORM ANTICIPATED WEDNESDAY INTO THURSDAY MORNING. GRADUALLY TURNING COLDER INTO THE WEEKEND. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... 1 AM UPDATE... SCT TO NUMEROUS SHOWERS MOVING E INTO W MA WITH ADDITIONAL SHOWERS ACROSS E NY. ACTIVITY ASSOCD WITH 50 KT LOW LEVEL JET AND DEEPENING MOISTURE PLUME. DEWPOINTS HAVE COME UP CONSIDERABLY IN W MA ALLOWING GREATER COVERAGE OF SHOWERS. MAIN FOCUS FOR PRECIP WILL REMAIN ALONG AND N OF THE PIKE WHERE MOISTURE IN THE LOW LEVELS IS GREATER. MOISTURE IN THE LOW LEVELS DECREASES FURTHER S FROM THE PIKE AND MOSTLY DRY CONDITIONS EXPECTED THROUGH CT/RI AND SE MA. TEMPS IN W MA STILL ABOVE FREEZING IN THE MID 30S...AND LOWER 40S CT VALLEY AS WESTERLY LOW LEVEL JET INDUCING S FLOW. NOTED A FEW LOCATIONS IN W MA 32-33 DEGREES PER MESONET SO CANT RULE OUT AN ISOLATED POCKET OF SOME LIGHT FREEZING RAIN INTERIOR HIGH TERRAIN...MAINLY BERKSHIRES...BUT THE THREAT IS LOW. GUSTY SW WINDS TO 30-40 MPH ACROSS CAPE/ISLANDS WILL DIMINISH THROUGH DAYBREAK. TEMPS REMAINING NEARLY STEADY OVERNIGHT. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/... ***BRIEF PERIOD OF HEAVY RAIN VERY LATE SUN NIGHT/MON MORNING IMPACTING THE AM RUSH HOUR*** SUNDAY... THE SHORTWAVE SHOULD EXIT THE REGION AND RESULT IN MID LEVEL DRYING. THIS WILL RESULT IN AT LEAST PARTLY SUNNY SKIES AND MUCH MILDER TEMPS. 850 MB TEMPS AROUND +5C SHOULD ALLOW HIGH TEMPS TO RECOVER INTO THE LOWER TO MIDDLE 50S AND LEANED TOWARD THE WARMER GUIDANCE. GIVEN MID LEVEL TEMPS ARE PRETTY MILD...WOULD NOT BE SHOCKED IF THE NEXT SHIFT NEEDS TO INCREASE HIGHS A FEW MORE DEGREES. GUIDANCE SEEMS A BIT COOL CONSIDERING THOSE FACTORS. SUNDAY NIGHT AND MONDAY... DRY WEATHER EXPECTED THROUGH SUNDAY EVENING. STRONG LOW PRESSURE WILL THEN BE PASSING WELL TO OUR WEST ACROSS THE GREAT LAKES VERY LATE SUN NIGHT INTO MON MORNING. THE WILL CAUSE A STRONG LOW LEVEL JET TO DEVELOP ALONG WITH PLENTY OF MOISTURE. GEFS IS SHOWING THAT PWATS INCREASE TO AT LEAST 3 STANDARD DEVIATIONS ABOVE NORMAL. EXPECT RAIN TO DEVELOP AFTER MIDNIGHT AND CONTINUE INTO MONDAY MORNING. WITH STRONG FORCING AND HIGH PWATS IN PLACE...BRIEF HEAVY RAIN IS EXPECTED BUT FORTUNATELY SYSTEM IS FAIRLY PROGRESSIVE. EXPECT MOST RAINFALL AMOUNTS TO BE IN THE ONE HALF TO 1 INCH TERRITORY ALTHOUGH LOCALLY HIGHER AMOUNTS ARE POSSIBLE. NOT TOO CONCERNED ABOUT FLOODING...BUT SOME MINOR POOR DRAINAGE ISSUES ARE POSSIBLE AND THIS WILL COINCIDE WITH THE MONDAY MORNING RUSH HOUR. THERE ALSO IS A LOW RISK FOR AN ISOLATED THUNDERSTORM OR TWO ACROSS THE SOUTHEAST NEW ENGLAND COAST. THE OTHER CONCERN IS POTENTIAL FOR WINDS ON MONDAY. WE COULD SEE SOUTH SOUTHEAST WIND GUSTS OF 30 TO 40 MPH DEVELOP ACROSS THE SOUTHEAST NEW ENGLAND COAST TOWARDS 12Z MONDAY...BUT INVERSION SHOULD KEEP THE STRONGEST WINDS JUST ABOVE OUR HEADS. THE ONE FLY IN THE OINTMENT IS IF WE CAN GENERATE A LITTLE FINE LINE THAT COULD ALLOW FOR A FEW LOCATIONS TO BRIEFLY TOUCH WIND ADVISORY CRITERIA ACROSS THE SOUTHEAST NEW ENGLAND COAST MONDAY MORNING. BULK OF THE RAIN IS OVER BY MON AFTERNOON...BUT A FEW LEFT OVER SPOT SHOWERS ARE POSSIBLE. GUIDANCE APPEARS TOO COOL FOR HIGHS GIVEN 850 MB TEMPS REMAINING AROUND +10C. SHOULD SEE HIGHS CLIMB WELL INTO THE 60S IN MANY LOCATIONS. NOT OUT OF THE QUESTION THAT SOME LOCALES APPROACH 70 IF WE CAN MUSTER A FEW PEEKS OF SUN. GUSTY SOUTHWEST WINDS POSSIBLE...ESPECIALLY IF WE CAN MIX OUT A BIT. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... */ HIGHLIGHTS... - DRY AND MILD AROUND TUESDAY - STORM SYSTEM ANTICIPATED WEDNESDAY INTO THURSDAY MORNING - GRADUALLY TURNING COLDER INTO THE FOLLOWING WEEKEND */ OVERVIEW AND MODEL CONSENSUS... ECHO SIMILAR SENTIMENTS PER WPC: MEANINGFUL SHORT-WAVE DIFFERENCES LEND TO LOW CONFIDENCE...SIGNIFICANT SPREAD DOWNSTREAM OF PACIFIC- ORIGIN ENERGY LEND TO FORECAST UNCERTAINTY. WITH UPSTREAM ISSUES IN HANDLING PACIFIC ENERGY...IT IS DIFFICULT TO RESOLVE DETAILS OFF THE E-COAST AND WE MAY NOT KNOW THE TRUE IMPACTS / OUTCOMES UNTIL WE GET WITHIN 2-3 DAYS OF THE TIMEFRAME. HAVE ONLY A MODEST CONFIDENCE IN THE FORECAST...BELOW-AVERAGE PREDICTABILITY. STILL BELIEVE THAT THE STORM ITSELF WILL REMAIN ON THE W-SIDE OF THE ENVELOPE OF MODEL SOLUTIONS /AGREED UPON BY WPC/ IN THE VICINITY OF THE 40N / 70W BENCHMARK SO DO NOT PREFER A DRY OUTCOME. CONSIDER OVER THE PAST COUPLE OF MONTHS ANOMALOUSLY WARM CONDITIONS HAVE PREVAILED S OF NOVA SCOTIA. LATELY THE TREND HAS BEEN COLD AIR SURGING S THROUGH THE C-CONUS TO THE GULF WITH NEW ENGLAND AVERAGING WITHIN THE E-PERIPHERY OF THE BROADER TROUGH. FEEL TREND CONTINUES WITH THIS FORECAST. LACK OF ARCTIC AIR INTO THE REGION...BELIEVE RIDGING OVER THE W-ATLANTIC WILL KEEP THE BULK OF SYNOPTICS ACROSS OUR REGION. SO FROM MONDAY NIGHT INTO TUESDAY NIGHT... DRY FORECAST. BLUSTERY W/SW FLOW ACROSS THE WATERS / SHORES WITH THE WARMER OCEAN. OVER THE INTERIOR DURING THE DAY TUESDAY AS MOSTLY CLEAR TO PARTLY CLOUDY CONDITIONS ALLOW FOR BOUNDARY-LAYER MIXING UP TO H9. GUSTS OF AROUND 30 TO 35 MPH... STRONGEST OVER THE SHORES AND ADJACENT WATERS. WILL REMAIN MILD BENEATH THE SW-FLOW. HIGHS TO NEAR- 60S AS A WARMER AIRMASS LINGERS ALOFT. NOW AS TO THE STORM... SYNOPTICALLY...SERIES OF PACIFIC WAVES INVOKE / MAINTAIN A H5 OPEN- WAVE TROUGH STRETCHING S INTO THE GULF. NO UPSTREAM BLOCKING WITH TELECONNECTIONS OF +AO/+NAO INDICATING A PROGRESSIVE FLOW OF MID- LEVEL IMPULSES. INTERACTING WITH THE OFFSHORE SW-NE FRONTAL BOUNDARY- BAROCLINIC ZONE AS IT BECOMES NEGATIVELY-TILTED RESULTS IN DEEPENING SFC-H85 LOW PRESSURE UP ALONG THE W-ATLANTIC PASSING WITHIN VICINITY OF THE 40N / 70W BENCH-MARK AROUND MIDNIGHT THURSDAY UP AGAINST AN INTERIOR REGION LACKING OF CANADIAN HIGH PRESSURE / ARCTIC AIR. INITIALLY...BAROCLINIC LEAF / OVER-RUNNING PATTERN OF BROADSCALE ASCENT YIELDS TOP-DOWN MOISTENING OF MID- TO LOW-LEVELS DYNAMICALLY COOLING TOWARDS EVENING SETTING UP THE ENVIRONMENT AHEAD OF THE MAIN STORM. UNDERCUTTING MARGINALLY COLD AIR AIDED BY SURFACE N/NE-FLOW WITH W/NW AGEOSTROPHIC FLOW OF INTERIOR ORIGIN LOOK TO KEEP THE N/W INTERIOR AROUND THE FREEZING MARK...MILD ACROSS THE COASTAL PLAIN. THERMAL FIELDS DIFFICULT TO DIAGNOSE WITH FORECAST UNCERTAINTY. KEY IS THE TRACK AND LOCATION OF H85 LOW / H925 < -2C. WHILE LIKELY TO SEE LOWER DEWPOINTS AND DRIER AIR N/W...ANOTHER KEY TO THE FORECAST TO THE TOP-DOWN MOISTENING IS WETBULBING AT THE SURFACE. AROUND MIDNIGHT THURSDAY INTO THURSDAY MORNING...SURFACE LOW LOOKS TO TRACK WITHIN THE VICINITY OF 40N / 70W BENCHMARK. UNCERTAIN AS TO DEPTH / STRENGTH / EXACT TRACK. EXPECT STRONG DEEP-LAYER ASCENT BUT FEEL BEST MOISTURE WILL BE E OF THE LOW WITHIN THE ANTI-CYCLONIC BRANCH OF THE WARM-CONVEYER-BELT /WCB/. THOUGH FORCING THROUGH A MOIST DENDRITIC GROWTH ZONE NW OF THE H85 LOW BENEATH THE RRQ OF THE UPPER-LEVEL-JET...HEAVIEST PRECIPITATION LOOKS TO REMAIN E/NE WITH THE LACK OF A STRONG H7 CLOSED LOW AND LITTLE EVIDENCE OF BANDING NOR -EPV /CYCLONIC BRANCH OF THE WCB LACKING/. COLD AIR CONTINUES TO UNDERCUT BUT MARGINAL /AROUND UPPER-20S TO LOW-30S/. NO NEIGHBORING ARCTIC AIRMASS IN PLACE. WETBULBING LIKELY CONTINUES. SNOWS N/W OF THE H85 LOW WITH RAIN ELSEWHERE. REMAIN UNCERTAIN AS TO AMOUNTS / HEADLINES AS MODEL RUNS /WHILE PERSISTENT/ CONTINUE TO WOBBLE WITH THE LOW AND POTENTIAL OUTCOMES. ACTIVITY CONCLUDING THANKSGIVING DAY MORNING REARWARD OF WHICH SOME STRONG SW-FLOW IS POSSIBLE. SEE THE ADDITIONAL DETAILS BELOW: SNOWS / HEAVY RAIN...HIGHEST CONFIDENCE ACROSS THE N/W INTERIOR FOR SNOW WITH HEAVY RAIN OVER SE MA...BUT STILL A LOT OF UNCERTAINTY AS HIGHLIGHTED IN THE DISCUSSION ABOVE. NOT EVEN DOES CIPS ANALOGS PROVIDE SIGNIFICANT CONFIDENCE...AND WITH THE WOBBLING OF MODEL SOLUTIONS CONCERNING THE TRACK / STRENGTH OF THE LOW...IT IS ANYONES GUESS AS TO SNOWFALL AMOUNTS. WINDS...SOME CONCERN DEPENDING THE DEPTH OF THE LOW. NE-FLOW AHEAD OF THE LOW WILL BE STRONG...BUT SOME CONCERN AFTER THE LOW PASSES WITH SW-FLOW IMPACTING THE S-COAST. LIKELY TO BE AN ACCOMPANYING STRONG LOW-LEVEL-JET. WITH THE 22.12Z GFS...CIPS ANALOGS HAVE A ROBUST CONFIDENCE OVER SE NEW ENGLAND /MAINLY THE CAPE AND ISLANDS/ FOR GUSTS EXCEEDING 35 MPH...POSSIBLY 40 MPH. BEARS MONITORING. COASTAL FLOODING...INCREASING WINDS OUT OF THE NE ALONG E MA INTO CAPE COD BAY. A BRIEF SURGE ANTICIPATED AS WINDS INCREASE AHEAD OF THE LOW-CENTER PASSAGE AROUND MIDNIGHT THURSDAY. THOUGH HIGH TIDES SHORTLY AFTER MIDNIGHT ARE FORECAST TO BE ASTRONOMICALLY LOW /10 FT FOR BOSTON/. WITH THE SHORT RESIDENCY TIME...AM NOT ANTICIPATING AT THIS TIME MUCH IN THE WAY OF IMPACTS BASED ON THE FORECAST MODEL PREFERENCE. THANKSGIVING AND BEYOND... CONTINUED PACIFIC ENERGY ROTATING THROUGH THE BROADER OPEN-WAVE H5 TROUGH WILL TO NEED TO BE MONITORED AS TO WHETHER MID-LEVEL IMPULSES INVOKE ANOTHER OFFSHORE LOW AROUND FRIDAY. ONCE THE H5 TROUGH PUSHES THROUGH THE REGION...EXPECT THE RETURN OF BELOW-AVERAGE TEMPERATURES USHERED BY NW-FLOW. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH MONDAY/... THROUGH 12Z...MAINLY VFR CIGS WITH POCKETS OF MVFR BERKSHIRES AND MONADNOCKS. SCT SHOWERS MOVING ACROSS W AND CENTRAL MA WITH ISOLD -FZRA IN THE BERKSHIRES. SW GUSTS TO 35 KT CAPE/ISLANDS WILL BE DIMINISHING THROUGH 12Z. AREAS OF LLWS POSSIBLE...MAINLY IN THECT VALLEY WHERE SFC WINDS SOUTH AND 2K WINDS WEST AROUND 40 KT. SUNDAY...HIGH CONFIDENCE. VFR. SUNDAY NIGHT INTO MONDAY...MODERATE CONFIDENCE. DETERIORATING CONDITIONS TO MVFR-IFR AS WIDESPREAD RAIN...LOCALLY HEAVY MOVES WEST TO EAST ACROSS THE REGION...BEGINNING AROUND 06Z CT VALLEY AND REACHING E COAST BY 10Z. ISOLD TSTM POSSIBLE MON MORNING NEAR THE SOUTH COAST. RAIN TAPERS OFF 12-16Z W TO E BUT IFR CIGS WILL LIKELY PERSIST THROUGH THE DAY ALONG WITH PATCHY FOG AS HIGHER DEWPOINTS MOVE IN. A PERIOD OF S WIND GUSTS TO 30-40 KT POSSIBLE 12-16Z MON ALONG THE S COAST AND ESPECIALLY CAPE/ISLANDS...THEN SW GUSTS TO 20-30 KT POSSIBLE IN THE AFTERNOON ENTIRE AREA. LLWS WILL ALSO BE A CONCERN LATE TONIGHT CT VALLEY SHIFTING TO SE NEW ENG MON MORNING AS SOUTHERLY LOW LEVEL JET 50-60 KT DEVELOPS AT 2K FT. KBOS TERMINAL...HIGH CONFIDENCE. KBDL TERMINAL...HIGH CONFIDENCE. SHOWERS MAINLY N OF TERMINAL. LLWS POSSIBLE EARLY THIS MORNING. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY. MONDAY NIGHT THROUGH TUESDAY NIGHT...MODERATE CONFIDENCE. W/SW-FLOW DIMINISHING THROUGH TUESDAY WITH GUSTS OF AROUND 30 KTS OVER SE-COASTAL TERMINALS THROUGHOUT MONDAY NIGHT. VFR. WEDNESDAY INTO THURSDAY MORNING...LOW CONFIDENCE. STORM WILL BRING SIGNIFICANT IMPACTS TO THE TERMINALS. THREATS CONSIDERED ARE STRONG WINDS AND THE THREAT OF +RA ALONG THE SHORES WITH SNOW SOMEWHERE ACROSS THE INTERIOR. EXACT SPECIFICS UNCERTAIN BUT EXPECTING A MIX OF IFR-VLIFR CONDITIONS. HEIGHT OF THE STORM WILL BE AROUND MIDNIGHT THURSDAY. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH MONDAY/... 7 PM UPDATE... TONIGHT...HIGH CONFIDENCE. STRONG W/SW FLOW CONTINUES EXCEEDING GALE FORCE. BOATS ACROSS THE S-WATERS REPORTING GUSTS UP TO AROUND 40 KTS AT TIMES. GALE FORCE WARNINGS CONTINUE WITH THE THREAT OF AVERAGE WIND GUSTS AROUND 35 KTS...ONLY SMALL-CRAFTS FOR NARRAGANSETT BAY AND BOSTON HARBOR WHICH SHALL REMAIN SHELTERED FROM THE WINDS. SEAS BUILDING 6-10 FEET OVER THE S-WATERS. SUNDAY...HIGH CONFIDENCE. GUSTY SW WINDS 25-30 KT IN THE MORNING WILL BE DIMINISHING THROUGH THE AFTERNOON DROPPING BELOW SCA DURING AFTERNOON AS LOW LEVEL JET WEAKENS. LEFT OVER SWELL WILL KEEPS SEAS ABOVE SMALL CRAFT ADVISORY THRESHOLDS ACROSS THE SOUTHERN WATERS THROUGH THE AFTERNOON. SUNDAY NIGHT AND MONDAY...MODERATE CONFIDENCE. WIND WILL REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS SUNDAY EVENING. LOW PRESSURE WILL THEN LIFT TOWARDS THE GREAT LAKES ALLOWING A STRONG LOW LEVEL JET TO DEVELOP VERY LATE SUN NIGHT INTO MON. THERE WILL BE AN INVERSION AND ITS ALWAYS UNCERTAIN AS TO HOW MUCH OF THIS WIND WILL BE ABLE TO MIX DOWN. AT THE VERY LEAST WILL HAVE STRONG SCA TO PERHAPS GALE FORCE SOUTHERLY WIND GUSTS VERY LATE SUN NIGHT INTO MON. SEAS WILL LIKELY BUILD TO BETWEEN 10 AND 15 FEET ACROSS THE SOUTHERN WATERS WITH VERY LONG FETCH. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY. MONDAY NIGHT THROUGH TUESDAY...MODERATE CONFIDENCE. WINDS TURNING W/SW REMAINING BLUSTERY WITH GUSTS AROUND 30 KTS FOR MONDAY NIGHT...RELAXING THROUGH THE DAY TUESDAY THOUGH GUSTS UP TO 30 KTS EXPECTED. WAVES AROUND 10 FEET ON THE OUTER WATERS EXPECTED INITIALLY INTO TUESDAY MORNING...DIMINISHING THEREAFTER. WEDNESDAY INTO THURSDAY...LOW CONFIDENCE. STORM WILL BRING SIGNIFICANT IMPACTS TO THE WATERS. THREATS CONSIDERED ARE GALE-FORCE WINDS AND THE THREAT OF HEAVY RAIN ACROSS THE WATERS. EXACT SPECIFICS UNCERTAIN BUT EXPECTING SEAS TO ENHANCE AROUND THE STORM CENTER WHICH LOOKS TO PASS IN VICINITY OF THE 40N / 70W BENCHMARK AROUND MIDNIGHT THURSDAY...VISIBILITIES REDUCED WITH HEAVY RAIN. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...GALE WARNING UNTIL 4 AM EST EARLY THIS MORNING FOR ANZ231-232. GALE WARNING UNTIL 3 AM EST EARLY THIS MORNING FOR ANZ233>235- 237-256. SMALL CRAFT ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR ANZ230-236-251. GALE WARNING UNTIL 6 AM EST EARLY THIS MORNING FOR ANZ250-254- 255. && $$ SYNOPSIS...FRANK/SIPPRELL NEAR TERM...KJC SHORT TERM...FRANK LONG TERM...SIPPRELL AVIATION...KJC/SIPPRELL MARINE...FRANK/SIPPRELL

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