Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 240842 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 342 AM EST MON NOV 24 2014 .SYNOPSIS... A WARM FRONT WILL BRING A BRIEF PERIOD OF HEAVY RAIN AND STRONG WINDS ALONG THE SOUTHEAST COAST THIS MORNING...FOLLOWED BY UNSEASONABLY MILD CONDITIONS MONDAY AFTERNOON. QUIET AND MILD TUESDAY WITH SOME GUSTY SW-WINDS. A SIGNIFICANT WINTER STORM IS POSSIBLE WEDNESDAY INTO WEDNESDAY NIGHT...BUT SPECIFIC OUTCOMES REMAIN UNCERTAIN. GRADUALLY TURNING COLDER INTO THE WEEKEND. && .NEAR TERM /THROUGH TODAY/... ***BRIEF PERIOD OF HEAVY RAIN THIS MORNING ALONG WITH STRONG WINDS ACROSS SOUTHEAST NEW ENGLAND*** RAIN BEGINNNING TO MOVE INTO WESTERN NEW ENG AND WILL OVERSPREAD THE REST OF SNE THROUGH DAYBREAK. POTENT LOW LEVEL JET +4SD WILL TRANSPORT ANOMALOUS PWATS /+3 TO +4SD/ NORTH INTO THE REGION TO BRING A PERIOD OF HEAVY RAINFALL TO THE REGION. ELEVATED THUNDER INDICES ARE MARGINAL AT BEST BUT CANT RULE OUT AN ISOLD TSTM IN THE COASTAL PLAIN AS THE NOSE OF LLJ MOVES ACROSS THE REGION. SYSTEM IS RATHER PROGRESSIVE AND NOTE THAT DRY SLOT IS ALREADY MOVING INTO CENTRAL PA SO DURATION OF STEADIEST RAINFALL WILL BE SHORT LIKELY LASTING NO MORE THAN 6 HOURS...WITH RAIN TAPERING OFF 13-16Z FROM WEST TO EAST. THIS WILL LIMIT QPF WITH RAINFALL AMOUNTS AVERAGING 0.50-1.00 ACROSS THE REGION WITH LOCALLY HIGHER ANOUNTS. JUST THE TYPICAL NUISANCE POOR DRAINAGE STREET FLOODING IS ANTICIPATED. STRONG WIND POTENTIAL ALONG SE NEW ENG COAST... FAIRLY POTENT LOW LEVEL JET 70-75 KT AT 925 MB WILL BE MOVING ACROSS SE NEW ENG 12-18Z. HOWEVER LOW LEVEL INVERSION IS PRESENT AT THE TIME THE JET IS MOVING THROUGH SO THIS WILL LIMIT HOW MUCH OF THIS WIND CAN MIX DOWN TO THE SURFACE IN THE ABSENCE OF ANY FINE LINE OF CONVECTION. AND THIS IS NOT REALLY AN IDEAL SITUATION FOR A FINE LINE GIVEN MARGINAL INSTABILITY AND NO COLD FRONT. TAKING ABOUNT 50 PERCENT OF THE MAGNITIDE OF THE JET OFTEN IS A DECENT STARTING POINT FOR ESTIMATING GUST POTENTIAL WITH THESE SOUTHERLY LOW LEVEL JETS WITH INVERSION IN PLACE. THIS SUGGESTS POTENTIAL FOR G35-40 KT WHICH IS RIGHT NEAR THE THRESHOLD OF WIND ADVISORY CRITERIA SO WE WILL CONTINUE THE ADVISORY FOR THE CURRENT AREA. HOWEVER...BEST CHANCE OF REALIZING GUSTS TO 45+ MPH WILL BE OVER CAPE/ISLANDS AND AREAS NEAR THE CAPE CAOD CANAL IN SE MA. THIS AFTERNOON... DRY SLOT WILL HAVE MOVED ACROSS THE REGION BY MIDDAY WITH RAINFALL EXITING THE REGION...BUT PLENTY OF LOW LEVEL MOISTURE IN PLACE WHICH WILL KEEP LOW CLOUDS ACROSS THE REGION WITH A FEW PASSING SHOWERS POSSIBLE. IT WILL BE WINDY AS STRONG LOW LEVEL WINDS REMAIN ACROSS THE REGION. SW WIND GUSTS 25-35 MPH EXPECTED AND POSSIBLY UP TO 40 MPH SE NEW ENG. 925 MB TEMPS 13-15C SO IT WILL BE A RATHER MILD DAY FOR LATE NOVEMEBER WITH TEMPS REACHING THE MID 60S ACROSS MANY LOCATIONS. 70 DEGREES WOULD BE POSSIBLE IF WE COULD GET SOME SUNSHINE BUT THIS DOESNT APPEAR LIKELY. && .SHORT TERM /TONIGHT/... WEAK COLD FRONT WILL BE MOVING INTO THE REGION SO CANT RULE OUT A FEW SHOWERS. OTHERWISE AREAS OF LOW CLOUDS WILL LINGER INTO THE EVENING BEFORE PARTIAL MOVES IN FROM THE WEST OVERNIGHT. IT WILL BE AN UNSEASONABLY MILD MIGHT AS LOW LEVEL COOLING DOESNT MOVE INTO THE REGION TIL LATE TONIGHT. MINS WILL BE IN THE 50S ACROSS MUCH OF THE REGION...EXCEPT 40S FAR W WHERE COOLING ARRIVES EARLIER. GUSTY SW WINDS WILL CONTINUE INTO THE EVENING BEFORE DIMINISHING OVERNIGHT. && .LONG TERM /TUESDAY THROUGH SUNDAY/... */ HIGHLIGHTS... - DRY AND MILD TUESDAY - STORM WEDNESDAY INTO THURSDAY...TRAVEL IMPACTS - TURNING COLDER INTO THE WEEKEND */ OVERVIEW AND MODEL CONSENSUS... MAIN FOCUS IS ON THE WEDNESDAY - THURSDAY TIMEFRAME. IN AGREEMENT WITH WPC: CONTINUED SPREAD OF GUIDANCE UPSTREAM RESULTING IN THE POOR RESOLVING OF DOWNSTREAM IMPACTS. INDIVIDUAL MODEL SOLUTIONS / ENSEMBLES STILL UNDECIDED ON THE RELATIVE TRACK / STRENGTH OF DOWN- STREAM ENERGY ACROSS THE NE-CONUS. DIFFICULT TO RESOLVE DETAILS ACROSS THE REGION OF WHICH WE MAY NOT KNOW THE TRUE OUTCOMES TILL ABOUT 2-3 DAYS PRIOR. NEVERTHELESS...CONTINUE TO WEIGH PREFERENCE UPON THE W-ENVELOPE OF FORECAST SOLUTIONS. BELIEVE THE 23.6Z / 23.12Z GFS AND THE 23.12Z EC ENSEMBLE MEAN OFFER THE MOST REASONABLE NE-TRACK OF THE SYSTEM IN THE VICINITY OF THE 40N/70W BENCHMARK S OF NANTUCKET. AGREE WITH WPC NOTING THERE HAS BEEN A WIDE SPREAD OF EC DETERMINISTIC SOLUTIONS ON THE W-HALF OF THE GUIDANCE ALONG WITH THE UKMET...WHILE THE CANADIAN REMAINS TO THE RIGHT. EXPECT A MODERATE DEVELOPMENT OF THE SYSTEM WHICH WILL RESULT IN IMPACTS ACROSS THE REGION...THOUGH THERE REMAINS A SIGNIFICANT AMOUNT OF UNCERTAINTY ON BOTH THE STRENGTH AND THE EXACT TRACK OF THE SYSTEM. ASIDE...EXPECTING SOME SORT OF RAIN AND / OR SNOW BAND SOMEWHERE ACROSS S NEW ENGLAND...WITH A CLIMATOLOGICAL PREFERENCE OF RAIN OVER COASTAL COMMUNITIES AND SNOWS FOR THE INTERIOR. THE ONLY CERTAINTY TO THE FORECAST IS THE TIMING OF THE SYSTEM OF WHICH IMPACTS ARE ANTICIPATED TO BEGIN DURING THE DAY WEDNESDAY... INCREASING INTO THE EVENING WITH THE HEIGHT OF THE STORM AROUND MIDNIGHT THURSDAY. MODEL CONSENSUS HAS THE STORM CONCLUDING THURSDAY MORNING. DETAILS... TUESDAY INTO TUESDAY NIGHT... DRY AND MILD. HIGH PRESSURE IN CONTROL BENEATH THE DRY-SLOT REARWARD OF THE DEPARTING LOW OVER THE ST LAWRENCE RIVER VALLEY IN CANADA. AM EXPECTING BLUSTERY SW-FLOW WITH GUSTS 30-35 MPH ALONG THE S-COAST. WINDS RELAXING INTO THE EVENING. LIGHT FLOW OVERNIGHT COULD MAKE FOR A GOOD RADIATIVE COOLING SETUP. BUT ANTICIPATING MID- TO HIGH-LEVEL CLOUDS TO INCREASE FROM THE S INTO WEDNESDAY MORNING LIMITING THE POTENTIAL. WEDNESDAY INTO WEDNESDAY NIGHT... SYNOPTICALLY...SUCCESSIVE PACIFIC-IMPULSES MAINTAIN AN OPEN-WAVE H5 TROUGH INTO THE GULF. UNDERGOING A NEGATIVE-TILT ACROSS THE E-CONUS INITIATES AND INTENSIFIES AN AREA OF LOW PRESSURE FROM THE N-GULF NE OVER THE W-ATLANTIC ACROSS THE 40N/70W BENCHMARK S OF NANTUCKET BY MIDNIGHT THURSDAY. NO APPRECIABLE DOWNSTREAM BLOCKING SIGNIFIES A PROGRESSIVE-FLOW PATTERN /+NAO/ RESULTING IN THE ABSENCE OF A CLOSED- LOW PATTERN ABOVE H7 /LESS EMPHASIS OF A CYCLONIC BRANCH OF THE WARM CONVEYER BELT/...WHILE LOW PRESSURE TROUGHING OVER THE GREAT LAKES ASSOCIATED WITH A STRONG POLAR-LOW HOLDS ARCTIC AIR REARWARD ACROSS C-CANADA /+AO/ RESULTING IN THERMAL PROFILES AROUND THE FREEZING MARK OVER S NEW ENGLAND. TOWARDS EVENING...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 MODEST W-COMPONENT OF AGEOSTROPHIC FLOW...AND DRIER AIR N/W INITIALLY...AM EXPECTING WETBULBING TOWARDS THE DEWPOINT AROUND THE FREEZING MARK THE DIVISION OF WHICH MAY BE ALONG A POSSIBLE COASTAL FRONT SETUP. OVERNIGHT...INTENSIFYING LOW SWEEPS NE IN THE VICINITY OF THE 40N / 70W BENCHMARK S OF NANTUCKET. WITH A PROGRESSIVE FLOW-PATTERN AND LACK OF A CLOSED LOW ABOVE H7...MUCH OF THE EMPHASIS IS WITH THE ANTI-CYCLONIC BRANCH OF THE WCB. NEVERTHELESS A FRONT-END THUMP IS ANTICIPATED WITH SLANTWISE ASCENT / FORCING PER FRONTOGENESIS NW OF H85 LOW EXTENDED E...ALONG WITH INDICATIONS OF WEAK TROWALING TOWARD THE NW-QUADRANT OF THE 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 SW-NE BAND SIGNATURE ACROSS S NEW ENGLAND...THOUGH WHERE EXACTLY REMAINS UNCERTAIN AS IS THE EXACT TRACK AS WELL AS THE DEPTH / STRENGTH OF THE STORM. IF A COASTAL FRONT SETUP EMERGES BENEATH NEAR-ISOTHERMAL PROFILES JUST BELOW FREEZING UP TO H7 PER THE PREFERRED MODEL SOLUTIONS NOTED EARLIER...THEN WOULD EXPECT INTERIOR SNOWS /WITH A NEAR 1:10 RATIO/ AND COASTAL RAINS. KEY TO THIS ENTIRE FORECAST IS THE TRACK OF THE H85 LOW ALONG WITH H925 TEMPERATURES AT OR BELOW -2C. THE DIVIDING LINE IS VARIED AMONG PREFERRED MODEL SOLUTIONS. CIPS ANALOG GUIDANCE DOES WEIGH SOME INDICATION PER PROBABILITIES OF > 2 INCHES OF SNOW. LOW CONFIDENCE FORECAST. 23.12Z EC / UKMET CONTINUE TO BE ON THE WARMER-END OF SOLUTIONS. IF THE 23.12Z GFS / GEFS AND 23.15Z SREF ARE CORRECT WITH THE TRACK OF THE H85 / SURFACE LOW...WHICH IS IN THE MIDDLE OF THE GUIDANCE SPREAD /CANADIAN THE FAR E SOLUTION/ THEN WOULD EXPECT A PLOWABLE SNOW ACROSS THE INTERIOR N/W OF THE I-95/495 CORRIDOR...KEEPING IN MIND THERE IS LIKELY WIGGLE ROOM OF THE RAIN / SNOW BAND DUE TO THE UNCERTAINTY IN THERMAL PROFILES THIS FAR OUT IN THE FORECAST. SO WITH THAT BEING SAID...WILL NOT ISSUE OUT ANY SNOW- FALL GRAPHICS WITH THIS FORECAST. THERE IS ABSOLUTELY NO CERTAINTY AS TO SNOW-OUTCOMES. CIPS ANALOGS HAVE TONED DOWN ON THE WIND PROBABILITIES. BUT WITH THE AFOREMENTION MODEL PREFERENCE...WILL NEED TO WATCH THE 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. 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. ALL SORTS OF DEPENDENCIES AND INTANGIBLES. ITS A HARD KNOCK LIFE. 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 /08Z MONDAY THROUGH FRIDAY/... 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 TODAY...CONDITIONS DETERIORATING TO MVFR/IFR SW TO NE 08-12Z AS WIDESPREAD RAIN...LOCALLY HEAVY OVERSPREADS THE REGION. RAIN WILL BE EXITING 14-16Z WITH A FEW SHOWERS POSSIBLE IN THE AFTERNOON...BUT MVFR/IFR CIGS WILL PERSIST. S WIND GUSTS TO 35-40 KT POSSIBLE ACROSS SE NEW ENG AND ESPECIALLY CAPE/ISLANDS 12-16Z...THEN SW GUSTS TO 25-35 KT DURING THE AFTERNOON. LLWS LIKELY AS 2K FT WINDS 45-55 KT. TONIGHT...MVFR-IFR CONDITIONS GRADUALLY IMPROVE TO VFR IN THE EVENING ACROSS W AND N TERMINALS...BUT NOT UNTIL AFT 06Z ACROSS SE NEW ENG. BLUSTERY SW WIND GUSTS 25-35 KT IN THE EVENING DIMINISHING OVERNIGHT. KBOS TERMINAL...MODERATE CONFIDENCE. KEPT CIGS ABOVE IFR WITH GUSTY S WINDS...BUT A BRIEF PERIOD OF IFR POSSIBLE. KBDL TERMINAL...MODERATE CONFIDENCE. LLWS WILL BE OF GREAT CONCERN IN THE MORNING WITH SOUTHERLY LLJ AND WEAKER E/SE FLOW NEAR THE SURFACE. OUTLOOK...TUESDAY THROUGH FRIDAY. TUESDAY THROUGH TUESDAY NIGHT...MODERATE CONFIDENCE. W/SW-FLOW DIMINISHING THROUGH TUESDAY WITH GUSTS OF AROUND 30 KTS OVER SE-COASTAL TERMINALS INITIALLY TUESDAY MORNING. VFR. WEDNESDAY INTO THURSDAY MORNING...LOW CONFIDENCE. SIGNIFICANT STORM ANTICIPATED. POSSIBLE THREATS OF A PLOWABLE SNOW OVER INTERIOR S NEW ENGLAND...WITH STRONG NE WINDS OVER E MA / CAPE COD / ISLANDS...MAYBE EVEN +RA. MIX OF IFR-VLIFR ANTICIPATED. STORM IMPACTS BEGINNING WEDNESDAY ENHANCING WEDNESDAY NIGHT. HEIGHT OF THE STORM AROUND MIDNIGHT THURSDAY...CONCLUDING INTO THURSDAY MORNING. LATER-THURSDAY INTO FRIDAY...LOW CONFIDENCE. IMPROVING VFR. BUT MUCH OF THIS DEPENDS ON STORM MORPHOLOGY. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. .SHORT TERM /THROUGH TONIGHT/...MODERATE CONFIDENCE. STRONG LOW LEVEL JET WILL BRING SOUTHERLY GALE FORCE WIND GUSTS TO THE WATERS TODAY. WHILE INVERSION IS PRESENT WHICH WILL LIMIT STRONGEST WINDS FROM MIXING DOWN STILL THINK GUSTS TO 35-40 KT POSSIBLE SO GALE WARNINGS WILL CONTINUE. SW GALES WILL LINGER INTO THE EVENING ACROSS THE OUTER WATERS BEFORE DIMINISHING OVERNIGHT. SEAS WILL BUILD TO BETWEEN 10 AND 15 FEET ACROSS THE SOUTHERN WATERS. REDUCED VSBYS THIS MORNING IN RAIN AND FOG. OUTLOOK...TUESDAY THROUGH FRIDAY. TUESDAY INTO TUESDAY NIGHT...MODERATE CONFIDENCE. WINDS TURNING W/SW REMAINING BLUSTERY WITH GUSTS AROUND 30 KTS FOR TUESDAY MORNING...RELAXING THROUGH THE DAY. WAVES AROUND 10 FEET ON THE OUTER WATERS TUESDAY MORNING...DIMINISHING THEREAFTER. WEDNESDAY INTO THURSDAY...LOW CONFIDENCE. SIGNIFICANT STORM ANTICIPATED PASSING NEAR THE 40N/70W BENCHMARK S OF NANTUCKET. POSSIBLE THREATS OF STRONG NE GALES OVER E MA / CAPE COD / ISLANDS...INCLUDING ALL ADJACENT AND OUTER WATERS. HEAVY RAIN LENDING TO REDUCED VISIBILITIES AT TIMES. STORM IMPACTS BEGINNING WEDNESDAY ENHANCING WEDNESDAY NIGHT. HEIGHT OF THE STORM AROUND MIDNIGHT THURSDAY...CONCLUDING INTO THURSDAY MORNING. && .TIDES/COASTAL FLOODING... ASTRONOMICAL TIDES ARE FAIRLY HIGH DURING THIS MORNINGS HIGH TIDE CYCLE. WITH SOUTHERLY GALES EXPECTED...A STORM SURGE OF 1.5 TO 2 FT IS LIKELY ALONG THE SOUTH COAST WITH HIGHEST SURGE EXPECTED IN NARRAGANSETT BAY. THIS MAY BRING A FEW LOCATIONS TO MINOR FLOOD. THE MAIN THREAT FOR MINOR COASTAL FLOODING WILL BE ALONG NARRAGANSETT BAY AND WESTPORT HARBOR DUE TO SOUTHERLY FETCH. COASTAL FLOOD ADVISORIES CONTINUE FOR THE SOUTH COAST. NO FLOODING IS EXPECTED ALONG THE EAST COAST. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...WIND ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR MAZ018>024. COASTAL FLOOD ADVISORY FROM 7 AM TO 11 AM EST THIS MORNING FOR MAZ020>022. NH...NONE. RI...WIND ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR RIZ003>008. COASTAL FLOOD ADVISORY FROM 7 AM TO 11 AM EST THIS MORNING FOR RIZ002-004>007. MARINE...GALE WARNING UNTIL 10 PM EST THIS EVENING FOR ANZ231>235-237- 250-251-254>256. SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR ANZ230. GALE WARNING UNTIL 2 PM EST THIS AFTERNOON FOR ANZ236. && $$ SYNOPSIS...KJC/RLG NEAR TERM...KJC SHORT TERM...KJC LONG TERM...RLG AVIATION...KJC/RLG MARINE...KJC/RLG TIDES/COASTAL FLOODING...

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.