Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 262355 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 655 PM EST WED NOV 26 2014 .SYNOPSIS... A DEVELOPING COASTAL STORM WILL PASS SOUTH AND EAST OF NANTUCKET EARLY TONIGHT... THEN QUICKLY MOVE OFF TOWARD NOVA SCOTIA OVERNIGHT. THE VARIETY OF WEATHER IMPACTS FROM THIS STORM WILL DIMINISH OVERNIGHT...WITH WEATHER CONDITIONS IMPROVING FOR THANKSGIVING DAY. HIGH PRESSURE BUILDS OVER NEW ENGLAND FRIDAY AND SHIFTS OFFSHORE OVER THE WEEKEND. A WARM FRONT MOVES ACROSS THE REGION SATURDAY NIGHT. A COLD FRONT THEN SWINGS THROUGH NEW ENGLAND LATE SUNDAY NIGHT OR MONDAY. ANOTHER WARM FRONT APPROACHES NEXT WEDNESDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 650 UPDATE... 23Z SURFACE ANALYSIS PLACES THE COASTAL LOW CENTER NEAR 39.7N/71.6W...WHICH IS ABOUT 100 MILES SOUTH OF BLOCK ISLAND. STRONGEST PRESSURE FALLS ARE NOW EAST OF CAPE COD WHICH PROJECTS A NORTHEAST TRACK TO THE STORM THAT CROSSES 70W LONGITUDE ABOUT 30 MILES SOUTH OF NANTUCKET. EXTRAPOLATION WOULD HAVE THE LOW CROSSING 70W AROUND 9 PM AND DUE EAST OF TRURO AROUND MIDNIGHT. RADAR IS SHOWING EFFECTS OF A DRY SLOT MOVING UP TOWARD THE RI COAST. LOCATIONS IN THE COASTAL PLAIN MAY SEE PCPN DIMINISH STARTING AROUND 730 PM ON THE SOUTH COAST. LOCATIONS FARTHER WEST WILL DIMINISH AS THE LOW PASSES TO THE EAST. SO PCPN SHOULD DIMINISH THROUGH THE EARLY NIGHT. WE HAVE ADJUSTED TIMING OF POPS TO REFLECT THIS TIMING. BUT OVERALL THE GRIDS CONTINUE TO LOOK FINE SO ONLY SMALL CHANGES MADE. PREVIOUS DISCUSSION... *** WINTER STORM TRACKING CLOSE TO THE COAST TONIGHT *** IMPACTS... * HEAVY SNOW WESTERN AND CENTRAL MA INTO SOUTHERN NH * STRONG WINDS SOUTHEAST MA AND SOUTHERN RI * HEAVY RAIN AND MINOR POOR DRAINAGE/URBAN FLOODING MUCH OF RI AND SOUTHEAST MA SYNOPTIC OVERVIEW AND MODEL PREFERENCES... 12Z MODEL GUIDANCE HAS REMAINED CONSISTENT WITH 00Z/06Z GUIDANCE WITH THE SURFACE LOW PASSING OVER OR NEAR NANTUCKET. PATTERN RECOGNITION SUGGESTS AXIS OF HEAVIEST SNOW SHOULD BE ALONG AND JUST NORTHWEST OF H7 LOW TRACK...WHICH MODELS AGREE WILL BE ACROSS NORTHWEST MA INTO SOUTHWEST NH. SO HEAVIEST SNOW SHOULD BE INTO VT AND NH WITH THE HEAVIEST SNOW IN SOUTHERN NEW ENGLAND ACROSS NORTHWEST MA AND SOUTHWEST NH. INDEED...HEAVY SNOW IS FALLING ACROSS MUCH OF SOUTHERN NEW HAMPSHIRE AS WELL AS PORTIONS OF NORTHWESTERN MASSACHUSETTS AND NORTHERN CONNECTICUT. PTYPE AND SNOWFALL... THE AXIS OF HEAVIEST SNOW HAS BEEN AND SHOULD CONTINUE TO BE ALONG AND NORTHWEST OF A LINE FROM BDL-ORH-ASH. A SWATH OF 6-12 INCHES IS EXPECTED ACROSS THIS AREA. SNOW WILL LIKELY BE HEAVY AT TIMES ACROSS THIS REGION THROUGH APPROXIMATELY 9 PM WITH SNOWFALL RATES REPORTED AS 1-2 INCHES PER HOUR. THERE IS EVEN A LOW PROBABILITY OF THUNDERSNOW AS THE DRY SLOT APPROACHES THIS EVENING. STATIONS FARTHER UPSTREAM HAVE REPORTED THUNDER INCLUDING ALLENTOWN AND PHILADELPHIA PENNSYLVANIA AND LIGHTNING WAS SEEN AS CLOSE AS THE SOUTHERN PORTIONS OF THE HUDSON VALLEY. HEAVY WET SNOW HAS RESULTED IN SEVERAL DOWNED TREES/BRANCHES AS WELL AS POWER LINES ALREADY THIS AFTERNOON. THIS HAS RESULTED IN POWER OUTAGES ACROSS PORTIONS OF NORTHWEST MA AND SOUTHWEST NH. SOUTHEAST OF THE BDL-ORH-ASH LINE...AND ROUGHLY NORTHWEST OF THE I- 95 CORRIDOR...HAVE SEEN A MIX OF RAIN...SNOW AND SLEET. THIS IS LIKELY TO CONTINUE THROUGH THE REMAINDER OF THE AFTERNOON BEFORE CHANGING OVER TO ALL SNOW LATER THIS EVENING. THIS MIX OF SLEET WILL REDUCE SNOW TOTALS SOMEWHAT HOWEVER WILL ADD TO THE HAZARDOUS TRAVEL CONDITIONS. FARTHER SOUTH AND EAST INTO THE BOSTON TO PROVIDENCE CORRIDOR...A COLD RAIN HAS MIXED WITH SLEET AND EVEN FREEZING RAIN THIS AFTERNOON. THIS HAS ALREADY CAUSED SOME TRAFFIC ACCIDENTS ON SLIPPERY ROADS. THERE IS A LOW PROBABILITY OF SNOW MIXING IN LATER THIS AFTERNOON AND EVENING...RESULTING IN A SLUSHY INCH OR POSSIBLY TWO ACCUMULATING. NEVERTHELESS THIS WILL YIELD SLIPPERY TRAVEL... ESPECIALLY THROUGH 10PM WHEN PRECIP INTENSITY IS AT ITS GREATEST. FINALLY FOR SOUTHERN RI AND SOUTHEAST MA...MAINLY A WIND SWEPT RAIN STORM WITH MINOR POOR DRAINAGE/URBAN FLOODING AS RAINFALL TOTALS OF UP TO 2 INCHES POSSIBLE. HAVE LOWERED SNOWFALL TOTALS A BIT FROM THE I-95 CORRIDOR EASTWARD BASED ON THE MIX OF PRECIP CONTINUING THIS AFTERNOON. HOWEVER... THE ONLY CHANGE TO HEADLINES THAT WAS MADE WAS TO ADD A FREEZING RAIN ADVISORY FOR NORTHERN BRISTOL COUNTY IN MASSACHUSETTS AND ADDED FREEZING RAIN WORDING IN THE WINTER WEATHER ADVISORY FOR NORTHERN RHODE ISLAND. WHILE THERE ARE SOME AREAS...MAINLY IN THE ADVISORY AREA BUT ALSO IN THE WARNING AREA JUST BORDERING THE ADVISORY...THAT MAY NOT REACH THE SNOWFALL TOTALS GENERALLY ASSOCIATED WITH THESE HEADLINES...THE IMPACTS OF THE FIRST WINTER STORM OF THE SEASON DURING ONE OF THE BUSIEST TRAVEL DAYS OF THE YEAR ARE SUCH THAT WE FEEL THE WARNING IS JUSTIFIED. WINDS... A STRONG LOW LEVEL NORTHEAST JET WILL MOVE ACROSS RI AND SOUTHEAST MA INCLUDING CAPE COD AND THE ISLANDS AROUND 00Z. MODELS PROJECTING 40 TO 50 KT JET AT 925 MB. THIS COUPLED WITH STRONG PRESSURE FALLS AND RELATIVELY WARM OCEAN WATERS PROVIDING A WELL MIXED BOUNDARY LAYER WILL YIELD A MODERATE RISK OF 50 MPH WIND GUSTS FROM THE SOUTH COAST TO PLYMOUTH COUNTY/CAPE COD AND THE ISLANDS. WINDS MAY DECREASE OVER THE ISLANDS FOR A TIME THIS EVENING AS LOW MAKES IT CLOSEST APPROACH...SOMEWHERE NEAR NANTUCKET. TIMING OF STRONGEST WINDS CONTINUES TO BE LATE THIS AFTERNOON THROUGH JUST AFTER MIDNIGHT THURSDAY. && .SHORT TERM /6 AM THURSDAY THROUGH 6 AM THURSDAY/... SEE LONG TERM SECTION. && .LONG TERM /THURSDAY THROUGH WEDNESDAY/... BIG PICTURE... THANKSGIVING STARTS WITH A TWO-STREAM TROUGH OVER THE EASTERN USA AND A RIDGE OVER THE WEST. SHORTWAVE IN THE SOUTHERN STREAM MOVES OVER NEW ENGLAND THURSDAY...QUICKLY FOLLOWED BY A NORTHERN STREAM SHORTWAVE ON FRIDAY. THE FLOW GOES ZONAL OVER THE WEEKEND. A SHORTWAVE IN THE NORTHERN STREAM DROPS SOUTH FROM NORTHERN CANADA AND MOVES ALONG THE BORDER EARLY NEXT WEEK. A SECOND NORTHERN SHORTWAVE WILL DEEPEN OVER THE GREAT LAKES MIDWEEK DRAWING MILDER AIR NORTH OVER NEW ENGLAND. MODEL UPPER CONTOURS ARE SIMILAR THROUGH THE WEEKEND. THE GGEM EDGES FASTER EARLY NEXT WEEK. THE ECMWF BECOMES SHARPER WITH THE GREAT LAKES SHORTWAVE NEXT MIDWEEK BUT HAS A SIMILAR AXIS LOCATION AS THE GFS. WE FAVORED A BLEND OF THE MODEL DATA. THE DAILIES... THURSDAY-FRIDAY.... SOUTHERN AND NORTHERN STREAM SHORTWAVES MOVE ACROSS NEW ENGLAND. THIS MAINTAINS SOME WEAK LIFT IN AN AIRMASS THAT MAINTAINS DEEP MOISTURE THROUGH FRIDAY MORNING BEFORE DRYING. WITH THIS COMBINATION WE HELD ON TO CHANCE POPS THURSDAY ACROSS MUCH OF MASS AND NH. THE AIRMASS DRIES FRIDAY SO LAND AREAS SHOULD SEE A CLEARING TREND. OVER WATER THERE WILL BE AN 18C AIR-WATER TEMP DIFFERENCE...AN EQUILIBRIUM LEVEL OF 6400 FEET...AND A 12-14 KNOT NORTHWEST WIND. THIS SHOULD SUPPORT OCEAN EFFECT RAIN/SNOW SHOWERS. THE NORTHWEST FETCH WILL FAVOR MAINLY OFFSHORE SHOWERS ALTHOUGH PROVINCETOWN AND TRURO MIGHT GET CLIPPED. SATURDAY-SUNDAY... HIGH PRESSURE AXIS SHIFTS OFFSHORE. CLOUDS INCREASE IN THE WARM ADVECTION...BUT LIFT IS RATHER WEAK. WE INDICATED SLIGHT CHANCE POPS SATURDAY AS A WARM FRONT LIFTS NORTHEAST THROUGH THE REGION. DECREASING CLOUDS AND POPS SUNDAY AS THE WARM FRONT SHIFTS NORTH OF US. MONDAY...GREAT LAKES SHORTWAVE/SURFACE LOW SWINGS A COLD FRONT THROUGH NEW ENGLAND. THERE IS UNCERTAINTY AS TO TIMING OF THE FRONT...BUT LIMITED SUPPORT FOR LIFT AND SHOWERS FROM THE RIGHT ENTRANCE REGION OF A TRAILING UPPER JET. WE INDICATED CHANCE POPS AND STRETCHED THE TIME FROM EARLY MORNING THROUGH THE EVENING. TUESDAY-WEDNESDAY... HIGH PRESSURE MOVES ACROSS THE REGION TUESDAY AND BRINGS COOLER TEMPS. THE NEXT SHORTWAVE APPROACHES WEDNESDAY WITH WARM ADVECTION RUNNING OVER THE TOP OF THOSE COOLER TEMPS. WE USED CHANCE POPS FROM EARLY MORNING THROUGH THE DAY. TEMPERATURE PROFILES SUGGEST A MIX OF PCPN AT THE START ESPECIALLY NORTH/WEST OF BOSTON...BUT TEMPS WARM ENOUGH ON WEDNESDAY FOR RAIN. && .AVIATION /23Z WEDNESDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. .SHORT TERM /THROUGH TONIGHT/...MODERATE CONFIDENCE. TONIGHT...PRECIP WINDS DOWN STARTING 01Z ALONG THE SOUTH COAST AND 06Z IN SOUTHWEST NH. VSBYS 1/2 MILE TO 1 MILE IN HEAVY SNOW FROM WESTERN MASS INTO SOUTHERN NH...2-3 MILES IN NORTHERN CT...AND 3-5 MILES IN RAIN IN RI AND SOUTHEAST MASS. THESE WILL IMPROVE TO P6SM FROM SOUTH TO NORTH 01Z TO 06Z. MOST CIGS 500-1000 FEET WHICH SHOULD IMPROVE TO 1500-2000 FEET OVERNIGHT. STRONG NNE WINDS LINGER IN RI AND SOUTHEAST MASS EARLY TONIGHT...THEN DIMINISH AS DIRECTIONS SHIFT TO NORTHWEST OVERNIGHT. KBOS TERMINAL...HIGH CONFIDENCE IN TRENDS BUT LOWER CONFIDENCE IN EXACT TIMING. HEAVIEST PRECIP THROUGH 03Z KBDL TERMINAL...HIGH CONFIDENCE IN TRENDS BUT LOWER CONFIDENCE IN EXACT TIMING ESPECIALLY PTYPE. OUTLOOK...THURSDAY THROUGH MONDAY...MODERATE CONFIDENCE THURSDAY...MIXED VFR AND MVFR WITH SCATTERED RAIN/SNOW SHOWERS. DIMINISHING NORTHWEST WINDS. FRIDAY...VFR WITH NORTHWEST WINDS GUSTING 15-20 KNOTS. SATURDAY-SUNDAY...INCREASING SKY COVER BUT MAINLY VFR. LOW POTENTIAL FOR MVFR CIGS MOVING NORTH OFF THE OCEAN INTO CAPE COD AND ISLANDS. INCREASING SOUTHWEST WINDS AT 2000 FEET AGL...REACHING 35-40 KNOTS...WITH LIGHTER SOUTHWEST WINDS AT SURFACE. THIS WOULD MEAN POTENTIAL FOR LOW LEVEL WIND SHEAR SUNDAY. MONDAY...COLD FRONT MOVES ACROSS NEW ENGLAND WITH SCATTERED SHOWERS. BRIEF MVFR CIGS/VSBYS IN ANY SHOWERS. CONTINUED SOUTHWEST WINDS AHEAD OF THE FRONT WITH 35-40 KNOTS AT 2000 FEET AGL AND POTENTIAL LOW LEVEL WIND SHEAR. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. .SHORT TERM /THROUGH TONIGHT/... TONIGHT...HIGH CONFIDENCE. GALE CENTER TRACKS JUST SOUTH OF NANTUCKET AND EAST OF OUTER CAPE COD EARLY TONIGHT. THIS WILL RESULT IN A PERIOD OF NORTHEAST GALES WITH A LOW RISK OF A FEW STORM FORCE GUSTS. WINDS BECOME NORTHWEST AROUND OR SHORTLY AFTER MIDNIGHT. WINDS THEN DIMINISH OVERNIGHT. SEAS BUILD RAPIDLY DURING THE EARLY NIGHT...THEN SUBSIDE LATE TONIGHT. POOR VSBY IN HEAVY RAIN. OUTLOOK...THURSDAY THROUGH MONDAY...MODERATE CONFIDENCE. THURSDAY...NORTHWEST WINDS GUST NEAR 25 KNOTS EARLY BUT DIMINISH THROUGH THE DAY. SEAS START THE DAY ROUGH...WITH HEIGHTS 8 TO 12 FEET ON THE EXPOSED WATERS...THEN DIMINISH THROUGH THE DAY. SMALL CRAFT ADVISORY WILL BE NEEDED ON MOST WATERS. FRIDAY... LINGERING 5 TO 6 FOOT SEAS ON THE OUTER WATERS. NORTHWEST WINDS WILL GUST NEAR 20 KNOTS. A SMALL CRAFT ADVISORY MAY BE NEEDED ON SOME OF THE WATERS. SATURDAY-SUNDAY... SOUTHWEST WINDS GUSTING TO 20 TO 25 KNOTS SATURDAY AND AROUND 25 KNOTS SUNDAY. SEAS WILL BE LESS THAN 5 FEET SATURDAY AND THEN BUILD TO 5 TO 6 FEET ON THE EXPOSED WATERS SUNDAY. A SMALL CRAFT ADVISORY MAY BE NEEDED SUNDAY. MONDAY...SOUTHWEST WINDS GUSTING 20 TO 25 KNOTS UNTIL THE COLD FRONT MOVES THROUGH. WINDS THEN SHIFT TO WEST-NORTHWEST BEHIND THE FRONT WITH SIMILAR GUSTS. SEAS ON THE EXPOSED WATERS WILL BE 5 TO 8 FEET. A SMALL CRAFT ADVISORY MAY BE NEEDED. && .TIDES/COASTAL FLOODING... HIGH TIDE OF CONCERN IS SHORTLY AFTER MIDNIGHT TONIGHT. STRONGEST WINDS AND PRESSURE FALLS OCCUR DURING LOW TIDE THIS EVENING WITH WINDS AND SURGE EASING TOWARD HIGH TIDE. THUS IMPACTS WILL BE LIMITED WITH VERY MINOR EROSION AND TIDAL FLOODING. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR CTZ002>004. MA...WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR MAZ002>006- 008>012-026. WIND ADVISORY UNTIL 3 AM EST THURSDAY FOR MAZ019>024. WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR MAZ007- 013>017. NH...WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR NHZ011-012- 015. RI...WIND ADVISORY UNTIL 3 AM EST THURSDAY FOR RIZ005>008. WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR RIZ001>003. MARINE...GALE WARNING UNTIL 5 AM EST THURSDAY FOR ANZ230>237. GALE WARNING UNTIL 7 AM EST THURSDAY FOR ANZ250-251-254>256. && $$ SYNOPSIS...WTB/RLG NEAR TERM...WTB/RLG SHORT TERM...RLG LONG TERM...WTB AVIATION...WTB/RLG MARINE...WTB/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.