Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 170714 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 215 AM EST WED DEC 17 2014 .SYNOPSIS... A WAVE OF LOW PRESSURE WILL BRING A PERIOD OF RAIN TONIGHT INTO EARLY WEDNESDAY BEFORE TAPERING TO A FEW SHOWERS. ANOTHER ROUND OF SNOW OR RAIN SHOWERS POSSIBLE WEDNESDAY NIGHT INTO THURSDAY... ESPECIALLY NORTH OF THE MASS PIKE. HIGH PRESSURE BRINGS DRY AND NEAR SEASONABLE CONDITIONS LATE THIS WEEK. STRENGTHENING LOW PRESSURE IS FORECAST TO PASS SOUTHEAST OF NEW ENGLAND SOMETIME THIS WEEKEND INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... 215 AM UPDATE... A DEVELOPING SECONDARY AREA OF LOW PRESSURE AND AMPLE MOISTURE ALLOWING BRIEF BURST OF HEAVY RAIN TO DEVELOP ACROSS CT AND NEAR THE SOUTH COAST. THIS RAIN SHOULD RAPIDLY MOVE NORTHWARD OVER THE NEXT FEW HOURS. SHOWALTER VALUES DROPPING TO NEAR ZERO MAY RESULT IN AN ISOLATED THUNDERSTORM OR TWO ACROSS EASTERN NEW ENGLAND. BULK OF THE RAIN SHOULD RAPIDLY COME TO AN END BETWEEN 7 AND 9 AM ACROSS MOST OF THE EASTERN MA COAST...AS LOW PRESSURE LIFTS TO THE NORTHEAST OF THE REGION. THE OTHER CONCERN WILL BE FOR AREAS OF FOG EARLY THIS MORNING...PARTICULARLY IN CENTRAL AND NORTHEAST MA. WILL CONTINUE TO COVER THIS WITH A SPECIAL WEATHER STATEMENT AND THINK RAIN WILL PRECLUDE THE NEED FOR A DENSE FOG ADVISORY. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/... WEDNESDAY... MAIN FOCUS FOR SHOWERS EARLY WED MORNING WILL BE ACROSS CENTRAL AND NE MA BEFORE DEEPER MOISTURE AND MID LEVEL OMEGA MOVES TO THE N. OTHERWISE...MUCH OF THE DAY WILL LIKELY BE DRY OTHER THAN A FEW PASSING SHOWERS. BEST CHANCE FOR AFTERNOON SHOWERS LATER IN THE DAY WILL BE ACROSS W MA AS MID LEVEL LOW AND SHORTWAVE APPROACH FROM THE WEST. IT WILL BE A MILD DAY WITH TEMPS REACHING INTO THE MID/UPPER 40S ACROSS MUCH OF THE REGION AND AROUND 50 DEGREES NEAR THE COAST WHERE A FEW BREAKS OF SUNSHINE POSSIBLE. OTHERWISE...MAINLY CLOUDY SKIES WILL PREVAIL. WEDNESDAY NIGHT... MID LEVEL LOW FORECAST TO TRACK ACROSS CENTRAL/NORTHERN NEW ENG WED NIGHT AS THE COLUMN COOLS FROM TOP DOWN. BEST FORCING AND MOISTURE WILL BE ALONG AND ESPECIALLY TO THE NORTH OF THE MID LEVEL CENTER SO BEST CHANCE OF SNOW SHOWERS WILL BE ACROSS N NEW ENG. HOWEVER...WILL LIKELY SEE A FEW RAIN/SNOW SHOWERS SPILLING INTO SNE...ESPECIALLY N MA WHICH WILL BE ON SOUTHERN EDGE OF DEEPER MOISTURE AND QG FORCING. ANY ACCUM WILL BE LIGHT...AN INCH OR LESS AND CONFINED TO HIGHER TERRAIN. GUSTY WEST WINDS DEVELOPING OVERNIGHT AS LOW PRES DEEPENS IN THE GULF OF MAINE. GUSTS TO 30 MPH POSSIBLE. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... HIGHLIGHTS... * SNOW SHOWERS ACROSS THE INTERIOR THROUGH MIDDAY THURSDAY * DRY WEATHER WITH NEAR OR SLIGHTLY BELOW TEMPS FRIDAY AND SAT * POSSIBLE COASTAL SYSTEM SAT NIGHT THROUGH SUN NIGHT OVERVIEW AND MODEL PREFERENCES... 12Z OP MODEL RUNS APPEAR IN FAIRLY GOOD AGREEMENT EARLY IN THE MEDIUM RANGE PERIOD...BUT UPPER LEVEL SPLIT FLOW ACROSS THE LOWER 48 LEADS TO TIMING DIFFERENCES INTO THIS WEEKEND AND BEYOND. THE BIG ISSUE APPEARS TO BE IN PHASING SOUTHERN STREAM ENERGY INTO POSSIBLE COASTAL CYCLOGENESIS LATE THIS WEEKEND INTO EARLY NEXT WEEK. OVERALL H5 PATTERN APPEARS FLAT UNTIL THE SOUTHERN STREAM SHORT WAVE WORKS OUT OF THE 4 CORNERS REGION AND STARTS DIGGING...WHILE THE NORTHERN STREAM REMAINS RATHER FAST. THE 12Z ECMWF/GFS APPEAR TO KEEP THIS SYSTEM RATHER WEAK AND WELL S OF THE REGION WHILE THE GGEM IS STRONGER AND EVEN FURTHER OFFSHORE. DID NOTE SOLUTION DIFFERENCES BETWEEN THE 00Z AND 12Z EC OP RUN...WITH THE 12Z RUN MOVING THE LATE WEEKEND LOW PRES FASTER THAN ITS 00Z COUNTERPART. WITH THE 00Z AND 12Z OP CANADIAN GGEM BEING FAST OUTLIERS...LEANED TOWARD A BLEND OF THE EC ENSEMBLE MEANS WITH A BIT OF THE GFS OP RUN AS THIS SHOWED DECENT RUN TO RUN CONSISTENCY VS. THE EC OP RUN... ALONG WITH PREVIOUS FORECAST FOR CONTINUITY. THIS WAS NOT TOO FAR FROM THE PREVIOUS FORECAST...THOUGH STILL QUITE A BIT OF UNCERTAINTY ESPECIALLY WITH THE TRACK AND INTENSITY OF THE LATE WEEKEND SYSTEM. DETAILS... THURSDAY...HIGH CONFIDENCE. AS H5 CUTOFF LOW ELONGATES ACROSS THE NORTHEAST U.S. ON THU... SURFACE LOW EXITS TO THE MARITIMES. WILL STILL SEE A BIT OF LEFTOVER MOISTURE AS CYCLONIC FLOW LINGERS MAINLY THROUGH MIDDAY. SOME DRYING DOES FILTER INTO S COASTAL AREAS ON GUSTY W-NW WINDS. MAY SEE SOME LIGHT SNOW ACCUMULATIONS ACROSS THE HIGHER TERRAIN OF NW MA...GENERALLY LESS THAN AN INCH. CORE OF COLDEST AIR REMAINS W OF THE REGION INTO THU NIGHT...SO EXPECT HIGHS MAINLY AROUND SEASONAL NORMS. FRIDAY AND SATURDAY...MODERATE TO HIGH CONFIDENCE. SURFACE HIGH PRES WILL REMAIN ACROSS THE REGION WHILE UPPER LEVEL CUTOFF LOW EXITS TO THE MARITIMES. DRY CONDITIONS WILL BE IN PLACE THROUGH MOST OF THIS PERIOD WITH TEMPS RUNNING CLOSE TO OR SLIGHTLY BELOW SEASONAL NORMALS. HIGH PRES CENTER WILL PASS ACROSS SOUTHERN QUEBEC BY SATURDAY WHICH WILL ALLOW WINDS TO VEER TO NE-E OVER TIME THOUGH REMAIN RATHER LIGHT. BIG QUESTION AT THIS POINT WILL BE HOW QUICKLY THE LOW THAT DEVELOPS OVER THE EASTERN GULF OF MEXICO MOVES TO THE SE U.S. COAST AND BRING ITS LEADING EDGE OF MOISTURE NORTHWARD. FOR NOW...HAVE KEPT WITH PREVIOUS FORECAST TRENDS AND BROUGHT INCREASING CLOUDS FROM S-N DURING THE DAY. KEPT A DRY FORECAST GOING ALONG WITH SEASONAL TEMPS. SATURDAY NIGHT THROUGH SUNDAY NIGHT...LOW CONFIDENCE. OP MODEL TIMING IS STILL SUSPECT WITH THE PHASING OF THE SPLIT FLOW AS LOW PRES WORKS NE. ONE CONSISTENT THING HAS BEEN THE FLATNESS OF THE WAVE ALONG WITH SECOND SHORT WAVE TRYING TO WORK INTO THIS SYSTEM. ANOTHER QUESTION IS HOW MUCH QPF TO EXPECT WITH THIS FEATURE. BLENDING OF PREVIOUS FORECAST WITH ENSEMBLES AND WPC GUIDANCE GAVE SOME CONSISTENCY ON THIS FORECAST PACKAGE. KEPT ONLY CHANCE POPS GOING FOR NOW...BUT HAVE SOME CONFIDENCE THAT PRECIP WILL OCCUR SOMETIME DURING THIS TIMEFRAME BUT ONSET AND EXIT ARE STILL VERY MUCH IN QUESTION. AT THIS POINT...LOOKS LIKE BEST SHOT OF PRECIP WILL OCCUR LATE SAT NIGHT INTO EARLY SUNDAY NIGHT. NEXT QUESTION IS PTYPE. LOOKS LIKE GENERAL EASTERLY WINDS WILL BRING SOMEWHAT MILDER AIR ACROSS EASTERN AREAS...WITH SOME MIXED RAIN/SNOW A BIT FURTHER INLAND. QPF FORECASTED AMOUNTS VARIED WIDELY. LEANED TOWARD LIGHTER AMOUNTS WITH THE WEAKNESS OF THIS SYSTEM /FOR NOW/. ANOTHER QUESTION IS THE WIND...WHICH IS ALL DEPENDENT UPON STORM TRACK AND STRENGTH. WHILE THIS LOOKS LIKE AN OPEN WAVE VS. A DEEPENING STORM /FOR NOW/...SHOULD NOT HAVE TOO MANY WIND ISSUES. HOWEVER...IF STORM DOES TREND STRONGER HENCE HIGHER ONSHORE WINDS...MAY NEED TO CONTEND WITH COASTAL CONCERNS AS ASTRO TIDES ARE HIGH DURING SUN AND MON. WILL CONTINUE TO MONITOR MODEL RUNS AND ENSEMBLES CLOSELY. MONDAY AND TUESDAY...LOW CONFIDENCE. TIMING ISSUES VERY MUCH IN PLACE DURING THIS TIMEFRAME. AT THIS POINT...HAVE PUSHED PRECIP OFFSHORE AS ANOTHER HIGH BUILDS E. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY/...MODERATE TO HIGH CONFIDENCE. TODAY...IFR TO LIFR CONDITIONS IN SHOWERS AND FOG EXPECTED THROUGH EARLY TO MID MORNING. BURST OF HEAVY SHOWERS THROUGH 7 AM WITH EVEN AN ISOLATED THUNDERSTORM POSSIBLE ACROSS EASTERN NEW ENGLAND. BULK OF RAIN EXITS THE EASTERN MA COAST BY 9 AM. OTHERWISE...NORTHWEST FLOW BEHIND DEPARTING LOW PRESSURE SHOULD ALLOW MOST AREAS TO IMPROVE TO MVFR CONDITIONS BY AFTERNOON...BUT THE CAPE/ISLANDS MAY REMAIN IFR. BULK OF THE RAIN OVER BY MID MORNING...OTHERWISE DRY WEATHER DOMINATES TODAY BESIDES A PASSING SHOWER OR TWO. TONIGHT...MARGINAL VFR TO MVFR CEILING EXPECTED TONIGHT. IN ADDITION...A FEW RAIN/SNOW SHOWERS EXPECTED PARTICULARLY NORTH OF THE MA TURNPIKE. THIS MAY RESULT IN BRIEF IFR CONDITIONS...MAINLY ACROSS OUR NORTHERN ZONES. WEST TO NORTHWEST WIND GUSTS OF 20 TO 25 KNOTS DEVELOP ACROSS THE COASTAL PLAIN. THURSDAY...MARGINAL VFR TO MVFR CEILINGS EXPECTED. A LEFT OVER RAIN/SNOW SHOWER POSSIBLE MAINLY IN THE MORNING...BUT DRY WEATHER DOMINATES. NORTHWEST WIND GUSTS OF 20 TO 30 KNOTS EXPECTED. KBOS TERMINAL...MODERATE CONFIDENCE. IFR TO LIFR CIGS/VSBYS SHOULD IMPROVE TO MVFR THIS AFTERNOON AS SURFACE WINDS TURN NORTHWEST. LOW PROBABILITY OF AN ISOLATED THUNDERSTORM THROUGH 7 AM. KBDL TERMINAL...MODERATE CONFIDENCE. IFR TO LIFR CONDITIONS SHOULD IMPROVE TO MVFR BY AFTERNOON AS SURFACE WINDS TURN NORTHWEST. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY... THURSDAY NIGHT THROUGH SATURDAY...MODERATE TO HIGH CONFIDENCE. VFR. MID AND HIGH CLOUDS MOVE IN FROM S-N DURING SAT. SATURDAY NIGHT-SUNDAY...LOW CONFIDENCE...MAINLY FOR TIMING. VFR TO START...THEN AREAS OF MVFR-IFR CIGS/VSBYS FROM S-N. MAINLY RAIN ACROSS E MA/MOST OF RI...WITH MIXED RAIN/SNOW INLAND. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH WEDNESDAY NIGHT/...HIGH CONFIDENCE. SE WINDS LESS THAN 20 KT TONIGHT...THEN SHIFTING TO WEST WEDNESDAY WITH GUSTS INCREASING TO 25 KT DURING THE AFTERNOON OVER THE SOUTHERN WATERS. EXPECT GUSTS TO 30 KT WED NIGHT AS LOW PRES INTENSIFIES IN THE GULF OF MAINE. A FEW GALE FORCE GUSTS TO 35 KT POSSIBLE OVER WATERS SOUTH AND EAST OF CAPE COD. BUILDING SEAS WED AFTERNOON AND ESPECIALLY WED NIGHT...8 TO 10 FT OVER THE OUTER WATERS. OUTLOOK...THURSDAY THROUGH SUNDAY...MODERATE TO HIGH CONFIDENCE. THURSDAY...SMALL CRAFT CONDITIONS CONTINUE ON W-NW WINDS. LOW PROB OF GALE FORCE GUSTS OVER THE OUTER WATERS DURING THU. WINDS SLOWLY DIMINISH LATE THU NIGHT. SEAS UP TO 7-10 FT MAINLY OVER THE SOUTHERN OUTER WATERS...SLOWLY SUBSIDING THU NIGHT. FRIDAY-SATURDAY...NW WINDS DIMINISH BELOW SMALL CRAFT DURING FRI AND REMAIN BELOW SMALL CRAFT THROUGH SAT. SEAS LINGER AOA 5 FT INTO EARLY FRI NIGHT THEN WILL SUBSIDE. SATURDAY NIGHT-SUNDAY...WINDS VEER TO NE-E SAT NIGHT...THEN INCREASE DURING SUNDAY. MAY SEE GUSTS TO 25 KT LATE SUN/SUN NIGHT. SEAS SLOWLY BUILD SUN NIGHT. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 6 PM EST THURSDAY FOR ANZ232>235-237. SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 6 PM EST THURSDAY FOR ANZ230-236. SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 6 PM EST THURSDAY FOR ANZ231-251. SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 6 PM EST THURSDAY FOR ANZ250-254>256. && $$ SYNOPSIS...KJC/EVT NEAR TERM...FRANK SHORT TERM...KJC LONG TERM...EVT AVIATION...FRANK/EVT MARINE...KJC/EVT

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