Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 162013 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 313 PM EST TUE DEC 16 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...ESPECIALLY NORTH OF THE MASS PIKE. A STRENGTHENING LOW PRESSURE CENTER IS EXPECTED TO PASS SOUTHEAST OF NEW ENGLAND LATE IN THE WEEKEND. IT IS UNCERTAIN AT THIS TIME IF THIS SYSTEM WILL PASS CLOSE ENOUGH TO PRODUCE PRECIPITATION ACROSS SOUTHERN NEW ENGLAND. && .NEAR TERM /THROUGH TONIGHT/... LATEST GUIDANCE SHOWING NEG TILT SHORTWAVE MOVING ACROSS NEW ENG LATE TONIGHT. PRIMARY LOW PRES MOVES ACROSS GT LAKES AS SECONDARY LOW DEVELOPS ACROSS SNE. RADAR INDICATING A BAND OF SHOWERS MOVING E FROM CENTRAL NY AND E PA/NJ AND THESE SHOWERS WILL OVERSPREAD SNE TONIGHT...REACHING CT VALLEY 00-02Z AND E COASTAL MA BY 06Z. THERMAL PROFILES ARE WARM ENOUGH TO SUPPORT RAIN FOR ALL SNE. GUIDANCE SHOWS GOOD SYNOPTIC FORCING AS AREA OF DEEPER MOISTURE MOVES THROUGH...SO WE HAVE CATEGORICAL POPS. DECENT INSTABILITY BURST EXPECTED LATE TONIGHT AS REFLECTED BY RAPID INCREASE IN KI/TT AND SWI DROPPING TO NEAR ZERO. THIS SUPPORTS A FEW HEAVIER SHOWERS AND MAYBE EVEN AN ISOLD TSTM LATE TONIGHT TOWARD DAYBREAK...ESPECIALLY ACROSS SE NEW ENG. RAINFALL OF 0.25 TO 0.5" EXPECTED WITH LOCALLY HIGHER AMOUNTS POSSIBLE. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... 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 THROUGH TUESDAY/... HIGHLIGHTS... * SNOW SHOWERS ACROSS THE INTERIOR WED NIGHT INTO THURS * DRY WEATHER AND AT OR BELOW AVG TEMPS FRIDAY INTO SAT * POSSIBLE COASTAL SYSTEM SUNDAY INTO MONDAY OVERVIEW... OVERALL 12Z GUIDANCE IS IN AGREEMENT SYNOPTICALLY...HOWEVER THERE ARE MANY ISSUES REGARDING THE SPLIT FLOW ESP FOR THE WEEKEND. IT DOES LOOK LIKE A PATTERN CHANGE IS GOING TO OCCUR AS UPPER LEVEL RIDGING BUILDS INTO CALIFORNIA AND HIGH PRESSURE IN CENTRAL CANADA MOVES TO EASTERN CANADA. THIS SHOULD FAVOR TROUGHING IN THE SW CONUS MOVING EASTWARD WHICH COULD KEEP OUR PATTERN ACTIVE BEGINNING NEXT WEEKEND. GUIDANCE TENDS TO HAVE ISSUES WITH THE PATTERN SHIFT AS WELL AS PHASING SO TIMING ON ANY SYSTEMS MAY SLOW DOWN OR EVEN SPEED UP. WHILE WE ARE IN TRANSITION...DEPARTING UPPER LEVEL LOW WILL PUSH TOWARDS THE MARITIMES BY LATE THURSDAY WITH RIDGING TO MOVING IN FRIDAY INTO SATURDAY. DIGGING SHORTWAVE INTO THE SE CONUS WILL DEVELOP A LOW PRESSURE SYSTEM IN THE MID-ATLANTIC. THIS SYSTEM MAY MOVE ACROSS THE BENCHMARK...THE CANAL OR WELL EAST OF THE BENCHMARK. FOR NOW TRENDED TOWARDS THE ENSEMBLES FOR THIS FORECAST BECAUSE OF THE AMOUNT OF UNCERTAINTY. DETAILS... WEDNESDAY NIGHT INTO THURSDAY...HIGH CONFIDENCE. UPPER LEVEL LOW WILL SET UP OVER NEW ENGLAND WEDNESDAY NIGHT BEFORE EXITING OFF INTO THE MARITIMES LATE THURSDAY. A SECONDARY SHORTWAVE WILL MOVE THROUGH THE FLOW AND OVER THE REGION ALLOWING FOR PRECIP TO DEVELOP AND CONTINUE INTO THURSDAY MORNING. STRONG CAA WILL MOVE IN BEHIND THE FIRST SHORTWAVE SO ANTICIPATE PRECIP TO BE MORE IN THE FORM OF SNOW...ESP AWAY FROM THE COASTLINE. THESE SNOW SHOWERS WILL BE MORE SCATTERED IN NATURE WED NIGHT THEN BEGIN TO BECOME MORE ISOLATED BY THURSDAY AS SHORTWAVE MOVES THROUGH AND DRY AIR PUSHES INTO THE AREA. AM NOT EXPECTING MUCH IN THE WAY OF ACCUMULATIONS BUT COULD SEE AN QUICK INCH ACROSS THE HIGHER ELEVATIONS INTO THE NW ZONES. TEMPERATURES THROUGH THIS PERIOD WILL BE AT OR BELOW AVERAGE AS STRONG CAA MOVES THROUGH WITHIN THE NORTHWEST FLOW. FRIDAY INTO SATURDAY...HIGH CONFIDENCE. AS UPPER LEVEL LOW SPINS INTO THE MARITIMES...HIGH PRESSURE WILL BUILD INTO SOUTHERN NEW ENGLAND. THIS SILL ALLOW FOR QUIET AND DRY WEATHER. TEMPERATURES WILL HOVER NEAR AVERAGE DURING THIS TIME PERIOD. SUNDAY INTO MONDAY...LOW CONFIDENCE. MAIN FOCUS OF THE FORECAST WAS ON THIS TRICKY TIME PERIOD. THE MODELS/ENSEMBLES HAVE OFFERED A VARIETY OF SOLUTIONS OVER THE PAST FEW DAYS FROM A VERY LOW AMPLITUDE AND FLAT WAVE MOVING THROUGH THE SOUTHEAST TO A WRAPPED UP SFC LOW HUGGING THE COAST INTO NEW ENGLAND. THE ECMWF ENSEMBLE MEAN HAS OFFERED THE BEST CONSISTENCY WHILE THE DETERMINISTIC ECMWF HAS BEEN LESS STABLE IN ITS DETAILS. THE GFS IS SHOWING A SYSTEM...BUT IT MORE OF A WAVE FOCUSING ON THE NORTHERN STREAM. THE GEFS SPREAD IS QUITE LARGE...BUT THERE ARE A FEW MEMBERS AGREEING WITH THE ECMWF ENSEMBLES. BECAUSE OF THE AMOUNT OF SPREAD...HAVE A VERY LOW CONFIDENCE ON THE FORECAST BUT TRENDED TOWARDS WPC AN A BLEND OF THE ENSEMBLES. OVERALL APPEARS THAT PRECIP WILL MOVE INTO THE REGION AND IMPACT SOUTHERN NEW ENGLAND BETWEEN THE SAT NIGHT INTO MONDAY TIME FRAME. THERE MAY BE ENOUGH LINGERING COLD AIR FROM DEPARTING HIGH PRESSURE THAT THERE COULD BE SOME SNOW ACROSS THE INTERIOR. HOWEVER IF THE STORM IS WELL EAST OF THE BENCHMARK THEN NO SNOW WILL OCCUR ACROSS THE INTERIOR AND IT MAY BE ACROSS THE COAST. SO APPEARS THAT THERE WILL BE P-TYPE ISSUES AND PERHAPS SOME WIND ISSUES IF THE STORM TRACKS WEST OF THE BENCHMARK. TIDES FOR THE MASS EAST COAST WILL BE ASTRONOMICALLY HIGH WITH 11.0 SUNDAY MORNING AND 11.4 MONDAY MORNING AT BOS. IF NE FLOW STRENGTHENS THEN ANTICIPATE A BUILD UP IN SEAS AS WELL AS SURGE. SO THERE COULD BE COASTAL FLOODING CONCERNS WITH THE SYSTEM. AS MENTIONED BEFORE...THIS IS A LOW CONFIDENCE FORECAST WITH MUCH SPREAD ACROSS THE GUIDANCE. HOWEVER THIS STORM WILL NEED TO BE WATCH OVER THE COMING DAYS. && .AVIATION /19Z TUESDAY THROUGH SUNDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH WEDNESDAY NIGHT/...MODERATE CONFIDENCE. THROUGH 00Z...WIDESPREAD MVFR CIGS WITH POCKETS OF IFR IN THE HIGHER ELEVATIONS. PATCHY DRIZZLE NEAR THE COAST. TONIGHT...WIDESPREAD MVFR LOWERING TO IFR IN STRATUS AND DEVELOPING PATCHY FOG. SHOWERS WILL OVERSPREAD THE REGION REACHING CT VALLEY 00-02Z AND E MA AROUND 06Z. WEDNESDAY...IFR CONDITIONS IN THE MORNING SHOULD IMPROVE TO MVFR DURING THE AFTERNOON FROM SW TO NE...AND POSSIBLY VFR NEAR THE CT VALLEY. SHOWERS SHOULD BE CONFINED TO NE HALF OF SNE EARLY IN THE MORNING...THEN DIMINISHING BY AFTERNOON. WEDNESDAY NIGHT...MIX OF VFR/MVFR CIGS. SCT SNOW SHOWERS LIKELY...ESPECIALLY NORTH OF THE MASS PIKE. KBOS TERMINAL...HIGH CONFIDENCE FOR IFR CONDITIONS DEVELOPING TONIGHT. LOWER CONFIDENCE ON TIMING. KBDL TERMINAL...HIGH CONFIDENCE FOR IFR CONDITIONS DEVELOPING TONIGHT. LOWER CONFIDENCE ON TIMING. OUTLOOK...THURSDAY THROUGH SATURDAY... THURSDAY...HIGH CONFIDENCE. MVFR CIGS IN SCATTERED SNOW SHOWERS. NORTHWEST WINDS NEAR 25 KTS. THURSDAY THROUGH SATURDAY...HIGH CONFIDENCE. VFR CONDITIONS EXPECTED. && .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 SATURDAY...MODERATE TO HIGH CONFIDENCE. ANTICIPATE SMALL CRAFT ADVISORY WINDS IN NW FLOW BEHIND THE DEPARTING SYSTEM WED INTO THU. SEAS WILL LIKELY BE NEAR OR ABOVE 5 FEET ACROSS THE OPEN WATERS WED INTO THU. LOW CONFIDENCE OF GALES WED NIGHT THANKS TO STRONG CAA OVER THE RELATIVELY WARM WATER. WINDS DIMINISHING AND SEAS SUBSIDING THU NIGHT AND LIKELY BELOW SMALL CRAFT ADVISORY LEVELS FRI THROUGH SAT. ALTHOUGH JUST BEYOND THE OUTLOOK PERIOD...WE CONTINUE TO MONITOR A POTENTIAL COASTAL STORM FOR LATE SATURDAY NIGHT AND SUNDAY. THERE IS A LARGE UNCERTAINTY IN THE TRACK AND INTENSITY OF THIS SYSTEM AND ANY CORRESPONDING IMPACT ON WINDS AND SEAS IN THE COASTAL WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 PM WEDNESDAY TO 7 AM EST THURSDAY FOR ANZ232>235-237. SMALL CRAFT ADVISORY FROM 7 PM WEDNESDAY TO 7 AM EST THURSDAY FOR ANZ230-236. SMALL CRAFT ADVISORY FROM 4 PM WEDNESDAY TO 7 AM EST THURSDAY FOR ANZ231-251. SMALL CRAFT ADVISORY FROM 7 AM WEDNESDAY TO 7 AM EST THURSDAY FOR ANZ250-254>256. && $$ SYNOPSIS...KJC NEAR TERM...KJC SHORT TERM...KJC LONG TERM...DUNTEN AVIATION...KJC/DUNTEN MARINE...KJC/DUNTEN

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