Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 281448 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1048 AM EDT SAT MAR 28 2015 .SYNOPSIS... LOW PRESSURE WILL PASS WELL OFFSHORE BUT A SURFACE TROUGH EXTENDING WESTWARD FROM THE LOW WILL CAUSE SNOW ACROSS MUCH OF SOUTHERN NEW ENGLAND THIS AFTERNOON AND EVENING. HIGH PRESSURE BUILDS OVER THE EASTERN USA WITH DRY WEATHER ON SUNDAY. ANOTHER BATCH OF PRECIPITATION IS POSSIBLE LATE SUNDAY NIGHT INTO MONDAY AHEAD OF A COLD FRONT. FAST MOVING LOW PRESSURE WILL BRING MORE LIGHT RAIN AND/OR SNOW SHOWERS TUESDAY NIGHT INTO WEDNESDAY. LOW PRES MAY APPROACH LATE NEXT WEEK WITH MORE PRECIPITATION. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1040 AM UPDATE... VERY TRICKY FORECAST CONTINUES. DESPITE MANY THOUGHT PROCESSES THIS MORNING...HAVE UPDATED THE FORECAST SNOW AMOUNTS BUT NOT QUITE ENOUGH FOR ADVISORIES IN NORTHERN RI AND EASTERN MA. INFRARED SATELLITE IMAGERY HAS SHOWN COOLING CLOUD TOPS ACROSS THE REGION THROUGHOUT THE MORNING. IN ADDITION...WE HAVE THE DEVELOPMENT OF A COMMA HEAD WHICH HAS LED TO PERIODS OF MODERATE SNOW ACROSS EASTERN LONG ISLAND NY AND VISIBILITIES HAVE DROPPED TO BELOW 1 MILE AT TIMES IN PARTS OF MA AND CT. A SURFACE TROUGH IS IN PLACE ACROSS THE SOUTH COAST...WHICH IS A WESTWARD EXTENSION FROM DEEPER OFFSHORE LOW PRESSURE. DEWPOINT TEMPERATURES HAVE DROPPED INTO THE LOWER AND MID 20S ACROSS WESTERN PORTIONS OF THE FORECAST AREA AND WILL BE SPREADING EAST...WHICH WOULD MEAN A BETTER CHANCE OF TEMPERATURES DROPPING DOWN TO THEIR WET-BULB LEVELS...A LITTLE LOWER THAN CURRENTLY FORECAST N AND W OF THE I-95 CORRIDOR. EARLIER MESOSCALE MODELS WERE SHOWING A SIGNIFICANT INCREASE IN PRECIPITATION RATES BETWEEN 18Z AND 00Z IN EASTERN MA. ALL OF THESE FACTORS WERE LEADING US TO BELIEVE THAT THERE COULD BE ADVISORY...3 TO PERHAPS EVEN 5 INCHES OF SNOW IN PARTS OF THE REGION BY THIS EVENING. HOWEVER...THE 12Z NAM SHOWS LESS PRECIPITATION IN THE 18Z TO 00Z TIME FRAME THAN IN THE 12Z TO 18Z TIME FRAME. RADAR IMAGERY SHOWS THE BEST PRECIPITATION SLIDING EASTWARD ALREADY. A COOPERATIVE WEATHER OBSERVER IN NORTH FOSTER RI REPORTED 1.4 INCHES OF SNOW...BUT ONLY ON GRASSY AREAS AND NOT ON THE PAVEMENT. GIVEN THAT THE SNOWFALL IS NOT HAVING A BIG IMPACT BECAUSE OF MELTING ON PAVEMENTS...WE HAVE OPTED TO HOLD OFF ON ANY ADVISORIES FOR NORTHERN RI/NORTHEAST CT/EASTERN MA AT THIS TIME. HAVE UPPED THE SNOWFALL TOTALS SLIGHTLY HOWEVER...TO 2 TO 3 INCHES ACROSS MUCH OF THE EASTERN HALF OF THE FORECAST AREA. THE NAM IS BULLISH ON SOUTHEAST MA INCLUDING CAPE COD AND THE ISLANDS GETTING PRECIPITATION IN THE FORM OF SNOW AND GREATER THAN 0.25" QPF FROM 00Z TO 06Z SO WILL BE WATCHING THAT AREA CLOSELY FOR POSSIBLE UPGRADES LATER THIS AFTERNOON. FARTHER TO THE WEST...ARE STILL GETTING SOME SNOW BANDS IN THE HIGHER TERRAIN AND A SPOTTER REPORTED 1.5 INCHES IN HUBBARDSTON MA. WE ARE THINKING THAT THE AXIS WILL SHIFT FARTHER TO THE EAST AS THE AFTERNOON PROGRESSES...THUS LIMITING AMOUNTS IN WESTERN PORTIONS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... TONIGHT...LOW CONFIDENCE. OFFSHORE LOW MOVES OFF THROUGH THE MARITIMES WHILE UPPER TROUGH MOVES OVERHEAD. THIS MAINTAINS THE POTENTIAL FOR PCPN WHILE COOLING NIGHTIME TEMPS WOULD FAVOR SNOW OR RAIN CHANGING TO SNOW. THE PIVOTING SURFACE TROUGH SHOULD MOVE OFFSHORE AFTER MIDNIGHT WITH ANY PCPN OVER OUR AREA DIMINISHING. BASED ON EXPECTED TEMPS AND LIGHT PCPN THROUGH THE DAY AND NIGHT WE PROJECT STORM TOTAL OF 1-3 INCHES IN THE HILLS AND AROUND 1 INCH IN THE LOWER TERRAIN. NORTH WINDS WILL PULL /YET AGAIN/ COLDER THAN NORMAL AIR ACROSS THE REGION. TEMPERATURES UPSTREAM OVERNIGHT HAVE BEEN IN THE TEENS AND LOWER 20S. CLOUDS MAY SLOW COOLING A LITTLE...SO WE FAVORED 15 TO 25 DEGREES. SUNDAY...HIGH CONFIDENCE. HIGH PRESSURE BUILDS OVER THE EASTERN USA SURFACE AND ALOFT. THIS SHOULD BRING SUNNY SKIES MOST AREAS. SOME LINGERING CLOUDS ARE POSSIBLE IN THE MORNING IN EASTERN MASS. TEMPS ALOFT SUGGEST HIGHS IN THE 30S...BUT WARM ADVECTION LATE IN THE DAY MAY NUDGE VALUES TO AROUND 40. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... HIGHLIGHTS... * A WEAK COLD FRONT WILL MOVE THROUGH ON MONDAY BRINGING SCT SHOWERS * MODERATING SPRING-LIKE TEMPS INTO NEXT WEEK * ALBERTA CLIPPER MOVES THROUGH TUESDAY NIGHT INTO WED * INCREASING CHANCES FOR PRECIP SOMETIME DURING THE EASTER WEEKEND OVERVIEW... ACTIVE PATTERN APPEARS TO BE SETTING UP OVER SOUTHERN NEW ENGLAND NEXT WEEK. FIRST SYSTEM IS ON MONDAY FOLLOWED BY A WAVE TUESDAY NIGHT AND FINALLY A SYSTEM THURS/FRIDAY. OVERALL...A QUICK MOVING RIDGE AND ASSOCIATED HIGH WILL DEVELOP ON SUNDAY BEFORE NORTHWEST FLOW SETS UP AS RIDGE BUILD OVER THE ROCKIES. THIS WILL ALLOW FOR SEVERAL WAVES TO PUSH THROUGH. AS MENTIONED EARLIER...LOW PRESSURE SYSTEM WILL MOVE ACROSS NORTHERN NEW ENGLAND DRAGGING A COLD FRONT WITH IT ON MONDAY. NEXT AN ALBERTA CLIPPER WILL DIVE INTO SOUTHERN NEW ENGLAND BY LATE TUESDAY INTO WEDNESDAY. LASTLY A NORTHERN AND SOUTHERN STREAM MERGER APPEARS TO APPROACH THURSDAY/FRIDAY. IT IS DIFFICULT TO ANY DETERMINISTIC MODEL OVER ANOTHER SINCE ALL FALL WITHIN THE MULTI-CENTER ENSEMBLE SPREAD. NEVERTHELESS... THE ECMWF HAS BEEN MORE CONSISTENT WITH SOME...NOT ALL...FEATURES ACROSS THE REGION THAN THE GFS AND HAS MORE SUPPORT FROM THE CMC/UKMET. NOTHING SHOWS GOOD MULTI-DAY CONTINUITY AND THE TREND HAS BEEN BOTH SLOWER AND QUICKER... DEPENDING ON THE SYSTEM OF INTEREST. THEREFOR TRENDED TOWARD WPC GUIDANCE FOR THIS FORECAST. DETAILS... * SUNDAY NIGHT INTO TUESDAY...HIGH CONFIDENCE. NEXT UPPER LEVEL SHORTWAVE WILL QUICKLY MOVE THROUGH NW FLOW ALOFT LATE SUNDAY INTO MONDAY. GUIDANCE SEEMS TO BE IN BETTER AGREEMENT WITH THIS SYSTEM KEEPING MOST OF SUN PM DRY AND BRINGING PRECIP EARLY MONDAY MORNING. SURFACE LOW ACROSS THE GREAT LAKES WILL PASS JUST NORTH OF SNE...DRAGGING ASSOCIATED COLD FRONT WITH IT. TEMPS AT THE ONSET LOOK TO BE COOL THEN WARM UP DURING THE DAY ON MONDAY PRIOR TO FRONTAL PASSAGE. AT THE ONSET OF PRECIP...EXPECT A FEW SNOW SHOWERS...BUT THEN TRANSITIONING TO RAIN FAIRLY QUICKLY AS TEMPS WARM UP. MOISTURE IS MARGINAL SO COVERAGE MAY BE MORE SCT ALONG THE FRONT. EXPECT VERY MINOR ACCUMULATIONS WITHIN ANY SNOW SHOWERS. BEHIND THE FRONT...WESTERLY WINDS WILL BE ON THE INCREASE AND GUSTING TO 25-30 MPH. TUESDAY WILL BE MOSTLY DRY AS SOUTHERN NEW ENGLAND IS SQUEEZED BETWEEN TWO SYSTEMS. WINDS WILL CONTINUE TO GUST THROUGH THE DAY. TEMPS WILL BE IN THE MID TO UPPER 40S BUT WITH THE WIND...IT WILL FEEL LIKE THE UPPER 30S. CLOUDS WILL BE ON THE INCREASE THROUGHOUT THE DAY AS NEXT SYSTEM APPROACHES. * TUESDAY NIGHT INTO WEDNESDAY...MODERATE CONFIDENCE. NEXT SHORT WAVE WILL QUICKLY DIVE THROUGH THE FLOW FROM CANADA AND MOVE JUST SOUTH OF SOUTHERN NEW ENGLAND. THE EC IS STILL MORE AMPLIFIED/STRONGER WITH THIS SYSTEM CUTTING OFF THE 850 MB LOW COMPARED TO THE GFS WHICH KEEPS AN OPEN WAVE. THIS HAS ALLOWED FOR PRECIP TO BE CLOSER TO SNE WHILE THE GFS PUSHES EVEN FARTHER SOUTH IMPACTING THE MID-ATLANTIC. OVERALL BELIEVE THAT LOCATIONS ALONG AND SOUTH OF THE PIKE HAVE THE BEST CHANCE TO SEE PRECIP. MODELS ARE SIMILAR ON THE TIMING BRINGING PRECIP IN OVERNIGHT AND PUSHING OUT BY LATE WED MORNING. THIS WILL ALLOW FOR TEMPS TO BE COOL ENOUGH FOR SNOW SHOWERS. WILL NEED TO CONTINUE TO WATCH THE TRENDS WITH THIS SYSTEM SINCE IT COULD PRODUCE A QUICK 1-2 INCHES OF SNOW ACROSS THE AREA. * WEDNESDAY NIGHT INTO FRIDAY...LOW CONFIDENCE IN TIMING. MODERATE CONFIDENCE IN PRECIP OCCURRING. WEAK RIDGE WILL FOLLOW BEHIND THE SYSTEM BEFORE NEXT LOW PRESSURE IMPACT SOUTHERN NEW ENGLAND EITHER THURSDAY OR FRIDAY. EC IS LESS AMPLIFIED AND MORE PROGRESSIVE COMPARED TO THE GFS. STILL PLENTY OF TIME TO WATCH THIS SYSTEM AS WELL. BECAUSE OF THE MODEL DISCREPANCIES HAVE A LOW CONFIDENCE ON TIMING...BUT BOTH DETERMINISTIC AND ENSEMBLE GUIDANCE POINT TOWARDS WET WEATHER THURSDAY INTO FRIDAY. LASTLY TEMPS MAY TURN MORE SPRING-LIKE BY THURS/FRIDAY AHEAD OF NEXT SYSTEM. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...TODAY THROUGH SUNDAY THIS AFTERNOON... MVFR CIGS AND IFR VSBYS IN SNOW MOST AREAS EXCEPT RAIN AND SNOW CAPE COD AND ISLAND. LOCAL IFR CIGS. TONIGHT... MIXED MVFR/IFR CIGS AND VSBYS CONTINUE BEFORE MIDNIGHT WITH AREAS OF SNOW IN THE EAST. TREND SHIFTS TO VFR AFTER MIDNIGHT ESPECIALLY IN THE WEST. SUNDAY...VFR. IFR MAY LINGER NEAR THE CAPE AND ISLANDS IN THE MORNING BUT WITH THE TREND TO VFR BY AFTERNOON. KBOS TAF...MODERATE CONFIDENCE IN TAF. KBDL TAF...MODERATE CONFIDENCE IN TAF. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...HIGH CONFIDENCE. SUNDAY NIGHT...LINGERING MVFR ACROSS THE CAPE AND ISLANDS. VFR EVERYWHERE ELSE. MONDAY...VFR DROPPING TO POSSIBLE MVFR IN SCT RAIN SHOWERS AS WEAK COLD FRONT MOVES THROUGH. GUSTY WESTERLY WINDS BEHIND THE FRONT NEAR 20-25 KTS. TUESDAY INTO WEDNESDAY...VFR FOR MOST OF THE PERIOD. MAY SEE MVFR SOUTH OF PIKE IN QUICK MOVING RAIN/SNOW SHOWERS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...THIS AFTERNOON THROUGH SUNDAY MODERATE CONFIDENCE THIS AFTERNOON AND TONIGHT. HIGH CONFIDENCE SUNDAY. NORTH WINDS AS LOW PRESSURE PASSES WELL OFFSHORE...FREQUENTLY GUSTING TO 25 KNOTS ON MOST MA WATERS AND ON RI SOUND. GUSTS TO 30 KNOTS POSSIBLE ON THE OUTER WATERS EAST OF MA. SEAS WILL BE 5-8 FEET ON ALL EXPOSED WATERS AND 1 TO 4 FEET ON THE REMAINING WATERS. WINDS ON THE NEARSHORE WATERS DIMINISH THIS EVENING WHILE WINDS FARTHER OFFSHORE MAY TAKE UNTIL LATE TONIGHT TO FALL BELOW 25 KNOTS. UNDER THESE CONDITIONS WE EXPECT SEAS TO REMAIN AT THEIR DAYTIME LEVELS. HIGH PRESSURE BUILDS OVER THE WATERS SUNDAY. WINDS AND SEAS SHOULD DIMINISH AT THAT TIME. LINGERING 5 FOOT SEAS ON THE OUTER WATERS DURING THE AFTERNOON. SMALL CRAFT ADVISORIES HAVE BEEN EXPANDED TO ALL WATERS EXCEPT NARRAGANSETT BAY...AND EXTENDED INTO SUNDAY FOR MOST WATERS. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... MODERATE CONFIDENCE INTO WEDNESDAY. SUNDAY THROUGH MONDAY...HIGH PRESSURE MOVES OFFSHORE SUNDAY NIGHT AS WINDS BACK TO SW. APPROACHING COLD FRONT ON MONDAY WILL INCREASE SEAS IN RESPONSE. THIS WILL ALLOW FOR SCA TO CONTINUE THROUGH THE PERIOD. TUESDAY...WEAK LULL IN BETWEEN SYSTEMS HOWEVER WINDS WILL BE GUSTY ON THE BACKSIDE OF THE FRONT REACHING NEAR 30KTS. THIS WILL KEEP SEAS UP ABOVE SCA. TUESDAY NIGHT INTO WEDNESDAY...QUICK MOVING SYSTEM WILL MOVE OVER SOUTHERN WATERS. THIS WILL KEEP BOTH SEAS AND WINDS ABOVE SCA ON TUESDAY NIGHT. HIGH PRESSURE WILL FOLLOW ON WED ALLOWING FOR SEAS AND WINDS TO RELAX. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ232>234. SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ230. SMALL CRAFT ADVISORY UNTIL 3 PM EDT SUNDAY FOR ANZ231-235-237- 251. SMALL CRAFT ADVISORY UNTIL 10 PM EDT SUNDAY FOR ANZ250-254>256. && $$ SYNOPSIS...WTB/DUNTEN/GAF NEAR TERM...GAF SHORT TERM...WTB/GAF LONG TERM...DUNTEN AVIATION...WTB/DUNTEN/GAF MARINE...WTB/DUNTEN/GAF

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