Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 272010 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 310 PM EST FRI FEB 27 2015 .SYNOPSIS... HIGH PRESSURE SLOWLY BUILDING IN FROM THE WEST WILL BRING DRY BUT UNSEASONABLY COLD WEATHER INTO SUNDAY MORNING. A LOW PRESSURE SYSTEM WILL BRING A PERIOD OF SNOW LATE SUNDAY INTO MONDAY. ANOTHER STORM IS LIKELY TUESDAY INTO WEDNESDAY...WITH PRECIPITATION TYPES UNCERTAIN. && .NEAR TERM /THROUGH TONIGHT/...
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315 PM UPDATE...TEMPERATURES HAVE CLIMBED UP INTO THE MID TO UPPER 20S SOUTH OF THE MASS PIKE THIS AFTERNOON. THIS IS A BIT ABOVE WHAT WAS FORECAST SO HAVE UPDATED THE TEMPERATURES TO BETTER REFLECT CURRENT TRENDS. OTHERWISE...MOSTLY SUNNY SKIES AND QUIET WEATHER CONTINUE. TONIGHT...HIGH PRESSURE CONTINUES TO BUILD IN PROVIDING EXCELLENT RADIATIONAL COOLING CONDITIONS ACROSS SOUTHERN NEW ENGLAND. LOW TEMPERATURES WERE A BLEND OF THE NAM AND GFS 2 METER TEMPS... RESULTING IN LOWS BETWEEN 5 AND 15 BELOW ZERO IN THE WESTERN LOCATIONS AND 0 TO 10 DEGREES ACROSS THE EASTERN ZONES.
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&& .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... SATURDAY AND SATURDAY NIGHT...HIGH PRESSURE REMAINS IN CONTROL OF THE REGION. DESPITE A FRIGID START TO THE DAY...TEMPERATURES WILL REBOUND INTO THE MID TO UPPER 20S SATURDAY AFTERNOON. LIGHT WINDS AND THE HIGHER SUN ANGLE WILL AID IN IT FEELING A BIT MORE TOLERABLE DESPITE TEMPS REMAINING WELL BELOW NORMAL. ANOTHER COLD NIGHT IS EXPECTED SATURDAY NIGHT WITH EXCELLENT RADIATIONAL COOLING. && .LONG TERM /SUNDAY THROUGH FRIDAY/... * HIGH PRESSURE SATURDAY NIGHT INTO SUNDAY * COLD FRONT BRINGS SNOW SUNDAY NIGHT INTO MONDAY * ANOTHER STORM POSSIBLE TUESDAY...PTYPE LESS CERTAIN OVERVIEW AND MODEL PREFERENCES... NOTING LITTLE CHANGE IN THE OVERALL PATTERN THROUGH THE LONG TERM WITH NAO/AO REMAINING PRIMARILY NEGATIVE. THE BIGGEST CHANCE IS IN THE PNA WHICH LOOKS TO TREND NEGATIVE UNDER A NEGATIVE EPO. THEREFORE..THIS IS SLIGHTLY DIFFERENT THAN THE OVERALL PATTERN ACROSS NOAM DURING THE SNOW BLITZ PERIOD. AT ODDS PRIMARILY IS A SPLIT FLOW REGIME AND THEIR MERGER /OR LACK THEREOF/ ACROSS THE ERN HALF OF THE CONUS. THE FIRST WAVE TO WATCH ARRIVES VIA THE NRN STREAM SUN NIGHT INTO MON...MANIFESTING AS LOW PRES THROUGH SRN CANADA AND A COLD FRONTAL PASSAGE ACROSS NEW ENGLAND. THE SECOND MAY BE A RESULT OF PHASING OF THESE TWO STREAMS AS WAVES MOVE THROUGH...WHICH IS LIKELY WHY MODELS HAVE BEEN STRUGGLING TO SETTLE ON A SOLUTION FOR THE SFC AND LOW LVL FEATURES. HOWEVER...GIVEN THIS DOES INVOLVE THE SRN STREAM...WILL LIKELY SEE MORE MOISTURE AND HIGHER LATENT HEAT RELEASE RESULTING IN A STRONGER SYSTEM. MODELS ARE TRENDING WARMING IN THE LOW-MID LVLS...HOWEVER WITH A DEEP SNOWPACK IN PLACE AND SOME AGEOSTROPHIC DRAINAGE FLOW POSSIBLE...WILL NEED TO WATCH FOR MIXED P-TYPE ISSUES. IN ANY CASE...A BLEND OF WARMER DETERMINISTIC ECMWF AND GFS WITH THE COOLER MEMBERS FROM BOTH ECENS AND GEFS WILL SHOW THE POTENTIAL RANGE. WILL USE THIS BLEND FOR THE REMAINDER OF THE FORECAST AS WELL. DETAILS... SAT NIGHT INTO SUN... DRY WX PREVAILS AS 1030+ HPA HIGH PRES CRESTS ACROSS THE REGION EARLY SUN. OVERNIGHT MINS ARE LIKELY TO DIP INTO THE SINGLE DIGITS BLOW AND ABOVE ZERO UNDER THE WEAK WINDS AND DEEP SNOWPACK. MODERATING TEMPS UNDER WEAK WARM ADVECTION SUN...BUT HIGHS ARE STILL LIKELY TO BE BELOW NORMAL...MAINLY IN THE 30S. SUN NIGHT INTO MON... LOW PRES WILL PASS THROUGH NRN NEW ENGLAND...ALLOWING A COLD FRONTAL PASSAGE SUN NIGHT INTO MON THROUGH SRN NEW ENGLAND. NOTING MODERATE ISENTROPIC LIFT IN ADVANCE OF THE FRONT...ALONG WITH MID LVL F-GEN ASSOCIATED WITH THE FROPA ITSELF. THESE TWO SOURCES OF LIFT LOOK TO ACT JUST BELOW /BUT ALSO SOMEWHAT WITHIN/ THE PEAK DENDRITE ZONE AND THERMAL PROFILES IN THE LOWER LVLS ARE ALL COLD ENOUGH FOR SNOW. THEREFORE...GIVEN QPF VALUES RANGE FROM ABOUT 0.2 INCHES TO ABOUT 0.5...ADVISORY LEVEL SNOWFALLS ARE LIKELY. IT IS LIKELY THAT ACCUMULATION WILL HAVE BEGUN BEFORE...AND CONTINUE DURING THE MONDAY MORNING COMMUTE. MON NIGHT INTO TUE... ANOTHER BRIEF RIDGE OF HIGH PRES MOVES OVER THE REGION. FAST MOVING EMBEDDED WITHIN CONFLUENT FLOW ALOFT. LOW LVL THERMAL PROFILES SUPPORT TEMPS REMAINING BELOW NORMAL. TUE NIGHT INTO WED NIGHT... AS MENTIONED ABOVE...AND NOTED BY THE PREVIOUS FORECASTER...THERE REMAINS A FAIR AMOUNT OF UNCERTAINTY WITH YET ANOTHER LOW PRES SYSTEM PASSING TO THE NW. WITH THE POTENTIAL FOR PHASING OF THE STREAMS ALOFT...IT IS DIFFICULT TO DETERMINE EXACTLY WHERE THE LOW PRES WILL MOVE OR WHETHER A SECOND LOW WILL FORM. ANY SLIGHT ADJUSTMENT IS LIKELY TO MAKE SIGNIFICANT CHANGES IN THE THERMAL PROFILES...BUT THE RECENT TRENDS SUGGEST MID LVL WARMING WITH H85 TEMPS LIKELY EXCEEDING 0C THROUGHOUT MUCH OF SRN NEW ENGLAND. WITH DEEP SNOWPACK...THIS IS LIKELY TO LEAD TO MIXED PRECIP TYPES AND A POTENTIAL FOR ICING. IT COULD START AS SNOW THOUGH...AS EVEN THE WARMEST OF THE AVAILABLE GUIDANCE BEGINS COLD ENOUGH FOR SNOW AT THE FIRST QPF ONSET. GIVEN THIS DOES SEEM TO HAVE SOME CONNECTION TO THE SRN STREAM...THE INFUSION OF MOISTURE WITH PWATS POTENTIALLY 2-3 STD DEVIATIONS ABOVE NORMAL SUGGESTS THAT WARNING LEVEL SNOW IS NOT OUT OF THE QUESTION FOR AREAS THAT MAINTAIN SNOW LONGER...WITH SOME ICE ACCRETION. WILL NEED TO CONTINUE TO WATCH THIS STORM AS WE APPROACH. HEAVY RAIN NOT OUT OF THE QUESTION EITHER IF A FULL CHANGE OVER IS ALLOWED /THE FURTHER SRN REACHES HAVE THE BEST CHANCE OF THIS/. LATE NEXT WEEK... ONCE AGAIN IT/S DEPENDENT ON WHETHER EACH OF THE STREAMS PHASE. IF THEY DO SO...IT/S POSSIBLE THE LOW PRES/FRONTAL SYSTEM WILL BE RATHER SLOW MOVING AND MAY LINGER INTO THU POTENTIALLY. IN ANY CASE...IT APPEARS ANOTHER INTRUSION OF ARCTIC AIR WILL IMPACT THE REGION TOWARD THE END OF THE WEEK. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TODAY THROUGH SATURDAY AFTERNOON/... THROUGH 00Z...HIGH CONFIDENCE. VFR. A FEW MID AND HIGH CLOUDS TODAY...WITH SOME BKN LOW END VFR CIGS POSSIBLE JUST EAST OF THE CAPE. TONIGHT THROUGH SATURDAY NIGHT...HIGH CONFIDENCE. VFR KBOS TAF...HIGH CONFIDENCE. VFR. KBDL TAF...HIGH CONFIDENCE. VFR. OUTLOOK...SUNDAY THROUGH TUESDAY... SUNDAY...HIGH CONFIDENCE. MAINLY VFR. CIGS SLOWLY DIMINISH DURING THE DAY ON SUN. SUN NIGHT INTO MON NIGHT...MODERATE CONFIDENCE. A COLD FRONTAL PASSAGE WILL BRING ABOUT ACCUMULATING SNOWFALL AT AREA TERMINALS. EXPECTING 2-5 INCHES AT THIS TIME. PERIODS OF IFR/MVFR LIKELY WITH GUSTY NW WINDS ON MON...20-30 KT AT TIMES. TUE...HIGH CONFIDENCE. MAINLY VFR. && .MARINE...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SATURDAY NIGHT/...HIGH CONFIDENCE. HIGH PRESSURE BUILDS OVER THE WATERS FROM THE WEST ALLOWING WINDS AND SEAS TO SUBSIDE GRADUALLY. SEAS REMAIN ABOVE 5 FEET ON THE OUTER WATERS SO AM ALLOWING THE SMALL CRAFT ADVISORY TO CONTINUE ON THOSE WATERS THROUGH TONIGHT. OUTLOOK...SUNDAY THROUGH TUESDAY... SUNDAY...HIGH CONFIDENCE. HIGH PRES OVER THE WATERS. WINDS AND SEAS GENERALLY BELOW SMALL CRAFT ADVISORY CRITERIA. SUN NIGHT INTO MON NIGHT...MODERATE CONFIDENCE. A COLD FRONT CROSSES THE WATERS ON MONDAY. THIS WILL BRING A PERIOD OF SNOW /MIXING WITH RAIN ON THE SOUTH COAST/. EXPECT SOUTHERLY WINDS AND BUILDING SWELL SUN NIGHT INTO EARLY MON...WITH SMALL CRAFT ADVISORY CONDITIONS LIKELY. HOWEVER AFTER THE FRONTAL PASSAGE AND WINDS SHIFTING TO THE W-NW GALE FORCE WINDS POSSIBLE. TUESDAY...MODERATE CONFIDENCE. CONDITIONS IMPROVE BUT SMALL CRAFT ADVISORIES ARE LIKELY TO CONTINUE.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST SATURDAY FOR ANZ250- 254>256. && $$ SYNOPSIS...DOODY/RLG NEAR TERM...RLG SHORT TERM...RLG LONG TERM...DOODY AVIATION...DOODY/RLG MARINE...DOODY/RLG

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