478
FXUS61 KBOX 271936
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
236 PM EST SAT DEC 27 2025
WHAT HAS CHANGED
CONFIDENCE IN A PERIOD OF FREEZING RAIN CONTINUES TO INCREASE FOR
SUNDAY NIGHT INTO EARLY MONDAY MORNING, ESPECIALLY NORTHWEST OF THE
I-95 CORRIDOR. GREATEST IMPACTS FROM ICE ACCRETION COMBINED WITH
SNOW COVERED TREES, WILL BE IN THE CT RIVER VALLEY OF WESTERN MA AND
THE MERRIMACK RIVER VALLEY OF NORTHEAST MA. FREEZING RAIN WILL
TRANSITION TO A LIGHT TO MODERATE RAIN LATE SUNDAY NIGHT INTO MONDAY
MORNING. CONFIDENCE CONTINUES TO INCREASE IN THE POTENTIAL FOR
STRONG GUSTY WINDS ON TUESDAY. WIND ADVISORIES MAY BE NEEDED FOR
AT LEAST THE HIGH TERRAIN AND CAPE/ISLANDS.
KEY MESSAGES
- PATCHY BLACK ICE POSSIBLE TONIGHT, OTHERWISE DRY BUT COLD THROUGH
SUNDAY, WITH LOWS IN THE SINGLE DIGITS AND TEENS TONIGHT.
- PERIOD OF FREEZING RAIN SUNDAY NIGHT, BEFORE TRANSITIONING TO
RAIN LATE SUNDAY NIGHT INTO MONDAY MORNING. BEST CHANCE FOR
ICE ACCUMULATION GREATER THAN A TRACE IS ACROSS WESTERN MA IN
THE CT RIVER VALLEY AND IN THE MERRIMACK RIVER VALLEY OF
NORTHEAST MA.
- STRONG GUSTY WINDS AND COLD TUESDAY WITH A FEW SNOW SHOWERS OR
FLURRIES POSSIBLE.
- BELOW NORMAL TEMPERATURES CONTINUE THROUGH LATE WEEK. PERIODS
OF LIGHT SNOW POSSIBLE LATE WEEK.
DISCUSSION
KEY MESSAGE 1...PATCHY BLACK ICE POSSIBLE TONIGHT, OTHERWISE DRY BUT
COLD THROUGH SUNDAY.
FRESH SNOWPACK OF MAINLY 3-6", WITH UP TO 8" ACROSS CT, COMBINED
WITH HIGH PRESSURE ADVECTING INTO SNE WILL YIELD IDEAL RADIATIONAL
COOLING CONDITIONS. GIVEN THIS, WE WILL FOLLOW THE COLDER GUIDANCE,
SUPPORTING MOST LOCATIONS WITH LOW TEMPS IN THE SINGLE DIGITS AND
TEENS TONIGHT. ALSO, ANY RESIDUAL MOISTURE/MELTING FROM THE DAYLIGHT
HOURS, WILL LIKELY REFREEZE TONIGHT, ESPECIALLY ON UNTREATED
SURFACES YIELDING BLACK ICE. THUS, EXERCISE CAUTION IF OUT TONIGHT.
A TRANQUIL WINTER DAY SUNDAY, WITH LIGHT WINDS AND SUNSHINE THRU
INCREASING MID/HIGH CLOUDS, BUT COLD WITH HIGHS IN 30S.
KEY MESSAGE 2...PERIOD OF FREEZING RAIN SUNDAY NIGHT, BEFORE
TRANSITIONING TO RAIN LATE SUNDAY NIGHT INTO MONDAY MORNING.
BEST CHANCE FOR ICE ACCUMULATION GREATER THAN A TRACE IS ACROSS
WESTERN MA IN THE CT RIVER VALLEY AND IN THE MERRIMACK RIVER
VALLEY OF NORTHEAST MA.
RAPIDLY INTENSIFYING LOW (SUB 980 MB) ENTERS THE GREAT LAKES SUNDAY
NIGHT, WITH ITS ATTENDING WARM FRONT INTO NEW ENGLAND. SHALLOW COLD
AIR CURRENTLY OVER SNE, COMBINED WITH STRONG WAA AND A PRONOUNCED
MID LEVEL WARM NOSE OF +9C AROUND 850 MB, WILL YIELD A PTYPE OF FZRA
FOR MOST OF SNE SUNDAY NIGHT. MODEL SOUNDINGS INDICATE FREEZING RAIN
WILL BE EXTREMELY BRIEF SOUTHEAST OF I-95, WITH MAINLY A PLAIN RAIN
EVENT. HOWEVER, NORTHWEST OF I-95, SOUNDINGS INDICATE SHALLOW COLD
AIR WILL TAKE SOMETIME TO ERODE/DISLODGE, WHICH MAKES SENSE GIVEN
THE FRESH 3-6" SNOWCOVER. GIVEN THIS, WE INCORPORATED SOME OF THE
COLDER GUIDANCE INTO THE FORECAST, SPECIFICALLY, THE NBM 10
PERCENTILE TEMPS.
12Z MODEL GUIDANCE MAY NOT HAVE CAPTURED THIS FRESH SNOWCOVER FROM
LAST NIGHT. THEREFORE, LATER MODEL RUNS MAY TREND COLDER WITH THE
CURRENT SHALLOW COLD AIRMASS OVER SNE. THUS, ADVISORIES MAY HAVE TO
BE EXPANDED SOUTHEAST INTO BOSTON, SOUTHEAST MA AND THE PVD AREA.
FOR NOW, WE ISSUED A WINTER WEATHER ADVISORY ALONG AND NORTHWEST OF
I-95 SUNDAY NIGHT, GIVEN THIS IS THE AREA OF GREATEST CONFIDENCE.
GREATEST IMPACTS WILL LIKELY BE ACROSS WESTERN MA IN THE CT RIVER
VALLEY AND THE MERRIMACK RIVER VALLEY OF NORTHEAST MA, WHERE
DURATION OF FREEZING RAIN WILL BE LONGEST. FLAT ICE ACCRETION OF UP
TO TWO TENTHS IS POSSIBLE IN THIS AREA. THIS COMBINED WITH 3-6" OF
SNOW COVER ON TREES WILL YIELD POTENTIAL POWER OUTAGES IN THIS
REGION. THE 12Z HREF RUN FREEZING RAIN ACCUMULATION MODEL (FRAM), A
FAR MORE RELIABLE METHOD THAN STANDARD MODEL ICE ACCRETION,
GENERATES 0.25 TO 0.50 INCH ACCRETION IN WESTERN MA NORTHEAST INTO
THE MERRIMACK RIVER VALLEY. THUS, THIS IS OUR GREATEST AREA OF
CONCERN FOR IMPACTS SUNDAY NIGHT INTO VERY EARLY MONDAY MORNING.
RAIN TAPERS OFF TO DRIZZLE MONDAY MORNING AS DRY SLOT RACES
EASTWARD. CHANCE OF SHOWERS WITH THE COLD FRONT IN THE AFTERNOON.
TEMPS RISE ABOVE FREEZING MONDAY MORNING WITH THE PASSAGE OF THE
WARM FRONT AND INTO THE 40S TO NEAR 50 IN THE AFTERNOON. THEREFORE,
THREAT OF ICING ENDS AFTER 09Z MONDAY MOST LOCALS, AFTER 12Z
NORTHWEST OF I495.
KEY MESSAGE 3...STRONG GUSTY WINDS AND COLD TUESDAY WITH A FEW SNOW
SHOWERS OR FLURRIES POSSIBLE.
A FAIRLY STRONG MID-LEVEL TROUGH SHIFTS AND COLD FRONT SHIFT ACROSS
SOUTHERN NEW ENGLAND EARLY TUESDAY. STRONG CAA PAIRED WITH A
MODERATE LLJ JET RAISES THE CONCERN FOR EFFICIENT MIXING OF GUSTY
WINDS DOWN TO THE SURFACE. LATEST GUIDANCE HASN'T CHANGED MUCH STILL
SHOWING SMALL DIFFERENCES IN THE STRENGTH OF THE LLJ. MOST GLOBAL
GUIDANCE SHOWS 30-40 KTS WHILE GFS REMAINS A BIT MORE ROBUST AT 40-
50 KTS. MODEL SOUNDINGS ARE SUPPORTIVE OF THE HIGHER GUST POTENTIAL
SHOWING A DECENT MIXING DEPTH FROM AROUND 850 MB. THE MAX GUSTS WILL
COME DOWN TO HOW STRONG THE JET ENDS UP BEING. ENSEMBLES HAVE A
RANGE OF 35-50 MPH GUSTS WITH THE HIGHER GUSTS OVER THE HIGHER
TERRAIN AND NEAR THE CAPE/ISLANDS. NBM PROBABILITIES HAVE BEEN
CONSISTENTLY IN THE 60-80% RANGE FOR GUSTS GREATER THAN 45 MPH
(ADVISORY CRITERIA) FOR THE HIGH TERRAIN (BERKSHIRES, WORCESTER
HILLS) AND NEAR THE CAPE/ISLANDS. THE NBM ALSO DISPLAYS LOW
PROBABILITIES (< 35%) FOR MAX GUSTS GREATER THAN 55 MPH CONFINED TO
THE BERKSHIRES/IMMEDIATE EAST SLOPE OF BERKSHIRES. THIS SEEMS
REASONABLE GIVEN THE WESTERLY COMPONENT FLOW MAY SUPPORT DOWNSLOPE
ENHANCEMENT. WIND ADVISORIES ARE LOOKING MORE LIKELY FOR THE HIGH
TERRAIN/CAPE & ISLANDS, BUT WE'LL NEED A BIT MORE CONFIDENCE FOR
OTHER AREAS IN FUTURE GUIDANCE. FOR TIMING, WINDS INCREASE EARLY
TUESDAY MORNING, WITH THE HIGHEST GUSTS LATE AM THROUGH EARLY
EVENING.
TEMPERATURES WILL ALSO BE BELOW NORMAL TUESDAY AND WITH THE ADDED
WIND GUSTS WOULD SUGGEST WIND CHILLS IN THE SINGLE DIGITS TO TEENS
DURING THE DAY.
MID-LEVEL MOISTURE WILL BE PRESENT ON TUESDAY WITH STEEP LAPSE
RATES/MARGINAL INSTABILITY. COMBINED WITH ENHANCED WESTERLY FLOW,
THIS SHOULD BE ENOUGH TO BRING A STREAMER/SHOWERS FROM THE
GREAT LAKES INTO WESTERN MA. ISOLATED SNOW SHOWERS OR FLURRIES
ARE ALSO POSSIBLE FOR SOUTHERN NEW ENGLAND WITHIN THE COLD
ADVECTIVE REGIME.
KEY MESSAGE 4...BELOW NORMAL TEMPERATURES CONTINUE THROUGH LATE
WEEK. PERIODS OF LIGHT SNOW POSSIBLE LATE WEEK.
THERE IS GOOD AGREEMENT AMONG ENSEMBLE GUIDANCE FOR CONTINUED MID-
LEVEL TROUGHING ACROSS THE NORTHEAST THROUGH LATE WEEK. ACCOMPANIED
BY COLD TEMPERATURES ALOFT, THIS WILL SUPPORT BELOW NORMAL
TEMPERATURES IN THE 20S TO LOW 30S. THERE IS A SIGNAL FOR ANOTHER
SHOT OF COLDER AIR FOR THURSDAY AND ESPECIALLY FRIDAY WITH HIGH
POTENTIALLY STRUGGLING TO HIT 30 FRIDAY. THERE MAY BE A FEW SYSTEMS
THAT MOVE THROUGH THE FLOW LATER IN THE WEEK; HOWEVER, CONFIDENCE IS
LOW FOR PRECIPITATION CHANCES/TIMING. THIS MAY BRING A PERIOD OR TWO
OF LIGHT SNOW FALL LATE WEDNESDAY THROUGH FRIDAY.
AVIATION /19Z SATURDAY THROUGH THURSDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
TODAY: MODERATE CONFIDENCE
SNOW IS WRAPPING UP AND SHOULD BE OFFSHORE BETWEEN 13-15Z THIS
MORNING. CIGS AROUND THE REGION ARE ALREADY IMPROVING TO VFR
WITH THE EXCEPTION OF COASTAL TERMINALS WHERE MVFR CIGS WILL
LINGER INTO THE AFTERNOON. THERE MAY BE SOME GUSTY NNW WINDS
THIS MORNING THAT COULD BLOW SNOW AROUND, BUT WINDS THIS
AFTERNOON BECOME LIGHT AT 5-10 KNOTS.
TONIGHT: HIGH CONFIDENCE
VFR. LIGHT NW WINDS UNDER 5 KNOTS.
SUNDAY: HIGH CONFIDENCE
VFR. LIGHT WSW WINDS AT 5-10 KNOTS
KBOS TERMINAL...MODERATE CONFIDENCE
LIGHT SNOW COULD LINGER UNTIL ABOUT 13Z WITH MVFR CIGS LINGERING
UNTIL 17Z. OTHERWISE VFR WITH NNW WINDS AROUND 10 KNOTS FOR THE
AFTERNOON
KBDL TERMINAL...HIGH CONFIDENCE
VFR. LIGHT NNW WINDS AT 5-10 KNOTS.
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...
MONDAY: MAINLY IFR, WITH AREAS MVFR POSSIBLE. BREEZY. RA, FZRA,
PATCHY FG.
MONDAY NIGHT: VFR. WINDY WITH GUSTS UP TO 35 KT. CHANCE RA,
SLIGHT CHANCE FZRA.
TUESDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. STRONG WINDS
WITH LOCAL GUSTS UP TO 40 KT.
TUESDAY NIGHT: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. WINDY WITH
GUSTS UP TO 35 KT.
WEDNESDAY: VFR. BREEZY.
WEDNESDAY NIGHT: VFR. BREEZY. SLIGHT CHANCE SN.
NEW YEARS DAY: VFR. BREEZY. CHANCE SN.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THROUGH MONDAY:
N-NE WINDS UP TO 20 KT ACROSS THE EASTERN MA WATERS YIELDING SCA
SEAS UP TO 7 FT. WE WILL CONTINUE THE SCA HEADLINE THIS EVENING AND
OVERNIGHT. OTHERWISE, HIGH PRESSURE ADVECTS FROM WEST TO EAST ACROSS
SNE TONIGHT AND SUNDAY, YIELDING TRANQUIL MARINE CONDITIONS BY LATE
DEC STANDARDS. POWERFUL LOW PRESSURE (SUB 980 MB) ENTERS THE GREAT
LAKES SUNDAY NIGHT INTO MON, YIELDING SW WINDS UP TO 25 KT. STRONGER
WINDS ALOFT, BUT PROBABLY OF GALES HOLDS OFF UNTIL LATE MONDAY
NIGHT/EARLY TUESDAY.
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...
MONDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS
UP TO 30 KT. AREAS OF ROUGH SEAS. RAIN, PATCHY FOG. AREAS OF
VISIBILITY 1 TO 3 NM.
MONDAY NIGHT: STRONG WINDS WITH GUSTS UP TO 40 KT. ROUGH SEAS
UP TO 17 FT. CHANCE OF RAIN.
TUESDAY: GALE FORCE WINDS WITH LOCAL GUSTS UP TO 45 KT. ROUGH
SEAS UP TO 17 FT. SLIGHT CHANCE OF SNOW.
TUESDAY NIGHT: STRONG WINDS WITH GUSTS UP TO 40 KT. ROUGH SEAS
UP TO 15 FT. CHANCE OF FREEZING SPRAY.
WEDNESDAY: STRONG WINDS WITH GUSTS UP TO 30 KT. AREAS OF ROUGH
SEAS.
WEDNESDAY NIGHT: STRONG WINDS WITH GUSTS UP TO 35 KT. AREAS OF
ROUGH SEAS. SLIGHT CHANCE OF SNOW.
NEW YEARS DAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. LOCAL ROUGH SEAS. CHANCE OF SNOW, CHANCE OF
RAIN.
BOX WATCHES/WARNINGS/ADVISORIES
CT...WINTER WEATHER ADVISORY FROM 7 PM SUNDAY TO 6 AM EST MONDAY
FOR CTZ002>004.
MA...WINTER WEATHER ADVISORY FROM 7 PM SUNDAY TO 6 AM EST MONDAY
FOR MAZ002>006-008>014-026.
RI...WINTER WEATHER ADVISORY FROM 7 PM SUNDAY TO 6 AM EST MONDAY
FOR RIZ001.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ250-
256.
SMALL CRAFT ADVISORY UNTIL 1 AM EST SUNDAY FOR ANZ254-255.
DISCUSSION...MENSCH/NOCERA
AVIATION...MENSCH/NOCERA
MARINE...MENSCH/NOCERA
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