860
FXUS61 KBOX 212336
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
636 PM EST SUN DEC 21 2025
WHAT HAS CHANGED
NO SIGNIFICANT CHANGES. MINOR SNOW ACCUMULATIONS STILL EXPECTED
TUESDAY GENERALLY ON THE ORDER OF 1 TO 3 INCHES. LOW CONFIDENCE
TEMPERATURE AND PRECIPITATION FORECAST CONTINUES FRIDAY INTO
NEXT WEEKEND...BUT CONCERN GROWING FOR AN EXTENDED PERIOD OF
SHALLOW COLD AIR OVER THIS TIME.
KEY MESSAGES
- COLD AND GUSTY CONDITIONS TONIGHT INTO MONDAY WITH WIND CHILLS
FALLING TO BETWEEN 0 AND 10 ABOVE BY EARLY MONDAY MORNING.
- MINOR SNOW ACCUMULATIONS OF 1-3" LIKELY TUESDAY.
- A FEW LEFT OVER SNOW SHOWERS POSSIBLE NEAR THE COAST WED,
OTHERWISE DRY/SEASONABLY CHILLY WED INTO THU /CHRISTMAS/.
SEASONABLE HIGH TEMPS MAINLY IN THE 30S TO LOWER 40S.
- LOW CONFIDENCE FORECAST FRI INTO NEXT WEEKEND WITH THE
POTENTIAL FOR SHALLOW COLD AIR ALONG WITH SNOW/ICE AND/OR
RAIN AT TIMES.
DISCUSSION
KEY MESSAGE 1...COLD AND GUSTY CONDITIONS TONIGHT INTO MONDAY
WITH WIND CHILLS FALLING TO BETWEEN 0 AND 10 ABOVE BY EARLY
MONDAY MORNING.
STRONG COLD FRONT ACCOMPANIED BY A SHARP
TEMPERATURE DROP HAS CLEARED THE REGION. WINDS HAVE RAMPED UP
BEHIND IT WITH WIDESPREAD 25-35 MPH GUSTS. EXPECT THESE
CONDITIONS TO PERSIST THROUGH MONDAY BEFORE GRADUALLY
DIMINISHING MONDAY AFTERNOON WITH A WEAKENING PRESSURE GRADIENT.
STILL TRACKING A COLD AIRMASS WITH -12 TO -15C TEMPS AT 850
ADVECTING INTO THE REGION. MAIN IMPACT MONDAY MORNING WILL BE COLD
WIND CHILLS THAT WILL RANGE FROM SINGLE DIGITS IN THE INTERIOR TO
MID TEENS ACROSS THE CAPE/ISLANDS... EXCEPT SLIGHTLY BELOW ZERO IN
THE BERKSHIRES. MONDAY'S TEMPERATURES WILL BE SEVERAL DEGREES BELOW
NORMAL WITH HIGHS IN THE UPPER 20S TO LOWER 30S AND PLENTIFUL
SUNSHINE IN VERY DRY AIRMASS.
KEY MESSAGE 2...MINOR SNOW ACCUMULATIONS OF 1-3" LIKELY TUESDAY
CONFIDENCE IN BOTH TIMING AND TOTALS FOR TUESDAY'S LIGHT SNOW EVENT
HAS INCREASED SINCE THE LAST UPDATE. SYNOPTICALLY THE PICTURE
REMAINS FAIRLY STRAIGHTFORWARD, A SHORTWAVE APPROACHES FROM THE NW
WHILE A WARM FRONT MOVES N FROM THE SW. WARM FRONT WILL BE SLOW TO
PROGRESS N AS NW FLOW ALOFT STRENGTHENS. HAVE SEEN MORE GUIDANCE
COME INTO ALIGNMENT WITH THE IDEA OF A LATER START WITH SNOW
STARTING LATE MORNING/EARLY AFTERNOON ON TUESDAY AND LINGERING
THROUGH TUESDAY NIGHT. GUIDANCE HAS ALSO TRENDED COLDER FOR AREAS SE
OF I-95 AND NOW SHOWS A MOSTLY SNOW EVENT. LOW LEVEL ISOTHERMAL
PROFILE PAIRED WITH LIGHT WAA WILL LIKELY WARM SFC TEMPS ENOUGH FOR
A BRIEF TRANSITION TO RAIN OR A RAIN/SNOW MIX ESPECIALLY ALONG THE
SOUTH COAST AS WELL AS THE CAPE AND ISLANDS. IT IS POSSIBLE SNOW OR
MIXED SNOW/RAIN WILL LINGER INTO TUE EVENING, BUT THIS IS NOT A
SIGNIFICANT QPF EVENT SO EXPECTING MOSTLY LIGHT ACCUMULATIONS ON THE
ORDER OF 1-3 INCHES WITH PERHAPS LOCALIZED 4" AMOUNTS ACROSS THE
INTERIOR HIGH TERRAIN.
KEY MESSAGE 3...A FEW LEFT OVER SNOW SHOWERS POSSIBLE NEAR THE COAST
WED, OTHERWISE DRY/SEASONABLY CHILLY WED INTO THU /CHRISTMAS/.
SEASONABLE HIGH TEMPS MAINLY IN THE 30S TO THE LOWER 40S.
OFFSHORE LOW PRESSURE WITH AN INVERTED TROUGH SETUP MAY RESULT IN A
FEW LINGERING SNOW SHOWERS NEAR THE COAST WED. OTHERWISE...DRY
WEATHER EXPECTED WED INTO THU /CHRISTMAS/. SEASONABLY CHILLY HIGH
TEMPS IN THE 30S TO THE LOWER 40S EXPECTED WITH THU /CHRISTMAS/
BEING THE MILDER OF THE TWO DAYS. INTENSIFYING LOW PRESSURE WELL
OVER THE ATLANTIC COUPLED WITH HIGH PRESSURE ACROSS THE GREAT LAKES
WILL RESULT IN GUSTY NORTHWEST WINDS ON WED. THIS HIGH BUILDS
FURTHER EAST BY THU /CHRISTMAS/...SO LESS WIND THAN WED ALONG WITH
SLIGHTLY MILDER TEMPERATURES.
KEY MESSAGE 4...LOW CONFIDENCE FORECAST FRI INTO NEXT WEEKEND WITH THE
POTENTIAL FOR SHALLOW COLD AIR ALONG WITH SNOW/ICE AND/OR RAIN
AT TIMES.
LOW CONFIDENCE FORECAST CONTINUES FRIDAY INTO NEXT WEEKEND AS A
BOUNDARY WILL BE SEPARATING VERY COLD AIR/BELOW NORMAL TEMPERATURES TO
OUR NORTH AND UNSEASONABLY MILD TEMPERATURES TO OUR SOUTHWEST. THERE
IS A HIGH ACROSS QUEBEC AND PATTERN RECOGNITION WOULD INDICATE GOOD
SUPPORT FOR SHALLOW COLD AIR TO INVADE SOUTHERN NEW ENGLAND. THE 12Z
ECMWF IS MOST AGGRESSIVE WITH THE SHALLOW COLD AIR...ESPECIALLY ON
FRIDAY WITH DAYTIME TEMPERATURES MAINLY IN THE 20S! MEANWHILE...THE
12Z GFS IS THE MILDEST OF THE GUIDANCE WITH TEMPERATURES AT THE SAME
TIME IN THE 50S! THE INTERESTING THING IS THAT THE GFS AI MODEL IS
MUCH COLDER AND MORE SIMILAR TO THE ECMWF. ASSUME IT IS PROBABLY AN
INDICATION OF PAST PERFORMANCE/PATTERN RECOGNITION. WHILE WE ARE NOT
SURE IT WILL BE QUITE AS COLD AS THE ECMWF...WE CERTAINLY WANT TO
LEAN COLDER BASED ON PATTERN RECOGNITION AND SUPPORT FROM THE AI
GUIDANCE. BUT AGAIN...TREMENDOUS UNCERTAINTY CONTINUES IN THIS
FORECAST.
IN FACT...CONFIDENCE IN TEMPERATURES REMAINS QUITE LOW INTO NEXT
WEEKEND AS WELL. HEIGHT FIELDS MAY RISE A BIT AHEAD OF THE NEXT
SHORTWAVE...BUT SHALLOW COLD AIR MAY BE STILL BE HANGING TOUGH.
SO IF THERE IS A WARMUP...IT MAY END UP RATHER BRIEF BEFORE THE
NEXT SURGE OF COLD AIR WORKS INTO THE REGION.
THE OTHER ISSUE WILL BE LOW PRESSURE APPROACHING FROM THE WEST. THIS
WILL BRING THE POTENTIAL FOR SOME RAIN/ICE AND/OR SNOW FRI INTO SAT.
PTYPE WILL DEPEND UPON DEPTH AND AMOUNT OF COLD AIR THAT ENDS UP
WORKING INTO SOUTHERN NEW ENGLAND...WHICH REMAINS UNCERTAIN AT THIS
TIME.
AVIATION /00Z MONDAY THROUGH FRIDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
00Z TAF UPDATE...NO SIGNIFICANT CHANGES.
TODAY THROUGH MONDAY...HIGH CONFIDENCE.
VFR THROUGH THE PERIOD. NW AND GUSTY WINDS FOR THE REST OF
TONIGHT THEN GRADUALLY DIMINISHING MONDAY.
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.
OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/...
TUESDAY: MVFR/IFR CONDITIONS POSSIBLE. SN.
TUESDAY NIGHT: MVFR/IFR CONDITIONS POSSIBLE. BREEZY. CHANCE SN.
WEDNESDAY: VFR. WINDY WITH GUSTS UP TO 35 KT. SLIGHT CHANCE
SHSN.
WEDNESDAY NIGHT: VFR. BREEZY.
CHRISTMAS DAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. BREEZY.
THURSDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. BREEZY.
CHANCE RA, CHANCE FZRA, CHANCE SN, CHANCE PL.
FRIDAY: MAINLY VFR, WITH AREAS IFR POSSIBLE. BREEZY. CHANCE RA,
CHANCE SN, CHANCE PL, CHANCE FZRA.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
GALE WARNINGS FOR THE INNER AND OUTER COASTAL WATERS THROUGH 12Z
MONDAY MORNING. ELSEWHERE, SMALL CRAFT ADVISORIES FOR NARRAGANSETT
BAY AND BOSTON HARBOR. GRADUAL IMPROVEMENTS ON MONDAY AFTERNOON.
WARM FRONT APPROACHES FROM THE SW LATER TUESDAY MORNING WITH SW
WINDS 10-15 KTS WITH GUSTS UP TO 25 KTS.
OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/...
TUESDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
RAIN, SNOW LIKELY. LOCAL VISIBILITY 1 TO 3 NM.
TUESDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 30 KT. LOCAL ROUGH SEAS. CHANCE OF RAIN.
WEDNESDAY: MODERATE RISK FOR GALE FORCE WINDS WITH GUSTS UP TO
40 KT. AREAS OF ROUGH SEAS. CHANCE OF RAIN SHOWERS, CHANCE OF
SNOW SHOWERS.
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. LOCAL ROUGH SEAS.
CHRISTMAS DAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT.
THURSDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS
APPROACHING 5 FT. CHANCE OF RAIN.
FRIDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS
UP TO 25 KT. SEAS UP TO 5 FT. CHANCE OF RAIN.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST MONDAY FOR ANZ230-236.
GALE WARNING UNTIL 7 AM EST MONDAY FOR ANZ231>235-237-250-251-
254>256.
DISCUSSION...FRANK/FT
AVIATION...FRANK/MCMINN
MARINE...FRANK/FT
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page