371
FXUS61 KBOX 132335
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
635 PM EST SAT DEC 13 2025
SYNOPSIS
A FAST-MOVING LOW PRESSURE WILL BRING ACCUMULATING SNOW
OVERNIGHT INTO SUNDAY MORNING, ESPECIALLY SOUTH OF THE MASS
PIKE. OCEAN EFFECT SNOW SHOWERS WILL LINGER INTO SUNDAY
AFTERNOON TOWARDS THE CAPE AND ISLANDS. A BRIEF SHOT OF ARCTIC
AIR FOLLOWS SUNDAY NIGHT INTO MONDAY, WITH WIND CHILL VALUES
DROPPING TO BETWEEN 0 TO 10 BELOW ZERO. IT REMAINS COLD TUESDAY,
BUT A PATTERN CHANGE WITH A SIGNIFICANT WARMING TREND IS LIKELY
WEDNESDAY INTO THURSDAY. THE MILDER CONDITIONS WILL LIKELY BE
ACCOMPANIED BY A PERIOD OF GUSTY WINDS AND SHOWERS SOMETIME IN
THE LATE THURSDAY INTO FRIDAY TIME FRAME.
NEAR TERM /THROUGH SUNDAY/
KEY MESSAGES...
* ACCUMULATING SNOW VERY LATE TONIGHT-SUN MORNING, ESPECIALLY
SOUTH OF I-90. HIGHEST ACCUMULATIONS NEAR THE SOUTH COAST.
* ADVISORY LEVEL SNOWFALL EXPECTED ACROSS MUCH OF SOUTHEAST MA
AND SOUTHERN RI.
THE LATEST GUIDANCE SUITE CONTINUED TO NARROW THE FOCUS ON SOME
OF THE CRITICAL DETAILS FOR THIS PORTION OF THE FORECAST. THAT
SAID, SOME UNCERTAINTY REMAINS. FOR EXAMPLE, AT WHAT TEMPERATURE
DOES THE SNOW START ACCUMULATING ON UNTREATED PAVED SURFACES?
EVEN A 1F DEGREE CHANGE COULD EXPAND THE ACCUMULATING SNOW
WINDOW BY A FEW HOURS. THAT COULD MAKE A BIG DIFFERENCE IN
IMPACTS ACROSS OUR REGION.
THE MAIN CONCERN IS WITH THE MAJORITY OF THE SNOWFALL OCCURRING
AT NIGHT, ACCUMULATIONS ARE A LITTLE MORE LIKELY TO OCCUR THAN
AT THE SAME TEMPERATURE DURING THE DAYTIME. SOME OF THE HIGHER
RESOLUTION GUIDANCE WITH HIS LAST SUITE EXHIBITED A NOTABLE
UPTICK IN BANDING WITHIN THE DENDRITIC GROWTH ZONE. HAVE SOME
CONFIDENCE THE HEAVIEST SNOWFALL WILL BE TOWARDS THE SOUTH COAST
OF MA AND RI, BUT STILL DO NOT KNOW WITH CERTAINTY EXACTLY WHERE
THE HEAVIEST BAND WILL FINALLY SET UP.
BASED ON THIS SUBTLE SHIFT FARTHER NORTH AND SLIGHTLY BETTER
DYNAMICS, THE WINTER WEATHER ADVISORY WAS EXPANDED INTO NORTHERN
BRISTOL AS WELL AS EASTERN AND NORTHERN PLYMOUTH COUNTIES IN MA.
STILL KEPT THE GOAL POSTS WIDE WITH RESPECT TO THE TIMING.
THINKING THAT MOST AREAS AWAY FROM THE CAPE AND ISLANDS WILL
LIKELY BE ABLE TO HAVE THE ADVISORY CANCELLED EARLIER THAN THE
7 PM TIMING.
STEADIEST SNOW WILL QUICKLY END FROM WEST TO EAST THROUGH MID
MORNING SUNDAY. EXPECTING OCEAN EFFECT SNOW SHOWERS TO LINGER
ACROSS THE OUTER CAPE SUNDAY AFTERNOON AND NIGHT AS ARCTIC AIR
POURS INTO OUR REGION ON NNW-NW FLOW. OCEAN INDUCED CAPE VALUES
EXPECTED TO INCREASE TO 500-600 J/KG. AN ADDITIONAL 1-2" IS
POSSIBLE ON THE OUTER CAPE, BUT BOUNDARY LAYER TEMPERATURE
PROFILES MAY BE A BIT WARM FOR ADDITIONAL ACCUMULATIONS DURING
THE AFTERNOON.
SHORT TERM /SUNDAY NIGHT/
KEY MESSAGES...
* VERY COLD WITH WIND CHILL VALUES NEAR OR BELOW ZERO
THE COLDEST AIRMASS OF THE SEASON THUS FAR WILL MOVE IN BEHIND
THE SNOW FOR MONDAY NIGHT AS 850MB TEMPS CRASH INTO THE -15C TO
-20C RANGE. THIS WILL RESULT IN OVERNIGHT LOW TEMPERATURES
BOTTOMING OUT IN THE SINGLE DIGITS ACROSS THE INTERIOR, TO THE
LOW TEENS NEAR THE COASTAL PLAIN. A STRONG PRESSURE GRADIENT
WILL RESULT IN GUSTY WINDS OVERNIGHT, AROUND 20-30MPH. THIS WILL
BRING THE WINDCHILL INDEX/FEELS-LIKE TEMPERATURES DOWN TO THE
0F TO -5F RANGE, WITH -5F TO -15F IN THE HIGH TERRAIN. COLD
WEATHER ADVISORIES MAY BE NEEDED IN THE NORTHERN BERKSHIRES FOR
MONDAY MORNING.
LONG TERM /MONDAY THROUGH SATURDAY/
KEY MESSAGES...
* REMAINING COLD MONDAY AND TUESDAY. LIGHT SNOW SHOWERS ARE
POSSIBLE MONDAY NIGHT
* RAPID WARMING TREND WEDNESDAY THROUGH FRIDAY
* LATE WEEK SYSTEM LOOKS TO BRING RAIN AND GUSTY WINDS TO THE
REGION.
THE ARCTIC AIR MASS REMAINS IN PLACE THROUGH TUESDAY AS GFS AND
EURO ENSEMBLES KEEP TEMPERATURE ANOMALIES NEAR 10 DEGREES COLDER
THAN NORMAL. WHILE IT WONT BE AS COLD AS MONDAY MORNING, HIGH
TEMPS WILL REMAIN IN THE 20S FOR MONDAY, AND STRUGGLE TO TOP
FREEZING ON TUESDAY. TUESDAY MORNING LOWS DROP INTO THE TEENS
ACROSS THE REGION, BUT WITH CALM WINDS, THE WIND CHILL INDEX
ALSO REMAINS IN THE TEENS. A WEAK SHORTWAVE PASSES THROUGH THE
REGION MONDAY NIGHT AND COULD BRING SOME LIGHT SNOW SHOWERS TO
THE REGION. WITH A LACK OF STRONG FORCING AND MARGINAL MOISTURE,
QPF WILL BE LIGHT, ON THE ORDER OF A TRACE TO 0.05 INCHES. ANY
SNOW THAT FALLS WILL ALSO BE LIGHT, UNDER A HALF INCH.
AN UPPER-LEVEL RIDGE ORIGINATING FROM MILDER MARITIME AIR OVER
THE PACIFIC OCEAN WILL REACH THE REGION BY WEDNESDAY, WITH
850 MB TEMPS RISING TO +2C. SURFACE HIGH TEMPS ON WEDNESDAY
JUMP INTO THE LOW TO MID 40S, WITH UPPER 40S TO LOW 50S POSSIBLE
FOR THURSDAY AND FRIDAY. GUIDANCE HAS BEEN RELATIVELY CONSISTENT
IN SHOWING A STRONG SHORTWAVE TROUGH DROPPING OUT OF THE GREAT
LAKES ON FRIDAY. TEMPS BY FRIDAY WILL BE WARM ENOUGH TO KEEP
PRECIPITATION AS ALL RAIN. GIVEN THE STRONG WAA, THERE COULD BE
SOME GUSTY WINDS ASSOCIATED WITH THIS SYSTEM ON FRIDAY, BUT IT
IS FAR TOO EARLY TO SPECULATE ON POTENTIAL WIND IMPACTS AT THIS
TIME.
AVIATION /00Z SUNDAY THROUGH THURSDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
TONIGHT...HIGH CONFIDENCE.
VFR CONDITIONS DOMINATE DURING THE FIRST HALF OF THIS EVENING.
MVFR-IFR CONDITIONS IN LIGHT SNOW ARRIVES IN THE 14/03Z TO 14/07Z
TIME FRAME. EXPECTING MAINLY SNOW, BUT A FEW HOURS OF RAIN OR
MIXED RAIN/SNOW ARE POSSIBLE NEAR THE CAPE AND ISLANDS.
STEADIEST SNOW SOUTH OF I-90, AND ESPECIALLY TOWARDS THE SOUTH
COAST WHERE BRIEF LIFR CONDITIONS ARE POSSIBLE IN SNOW.
SUNDAY... MODERATE CONFIDENCE
SNOW EXPECTED TO LINGER A FEW HOURS LONGER THAN THE LAST UPDATE.
EXPECTING SNOW TO END BETWEEN 15/16Z AND 16/18Z FROM NORTHWEST
TO SOUTHEAST, BUT LINGERS TO AROUND 21Z TOWARDS THE SOUTHEAST
NEW ENGLAND COAST. OTHERWISE, IMPROVEMENT TO VFR CONDITIONS
EXPECTED. LIGHT SW WINDS TONIGHT SHIFT TO THE NW AT 5 TO 10 KT
SUNDAY. COULD BECOME GUSTY TOWARDS THE SUNDAY EVENING PUSH.
SUNDAY NIGHT...HIGH CONFIDENCE.
VFR OUTSIDE THE THE OUTER-CAPE/NANTUCKET WHERE OCEAN EFFECT SNOW
SHOWERS MAY PERSIST SUNDAY EVENING. THIS ACTIVITY SHOULD
DISSIPATE THOUGH AFTER MIDNIGHT. OTHERWISE, NW WIND GUSTS OF 20
TO 25 KNOTS WITH A FEW GUSTS NEAR 30 KNOTS ACROSS THE HIGH
TERRAIN AND NEAR THE COAST DEVELOP SUNDAY NIGHT.
KBOS TERMINAL...HIGH CONFIDENCE IN TRENDS. MODERATE CONFIDENCE
IN TIMING. SNOW LIKELY DEVELOPS AFTER 06Z, WITH THE BULK OF IT
ENDING BEFORE LUNCHTIME SUNDAY. TOTAL SNOW ACCUMULATIONS OF 1-2"
POSSIBLE.
KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. SNOW DEVELOPS AFTER
14/03Z AND ENDS BY MID-LATE SUNDAY MORNING. TOTAL SNOW
ACCUMULATIONS OF 1-3" POSSIBLE.
OUTLOOK /MONDAY THROUGH THURSDAY/...
MONDAY: VFR. BREEZY.
MONDAY NIGHT: VFR. BREEZY. SLIGHT CHANCE SN.
TUESDAY: VFR.
TUESDAY NIGHT: VFR. BREEZY.
WEDNESDAY: VFR. WINDY WITH LOCAL GUSTS UP TO 30 KT.
WEDNESDAY NIGHT: VFR. BREEZY.
THURSDAY: VFR. BREEZY. SLIGHT CHANCE RA.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THROUGH SUNDAY NIGHT...HIGH CONFIDENCE.
GUSTY SW WINDS INTO THIS EVENING AHEAD OF AN APPROACHING COLD
FRONT. WIDESPREAD RAIN/SNOW MOVES ACROSS THE WATERS LATE TONIGHT
AND SUNDAY MORNING. GALE WATCH SUNDAY NIGHT INTO MONDAY AS
COLDER AIR MOVING OVER THE WATERS WILL RESULT IN EXCELLENT
MIXING CONDITIONS. AREAS OF VERY LIGHT FREEZING SPRAY LIKELY
SUNDAY NIGHT.
OUTLOOK /MONDAY THROUGH THURSDAY/...
MONDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS
UP TO 30 KT. AREAS OF ROUGH SEAS. AREAS OF FREEZING SPRAY
LIKELY.
MONDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. LOCAL ROUGH SEAS. SLIGHT CHANCE OF SNOW.
TUESDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
TUESDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 30 KT. SEAS LOCALLY APPROACHING 5 FT.
WEDNESDAY: STRONG WINDS WITH GUSTS UP TO 30 KT. AREAS OF ROUGH
SEAS.
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. LOCAL ROUGH SEAS.
THURSDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 7 PM EST
SUNDAY FOR MAZ017>024.
RI...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 7 PM EST
SUNDAY FOR RIZ003>008.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST SUNDAY FOR ANZ231>235-237-
250-251-254>256.
GALE WATCH FROM SUNDAY EVENING THROUGH MONDAY AFTERNOON FOR
ANZ231>235-237-250-251-254>256.
SYNOPSIS...BELK/KP
NEAR TERM...BELK
SHORT TERM...KP
LONG TERM...KP
AVIATION...KP/FT
MARINE...BELK/KP
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