248
FXUS61 KBOX 210253
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
953 PM EST FRI DEC 20 2024
SYNOPSIS
A COASTAL STORM WILL MOVE OUT TO SEA TONIGHT WITH SNOWFALL
ENDING. MAINLY DRY BUT BLUSTERY AND VERY COLD THIS WEEKEND INTO
EARLY NEXT WEEK. A WEAK CLIPPER SYSTEM MAY BRING LIGHT SNOW
ACCUMULATIONS CHRISTMAS EVE, THEN MAINLY DRY FOR THE REST OF THE
CHRISTMAS WEEK WITH TEMPERATURES MODERATING INTO THE 30S AND
LOW 40S.
NEAR TERM /UNTIL 6 AM SATURDAY MORNING/
945 PM UPDATE...
SOME DRIER AIR IS STARTING TO MOVE INTO THE REGION AND
STEADIER SNOW HAS ERODED ACROSS THE CAPE/ISLANDS. HOWEVER,
STILL GETTING CELLULAR BANDS OF SNOW ACROSS SE MA WITH
OCCASIONAL BURSTS OF MODERATE SNOW WHICH IS ENHANCED ALONG THE
COASTAL FRONT IN SE MA. MAY SEE LOCALLY ANOTHER INCH OR 2,
ESPECIALLY ACROSS PORTIONS OF NORFOLK AND NORTHERN PLYMOUTH
COUNTIES BEFORE THE SNOW TAPERS OFF AROUND MIDNIGHT. GUSTY N-NE
WINDS ALONG THE COAST WILL SLOWLY DIMINISH LATE TONIGHT. THE
WINTER WEATHER ADVISORY FOR SE MA WILL LIKELY BE DISCONTINUED
AROUND OR JUST AFTER MIDNIGHT.
SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/
KEY MESSAGES...
* DRIER AND COLDER ON SATURDAY AND VERY COLD ON SATURDAY NIGHT
SATURDAY THE MID LEVEL TROUGH REMAINS OVERHEAD BUT THE LOW QUICKLY
EXITS EAST. WE'LL SEE BREEZY NW WINDS 10 TO 15 MPH WITH GUSTS AS
HIGH AS 25 MPH. GIVEN THE CYCLONIC FLOW ALOFT WE MAY SEE SOME WIDELY
SCATTERED LIGHT SNOW BUT MOSTLY JUST CONTINUED CLOUDCOVER. IN THE
AFTERNOON HEIGHTS WILL BE STARTING TO RISE AND DRIER AIR ADVECTED IN
ON THAT NW FLOW SO CLOUDS WILL DISSIPATE THROUGH THE AFTERNOON AND
EVENING. THIS WILL BE THE TRANSITION TOWARD OUR COLDEST DAY OF THE
SEASON ON SUNDAY, WITH HIGHS ONLY MAKING IT INTO THE UPPER 20S AND
LOW 30S. THE REAL COLD ARRIVES OVERNIGHT, THOUGH, AS FRIGID AIR
ARRIVES. 850 MB REACH AROUND -15C, WHILE AT THE SURFACE LOWS WILL
DROP INTO THE SINGLE DIGITS (INTERIOR) AND MID TEENS (COAST). BREEZY
WINDS WILL MAKE IT FEEL MORE LIKE SINGLE DIGIT NEGATIVES TO NEAR 0
IN THE INTERIOR.
LONG TERM /SUNDAY THROUGH FRIDAY/
KEY MESSAGES:
* ARCTIC AIRMASS CONTINUES TO BRING HIGHS IN THE 20S AND LOWS IN
THE SINGLE DIGITS SUNDAY INTO MONDAY
* GRADUAL WARM-UP THE REST OF THE WEEK WITH HIGHS IN THE 30S AND
LOWS IN THE 20S
* WEAK CLIPPER SYSTEM MOVES THROUGH CHRISTMAS EVE, BUT CONFIDENCE
IS STILL LOW
1040MB HIGH PRESSURE AND ARCTIC AIRMASS REMAIN OVER THE REGION
THROUGH MONDAY. DESPITE SUNNY SKIES, HIGHS WILL STRUGGLE TO TOP 30F,
WITH MOST OF THE REGION IN THE LOW 20S. WITH BLUSTERY NW WINDS AT 10-
15MPH, THE WIND CHILL FACTOR WILL MAKE IT FEEL LIKE THE SINGLE
DIGITS. OVERNIGHT LOWS WILL LIKELY DROP TO SOME OF THE COLDEST WE
HAVE SEEN THUS FAR FOR THE SEASON, WITH LOWS IN THE SINGLE DIGITS,
POSSIBLY BELOW ZERO IN HIGH TERRAIN IN NW MA. WINDS WILL DECREASE
OVERNIGHT, WHICH WILL HELP PREVENT THE WIND CHILL FACTOR FROM GOING
FAR BELOW ZERO. SURFACE FLOW TURNS SOUTHERLY ON MONDAY, ALLOWING
HIGH TEMPS TO MODERATE SLIGHTLY INTO THE UPPER 20S TO LOW 30S.
A CLIPPER SYSTEM DROPS OUT OF THE NORTHERN GREAT LAKES ON CHRISTMAS
EVE, WHICH COULD BRING ANOTHER ROUND OF LIGHT WINTRY PRECIPITATION.
UNCERTAINTY REMAINS HIGH WITH THIS SYSTEM AS MODELS ARE USUALLY TOO
QUICK TO KICK OUT STRONG HIGH-PRESSURE SYSTEMS. CURRENT ENSEMBLE
GUIDANCE SHOWS HIGH PROBS FOR 1 INCH ACROSS THE REGION, WITH LOW
PROBS FOR 3 INCHES IN THE HIGH TERRAIN OF THE BERKSHIRES.
TEMPERATURES TUESDAY CONTINUE TO MODERATE INTO THE LOW TO MID-30S.
HIGH PRESSURE BUILDS BACK IN FROM THE NORTH FOR CHRISTMAS DAY
THROUGH THE END OF THE WEEK. HIGH TEMPERATURES CONTINUE TO MODERATE
INTO THE MID TO UPPER 30S TO EVEN LOW 40S BY THE END OF THE WEEK.
AVIATION /03Z SATURDAY THROUGH WEDNESDAY/
FORECAST CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
TONIGHT...MODERATE CONFIDENCE.
LIGHT TO MODERATE SNOW CONTINUES EAST OF THE I-95 CORRIDOR
THOUGH ABOUT 04-06Z, EXCEPT OVER THE CAPE AND ISLANDS WHERE
SNOW WILL LAST UNTIL 06-09Z. IFR/LIFR CONDITIONS CAN BE EXPECTED
WITH SNOW FALL, BUT SHOULD LIFT TO MVFR AS SNOW COMES TO AN
END.
WEST OF THE I-95 CORRIDOR, SNOW IS SLOWING DOWN WITH ONLY
LINGERING SNOW SHOWERS AND MVFR CIGS.
CIGS WILL GO VFR FROM WEST TO EAST TONIGHT AS WINDS TURN NW.
WITH GOOD MIXING GUSTS OF 10-20 KNOTS ARE POSSIBLE RIGHT INTO
SATURDAY MORNING.
SATURDAY...MODERATE CONFIDENCE.
MAINLY VFR CIGS, BUT LOWER MVFR CIGS POSSIBLE EARLY
CAPE/ISLANDS. SCATTERED SNOW SHOWERS DEVELOPING WHICH MAY
REDUCE VSBYS AT TIMES, ESPECIALLY INTERIOR. NW WIND 10-20 KT
WITH SOME HIGHER GUSTS.
SATURDAY NIGHT...MODERATE.
VFR. NW WINDS 5-10 KTS GUSTING TO 20 KTS.
KBOS TAF...LOW TO MODERATE CONFIDENCE. CONTINUED LIGHT TO
MODERATE SNOW OFF OF THE OCEAN WILL REDUCE VSBYS AT TIMES BELOW
3 MILES THROUGH THE EVENING. NNE GUSTS TO 20-25 KT.
KBDL TAF...MODERATE CONFIDENCE. CIGS LOWERING TO MVFR WITH
LIGHT TO MODERATE SNOW IN THE AFTERNOON AND EVENING WHICH MAY
REDUCE VSBYS BELOW 1 MILE AT TIMES.
OUTLOOK /SUNDAY THROUGH WEDNESDAY/...
SUNDAY: VFR. BREEZY.
SUNDAY NIGHT THROUGH MONDAY: VFR.
MONDAY NIGHT: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. CHANCE SN.
TUESDAY: MAINLY VFR, WITH AREAS MVFR POSSIBLE. CHANCE SN,
CHANCE RA.
TUESDAY NIGHT: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. CHANCE SN.
CHRISTMAS DAY: VFR. SLIGHT CHANCE RA, SLIGHT CHANCE SN.
MARINE
FORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
KEY MESSAGES:
* SMALL CRAFT ADVISORY IN EFFECT THROUGH SUNDAY.
TONIGHT...MODERATE CONFIDENCE.
SURFACE LOW PRESSURE SYSTEM MOVES UP THE COAST AND REMAINS OUT TO
SEA. INCREASING EAST/NORTHEAST WINDS 15 TO 20 KNOTS WITH GUSTS
UP TO 30 KNOTS ON THE OUTERMOST WATERS, NEARSHORE WATERS GUSTS
ARE CLOSER TO 25 KNOTS. SEAS BUILDING 4 TO 9 FEET FOR THE
WATERS. PERIODS OF RAIN AND SNOW TONIGHT, DIMINISHING EARLY
SATURDAY MORNING.
SATURDAY...HIGH CONFIDENCE.
LOW PRESSURE SYSTEM LIFTS NORTHEAST FROM SOUTHERN NEW ENGLAND, BUT
WITH HIGH PRESSURE BUILDING TO THE WEST, IT WILL LEAD TO NORTHWEST
FLOW WITH GUSTS CONTINUING THROUGHOUT THE DAY. HAVE EXTENDED THE
SMALL CRAFT ADVISORY AS A RESULT THROUGH THE DAY. SEAS REMAIN ROUGH
3 TO 6 FEET ON THE SOUTHERN WATERS AND 5 TO 8 FEET ON THE EASTERN
WATERS.
SATURDAY NIGHT...HIGH CONFIDENCE.
HIGH PRESSURE MOVING OVERHEAD. NW WINDS 15-20 KTS GUSTING TO 25
KTS. SEAS 5-7 FT.
OUTLOOK /SUNDAY THROUGH WEDNESDAY/...
SUNDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. CHANCE OF SNOW.
LOCAL VISIBILITY 1 TO 3 NM.
SUNDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT. CHANCE OF SNOW.
MONDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
SLIGHT CHANCE OF SNOW.
MONDAY NIGHT: WINDS LESS THAN 25 KT. CHANCE OF RAIN, CHANCE OF
SNOW.
TUESDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
RAIN LIKELY. LOCAL VISIBILITY 1 TO 3 NM.
TUESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT. CHANCE OF RAIN, CHANCE OF SNOW.
CHRISTMAS DAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT. CHANCE OF RAIN.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...WINTER WEATHER ADVISORY UNTIL 4 AM EST SATURDAY FOR MAZ013-
015>022.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST SATURDAY FOR ANZ230.
SMALL CRAFT ADVISORY UNTIL 7 AM EST SUNDAY FOR ANZ231-232-251.
SMALL CRAFT ADVISORY UNTIL 7 AM EST SATURDAY FOR ANZ233>235-
237.
SMALL CRAFT ADVISORY UNTIL 7 PM EST SUNDAY FOR ANZ250-256.
GALE WARNING UNTIL 4 AM EST SATURDAY FOR ANZ254-255.
SYNOPSIS...BW/KP
NEAR TERM...KJC
SHORT TERM...BW
LONG TERM...KP
AVIATION...BW/KP
MARINE...BW/KP
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