074
FXUS61 KBOX 192020
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
320 PM EST SUN JAN 19 2025
SYNOPSIS
A FAST-MOVING LOW-PRESSURE SYSTEM WILL BRING ACCUMULATING SNOW TO
THE REGION TONIGHT, WITH THE MOST SIGNIFICANT TRAVEL IMPACTS
OCCURRING THIS EVENING BETWEEN 7 PM - 12 AM. AN ARCTIC
AIRMASS WILL BRING FRIGID CONDITIONS WITH MINIMUM WIND CHILLS ON THE
ORDER OF 5 TO 15 BELOW ZERO AT TIMES MONDAY NIGHT THROUGH THURSDAY
MORNING. TEMPERATURES MODERATE A BIT IN THE THURSDAY THROUGH
SATURDAY TIME FRAME, BUT THEY WILL REMAIN BELOW NORMAL. DRY WEATHER
WILL GENERALLY PREVAIL, BUT A BIT OF LIGHT SNOW/FLURRIES MAY CLIP
THE SOUTHEAST NEW ENGLAND COAST LATE TUESDAY NIGHT INTO WEDNESDAY
MORNING.
NEAR TERM /UNTIL 6 AM MONDAY MORNING/
KEY POINTS
*WINTER STORM HEADLINES REMAIN IN EFFECT FOR TONIGHT
*6-8 INCHES, WITH LOCALIZED 10 INCHES NW OF I-95
*3-6 INCHES, WITH HIGHER UNCERTAINTY SE OF I-95
*0-2 INCHES ACROSS THE CAPE AND THE ISLANDS
AN AREA OF LOW PRESSURE STRENGTHENS AS IT MAKES A CLOSE PASS
OFFSHORE, WITH THE CENTER NEAR THE CAPE AND ISLANDS. MODEL GUIDANCE
REMAINED CONSISTENT WITH THIS PATH TODAY. THUS, CONFIDENCE CONTINUES
TO INCREASE FOR WIDESPREAD ACCUMULATING SNOWFALL ACROSS THE REGION
TONIGHT. PRECIPITATION MOVES IN SW TO NE TONIGHT BETWEEN 4 PM - 7
PM, WITH A MIX OF RAIN/SNOW POSSIBLE WITH ONSET DUE TO ABOVE-
FREEZING TEMPERATURES AROUND THE REGION. TEMPERATURES SHOULD DROP
BELOW FREEZING FROM NW TO SE BETWEEN 4 PM AND 8 PM, ALLOWING ANY
RAIN-SNOW MIX TO CHANGE TO SNOW.
THE HEAVIEST SNOW AND BEST POTENTIAL FOR BANDING WILL OCCUR BETWEEN
6 PM TO 1 AM, WHERE 0.5 INCH/HR SNOW RATES ARE LIKELY, WITH A LOW TO
MODERATE CHANCE FOR 1-2 INCH/HR SNOW RATES. THE LATEST 12Z HI-RES
GUIDANCE FAVORS SE OF THE I-95 CORRIDOR FROM BOSTON TO PROVIDENCE
FOR THE HEAVIEST QPF AND SNOW RATES DUE TO THE CLOSE OFFSHORE TRACK
OF THE LOW. HOWEVER, SE MA AND RI IS THE AREA OF HIGHEST
UNCERTAINTY BECAUSE TEMPERATURES WILL TAKE LONGER FOR TEMPS TO DROP
BELOW FREEZING. IF TEMPS STAY ABOVE FREEZING AFTER 7-8PM, THEN SNOW
TOTALS LIKELY REMAIN IN THE 3-6 RANGE, BUT IF THEY DROP QUICKER,
THEN 6-8 INCHES WITH LOCALIZED 10 INCHES WILL BE POSSIBLE. AS FOR
NORTH AND WEST OF I-95, COLDER TEMPS AND HIGHER SNOW-TO-LIQUID
RATIOS WILL MAKE UP FOR LESS QPF. WIDESPREAD OF 6-8 INCHES IS
EXPECTED, WITH LOCALIZED AREAS OF UP TO 10 INCHES POSSIBLE.
AS FOR THE CAPE AND ISLANDS, TEMPS SHOULD STAY ABOVE FREEZING UNTIL
AFTER MIDNIGHT; BY THIS POINT, THE HEAVIEST QPF WILL HAVE MOVED OFF
TO THE NORTHEAST. WE DID BUMP UP SNOW TOTALS WITH THE SLIGHT SHIFT
SOUTH IN THE HI-RES GUIDANCE. EXPECT ANYWHERE FROM 0-2 INCHES, WITH
LOCALIZED 3-4 INCHES IF COLDER TEMPS MOVE IN QUICKER THAN EXPECTED.
WINTER STORM WARNINGS REMAIN IN EFFECT NORTH AND WEST OF THE I-95
CORRIDOR, WITH WINTER WEATHER ADVISORIES SE OF THE I-95 CORRIDOR
EXCEPT FOR THE CAPE AND ISLANDS. SNOW ENDS FROM SW TO NE TONIGHT
BETWEEN 1 AM TO 5 AM, WITH SOME FLURRIES LINGERING UNTIL
SUNRISE. THE MOST SIGNIFICANT TRAVEL IMPACTS WILL OCCUR THIS
EVENING AS THE HEAVIEST SNOW OCCURS BETWEEN 7 PM AND MIDNIGHT.
GUSTY WINDS BEHIND THE SYSTEM COULD BLOW AROUND SNOW, LEADING TO
LIGHT TRAVEL CONCERNS FOR THE MONDAY MORNING COMMUTE.
SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/
KEY POINTS
*ARCTIC AIRMASS BRINGS WIND CHILL VALUES DOWN INTO THE SINGLE
DIGITS ON MONDAY
*DANGEROUSLY COLD MONDAY NIGHT WITH LOWS AROUND 0F
ARCTIC AIRMASS MOVES IN BEHIND SUNDAY NIGHTS SYSTEM WITH 850 MB
TEMPERATURES CRASHING FROM -3C THIS AFTERNOON TO -20C BY MONDAY
EVENING. WITH GUSTY WINDS AROUND 15 TO 25MPH ON MONDAY, THE WIND
CHILL INDEX (FEELS LIKE TEMPERATURE) WILL BE IN THE SINGLE DIGITS TO
LOW TEENS ALL DAY. WINDS BEGIN TO DIE DOWN MONDAY EVENING AND COULD
GO CALM OVERNIGHT AS THE BOUNDARY LAYER DECOUPLES. CLEAR SKIES,
CALM WINDS, AND SUBLIMATING SNOW WILL SET UP FOR STRONG RADIATIONAL
COOLING AND DANGEROUSLY COLD NIGHT. LOWS WILL LIKELY BOTTOM OUT
NEAR 0F, WITH WIND CHILL VALUES IN THE SINGLE DIGITS BELOW ZERO.
LONG TERM /TUESDAY THROUGH SUNDAY/
KEY POINTS
* ARCTIC OUTBREAK MON PM THROUGH THU AM
-MINIMUM WIND CHILLS 5 TO 15 BELOW ZERO AND PERHAPS AS LOW AS20
IN SPOTS
-ACTUAL LOW TEMPERATURES IN THE SINGLE DIGITS, WITH SOME BELOW
ZERO
-ACTUAL HIGHS TUE AND WED MAINLY BETWEEN 15 AND 20
* ANOTHER OFFSHORE LOW PRESSURE MAY IMPACT SOUTHERN NEW ENGLAND THU
NIGHT INTO FRI
ABOVE AVERAGE CONFIDENCE IN THE FORECAST THROUGH THURSDAY. LATEST
GUIDANCE SUITE IN RATHER GOOD SYNOPTIC AGREEMENT WITH THE DEEP MID
LEVEL TROUGH AND SURFACE HIGH PRESSURE. THIS WILL LEAD TO AN ARCTIC
OUTBREAK ACROSS SOUTHERN NEW ENGLAND, WITH THE COLDEST AIR WE HAVE
SEEN SO FAR THIS SEASON. THE PEAK OF THIS COLD LOOKS TO BE
WEDNESDAY, WITH A VERY GRADUAL WARMUP INTO FRIDAY. EVEN THEN,
TEMPERATURES STILL EXPECTED TO REMAIN BELOW NORMAL. NEAR NORMAL
TEMPERATURES POSSIBLE THIS WEEKEND. MUCH WILL DEPEND UPON THE TRACK
OF A LOW PRESSURE LATE THIS WEEK.
WITH THE HIGH PRESSURE IN PLACE, NOT MUCH CHANCE FOR PRECIPITATION
MOST OF THIS WEEK. THE ARCTIC AIR WILL GENERATE SOME OCEAN-EFFECT
SHOWERS WHICH WILL REMAIN PRIMARILY OVER THE COASTAL WATERS. SOME
CHANCE THEY COULD BACK INTO PORTIONS OF THE OUTER CAPE OR NANTUCKET
WITH A SUBTLE WIND SHIFT, BUT THAT IS A VERY LOW PROBABILITY.
THE NEXT LOW PRESSURE WHICH MAY IMPACT OUR REGION LOOKS TO PASS
SOUTHEAST OF THE 40N/70W BENCHMARK TOWARDS THURSDAY NIGHT INTO
FRIDAY. WE WILL LIKELY NEED SEVERAL MORE DAYS TO HAVE A BETTER IDEA
OF THE RISK POSED BY THIS PARTICULAR SYSTEM.
AVIATION /20Z SUNDAY THROUGH FRIDAY/
FORECAST CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
REST OF TODAY AND TONIGHT...MODERATE TO HIGH CONFIDENCE.
VFR INTO THE AFTERNOON, WITH SOME SPOTS ALREADY GOING MVFR IN
CENTRAL MA. PRECIPITATION SPREADS ACROSS REGION FROM THE SW TO
NE BETWEEN 21Z AND 23Z WITH CONDITIONS LOWERING TO MVFR/IFR.
PERIODS OF LIFR POSSIBLE IN ANY HEAVIER SNOW BANDS THAT DEVELOP.
PTYPE WILL MAINLY BE SNOW NW OF I-95 IN MA AND RI, BUT A PERIOD
OF RAIN MAY OCCUR NEAR AND ESPECIALLY SOUTHEAST OF I-95. PTYPE
SHOULD TRANSITION TO MAINLY SNOW NORTHWEST OF THE CAPE COD CANAL
BY 00Z/01Z OR SO. HEAVIER SNOW RATES WILL LIKELY OCCUR 00Z
THROUGH 04Z/05Z WHEN IFR/LIFR CONDITIONS ARE EXPECTED. SNOWFALL
RATES OF 1-2" PER HOUR WILL BE POSSIBLE AT TIMES. MODERATE
CONFIDENCE IN WHERE THESE HIGHER RATES WILL DEVELOP. TOTAL SNOW
ACCUMULATIONS OF 3-6"/4-8" WILL BE COMMON FOR MUCH OF THE
REGION NORTHWEST OF THE CAPE COD CANAL. PTYPE PROBABLY CHANGES
TO ALL SNOW BEFORE ENDING EVEN ACROSS THE CAPE. THE LAST OF THE
STEADY SNOW SHOULD EXIT THE COAST BY 09Z/10Z MON. CONDITIONS
WILL IMPROVE TO VFR BY DAYBREAK MONDAY.
WINDS AT SOME TERMINALS HAVE ALREADY SHIFTED MORE N AND OTHERS
WILL CONTINUE TO DO SO AS THE AFTERNOON PROGRESSES. WINDS
EXPECTED TO SHIFT MORE NW LATER TONIGHT WITH GUSTS OF 20-25 KTS
POSSIBLE. BRIEF GUSTS TO 30 KT POSSIBLE ACROSS THE CAPE AND AT
ORH.
MONDAY...HIGH CONFIDENCE.
TERMINALS EXPECTED TO IMPROVE TO VFR PAST 11Z MONDAY. SOME BRIEF
SPOT SNOW SHOWERS CANNOT BE RULED OUT. NW WIND GUSTS OF 20 TO
30 KNOTS.
KBOS TAF...MODERATE CONFIDENCE IN TAF. HEAVIEST OF THE SNOW
ROUGHLY BETWEEN 00Z AND 05Z. 1" PER HOUR SNOWFALL RATES POSSIBLE
AT TIMES.
KBDL TAF...MODERATE CONFIDENCE IN TAF. HEAVIEST OF THE SNOW
ROUGHLY BETWEEN 22Z AND 03Z. 1" PER HOUR SNOWFALL RATES POSSIBLE
AT TIMES.
OUTLOOK /TUESDAY THROUGH FRIDAY/...
TUESDAY: VFR. BREEZY.
TUESDAY NIGHT THROUGH THURSDAY: VFR.
THURSDAY NIGHT: VFR. SLIGHT CHANCE SN.
FRIDAY: VFR.
MARINE
FORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH- GREATER THAN 60 PERCENT.
HIGH CONFIDENCE...
INCREASING WINDS TONIGHT TO 15-20 KTS WITH GUSTS TO 30 KTS AS A
LOW PRESSURE PASSES FROM SOUTHWEST TO NORTHEAST. GUSTS UP TO 35
KTS POSSIBLE FOR THE NORTHERN OUTER WATERS TONIGHT THROUGH
EARLY MONDAY RESULTING IN A GALE WARNING. OTHERWISE, EXPECT SCAS
GENERALLY THROUGH 12Z TUESDAY. SEAS 4-9 FT.
OUTLOOK /TUESDAY THROUGH FRIDAY/...
TUESDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING 5 FT.
TUESDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT. CHANCE OF SNOW SHOWERS.
WEDNESDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT. SLIGHT CHANCE OF SNOW SHOWERS.
WEDNESDAY NIGHT THROUGH THURSDAY: WINDS LESS THAN 25 KT.
THURSDAY NIGHT: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN,
SLIGHT CHANCE OF SNOW.
FRIDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
SLIGHT CHANCE OF SNOW.
BOX WATCHES/WARNINGS/ADVISORIES
CT...WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR CTZ002>004.
MA...WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR MAZ002>016-026.
WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR MAZ017>021.
RI...WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR RIZ001-002.
WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR RIZ003>007.
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 7 PM EST
MONDAY FOR ANZ230>234-236.
SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 4 AM EST
TUESDAY FOR ANZ235-237.
GALE WARNING FROM 7 PM THIS EVENING TO 7 AM EST MONDAY FOR
ANZ250.
SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 1 AM EST
TUESDAY FOR ANZ251.
SMALL CRAFT ADVISORY UNTIL 3 PM EST TUESDAY FOR ANZ254>256.
SYNOPSIS...BELK/KP
NEAR TERM...KP
SHORT TERM...KP
LONG TERM...BELK
AVIATION...BELK/HRENCECIN/KP
MARINE...BELK/KP
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