201
FXUS61 KBOX 222017
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
417 PM EDT SAT MAR 22 2025
SYNOPSIS
INCREASING CLOUDS EARLY TONIGHT AHEAD OF A MAINLY DRY COLD
FRONTAL PASSAGE. A COOLER, BLUSTERY AND VERY DRY DAY IS THEN
EXPECTED FOR SUNDAY. ANOTHER FRONTAL SYSTEM THEN BRINGS A SNOW
TO RAIN MIX TO SOUTHERN NEW ENGLAND, TAKING THE LONGEST TO
CHANGE OVER TO RAIN IN THE INTERIOR. A MINOR, SLUSHY
ACCUMULATION OF SNOW IS EXPECTED IN THE INTERIOR, WITH ANY SNOW
BEING WASHED AWAY BY RAIN EARLY MONDAY IN THE COASTAL PLAIN.
DRYING OUT FOR TUESDAY, BUT THERE IS POTENTIAL FOR ANOTHER ROUND
OF SHOWERS MID- WEEK AS A SYSTEM TRACKS TO THE SOUTHEAST OF NEW
ENGLAND.
NEAR TERM /THROUGH SUNDAY/
400 PM UPDATE:
KEY MESSAGES:
* MAINLY DRY FRONTAL PASSAGE BRINGS A COLDER AIRMASS AND BLUSTERY
NORTHWEST WINDS.
* FULL SUNSHINE BUT WINDY AND VERY DRY SUNDAY. HIGHS SOME 10-15
DEGREES COLDER THAN TODAY IN THE 40S.
DETAILS:
PLEASANT AFTERNOON CURRENTLY UNDERWAY ACROSS SOUTHERN NEW ENGLAND,
WITH MOSTLY FULL SUN AND SOUTHWESTERLY GUSTS AROUND 25 TO 30 MPH AND
CURRENT TEMPS IN THE 50S TO LOW 60S, WITH LOW 50S OVER THE
CAPE/ISLANDS WITH THE SWLY MARINE FLOW OFF THE COOLER WATERS OFF
CAPE COD. HOWEVER CLOUD COVER WAS INCREASING OVER EASTERN NY AHEAD
OF A COLD FRONT WHICH WILL CROSS THROUGH SOUTHERN NEW ENGLAND DURING
THE AFTER-SUNSET TO MID EVENING PERIOD - ABOUT 7 TO 10 PM FROM WEST
TO EAST. EXPECT AN INCREASE IN CLOUD COVER EARLY TONIGHT, AND WHILE
CURRENT COMPOSITE RADAR MOSAIC PRESENTATION MAY LEAD YOU TO THINK
OTHERWISE, THE VERY DRY AIR WHICH IS NOT EXPECTED TO RECOVER MAY
LEAD TO A HIT-OR-MISS SHOWER ASSOCIATED WITH FRONTAL PASSAGE, BUT
THE MAJORITY OF THE TIME SHOULD BE DRY, SO NO NEED TO CANCEL ANY
OUTDOOR PLANS TONIGHT. AND REALLY, THE BIGGER STORY ACTUALLY LIES
BEHIND THE FRONT...THAT BEING THE HORIZONAL ADVECTION OF A
NOTICEABLY COOLER AIRMASS INTO SOUTHERN NEW ENGLAND, ALONG WITH
INCREASINGLY BLUSTERY NORTHWEST WIND CONDITIONS. SKIES SHOULD ALSO
CLEAR OUT QUICKLY AFTER FRONTAL PASSAGE - WHEN COMBINED WITH THE
COLD ADVECTION, THAT SHOULD ALLOW FOR TEMPS TO FALL FAIRLY QUICKLY,
AND WHILE THE INCREASED BREEZINESS WILL ADD A CHILL, THESE BREEZES
ADD A LEVEL OF UNCERTAINTY ON HOW LOW AIR TEMPS COULD FALL GIVEN
WINDS AT NIGHT IN A MIXED ATMOSPHERE LENDS ITSELF TO WARMER
NIGHTTIME TEMPS THAN IN A CALM-WIND SITUATION. OPTED FOR WIDESPREAD
20S TO NEAR FREEZING LOW TEMPS FOR TONIGHT, ALTHOUGH THE CITIES
COULD HAVE A BETTER CHANCE AT STAYING NEAR OR JUST ABOVE THE
FREEZING MARK.
FOR SUNDAY...A BUILDING 1020+ MB RIDGE OF HIGH PRESSURE OVER NY/PA
WITH THE DEPARTING COLD FRONT INTO THE MARITIMES WILL CREATE A
PRETTY TIGHT NWLY PRESSURE GRADIENT, WHICH TENDS TO RELAX LATER IN
THE DAY. WE'LL ALSO SEE A MUCH COLDER AIRMASS (E.G. 925 MB TEMPS
RUNNING AROUND -7 TO -9C!) AND FULL SUN UNDER DEEP BLUE SKIES WILL
YIELD AN EXTREMELY WELL-MIXED ATMOSPHERE PRONE TO PRODUCING NWLY
GUSTS AROUND 25-30 MPH ALONG WITH EXCEEDINGLY DRY AIR. NOT OUT OF
THE REALM OF POSSIBILITY THAT WE COULD SEE DEWPOINTS DROP TO SUB-
ZERO LEVELS IN THE INTERIOR, WITH RHS AROUND 20 PERCENT. SO, IT IS A
VERY DRY DAY BUT ALSO QUITE A BIT COOLER THAN TODAY AND WITH NWLY
GUSTS AROUND 25-30 MPH, BUT WINDS SHOULD EASE RATHER QUICKLY LATE IN
THE DAY. GOOD IDEA TO HAVE LIP BALM OR CHAPSTICK ON HAND IF YOU HAVE
OUTDOOR PLANS. DESPITE THE COOLER AIRMASS, KEPT HIGHS IN THE UPPER
30S TO MID/UPPER 40S SINCE WE SHOULD SEE AN ADIABATIC WARMING BOOST
FROM NWLY DOWNSLOPED WINDS.
SHORT TERM /SUNDAY NIGHT THROUGH MONDAY/
400 PM UPDATE:
KEY MESSAGES:
* WARM FRONTAL PASSAGE OVERNIGHT INTO MONDAY AFTERNOON TO BRING A
LIGHT SNOW TO RAIN EVENT TO SOUTHERN NEW ENGLAND.
* WINTRY ACCUMULATIONS GREATEST IN INTERIOR SOUTHERN NEW ENGLAND (UP
TO 2" OF SNOW AND SLEET) AND COULD CAUSE DIFFICULT TRAVEL MONDAY
MORNING BUT EXPECTED TO BE SUB-ADVISORY LEVELS. SLUSHY SNOW
COATINGS EASTWARD INTO THE COASTAL PLAIN. OVERNIGHT TO EARLY
MONDAY TO BE WASHED AWAY BY PREDOMINANTLY RAIN BY MONDAY MORNING.
* RATHER DAMP/RAW MONDAY WITH HIGHS UPPER 30S TO MID/UPPER 40S.
DETAILS:
WE GET A BRIEF PERIOD OF HIGH PRESSURE AND AT LEAST AN EARLY PERIOD
RATHER STRONG RADIATIONAL COOLING FOR SUN NIGHT. HOWEVER THAT
BECOMES REPLACED BY INCREASING CLOUDINESS WITH AN EAST TO
SOUTHEAST BREEZE. THIS OCCURS IN RESPONSE TO AN APPROACHING WARM
FRONT ASSOCIATED WITH A FILLING 995 MB CYCLONE OVER THE
NORTHERN GT LAKES REGION. PRECIPITATION ASSOCIATED WITH THIS
WARM FRONT STARTS TO MOVE IN AROUND MIDNIGHT TO EARLY OVERNIGHT
MONDAY MORNING IN INTERIOR SOUTHERN NEW ENGLAND, THEN SPREAD
EAST INTO THE PRE-DAWN TO EARLY MONDAY HOURS. TEMPS ESPECIALLY
GIVEN THE INITIALLY DRY AIRMASS PRONE TO EVAPORATIVE/WET-BULB
COOLING EFFECTS, SEEM LIKELY TO BRING A PERIOD OF WET SNOW AT
ONSET TO MOST OF SOUTHERN NEW ENGLAND. BUT MILDER MARINE AIR
ON SE FLOW SHOULD FACILITATE AN CHANGEOVER FROM SNOW TO RAIN
EARLY MONDAY ALONG THE COASTAL PLAIN AND INTO CT, WITH A LONGER
DURATION OF FROZEN PRECIP BEFORE THE CHANGEOVER IN INTERIOR
PORTIONS OF SOUTHERN NEW ENGLAND.
BIGGEST UNCERTAINTY WITH THE FORECAST WHEN IT COMES TO PRECIP TYPES,
CHANGEOVERS AND AMOUNTS IS TIED TO THE THERMAL PROFILE AND MORE
SPECIFICALLY WHAT SURFACE TEMPS WILL BE WHEN PRECIP BEGINS
DURING THE OVERNIGHT. THE MODIFYING VERY DRY AIRMASS AND
INCREASED FRONTAL FORCING SHOULD ALLOW FOR TEMPS TO FALL THROUGH
WETBULBING REGARDLESS OF WHEN THE PRECIP COMES IN; IF THAT
PRECIP ARRIVES TOWARD MONDAY MORNING AND ALLOWS FOR A LONGER
PERIOD OF NIGHTTIME COOLING BEFORE IT, A LARGER PORTION OF
SOUTHERN NEW ENGLAND WOULD SEE AT LEAST SOME WINTRY WEATHER AT
ONSET UNTIL TEMPS CAN WARM ABOVE FREEZING. WET SNOW SHOULD START
IN MOST LOCATIONS, WITH THE TRANSITION OVER TO A PLAIN RAIN
MONDAY MORNING TO NOONTIME FROM THE COASTAL PLAIN TO I- 95.
VERTICAL THERMAL PROFILE FROM THE MASS PIKE NORTHWARD ON MONDAY
SHOWS A MODEST WARM NOSE BETWEEN 900-825 MB THEN REFREEZING INTO
ICE PELLETS GIVEN SHALLOW COLD AIRMASS BENEATH THE WARM NOSE.
SURFACE TEMPERATURE-DEPENDENT SNOW OR RAIN IN INTERIOR SOUTHERN
NEW ENGLAND MAY END UP BECOMING MIXED WITH ICE PELLETS/SLEET FOR
A TIME MONDAY MORNING BEFORE COLUMN GRADUALLY WARMS IN FAVOR OF
PLAIN RAIN.
PRECIP COMES TO AN END LATER MONDAY, AND MOST OF THE QPF WITH THE
SYSTEM IS ALONG THE COASTAL PLAIN AND INTO CT, FALLING LARGELY
AS RAIN. COMBINED SNOW AND SLEET ACCUMULATIONS WILL FALL SHORT
OF ADVISORY THRESHOLDS, BUT THE COMBO OF UP TO 2" OF SNOW/SLEET
IN INTERIOR SOUTHERN NEW ENGLAND (FROM A HFD-ORH-LWM LINE NORTH
AND WEST) COULD MAKE FOR SOME DIFFICULT TRAVEL DURING THE MONDAY
AM COMMUTE. FURTHER EAST AND SOUTH INTO THE BOSTON-PROVIDENCE
I-95 CORRIDOR, SLUSHY COATINGS OF SNOW ARE EXPECTED AND SHOULD
NOT YIELD ANY ADVERSE IMPACTS.
EVEN AFTER PRECIPITATION WINDS DOWN MONDAY, SIGNIFICANT WARMING
IS NOT EXPECTED. OVERALL MONDAY IS LOOKING TO BE A RATHER RAW
DAY WITH OVERCAST AND STEADY PRECIP. I SIDED HIGHS ON MONDAY
TOWARD THE COLDER END OF GUIDANCE, FROM THE UPPER 30S TO LOW 40S
NORTH OF THE MASS PIKE, AND INTO THE MID TO UPPER 40S FOR CT-
RT-EASTERN AND SOUTHEAST MA.
LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
KEY MESSAGES:
* SYSTEM BRINGS RAIN MONDAY, WITH A BRIEF PERIOD OF WET SNOW
POSSIBLE MONDAY MORNING ACROSS THE INTERIOR (MAINLY HIGHER
ELEVATIONS).
* POTENTIAL FOR SYSTEM TO BRING A ROUND OF SHOWERS WEDNESDAY.
* TROUGH POSITIONS OVER NORTHEAST THURS/FRI WITH TEMPERATURES NEAR
TO SLIGHTLY BELOW NORMAL.
* POTENTIAL FOR RIDGING AND ABOVE-AVERAGE TEMPERATURES BY NEXT
WEEKEND
TUESDAY AND WEDNESDAY:
CONDITIONS TREND DRIER TUESDAY BEHIND MONDAY'S SYSTEM WITH HIGHS IN
THE 40S AND LOW 50S. LINGERING UPPER LEVEL LOW ALOFT PAIRED WITH
DECENT SURFACE WARMING MAY RESULT IN FAIRLY STEEP LAPSE RATES
TUESDAY. MOISTURE WILL LIKELY BE IN SHORT SUPPLY SO ANY SHOWER
ACTIVITY WILL BE ISOLATED AND LIGHT IN NATURE. TUESDAY WILL ALSO
FEATURE A WEAK COLD FRONT THAT WILL BRING LITTLE CHANGE BEYOND
PUSHING WEDNESDAY'S HIGH TEMPERATURES DOWN A FEW DEGREES.
ENSEMBLE GUIDANCE SHOWS ANOTHER SHORTWAVE TROUGH MOVING ACROSS MID-
WEEK THAT COULD BRING SOME PRECIPITATION TO SOUTHERN NEW ENGLAND. IN
TERMS OF EVENTUAL IMPACTS, IT'S CURRENTLY THE GEPS VERSUS MOST
OTHER ENSEMBLES. THE EPS AND GEFS ADVERTISE A WEAK WAVE THAT PASSES
WELL TO THE SOUTH OF THE REGION WITH MINIMAL IMPACTS. THE GEPS ON
THE OTHER HAND SIGNALS A MORE AMPLIFIED SYSTEM WITH SIMILAR IMPACTS
TO WHAT WILL LIKELY PLAY OUT ON MONDAY. OVERALL TRENDS HAVE SHOWN
THE MAIN LOW TRACKING SOUTHEAST OF SOUTHERN NEW ENGLAND WHICH WOULD
BRING A HIGHER CHANCE FOR PRECIPITATION FOR RI AND SE MA AND
ISOLATED-SCATTERED SHOWERS ELSEWHERE.
THURSDAY THROUGH SATURDAY:
THE AMPLIFIED PATTERN MAINTAINS TROUGHING OVER THE NORTHEAST THROUGH
FRIDAY WITH WEAK EMBEDDED SHORTWAVES. THIS LIKELY TRANSLATES TO
CHANCES FOR SHOWERS LATER THURSDAY AND FRIDAY. TEMPERATURES STAY
AROUND TO JUST BELOW NORMAL IN THE UPPER 40S TO LOW 50S. A DEEPENING
TROUGH OVER THE WESTERN CONUS COULD HELP AMPLIFY A RIDGE IN TIME FOR
SATURDAY. INCREASING HEIGHTS WOULD LIKELY BRING A WARMING TREND IN
TEMPERATURES FOR THE FIRST HALF OF THE WEEKEND.
AVIATION /20Z SATURDAY THROUGH THURSDAY/
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
18Z TAF UPDATE:
THIS AFTERNOON THROUGH TONIGHT: HIGH CONFIDENCE.
VFR THROUGH THE PERIOD, ALTHOUGH A COLD FRONT'S WEST TO EAST
PASSAGE THROUGH SOUTHERN NEW ENGLAND ~22Z SAT-01Z SUN WILL
BRING A BRIEF PERIOD OF LOWER-VFR CLOUD DECKS AND A LOW (<30%)
CHANCE AT AN UNRESTRICTED SHOWER. CLEARING THEREAFTER WILL THEN
BRING A WINDSHIFT FROM INITIAL SW WINDS 10-15 KT GUSTS 20-25 KT
TO NWLY AROUND 13-17KT WITH GUSTS 23-28 KT.
SUNDAY: HIGH CONFIDENCE.
VFR. GUSTY NW WINDS (SPEEDS 14-18 KT/GUSTS 25-30 KT), ALTHOUGH
WINDS AND GUSTS EASE AFTER 20Z.
SUNDAY NIGHT: HIGH CONFIDENCE IN TRENDS, BUT MODERATE CONFIDENCE
IN TIMING.
VFR WITH LIGHT WINDS BECOMING E/ESE INITIALLY. ALTHOUGH IT
SHOULD BE DRY THRU 12Z MON ALBEIT WITH LOWERING CIGS IN EASTERN
NEW ENGLAND, WARM FRONTAL PRECIP SHIELD BRING MVFR/IFR CEILINGS
AND 2-5 SM VISBYS BEGINS TO MOVE INTO INTERIOR WESTERN NEW
ENGLAND AS SOON AS 06Z MON BUT MORE LIKELY AFTER 09Z MON. PRECIP
LIKELY COLD ENOUGH FOR SNOW/ICE PELLET MIX FOR INTERIOR
AIRPORTS WITH MINOR ACCUM (C-1") OF SNOW/SLEET BY DAYBREAK FOR
BAF/BDL. SE WINDS AROUND 5-10 KT, AND THERE COULD BE AREAS OF
LOW LEVEL WIND SHEAR ESPECIALLY SOUTH COASTAL NEW ENGLAND
KBOS TAF...HIGH CONFIDENCE IN TAF. VFR. SW WINDS TO SHIFT TO
WNW AROUND 23-00Z WITH 25-KT GUSTS UPON PASSAGE OF COLD FRONT.
NW WINDS GUSTING TO AROUND 30 KT ON SUN.
KBDL TAF...HIGH CONFIDENCE IN TAF.
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...
MONDAY NIGHT: VFR. BREEZY. SLIGHT CHANCE RA.
TUESDAY: VFR. BREEZY.
TUESDAY NIGHT: VFR. SLIGHT CHANCE SN.
WEDNESDAY: VFR. CHANCE RA.
WEDNESDAY NIGHT: VFR.
THURSDAY: VFR. BREEZY.
MARINE
FORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
400 PM UPDATE:
ADDED THE SOUTHERN NEW ENGLAND NEARSHORE WATERS INTO SMALL CRAFT
ADVISORIES BASED ON OBSERVED SOUTHWEST GUSTS IN THE 25 KT RANGE
ALONG THE COASTLINE. THUS ALL AREAS ARE NOW IN SCAS AND THESE
WILL CONTINUE INTO MUCH OF SUNDAY. A BREAK IN SCA CONDITIONS FOR
SUNDAY NIGHT, BUT ANOTHER SCA COULD BE WARRANTED FOR MONDAY.
SW WINDS AROUND 25-30 KT THIS AFTERNOON INTO EARLY TONIGHT TO
SHIFT TO NW WITH SIMILAR GUST SPEEDS OVERNIGHT INTO SUNDAY ON
ALL WATERS. GUSTS COULD OCCASIONALLY FLIRT WITH GALE FORCE
LEVELS ON THE FAR NORTHEAST WATERS SUNDAY MORNING BUT FELT THE
PREVALANCE OF 35+ KT GUSTS SHOULD BE ISOLATED ENOUGH TO NOT
WARRANT UPGRADES TO GALES. NW GUSTS SHOULD THEN SUBSIDE INTO
SUNDAY AND ESPECIALLY SUNDAY NIGHT. SEAS BUILDING TO 4-7 FT
TONIGHT INTO SUNDAY, THEN SLOWLY RECEDING TO 3-5 FT INTO SUNDAY
AFTERNOON.
FOR MONDAY...EXPECT SOUTHEAST TO SOUTH WINDS INCREASING TO
AROUND 20-25 KT WITH SEAS RISING TO 4-6 FT. STEADY RAINS ARE
EXPECTED ON ALL WATERS MONDAY, WHICH COULD REDUCE VISIBILITY TO
AROUND 2 MILES.
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...
MONDAY NIGHT: WINDS LESS THAN 25 KT. LOCAL ROUGH SEAS. CHANCE
OF RAIN.
TUESDAY: WINDS LESS THAN 25 KT. LOCAL ROUGH SEAS.
TUESDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT. SLIGHT CHANCE OF RAIN.
WEDNESDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT. CHANCE OF RAIN.
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS
APPROACHING 5 FT. SLIGHT CHANCE OF RAIN.
THURSDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 PM EDT SUNDAY FOR ANZ230>237-251.
SMALL CRAFT ADVISORY UNTIL 8 PM EDT SUNDAY FOR ANZ250-254>256.
SYNOPSIS...LOCONTO/FT
NEAR TERM...LOCONTO
SHORT TERM...LOCONTO
LONG TERM...FT
AVIATION...LOCONTO/FT
MARINE...LOCONTO/FT
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