102
FXUS61 KBOX 180606
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
106 AM EST SAT JAN 18 2025
SYNOPSIS
AN APPROACHING COLD FRONT WILL RESULT IN A SOUTHERLY FLOW OF
EVEN MILDER AIR FOR SATURDAY WITH A PERIOD OF RAIN SHOWERS
SATURDAY AFTERNOON INTO EARLY EVENING. DRY WEATHER SHOULD
PREVAIL FOR THE FIRST PART OF SUNDAY BEHIND THIS COLD FRONT. A
WAVE OF LOW PRESSURE MOVING IN LATER SUNDAY THROUGH EARLY MONDAY
IS LIKELY TO BRING ACCUMULATING, PLOWABLE SNOWFALL TO SOUTHERN
NEW ENGLAND, THOUGH THE EXACT FORECAST ACCUMULATIONS WILL HINGE
ON THE SYSTEM'S TRACK NEAR OR THROUGH SOUTHERN NEW ENGLAND. THIS
WILL BE FOLLOWED BY AN ARCTIC OUTBREAK LATER MONDAY INTO
WEDNESDAY WITH WIND CHILLS LIKELY DROPPING TO BETWEEN 10 AND 15
BELOW ZERO.
NEAR TERM /UNTIL 6 AM THIS MORNING/
KEY MESSAGES:
* NEAR TO ABOVE NORMAL TEMPERATURES
HIGH PRESSURE MOVES OFF THE MID ATLANTIC COAST TONIGHT, SHIFTING
WINDS TO THE S TO SW ACROSS SOUTHERN NEW ENGLAND. NOT ESPECIALLY
STRONG FOR THIS TIME OF YEAR. INCREASING CLOUDS EXPECTED, WHICH
WILL TEMPER THE IMPACT OF RADIATIONAL COOLING. ANTICIPATING LOW
TEMPERATURES TO BE NEAR TO ABOVE NORMAL.
SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/
KEY MESSAGES:
* ABOVE NORMAL TEMPERATURES WITH BREEZY CONDITIONS SATURDAY.
* RAIN SHOWERS DEVELOPING IN THE AFTERNOON, BECOMING MORE
WIDESPREAD DURING THE EVENING.
A COLD FRONT IS EXPECTED TO CROSS SOUTHERN NEW ENGLAND SATURDAY
NIGHT. SHOWERS BECOMING MORE WIDESPREAD BY EVENING, THEN
TAPERING OFF FROM WEST TO EAST BEHIND THIS FRONT AS IT MOVES
OFFSHORE.
SATURDAY:
A WEAK SHORTWAVE TROUGH AND COLD FRONT APPROACHES THE REGION
SATURDAY. MOISTURE GRADUALLY INCREASES INTO THE AFTERNOON WITH
PRECIPITABLE WATER VALUES AROUND 150-200% OF NORMAL BY EARLY
EVENING. THIS WAVE WILL BRING A BROAD AREA OF ASCENT SUPPORTING
OUR NEXT CHANCE OF PRECIPITATION. SHOWERS BEGIN TO DEVELOP IN
THE AFTERNOON FROM WEST TO EAST, BECOMING MORE WIDESPREAD MID-
AFTERNOON TO EARLY EVENING.
EXPECTING MAINLY RAINFALL FOR THIS EVENT GIVEN THE INCREASING
WARM AIR ADVECTION. THERE IS A SLIGHT RISK FOR SOME FREEZING
RAIN OR LIGHT SNOW AT THE ONSET SATURDAY MORNING ACROSS THE
HIGHER TERRAIN TOWARDS THE BERKSHIRES. AT THIS POINT, THINKING
UP TO AN INCH OF SNOWFALL IS POSSIBLE BEFORE RAIN MIXES IN OR
ALL PRECIPITATION TRANSITIONS TO ALL RAIN.
TEMPERATURE-WISE, THINKING THE SIGNIFICANTLY COLDER AIR STARTS
TO ARRIVE LATE SATURDAY NIGHT. THIS WILL NOT BE ENOUGH TIME TO
BRING LOW TEMPERATURES EVEN TO NEAR NORMAL LEVELS.
LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
KEY MESSAGES:
* PLOWABLE SNOWFALL LIKELY LATE SUN/SUN NIGHT, WITH POTENTIAL FOR
HALF-FOOT OR MORE OF SNOW IN INTERIOR SOUTHERN NEW ENGLAND. WINTER
STORM WATCHES ISSUED FOR SUNDAY INTO EARLY MONDAY FOR NORTHERN
CT AND WESTERN/CENTRAL MA.
* BELOW NORMAL TEMPS AND LOW WIND CHILLS FOR EARLY TO MID NEXT WEEK
ASSOCIATED WITH COLDEST AIRMASS TO THIS POINT IN WINTER. HIGHS MAY
STRUGGLE TO REACH THE MID TEENS IN INTERIOR CT AND MA.
DETAILS:
SUNDAY AND MONDAY:
WE CONTINUE TO MONITOR DEVELOPMENTS REGARDING THE POTENTIAL FOR
ACCUMULATING SNOWFALL CENTERED DURING THE SUNDAY AFTERNOON TO EARLY
MONDAY MORNING TIMEFRAME. THIS IS IN ASSOCIATION WITH A WAVE OF LOW
PRESSURE WHICH MOVES NORTHEAST FROM THE CENTRAL APPALACHIANS/MID-
ATLANTIC REGION.
THERE IS STILL A CONSIDERABLE SPREAD IN POTENTIAL OUTCOMES SPECIFIC
TO THIS SYSTEM, DUE TO A STILL-UNCERTAIN LOW PRESSURE TRACK EITHER
THROUGH SOUTHERN NEW ENGLAND OR OFFSHORE. IN PARTICULAR, AN OFFSHORE
PASS THROUGH SOUTHERN NEW ENGLAND CLOSER TO THE 12Z ECMWF AND MORE
OF ITS ENSEMBLE MEMBERS WOULD FAVOR AN OFFSHORE, COLDER, LESS-LIQUID-
EQUIVALENT QPF SCENARIO AND WOULD LIKELY LEAN TO A WIDESPREAD
ACCUMULATING SNOWFALL, IF OF THE FLUFFIER VARIETY GIVEN THE COLD
TEMPS. ANOTHER POTENTIAL OUTCOME AT PLAY IS A CAMP FAVORED BY THE
GFS, CANADIAN GEM AND THEIR ENSEMBLE MEMBERS, WHICH ARE CLOSER OR
EVEN THROUGH EASTERN PORTIONS OF SOUTHERN NEW ENGLAND SUCH THAT
WARMER AIR ALOFT MAY FAVOR PORTIONS OF THE EASTERN NEW ENGLAND
COASTAL PLAIN TO INITIALLY SEE PLAIN RAIN (OR, RAIN MIXING IN
WITH SNOW) BEFORE THE COLDER AIR FLIPS PRECIPITATION OVER TO
ALL- SNOW; WITH THE STEADIEST AND EVEN POTENTIALLY AREAS OF
BANDED SNOW OCCURS IN INTERIOR SOUTHERN NEW ENGLAND ALONG AND
NORTHWEST OF THE 925-850 MB THERMAL GRADIENT.
BECAUSE OF A CONTINUED UPTICK IN MODEL-FORECAST QPF ACROSS ALL
GLOBAL ENSEMBLES, AND AFTER COORDINATION WITH WPC AND NWS OFFICES,
WE OPTED TO HOIST WINTER STORM WATCHES FOR INTERIOR PORTIONS OF
SOUTHERN NEW ENGLAND (NORTHERN CT, WESTERN/CENTRAL MA) FOR SUNDAY
AFTERNOON INTO EARLY ON MONDAY. FOR THE AREAS IN THE WINTER STORM
WATCH, WE FELT THE POTENTIAL FOR 4-8" WITH LOCALLY EMBEDDED HIGHER
AMTS (ESPECIALLY IF BANDING MATERIALIZES) WAS CONCEIVABLE FOR THOSE
AREAS. DUE TO THE POTENTIAL FOR WARMER AIR CUTTING IN AND REDUCING
ACCUMS FOR EASTERN MA AND RI, WE OPTED FOR AROUND A 2 TO 5 INCH
ACCUMULATION FOR THESE LOCATIONS; A COLDER/MORE OFFSHORE STORM TRACK
CERTAINLY COULD PUSH THOSE TOTALS UPWARD AND POSSIBLY FORCE WINTER
STORM WATCHES EASTWARD IN LATER UPDATES WERE THAT TO BE THE CASE.
BUT IT IS STILL TOO UNCERTAIN TO MAKE THAT DECISION GIVEN THE
CURRENT MODEL-FORECAST SITUATION.
PRECIP STILL LOOKS TO BEGIN SUNDAY AFTERNOON, AND WITH THE PEAK
OCCURRING SUNDAY EVENING INTO EARLY MONDAY, SNOW SHOULD EASILY
ACCUMULATE ON ALL SURFACES WHEN IT DOES DEVELOP. WITH IT BEING A
HOLIDAY WEEKEND, THE ADVERSE IMPACT ON TRAVEL SHOULD BE AT LEAST
ATTENUATED SOME THAN IT WOULD OTHERWISE.
EARLY TO MID NEXT WEEK:
ONE OF THE COLDEST AIRMASSES TO THIS POINT IN THE WINTER SEASON
TAKES HOLD THROUGH AT LEAST MIDWEEK. BELOW NORMAL TEMPS AND WIND
CHILLS IN THE SINGLE DIGITS ABOVE TO SINGLE DIGITS BELOW ZERO ARE
FORECAST, WITH POTENTIAL FOR LOWER WIND CHILLS PENDING WIND SPEEDS.
TUE AND WED LOOK TO BE THE COLDEST DAYS, AND IT IS POSSIBLE THAT
COLD WEATHER ADVISORIES COULD BE NEEDED. DEPENDING ON HOW MUCH SNOW
FALLS SUN NIGHT/MON, LOW TEMPS COULD BE COLDER THAN FORECAST GIVEN A
FRESH SNOWPACK.
LATE-WEEK:
MOSTLY STUCK WITH NBM OUTPUT GIVEN A RATHER BUSY WEEKEND TO MIDWEEK
FORECAST TIMEFRAME. BUT IT APPEARS AS THOUGH WE START TO
GRADUALLY THAW OUT OF THE TRULY DEEP COLD AS WE MOVE INTO LATE
IN THE WEEK. DRIER WEATHER AND TEMPS RETURNING BACK INTO THE
20S.
AVIATION /06Z SATURDAY THROUGH WEDNESDAY/
FORECAST CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
06Z TAF UPDATE:
TONIGHT: HIGH CONFIDENCE.
MAINLY VFR, THOUGH THERE IS A CHANCE AT VFR/MVFR CLOUDINESS NEAR
SOUTHEAST MA, CAPE AND ISLANDS BY DAYBREAK. LIGHT S/SW WINDS.
SATURDAY...HIGH CONFIDENCE IN TRENDS. MODERATE CONFIDENCE IN
TIMING.
VFR CONDITIONS THIS MORNING, GRADUALLY BECOMING MVFR IN THE
AFTERNOON AND EARLY EVENING. LOCALIZED IFR CONDITIONS POSSIBLE
BY EARLY EVENING. RAIN SHOWERS WILL ALSO OVERSPREAD THE REGION
DURING THE AFTERNOON HOURS FROM WEST TO EAST; HOWEVER, FEW
SCATTERED SHOWERS ARE POSSIBLE BEFORE THAT(AFTER 15Z).
SATURDAY NIGHT...HIGH CONFIDENCE IN TRENDS. MODERATE CONFIDENCE IN
TIMING.
MVFR TRENDING TO VFR. AREAS OF IFR COULD LINGER ACROSS RI AND
SOUTHEAST MA UNTIL AFTER MIDNIGHT, BEFORE IMPROVING LATE.
KBOS TAF...HIGH CONFIDENCE IN TAF.
KBDL TAF...HIGH CONFIDENCE IN TAF.
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...
SUNDAY NIGHT: MAINLY IFR, WITH LOCAL MVFR POSSIBLE. BREEZY.
CHANCE SN.
MARTIN LUTHER KING JR DAY: VFR. BREEZY. SLIGHT CHANCE SN.
MONDAY NIGHT THROUGH TUESDAY: VFR. BREEZY.
TUESDAY NIGHT: VFR.
WEDNESDAY: VFR. BREEZY. SLIGHT CHANCE SN.
MARINE
FORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH- GREATER THAN 60 PERCENT.
HIGH CONFIDENCE.
HIGH PRESSURE MOVES ACROSS THE WATERS TONIGHT, KEEPING LIGHT
WINDS AND SEAS. S TO SW WINDS INCREASE SATURDAY AHEAD OF AN
APPROACHING COLD FRONT. BUILDING SEAS ACROSS THE OUTER COASTAL
WATERS. SMALL CRAFT ADVISORIES WILL BE ISSUED FOR THE OUTER
COASTAL WATERS FOR A PERIOD FROM LATE SATURDAY MORNING INTO
SUNDAY MORNING. THIS ADVISORY COULD BE EXTENDED WITH LATER
FORECASTS.
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...
SUNDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. ROUGH SEAS UP TO 9 FT. RAIN, CHANCE OF SNOW.
AREAS OF VISIBILITY 1 TO 3 NM.
MARTIN LUTHER KING JR DAY: MODERATE RISK FOR SMALL CRAFT
ADVISORY WINDS WITH GUSTS UP TO 25 KT. ROUGH SEAS UP TO 9 FT.
CHANCE OF FREEZING SPRAY, SLIGHT CHANCE OF SNOW.
MONDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. AREAS OF ROUGH SEAS. CHANCE OF FREEZING
SPRAY, SLIGHT CHANCE OF SNOW.
TUESDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT.
TUESDAY NIGHT THROUGH WEDNESDAY: WINDS LESS THAN 25 KT. AREAS
OF SEAS APPROACHING 5 FT. SLIGHT CHANCE OF SNOW.
BOX WATCHES/WARNINGS/ADVISORIES
CT...WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY
MORNING FOR CTZ002>004.
MA...WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY
MORNING FOR MAZ002>004-008>012-026.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 7 PM EST THIS
EVENING FOR ANZ230>237-251.
SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 2 AM EST SUNDAY
FOR ANZ250-254>256.
SYNOPSIS...BELK/FRANK
NEAR TERM...BELK/LOCONTO
SHORT TERM...BELK
LONG TERM...LOCONTO
AVIATION...FRANK/MENSCH
MARINE...BELK/LOCONTO
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