363
FXUS61 KBOX 150551
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
1251 AM EST SUN DEC 15 2024
SYNOPSIS
STRONG HIGH PRESSURE WILL RESULT IN A DRY BUT COLD WEEKEND. A
SHIFT TO A MORE UNSETTLED WEATHER PATTERN NEXT WEEK WITH PERIODS
OF PRECIPITATION POSSIBLE. TEMPERATURES TREND ABOVE NORMAL
TUESDAY THROUGH THURSDAY. POTENTIAL FOR ANOTHER LATE WEEK
SYSTEM; HOWEVER, CONFIDENCE IS LOW IN THE DETAILS.
NEAR TERM /THROUGH TODAY/
NEAR RECORD HIGH PRESSURE OVER UPSTATE NY WILL MOVE OVER NEW
ENGLAND TONIGHT. RATHER TRANQUIL WEATHER WILL CONTINUE. WITH
LIGHT WINDS AND CLEAR SKIES, EXCEPT ACROSS PORTIONS OF THE OUTER
CAPE AND NANTUCKET, EXPECTING EXCELLENT RADIATIONAL COOLING
CONDITIONS. FAVORED THE LOWEST GUIDANCE FOR LOW TEMPERATURES
OVER LAND. THINKING LOW TEMPERATURES ABOUT 7-10 DEGREES BELOW
NORMAL FOR MID DECEMBER.
SHORT TERM /TONIGHT THROUGH 6 PM MONDAY/
KEY MESSAGES...
* DRY THROUGH SUNDAY WITH BELOW NORMAL TEMPERATURES
* WINTRY MIX LATE SUNDAY NIGHT
MORE OF THE SAME TO START SUNDAY. LARGE HIGH PRESSURE SHIFTS
FARTHER OFFSHORE, BUT STILL REMAINS IN CONTROL. THE FORECAST FOR
LATE SUNDAY NIGHT IS COMPLICATED, AND THE DETAILS REMAIN
UNCERTAIN. THESE DETAILS WILL BE CRUCIAL, AS A SUBTLE SHIFT OF A
SINGLE DEGREE IN TEMPERATURE WILL MAKE A DIFFERENCE IN
PRECIPITATION TYPE. ADD IN THE TIMING ERRORS FOR PRECIPITATION
AT ALL, AND THE RESULT IS A COMPLICATED FORECAST. THE LATEST
TREND IN THE GUIDANCE IS FOR A SLOWER ARRIVAL TIMING, WHICH
MAKES SENSE GIVEN THE LARGE HIGH PRESSURE THAT SHOULD BE JUST TO
OUR EAST. EVEN BY DAYBREAK MONDAY, SURFACE MSLP SHOULD BE 1035+
MB. THUS, IT MAY BE DIFFICULT TO GENERATE PRECIPITATION AT ALL.
WILL TREND THE FORECAST TO A SLOWER TIMING, BUT FURTHER TIMING
ADJUSTMENTS MAY BE NEEDED FOR SUNDAY NIGHT.
IN GENERAL FOR THIS UPDATE, THINKING SNOW IS THE MOST LIKELY
TYPE THROUGH ABOUT 2 AM, WHERE IT PRECIPITATES AT ALL. THEN
A WARMING TREND BEGINS HIGHER UP IN THE ATMOSPHERE. DIFFERENCES
IN THE GUIDANCE, WITH THE GFS HOLDING ONTO A COLDER SOLUTION IN
THE IDEA OF A WEAKER WARM NOSE OVER A GREATER DEPTH WHEN
COMPARED TO THE NAM. THE NAM HAD A SHALLOWER WARM NOSE, BUT IT
WAS MORE POTENT. BOTH OF THESE SCENARIOS DO DEPICT THE SAME
PATTERN, ONE OF A TRANSITION FROM SNOW TO RAIN, WITH A PERIOD
OF FREEZING RAIN SOME TIME IN BETWEEN. DO NOT HAVE ENOUGH
CONFIDENCE FOR A WINTER WEATHER ADVISORY AT THIS TIME. HOWEVER,
ONE MAY BE ISSUED WITH LATER FORECASTS AS CONFIDENCE IN THE
TIMING AND LOCATION OF FREEZING RAIN INCREASES.
INCREASING CLOUDS DURING THE AFTERNOON, WITH EVEN MORE CLOUDS
SUNDAY NIGHT. BELOW NORMAL TEMPERATURES SUNDAY, TEN TRENDING
CLOSER TO NORMAL SUNDAY NIGHT.
LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
KEY MESSAGES:
* UNSETTLED START TO NEXT WEEK WITH SOME LIGHT FROZEN
PRECIPITATION POSSIBLE MONDAY MORNING
* DRYING OUT WEDNESDAY BEFORE ANOTHER LOW-PRESSURE SYSTEM
PRODUCES SUBSTANTIAL PRECIPITATION DURING THE WEDNESDAY
NIGHT/THURSDAY TIME FRAME
* TRENDING COOLER NEXT WEEKEND WITH THE POTENTIAL FOR SOME
UNSETTLED WEATHER
MONDAY AND TUESDAY
HIGH PRESSURE CONTINUES TO SLOWLY BUILD EAST OF SOUTHERN NEW
ENGLAND DURING THE FIRST HALF OF MONDAY. SOUTHERLY FLOW/WARM
ADVECTION WEST OF THE ASSOCIATED MID-LEVEL RIDGE AXIS IS LIKELY
TO SUPPORT A PERIOD OF LIGHT PRECIPITATION FOR PORTIONS OF
SOUTHERN NEW ENGLAND MONDAY MORNING INTO EARLY MONDAY AFTERNOON.
WITH LOW TEMPS IN THE LOW TO MID 20S TO START MONDAY,
PRECIPITATION SHOULD FALL AS LIGHT SNOW AS AS TEMPERATURES
THROUGH 850 HPA WILL BE BELOW FREEZING AS WELL. HOWEVER AS WE
PROGRESS INTO MID- MORNING PERSISTENT WARM ADVECTION WILL
EVENTUALLY RESULT IN 925 HPA TEMPS CLIMBING ABOVE 0 CELSIUS
WHICH WILL INTRODUCE A WARM NOSE/MELTING LAYER IN THE COLUMN.
WITH SURFACE TEMPS STILL WELL BELOW FREEZING ACROSS
INTERIOR/NORTHWEST MA, A PERIOD OF FREEZING RAIN MAY BE POSSIBLE
TOWARD THE END OF THE MONDAY MORNING COMMUTE FOR LOCATIONS WEST
OF I-495. ELSEWHERE, SURFACE TEMPS SHOULD BE EDGING ABOVE
FREEZING AS THE WARMER AIR ALOFT NOSES IN, WHICH SHOULD SUPPORT
ANY SNOW CHANGING OVER TO RAIN. QUITE A TRICKY FORECAST AS
TIMING WILL BE PLAY A CRUCIAL ROLE IN POTENTIAL FROZEN
PRECIPITATION. GUIDANCE HAS BEEN TRENDING TOWARD A SLOWER
ARRIVAL OF PRECIPITATION THANKS TO THE LARGE AREA OF SURFACE
HIGH PRESSURE THAT'S IN PLACE. SHOULD THE LATE TREND CONTINUE,
SURFACE TEMPS MAY HAVE MORE TIME TO WARM LIMITING THE POTENTIAL
FOR FROZEN PRECIP. CONSULTING ENSEMBLE GUIDANCE, WE FIND ONLY A
10 TO 20 PERCENT CHANCE FOR GREATER THAN 0.01 INCHES OF ICE
ACCUMULATION AND A 10 TO 30 PERCENT CHANCE OF SNOW ACCUMULATIONS
GREATER THAN 1 INCH FOR LOCATIONS WEST OF WORCESTER. THUS, A
LOW IMPACT EVENT IF IT COMES TO FRUITION, BUT SOMETHING WE'LL
HAVE TO MONITOR OVER THE NEXT 36 HOURS OR SO.
BY TUESDAY EVENING, A COLD FRONT APPROACHING FROM THE WEST WILL
SUPPORT ANOTHER ROUND OF SUBSTANTIAL RAINFALL WITH ENSEMBLE
MEANS COMING IN AROUND 0.25 TO 0.5 INCHES BETWEEN MONDAY NIGHT
AND TUESDAY MORNING. THIS WILL BE ACCOMPANIED BY A WARMING TREND
AS SOUTHWEST FLOW AHEAD OF THE COLD FRONT HELPS 925 HPA TEMPS
RISE CLOSE TO 10 CELSIUS. THIS WILL SUPPORT SURFACE TEMPS IN THE
50S ON TUESDAY. TEMPERATURES RETURN TO NORMAL BY WEDNESDAY
MORNING (UPPER 20S/LOWER 30S) AS THE AIR MASS BEHIND THE COLD
FRONT SETTLES OVER THE REGION.
WEDNESDAY AND THURSDAY
BRIEFLY DRYING OUT ON WEDNESDAY BEHIND A WEAK SURFACE COLD
FRONT. WINDS QUICKLY SHIFT FROM WNW TO SOUTHWEST EARLY WEDNESDAY
ALLOWING MILD AIR TO CREEP BACK INTO THE NORTHEAST, THUS ANOTHER
MILD AFTERNOON IN THE MID TO UPPER 40S. THIS WILL BE FOLLOWED
BY ANOTHER FRONTAL SYSTEM PUSHING THROUGH THE REGION WITH MORE
RAINFALL. LATEST GUIDANCES SUGGESTS THE ASSOCIATED COLD FRONT
AND PRECIPITATION SHOULD BE EXITING THE AREA THURSDAY AFTERNOON,
BUT TIMING AT THIS TIME RANGE IS UNCERTAINTY.
FRIDAY AND SATURDAY
A POLAR AIR MASS SETTLES OVER THE NORTHEAST BEHIND THURSDAY'S
FRONTAL SYSTEM. MODELS ARE IN AGREEMENT WITH RESPECT TO BELOW
NORMAL TEMPERATURES, BUT THERE IS A BIT OF SPREAD WHEN IT COMES
TO PRECIPITATION CHANCES. SOME SOLUTIONS SUPPORT SHORTWAVE
ENERGY OVER ONTARIO/QUEBEC PRODUCING SOME CHANCES FOR MODEST
SNOW ON FRIDAY AND SATURDAY. ENSEMBLES SUGGEST A 20 TO 30
PERCENT CHANCE OF 1+ INCHES OF SNOW BOTH FRIDAY AND SATURDAY, SO
CONFIDENCE IN SNOW IS LOW AT THIS TIMES. CHECK BACK LATER THIS
WEEK FOR MORE DETAILS.
AVIATION /06Z SUNDAY THROUGH THURSDAY/
FORECAST CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
TODAY...HIGH CONFIDENCE.
VFR, OUTSIDE OF SOME OCEAN-EFFECT CLOUDS AND SOME MARGINAL MVFR
CEILINGS AT TIMES ALONG PORTIONS OF THE IMMEDIATE COAST, MAINLY
THE CAPE AND NANTUCKET. LIGHT WINDS GENERALLY OUT OF THE N/NNE.
SUNDAY NIGHT...MODERATE CONFIDENCE.
MAINLY VFR. AREAS MVFR POSSIBLE, MAINLY TOWARDS THE BERKSHIRES.
LIGHT SNOW POSSIBLE AFTER MIDNIGHT, WITH A RISK OF SOME -FZRA
TOWARDS DAYBREAK MONDAY ACROSS THE WESTERN HALF OF SOUTHERN NEW
ENGLAND.
KBOS TAF...HIGH CONFIDENCE IN TAF.
KBDL TAF...HIGH CONFIDENCE IN TAF.
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...
MONDAY NIGHT: MVFR/IFR CONDITIONS POSSIBLE. BREEZY. RA LIKELY,
CHANCE FZRA.
TUESDAY: MAINLY VFR, WITH LOCAL IFR POSSIBLE. BREEZY. RA
LIKELY.
TUESDAY NIGHT: VFR. BREEZY.
WEDNESDAY: VFR. CHANCE RA.
WEDNESDAY NIGHT: MVFR/IFR CONDITIONS POSSIBLE. BREEZY. RA
LIKELY.
THURSDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. BREEZY. CHANCE
RA.
MARINE
FORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THROUGH SUNDAY NIGHT...
A VERY STRONG HIGH PRESSURE MOVES OVER NEW ENGLAND TONIGHT,
THEN OFFSHORE SUNDAY NIGHT INTO MONDAY. LIGHT WINDS AND SEAS
EXPECTED. LOW RISK FOR SOME RAINFALL LATE SUNDAY NIGHT ACROSS
THE RI COASTAL WATERS.
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...
MONDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 30 KT. AREAS OF SEAS APPROACHING 5 FT. CHANCE OF
RAIN.
TUESDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 30 KT. AREAS OF ROUGH SEAS. RAIN LIKELY.
TUESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT.
WEDNESDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT. SLIGHT CHANCE OF RAIN.
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS
APPROACHING 5 FT. RAIN.
THURSDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS UP
TO 20 KT. SEAS UP TO 5 FT. RAIN LIKELY.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...NONE.
SYNOPSIS...BELK/RM
NEAR TERM...BELK
SHORT TERM...BELK
LONG TERM...RM
AVIATION...FRANK/MENSCH
MARINE...BELK/RM
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