614
FXUS61 KBOX 180822
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
322 AM EST SAT JAN 18 2025
SYNOPSIS
AN APPROACHING COLD FRONT WILL RESULT IN A SOUTHERLY FLOW AND
MILDER TEMPERATURES TODAY WITH A PERIOD OF RAIN SHOWERS
THIS AFTERNOON INTO EARLY EVENING. A WAVE OF LOW PRESSURE MOVING
IN LATER SUNDAY AND SUNDAY NIGHT WILL BRING ACCUMULATING,
PLOWABLE SNOWFALL TO SOUTHERN NEW ENGLAND, THOUGH THE EXACT
FORECAST ACCUMULATIONS AND PRECIPITATION TYPES HINGING ON THE
TRACK AND INTENSITY OF THE LOW PRESSURE SYSTEM. THIS WILL BE
FOLLOWED BY AN ARCTIC OUTBREAK MONDAY INTO WEDNESDAY WITH WIND
CHILLS LIKELY DROPPING TO BETWEEN 5 AND 15 BELOW ZERO.
TEMPERATURES MODERATE A BIT BY THE END OF THE UPCOMING WORK
WEEK...BUT THERE IS A LOW RISK FOR A PERIOD OF SNOW LATE
THURSDAY NIGHT AND FRIDAY IF LOW PRESSURE TRACKS FAR ENOUGH
NORTHWEST.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
* ABOVE NORMAL TEMPERATURES AND BREEZY CONDITIONS TODAY.
* RAIN SHOWERS DEVELOP IN THE AFTERNOON, BECOMING MORE WIDESPREAD BY
EARLY EVENING.
TODAY:
A WEAK SHORTWAVE TROUGH AND COLD FRONT APPROACHES THE REGION TODAY.
MOISTURE GRADUALLY INCREASES INTO THE AFTERNOON WITH PRECIPITABLE
WATER VALUES AROUND 180-220% OF NORMAL BY EARLY EVENING. THIS WAVE
WILL BRING A BROAD AREA OF ASCENT SUPPORTING OUR NEXT CHANCE OF
PRECIPITATION. SHOWERS ARRIVE EARLY AFTERNOON, SPREADING FROM WEST
TO EAST, BECOMING MORE WIDESPREAD MID-AFTERNOON TO EARLY EVENING.
THERE WILL WILL BE A GOOD AMOUNT OF WAA ADVECTION AHEAD OF THIS
SYSTEM WITH 850MB TEMPERATURES WARMING 5-8C FROM FRIDAY BRINGING
HIGHS INTO THE 40S, POTENTIALLY 50 IN SPOTS. THIS WILL PUT US AROUND
6-12 DEGREES WARMER THAN NORMAL. THAT MEANS THIS WILL FALL AS RAIN
WITH THE EXCEPTION OF THE BERKSHIRES WHO MAY SEE LIGHT SNOW OR A
RAIN/SNOW MIX AT TIMES. IT WILL ALSO BE BREEZY WITH A LOW LEVEL
JET/ENHANCED GRADIENT POSITIONED ACROSS THE REGION. NO IMPACTFUL
WINDS ARE EXPECTED, BUT GUSTS 20-30 MPH ARE POSSIBLE.
TONIGHT:
RAIN DECREASES FROM WEST TO EAST THIS EVENING. A COLD FRONT MOVES
THROUGH SHIFTING WINDS TO THE NW. TEMPERATURES DROP INTO THE MID 20S
TO LOW 30S ACROSS THE INTERIOR AND LOW TO MID 30S CLOSER TO THE
COAST.
SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/
KEY MESSAGES...
* PLOWABLE SNOW LATE SUN/SUN NIGHT...AMOUNTS/PTYPE ISSUES UNCERTAIN
* WINTER STORM WATCH NW OF I-95 WHERE THE GREATEST RISK OF 4-8"
* TWO MAIN CAMPS...
- STRONGER/NW TRACK...HEAVY SNOW INTERIOR/PTYPE ISSUES COASTAL PLAIN
- WEAKER/SE TRACK...MAINLY SNOW NORTHWEST OF CAPE BUT LIGHTER AMOUNTS
DETAILS...
SUNDAY AND SUNDAY NIGHT...
THE FIRST HALF OF SUNDAY WILL FEATURE DRY WEATHER WITH EVEN PARTIAL
SUNSHINE IN THE MORNING. THE AIRMASS IS NOT INITIALLY THAT COLD...SO
WITH JUST A PERIOD OF SUNSHINE HIGHS PROBABLY TOP OFF IN THE UPPER
30S TO THE MIDDLE 40S WITH THE MILDEST READINGS ACROSS PARTS OF
RI/SE MA.
THE MAIN FORECAST CHALLENGE CONTINUES TO BE THE LIKELIHOOD OF A
PLOWABLE SNOWFALL LATE SUN INTO SUN NIGHT FOR MUCH OF THE REGION.
PRECIPITATION SHOULD DEVELOP BY MID TO LATE SUNDAY
AFTERNOON...ROUGHLY BETWEEN 2 AND 6 PM CONTINUING INTO SUNDAY NIGHT.
HOWEVER...THERE REMAINS TREMENDOUS SPREAD AMONGST THE MODELS AND
POTENTIAL SPECIFIC OUTCOMES. WE WILL BREAK IT DOWN MORE BELOW.
AN ANAFRONTAL WAVE OF LOW PRESSURE IN THE CAROLINAS EARLY SUN
MORNING WILL RACE NORTHEASTWARD. HOWEVER...THERE IS STILL
SIGNIFICANT MODEL DIFFERENCES ON THE TRACK AND INTENSITY OF THE WAVE
OF LOW PRESSURE. THE RGEM HAS CONTINUALLY BEEN THE STRONGEST AND
FURTHEST NORTHWEST WITH THIS LOW PRESSURE SYSTEM. IN FACT...THE
SYSTEM TRACKS SO CLOSE TO THE COAST THAT PTYPE WOULD MAINLY BE RAIN
ACROSS EASTERN MA/RI WITH HEAVY SNOW OF 6"+ ACROSS THE INTERIOR.
MEANWHILE...THE ECMWF AND NAM HAVE TENDED TO BE WEAKER AND FURTHER
SOUTHEAST WITH THIS LOW PRESSURE SYSTEM. THIS RESULTS IN A COLDER
SOLUTION BUT WITH LESS QPF...SO WHILE PTYPE WOULD MAINLY BE SNOW
NORTHWEST OF THE CAPE COD CANAL IT WOULD BE MORE OF AN ADVISORY TYPE
OF EVENT. THE GFS/UKMET LEAN MORE TOWARDS THE MORE AMPED UP
SOLUTIONS...ALBEIT NOT QUITE AS EXTREME AS THE RGEM. WHILE THERE IS
NOT A CLASSIC CLOSED MID LEVEL LOW...THE MORE AMPED SOLUTIONS DO
INDICATE A CLOSED 850 MB LOW WHICH WOULD SUPPORT AT LEAST A BRIEF
PERIOD OF STRONG FRONTOGENESIS/GOOD RATIO TYPE OF SNOW. THIS WOULD
RESULT IN A PERIOD OF 1-2" PER HOUR SNOWFALL RATES FOR A SHORT
DURATION IF IT MATERIALIZED.
GIVEN THE UNCERTAINTY THAT REMAINS...WE CONTINUE TO BLEND A LOT OF
THE GUIDANCE. WE ARE THINKING THAT THIS IS A BORDERLINE WINTER
WEATHER ADVISORY/LOW END WINTER STORM WARNING. THINKING THE GREATEST
RISK FOR 4-8" OF SNOW IS TO THE NORTHWEST OF I-95. THE STORM IS
FAIRLY PROGRESSIVE..BUT IF ENOUGH BANDING WERE TO DEVELOP A LOW RISK
WOULD EXIST FOR LOCALIZED 10" SNOW AMOUNTS. OVERALL..WE DID NOT MAKE
TOO MANY CHANGES TO THE GOING FORECAST OTHER THAN TO EXPAND THE
WINTER STORM WATCH INTO NORTHEAST MA. NOW IF SOME OF THE MORE AMPED
UP SOLUTIONS TICK A BIT FURTHER SOUTHEAST...LATER SHIFTS MAY HAVE TO
CONSIDER EXPANDING THE WINTER STORM WATCHES A BIT FURTHER SOUTHEAST.
NOT ENOUGH CONFIDENCE TO DO THAT RIGHT NOW GIVEN POTENTIAL PTYPE
ISSUES WITH A STRONGER/FURTHER NORTHWEST TRACK. AT THE SAME
TIME...THE WEAKER MORE STRUNG OUT SOLUTIONS LIKE THE NAM/ECMWF WOULD
RESULT IN PTYPE BEING MAINLY SNOW NORTHWEST OF THE CAPE COD
CANAL...BUT MORE OF A 2-5"/3-6" EVENT FOR A LARGE CHUNK OF OUR AREA.
SO IN A NUTSHELL...THIS EVENT LOOKS TO BE RIGHT ON THE CUSP BETWEEN
A WINTER WEATHER ADVISORY/WINTER STORM WARNING SETUP. AGAIN...WE
OPTED TO GO WITH A WATCH NORTHWEST OF I-95...WHICH SHOULD GIVE LATER
SHIFTS MORE FLEXIBILITY IN CONVERTING TO AN ADVISORY OR UPGRADING TO
A WARNING. THE GOOD NEWS IS THAT THE ACCUMULATING SNOW WILL HAVE
COME TO AN END IN TIME FOR THE MONDAY MORNING COMMUTE.
HOWEVER...TEMPS WELL BELOW FREEZING SHOULD RESULT IN UNTREATED ROADS
BEING SNOW COVERED AND SLIPPERY.
LONG TERM /MONDAY THROUGH FRIDAY/
KEY MESSAGES...
* ARCTIC OUTBREAK MON THROUGH WED WITH WIND CHILLS 5-15 BELOW ZERO
* LOWS TUE NIGHT/WED NIGHT...SINGLE DIGITS WITH SOME BELOW ZERO
* HIGHS TUE & WED ONLY IN THE MIDDLE TEENS TO THE LOWER 20S
* LOW PROBABILITY FOR A PERIOD OF SNOW LATE THU NIGHT AND/OR FRI
DETAILS...
MONDAY THROUGH WEDNESDAY...
THE GOOD NEWS IS THAT THE STEADY SNOW WILL PRETTY MUCH BE OVER BY
DAYBREAK MON. OTHERWISE, THE MAIN STORY WILL BE AN ARCTIC OUTBREAK
AND LIKELY THE COLDEST WEATHER SINCE EARLY FEBRUARY 2023! THE ARCTIC
AIRMASS BEGINS TO WORK INTO THE REGION MON ON BLUSTERY NW WINDS.
HIGHS ON MON PROBABLY MAINLY IN THE LOWER TO MIDDLE 20S WITH THE
BITTERLY COLD AIR WORKS INTO THE REGION LATE MON/MON NIGHT AND
CONTINUING INTO WED. OVERNIGHT LOW TEMPS WILL BE IN THE SINGLE
DIGITS MON NIGHT AND TUE NIGHT WITH SOME BELOW ZERO READINGS IN THE
OUTLYING LOCATIONS...ESPECIALLY TUE NIGHT WHEN WINDS START TO
DIMINISH. HIGH TEMPS TUE AND WED WILL ONLY BE IN THE MIDDLE TEENS TO
THE LOWER 20S. BLUSTERY NORTHWEST WINDS WILL PROBABLY DROP WIND
CHILLS INTO THE 5 TO 15 BELOW ZERO. COLD WEATHER ADVISORIES WILL
LIKELY BE NEEDED.
THURSDAY AND FRIDAY...
THE CORE OF THE COLDEST AIR WILL BEGIN TO DEPART ON THU...BUT TEMPS
SHOULD STILL BE WELL BELOW NORMAL WITH HIGHS MAINLY IN THE 20S. WE
ALSO WILL NEED TO WATCH FOR A LOW PROBABILITY FOR A PERIOD OF SNOW
LATE THU NIGHT INTO FRI. THE MAJORITY OF THE GUIDANCE KEEPS THIS
NEXT WAVE OF LOW PRESSURE TO THE SOUTH OF OUR REGION AND WE WOULD
REMAIN DRY. HOWEVER...A FEW EPS/GEFS/CMC ENSEMBLES TRACK THE SYSTEM
FURTHER NORTHWEST WHICH WOULD BRING A PERIOD OF SNOW TO THE REGION
SOMETIME LATE THU NIGHT AND/OR FRI. WE WILL LIKELY NEED SEVERAL MORE
DAYS UNTIL THINGS BECOME MORE CLEAR. MUCH OF THE REGION MAY SEE
HIGHS FINALLY BREAK 30 BY FRI.
AVIATION /08Z 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 /MONDAY THROUGH WEDNESDAY/...
VFR. BREEZY.
MARINE
FORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH- GREATER THAN 60 PERCENT.
HIGH CONFIDENCE.
S TO SW WINDS INCREASE SATURDAY WITH GUSTS 25-30 KTS. SEAS BUILD
TO 4-6 FT FOR THE OTUER COASTAL WATERS. SMALL CRAFT ADVISORIES
WILL BE ISSUED FOR THE OUTER COASTAL WATERS FOR A PERIOD FROM
LATE SATURDAY MORNING INTO EARLY SUNDAY MORNING. WINDS/SEAS
GRADUALLY DECREASE TOWARD MIDNIGHT SATURDAY.
OUTLOOK /MONDAY THROUGH WEDNESDAY/...
MARTIN LUTHER KING JR DAY: MODERATE RISK FOR SMALL CRAFT
ADVISORY WINDS WITH GUSTS UP TO 30 KT. ROUGH SEAS UP TO 9 FT.
FREEZING SPRAY.
MONDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. AREAS OF ROUGH SEAS. FREEZING SPRAY. LOCAL
VISIBILITY 1 TO 3 NM.
TUESDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS UP
TO 25 KT. AREAS OF SEAS APPROACHING 5 FT. FREEZING SPRAY.
TUESDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. SEAS LOCALLY APPROACHING 5 FT. FREEZING
SPRAY, SLIGHT CHANCE OF SNOW SHOWERS. AREAS OF VISIBILITY 1 TO
3 NM.
WEDNESDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS
UP TO 25 KT. SEAS LOCALLY APPROACHING 5 FT. FREEZING SPRAY,
SLIGHT CHANCE OF SNOW SHOWERS. LOCAL VISIBILITY 1 TO 3 NM.
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>012-014-026.
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...FRANK/MENSCH
NEAR TERM...MENSCH
SHORT TERM...FRANK
LONG TERM...FRANK
AVIATION...FRANK/MENSCH
MARINE...FRANK/MENSCH
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