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Area Forecast Discussion
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000
FXUS61 KBOX 230227
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
927 PM EST MON DEC 22 2014

.SYNOPSIS...
LOW PRESSURE MOVING UP THE COAST WILL BRING PERIODS OF RAIN TO NEW
ENGLAND OVERNIGHT INTO TUESDAY...WITH WET SNOW POSSIBLE ACROSS 
NORTHWEST MASSACHUSETTS. A MUCH STRONGER STORM PASSING WELL TO
OUR WEST WED INTO CHRISTMAS MORNING WILL BRING HEAVY RAIN...GUSTY
WINDS AND PROBABLY MINOR COASTAL FLOODING. DRY WEATHER WITH ABOVE
NORMAL TEMPS EXPECTED CHRISTMAS AFTERNOON INTO SAT. UNSETTLED
WEATHER MAY RETURN FOR SUN AND MON.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
925 PM UPDATE...

SCATTERED SHOWERS FROM EASTERLY FLOW OFF OCEAN WERE PUSHING
THROUGH MERRIMACK VALLEY AND WILL LIFT FARTHER NW OVERNIGHT.
MEANWHILE NEXT BATCH OF SHOWERS ASSOCIATED WITH WEAK LOW PRESSURE
TO OUR S WILL ARRIVE FROM SW TO NE OVERNIGHT PER HIGH-RES MODEL
GUIDANCE.

TEMPERATURES WERE ABOVE FREEZING JUST ABOUT EVERYWHERE...EVEN
NEAR BERKSHIRES WERE MESONET DATA SHOWS TEMPERATURES NEAR 33 OR 34
DEGREES. DESPITE NORTHERLY AGEOSTROPHIC FLOW AT LOWER LEVELS IN
RESPONSE TO LOW PRESSURE PASSING OFFSHORE OVERNIGHT...POTENTIAL
FOR FREEZING RAIN REMAINS VERY LOW ACROSS INTERIOR.

ADJUSTED OVERNIGHT LOWS UP A TAD BASED UPON CURRENT OBSERVATIONS
AND HIGH-RES MODELS...FROM LOWER 30S NW TO LOWER 40S SE.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
TUESDAY...
THE SOUTHEAST LOW LEVEL JET WILL MOVE ACROSS SOUTHERN NEW ENGLAND
DURING THE DAY. THIS WILL FEED MOISTURE TO MAINTAIN A SATURATED
AIRMASS THROUGH MOST OF THE COLUMN...AND BRING OUR BEST CHANCE OF
RAIN. THE JET MOVES NORTH OF OUR AREA DURING THE AFTERNOON WHICH
WILL BRING DIMINISHING CHANCE OF PCPN.

AS WARMER AIR FILLS IN...TEMPERATURES WILL MODERATE FURTHER WITH
VALUES MOSTLY IN THE 40S.

THE STEADY SOUTHEAST FLOW WILL BE 15-25 MPH WITH SOME HIGHER GUSTS
POSSIBLE. THIS WINDS COMES AFTER A STEADY EAST FLOW TODAY WHICH
HAS PUSHED THE OCEAN TOWARD THE EAST MASS COAST. THIS SUGGESTS
BUILDING OCEAN LEVELS NEARSHORE...WITH SOME MINOR COASTAL
FLOODING CONCERNS ALONG THE EAST MASSACHUSETTS COAST. THE BEST
CHANCE WOULD BE AROUND BOSTON HARBOR AND NEAR SCITUATE.

TUESDAY NIGHT...
THE SOUTHEAST JET MOVES OFF TO THE NORTH. WE WILL CONTINUE TO HAVE
A MOIST AIRMASS WITH WARM ADVECTION AND LOW LEVEL LIFT. THE RESULT
WILL BE LINGERING SHOWERS AND DRIZZLE TUESDAY NIGHT. LOW LEVEL
SOUTH JET WILL MOVE UP THE ATLANTIC COAST OVERNIGHT AND REACH
SOUTHERN NEW ENGLAND AFTER MIDNIGHT. THIS WILL BRING INCREASED
LIFT WHICH WILL MEAN INCREASED COVERAGE OF SHOWERS LATE AT NIGHT.
THIS SOUTH JET IS ALSO DRAWING AN ANOMALOUSLY HUMID AIRMASS NORTH
WITH PRECIPITABLE WATER VALUES OVER 1.5 INCHES. SHOWERS DEVELOPING
LATE TUESDAY NIGHT WILL LIKELY HAVE SOME EMBEDDED DOWNPOURS.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
HIGHLIGHTS...

* PERIODS OF RAIN WEDNESDAY INTO CHRISTMAS MORNING WILL BE HEAVY AT 
  TIMES
* DRY BUT WINDY BY CHRISTMAS AFTERNOON
* TEMPS AROUND 60 FOR SOME LATE WED INTO CHRISTMAS MORNING
* DRY BUT ABOVE NORMAL TEMPS CONTINUE FRI AND SAT
* UNSETTLED WEATHER MAY RETURN FOR SUN BUT CONFIDENCE IS LOW

MODELS ARE IN DECENT AGREEMENT ON THE FIRST PART OF THE LONG TERM 
FORECAST.  THERE HAS BEEN QUITE A BIT OF RUN TO RUN VARIABILITY ON 
THE TRACK OF THE STRONG SHORTWAVE AND SURFACE LOW EXPECTED TO MOVE 
THROUGH THE GREAT LAKES CHRISTMAS EVE.  WHILE THE OVERALL PATTERN 
HAS BEEN WELL MODELED SINCE LAST WEEK...THIS VARIABILITY HAS LED TO 
SOME UNCERTAINTY...PARTICULARLY WITH THE WINDS AND THE QPF.  BEYOND 
THE CHRISTMAS STORM...MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH 
THE FIRST PART OF THE WEEKEND.  THEN ALL AGREEMENT GOES OUT THE 
WINDOW FOR THE LATTER PART OF THE WEEKEND INTO THE FIRST PART OF 
NEXT WEEK.  THE ECMWF HAS A STRONG LOW PRESSURE SYSTEM DEVELOPING 
SOUTH OF THE AREA AND MOVING ALONG THE SOUTH COAST SUNDAY WHILE THE 
GFS HAS A STRONG HIGH PRESSURE RIGHT OVER SOUTHERN NEW ENGLAND.  
GIVEN THE HUGE DIFFERENCE HERE...OPTED FOR A BLEND AND MENTION OF 
THE VARIABILITY HERE.

CHRISTMAS EVE AND DAY...STRONG SHORTWAVE MOVES THROUGH THE GREAT 
LAKES CHRISTMAS EVE AND INTO QUEBEC ON CHRISTMAS DAY.  IN 
RESPONSE...LOW PRESSURE DEVELOPS AT THE SURFACE AND MOVES ACROSS THE 
GREAT LAKES INTO CANADA ON CHRISTMAS EVE.  DEEP SOUTHERLY FLOW OVER 
SOUTHERN NEW ENGLAND WILL ALLOW SIGNIFICANTLY WARMER THAN NORMAL AIR 
TO MOVE OVER THE AREA RESULTING IN TEMPERATURES CLIMBING AS HIGH AS 
60 ACROSS SOUTHEASTERN MASSACHUSETTS AND RHODE ISLAND FROM WEDNESDAY 
AFTERNOON THROUGH CHRISTMAS MORNING.  

IN ADDITION...RAIN WILL MOVE IN ACROSS SOUTHERN NEW ENGLAND FOR ALL 
OF WEDNESDAY INTO CHRISTMAS MORNING. WHILE QPF AMOUNTS FORECAST BY 
THE MODELS HAVE VARIED QUITE A BIT AS WE MOVE CLOSER TO THE 
EVENT...CAUSING GREATER UNCERTAINTY IN HOW MUCH RAIN WE 
ANTICIPATE...THE GEFS HAS BEEN VERY CONSISTENT IN FORECASTING PWAT 
VALUES 4 TO 5 STANDARD DEVIATIONS ABOVE NORMAL. THIS PRESENTS QUITE 
A CONCERN AS RAIN WILL BE QUITE HEAVY AT TIMES.  AT THIS POINT...WE 
ARE LOOKING AT A WIDESPREAD 1 TO 3 INCH EVENT WITH HIGHER LOCALIZED 
AMOUNTS.  THIS WOULD CERTAINLY BE ENOUGH TO PRODUCE TYPICAL NUISANCE 
STREET FLOODING.  HOWEVER...WOULD NOT RULE OUT MORE WIDESPREAD 
FLOODING GIVEN THE HIGHLY ANOMALOUS PWATS THAT ARE FORECAST. WILL BE 
MONITORING OVER THE NEXT DAY OR SO FOR A POTENTIAL FLOOD WATCH.
 
HAVE KEPT THE SLIGHT CHANCE OF THUNDER GIVEN K INDICES OVER 30 AND 
SHOWALTER INDICES NEAR ZERO.  THE GREATEST CHANCE OF THIS IS SOUTH 
OF THE MASS PIKE THOUGH THERE IS POTENTIAL FOR SOME ISOLATED THUNDER 
ALONG THE EAST COAST WEDNESDAY AFTERNOON.  IN ADDITION...HAVE ADDED 
GUSTY WINDS AND HEAVY RAINFALL WORDING EVERYWHERE.  
CONSERVATIVELY...A 50 TO 60 KT LOW LEVEL JET WILL BE OVER SOUTHERN 
NEW ENGLAND...ESPECIALLY LATE WEDNESDAY AFTERNOON AND WEDNESDAY 
NIGHT.  WHILE AN INVERSION LOOKS TO KEEP THE STRONGEST OF THESE 
WINDS FROM REACHING THE SURFACE...THERE IS POTENTIAL FOR SOME OF 
THESE WINDS TO BE BROUGHT DOWN IN ANY STRONGER SHOWERS OR HEAVY 
RAINFALL.

THE RAIN SHOULD COME TO AN END CHRISTMAS MORNING WHILE TEMPERATURES 
PEAK OUT AROUND 60 FOR MUCH OF THE REGION.  DESPITE THE STRONGER LOW 
LEVEL JET WEDNESDAY NIGHT...THERE IS A MUCH BETTER CHANCE FOR THE 
WINDS TO MIX TO THE SURFACE CHRISTMAS AFTERNOON AND EVENING.  BEHIND 
THE SYSTEM...THERE ARE STRONGER WESTERLY WINDS AND STEEPER MID LEVEL 
LAPSE RATES.  ADVISORY LEVEL WIND GUSTS ARE FAIRLY CERTAIN... 
PARTICULARLY ACROSS SOUTHEASTERN MASSACHUSETTS...THE CAPE...AND 
ISLANDS WITH A LOW PROBABILITY OF HIGH WIND CRITERIA BEING MET.  
WILL BE WATCHING THIS FOR ANY HEADLINE ISSUANCE OVER THE NEXT DAY OR 
SO.

FRIDAY AND SATURDAY...HIGH PRESSURE SLIDES SOUTH OF SOUTHERN NEW 
ENGLAND BRINGING DRY WEATHER...AND ABOVE NORMAL TEMPERATURES.

SUNDAY AND MONDAY...LOW CONFIDENCE FORECAST AS MENTIONED ABOVE WITH 
WILDLY DIFFERENT SOLUTIONS FROM THE ECMWF AND THE GFS.  HAVE OPTED 
FOR SLIGHT CHANCE TO CHANCE POPS FOR THE TIME BEING...RECOGNIZING 
THAT IF THE GFS IS CORRECT THESE WILL BE WAY TOO HIGH AND IF THE 
ECMWF IS CORRECT...WAY TOO LOW.  POTENTIALLY UNSETTLED WEATHER 
DURING THIS TIME PERIOD AND DEFINITELY MUCH COOLER TEMPERATURES.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT. 
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /THROUGH TUESDAY NIGHT/...MODERATE CONFIDENCE.

CIGS LOWERING TO MVFR THROUGHOUT AREA OVERNIGHT WITH POCKETS OF
IFR PRIMARILY ACROSS HIGHER TERRAIN. SHOWERS BECOME MORE NUMEROUS
FROM SW TO NE AFTER MIDNIGHT.

TUESDAY...MVFR CONDITIONS MAY LOWER TO IFR IN SHOWERS. THE CORE
OF THE SHOWERS WILL BE OVER OUR AREA DURING THE MORNING AND EARLY
AFTERNOON...WITH VSBYS REDUCED TO 2-3SM IN THE HEAVIER SHOWERS.
SHOWERS DIMINISH LATE IN THE DAY WITH VSBYS 5-6 MILES BUT CIGS
LINGER AT 1000-1500 FEET.

TUESDAY NIGHT...AFTER A SHORT PAUSE EARLY IN THE NIGHT...THE
CHANCE OF SHOWERS WILL INCREASE AGAIN OVERNIGHT. CIGS WILL BE IFR
OR LOW-END MVFR. VSBYS WILL BE 3-4 MILES WITH AREAS OF 2 MILE
VSBYS.

KBOS TERMINAL...MODERATE CONFIDENCE. VFR CIGS SHOULD PERSIST
THROUGH 05Z OR SO...BEFORE SHOWERS ARRIVE FROM SW AND BRING MVFR
CIGS. 

KBDL TERMINAL...MODERATE CONFIDENCE. 

OUTLOOK...WEDNESDAY THROUGH SATURDAY...

WEDNESDAY...HIGH CONFIDENCE.  MVFR/IFR CONDITIONS IN WIDESPREAD -RA. 
LLWS IS LIKELY PARTICULARLY WEDNESDAY AFTERNOON AND EVENING AS WINDS 
AT THE SURFACE ARE LIKELY TO BE BELOW 10 KTS WHILE A SOUTHERLY LLJ 
SCREAMS OVERHEAD AT 50-60KTS.  

CHRISTMAS...MODERATE CONFIDENCE.  CONDITIONS IMPROVE TO VFR AS 
SYSTEM CLEARS OUT.  WESTERLY WINDS INCREASE DURING THE AFTERNOON 
GUSTING TO AROUND 40 KTS.

FRIDAY AND SATURDAY...MODERATE CONFIDENCE. VFR.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT. 
MODERATE...30 TO 60 PERCENT. 
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /THROUGH TUESDAY NIGHT/...MODERATE TO HIGH CONFIDENCE.

HIGH PRESSURE ACROSS QUEBEC AND THE MARITIMES WILL RESULT IN 
PERSISTENT NORTHEASTERLY TO EASTERLY WINDS ACROSS THE WATERS
TONIGHT. LOW PRESSURE MOVING UP THE ATLANTIC COAST WILL TIGHTEN
THE PRESSURE GRADIENT A LITTLE TONIGHT...AND MAY ALLOW WINDS TO
GUST AROUND 20 KNOTS OR IN THE LOW 20S. THE PERSISTENT ESE FLOW
WILL ALLOW SEAS TO BUILD TO 5 FEET ON THE EASTERN OUTER
WATERS...WITH 2-4 FEET MOST OTHER WATERS. SMALL CRAFT ADVISORY
CONTINUES.

APPROACHING SURFACE LOW PRESSURE FROM THE MID-ATLANTIC TONIGHT WILL 
HELP INCREASE AN EASTERLY LLJ OVER THE WATER TUESDAY. THIS WILL
BUILD THE SEAS BETWEEN 5-8 FT. COULD SEE WIND GUSTS BETWEEN 20-30
KTS AS THE FRONT PASSES. THE SMALL CRAFT ADVISORY HAS BEEN EXPANDED
ACCORDINGLY.

SOUTHEAST WINDS WILL DIMINISH BUT MAINTAIN TRANSPORT OF OCEAN
WATER TOWARD THE NEW ENGLAND COASTLINE ESPECIALLY ALONG EASTERN
MASSACHUSETTS. EXPECT SEAS AT OR ABOVE 5 FEET ON MANY OF THE
SOUTHERN NEW ENGLAND WATERS THROUGH THE NIGHT. WINDS SHOULD
GENERALLY BE BELOW SMALL CRAFT THRESHOLDS.

OUTLOOK...WEDNESDAY THROUGH SATURDAY...MODERATE CONFIDENCE

SEAS INCREASE WEDNESDAY INTO CHRISTMAS MORNING AS A COLD FRONT 
APPROACHES AND THEN CROSSES THE WATERS.  HIGH PRESSURE THEN BUILDS 
OVER THE WATERS FRIDAY AND SATURDAY ALLOWING SEAS TO SUBSIDE.  
SOUTHERLY GALES WEDNESDAY INTO CHRISTMAS MORNING WILL GIVE WAY TO 
WESTERLY GALES AS THE COLD FRONT MOVES ACROSS.  

VISIBILITIES WILL BE REDUCED WEDNESDAY INTO CHRISTMAS MORNING IN 
RAIN AND THERE IS A SLIGHT CHANCE OF THUNDER WEDNESDAY.

&&

.TIDES/COASTAL FLOODING...
HIGH ASTRONOMICAL TIDES OCCUR TUE AND WED.  

EAST MASSACHUSETTS COAST:

TUESDAY...HIGH TIDE AT BOSTON WILL BE 11.6 FEET AT MIDDAY WITH A
SURGE OF 1 TO 1.5 FEET. WINDS WILL BE FROM THE EAST AT 10 TO 15
KNOTS...SO THERE WILL BE ONSHORE FLOW DURING THIS HIGH TIDE. WHILE
THIS IS NOTHING TOO STRONG...GIVEN THE HIGH ASTRO TIDE AND
PERSISTENCE OF EAST WINDS WE EXPECT SOME SPLASH OVER/MINOR
COASTAL FLOODING. CERTAINLY DO NOT EXPECT TO SEE ANY SIGNIFICANT
ISSUES. A COASTAL FLOOD ADVISORY HAS BEEN ISSUED FOR THE EAST MASS
COASTLINE FOR THIS MIDDAY HIGH TIDE.
 
WEDNESDAY...HIGH TIDE AT BOSTON WILL BE AT 11.7 FEET AT MIDDAY
WITH A SURGE OF 1 TO 1.5 FEET. WINDS WILL BE FROM THE SOUTHEAST
NEAR 10 KNOTS BUT THERE WILL BE SOME PRESSURE FALLS WITH
INTENSIFYING LOW PRESSURE TO OUR WEST. THIS SHOULD BE ENOUGH FOR
MORE SPLASH OVER/MINOR COASTAL FLOODING WITH THE HIGH ASTRO TIDES.
HOWEVER...DO NOT EXPECT ANY SIGNIFICANT PROBLEMS GIVEN WINDS/SEAS
SHOULD BE HELD IN CHECK DURING THE TIME OF HIGH TIDE.

SOUTH COAST:

WEDNESDAY EVENING...SOUTHERLY WINDS ARE EXPECTED AND ASTRONOMICAL 
TIDES INCREASE ALONG THE SOUTH COAST. HIGH TIDE IN PROVIDENCE WILL 
BE 5.2 FEET WEDNESDAY EVENING. 925 MB LLJ STRENGTHENS TO 55-65
KTS WHICH COULD PUSH A 1 TO 2 FOOT SURGE UP ALONG THE SOUTH COAST
DURING THE TIME OF HIGH TIDE. THE LOW LEVEL INVERSION WILL
PROBABLY HOLD THE STRONGEST WINDS JUST ABOVE THE GROUND...SO
THINKING THE RISK IS FOR SPLASH OVER AND MINOR COASTAL FLOODING.
THERE STILL IS A LOW RISK FOR MODERATE COASTAL FLOODING...BUT THAT
IS OFTEN HARD TO GET IN A NON-TROPICAL SYSTEM ALONG THE SOUTH
COAST.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...COASTAL FLOOD ADVISORY FROM 9 AM TO 3 PM EST TUESDAY FOR 
     MAZ007-015-016-019-022.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 1 AM TO 7 PM EST TUESDAY FOR ANZ231-
     232.
     SMALL CRAFT ADVISORY FROM 1 AM TO 10 AM EST TUESDAY FOR ANZ233-
     234.
     SMALL CRAFT ADVISORY FROM 1 AM TUESDAY TO 6 AM EST WEDNESDAY 
     FOR ANZ235-237-251-256.
     SMALL CRAFT ADVISORY UNTIL 6 AM EST WEDNESDAY FOR ANZ250-254.
     SMALL CRAFT ADVISORY UNTIL 6 AM EST WEDNESDAY FOR ANZ255.

&&

$$
SYNOPSIS...WTB/RLG
NEAR TERM...JWD
SHORT TERM...WTB
LONG TERM...RLG
AVIATION...WTB/RLG
MARINE...WTB/RLG
TIDES/COASTAL FLOODING...



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