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Area Forecast Discussion
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000
FXUS61 KBOX 181945
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
245 PM EST THU DEC 18 2014

.SYNOPSIS...
DRY AND SEASONABLE CONDITIONS WILL PREVAIL FRIDAY. AN UPPER LEVEL
DISTURBANCE AND MOIST NORTHEAST FLOW MAY BRING SOME LIGHT SNOW
SHOWERS SATURDAY INTO SUNDAY. LOW PRESSURE MAY IMPACT THE REGION
TUESDAY...WITH A MUCH STRONGER STORM LIKELY BRINGING HEAVY RAIN
AND WIND TO SOUTHERN NEW ENGLAND WEDNESDAY INTO WEDNESDAY EVENING.
DRY BUT VERY WINDY CONDITIONS FOLLOW FOR CHRISTMAS DAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
LOW PRES MOVES NE FROM THE MARITIMES BUT CYCLONIC FLOW WILL
PERSIST ALONG WITH SOME MOISTURE IN THE COLUMN WHICH WILL KEEP A
FEW CLOUDS ACROSS THE REGION ALTHOUGH DRY WEATHER EXPECTED. WHILE
GUSTY WINDS WILL DIMINISH TONIGHT...THERE IS ENOUGH PRESSURE
GRADIENT TO KEEP THE WINDS UP SO TEMPS WILL NOT DROP OFF THAT
QUICKLY. USED A BLEND OF AVAILABLE GUIDANCE WHICH SUGGESTS MIN
TEMPS MOSTLY IN THE 20S...WITH LOWER 30S OVER THE OUTER
CAPE/ISLANDS.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
FRIDAY...
HIGH PRES BUILDS ACROSS THE GT LAKES WITH NW FLOW ACROSS NEW ENG.
TRICKY CLOUD FORECAST AS NAM INDICATING LOW LEVEL MOISTURE TRAPPED
BELOW INVERSION WITH WIDESPREAD LOW CLOUDS...WHILE GFS AND ECMWF
ARE DRIER IN THE LOW LEVELS. GIVEN LOW LEVEL FLOW IS STILL NW...WE
WILL LEAN MORE OPTIMISTIC THAN NAM WITH A MIX OF CLOUDS AND SUN
EXPECTED. TEMPS WILL LIKELY BE 3-5 DEGREES COLDER THAN TODAY GIVEN
COOLING AT 925 MB...WITH MAX TEMPS RANGING FROM NEAR 30 HIGHER
TERRAIN IN NORTHERN AND WESTERN MA TO UPPER 30S IN THE COASTAL
PLAIN.

FRIDAY NIGHT...
MID LEVEL SHORTWAVE MOVES INTO W NEW ENG TOWARD DAYBREAK...BUT
FORCING IS WEAK THROUGH MOST OF THE NIGHT AND MOISTURE IS LIMITED
SO EXPECTING A MAINLY DRY NIGHT. HOWEVER...AS HIGH PRES BUILDS
EASTWARD ACROSS QUEBEC LOW LEVEL WINDS BECOME NE AND MODELS
INDICATE INCREASING LOW MOISTURE BACKING IN ACROSS SE NEW ENG
OVERNIGHT. DELTA T FROM SST TO THE TOP OF THE MIXED LAYER IS
AROUND 13C WHICH IS MARGINAL FOR OCEAN EFFECT AND OCEAN INDUCED
CAPES ARE NOT IMPRESSIVE...BUT LOW LEVEL LAPSE RATES ARE
INCREASING. MODELS DO SHOW SOME LIGHT QPF DEVELOPING SO THERE MAY
BE A FEW SNOW SHOWERS DEVELOPING OVER CAPE COD AND ACK OVERNIGHT
AND WE HAVE SOME LOW CHC POPS.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
HIGHLIGHTS...

* SCT SNOW/RAIN SHOWERS SAT INTO SUNDAY WITH BELOW AVG TEMPS
* WEAK WAVE OF LOW PRESSURE ON TUESDAY
* ANOMALOUS SYSTEM ACROSS THE GREAT LAKES WILL BRING HEAVY 
  RAIN...GUSTY WINDS AND COASTAL CONCERNS AROUND CHRISTMAS EVE

OVERVIEW...

OVERALL 00Z GUIDANCE IS IN AGREEMENT SYNOPTICALLY WITH ISSUES ON 
TIMING AND SMALLER SCALE FEATURES. AMPLIFIED PATTERN SET TO RETURN 
TO THE U.S. AS THE STRONG W PACIFIC JET TRANSLATES DOWNSTREAM THIS 
WEEKEND INTO THE PAC NW. BUILDING HEIGHTS OVER SE CANADA SHOULD ALSO 
HELP DIG THE TROUGH INTO THE OHIO VALLEY MIDWEEK AND LIKELY CLOSE 
OFF AS IT SWINGS INTO SOUTHERN CANADA ON CHRISTMAS DAY. 
MODELS/ENSEMBLES HAVE BEEN FAIRLY CONSISTENT IN RECENT RUNS ON THIS 
AMPLIFIED PATTERN AND THE MOST RECENT GEFS/ECMWF ENSEMBLE GUIDANCE 
SHOW GOOD CORRELATION TO NEXT THURSDAY. 

DURING THIS SYNOPTIC TRANSITION...HIGH PRESSURE AND UPPER LEVEL 
RIDGE WILL BE OVER THE NORTHEAST SATURDAY INTO SUNDAY. DIGGING 
TROUGH OVER THE CENTRAL CONUS WILL PUSH A SHORTWAVE ACROSS THE SE 
INTO THE MID-ATLANTIC. APPEARS THAT A WEAK COASTAL LOW WILL DEVELOP 
MOVING TOWARDS THE REGION MONDAY INTO TUESDAY. THE GFS BRINGS THIS 
LOW OVER THE BENCHMARK WHERE THE EC PUSHES WELL EASTWARD THANKS TO 
BUILDING HIGH PRESSURE OVER EASTERN CANADA. THIS SYSTEM IS WEAK SO 
COASTAL REGIONS HAVE THE BEST SHOT FOR PRECIP. AS THIS SYSTEM DEPART 
APPEARS ANOMALOUS LOW OVER THE GREAT LAKES WILL DEVELOP A SECONDARY 
LOW CLOSER TO NEW ENGLAND. THE GFS IS STILL A TAD FASTER COMPARED TO 
THE EC BUT OVERALL EXCELLENT MODEL AGREEMENT 6+ DAYS OUT. 

DETAILS...
 
SATURDAY INTO SUNDAY...HIGH CONFIDENCE.

HIGH PRESSURE IN EASTERN CANADA WILL BUILD ACROSS THE REGION FRIDAY 
NIGHT INTO SATURDAY. HOWEVER IT APPEARS ON FRIDAY NIGHT INTO 
SATURDAY NORTHERLY FLOW MAY ALLOW FOR SOME OCEAN EFFECT CLOUDS/SNOW 
SHOWERS TO IMPACT THE CAPE. SURFACE TO 850 MB TEMP DIFFERENCE IS 14C 
WHICH IS UNSTABLE ENOUGH FOR SNOW SHOWERS ON SATURDAY FOR THE CAPE. 
AM NOT ANTICIPATE MUCH IN THE WAY OF ACCUMULATIONS BUT A DUSTING 
CANNOT BE RULED OUT. 

WEAK WAVE WILL MOVE THROUGH THE FLOW ON SATURDAY NIGHT AND WITH HIGH 
PRESSURE SHIFTING EASTWARD EXPECT ONSHORE EASTERLY FLOW. GUIDANCE 
CONTINUES TO SHOW QPF MOVING ONSHORE AND WITH MOISTURE AND THE LIFT 
COULD SEE SNOW SHOWERS MOVING INLAND SATURDAY NIGHT INTO SUNDAY.  
BIGGEST QUESTION IS WILL THE MOISTURE SATURATE ENOUGH TO -6C. IF NOT 
THEN THE POTENTIAL FOR FREEZING DRIZZLE IS POSSIBLE. FOR NOW BELIEVE 
THAT THERE IS ENOUGH MOISTURE SO A QUICK HALF INCH TO AN INCH IS 
POSSIBLE PER SOUNDINGS EAST OF THE WORCESTER HILLS. 

MONDAY INTO TUESDAY...MODERATE CONFIDENCE. 

WEAK COASTAL LOW PRESSURE SYSTEM WILL DEVELOP AND MOVE SOMEWHERE 
BETWEEN THE BENCHMARK AND WELL OFFSHORE. BELIEVE A SOLUTION FATHER 
OUT TO SEA IS POSSIBLE DUE TO STRONG HIGH PRESSURE IN EASTERN 
CANADA. REGARDLESS A ROUND OF SHOWERS WILL MOVE ACROSS THE REGION 
WITH THE COASTAL AREAS HAVING THE BEST SHOT TO SEE PRECIP. THERMAL 
PROFILES WILL ALLOW FOR SNOW AT NIGHT AND RAIN DURING THE DAY. 

TEMPERATURES WILL SLOWLY BEGIN TO WARM AS SOUTHERLY FLOW BECOMES 
DOMINATE OUT AHEAD OF STRONGER SYSTEM TO THE EAST. 

TUESDAY HIGH TIDE WILL BE 11.6 IN BOSTON DURING THE LATE MORNING AND 
WITH ANY EASTERLY FLOW MAY ALLOW FOR MINOR COASTAL FLOODING.

WEDNESDAY INTO THURSDAY...HIGH CONFIDENCE IN SYSTEM LOW CONFIDENCE 
ON DETAILS. 

STRONG ANOMALOUS SYSTEM WILL STRENGTHEN OVER THE GREAT 
LAKES...DEVELOPING A SECONDARY SURFACE LOW JUST WEST OF SOUTHERN NEW 
ENGLAND. STILL A LOT OF DETAILS TO WORK OUT AS THIS SYSTEM IS STILL 
6 DAYS AWAY...HOWEVER ENSEMBLES SHOW THAT THIS SYSTEM IS AROUND 2 TO 
3 STANDARD DEVIATIONS ALLOWING FOR INCREASING CONFIDENCE THAT A 
POTENT STORM WILL OCCUR. LATEST 00Z GUIDANCE SHOWS THAT MOST PRECIP 
WILL BE LIQUID WITH A DEEP SUBTROPICAL CONNECTION BACK ACROSS 
MEXICO... PW ANOMALIES FORECAST TO RISE TO BETWEEN +1 TO +3 
/OR HIGHER/...AND TEMPERATURES WELL ABOVE AVERAGE. IN FACT WE MAY BE 
CLOSE AT BREAKING RECORD HIGH TEMPS IF TEMPS WARM TO 60F OR ABOVE ON 
CHRISTMAS EVE.  AS THE SYSTEM WRAPS UP INTO CANADA...COLD AIR 
ADVECTION SHOULD CIRCULATE AROUND AND BEGIN A TRANSITION FROM 
SOUTHWEST TO NORTHEAST IN TURNING P-TYPE TO SNOW. 

THIS SYSTEM IS QUITE STRONG SO WE WILL NEED TO WATCH FOR POSSIBLE 
URBAN FLOODING ISSUES AS WELL AS WIND ISSUES. GUIDANCE RIGHT NOW IS 
SHOWING A 40 TO 50 KT JET AT 925 MB WHICH MAY WARRANT WIND 
ADVISORIES BUT THIS SYSTEM COULD STRENGTHEN EVEN MORE SO A STRONGER 
JET IS POSSIBLE. LASTLY COASTAL FLOODING ISSUES WILL NEED TO BE 
ADDRESS AS HIGH TIDE ON WED AND THUS ARE 11.7 AND 11.5 RESPECTIVELY. 
ANY ONSHORE COMPONENT WILL PUSH THE TIDE ABOVE FLOOD SO COASTAL 
FLOODING IS POSSIBLE AS WELL AS BEACH EROSION.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /TODAY THROUGH FRIDAY NIGHT/...

THROUGH 00Z...LOW VFR/MVFR CIGS AROUND 3000-3500 FT. TREND SHOULD
BE FOR CLOUD DECK TO BECOME SCT TOWARD 00Z..ESPECIALLY NEAR THE
COAST. W/NW GUSTS TO 25-30 KT. 

TONIGHT...MODERATE CONFIDENCE. MAINLY VFR...BUT LINGERING MVFR
CIGS POSSIBLE IN THE WEST. DIMINISHING WIND. 

FRIDAY...LOW CONFIDENCE DUE TO UNCERTAINTY WITH EXTENT OF ANY MVFR
CIGS. WE HAVE MAINLY VFR IN THE TAFS WITH POCKETS OF MVFR...BUT
IT IS POSSIBLE MVFR CIGS COULD BE MORE EXPANSIVE IF LOW LEVEL
MOISTURE BECOMES TRAPPED BELOW THE INVERSION. LATER FORECASTS
WILL NEED TO REEVALUATE THIS.

FRIDAY NIGHT...MODERATE CONFIDENCE. MAINLY VFR...BUT MVFR CIGS
FROM THE OCEAN EXPANDING WEST ACROSS E MA. LOW PROB FOR SOME OCEAN
EFFECT SNOW SHOWERS OVER CAPE COD AND ACK AFTER MIDNIGHT.

KBOS TERMINAL...MODERATE CONFIDENCE. MAINLY VFR...BUT LOW PROB
FOR MVFR CIGS FRIDAY.

KBDL TERMINAL...MODERATE CONFIDENCE. SHOULD SEE MVFR CIGS SCATTER
OUT THIS EVENING. MVFR CIGS MAY RETURN FRI BUT THIS IS UNCERTAIN.

OUTLOOK...SATURDAY THROUGH MONDAY...

SATURDAY INTO SUNDAY...HIGH CONFIDENCE. MOSTLY VFR WITH MVFR
CONDITIONS ANY SCT SNOW/RAIN SHOWERS.

MONDAY...LOW CONFIDENCE. VFR CONDITIONS.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /TODAY THROUGH FRIDAY NIGHT/...HIGH CONFIDENCE.

TONIGHT...W/NW GUSTS 25-30 KT WILL LINGER OVER THE WATERS INTO
THIS EVENING BEFORE DIMINISHING OVERNIGHT. SCA HEADLINES WILL
CONTINUE TONIGHT.

FRIDAY...NW WINDS WILL BE BELOW SCA THRESHOLDS...BUT HAZARDOUS
SEAS WILL CONTINUE THROUGH THE MORNING OVER THE OUTER EASTERN 
WATERS...BEFORE SUBSIDING BELOW SCA. WILL LIKELY NEED TO EXTEND
THE SCA FOR SEAS INTO FRI MORNING. 

FRIDAY NIGHT...N/NW WINDS AND SEAS BELOW SCA. 

OUTLOOK...SATURDAY INTO MONDAY...MODERATE TO HIGH CONFIDENCE.

FRIDAY NIGHT INTO SUNDAY...ANTICIPATE DIMINISHING WINDS AND SEAS 
SUBSIDING LATE THU NIGHT INTO SATURDAY LEADING TO BELOW SMALL CRAFT 
ADVISORY LEVELS.
 
MONDAY...EXPECT NE WINDS GUSTING UP TO 20 KT. LOW PROB OF 25 KT 
GUSTS AS WELL AS 5 FT SEAS.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST FRIDAY FOR ANZ231-232-251.
     SMALL CRAFT ADVISORY UNTIL 11 PM EST THIS EVENING FOR 
     ANZ233>235-237.
     SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR ANZ230-
     236.
     SMALL CRAFT ADVISORY UNTIL 6 AM EST FRIDAY FOR ANZ250-254>256.

&&

$$
SYNOPSIS...KJC
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...DUNTEN
AVIATION...KJC/DUNTEN
MARINE...KJC/DUNTEN



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