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Area Forecast Discussion
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000
FXUS61 KBOX 272053
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
353 PM EST THU NOV 27 2014

.SYNOPSIS...
SCATTERED LIGHT SNOW SHOWERS/FLURRIES POSSIBLE THIS AFTERNOON. 
TONIGHT...A TROUGH OF LOW PRESSURE MAY PRODUCE ACCUMULATING SNOW 
ACROSS EASTERN MA INCLUDING THE BOSTON AREA. HIGH PRESSURE MOVES
OVER NEW ENGLAND FRIDAY AND SHIFTS OFFSHORE OVER THE WEEKEND. A
WARM FRONT MOVES ACROSS THE REGION LATE SATURDAY NIGHT AND EARLY
SUNDAY. A COLD FRONT THEN SWINGS THROUGH NEW ENGLAND MONDAY.
ANOTHER WARM FRONT/COLD FRONT COMBINATION WILL MOVE THROUGH THE
REGION WEDNESDAY AND WEDNESDAY NIGHT.

&&

.NEAR TERM /UNTIL MIDNIGHT TONIGHT/...
LIGHT SNOW SHOWERS AND FLURRIES MOVE OVER SOUTHERN NEW ENGLAND AS A 
SHORTWAVE APPROACHES SOUTHERN NEW ENGLAND.  MOST OF THESE 
SHOWERS/FLURRIES SHOULD REMAIN SOUTH OF THE MASS PIKE THOUGH A FEW 
MAY GRAZE THE NORTHWESTERN ZONES.  

AT THE SAME TIME...LOW PRESSURE DEVELOPS OFF THE COAST OF NORTH 
CAROLINA.  THIS WILL BECOME IMPORTANT FOR OUR WEATHER LATE TONIGHT 
INTO FRIDAY MORNING AS AN INVERTED TROUGH DEVELOPS OFF THIS LOW INTO 
PORTIONS OF NEW ENGLAND.

TEMPERATURES REMAIN IN THE 30S FOR MOST OF SOUTHERN NEW ENGLAND THIS 
AFTERNOON.  WHILE TEMPERATURES WILL DROP AFTER SUNSET...WITH 
OVERCAST SKIES IN PLACE...THEY WILL BE SLOW TO DROP...STAYING IN THE 
LOWER 30S THROUGH MIDNIGHT.

&&

.SHORT TERM /MIDNIGHT THROUGH 6 PM FRIDAY/...
*** ACCUMULATING SNOW POSSIBLE LATE TONIGHT INTO EARLY FRI AFTERNOON 
  ACROSS EASTERN MA FROM CAPE ANN TO BOSTON TO CAPE COD ***

AS MENTIONED IN THE NEAR TERM SECTION...LOW PRESSURE OFF OF NORTH 
CAROLINA WILL MOVE NORTHEASTWARD...PASSING WELL OUTSIDE THE 
BENCHMARK.  HOWEVER...AN INVERTED TROUGH WILL DEVELOP AS THE 
SHORTWAVE CROSSES SOUTHERN NEW ENGLAND. THESE TWO FEATURES WILL 
PROVIDE ENOUGH LIFT AND INSTABILITY ALONG THE EAST COAST OF NEW 
ENGLAND TO PRODUCE A NARROW BAND OF RAIN/SNOW SHOWERS.  THE MAIN 
QUESTION IS JUST WHERE DOES THIS TROUGH SET UP AND HOW CLOSE TO THE 
COAST DOES IT GET.

THESE FEATURES LEAVE A LOT OF UNCERTAINTY AS A SHIFT OF 10 TO 20 
MILES TO THE EAST WILL LEAVE MOST AREAS WITHOUT SNOW.  HOWEVER... 
MODELS HAVE CONSISTENTLY BEEN FORECASTING UP TO HALF AN INCH OF QPF 
ALONG THE EAST COAST OF MASSACHUSETTS TO JUST OFF THE COAST FOR THE 
LAST THREE MODEL RUNS. THAT LENDS SOME LEVEL OF CERTAINTY TO THE 
POTENTIAL FOR A QUICK FEW INCHES OF SNOW.  IN ADDITION...STEEP LOW 
LEVEL LAPSE RATES AND TOTAL TOTALS OVER 50 BOTH INDICATE PLENTY OF 
INSTABILITY THAT WILL BE REALIZED.

AT THIS POINT...GENERALLY HAVE SNOWFALL TOTALS JUST UNDER ADVISORY 
CRITERIA /3 INCHES/. HOWEVER...THERE ARE A FEW POCKETS OF AROUND 3 
INCHES RIGHT AROUND THE BOSTON AREA.  DUE TO THE POTENTIAL FOR A 
CHANGE IN AMOUNTS IF HIGHEST QPF ENDS UP OVER LAND RATHER THAN OVER 
THE OCEAN...AM OPTING TO ISSUE A WINTER WEATHER ADVISORY ALONG THE 
IMMEDIATE EAST COAST FROM CAPE ANN SOUTH THROUGH COASTAL PLYMOUTH 
COUNTY.  EXPECT SNOW TO BEGIN SHORTLY AFTER MIDNIGHT AND CONTINUE 
THROUGH THE MORNING HOURS ON FRIDAY.  WHILE THERE IS QUITE A BIT OF 
UNCERTAINTY WITH THESE SYSTEMS...GIVEN THE NUMBER OF SHOPPERS AND 
TRAVELERS WHO MAY BE OUT AND ABOUT FRIDAY MORNING...FELT AN ADVISORY 
WOULD BE A GOOD IDEA.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
BIG PICTURE... ZONAL FLOW THIS WEEKEND WITH 500 MB HEIGHTS BUILDING 
OVER NEW ENGLAND WHILE A SHORTWAVE TROUGH DROPS THROUGH WESTERN 
CANADA INTO THE PACIFIC NORTHWEST. THE SHORTWAVE THEN RACES EAST TO 
CROSS NEW ENGLAND MONDAY NIGHT. ANOTEHR SHORTWAVE RACES EAST ACROSS 
THE NORTHERN TIER DURING THE WEEK.  THERE ARE DIFFERENCES BETWEEN 
THE ECMWF AND GFS REGARDING THE AMPLITUDE AND SPEED OF THIS 
SHORTWAVE WITH THE GFS FASTER/LESS AMPLIFIED. 

WE FAVOR A MODEL BLEND FOR MOST OF THE LONG TERM.  MOVEMENT OF 
SHORTWAVES THROUGH ZONAL FLOW LEADS TO QUESTIONS ON TIMING SO 
CONFIDENCE IS AT BEST MODERATE. LATE IN THE LONG TERM WE TEND CLOSER 
TOWARD THE ECMWF. AS NOTED BY HPC...THE GREATER AMPLITUDE TROUGH 
SHOWN BY THE ECMWF IS MORE REASONABLE DUE TO DEEP LOW PRESSURE IN 
THE BERING SEA AND RESULTING BUILDING OF A RIDGE ALONG THE PACIFIC 
COAST.

THE DAILIES... 

FRIDAY NIGHT-SATURDAY... HIGH PRESSURE BUILDS OVER NEW ENGLAND WITH 
DRY CHILLY WEATHER. CROSS SECTIONS SHOW INCREASING MID AND HIGH 
LEVEL MOISTURE SATURDAY AS THE HIGH SHIFTS EAST AND WARMER AIR 
STARTS MOVING IN OVER THE TOP OF THE COLDER AIR. SO WE EXPECT MOSTLY 
CLEAR SKIES FRIDAY NIGHT AND INCREASING SKY COVER ON SATURDAY. WE 
STAYED CLOSE TO A COMPOSITE OF GUIDENCE FOR TEMPS BOTH PERIODS.

SATURDAY NIGHT THROUGH MONDAY... A WARM FRONT APPROACHES SATURDAY 
NIGHT. THIS WILL MAINTAIN CLOUDS OVER THE REGION. LOW LEVEL PROFILES 
LOOK RATHER DRY AND LIFT IS WEAK. SO ANY PCPN SHOULD BE LIMITED. WE 
SHOWED SLIGHT CHANCE POPS MAINLY ALONG AND NORTH OF THE MASS PIKE 
SATURDAY NIGHT AND IN SRN NH SUNDAY MORNING. THE WARM FRONT LIFTS 
NORTH ON SUNDAY ALLOWING FOR MILDER TEMPS AND DEWPOINTS AS WELL AS A 
GENERALLY DRY DAY.

THE MODELS SHOW DIFFERENCES IN TIMING THE PASSAGE OF THE COLD FRONT. 
THIS IS NOT A SURPRISE AS WE WILL BE IN A ZONAL FLOW. THE GFS IS 
FASTEST WITH PASSAGE MONDAY MORNING. THE ECMWF IS SLOWER WITH 
PASSAGE MONDAY EVENING. WE USED A BLEND OF THIS DATA WITH CHANCE 
POPS IN THE WEST IN THE MORNING...SLIGHT CHANCE ALL AREAS AFTN...AND 
CHANCE ALL AREAS EARLY MONDAY NIGHT. AT BEST MODERATE CONFIDENCE IN 
THIS TIMING.

TUESDAY... HIGH PRESSURE BUILDS OVER THE REGION WITH COLDER AIR. 
MIXING WILL BE LIMITED TO 925 OR 950 MB...AND TEMPS AT THAT LEVEL 
SUPPORT MAX TEMPS IN THE UPPER 20S AND 30S.

WEDNESDAY-THURSDAY... SHORTWAVE MOVES OUT OF THE PACIFIC NORTHWEST 
AND PUSHES A COLD FRONT ACROSS THE NORTHERN TIER OF STATES TUESDAY-
WEDNESDAY. THIS WILL DRAW A SOUTHWEST LOW LEVEL JET OF 40-45 KNOTS 
LEADING THE COLD FRONT UP TO OUR AREA BY WEDNESDAY. 

THIS JET WILL SUPPLY MOISTURE AND GENERATE SUFFICIENT LIFT FOR 
CLOUDS AND A CHANCE OF PCPN. CONFIDENCE IN TIMING IS LOW BUT AS 
NOTED ABOVE WE FAVORED THE TIMING SHOWN BY THE ECMWF FOR ONSET OF 
CLOUDS AND ANY PCPN. LOW LEVEL TEMPERATURES WILL DETERMIN PCPN 
TYPE...BUT TREND SHOULD BE FROM SNOW TO RAIN EARLY WEDNESDAY AND 
WEDNESDAY MORNING. LINGERING COLD AIR AT THE SURFACE MAY SUPPORT A 
PERIOD OF SLEET OR FREEZING RAIN DURING THE TRANSITION DURING THE 
MORNING...THEN TEMPS SHOULD BE WARM ENOUGH FOR PCPN TO FALL AS RAIN 
ANY OTHER TIME OF THE DAY. TIMING OF THE COLD FRONT PER THE ECMWF 
WOULD BE LATE WEDNESDAY OR EARLY WEDNESDAY NIGHT. 

HIGH PRESSURE BRINGS DRIER WEATHER ON THURSDAY.

&&

.AVIATION /21Z THURSDAY THROUGH TUESDAY/...
FORECASTER CONFIDENCE LEVELS...

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

.SHORT TERM /THROUGH FRIDAY/...MODERATE CONFIDENCE.

THROUGH 00Z...A MIX OF CIGS ACROSS THE AREA THOUGH MOSTLY
VFR/MVFR. IFR CIGS ON THE OUTER CAPE. -SHSN MOVE INTO SOUTHERN NEW
ENGLAND FROM NYS THROUGH THE AFTERNOON.

TONIGHT...MVFR CIGS MOVE ACROSS THE REGION. PRECIP DEVELOPS ACROSS
E MA INTO RI...POSSIBLY AS FAR W AS KORH-KIJD...AS INVERTED
TROUGH TAKES SHAPE NEAR THE COAST AFTER 06Z. AREAS OF MVFR-IFR
VSBYS DEVELOP IN RAIN AND/OR SNOW. VSBYS SHOULD REMAIN MAINLY VFR
ACROSS CENTRAL AND WESTERN AREAS...THOUGH PATCHY FOG MAY FORM LATE
AT NIGHT.

FRIDAY...SNOW/RAIN SHOWERS WILL CONTINUE THROUGH MID-MORNING ALONG
THE E COAST OF MASS...POSSIBLY AS FAR INLAND AS ORH-IJD. PRECIP
COMES TO AN END AFTER NOON AND CONDITIONS WILL IMPROVE TO VFR BY
FRIDAY EVENING.

KBOS TERMINAL...HIGH CONFIDENCE TODAY...LOWER CONFIDENCE TONIGHT IN
EXACT TIMING AS PRECIP DEVELOPS.

KBDL TERMINAL...HIGH CONFIDENCE.

OUTLOOK...FRIDAY NIGHT THROUGH TUESDAY...MODERATE CONFIDENCE

FRIDAY NIGHT AND SATURDAY...VFR. INCREASING SKY COVER SATURDAY. 
NORTHWEST WINDS BECOME SOUTHWEST BUT REMAIN LIGHT.

SATURDAY NIGHT-SUNDAY...LOWERING CLOUDS SATURDAY NIGHT WITH 
POTENTIAL FOR MVFR CIGS/VSBYS IN WIDELY SCATTERED PCPN LATE AT NIGHT 
AND SUNDAY MORNING. LOW LEVEL WINDS...AROUND 2000 FEET...WILL 
INCREASE OVERNIGHT AND SUNDAY TO 40-45 KNOTS AND MAY CREATE LOW 
LEVEL WIND SHEAR.

MONDAY...VFR WITH SCATTERED SHOWERS AS A COLD FRONT MOVES THROUGH. 
SOUTHWEST WINDS AHEAD OF THE COLD FRONT WILL SWITCH TO NORTHWEST 
AFTER THE FRONT MOVES THROUGH.

TUESDAY...VFR WITH NORTH TO NORTHEAST WINDS.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

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

SEAS DIMINISH SLOWLY TONIGHT BEFORE INCREASING AGAIN AS INVERTED 
TROUGH DEVELOPS OVER THE WATERS.  GENERALLY NORTHWESTERLY WINDS 
EXPECTED OVER THE WATERS THOUGH A FEW NORTHEASTERLY WINDS ARE 
POSSIBLE ON THE EASTERN WATERS.  WINDS INCREASE FRIDAY...GUSTING TO 
NEAR 25 KTS.  HAVE SMALL CRAFT ADVISORIES UP FOR MOST OF THE COASTAL 
WATERS FOR EITHER SEAS...GUSTY WINDS OR BOTH.

OUTLOOK...FRIDAY NIGHT THROUGH TUESDAY...MODERATE CONFIDENCE. 

FRIDAY NIGHT...DIMINISHING WINDS AND SEAS. LINGERING 5 FOOT SEAS ON 
THE OUTER WATERS BEFORE MIDNIGHT MAY REQUIRE A SMALL CRAFT ADVISORY.

SATURDAY...WINDS AND SEAS SHOULD REMAIN BELOW SMALL CRAFT THRESHOLDS.

SUNDAY...SOUTHWEST WINDS INCREASE TO 25 KNOTS AND SEAS BUILD TO 5-7 
FEET. A SMALL CRAFT ADVISORY MAY BE NEEDED ON MOST WATERS.

MONDAY...A COLD FRONT MOVES THROUGH DURING THE AFTERNOON OR EVENING. 
SOUTHWEST WINDS SHIFT TO NORTHWEST LATER IN THE DAY...WITH SPEEDS 20 
TO 25 KNOTS. SEAS DIMINISH A LITTLE BUT REMAIN AT OR ABOVE 5 FEET ON 
THE EXPOSED WATERS.  A SMALL CRAFT ADVISORY MAY STILL BE NEEDED.

TUESDAY...NORTH WINDS BECOME NORTHEAST WITH GUSTS AROUND 25 KNOTS. 
SEAS LINGER AT 5 TO 6 FEET ON THE OUTER WATERS.  A SMALL CRAFT 
ADVISORY MAY BE NEEDED.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...WINTER WEATHER ADVISORY FROM 1 AM TO NOON EST FRIDAY FOR 
     MAZ007-015-016-019.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ231-
     232.
     SMALL CRAFT ADVISORY UNTIL 6 PM EST FRIDAY FOR ANZ235-237-250-
     251-254>256.

&&

$$
SYNOPSIS...WTB/RLG
NEAR TERM...RLG
SHORT TERM...RLG
LONG TERM...WTB
AVIATION...WTB/RLG
MARINE...WTB/RLG



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