749  
FXUS61 KBOX 100939  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
439 AM EST MON DEC 10 2018  
   
SYNOPSIS
 
 
ANOTHER COLD STRETCH OF WEATHER MUCH OF THIS WEEK AS  
TEMPERATURES CONTINUE TO AVERAGE COLDER THAN NORMAL THROUGH THU  
WITH THE COLDEST AIR WED AND THU. MAINLY DRY WEATHER PREVAILS  
AS WELL WITH THE EXCEPTION BEING POTENTIAL SCATTERED SNOW  
SHOWERS OR FLURRIES LATE TUE NIGHT INTO WED FOLLOWED BY OCEAN  
EFFECT SNOW SHOWERS WED AFTERNOON AND NIGHT ACROSS THE OUTER  
CAPE. TEMPERATURES MODERATE FRIDAY AHEAD OF AN APPROACHING COLD  
FRONT THAT MAY RESULT IN RAIN FRIDAY NIGHT INTO SATURDAY.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
WINDS HAVE SHIFTED TO N-NW EARLY THIS MORNING AS A DRY, WEAK  
TROUGH PUSHED ACROSS EARLIER THIS MORNING. THE VEIL OF HIGH  
CLOUDS AS SEEN ON SATELLITE IMAGERY SINCE LAST EVENING HAS  
PUSHED OFFSHORE, THOUGH SOME SOME BANDS LINGERING ACROSS N  
CT/RI/SE MASS. ALSO, THE LOWER CLOUDS ACROSS W MASS HAVE ALSO  
DISSIPATED, EXCEPT FOR SOME LINGERING CLOUDS FROM NEAR KBAF-  
KBDL. STILL SEE A BANK OF LOWER CLOUDS ACROSS S NH/S VT INTO  
THE HUDSON VALLEY. COULD SEE SOME OF THESE CLOUDS MOVE INTO  
WESTERN AREAS THIS MORNING.  
 
WITH LIGHT NORTHERLY OR CALM WINDS, TEMPS HAVE FALLING TO THE  
MID TEENS TO NEAR 20 INLAND, RANGING TO THE LOWER 30S ACROSS THE  
MID AND OUTER CAPE AND ON THE ISLANDS AT 09Z. SHOULD SEE  
READINGS FALL A FEW MORE DEGREES BEFORE DAYBREAK.  
 
TODAY...  
 
HIGH PRESSURE ACROSS QUEBEC WILL SHIFT SE INTO N NH AND W MAINE  
TODAY AS ANOTHER COLD FRONT WORKS S THROUGH MIDDAY TODAY. THIS  
FRONT WILL SLOW ACROSS RI/SE MASS AS THE STRONG WINTER STORM  
THAT AFFECTED THE SOUTHERN TIER SLOWLY PUSHES OFFSHORE. WILL SEE  
SKIES BECOME MOSTLY SUNNY ACROSS MOST AREAS BUT IT WILL REMAIN  
CHILLY. HIGHS WILL ONLY REACH THE 30S.  
 
HOWEVER, WITH COLD, NORTHERLY WINDS IN PLACE ACROSS THE MILDER  
WATERS OFF THE E COAST, WILL LIKELY SEE OCEAN ENHANCED CLOUDS  
DEVELOP THIS MORNING AND LINGER THROUGH THE DAY. WITH MODEST  
INSTABILITY IN PLACE ACROSS THE WATERS, MAY EVEN SEE SOME OCEAN  
EFFECT RAIN/SNOW SHOWERS DEVELOP. SEVERAL OF THE HIGH RES SHORT  
RANGE MODELS HAVE SIGNALED THAT SOME PRECIP MAY DEVELOP JUST E  
OF THE OUTER ARM OF THE CAPE, BUT CAN'T RULE OUT SOME LIGHT  
PRECIP REACH PORTIONS OF THE OUTER CAPE AND NANTUCKET AROUND  
MIDDAY OR THIS AFTERNOON.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/
 
 
TONIGHT...  
 
THE NORTHERLY WINDS WILL LINGER ACROSS THE MID AND OUTER CAPE  
AS WELL AS NANTUCKET THROUGH AROUND MIDNIGHT, SO COULD SEE THE  
OCEAN ENHANCED CLOUDS LINGER AS WELL. OTHERWISE, HIGH PRESSURE  
REMAINS IN CONTROL WITH A FRIGID NIGHT IN STORE. EXPECT  
OVERNIGHT LOWS TO RANGE FROM AROUND 10-15 DEGREES ACROSS THE  
INTERIOR, RANGING TO THE 20S ALONG THE IMMEDIATE COAST.  
 
TUESDAY...  
 
A DRY, NEARLY ZONAL MID LEVEL STEERING FLOW CONTINUES FOR  
TUESDAY. CLOUDS WILL LINGER ACROSS THE MID AND OUTER CAPE,  
OTHERWISE ANOTHER MOSTLY SUNNY AND COLD DAY ELSEWHERE. HIGHS  
WILL RANGE FROM THE UPPER 20S TO AROUND 30 ACROSS THE HIGHER  
TERRAIN TO THE UPPER 30S ALONG THE S COAST.  
 
HOWEVER, NOTING THE FLOW BEGINNING TO BACK TO W-SW AS A CLIPPER  
TYPE SYSTEM RIDES SE OUT OF THE GREAT LAKES. LOOKS LIKE THIS  
SYSTEM WILL REMAIN W OF THE REGION THROUGH TUESDAY.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/
 
 
335 AM UPDATE...  
 
HIGHLIGHTS...  
 
* NOTICEABLY COLDER WED & THU AND BLUSTERY WED AFTERNOON/EVENING  
* OCEAN EFFECT SNOW SHOWERS OUTER CAPE COD WED AFTERNOON & NIGHT  
* MILDER FRI/SAT/SUN WITH THREAT OF RAIN FRI NIGHT/SAT  
 
TUESDAY NIGHT INTO WEDNESDAY MORNING...  
 
OFFSHORE LOW TRACKING WELL SOUTHEAST OF THE 40N/70W BENCHMARK  
TUE EVENING, HOWEVER AN UPSTREAM STRONG NORTHERN STREAM SHORT  
WAVE EXITS THE GREAT LAKES AND ONTARIO, TRACKING EAST INTO NEW  
ENGLAND. THIS HIGH AMPLITUDE SHORT WAVE INDUCES AN INVERTED  
TROUGH FROM THE OFFSHORE CYCLONE WESTWARD INTO NEW ENGLAND,  
INDICATIVE OF STRONG FORCING FOR ASCENT. HOWEVER LIMITING FACTOR  
IS SHORT DURATION OF ATTENDING MID LEVEL MOISTURE. INSPECTION  
OF TIME SECTIONS FROM BOTH NAM AND GFS BUFKIT REVEAL COLUMN  
STRUGGLES TO SATURATE INCLUDING THE DGZ (-10C TO -20C). THIS  
SHOULD LIMIT PRECIP TO WIDELY SCATTERED SNOW SHOWERS OR JUST  
FLURRIES. CHILLY DAY WITH 850 TEMPS AROUND -12C WITH MODEL  
SOUNDINGS SHOWING MIXING ALMOST TO THIS LAYER.  
 
WEDNESDAY EVENING AND OVERNIGHT...  
 
STRONG CAA BEHIND DEPARTING NORTHERN STREAM SHORT WAVE. 850 MB  
TEMPS LOWER TO -12C TO -14C AND 925 MB TEMPS -10C TO -12C ACROSS  
THE REGION. SO HIGHS ONLY 30-35 WED AFTN EXPECTED BUT WILL FEEL  
CONSIDERABLY COLDER WITH GUSTY NORTH WINDS 15-25 MPH PROVIDING  
WIND CHILLS IN THE 20S. THESE GUSTY NORTH WINDS ADVECTING A COLD  
AIRMASS OVER THE RELATIVELY WARM OCEAN WATERS WILL GENERATE  
OCEAN EFFECT SNOWS (OES) FROM ABOUT HYANNIS EASTWARD. GIVEN SSTS  
NEAR SHORE STILL RELATIVELY WARM AROUND +6C TO +7C, THIS WILL  
SUPPORT STEEP LOW LEVEL LAPSE RATES WITH DELTA-T ON THE ORDER OF  
APPROACHING 20 DEGS. THIS TYPICALLY IS THE INSTABILITY  
THRESHOLD FOR THE BEGINNING OF ACCUMULATING OCEAN EFFECT SNOWS.  
NAM BUFKIT AT CHH HAS OCEAN INDUCED CAPES UP TO 700 J/KG WITH  
NORMALIZED CAPE GREATER THAN 0.20 INCHES. THIS SHOULD BE  
SUFFICIENT FOR MINOR SNOW ACCUMULATIONS, SAY A COATING TO  
PERHAPS UP TO 2 INCHES IN A FEW LOCATIONS. WINDS DROP OFF AFTER  
MIDNIGHT SO SHOULD SEE SOME IMPROVEMENT THEN. COLD NIGHT AS 1034  
MB HIGH CREST OVER THE REGION. THUS IDEAL RADIATIONAL COOLING  
AND WILL FOLLOW THE COLDEST GUIDANCE ACCORDINGLY.  
 
THURSDAY...  
 
NOT AS WINDY AS WED AS 1034 MB HIGH CREST OVER THE REGION.  
THEREFORE LIGHT WINDS. HOWEVER SUBSIDENCE INVERSION WILL  
PRECLUDE COLD MORNING TEMPS FROM MODIFYING MUCH. THUS A CHILLY  
THU. DRY WEATHER PREVAILS.  
 
FRIDAY, SATURDAY AND SUNDAY...  
 
MILDER TEMPS FRI AS NORTHERN STREAM JET LIFTS NORTHWARD AND  
HIGH PRES MOVES OFFSHORE, PROMOTING ONSHORE FLOW INTO SOUTHERN  
NEW ENGLAND. SEASONABLY WARM WITH HIGHS IN THE 40S FRI.  
THEREAFTER FORECAST BECOMES HIGHLY UNCERTAIN FROM FRI NIGHT INTO  
SUNDAY. ENSEMBLES AND DETERMINISTIC GUIDANCE HAVE ALL TRENDED  
AWAY FROM STREAMS MERGING WITH NOW AN UNPHASED SCENARIO THIS  
PERIOD ALONG WITH SOUTHERN STREAM BEING MORE DOMINANT. HOWEVER  
INDIVIDUAL MEMBERS FROM BOTH THE 00Z GEFS AND EPS REALLY EXHIBIT  
LARGE SPREAD WITH MANY MEMBERS DRY THIS WEEKEND WHILE OTHER  
MEMBERS ARE VERY WET. THUS HIGHLY UNCERTAIN WEEKEND FORECAST.  
 

 
   
AVIATION /10Z MONDAY THROUGH FRIDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH TUESDAY/...HIGH CONFIDENCE.  
 
THROUGH 12Z...  
VFR CONDITIONS. MOSTLY CLEAR SKIES, EXCEPT BKN-OVC CLOUDS AT  
3000- 3500 ACROSS THE CT VALLEY TERMINALS.  
 
TODAY...  
VFR. CONDITIONS IMPROVE ACROSS THE CT VALLEY. SCT-BKN CLOUDS  
DEVELOP ACROSS CAPE COD AND THE ISLANDS THIS MORNING. SOME MVFR  
CIGS LOWER TO AROUND 2500 FT MAINLY FROM KHYA-KACK EAST TO THE  
OUTER CAPE THROUGH THE AFTERNOON IN OCEAN ENHANCED CLOUDS. LOW  
RISK OF A FEW RAIN SHOWERS OR SNOW FLURRIES FROM KPVC-KCQX THIS  
AFTERNOON. NORTHERLY WIND GUSTS IN THE LOWER 20 KNOTS ACROSS THE  
OUTER CAPE AND KACK THROUGH MIDDAY OR EARLY AFTERNOON.  
 
TONIGHT AND TUESDAY...  
VFR. CIGS LINGER ACROSS THE MID AND OUTER CAPE/NANTUCKET  
TONIGHT, THEN MAY LINGER ON THE OUTER CAPE INTO TUESDAY. N  
WINDS TONIGHT WILL DIMINISH AS THEY SHIFT TO E-SE EARLY TUE,  
THEN LIGHT W-SW BY MIDDAY TUE.  
 
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.  
 
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.  
 
OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/...  
 
TUESDAY NIGHT: VFR.  
 
WEDNESDAY THROUGH WEDNESDAY NIGHT: VFR. BREEZY. MVFR IN SNOW  
SHOWERS LIKELY ACROSS THE OUTER CAPE.  
 
THURSDAY: VFR.  
 
THURSDAY NIGHT: MAINLY VFR, WITH LOCAL MVFR POSSIBLE.  
 
FRIDAY: VFR. BREEZY.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH TUESDAY/...HIGH CONFIDENCE.  
 
THROUGH TODAY...  
WINDS AND SEAS HAVE LOWERED BELOW SMALL CRAFT CRITERIA ON THE  
OUTER WATERS SO HAVE ENDED THE SMALL CRAFT HEADLINES.  
 
WINDS HAVE SHIFTED TO N-NW OVER THE LAST FEW HOURS WITH THE  
PASSING COLD FRONT, WHICH WILL LIE ACROSS CAPE COD AND NEAR THE  
S COAST BY LATE THIS MORNING. WITH ANOTHER BATCH OF COLD AIR  
MOVING IN, WILL SEE GUSTS UP TO AROUND 20 KT. MAY SEE A FEW  
BRIEF GUSTS UP TO 25 KT MAINLY ACROSS THE SOUTHERN OUTER WATERS  
THIS AFTERNOON. SEAS 4 FT OR LESS.  
 
OCEAN ENHANCED CLOUDS WILL DEVELOP ACROSS MOST OF THE EASTERN  
WATERS DURING THIS MORNING, WITH THE BEST CHANCE ACROSS PORTIONS  
OF THE MID AND OUTER CAPE, AND CONTINUE THROUGH THIS AFTERNOON  
AS THE NORTHERLY WINDS BRING ANOTHER BATCH OF COLDER AIR. MAY  
SEE SOME BRIEF VISIBILITY RESTRICTIONS E OF CAPE COD IN OCEAN  
EFFECT RAIN AND SNOW SHOWERS AROUND MIDDAY THROUGH THE  
AFTERNOON.  
 
TONIGHT...  
WINDS SLOWLY DIMINISH AS THEY BECOME N-NE. GUSTS UP TO 20 KT  
POSSIBLE ACROSS THE EASTERN OUTER WATERS THIS EVENING. ANY  
LEFTOVER RAIN AND/OR SNOW SHOWERS WILL DISSIPATE THIS EVENING AS  
THE NORTHERLY WINDS DIMINISH. OTHERWISE, GOOD VISIBILITY. SEAS  
AROUND 2 TO 4 FEET AWAY FROM THE COAST.  
 
TUESDAY...  
HIGH PRESSURE MOVES OFFSHORE AS ANOTHER WEAK LOW QUICKLY  
APPROACHES FROM THE W. WINDS DIMINISH AS THEY SHIFT TO S-SW.  
SEAS CONTINUE AT 4 FT OR LESS.  
 
OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/...  
 
TUESDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING  
5 FT. LOCAL VISIBILITY 1 TO 3 NM.  
 
WEDNESDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS  
UP TO 25 KT. LOW RISK OF GALE FORCE NORTHERLY WINDS. SEAS UP TO  
5 FT. CHANCE OF SNOW SHOWERS. VISIBILITY 1 TO 3 NM.  
 
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. LOW RISK OF GALE FORCE  
NORTHERLY WINDS DURING THE EVENING, THEN DIMINISHING AFTER  
MIDNIGHT. AREAS OF ROUGH SEAS. SLIGHT CHANCE OF SNOW SHOWERS.  
LOCAL VISIBILITY 1 TO 3 NM.  
 
THURSDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING  
5 FT.  
 
THURSDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS  
APPROACHING 5 FT. SLIGHT CHANCE OF RAIN SHOWERS. LOCAL  
VISIBILITY 1 TO 3 NM.  
 
FRIDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING 5 FT.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...NONE.  
RI...NONE.  
MARINE...NONE.  
 

 
 

 
SYNOPSIS...NOCERA/EVT  
NEAR TERM...NOCERA/EVT  
SHORT TERM...EVT  
LONG TERM...NOCERA  
AVIATION...NOCERA/EVT  
MARINE...NOCERA/EVT  
 
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