380  
FXUS61 KBOX 112059  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
359 PM EST TUE DEC 11 2018  
   
SYNOPSIS
 
 
MAINLY DRY AND COLD WEATHER PREVAILS INTO THURSDAY, EXCEPT FOR SOME  
SCATTERED OCEAN EFFECT SNOW SHOWERS WEDNESDAY, MAINLY ACROSS  
THE OUTER-CAPE. MILD TEMPERATURES ARRIVE FRIDAY AND CONTINUE  
INTO EARLY NEXT WEEK WITH THE BEST CHANCE FOR RAIN FRIDAY NIGHT  
INTO SATURDAY IN ASSOCIATION WITH LOW PRESSURE.  
 

 
   
NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/
 
 
DRY WEATHER WILL CONTINUE THROUGHOUT THE DAY AS A HIGH PRESSURE  
REMAINS OVER THE REGION. LIGHT VEERING WINDS WITH CLEAR SKIES  
WILL DOMINATE INTO THE EVENING, APART FROM OCEAN EFFECT CLOUDS  
THAT CONTINUE TO LINGER OVER THE OUTER CAPE, AS WELL AS  
NANTUCKET. CLOUDS WILL ALSO INCREASE ALONG THE SOUTH COAST AND  
SE MASS OVERNIGHT AS A TONGUE OF MOISTURE AT 925MB PUSHES  
NORTHEAST.  
 
OVERNIGHT TEMPERATURES WILL BE 5 TO 10 DEGREES BELOW NORMAL  
ONCE AGAIN, WITH AREAS AT HIGHER ELEVATIONS POSSIBLY SEEING LOWS  
INTO THE TEENS.  
 

 
   
SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/
 
 
A SHORTWAVE WILL MOVE SOUTHEAST ACROSS THE REGION OVERNIGHT,  
PROVIDING ENOUGH INSTABILITY FOR OCEAN EFFECT SNOW ALONG THE  
OUTER CAPE TOMORROW MORNING. MODELS SUPPORT OCEAN EFFECT SNOW  
TOMORROW ALONG THE OUTER CAPE. AS WINDS TURN OUT OF THE NNW BY  
12Z TOMORROW, COMBINING WITH THE INSTABILITY AND MOISTURE ALOFT,  
OCEAN EFFECT SEEMS LIKELY AFTER 12Z.  
 
LOOKING AT MODEL SOUNDINGS, IT LOOKS LIKE THE TEMPERATURE  
DIFFERENCE BETWEEN AN INVERSION ALOFT AND THE SEA SURFACE TEMPS  
WILL BE BETWEEN 15C AND 20C, WHICH WILL SUPPORT STRONG SNOW  
SHOWERS DURING THE TIME PERIOD. SNOWFALL ACCUMULATIONS LOOK TO  
BE BETWEEN 1 TO 2 INCHES ALONG THE OUTER CAPE, BUT LESS THAN 1  
INCH IS POSSIBLE INTO FALMOUTH AND SOUTHERN PLYMOUTH COUNTY.  
 
ELSEWHERE ACROSS THE REGION WILL BE MOSTLY SUNNY AND DRY.  
 
SNOW WILL LIKELY LAST THROUGHOUT THE DAY, HOWEVER, SOME MODELS  
ARE SHOWING POCKETS OF DRY AIR MOVING IN ALOFT AFTER 18Z, WHICH  
MAY CUT OFF THE SNOW SHOWERS EARLIER THAN EXPECTED.  
 
A STRONG HIGH PRESSURE BUILDS INTO THE NORTHEAST WEDNESDAY  
NIGHT. WITH MOSTLY CLEAR SKIES AND LIGHT NORTHERLY WINDS,  
OVERNIGHT TEMPERATURES WILL BE MORE THAN 10 DEGREES BELOW  
NORMAL. NORTHERN MASSACHUSETTS COULD SEE LOWS IN THE SINGLE  
DIGITS.  
 

 
   
LONG TERM /THURSDAY THROUGH TUESDAY/
 
 
HIGHLIGHTS...  
 
* DRY BUT COLD THURSDAY  
* MILDER FRIDAY WITH A PERIOD RAIN FOCUSED FRI NIGHT INTO SAT  
* LOW CONFIDENCE FORECAST EARLY NEXT WEEK  
 
DETAILS...  
 
THURSDAY...  
 
HIGH PRESSURE OVERHEAD WILL RESULT IN MOSTLY SUNNY SKIES BUT ANOTHER  
COLD DAY. AFTER A VERY COLD START...LIGHT WINDS AND THE LOW  
DECEMBER SUN ANGLE WILL ONLY ALLOW AFTERNOON HIGH TEMPERATURES TO  
RECOVER INTO THE LOWER TO MIDDLE 30S.  
 
THURSDAY NIGHT...  
 
DRY WEATHER SHOULD PREVAIL...BUT WE MAY SEE SOME MID LEVEL  
CLOUDINESS OVERSPREAD PARTS OF THE REGION OVERNIGHT. THIS A RESULT  
OF HIGH PRESSURE MOVING OFF THE COAST AND WARM ADVECTION ALOFT.  
STILL EXPECT TO SEE LOW TEMPS BOTTOM OUT MAINLY IN THE UPPER TEENS  
TO LOWER 20S WITH RATHER LIGHT WINDS.  
 
FRIDAY INTO EARLY NEXT WEEK...  
 
A PATTERN CHANGE TO MILDER WEATHER EXPECTED AS AN ACTIVE PACIFIC JET  
FLUSHES OUT THE COLD WEATHER WE HAVE EXPERIENCED OVER MUCH OF THE  
LAST MONTH. GIVEN THE PATTERN TRANSITION AND ACTIVE SUB-TROPICAL  
JET...THE FORECAST GOING FORWARD REMAINS LOW CONFIDENCE INTO EARLY  
NEXT WEEK.  
 
WE DO THINK THAT WARM ADVECTION AHEAD OF SOUTHERN STREAM ENERGY WILL  
RESULT IN A PERIOD OF RAIN...FOCUSED FRIDAY NIGHT INTO SATURDAY.  
A LOW RISK FOR A PERIOD OF FREEZING RAIN AT THE ONSET CAN NOT BE  
RULED OUT...BUT GENERALLY EXPECTING A RAIN EVENT.  
 
THE OTHER BIG ISSUE IS THE TRACK/TIMING OF THE SURFACE LOW. THIS  
WILL ALL COME DOWN TO THE LOCATION/STRENGTH OF BOTH THE NORTHERN AND  
SOUTHERN STREAM ENERGY. IF THE SOUTHERN STREAM ENERGY GETS PULLED  
NORTHWARD, PRECIPITATION CHANCES WOULD CONTINUE INTO SUNDAY AND/OR  
MONDAY...BUT IF IT GETS SHUNTED SOUTH OUR REGION WILL MAINLY BE DRY.  
IF WE DO SEE PRECIPITATION SUN INTO MON...PTYPE WOULD FAVOR RAIN  
GIVEN THE OVERALL MILDER REGIME. HOWEVER...A LOW RISK FOR SOME  
WINTRY PRECIPITATION CAN NOT BE COMPLETELY RULED OUT. THE STORM  
WOULD HAVE TO TRACK NEAR THE BENCHMARK AND WOULD ALSO REQUIRE ENOUGH  
MARGINALLY COLD AIR TO WORK DOWN FROM THE NORTH.  
 

 
   
AVIATION /21Z TUESDAY THROUGH SUNDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH WEDNESDAY NIGHT/...HIGH CONFIDENCE.  
 
OVERALL VFR. EXCEPTION IS CAPE AND ISLANDS, AS WELL AS PORTIONS  
OF SOUTHEAST MA AS SCT-BKN -SN IS FORECAST WEDNESDAY WITH SCT-  
BKN LOW-END VFR TO MVFR CIGS. POTENTIAL VSBY ISSUES DOWN TO IFR  
WITH -SN. WITH -SN, WINDS SHIFTING N / NW, BECOMING BREEZY WITH  
POTENTIAL GUSTS UP AROUND 20 KTS LATE.  
 
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.  
 
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.  
 
OUTLOOK /THURSDAY THROUGH SUNDAY/...  
 
THURSDAY THROUGH THURSDAY NIGHT: VFR.  
 
FRIDAY: MAINLY VFR, WITH AREAS MVFR POSSIBLE. BREEZY. CHANCE  
RA.  
 
FRIDAY NIGHT: MAINLY MVFR, WITH LOCAL IFR POSSIBLE. BREEZY. RA.  
 
SATURDAY: MAINLY MVFR, WITH LOCAL IFR POSSIBLE. RA LIKELY.  
 
SATURDAY NIGHT: MAINLY MVFR, WITH LOCAL IFR POSSIBLE. WINDY  
WITH AREAS GUSTS TO 30 KT. CHANCE RA.  
 
SUNDAY: MAINLY MVFR, WITH LOCAL IFR POSSIBLE. WINDY WITH LOCAL  
GUSTS TO 30 KT. CHANCE RA.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH WEDNESDAY NIGHT/...HIGH CONFIDENCE.  
 
RATHER TRANQUIL BOATING CONDITIONS THROUGH THIS EVENING WITH  
GOOD VISIBILITY. NORTHERLY FLOW INCREASES ACROSS THE WATERS  
LATE TONIGHT INTO WEDNESDAY. ROUGH SEAS EXPECTED TO DEVELOP  
ACROSS THE OUTER COASTAL WATERS AS A RESULT. A SMALL CRAFT  
ADVISORY HAS BEEN ISSUED FOR THE WATERS ALONG THE CAPE DUE TO  
HIGH SEAS AND STRONG GUSTING WINDS. IN ADDITION TO THE WINDS,  
OCEAN- EFFECT SNOW SHOWERS MAY REDUCE VISIBILITY AT TIMES TO  
LESS THAN 3 NM LATE TONIGHT INTO WEDNESDAY ACROSS THE EASTERN  
COASTAL WATERS.  
 
OUTLOOK /THURSDAY THROUGH SUNDAY/...  
 
THURSDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING  
5 FT.  
 
THURSDAY NIGHT: WINDS LESS THAN 25 KT.  
 
FRIDAY: WINDS LESS THAN 25 KT. CHANCE OF RAIN.  
 
FRIDAY NIGHT: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH  
GUSTS UP TO 30 KT. SEAS LOCALLY APPROACHING 5 FT. RAIN.  
 
SATURDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS UP  
TO 25 KT. AREAS OF SEAS APPROACHING 5 FT. RAIN LIKELY.  
 
SATURDAY NIGHT: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS  
WITH LOCAL GUSTS UP TO 30 KT. ROUGH SEAS UP TO 11 FT. CHANCE OF  
RAIN.  
 
SUNDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH LOCAL  
GUSTS UP TO 30 KT. ROUGH SEAS UP TO 12 FT. CHANCE OF RAIN.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...NONE.  
RI...NONE.  
MARINE...SMALL CRAFT ADVISORY FROM NOON WEDNESDAY TO 1 PM EST  
THURSDAY FOR ANZ250-254-255.  
 

 
 

 
SYNOPSIS...CORREIA/FRANK  
NEAR TERM...CORREIA  
SHORT TERM...CORREIA  
LONG TERM...FRANK  
AVIATION...CORREIA/FRANK  
MARINE...CORREIA/FRANK  
 
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