313  
FXUS61 KBOX 181928  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
328 PM EDT WED SEP 18 2019  
   
SYNOPSIS
 
 
HIGH PRESSURE BUILDS OVER NEW ENGLAND TONIGHT AND LINGERS OVER  
THE REGION THROUGH EARLY NEXT WEEK. BELOW-NORMAL TEMPERATURES  
LATE THIS WEEK WILL TREND TO ABOVE-NORMAL TEMPERATURES OVER THE  
WEEKEND AND EARLY NEXT WEEK. A COLD FRONT BRINGS THE NEXT CHANCE  
OF SHOWERS EARLY NEXT WEEK. DISTANT HURRICANE HUMBERTO WILL  
BRING HIGH SURF AND DANGEROUS RIP CURRENTS LATE THIS WEEK, WHICH  
SHOULD PEAK ON FRIDAY.  
 

 
   
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
 
 
CLOUDS DIMINISH THIS EVENING WITH CLEAR SKIES MOST OF THE NIGHT.  
HIGH PRESSURE MOVES OVER THE REGION TONIGHT, BRINGING LIGHT WIND  
TO THE INTERIOR AND RESULTING RADIATIONAL COOLING. NORTHEAST  
WINDS LINGER ALONG THE CAPE AND ISLANDS WITH GUSTS TO 25 KT  
POSSIBLE.  
 
OBSERVED DEW POINTS AT 3 PM WERE 37 TO 45. RADIATIONAL COOLING  
MAY PUSH THESE VALUES A COUPLE OF DEGREES LOWER. OUR MIN TEMP  
FORECASTS RANGE FROM THE MID 30S TO AROUND 40 INLAND AND 40 TO  
50 ALONG THE COAST.  
 
THE FROST ADVISORY FOR TONIGHT WILL BE EXPANDED TO INCLUDE  
NORTHERN WORCESTER CO AND WESTERN HAMPDEN CO. THE FROST PERIOD  
WILL BE AFTER MIDNIGHT UNTIL AFTER SUNRISE.  
 
SWELL FROM HUMBERTO CONTINUES TO ARRIVE AND INCREASE. WE WILL  
CONTINUE THE RIP CURRENT RISK STATEMENT THROUGH MIDNIGHT, AT  
WHICH TIME WE WILL MOVE TO A HIGH SURF ADVISORY FOR THE SOUTH  
COAST.  
 

 
   
SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/
 
 
HIGH PRESSURE REMAINS IN PLACE THURSDAY AND THURSDAY NIGHT.  
EXPECT MOSTLY CLEAR SKIES AND LIGHT WIND THROUGH THE PERIOD.  
MIXING IS FORECAST TO 925 MB, WHERE TEMPERATURES OF 11-13C  
SUPPORT MAX TEMPS OF MID 60S TO AROUND 70.  
 
EAST-SOUTHEAST SWELL TO 7 FEET FROM HUMBERTO REMAINS ALONG OUR  
SOUTH COAST. THIS WILL CONTINUE TO GENERATE HIGH RIP CURRENT  
RISK AS WELL AS HIGH SURF. WILL CONTINUE THE HIGH SURF ADVISORY  
THROUGH THE DAY. THE SWELL EXPANDS UP THE EAST COAST OF MASS  
THURSDAY NIGHT, AT WHICH TIME THE ADVISORY WILL ALSO EXPAND UP  
THE SOUTH SHORE AND NORTH SHORE.  
 

 
   
LONG TERM /FRIDAY THROUGH WEDNESDAY/
 
 
HIGHLIGHTS...  
 
* HIGH SURF AND BUILDING SEAS FROM HUMBERTO ON COASTAL WATERS  
FRIDAY, HIGHEST EAST. SUBSIDING TREND LATE FRIDAY.  
 
* DRY PATTERN THROUGH THE WEEKEND WITH ABOVE- TO SIGNIFICANTLY ABOVE  
NORMAL TEMPERATURES.  
 
* COLD FRONT EARLY NEXT WEEK OFFERS NEXT CHANCES FOR RAIN.  
 
DETAILS...  
 
AMPLIFIED MID AND UPPER LEVEL RIDGE ALOFT TO BUILD AND CREST ACROSS  
MUCH OF NEW ENGLAND THROUGH THE WEEKEND, WITH SURFACE RIDGE TO  
REMAIN ESTABLISHED ACROSS THE REGION. PLENTY OF SUN WITH SIZABLE  
DIURNAL TEMPERATURE RANGES SHOULD BE EXPECTED FRIDAY THROUGH THE  
WEEKEND. 850 MB TEMPERATURES INCREASING TO THE LOW TO MID TEENS  
CELSIUS RANGE SUPPORTS HIGH TEMPERATURES INTO THE LOW TO MID 80S  
FRIDAY THRU SUNDAY ACROSS THE INTERIOR INTO THE COASTAL PLAIN, INTO  
THE MID 70S ALONG THE COASTS. THESE ARE SOME 10-15 DEGREES WARMER  
THAN LATE-SEPTEMBER CLIMATOLOGY. LOWS MAINLY IN THE 50S. DEWPOINTS  
WILL ALSO BE SLOWLY ON THE RISE EACH AFTERNOON, ALBEIT STILL AT  
COMFORTABLE LEVELS HUMIDITY-WISE. OVERALL, SHAPING UP TO BE AN  
OUTSTANDING CLOSE TO THE WEEK INTO THE WEEKEND WEATHER-WISE.  
 
WITH THE ABOVE SAID HOWEVER, WITH THE POTENTIAL FOR MANY TO HEAD TO  
THE BEACHES/COASTS TO TAKE ADVANTAGE OF THE NICE STRETCH OF WEATHER  
AHEAD...CONCERNS CONTINUE FOR FRIDAY REGARDING THE THREAT FOR HIGH  
SURF AND RIP CURRENTS IN THE COASTAL ZONE, AND FOR BUILDING SEAS IN  
THE OUTER WATERS. WHILE HUMBERTO WILL PASS WELL SOUTH OF NANTUCKET  
LATE THURSDAY INTO EARLY FRIDAY, SWELL FROM HUMBERTO'S CIRCULATION  
WILL CAUSE WAVES TO RISE CONSIDERABLY ON THE OUTER WATERS (TO AROUND  
8-10 FEET) AND CONTRIBUTE TO HIGH SURF AND A CONTINUED THREAT OF RIP  
CURRENTS. ESPECIALLY AS WE'RE NOW PROGRESSING INTO THE OFF-SEASON,  
BEACHGOERS SHOULD WATCH THE BUILDING SURF FROM A SAFE DISTANCE WITH  
SWIMMING NOT RECOMMENDED. SEAS WILL EVENTUALLY SUBSIDE AS WE MOVE  
INTO LATE FRIDAY INTO FRIDAY NIGHT.  
 
MONDAY INTO TUESDAY...  
 
COLD FRONT OVER THE LOWER GREAT LAKES LOOKS TO PROGRESS ACROSS THE  
REGION ON MONDAY. STILL LOOKS TO BE SOME QUESTION OVER TIMING THE  
FRONT'S EASTWARD ADVANCE, AND IF THE MOISTURE RECOVERY AHEAD OF THE  
FRONTAL PASSAGE WOULD BE SUFFICIENT TO HELP GENERATE ENOUGH  
INSTABILITY FOR THUNDERSTORMS. TO THE LATTER POINT, THE GFS HAS AN  
AXIS OF PWATS OVER 1.3" - 1.7" AHEAD OF THE FRONT, WHICH WOULD  
SUGGEST MOISTURE LEVELS MAY NOT NECESSARILY BE LACKING AND COULD  
SUPPORT BRIEF DOWNPOURS. DOESN'T APPEAR TO BE ENOUGH INSTABILITY FOR  
THUNDER THOUGH GIVEN MODEL SOUNDINGS REVEALING LIMITED IF ANY  
INSTABILITY, SO WILL LEAVE AS SHOWERS FOR NOW. FRONT MAY NOT FULLY  
CLEAR THE REGION UNTIL LATE MONDAY NIGHT, PARTICULARLY IF THE ECMWF  
IS CORRECT.  
 
TUESDAY - WEDNESDAY:  
 
MAY STILL HAVE SOME LINGERING LIGHT SHOWERS TOWARDS THE CAPE AND  
ISLANDS EARLY TUESDAY, BUT RIDGING LOOKS TO BUILD IN FROM QUEBEC  
ALLOWING FOR COOLER AND DRIER AIR TO FILTER IN FROM THE NORTHWEST.  
BY TUESDAY NIGHT, 850 MB TEMPERATURES LOOK TO FALL BACK INTO THE  
SINGLE DIGITS WHICH SHOULD BRING TEMPERATURES MORE IN LINE WITH  
SEASONAL CLIMATOLOGY - LOW 70S AND LOWS IN THE 40S TO LOWER 50S.  
 

 
   
AVIATION /19Z WEDNESDAY THROUGH MONDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH THURSDAY NIGHT/...  
 
VFR THROUGH THE PERIOD. GUSTY NORTHEAST WINDS CONTINUE ALONG THE  
COAST TONIGHT WITH GUSTS 20 TO 25 KT ESPECIALLY AROUND  
NANTUCKET. WINDS INLAND DIMINISH TO LIGHT. WINDS BECOME LIGHT  
ALL AREAS THURSDAY AND THURSDAY NIGHT.  
 
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.  
 
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.  
 
OUTLOOK /FRIDAY THROUGH MONDAY/...  
 
VFR.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH THURSDAY NIGHT/...HIGH CONFIDENCE.  
 
HIGH PRESSURE CENTERED OVER NEW ENGLAND. NORTHEAST WINDS  
CONTINUE ACROSS THE SOUTHERN AND SOUTHEAST WATERS WITH GUSTS OF  
20 TO 25 KT. SWELL FROM HURRICANE HUMBERTO IS BUILDING OFFSHORE  
WITH AN EAST-SOUTHEAST SWELL UP TO 7 FEET FORECAST IN THE  
SOUTHERN WATERS TONIGHT AND THURSDAY, THEN SPREADING TO THE  
EASTERN WATERS THURSDAY NIGHT.  
 
SMALL CRAFT ADVISORY CONTINUES THROUGH FRIDAY ON MOST WATERS.  
WINDS ARE A CONCERN ON THE SOUTHERN WATERS TONIGHT. ROUGH SEAS  
ARE A CONCERN THURSDAY AND FRIDAY.  
 
OUTLOOK /FRIDAY THROUGH MONDAY/...MODERATE CONFIDENCE.  
 
FRIDAY: WINDS LESS THAN 25 KT. ROUGH SEAS UP TO 12 FT.  
 
FRIDAY NIGHT: WINDS LESS THAN 25 KT. ROUGH SEAS UP TO 10 FT.  
 
SATURDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT.  
 
SATURDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING  
5 FT.  
 
SUNDAY: WINDS LESS THAN 25 KT.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...HIGH RIP CURRENT RISK UNTIL MIDNIGHT EDT TONIGHT FOR  
MAZ022>024.  
HIGH SURF ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM EDT FRIDAY  
FOR MAZ020-022>024.  
HIGH SURF ADVISORY FROM MIDNIGHT THURSDAY NIGHT TO 6 PM EDT  
FRIDAY FOR MAZ007-019.  
FROST ADVISORY FROM 3 AM TO 8 AM EDT THURSDAY FOR MAZ003-004-  
010-011.  
RI...HIGH RIP CURRENT RISK UNTIL MIDNIGHT EDT TONIGHT FOR RIZ008.  
HIGH SURF ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM EDT FRIDAY  
FOR RIZ006>008.  
MARINE...SMALL CRAFT ADVISORY UNTIL 3 AM EDT THURSDAY FOR ANZ231>234.  
SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ236.  
SMALL CRAFT ADVISORY UNTIL 6 PM EDT THURSDAY FOR ANZ235-237.  
SMALL CRAFT ADVISORY UNTIL 2 AM EDT SATURDAY FOR ANZ250-  
254>256.  
SMALL CRAFT ADVISORY UNTIL 2 AM EDT THURSDAY FOR ANZ251.  
 

 
 

 
 
SYNOPSIS...WTB/LOCONTO  
NEAR TERM...WTB  
SHORT TERM...WTB  
LONG TERM...LOCONTO  
AVIATION...WTB/LOCONTO  
MARINE...WTB/LOCONTO  
 
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