629  
FXUS61 KBOX 241335  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TAUNTON MA  
935 AM EDT SUN SEP 24 2017  
   
SYNOPSIS
 
 
HIGH PRESSURE COVERING MUCH OF THE EASTERN USA WILL BRING WARM AND  
DRY WEATHER TO SOUTHERN NEW ENGLAND THE FIRST PART OF THIS WEEK.  
COLD FRONT APPROACHES SOUTHERN NEW ENGLAND DURING WEDNESDAY  
AFTERNOON AND TRIGGERS SCATTERED SHOWERS. COLD FRONT SLOWLY MOVES  
THROUGH SOUTHERN NEW ENGLAND ON THURSDAY AND OFFSHORE THURSDAY  
NIGHT. MARIA WILL BRING SWELLS TO THE SOUTH COAST, BUT THE CENTER IS  
EXPECTED TO PASS WELL SOUTHEAST OF NEW ENGLAND LATE IN THE WEEK.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
930 AM UPDATE...  
 
STRATUS AND FOG ERODING ON THE CAPE BUT HANGING TOUGH OVER ACK.  
WE DO EXPECT STRATUS TO ERODE FOR PARTIAL SUNSHINE ON ACK WITH  
ABUNDANT SUNSHINE ELSEWHERE, BUT STRATUS AND FOG WILL LIKELY  
MOVE BACK IN ACROSS CAPE AND ISLANDS TOWARD SUNSET. RECORD HEAT  
EXPECTED IN THE CT VALLEY WITH UNSEASONABLY WARM TEMPS  
ELSEWHERE, BUT SEA BREEZES EXPECTED ALONG BOTH COASTS. NO  
CHANGES TO FORECAST TEMPS.  
 
PRIOR DISCUSSION...  
 
FULL SUN WILL MEAN DEEP MIXING, WITH THE LAYER EXPECTED TO REACH TO  
AT LEAST THE 850 MB PRESSURE LEVEL. THE MODELS HAVE BEEN KNOWN TO  
UNDERESTIMATE THIS DEPTH, SO MIXING ABOVE THAT LEVEL IS A REASONABLE  
SCENARIO, AND WOULD MEAN SURFACE TEMPERATURES WARMER THAN OUR  
ESTIMATES. BOTH THE GFS AND ECMWF PROJECT 850 MB TEMPS OF 17-19C,  
THE NAM AND GGEM 18-19C. THIS SUGGESTS INLAND AREAS WILL REACH MAX  
SFC TEMPS IN THE UPPER 80S AND LOWER 90S. LIGHT WIND UNDER THE HIGH  
PRESSURE WILL ALLOW SEA BREEZES TO DEVELOP LATER THIS MORNING. THIS  
WILL BUFFER TEMPS, SO EXPECT LOWER MAX TEMPS IN EASTERN MASS AND RI  
ESPECIALLY ALONG THE COAST.  
 
INTERIOR CLIMATE SITES ARE EXPECTED TO REACH MAX TEMPS AT OR NEAR  
RECORD LEVELS. THE SEA BREEZE AT BOSTON SHOULD KEEP LOGAN AIRPORT  
BELOW ITS RECORD.  
 
WE DO EXPECT COOLEST TEMPS TO BE FOUND ON CAPE COD. SHOULD THE FOG  
LINGER LONGER THAN ANTICIPATED, TEMPERATURES MAY BE A FEW DEGREES  
COOLER STILL.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/
 
 
HIGH PRESSURE REMAINS OVER THE REGION TONIGHT AND MONDAY. THAT MEANS  
MOSTLY CLEAR SKIES AND LIGHT WINDS. DEW POINTS WILL MOSTLY BE IN THE  
60S MUCH OF THIS TIME, SO MIN TEMPS TONIGHT WILL BE IN THE UPPER 50S  
AND 60S. EXPECT A SIMILAR MIXED LAYER MONDAY, WITH TEMPS AT 850 MB  
OF 17-18C. SO MAX TEMPS SHOULD BE SIMILAR TO TODAY, UPPER 80S AND  
LOW 90S INLAND AND COOLER NEAR THE SHORE. LIGHT FLOW WILL AGAIN  
ALLOW SEA BREEZES TO FORM, BUFFERING TEMPERATURES ALONG THE  
COASTLINE.  
 
PATCHY FOG WILL AGAIN BE POSSIBLE OVERNIGHT AND EARLY MORNING,  
FAVORING THE USUAL INLAND FOG SPOTS AS WELL AS THE SOUTH COAST.  
 

 
   
LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
 
 
HIGHLIGHTS...  
 
* VERY WARM TEMPERATURES PERSIST INTO WEDNESDAY  
* SCATTERED SHOWERS WEDNESDAY AFTERNOON THROUGH THURSDAY NIGHT  
* MARIA WILL BRING SWELLS TO THE SOUTH COAST BUT WILL SHARPLY  
RECURVE OUT TO SEA SOUTHEAST OF NEW ENGLAND LATE IN THE WEEK  
 
TUESDAY...H85 TEMPERATURES 16C TO 18C WILL SUPPORT VERY WARM  
TEMPERATURES INTO TUESDAY WITH SURFACE TEMPERATURES REACHING WELL  
INTO THE 80S THROUGHOUT MOST OF THE REGION. THE LIGHT GRADIENT FLOW,  
HOWEVER, WILL SET THE STAGE FOR SEA BREEZES ALONG THE COASTAL PLAIN.  
 
WEDNESDAY THROUGH THURSDAY NIGHT...A SURFACE COLD FRONT AND UPPER  
SHORT WAVE TROUGH WILL APPROACH SOUTHERN NEW ENGLAND WEDNESDAY  
AFTERNOON. WE ANTICIPATE SCATTERED SHOWERS TO DEVELOP AHEAD OF THE  
FRONT WEDNESDAY AFTERNOON IN MOIST, MARGINALLY UNSTABLE AIR MASS.  
MODEL GUIDANCE SUGGESTS SHOWALTERS NEAR ZERO AND K INDICES ABOV 30.  
MODELS HAVE BEEN GIVING A SIGNAL THAT TROPICAL MOISTURE FROM MARIA  
MAY BECOME ENTRAINED IN THE AIR MASS JUST AHEAD OF THE FRONT AND  
INCREASE THE RISK OF A FEW HEAVY DOWNPOURS, ALTHOUGH THERE IS  
UNCERTAINTY IN THE TIMING/DURATION OF MARIA'S MOISTURE ENTRAINMENT.  
THE AIR MASS APPEARS TO BE UNSTABLE ENOUGH TO SUPPORT ISOLATED  
THUNDER AT LEAST FOR WEDNESDAY AFTERNOON/EVENING. DUE TO THE UPPER  
SHORTWAVE TROUGH HAVING TO ERODE A VERY STRONG UPPER LEVEL RIDGE,  
THE SURFACE COLD FRONT WILL PROBABLY MOVE SLOWLY ACROSS SOUTHERN NEW  
ENGLAND AND MAY NOT PASS OFFSHORE UNTIL THURSDAY NIGHT. THUS, WE  
ANTICIPATE SCATTERED SHOWERS TO PERSIST WEDNESDAY NIGHT INTO  
THURSDAY NIGHT. WITH TROPICAL MOISTURE FROM MARIA AND PRECIPITABLE  
WATERS 1.7 TO 2 INCHES, SOME THE SHOWERS COULD CONTAIN VERY HEAVY  
DOWNPOURS ANYTIME LATE WEDNESDAY TO THURSDAY NIGHT.  
 
THE AIR MASS REMAINS MILD WEDNESDAY INTO THURSDAY, BUT CLOUDS WILL  
LIKELY TEMPER THE HIGH TEMPERATURES SOME. MAY STILL EXPERIENCE 70S  
TO NEAR 80 ON WEDNESDAY AND PROBABLY MID TO UPPER 70S ON THURSDAY.  
 
FRIDAY...MODEL CONSENSUS HAS THE COLD FRONT PASSING OFFSHORE TO THE  
SOUTHEAST OF NEW ENGLAND FRIDAY MORNING, AND MARIA PASSING WELL  
SOUTHEAST OF OUR REGION. THIS WILL RESULT IN DRIER AND COOLER AIR  
MOVING INTO SOUTHERN NEW ENGLAND, ALTHOUGH SHOWERS MAY LINGER INTO  
THE MORNING FOR A WHILE IN SOUTHEAST SECTIONS. MARIA WILL BECOME  
EMBEDDED IN THE WESTERLIES ON THE LEADING EDGE OF THE MID LATITUDE  
UPPER TROUGH AND LIKELY PASS OUT TO SEA WELL SOUTHEAST OF NEW  
ENGLAND. H85 TEMPERATURES DROP ABOUT 10C, AND FRIDAY'S HIGH  
TEMPERATURES WILL BE NOTICABLY COOLER, ALBEIT JUST CLOSER TO NORMAL,  
EVEN WITH PLENTY OF SUNSHINE AND DOWNSLOPING WINDS. DEWPOINTS IN THE  
UPPER 60S AND 70S FOR MOST OF THE WEEK WILL DROP INTO THE 40S MOST  
LOCATIONS DURING FRIDAY.  
 
SATURDAY...FOR NOW SATURDAY LOOKS TO BE DRY WITH NEAR NORMAL  
TEMPERATURES AND VERY LOW HUMIDITY.  
 

 
   
AVIATION /13Z SUNDAY THROUGH THURSDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH MONDAY/...  
 
TODAY...HIGH CONFIDENCE.  
 
IFR-LIFR CONDITIONS WILL SLOWLY IMPROVE ACROSS THE CAPE AND  
ISLANDS. VFR ELSEWHERE. LIGHT WINDS WITH COASTAL SEA BREEZES.  
 
TONIGHT...MODERATE CONFIDENCE.  
 
BELIEVE WE WILL SEE A RETURN TO STRATUS AND FOG ACROSS THE CAPE  
AND ISLANDS THIS EVENING AND POSSIBLE EXPANSION DURING THE  
OVERNIGHT OVER OTHER SECTIONS OF SE MA AND SOUTHERN RI.  
ANTICIPATE GENERALLY VFR CONDITIONS ELSEWHERE EXCEPT FOR PATCHY  
VALLEY FOG.  
 
MONDAY... HIGH CONFIDENCE.  
 
FOG OVER THE SE AND SOME INTERIOR VALLEYS BURNS OFF DURING THE  
MORNING. MOST OF THE DAY WILL BE VFR WITH LIGHT WINDS. SEA  
BREEZES AGAIN EXPECTED ALONG THE COASTLINES, INCLUDING BOS.  
 
KBOS TAF...HIGH CONFIDENCE TODAY FOR VFR. MODERATE CONFIDENCE  
TONIGHT AS POSSIBLE THAT FOG MAY REDEVELOP FOR A WHILE.  
 
KBDL TAF...HIGH CONFIDENCE IN TAF.  
 
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...  
 
CONFIDENCE...HIGH.  
 
MONDAY NIGHT THROUGH TUESDAY...MOSTLY VFR EXCEPT FOR PATCHY  
LATE NIGHT/EARLY MORNING FOG.  
WEDNESDAY...MOSTLY VFR BUT SCATTERED MVFR CEILINGS/VISIBILITIES IN  
SHOWERS, MAIN DURING THE AFTERNOON.  
WEDNESDAY NIGHT THROUGH THURSDAY...MVFR CEILINGS AND AREAS OF IFR  
CEILINGS AND VISIBILITIES IN SCATTERED SHOWERS AND FOG.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
TODAY...HIGH CONFIDENCE.  
 
HIGH PRESSURE OVER THE EASTERN USA WILL BRING LIGHT WIND TO THE  
WATERS. THE REMNANTS OF JOSE WELL SOUTH OF OUR AREA MAY FAVOR A  
LIGHT EAST WIND OVER OUR WATERS. DAYTIME HEATING OF LAND AREAS WILL  
FAVOR A SEA BREEZE ALONG THE IMMEDIATE COAST.  
 
LOCALLY DENSE FOG MAY START THE DAY OVER THE WATERS AROUND CAPE COD  
AND ISLANDS. THIS WILL MEAN A PERIOD OF POOR VISIBILITY TO START THE  
DAY. THIS FOG SHOULD THIN AND DISSIPATE OVER MOST WATERS BY MIDDAY  
OR EARLY AFTERNOON.  
 
MOST SEAS ARE AT 2-3 FEET WITH A PERIOD OF 10-15 SECONDS. THIS IS  
LEFTOVER SWELL FROM JOSE. HIGHER SEAS ARE FOUND ON THE SOUTHERN  
OUTER WATERS, AND AN ADDITIONAL SOUTH SWELL OF 3-4 FEET LEADING  
NORTH FROM MARIA WILL START SHOWING ITSELF IN OUR SOUTHERN WATERS  
LATER IN THE DAY. A HIGH SURF ADVISORY REMAINS IN PLACE IN  
ANTICIPATION OF THIS SWELL.  
 
TONIGHT AND MONDAY...  
 
LIGHT WIND CONTINUES UNDER HIGH PRESSURE. SEAS WILL CONTINUE TO  
BUILD THROUGH THE PERIOD AS INCREASING SWELL MOVES NORTH FROM MARIA.  
SOUTH SWELL SHOULD REACH 6-8 FEET BY MONDAY AFTERNOON, AFFECTING ALL  
OF OUR EXPOSED SOUTHERN SHORELINE AND POSSIBLY THE SOUTHERN BEACHES  
OF THE OUTER CAPE LATE MONDAY. EXPECT HIGH SURF AND DANGEROUS RIP  
CURRENTS AS A RESULT OF THIS SWELL.  
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...CONFIDENCE...HIGH  
 
RELATIVELY LIGHT WINDS ARE EXPECTED THROUGH THIS PERIOD. HOWEVER,  
SWELLS FROM MARIA WILL PROPAGATE INTO THE SOUTHERN COASTAL WATERS,  
BEGINNING LATE SUNDAY NIGHT OR MONDAY. SMALL CRAFT ADVISORIES WILL  
LIKELY NEED TO BE EXTENDED DUE TO ROUGH SEAS FOR THE WATERS SOUTH OF  
THE MA AND RI COAST FOR ALL OF THIS PERIOD.  
 
THE SWELLS FROM MARIA WILL LIKELY PRODUCE ANOTHER ROUND OF HIGH SURF  
AND DANGEROUS RIP CURRENTS.  
 
OUTLOOK...MONDAY NIGHT THROUGH THURSDAY  
 
CONFIDENCE...HIGH  
 
RELATIVELY LIGHT WINDS ARE EXPECTED THROUGH THURSDAY. HOWEVER,  
SWELLS FROM MARIA WILL IMPACT THE SOUTH COASTAL MARINE ZONES, AND  
SMALL CRAFT ADVISORIES WILL LIKELY BE NEEDED DUE TO ROUGH SEAS.  
 
THE SWELLS FROM MARIA WILL LIKELY PRODUCE CONTINUING HIGH SURF AND  
DANGEROUS RIP CURRENTS, PROBABLY LASTING MOST OF THE WEEK.  
 

 
   
TIDES/COASTAL FLOODING
 
 
HIGH SURF ADVISORIES REMAIN IN EFFECT THROUGH MONDAY ALONG THE SOUTH  
COAST AND THE OUTER CAPE EAST COAST. SWELLS FROM MARIA WILL LIKELY  
INCREASE THE SURF AND ASSOCIATED RIP CURRENT RISK ACROSS OUR OCEAN-  
EXPOSED SOUTH COAST STARTING LATER THIS AFTERNOON AND CONTINUING  
THROUGH THE WEEK. THIS WILL BE TRUE EVEN THOUGH MARIA MAY EVENTUALLY  
RECURVES OUT TO SEA WELL SOUTHEAST OF NEW ENGLAND.  
 

 
   
CLIMATE
 
 
BEST CHANCE FOR RECORD HIGH TEMPS WILL BE TODAY AND MONDAY, WHEN  
RECORDS ARE 85-90. RECORDS JUMP UP TUESDAY TO 89-95, WHILE LESS  
MIXING WILL LEAD TO LOWER MAX TEMPS. SO THE CHANCE FOR NEW RECORDS  
DIMINISHES TUESDAY. THE CURRENT RECORD MAX TEMPS FOR THE THREE DAYS  
ARE  
 
BOS 90/1959 89/1926 95/1881  
ORH 85/2010 85/1970 91/1930  
BDL 89/1959 90/2007 93/2007  
PVD 87/1959 89/1920 89/2007  
 
ALSO... DEW POINTS IN THE 60S, WHILE HIGH FOR THIS TIME OF YEAR,  
ARE NOT UNPRECEDENTED. THE DAILY EXTREME HIGH VALUES FOR DEW POINTS  
ARE STILL IN THE LOW 70S, EXCEPT FOR A COUPLE OF 68 AND 69 VALUES AT  
WORCESTER.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...HIGH SURF ADVISORY UNTIL 6 PM EDT MONDAY FOR MAZ020-022>024.  
RI...HIGH SURF ADVISORY UNTIL 6 PM EDT MONDAY FOR RIZ006>008.  
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 PM THIS  
AFTERNOON TO 6 PM EDT MONDAY FOR ANZ235-237.  
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 PM EDT MONDAY  
FOR ANZ254>256.  
 

 
 

 
SYNOPSIS...WTB/THOMPSON  
NEAR TERM...WTB/KJC  
SHORT TERM...WTB  
LONG TERM...THOMPSON  
AVIATION...WTB/THOMPSON  
MARINE...WTB/THOMPSON  
TIDES/COASTAL FLOODING...  
CLIMATE...  
 
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