112  
FXUS61 KBOX 162311  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TAUNTON MA  
711 PM EDT WED AUG 16 2017  
   
SYNOPSIS
 
 
DRY AND PLEASANT CONDITIONS CONTINUE INTO TOMORROW. A WEATHER  
SYSTEM MOVING THROUGH THE GREAT LAKES REGION TOWARDS THE END OF  
THE WORKWEEK WILL BRING SHOWERS AND SCATTERED THUNDERSTORMS TO  
SOUTHERN NEW ENGLAND DURING FRIDAY AND SATURDAY. HIGH PRESSURE  
RETURNS WITH FAIR SEASONABLE WEATHER SUNDAY AND MONDAY. A COLD  
FRONT APPROACHES FROM THE WEST TUESDAY AND WEDNESDAY, BRINGING  
OUR NEXT CHANCE OF SHOWERS.  
 

 
   
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
 
 
7 PM UPDATE...  
 
DIURNAL CUMULUS GRADUALLY DISSIPATING EARLY THIS EVENING.  
MOSTLY CLEAR SKIES EXPECTED FOR TONIGHT. MADE SOME MINOR  
ADJUSTMENTS TO THIS EVENING'S HOURLY TEMPS/DEW POINTS BASED ON  
LATEST TRENDS, OTHERWISE FORECAST LOOKS ON TRACK.  
 
330 PM DISCUSSION FOLLOWS...  
 
VERY WEAK TROF REMAINS IN PLACE ACROSS S NEW ENGLAND THIS  
AFTERNOON AND HAS BEEN THE REASON THAT DWPTS ARE FAILING TO MIX  
AS WELL AS PREVIOUSLY FORECAST. ALTHOUGH DWPTS ARE SHIFTING INTO  
THE UPPER 50S, THERE REMAINS A FEW LOW 60S THIS AFTERNOON.  
HOWEVER, NOTING THAT THE CU FIELD CONTINUES TO DISSIPATE ACROSS  
N NEW ENGLAND SUGGESTING THAT AS THE TROF WEAKENS (ESPECIALLY  
THIS EVENING), THE DRIER AIR SHOULD INFILTRATE THE LOW LVLS AND  
ALLOW THE DWPTS TO CONTINUE TO DIMINISH.  
 
THIS GRADUAL DROP IN DWPTS, ALONG WITH A TREND TOWARD SKC  
CONDITIONS GENERALLY ACROSS THE BOARD, COMBINED WITH A WEAK SFC  
PRES GRADIENT SHOULD ALLOW FOR A GOOD RADIATIONAL COOLING NIGHT.  
MINS LOOK TO DROP INTO THE 50S IN MOST LOCATIONS EXPECT THE  
WARMEST HEAT ISLANDS. CANNOT RULE OUT A FEW UPPER 40S IN THE  
MOST SHELTERED VALLEYS OF NW MA, BUT THESE WOULD GENERALLY BE  
FEW AND FAR BETWEEN. OVERALL, A GOOD SLEEPING NIGHT.  
 

 
   
SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/
 
 
TOMORROW...  
HIGH PRES CRESTS OVER THE REGION PROVIDING STOUT SUBSIDENCE.  
DESPITE THE MOSTLY SUNNY CONDITIONS THIS SUGGESTS, THE  
COMBINATION OF SUPPRESSED MIXING AND A COOLER START TO THE DAY  
WILL LEAD TO OVERALL HIGH TEMPS A FEW DEGREES COOLER THAN  
YESTERDAY. THIS IS ALSO IN SPITE OF GENERALLY W FLOW. MAINLY  
UPPER 70S AND LOW 80S IN THE WARMEST SPOTS WHERE THE DOWNSLOPING  
CAN BE MAXIMIZED. OVERALL A PLEASANT DAY ESPECIALLY WITH DWPTS  
REMAINING IN THE 50S.  
 
WILL STILL NEED TO WATCH MAINLY EXPOSED BEACHES ACROSS CAPE COD  
AND NANTUCKET, AS THE REMNANTS OF GERT CONTINUE TO SHIFT EAST, A  
LINGERING SWELL COULD MAINTAIN A MODERATE RISK FOR RIP CURRENTS  
THROUGH THE DAY IN THESE AREAS.  
 
TOMORROW NIGHT...  
A PLEASANT EVENING TO START, HOWEVER UPPER LVL WAVE WILL BE  
TILTING AND LIFTING THROUGH ONTARIO AND QUEBEC WITH SFC WAVE  
PUSHING A WARM FRONT TOWARD NEW ENGLAND. PWATS INCREASE THROUGH  
THE OVERNIGHT HOURS, SUCH THAT BY 12Z FRI, THEY NEAR 2.00  
INCHES (OR NEARLY 2 STD DEVIATIONS ABOVE NORMAL). INITIAL  
OVERRUNING IS WEAK AND THIS MOISTURE LOAD IS FROM THE TOP OF THE  
COLUMN TO THE SFC. THEREFORE, EXPECTING ONLY BUILDING CLOUDS  
THROUGH THE EVENING, WITH THE RISK FOR ANY PRECIPITATION HOLDING  
OFF UNTIL THE EARLY MORNING HOURS. INDEED, TIMING OF  
MEASURABLE QPF HAS SLOWED ON REGIONAL MODELS DUE TO THIS  
INITIAL LACK OF LIFT AND DRY COLUMN. STILL COULD SEE SOME  
WETTING RAINFALL BY SUNRISE MAINLY W OF THE WORCESTER HILLS IN  
MA AND THAMES RIVER REGION OF CT. NOTING SOME QPF BULLSEYES,  
BUT THESE ARE MOSTLY LIKELY SOME CONVECTIVE FEEDBACK. COLUMN  
REMAINS RELATIVELY STABLE THROUGH 12Z.  
 
THE INCREASED MOISTURE FROM W-E WILL LIMIT DIURNAL COOLING IN  
SPITE OF THE WEAK PRES GRADIENT TO START. COOLEST AREAS WILL  
LIKELY BE ACROSS E MA/RI, WHERE SOME RADIATIONAL COOLING CAN  
OCCUR INITIALLY. OVERNIGHT MINS RANGE FROM THE UPPER 50S IN  
THESE COOLER SPOTS TO THE LOW 60S ELSEWHERE DUE TO THE INCREASED  
CLOUD COVER.  
 

 
   
LONG TERM /FRIDAY THROUGH WEDNESDAY/
 
 
DETAILS...  
 
FRIDAY AND SATURDAY... MODERATE CONFIDENCE.  
 
DURING FRIDAY AND SATURDAY SHORT WAVES MOVE EASTWARD THRU OUR AREA,  
WITH THE UPPER RIDGE AXIS SHIFTING OFFSHORE AND UPPER TROUGH MOVING  
INTO THE GREAT LAKES REGION, GRADUALLY APPROACHING OUR AREA. SURFACE  
HIGH PRESSURE SLIDES FURTHER OFFSHORE WHILE SURFACE LOW CHURNS THRU  
NORTHERN GREAT LAKES REGION, HEADING TOWARDS SOUTHERN QUEBEC.  
 
ON FRIDAY A WARM FRONT ASSOCIATED WITH THE GREAT LAKES SURFACE LOW  
LIFTS NORTHWARD INTO OUR AREA. SOUTHERLY FLOW WILL BRING DEEP  
MOISTURE TO SOUTHERN NEW ENGLAND, WITH PRECIPITABLE WATER VALUES  
INCREASING TO AROUND 2 INCHES BY MIDDAY. THIS IN CONJUNCTION WITH  
SHORT WAVES WILL ALLOW FOR RAIN/SHOWERS FRIDAY-FRI NIGHT. LACK OF  
SURFACE-BASED CAPE ON FRIDAY, BUT SURFACE LIS DROP TO 0 TO  
-2 AND K INDICES MID 30S. SHOULD BE PRIMARILY SHOWERS BUT CAN'T RULE  
OUT RUMBLES OF THUNDER. COULD SEE BRIEF HEAVY DOWNPOURS.  
 
DURING SATURDAY THE SURFACE LOW'S ASSOCIATED COLD FRONT ADVANCES  
EASTWARD THROUGH OUR REGION, WHILE UPPER TROUGH APPROACHES FROM THE  
WEST. MODELS ALSO INDICATE A ZONE OF UPPER DIFLUENCE AFFECTING OUR  
AREA. WHILE DEEPER MOISTURE AXIS SHIFTS OFFSHORE, WE STILL START THE  
DAY WITH PRECIPITABLE WATER 1.5 INCHES OR SO ACROSS THE EASTERN HALF  
OF THE AREA, SOMEWHAT LESS LATER IN THE DAY. CAPE VALUES 500-1000  
J/KG. EXPECTING SCATTERED SHOWERS WITH A CHANCE OF THUNDERSTORMS.  
 
MAX TEMPS ARE EXPECTED TO BE MAINLY IN THE 70S ON FRIDAY. AIRMASS  
WARMS SEVERAL DEGREES SATURDAY WITH HIGHS RANGING FROM THE UPPER 70S  
TO MID 80S. HIGH DEW POINTS SHOULD CONTRIBUTE TO AREAS OF FOG EACH  
NIGHT/EARLY MORNING.  
 
ANTICIPATING A DRYING TREND SATURDAY NIGHT, HOWEVER MODELS HINT AT  
POTENTIAL FOR A WEAK SURFACE LOW DEVELOPING ALONG THE FRONT IN  
NORTHERN NEW ENGLAND AS THE UPPER TROUGH PASSES THRU NEW ENGLAND, SO  
THIS COULD KEEP SOME CLOUDS AND A CHANCE FOR LIGHT RAIN IN OUR AREA  
AT LEAST EARLY. PATCHY FOG POSSIBLE.  
 
SUNDAY THROUGH WEDNESDAY...  
 
UPPER TROUGH LIFTS OUT DURING THE SUNDAY WITH SURFACE HIGH PRESSURE  
BUILDING EAST INTO THE AREA DURING SUNDAY AND MONDAY. SO  
ANTICIPATING A PERIOD OF MAINLY DRY WEATHER. THEN THE HIGH MOVES  
OFFSHORE MONDAY NIGHT AND TUESDAY, WITH INCREASING MOISTURE LATER  
TUESDAY AS ANOTHER SHORT WAVE AND COLD FRONT APPROACH FROM THE WEST.  
THIS COULD BRING OUR NEXT ROUND OF SHOWERS FOR LATE TUESDAY-TUE  
NIGHT AND WEDNESDAY.  
 

 
   
AVIATION /23Z 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/...  
 
TONIGHT INTO TOMORROW...HIGH CONFIDENCE. VFR EXCEPT SOME VERY  
PATCHY GROUND FOG EARLY AM MAINLY AT TYPICALLY PRONE TERMINALS.  
WINDS SHIFT LIGHTLY W DURING THE DAY EXCEPT SEA BREEZES ALONG  
COAST.  
 
TOMORROW NIGHT...MODERATE CONFIDENCE.  
AREA OF RAINFALL ACCOMPANIED BY A MIX OF MVFR/IFR CONDITIONS  
LATE, ESPECIALLY DURING THE EARLY FRI MORNING HOURS. VFR TO  
START THE OVERNIGHT. WINDS SHIFT TO THE S.  
 
KBOS TERMINAL...HIGH CONFIDENCE IN TAF. SEA BREEZE DEVELOPMENT  
EXPECTED FOR THU.  
 
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.  
 
OUTLOOK /FRIDAY THROUGH MONDAY/...  
 
FRIDAY THROUGH MONDAY... MODERATE CONFIDENCE.  
 
FRIDAY...TRENDING TO MVFR/IFR IN SHOWERS, SCATTERED THUNDERSTORMS  
AND AREAS OF FOG.  
 
SATURDAY...MVFR/IFR TO START. IMPROVING TO VFR, EXCEPT FOR POSSIBLY  
THE CAPE AND ISLANDS WHERE MVFR/IFR COULD LINGER THRU THE DAY. THEN  
LOCALIZED MVFR/IFR SATURDAY NIGHT IN PATCHY FOG POSSIBLE.  
 
SUNDAY AND 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.  
 
NOTING SEAS HAVE REACHED 8-9 FT ALONG THE OPEN OCEAN WATERS S OF  
S NEW ENGLAND AS HURRICANE GERT BEGINS ITS E SHIFT. THIS WILL  
ALLOW THESE SEAS TO GRADUALLY RECEDE THROUGH THE OVERNIGHT  
HOURS. SMALL CRAFT ADVISORIES CONTINUE, BUT WILL BE ABLE TO BE  
DROPPED AS THE NIGHT PROGRESSES. OTHERWISE, MAINLY QUIET  
BOATING WEATHER CONTINUED INTO TOMORROW NIGHT AFTER THESE SEAS  
RECEDE.  
 
OUTLOOK /FRIDAY THROUGH MONDAY/...  
 
FRIDAY...  
 
WINDS/SEAS BELOW SCA THRESHOLDS TO START, HOWEVER DURING LATE  
FRIDAY/FRI NIGHT MAY SEE SOME SOUTHERLY WIND GUSTS TO 25 KTS. SEAS  
BUILDING TO 3-5 FEET FRIDAY NIGHT. INCREASING CHANCE OF SHOWERS WEST  
TO EAST DURING FRIDAY. A SMALL CRAFT ADVISORY MAY BE NEEDED. SHOWERS  
AND SCATTERED THUNDERSTORMS FRIDAY NIGHT AND REDUCED VISIBILITY  
IN AREAS OF FOG.  
 
SATURDAY...  
 
LINGERING SHOWERS AND SCATTERED THUNDERSTORMS SATURDAY, WITH REDUCED  
VISIBILITY IN PATCHY FOG. SEAS 3 TO 6 FEET ON THE OUTER WATERS,  
AND POSSIBLY THE EXPOSED PORTIONS OF THE SOUTHERN WATERS,  
SUBSIDING DURING SAT NIGHT. SOUTHERLY WINDS SATURDAY TURN TO THE  
WEST SATURDAY NIGHT WITH GUSTS TO 25 KTS POSSIBLE. A SMALL  
CRAFT ADVISORY MAY BE NEEDED.  
 
SUNDAY AND MONDAY...  
 
HIGH PRESSURE BUILDS OVER THE WATERS. WINDS AND SEAS EXPECTED TO BE  
BELOW SCA THRESHOLDS. ISOLATED SHOWERS POSSIBLE EARLY SUNDAY, BUT  
THESE MOVE OFF TO THE EAST DURING THE MORNING.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...HIGH SURF ADVISORY UNTIL 8 PM EDT THIS EVENING FOR MAZ020-  
022>024.  
RI...HIGH SURF ADVISORY UNTIL 8 PM EDT THIS EVENING FOR RIZ006>008.  
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 PM EDT THIS  
EVENING FOR ANZ232>234.  
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 3 AM EDT  
THURSDAY FOR ANZ235-237.  
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 AM EDT  
THURSDAY FOR ANZ254>256.  
 

 
 

 
SYNOPSIS...DOODY/NMB  
NEAR TERM...DOODY/NMB  
SHORT TERM...DOODY  
LONG TERM...NMB  
AVIATION...DOODY/NMB  
MARINE...DOODY/NMB  
 
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