289  
FXUS61 KBOX 172250  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
650 PM EDT WED JUL 17 2024  
   
SYNOPSIS
 
 
SCATTERED SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE REGION THIS  
EVENING BEFORE WEAKENING. A COLD FRONT MOVES INTO THE REGION  
THURSDAY BRINGING LOWER HUMIDITY AWAY FROM THE SOUTH COAST. THE  
FRONT MOVES OFFSHORE THURSDAY NIGHT WITH HIGH PRESSURE IN CONTROL  
FRIDAY THROUGH THE WEEKEND. THIS BRINGS SEASONABLE TEMPERATURES AND  
COMFORTABLE HUMIDITY LEVELS.  
 

 
   
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
 
 
650 PM UPDATE...  
 
BOWING LINE SEGMENT MOVING THROUGH CENTRAL MA WITH DAMAGING  
WIND THE MAIN THREAT. BEST LOW LEVEL LAPSE RATES ACROSS CENTRAL  
AND NE MA WHERE HIGHEST RISK OF SEVERE WEATHER WILL BE NEXT 1-2  
HOURS AS LINE MOVES EAST INTO NE MA. OTHERWISE, EXPECT A  
WEAKENING TREND THIS EVENING AS BOUNDARY LAYER COOLS AND CIN  
INCREASES. HOWEVER, STILL LOTS OF CONVECTION UPSTREAM AND  
EXPECT ADDITIONAL SCATTERED SHOWERS AND ISOLATED T-STORMS  
MOVING INTO THE REGION OVERNIGHT.  
 
PREVIOUS DISCUSSION...  
 
* SEVERE THUNDERSTORM WATCH FOR CT AND INTERIOR MA NORTH AND  
WEST OF I-95  
 
STORMS ARE INCREASING IN COVERAGE ACROSS EASTERN NY ALONG A PRE-  
FRONTAL TROUGH, AND THESE STORMS WILL MOVE WEST TO EAST ACROSS  
INTERIOR MA AND CT THROUGH EARLY EVENING. LOW AND MID LEVEL LAPSE  
RATES ARE MUTED BUT MLCAPES HAVE INCREASED TO 1000 J/KG AND FURTHER  
DESTABILIZATION IS LIKELY SO EXPECT STORMS TO INTENSIFY DURING THE  
NEXT FEW HOURS. EFFECTIVE SHEAR 35-40 KT WHICH IS MORE THAN  
SUFFICIENT FOR STORMS TO ORGANIZE INTO LINE SEGMENTS AND CLUSTERS.  
DAMAGING WIND REMAINS THE PRIMARY THREAT, BUT LATEST CSU MACHINE  
LEARNING GUIDANCE IS INDICATING THERE IS A LOW PROB FOR A TORNADO.  
MAIN FOCUS FOR SEVERE WEATHER WILL BE IN THE INTERIOR NORTH AND WEST  
OF I-95.  
 
CONVECTION SHOULD WEAKEN AS IT APPROACHES RI AND SE MA AFTER  
00Z GIVEN MORE STABLE MARINE LAYER AND DIMINISHING INSTABILITY.  
AFTER MIDNIGHT, ANOTHER WEAK SHORTWAVE IS FORECAST TO TRACK  
SOUTH OF SNE COAST AND MAY RESULT IN REGENERATION OF SHOWERS  
AND EMBEDDED T- STORMS. FOCUS FOR CONVECTION OVERNIGHT INTO THU  
MORNING WILL BE OVER THE COASTAL WATERS BUT NORTHERN EXTENT MAY  
REACH ALONG THE SOUTH COAST AND CAPE/ISLANDS WHERE INSTABILITY  
LINGERS THROUGH THE NIGHT. THE UNCERTAINTY WILL BE HOW FAR NORTH  
SHOWERS AND T-STORMS GET.  
 
OTHERWISE, COLD FRONT MOVES INTO NORTHERN AND WESTERN MA TOWARD  
DAYBREAK WITH LOWS DROPPING INTO THE 60S HERE, BUT LOWS HOLDING IN  
THE LOW-MID 70S ELSEWHERE WITH HIGH HUMIDITY.  
 

 
   
SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/
 
 
THURSDAY...  
 
A FEW SHOWERS AND ISOLATED T-STORMS MAY LINGER INTO THE  
MORNING, ESPECIALLY SE MA AND CAPE/ISLANDS AHEAD OF THE COLD  
FRONT WHERE 70+ DEWPOINTS CONTRIBUTE TO MARGINAL INSTABILITY.  
THE COLD FRONT IS EXPECTED TO EVENTUALLY STALL NEAR THE COASTAL  
PLAIN WHICH WILL KEEP HUMID CONDITIONS ALONG THE SOUTH COAST,  
BUT GRADUALLY LOWERING DEWPOINTS THROUGH THE 60S AND INTO THE  
UPPER 50S FURTHER IN THE INTERIOR DURING THE AFTERNOON WHICH  
WILL BE A WELCOMED AIRMASS CHANGE. CLOUDS WILL GIVE WAY TO  
INCREASING SUNSHINE FROM NW TO SE DURING THE MORNING AND INTO  
THE AFTERNOON WITH CAPE COD HOLDING ON TO CLOUDS THE LONGEST.  
STILL CAN'T RULE OUT AN ISOLATED SHOWER IN THE AFTERNOON ALONG  
THE SOUTH COAST WHERE HIGHER DEWPOINTS POOL. IT WILL BE WARM  
DAY BUT LESS HEAT THAN THE LAST SEVERAL DAYS. 925 MB TEMPS  
20-22C SUPPORT HIGHS IN THE MID-UPPER 80S BUT WITH LOWERING  
HUMIDITY, ESPECIALLY INTERIOR.  
 
THURSDAY NIGHT...  
 
THE COLD FRONT WILL FINALLY MOVE OFF THE COAST WITH LIGHT  
NORTHERLY FLOW BRINGING 50S DEWPOINTS ALL THE WAY TO THE SOUTH  
COAST. MAINLY CLEAR SKIES EXPECTED WITH LOWS DROPPING INTO THE  
MID-UPPER 50S ACROSS INTERIOR MA WITH LOW TO MID 60S ELSEWHERE.  
 

 
   
LONG TERM /FRIDAY THROUGH WEDNESDAY/
 
 
HIGHLIGHTS  
 
* DRY AND QUIET WEATHER LATE THIS WEEK THROUGH THE WEEKEND. NEAR  
SEASONABLE TEMPERATURES AND COMFORTABLE HUMIDITY LEVELS.  
 
* TURNING MORE UNSETTLED EARLY NEXT WEEK WITH INCREASING HUMIDITY.  
 
GIVEN THE CONVECTIVE THREAT THIS AFTERNOON AND EVENING HAVE NOT  
FOCUSED ON EXTENDED TERM.  
 
FRIDAY THROUGH SUNDAY...  
 
STUCK UNDER SOMEWHAT CYCLONIC FLOW THROUGH THIS TIMEFRAME WITH A  
DEEP TROUGH OVER ONTARIO/QUEBEC AND RIDGING OVER THE CAROLINAS INTO  
THE MID ATLANTIC. HIGH PRESSURE DOMINATES THE WEATHER THROUGH THIS  
TIMEFRAME. THERE ARE INDICATIONS THAT A WEAK COLD FRONT SLIDES IN  
LATE ON SAT INTO SUN.  
 
DRY AND QUIET WEATHER THROUGH THIS PERIOD. THERE ARE SOME  
INDICATIONS THAT THERE COULD BE SPOTTY SHOWERS ASSOCIATED WITH THE  
COLD FRONT THAT SLIDES IN LATE SAT INTO EARLY SUN. NOT ENOUGH MODEL  
CONSENSUS TO ADD AT THIS POINT IN TIME. FOR NOW NBM LOOKS QUITE  
REASONABLE. HIGH TEMPS WILL GENERALLY BE IN THE 80S, THOUGH THERE  
COULD BE SOME LOW 90S ACROSS THE MERRIMACK AND CT VALLEY THIS  
WEEKEND.  
 
MONDAY THROUGH TUESDAY...  
 
FLOW TURNING MORE SOUTHWESTERLY DURING THIS TIMEFRAME IN THE UPPER  
LEVELS WITH A SIMILAR SET UP. WILL HAVE CYCLONIC FLOW WITH TROUGH  
OVER QUEBEC EASTWARD AND THE RIDGE OVER THE CAROLINAS/MID ATLANTIC.  
HINTS THAT COULD HAVE ONE OR TWO SHORTWAVES RIDING THE RIDGE, LIKELY  
CONVECTIVE IN NATURE, WHICH COULD BRING US MORE UNSETTLED WEATHER.  
FRONTAL BOUNDARY WILL BE NEARBY/OVERHEAD.  
 
UNSETTLED DURING THIS TIMEFRAME AS FLOW TURNS MORE SOUTHWESTERLY,  
WHICH WILL BRING INCREASING MOISTURE LEVELS. CONFIDENCE QUITE LOW AT  
THIS POINT GIVEN CONVECTIVE DETAILS ARE TRICKY TO TIME OUT AT THIS  
TIME RANGE. FOR NOW THE NBM SLIGHT CHANCE TO CHANCES OF PRECIP  
SUFFICE. DID BUMP UP OUR THUNDERSTORM CHANCES AS NBM SEEMED A BIT  
LOW. HIGH TEMPS STILL IN THE 80S WITH INCREASING HUMIDITY LEVELS.  
 

 
   
AVIATION /00Z THURSDAY THROUGH MONDAY/
 
 
FORECAST CONFIDENCE LEVELS:  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
00Z TAF UPDATE...  
 
TONIGHT...MODERATE CONFIDENCE.  
 
LINE OF STRONG TO SEVERE STORMS WILL MOVE ACROSS NORTHERN AND NE  
MA THROUGH 01Z. OTHERWISE, WEAKENING CONVECTION THIS EVENING  
APPROACHING SE NEW ENG, BUT MAY SEE A REGENERATION OF SHOWERS  
AND A FEW T-STORMS LATE TONIGHT ALONG THE SOUTH COAST. AREAS OF  
MVFR-IFR STRATUS AND PATCHY FOG WILL IMPACT THE SOUTH COAST AND  
CAPE AND ISLANDS. BUT REST OF AREA SHOULD REMAIN VFR OUTSIDE OF  
ANY CONVECTION.  
 
THURSDAY...HIGH CONFIDENCE.  
 
AREAS OF MVFR-IFR CIGS LIKELY IMPACTING PORTIONS OF RI AND  
EASTERN MA IN THE MORNING, BUT IMPROVING TO VFR 14-16Z EXCEPT A  
BIT LATER OVER THE CAPE/ISLANDS. VFR INTERIOR. A FEW SHOWERS OR  
A T-STORM POSSIBLE OVER CAPE/ISLANDS IN THE MORNING. NW WIND  
AROUND 10 KT INTERIOR, WITH WINDS TURNING SW ALONG THE SOUTH  
COAST.  
 
THURSDAY NIGHT...HIGH CONFIDENCE.  
 
VFR. LIGHT WINDS.  
 
KBOS TAF...MODERATE CONFIDENCE IN TAF.  
 
LINE OF T-STORMS EXPECTED TO IMPACT THE TERMINAL 00-01Z. BRIEF  
GUSTS TO 40 KT POSSIBLE IF STORMS HOLD TOGETHER. A PERIOD OF  
MVFR CIGS POSSIBLE LATE TONIGHT AND THU MORNING, OTHERWISE VFR.  
 
KBDL TAF...MODERATE CONFIDENCE IN TAF.  
 
A FEW ADDITIONAL SHOWERS OR A T-STORM MAY IMPACT THE TERMINAL  
THROUGH 03Z.  
 
OUTLOOK /FRIDAY THROUGH MONDAY/...  
 
VFR.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS:  
 
LOW - LESS THAN 30 PERCENT.  
MEDIUM - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
THROUGH THURSDAY NIGHT: HIGH CONFIDENCE.  
 
DEVELOPING LOW LEVEL JET WILL BRING AN INCREASE IN SW WINDS OVER THE  
SOUTH COASTAL WATERS INTO THIS EVENING WITH GUSTS TO 25 KT. WINDS  
DIMINISH OVERNIGHT INTO THURSDAY, THEN SW WINDS BECOME NW THEN N THU  
NIGHT BEHIND THE FRONT. SEAS WILL PEAK UP TO 7 FT OVER SOUTH COASTAL  
WATERS TONIGHT WITH 5-6 FT SEAS LINGERING THROUGH THU BEFORE SLOWLY  
SUBSIDING THU NIGHT. AREAS OF FOG REDEVELOPING TONIGHT OVER SOUTHERN  
WATERS IMPROVING THU AFTERNOON. SHOWERS AND A FEW T-STORMS  
DEVELOPING OVERNIGHT INTO THU MORNING, ESPECIALLY SOUTHERN WATERS.  
 
RIP CURRENTS...  
 
A RIP CURRENT STATEMENT IS IN EFFECT INTO THIS EVENING AND AGAIN  
THURSDAY ALONG SOUTH COASTAL BEACHES DUE TO HIGH RISK FOR RIP  
CURRENTS. WHILE WINDS DIMINISH THU, LEFTOVER 5-6 FT SOUTHERLY SWELL  
WILL RESULT IN DANGEROUS RIP CURRENTS.  
 
OUTLOOK /FRIDAY THROUGH MONDAY/...  
 
FRIDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.  
 
FRIDAY NIGHT THROUGH MONDAY: WINDS LESS THAN 25 KT.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR CTZ002>004.  
MA...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR MAZ003>007-  
010>021-026.  
HIGH RISK FOR RIP CURRENTS UNTIL 8 PM EDT THIS EVENING FOR  
MAZ020>024.  
HIGH RISK FOR RIP CURRENTS FROM THURSDAY MORNING THROUGH THURSDAY  
EVENING FOR MAZ020-021-023-024.  
RI...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR RIZ001>007.  
HIGH RISK FOR RIP CURRENTS UNTIL 8 PM EDT THIS EVENING FOR  
RIZ006>008.  
HIGH RISK FOR RIP CURRENTS FROM THURSDAY MORNING THROUGH THURSDAY  
EVENING FOR RIZ006>008.  
MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT THURSDAY FOR ANZ232.  
SMALL CRAFT ADVISORY UNTIL 8 PM EDT THURSDAY FOR ANZ235-237-  
254>256.  
 

 
 

 
 
SYNOPSIS...KJC/BL  
NEAR TERM...KJC  
SHORT TERM...KJC  
LONG TERM...BL  
AVIATION...KJC/BL  
MARINE...KJC/BL  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab MA Page
The Nexlab RI Page
The Nexlab NH Page
The Nexlab CT Page Main Text Page