567  
FXUS61 KBOX 131601  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
1201 PM EDT SAT JUL 13 2024  
   
SYNOPSIS
 
 
SHOWERS, AND SOME DOWNPOURS, INTO EARLY AFTERNOON. HOT ON  
SUNDAY, BUT SLIGHTLY DRIER WITH SUNNY SKIES. DANGEROUS HEAT AND  
HUMIDITY IS EXPECTED MONDAY, TUESDAY, AND WEDNESDAY WITH  
AFTERNOON HEAT INDICES BETWEEN 95 AND 105 DEGREES. THE GREATEST  
RISK FOR SCATTERED SHOWERS AND THUNDERSTORMS WILL BE MONDAY AND  
WEDNESDAY, BUT MUCH OF THIS TIME WILL STILL FEATURE DRY WEATHER.  
RELIEF FROM THE HEAT AND HUMIDITY ARRIVES BY THURSDAY AND  
FRIDAY.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
CANCELED PART OF THE FLOOD WATCH, AS THE HEAVIEST RAINFALL HAS  
MOVED FATHER SOUTHEAST. WILL CONTINUE TO MONITOR THE REMAINING  
FLOOD WATCH. CURRENT THINKING IS THIS CAN LIKELY BE CANCELED  
PRIOR TO ITS 8 PM EXPIRATION TIME. WILL SEE HOW THINGS EVOLVE  
OVER THE NEXT COUPLE OF HOURS.  
 
PREVIOUS DISCUSSION...  
 
STILL A RISK FOR EMBEDDED THUNDERSTORMS THIS MORNING, BUT LOSING  
CONFIDENCE THAT WE WILL SEE THEM. HAVE NOT SEEN ACTIVE LIGHTNING  
DURING THE PAST COUPLE OF HOURS. LATEST SPC MESOANALYSIS SHOWED  
A SIMILAR PICTURE. PLENTY OF BUOYANCY, BUT POOR MID LEVEL LAPSE  
RATES. SHEAR WAS OFFSET TO THE NORTHWEST, SO NOT EXPECTING  
SEVERE WEATHER.  
 
UPDATED RAINFALL CHANCES USING THE LATEST RUNS OF THE HRRR,  
WHICH SEEMED TO HAVE THE BEST HANDLE ON THE EXISTING RAINFALL.  
WILL RECONSIDER THE FLOOD WATCH LATER TODAY, AS WILL LIKELY BE  
ABLE TO DROP PORTIONS PRIOR TO THE EXISTING EXPIRATION OF 8 PM.  
MINOR TWEAKS TO TEMPERATURES TO REFLECT OBSERVED TRENDS.  
 
645 AM UPDATE...  
 
* SHOWERS WITH A FEW T-STORMS AND LOCALIZED TORRENTIAL RAINFALL  
INTO MID AFTERNOON WITH THE GREATEST RISK SOUTH OF I-90  
 
A CLUSTER OF SHOWERS AND EMBEDDED T-STORM QUICKLY MOVED ACROSS  
AREAS NEAR THE SOUTH COAST EARLIER THIS MORNING AND WERE  
ALREADY EXITING THE CAPE. HOWEVER...AN ADDITIONAL BAND OF  
SHOWERS HAS SET UP IN NORTHEAST AXIS IN THE VICINITY OF A  
SPRINGFIELD TO FITCHBURG LINE. SO FAR RAINFALL RATES HAVE BEEN  
UNDER CONTROL...BUT GIVEN PWATS OF 2+ INCHES IN PLACE AND  
DEWPOINTS BETWEEN 70 AND 75 ANY OF THIS ACTIVITY WILL BE CAPABLE  
OF PRODUCING TORRENTIAL RAINFALL AND VERY LOCALIZED  
FLOODING...ESPECIALLY IF IT OCCURS IN A VULNERABLE URBAN CENTER.  
THE MESOSCALE PROCESSES INVOLVED THOUGH MAKE IT VERY DIFFICULT  
TO LOCATE WHERE THIS MAY OCCUR...BUT LATEST GUIDANCE CONTINUES  
TO INDICATE AREAS SOUTH OF I-90 MOST AT RISK. THINKING IS THAT  
THE FLOOD THREAT WILL BE LOCALIZED...BUT WORTH CONTINUING THE  
FLOOD WATCH GIVEN THE TROPICAL ENVIRONMENT IN PLACE. EMBEDDED  
THUNDER IS ALSO POSSIBLE WITH ANY OF THE ACTIVITY ESPECIALLY  
ACROSS RI/SE MA. PREVIOUS DISCUSSION BELOW.  
 
SHORT-WAVE ENERGY APPROACHING FROM THE WEST AND CONVERGENCE  
ALONG A STALLED FRONTAL BOUNDARY IS EXPECTED TO SUPPORT BANDS OF  
SHOWERS WITH HEAVY DOWNPOURS AND EMBEDDED THUNDER THIS MORNING.  
THESE SHOWERS WILL HAVE THE POTENTIAL TO PRODUCE EXCESSIVE  
RAINFALL AS THE ATMOSPHERE WILL HOLD TROPICAL LIKE  
CHARACTERISTICS WITH 2+ INCH PWATS, DEEP WARM CLOUD LAYER DEPTHS  
EXCEEDING 11000 FEET, AND MODERATE INSTABILITY WITH SBCAPE  
VALUES NEAR 1000 J/KG. GIVEN THE WEAKLY FORCED ENVIRONMENT,  
THERE REMAINS QUITE A BIT OF UNCERTAINTY WITH RESPECT TO WHERE  
THE HEAVIEST RAINFALL WILL SETUP. LATEST HI-RES MODEL GUIDANCE  
HAS TRENDED TOWARD SOUTHEASTERN MA, RI, THE CAPE AND ISLANDS  
BEING AT THE GREATEST RISK FOR EXCESSIVE RAINFALL. NONETHELESS,  
SEVERAL SOLUTIONS STILL SUPPORT BANDS OF HEAVY PRECIP ACROSS  
WESTERN MA AND CT. GIVEN THE UNCERTAINTY, NO CHANGES HAVE BEEN  
MADE TO THE FLOOD WATCH HEADLINES CURRENTLY IN PLACE.  
 
AS PREVIOUSLY FORECAST, MOST OF THE SHOWER/THUNDERSTORM ACTIVITY  
WILL TAKE PLACE BEFORE NOON TIME TODAY. THEREAFTER, WE SHOULD  
SEE SOME CLEARING FROM NORTHWEST TO SOUTHEAST AS THE 2+ INCH  
PWAT PLUME REGRESSES TO THE SOUTHEAST. AFTER NOON TIME  
HOWEVER,THE EQUATORWARD ENTRANCE REGION OF A 100 KNOT 250 HPA  
JET IS EXPECTED TO DEVELOP OVER THE NORTHERN HALF OF THE  
FORECAST AREA. SOME HI-RES MODEL GUIDANCE HAS BEEN HINTING AT  
THE POTENTIAL FOR THIS FEATURE TO PROVIDE ADDITIONAL FORCING TO  
SUPPORT REDEVELOPMENT OF A FEW THUNDERSTORMS ACROSS INTERIOR  
SOUTHERN NEW ENGLAND DURING THE MID- AFTERNOON/EVENING HOURS.  
CONFIDENCE IN THIS OUTCOME IS LOW, BUT ADDITIONAL THUNDERSTORMS  
AFTER THIS MORNING'S "MAIN EVENT" WILL BE POSSIBLE BEFORE  
SUNSET. ASIDE FROM THE SHOWER/THUNDERSTORM CHANCES, EXPECT  
CONTINUED MUGGY CONDITIONS WITH HIGHS IN THE MID TO UPPER 80S.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/
 
 
TONIGHT  
 
A SURFACE FRONTAL BOUNDARY MOVES THROUGH THE REGION OVERNIGHT  
WITH NORTHWEST FLOW AND A DRIER AIRMASS. PWATS FALL TO VALUES  
CLOSE TO AN INCH. THIS SHOULD RESULT IN A QUIET EVENING WITH  
CLEARING SKIES FROM NORTHWEST TO SOUTHEAST. THERE WILL BE SOME  
RELIEF FROM THE HUMIDITY AS DEWPOINTS FALL INTO THE MID TO UPPER  
60S ACROSS THE REGION, BUT THE URBAN AREAS WILL STILL STRUGGLE  
TO FALL BELOW 70.  
 
TOMORROW  
 
A SUBTLE MID-LEVEL RIDGE BUILDS OVER SOUTHERN NEW ENGLAND  
TOMORROW WITH WEAK HIGH PRESSURE AT THE SURFACE. THIS WILL  
SUPPORT A SUNNY/HOT AFTERNOON. NOT EXPECTING HUMIDITY TO BE AS  
OPPRESSIVE AS WITH PREVIOUS DAYS AS LIGHT WEST/NORTHWEST FLOW  
WILL ALLOW DEWPOINTS TO DROP INTO THE LOW TO MID 60S ACROSS MUCH  
OF INTERIOR SOUTHERN NEW ENGLAND. HUMIDITY MAY LINGER OVER THE  
SOUTHEASTERN AREAS WITH DEWPOINTS STILL IN THE LOW 70S. EXPECT  
HIGHS IN THE UPPER 80S TO LOW 90S WITH SOME MID 90S POSSIBLE IN  
THE CT RIVER VALLEY. COASTAL AREAS MAY BE SLIGHTLY COOLER AS THE  
GRADIENT WIND MAY BE WEAK ENOUGH TO SUPPORT SEA-BREEZES ALONG  
THE COAST.  
 

 
   
LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
 
 
KEY POINTS...  
 
* DANGEROUS HEAT & HUMIDITY MON/TUE/WED...HEAT INDICES 95-105  
DEGREES  
* GREATEST RISK FOR SCATTERED SHOWERS & T-STORMS MON AND  
ESPECIALLY WED  
* RELIEF FROM THE HEAT & HUMIDITY BY THU AND FRI  
 
DETAILS...  
 
MON/TUE/WED...  
 
EXCELLENT MODEL AGREEMENT IN STRONG UPPER LEVEL RIDGE IN THE  
ATLANTIC AND SHORTWAVE ENERGY IN CANADA DROPPING TOWARDS THE  
GREAT LAKES. THIS WILL RESULT IN WESTERLY FLOW ALOFT WITH  
ABOVE NORMAL HEIGHT FIELDS AND HIGH CONFIDENCE IN DANGEROUS HEAT  
AND HUMIDITY. HIGH TEMPS MON/TUE/WED SHOULD BE WELL INTO THE  
90S IN MOST LOCATIONS AWAY FROM ANY POTENTIAL LOCALIZED MARINE  
INFLUENCES NEAR THE IMMEDIATE COAST. DEWPOINTS IN THE LOWER TO  
MIDDLE 70S WILL RESULT IN VERY HUMID CONDITIONS...BRINGING  
AFTERNOON HEAT INDICES INTO THE 95 TO 105 DEGREE RANGE EACH DAY.  
HEAT HEADLINES WILL CERTAINLY BE NEEDED. IN FACT...THE WORST OF  
THE HEAT APPEARS TO BE TUE & WED WHEN WE MAY EVEN NEED SOME  
EXCESSIVE HEAT HEADLINES FOR THE POTENTIAL OF HEAT INDICES OF  
105+. REGARDLESS OF THE SPECIFIC TEMPS...THE MAIN STORY WILL BE  
DANGEROUS HEAT AND HUMIDITY IN THE MON THROUGH WED TIME FRAME.  
 
THE OTHER ISSUE WILL BE ASSESSING THE POTENTIAL FOR SCATTERED  
SHOWERS AND THUNDERSTORMS. WESTERLY FLOW ALOFT WITH THE  
MESOSCALE PART OF IT THIS TIME OF YEAR MAKES THAT QUITE A  
CHALLENGE. FOR WHAT ITS WORTH...MOST OF THE GUIDANCE INDICATES  
MON AND ESPECIALLY WED WITH THE GREATEST RISK FOR A ROUND OF  
SCATTERED SHOWERS AND THUNDERSTORMS...BUT CAN NOT RULE OUT A FEW  
ON TUE EITHER. THAT BEING SAID...THIS IS TYPICAL SUMMERTIME  
CONVECTION SO MUCH OF THIS TIME WILL STILL FEATURE DRY WEATHER.  
GIVEN THE ANOMALOUS HOT AND HUMID AIRMASS IN PLACE...INSTABILITY  
WILL LIKELY BE HIGH FOR THIS PART OF THE COUNTRY. IN  
ADDITION...APPEARS WE MAY HAVE SOME SORT OF REMNANT EML TO WORK  
WITH AS WELL. SO IF WIND FIELDS ALOFT END UP STRONG ENOUGH THERE  
WILL BE THE POTENTIAL FOR SEVERE WEATHER. THE CSU MACHINE  
LEARNING PROBS ALSO CONTINUE TO INDICATE THIS POTENTIAL IN THE  
MON THROUGH WED TIME FRAME...SO WILL NEED TO CONTINUE TO MONITOR  
THIS POTENTIAL.  
 
THU/FRI...  
 
WE MAY BE DEALING WITH SOME LINGERING SHOWERS FOR THE FIRST PART  
OF THU...DEPENDING ON THE TIMING OF THE FRONT. HOWEVER...THE  
MAIN STORY WILL BE HIGH PRESSURE BUILDING IN FROM THE MIDWEST  
BEHIND THE COLD FRONT. THE RESULT WILL BE RELIEF FROM THE HEAT &  
HUMIDITY BY THU AND FRI WITH SEASONABLE OR EVEN SLIGHTLY BELOW  
NORMAL TEMPERATURES. QUITE THE WELCOMED CHANGE FROM THE FIRST  
HALF OF THE UPCOMING WEEK!  
 

 
   
AVIATION /16Z SATURDAY THROUGH WEDNESDAY/
 
 
FORECAST CONFIDENCE LEVELS:  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
TODAY...MODERATE CONFIDENCE  
 
AREAS OF SHOWERS, WITH SOME DOWNPOURS, FOR MOST OF SOUTHERN NEW  
ENGLAND THROUGH ABOUT 18Z. THERE IS UNCERTAINTY ON THE OVERALL  
COVERAGE OF TSRA, BUT THE GREATEST RISK IS SOUTH OF THE MA  
TURNPIKE. CONDITIONS SHOULD BEGIN TO IMPROVE AFTER 18Z WITH  
VFR CONDITIONS SETTLING IN, BUT THERE IS A RISK FOR SOME  
REDEVELOPMENT OF SCATTERED SHOWERS AND A FEW STORMS MAINLY  
ACROSS THE INTERIOR IN NORTHERN AND WESTERN MA BETWEEN ABOUT 18Z  
AND 21Z. CONFIDENCE NOT HIGH ENOUGH TO INCLUDE MENTIONS OF  
THUNDER DURING THIS TIME PERIOD, BUT DID LEAVE VCSH IN THE TAF  
UPDATE THROUGH 00Z. AS FOR CEILINGS, THEY ARE RATHER VARIABLE  
THIS MORNING, BUT EXPECT A LOT OF MVFR CONDITIONS. THOSE SHOULD  
TEND TO IMPROVE TO VFR THIS AFTERNOON, EXCEPT FOR AREAS NEAR  
THE SOUTH COAST, WHERE MVFR-IFR CONDITIONS WILL PROBABLY  
PERSIST.  
 
TONIGHT...MODERATE CONFIDENCE  
 
ANY REMAINING SCATTERED SHOWERS SHOULD DIMINISH DURING THE EARLY  
EVENING. OTHERWISE...MVFR-IFR CEILINGS WILL PRETTY MUCH BE  
CONFINED TO AREAS NEAR THE SOUTH COAST. HOWEVER...LIGHT-CALM  
WINDS/HIGH DEWPOINTS MAY ALLOW FOR PATCHY GROUND FOG TO DEVELOP  
ESPECIALLY IN THE TYPICALLY PRONE LOCATIONS.  
 
TOMORROW...HIGH CONFIDENCE  
 
VFR. LIGHT NORTHWEST WINDS BECOMING MORE WESTERLY DURING THE  
AFTERNOON. WINDS MAY BE WEAK ENOUGH TO SUPPORT SEA-BREEZES ALONG  
THE COAST.  
 
KBOS TAF...MODERATE CONFIDENCE IN TAF.  
 
KBDL TAF...MODERATE CONFIDENCE IN TAF.  
 
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...  
 
SUNDAY NIGHT: VFR.  
 
MONDAY: MAINLY VFR, WITH AREAS MVFR POSSIBLE. BREEZY. CHANCE  
SHRA, CHANCE TSRA.  
 
MONDAY NIGHT: MAINLY VFR, WITH AREAS MVFR POSSIBLE. SLIGHT  
CHANCE SHRA, SLIGHT CHANCE TSRA.  
 
TUESDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. BREEZY. SLIGHT  
CHANCE SHRA, SLIGHT CHANCE TSRA.  
 
TUESDAY NIGHT: MAINLY VFR, WITH AREAS MVFR POSSIBLE. BREEZY.  
SLIGHT CHANCE SHRA, SLIGHT CHANCE TSRA.  
 
WEDNESDAY: MAINLY VFR, WITH AREAS MVFR POSSIBLE. BREEZY. CHANCE  
SHRA, CHANCE TSRA.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS:  
 
LOW - LESS THAN 30 PERCENT.  
MEDIUM - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
MARINE  
 
TODAY  
 
SHOWERS WITH EMBEDDED THUNDER MOVE OVER THE COASTAL WATERS THIS  
MORNING. THIS WILL BE FOLLOWED BY SOME CLEARING DURING THE  
AFTERNOON. WINDS REMAIN STEADY OUT OF THE SOUTHWEST. SEAS  
GENERALLY 3 TO 5 FEET OVER THE SOUTHERN MARINE ZONES AND 1 TO  
3 FEET OVER THE EASTERN MARINE ZONES.  
 
TONIGHT AND TOMORROW  
 
WEAK HIGH PRESSURE BUILDS OVER THE COASTAL WATERS TONIGHT INTO  
TOMORROW. THIS WILL SUPPORT DIMINISHING WINDS AND SUBSIDING SEAS  
WITH RELATIVELY CALM CONDITIONS OVER THE MARINE ZONES.  
 
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...  
 
SUNDAY NIGHT: WINDS LESS THAN 25 KT.  
 
MONDAY: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN SHOWERS,  
SLIGHT CHANCE OF THUNDERSTORMS.  
 
MONDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING  
5 FT. SLIGHT CHANCE OF RAIN SHOWERS, SLIGHT CHANCE OF  
THUNDERSTORMS.  
 
TUESDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.  
 
TUESDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING  
5 FT. SLIGHT CHANCE OF RAIN SHOWERS.  
 
WEDNESDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS  
UP TO 25 KT. AREAS OF SEAS APPROACHING 5 FT. SLIGHT CHANCE OF  
RAIN SHOWERS, SLIGHT CHANCE OF THUNDERSTORMS.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR MAZ013-015>021.  
RI...FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR RIZ001>007.  
MARINE...SMALL CRAFT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR ANZ255-  
256.  
 

 
 

 
 
SYNOPSIS...FRANK/RM  
NEAR TERM...BELK/FRANK/RM  
SHORT TERM...RM  
LONG TERM...FRANK  
AVIATION...FRANK/RM  
MARINE...FRANK/RM  
 
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