234  
FXUS61 KBOX 100752  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
336 AM EDT TUE JUL 10 2018  
   
SYNOPSIS
 
 
ANOTHER HOT AFTERNOON IS ON TAP TODAY AND AN APPROACHING COLD  
FRONT WILL TRIGGER SCATTERED SHOWERS AND THUNDERSTORMS LATE  
TODAY AND TONIGHT. A FEW STRONG STORMS ARE POSSIBLE IN THE  
INTERIOR. TROPICAL STORM CHRIS IS EXPECTED TO INTENSIFY INTO A  
HURRICANE TODAY BUT PASS WELL SOUTHEAST OF NANTUCKET WEDNESDAY.  
HIGH PRESSURE WILL BUILD OVER THE REGION THURSDAY AND FRIDAY  
RESULTING IN MAINLY DRY WEATHER ALONG WITH SEASONABLE  
TEMPERATURES AND COMFORTABLE HUMIDITY LEVELS. A RETURN TO HOT  
WEATHER IS EXPECTED LATER THIS WEEKEND INTO EARLY NEXT WEEK. WHILE A  
FEW THUNDERSTORMS CAN NOT BE RULED OUT THIS WEEKEND INTO EARLY NEXT  
WEEK, DRY WEATHER LOOKS TO DOMINATE THE MAJORITY OF THE TIME.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
* A FEW STRONG TO SEVERE T-STORMS POSSIBLE LATE TODAY ACROSS  
INTERIOR MA *  
 
APPROACHING NORTHERN STREAM TROUGH WILL DELIVER A COLD FRONT  
WHICH WILL MOVE INTO SNE LATER TODAY. VERY WARM PRE-FRONTAL  
AIRMASS WITH 850 MB TEMPS NEAR 19C AND 925 MB TEMPS 26C. THIS  
SUPPORTS HIGHS INTO THE LOW AND MID 90S AWAY FROM THE SOUTH  
COAST, WARMEST IN THE INTERIOR VALLEYS. COOLER MID/UPPER 80S  
ALONG THE SOUTH COAST WITH SW FLOW. DEWPOINTS UPPER 50S AND  
LOWER 60S DURING THE PEAK OF THE HEAT SO HUMIDITY LEVELS WILL BE  
MANAGEABLE.  
 
MAIN CONCERN FOR LATER TODAY IS THE POTENTIAL FOR A FEW STRONG  
TO SEVERE STORMS IN THE INTERIOR AS A COLD FRONT MOVES INTO THE  
REGION. SBCAPES EXPECTED TO INCREASE TO 1000-1500 J/KG WITH AXIS  
OF DEEPER MOISTURE AHEAD OF THE FRONT WITH KI INTO THE UPPER  
30S. THIS SUPPORTS SCT SHOWERS/T-STORMS DEVELOPING ACROSS  
INTERIOR MA MID/LATE AFTERNOON. GIVEN 0-6KM SHEAR INCREASING TO  
35-40 KT, A FEW STRONG TO SEVERE STORMS ARE POSSIBLE BUT HI-RES  
CAMS INDICATE SOMEWHAT LIMITED AREAL COVERAGE SO NOT LOOKING AT  
A WIDESPREAD EVENT. STEEP LOW LEVEL LAPSE RATES AND LARGE T-TD  
SPREAD WITH INVERTED V SOUNDING PROFILE SUGGEST STRONG WINDS  
WILL BE THE PRIMARY THREAT, BUT HAIL ALSO A THREAT IN THE  
STRONGER CORES. THE MAIN SEVERE THREAT WILL BE ACROSS NORTHERN  
AND WESTERN MA BETWEEN 4-8 PM.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/
 
 
TONIGHT...  
 
AXIS OF DEEP MOISTURE AND KI INTO THE UPPER 30S HOLD TOGETHER AS  
FRONT DROPS SOUTH ACROSS SNE. THIS COMBINED WITH LOW LEVEL  
CONVERGENCE AND ELEVATED INSTABILITY WILL BE ENOUGH FOR  
SCATTERED SHOWERS AND A FEW T-STORMS MOVING SOUTH ACROSS SNE.  
TROPICAL PWATS ASSOCD WITH CHRIS EXPECTED TO REMAIN OFFSHORE.  
WARM EVENING, TEMPS COOLING INT THE 60S OVERNIGHT.  
 
WEDNESDAY...  
 
COLD FRONT WILL BE NEAR THE SOUTH COAST BY MORNING AND SLOWLY  
MOVING SOUTH. AT 12Z, DEEPER MOISTURE AND INSTABILITY AXIS  
HANGING ACROSS SE NEW ENG WHERE A FEW SHOWERS OR A T-STORM MAY  
LINGER INTO THE MORNING BEFORE DRYING OUT. MID LEVEL TROUGH  
PASSAGE WILL INDUCE AN INVERTED TROUGH WHICH WILL HAVE TO BE  
MONITORED FOR THE POSSIBILITY OF A FEW SHOWERS IN THE INTERIOR.  
OTHERWISE, MAINLY DRY CONDITIONS. LOW LEVEL EASTERLY FLOW IN  
POST-FRONTAL AIRMASS WILL RESULT IN A COOLER, ESPECIALLY ACROSS  
EASTERN MA. HIGHS WILL RANGE FROM THE MID 70S EAST COASTAL MA TO  
MID 80S IN THE CT VALLEY.  
 
TROPICAL STORM CHRIS IS EXPECTED TO BE A HURRICANE AS IT TRACKS  
OVER 300 MILES SOUTH OF NANTUCKET SO ONLY IMPACTS WILL BE HIGH  
SURF AND DANGEROUS RIP CURRENTS ALONG SOUTH COASTAL BEACHES.  
HIGH SURF ADVISORIES MAY BE NEEDED.  
 

 
   
LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/
 
 
HIGHLIGHTS...  
 
* MAINLY DRY THU/FRI WITH SEASONABLE TEMPS AND COMFORTABLE HUMIDITY  
 
* HOT WEATHER RETURNS LATE THIS WEEKEND INTO EARLY NEXT WEEK AND  
WHILE A FEW T-STORMS ARE POSSIBLE DRY WEATHER SHOULD DOMINATE  
 
DETAILS...  
 
THURSDAY AND FRIDAY...  
 
DISTANT TROPICAL SYSTEM CHRIS WELL EAST OF THE BENCHMARK WED EVENING  
WILL RAPIDLY MOVE NORTHEAST AND BE LOCATED EAST OF THE CANADIAN  
MARITIMES BY THU. THIS SHOULD ALLOW LINGERING SOUTHEAST SWELL/RIP  
CURRENT RISK THU TO DIMINISH BY FRI. OTHERWISE...HIGH PRESSURE TO  
OUR NORTH WILL RESULT IN MAINLY DRY WEATHER ALTHOUGH A SPOT SHOWER  
CAN NOT BE RULED OUT THU WITH A MOISTURE STARVED SHORTWAVE.  
SEASONABLE TEMPERATURES WITH COMFORTABLE HUMIDITY LEVELS ON TAP FOR  
THE REGION ON BOTH THU AND FRI.  
 
THIS WEEKEND INTO EARLY NEXT WEEK...  
 
UPPER TROUGH WILL EXIT THE REGION THIS WEEKEND ALLOWING FOR RISING  
HEIGHT FIELDS INTO EARLY NEXT WEEK. THE RESULT WILL BE THE RETURN  
TO HOT AFTERNOONS AT LEAST AWAY FROM ANY MARINE INFLUENCES ON THE  
IMMEDIATE COAST. CERTAINLY THE POTENTIAL FOR A COUPLE DAYS OF 90+  
DEGREE HEAT. SYNOPTIC SCALE FORCING DOES NOT LOOK FAVORABLE FOR  
MUCH PRECIPITATION...BUT CAN NOT RULE OUT A FEW T-STORMS. TIMING OF  
THAT RISK IS HIGHLY UNCERTAIN AND REGARDLESS THE VAST MAJORITY OF  
THIS PERIOD WILL LIKELY FEATURE DRY WEATHER.  
 

 
   
AVIATION /07Z TUESDAY THROUGH SATURDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH WEDNESDAY/...HIGH CONFIDENCE.  
 
TODAY...  
VFR. SCATTERED SHOWERS/T-STORMS DEVELOPING AFTER 20Z ACROSS  
INTERIOR MA. BRIEF MVFR CONDITIONS AND GUSTY WINDS POSSIBLE IN  
ANY T-STORMS.  
 
TONIGHT...  
SCATTERED SHOWERS/T-STORMS MOVING SOUTH ACROSS SNE. MAINLY VFR,  
BUT BRIEF MVFR POSSIBLE IN SHOWERS/T-STORMS. WINDS SHIFTING TO  
NORTH.  
 
WEDNESDAY...  
MAINLY VFR. A FEW MORNING SHOWERS MAY LINGER ACROSS SE NEW ENG.  
 
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.  
 
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.  
 
OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/...  
 
WEDNESDAY NIGHT: VFR.  
 
THURSDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. SLIGHT CHANCE  
SHRA.  
 
THURSDAY NIGHT THROUGH FRIDAY NIGHT: VFR.  
 
SATURDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. SLIGHT CHANCE  
SHRA.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH WEDNESDAY/...HIGH CONFIDENCE.  
 
INCREASING SW FLOW TODAY WITH GUSTS TO 20 KT BUT SEAS EXPECTED  
TO REMAIN BELOW 5 FT. DIMINISHING WIND TONIGHT WITH WIND SHIFT  
TO N BEHIND THE COLD FRONT. A FEW SHOWERS AND AN ISOLD T-STORM  
POSSIBLE TONIGHT. NE WINDS 10-20 KT WED BUT THE MAIN CONCERN  
FOR MARINERS WILL BE THE INCREASING LONG PERIOD SOUTHERLY SWELL  
FROM DISTANT HURRICANE CHRIS. SEAS UP TO 7 FT POSSIBLE OVER  
SOUTHERN WATERS.  
 
OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/...  
 
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. LOCAL ROUGH SEAS.  
 
THURSDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING  
5 FT.  
 
THURSDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING  
5 FT.  
 
FRIDAY THROUGH FRIDAY NIGHT: WINDS LESS THAN 25 KT.  
 
SATURDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...AIR QUALITY ALERT FROM 11 AM THIS MORNING TO 11 PM EDT THIS  
EVENING FOR MAZ013-016>023.  
RI...AIR QUALITY ALERT FROM 11 AM THIS MORNING TO 11 PM EDT THIS  
EVENING FOR RIZ001>008.  
MARINE...NONE.  
 

 
 

 
SYNOPSIS...KJC/FRANK  
NEAR TERM...KJC  
SHORT TERM...KJC  
LONG TERM...FRANK  
AVIATION...KJC/FRANK  
MARINE...KJC/FRANK  
 
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