568  
FXUS61 KBOX 231058  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
658 AM EDT TUE JUL 23 2019  
   
SYNOPSIS
 
 
ANOTHER ROUND OF SHOWERS AND EMBEDDED THUNDERSTORMS IMPACT THE  
REGION THIS MORNING INTO EARLY THIS AFTERNOON, FOCUSED ACROSS  
RHODE ISLAND AND SOUTHEAST MASSACHUSETTS. LINGERING SHOWERS ARE  
EXPECTED TONIGHT INTO EARLY WEDNESDAY ACROSS THE SOUTHEAST NEW  
ENGLAND COAST. MOSTLY DRY, SEASONABLE WEATHER LATE WEEK INTO  
THE WEEKEND, WITH A RETURN OF MORE SUBSTANTIAL HEAT AND HUMIDITY  
EARLY NEXT WEEK. POTENTIAL WASH OUT OF THE MUGGINESS LATE NEXT  
WEEK.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
*/ HIGHLIGHTS ...  
 
- FLASH FLOOD WATCH INTO EARLY AFTERNOON ACROSS RI/SE MA  
 
*/ DISCUSSION (7 AM UPDATE, NO MAJOR CHANGES) ...  
 
THE MAIN ISSUE WILL BE ANOTHER BATCH OF HEAVY SHOWERS AND EMBEDDED  
THUNDERSTORMS EXPECTED TO IMPACT PORTIONS OF RI AND SE MA THIS  
MORNING. THIS ACTIVITY MAY LINGER INTO EARLY AFTERNOON ACROSS THE  
CAPE/NANTUCKET. WE DID GO AHEAD AND ISSUE A FLASH FLOOD WATCH  
INTO EARLY AFTERNOON FOR THIS REGION, WHICH WE WILL DISCUSS IN  
GREATER DETAIL BELOW.  
 
A SURFACE BOUNDARY WAS DRAPED NEAR THE SOUTH COAST VERY EARLY THIS  
MORNING. AT THE SAME TIME, ANOTHER WAVE OF LOW PRESSURE WAS LIFTING  
NORTHEAST ALONG THE BOUNDARY TO OUR SOUTHWEST. THIS SHOULD KEEP THE  
BOUNDARY IN THE SAME GENERAL VICINITY FOR MUCH OF THE MORNING, AS  
THE WAVE RIDES ALONG IT. PWATS OF 2+ INCHES ALONG WITH UNUSUALLY  
STRONG FORCING FOR THIS TIME OF YEAR, WILL BRING THE POTENTIAL FOR  
LOCALIZED POCKETS OF TORRENTIAL RAINFALL ACROSS RI/SE MA THIS MORNING  
INTO EARLY AFTERNOON. MODEL QPF IS ALL OVER THE PLACE AND MAY BE  
TOO FAR NORTH GIVEN CONVECTIVE FEEDBACK ISSUES. SO WHILE THERE IS  
UNCERTAINTY, ENOUGH PARAMETERS ARE IN PLACE TO WARRANT A FLASH  
FLOOD WATCH ACROSS RI AND SE MA. THE MAIN THREAT WILL BE THIS  
MORNING, BUT MAY LINGER INTO THE EARLY AFTERNOON ACROSS THE CAPE /  
ISLANDS. AGAIN, THIS IS A RESULT OF HIGH PWATS, A BOUNDARY IN THE  
VICINITY WITH UNUSUALLY STRONG FORCING FOR THIS TIME OF YEAR. ACROSS  
THE REST OF THE REGION, PLENTY OF SHOWERS EXPECTED THIS MORNING BUT  
GIVEN LESS FORCING DO NOT EXPECT ANY FLOODING ISSUES.  
 
SEVERE WEATHER IS NOT EXPECTED FOR THE VAST MAJORITY OF THE REGION  
THIS MORNING/EARLY AFTERNOON GIVEN LIMITED INSTABILITY. HOWEVER,  
WE CAN NOT RULE OUT A LOW RISK ACROSS THE CAPE/ISLANDS DEPENDING  
ON WHERE THE WARM FRONT AND TRIPLE POINT SETUP.  
 
BY MID AFTERNOON, THE STEADY SHOWERS WILL HAVE EXITED THE CAPE /  
ISLANDS. HOWEVER, CLOUDS SKIES A FEW SPOT SHOWERS WILL REMAIN  
POSSIBLE. HIGHS WILL ONLY REACH THE UPPER 60S TO LOWER 70S WITH  
A BIT OF A NORTHEAST BREEZE ACROSS THE SOUTHEAST NEW ENGLAND COAST.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/
 
 
TONIGHT...  
 
THE COLD FRONT WILL BE WELL SOUTH OF OUR REGION TONIGHT. THERE  
WILL BE ANOTHER WAVE OF LOW PRESSURE, BUT THIS WILL TRACK  
FURTHER SOUTHEAST THEN THIS MORNING/S. SO THE BULK OF THE  
SHOWERS WILL BE CONFINED TO THE SOUTHEAST NEW ENGLAND COAST,  
PARTICULARLY THE CAPE/ISLANDS. ELSEWHERE, THINK DRY WEATHER IS  
ON TAP FOR TONIGHT EXCEPT FOR A SPOT SHOWER OR TWO. LOW  
TEMPERATURES WILL RANGE FROM THE UPPER 50S TO THE MIDDLE 60S.  
 

 
   
LONG TERM /WEDNESDAY THROUGH MONDAY/
 
 
*/ HIGHLIGHTS ...  
 
- COASTAL RAINS LINGERING WEDNESDAY  
- OVERALL DRY AND SEASONABLE LATE WEEK INTO THE WEEKEND  
- BUILD UP HEAT AND HUMIDITY EARLY NEXT WEEK  
- POTENTIAL LATE WEEK WASHOUT OF THE MUGGINESS  
 
*/ OVERVIEW ...  
 
BRIEF RELIEF, BUT SUMMER HEAT WILL RETURN. THE FOUR-CORNERS MONSOON  
RIDGE PERSISTING AS THE N PACIFIC PATTERN OSCILLATES EMPHASIZED BY  
POSITIVE WPO / EPO / PNA TRENDS SIGNALING AN ONSHORE FAST N PACIFIC  
JET SQUEEZED BETWEEN AK LOW N OF A NE PACIFIC HIGH. DIAGNOSING H85  
TEMPERATURES, RETURN OF WARMER THAN AVERAGE CONDITIONS ALOFT MIXING  
DOWN TO THE SURFACE BY THE END OF JULY. CONVEYOR BELT MOTIONS FROM  
THE MILD PACIFIC AND HOT DESERT SW CONUS, TRENDS COINCIDING WITH CPC  
6-10 / 8-14 DAY OUTLOOKS. FOR NOW, LINGERING H5 TROF DEAMPLIFYING  
THROUGH THE WEEK. SEASONABLE, COMFORTABLE CONDITIONS INITIALLY, A  
GRADUAL RETURN OF HEAT AND HUMIDITY WHILE MONITORING FOR UPSTREAM  
WEAK WAVE IMPULSES THROUGH THE MID-LATITUDE NEAR-FLAT FLOW INTO THE  
END OF JULY. SOME ISOLATED TO SCATTERED SHOWER CHANCES BUT THE OVER-  
ALL PATTERN LOOKING DRY WITH THE ABSENCE OF MORE POTENT MID TO UPPER  
LEVEL SYNOPTICS (LIKE THAT PRESENTLY). BREAK DOWN THE DETAILS BELOW.  
 
*/ DETAILS ...  
 
WEDNESDAY ...  
 
COASTAL RAINS LINGERING. MID-UPPER TROF AND ACCOMPANYING SYNOPTICS  
SLOW TO LIFT UP AGAINST THE N ATLANTIC RIDGE / BERMUDA HIGH. GRADUAL  
DEAMPLIFICATION AS WARMER AIR / HIGHER HEIGHTS PREVAIL OUT AHEAD OF  
ADDITIONAL MID-LATITUDE ENERGY THROUGH AN EVOLVING FLATTENING FLOW.  
CHANCE TO LIKELY POPS FURTHER SE CLOSER TO THE WEAK WAVE LOW ALONG  
THE NOW OFFSHORE COLD FRONT BENEATH H3 JET DYNAMICS ALOFT. COOLER  
AIRMASS ALOFT WHILE DRIER AIR ENTRENCHING AT THE SURFACE, LEAN WITH  
SEASONABLE TEMPERATURES AROUND THE LOW 80S, HOWEVER 2M TEMPERATURES  
EXPECTED TO BE SOMEWHAT DEPENDENT ON CLOUD COVER. WARMEST CONDITIONS  
LOOK TO OCCUR OVER W AREAS OF THE CT RIVER VALLEY. LIGHT N/W WINDS  
DESPITE THE OFFSHORE COLD FRONT, POSSIBILITY OF SEA-BREEZES ALONG  
THE COAST.  
 
THURSDAY INTO THE WEEKEND ...  
 
DRY, SEASONABLE CONDITIONS, HOWEVER CAN'T RULE OUT AN ISOLATED SPOT  
SHOWER. DESPITE DRIER CONDITIONS WITH LOW TO MID LEVEL LOW THETAE,  
FAVORABLE LAPSE RATES ALONG WITH VERY WEAK MID LEVEL IMPULSES, WITH  
ANABATIC FLOW ALONG THE HIGH TERRAIN, CAN'T RULE OUT A SPOT SHOWER.  
THE BETTER CHANCE FRIDAY AND SATURDAY, BERKSHIRES PREFERRED, HOWEVER  
LIGHT WINDS, CAN'T RULE OUT ACTIVITY ALONG MIDDAY SEA-BREEZES. LOW  
CONFIDENCE AS THERE ARE SIGNALS SUGGESTING PREVAILING SUBSIDENCE.  
HEAT AND HUMIDITY GRADUALLY REBOUNDING THROUGHOUT AS WE SEE RETURN S  
FLOW LATE.  
 
EARLY NEXT WEEK ...  
 
HEAT AND HUMIDITY CONTINUING. SUBSIDENCE RIDGE PREVAILING BETWEEN  
UPSTREAM SYNOPTICS UP AGAINST TROPICAL ENERGY CREEPING N. MAY NOT BE  
TILL THE END OF THE WEEK THAT WE'LL WASH OUT THE MUGGINESS WITH A  
SWEEPING COLD FRONT. MORE POTENT SYNOPTICS CAN ONLY BE EMPHASIZED IF  
ENERGY IS DOWNSHEARED OUT OF CANADA AHEAD OF RE-EMERGING SYNOPTICS  
OVER THE GULF OF AK. LOW CONFIDENCE FORECAST.  
 

 
   
AVIATION /12Z TUESDAY THROUGH SATURDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH TONIGHT/ ... MODERATE CONFIDENCE.  
 
12Z UPDATE ...  
 
TODAY ...  
WIDESPREAD MVFR-IFR WITH -RA, EMBEDDED RA/+RA WITH POSSIBLE TSRA,  
THE GREATER RISK OVER SE-COASTAL TERMINALS. WITH RA/+RA A GREATER  
LIKELIHOOD OF IFR PERHAPS LIFR. ACTIVITY THROUGH MID AFTERNOON.  
ACCOMPANYING BURST OF N/NE WINDS SUSTAINED AROUND 10 TO 15 KTS  
WITH GUSTS UP TO 25 KTS. SPOT SHOWERS TOWARDS EVENING.  
 
TONIGHT...  
PERHAPS SOME PARTIAL CLEARING W, HOWEVER ANOTHER BATCH OF -RA IS  
ANTICIPATED AROUND MIDNIGHT INTO THE EARLY MORNING HOURS OF  
WEDNESDAY. MVFR-IFR LINGERING ESPECIALLY ALONG AND SE OF BDL-LWM.  
BRIEF W FLOW WITH -RA TURNING N LATE.  
 
KBOS TERMINAL...MODERATE CONFIDENCE IN TAF.  
 
KBDL TERMINAL...MODERATE CONFIDENCE IN TAF.  
 
OUTLOOK /WEDNESDAY THROUGH SATURDAY/ ... HIGH CONFIDENCE.  
 
TUESDAY: MVFR/IFR CONDITIONS POSSIBLE. BREEZY. WIDESPREAD SHRA,  
PATCHY BR.  
 
TUESDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. SLIGHT  
CHANCE SHRA.  
 
WEDNESDAY: VFR. SLIGHT CHANCE SHRA.  
 
WEDNESDAY NIGHT THROUGH SATURDAY: VFR.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH TONIGHT/...HIGH CONFIDENCE.  
 
TODAY...  
NORTHEAST WIND GUSTS OF 20 TO 25 KNOTS EXPECTED BEHIND THE WAVE  
OF LOW PRESSURE THIS MORNING. THIS WILL ALSO RESULT IN 3 TO 6  
FOOT SEAS BUILDING ACROSS MANY OPEN WATERS AND SCA HEADLINES ARE  
IN EFFECT FOR MANY OF OUR WATERS. THE OTHER ISSUE WILL BE HEAVY  
SHOWERS AND EMBEDDED THUNDERSTORMS THROUGH EARLY AFTERNOON. A  
FEW OF THE STORMS MAY BE STRONG ACROSS OUR SOUTHERN WATERS AND A  
WATERSPOUT CAN NOT BE RULED OUT.  
 
TONIGHT...  
NE WIND GUSTS WILL DIMINISH AS PRESSURE GRADIENT WEAKENS. HOWEVER,  
WE WILL NEED TO KEEP SMALL CRAFT HEADLINES IN EFFECT FOR OUR  
SOUTHERN WATERS AS A RESULT OF LINGERING SEAS.  
 
OUTLOOK /WEDNESDAY THROUGH SATURDAY/...HIGH CONFIDENCE.  
 
TUESDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. WIDESPREAD  
RAIN SHOWERS, SCATTERED THUNDERSTORMS, PATCHY FOG. AREAS OF  
VISIBILITY 1 TO 3 NM.  
 
TUESDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING  
5 FT. CHANCE OF RAIN SHOWERS, PATCHY FOG.  
 
WEDNESDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING  
5 FT. CHANCE OF RAIN SHOWERS.  
 
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS  
APPROACHING 5 FT.  
 
THURSDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.  
 
THURSDAY NIGHT THROUGH SATURDAY: WINDS LESS THAN 25 KT.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...FLASH FLOOD WATCH UNTIL 2 PM EDT THIS AFTERNOON FOR MAZ017>024.  
RI...FLASH FLOOD WATCH UNTIL 2 PM EDT THIS AFTERNOON FOR RIZ001>008.  
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ231-  
232-250-251.  
SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 2 AM EDT  
WEDNESDAY FOR ANZ235-237.  
SMALL CRAFT ADVISORY UNTIL 2 AM EDT WEDNESDAY FOR ANZ254.  
SMALL CRAFT ADVISORY UNTIL 8 AM EDT WEDNESDAY FOR ANZ255-256.  
 

 
 

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