409  
FXUS61 KBOX 201427  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
1027 AM EDT SAT APR 20 2019  
   
SYNOPSIS
 
 
LOW PRESSURE SYSTEM WILL SLOWLY SHIFT NORTHEAST FROM THE OHIO  
VALLEY, BRINGING SHOWERS WITH LOCALLY HEAVY RAINFALL INTO THIS  
EVENING. THE LOW PRESSURE WILL LINGER ACROSS NEW ENGLAND INTO  
EARLY NEXT WEEK. OFF AND ON RAIN CHANCES THROUGH WEDNESDAY,  
PERHAPS A DRYING TREND FOR LATE WEEK.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
10 AM UPDATE...  
 
FIRST AREA OF SHOWERS, SOME WITH EMBEDDED HEAVY RAINS, LIES  
ACROSS MOST OF MASSACHUSETTS, MAINLY ON EITHER SIDE OF THE MASS  
PIKE AS SEEN ON THE 14Z NE REGIONAL 88D RADAR IMAGERY. BRIEF  
BAND OF LIGHT RAIN CONTINUES ACROSS CT INTO RI, WITH SPOTTY  
SHOWERS AND SOME PATCHY DRIZZLE ACROSS THE S COAST, CAPE COD  
AND THE ISLANDS. HAVE HAD REPORTS OF 0.4 INCHES BETWEEN 13Z  
AND 14Z AT BOTH KBDL AND KBAF AS WELL.  
 
ANOTHER AREA OF HEAVY RAIN OFF THE COASTS OF S NJ/DELMARVA  
PENINSULA, WHICH WILL PUSH N-NE, WHILE THE FORWARD MOTION OF  
THIS RAIN WILL SHIFT SLOWLY E. SO, COULD HEAR A FEW RUMBLES OF  
THUNDER ACROSS CENTRAL AND WESTERN AREAS, ALONG WITH LOCALLY  
HEAVY RAINFALL THAT MAY CAUSE STREET/POOR DRAINAGE FLOODING IN  
NORMALLY PRONE AREAS.  
 
AGREE WITH PREVIOUS FORECASTER THAT, AS THE HIGHEST DEEP  
MOISTURE PLUME SHIFTS E WITH THE SHORT WAVE, SHOULD SEE LIGHT  
PRECIP CONTINUE BUT THE HEAVY BANDS SHOULD ALSO SHIFT E DURING  
THE AFTERNOON/EVENING HOURS.  
 
PREVIOUS DISCUSSION...  
 
HIGH AMPLITUDE TROUGH TO THE WEST WITH MID LEVEL LOW DRIFTING  
TO THE OHIO VALLEY TODAY. DOWNSTREAM MERIDIONAL FLOW INTO NEW  
ENG WILL SET UP AN ANOMALOUS 3-4SD PWAT AND LOW LEVEL WIND AXIS  
WHICH WHICH WILL SUPPORT NUMEROUS SHOWERS WITH LOCALLY HEAVY  
RAINFALL TODAY. MODELS ARE SHOWING SOME ELEVATED CAPE TODAY SO  
ISOLD T-STORMS ALSO POSSIBLE.  
 
WILL SEE ADDITIONAL CONVECTION FIRE OFF THE NJ AND DELMARVA  
COASTS AS IT LIFTS NORTH INTO SNE. THE AXIS OF HEAVIER RAIN IS  
CURRENTLY FAIRLY WELL ALIGNED WITH THE LOW LEVEL JET WHICH  
SLOWLY SHIFTS EAST DURING THE DAY. AS A RESULT, THE FOCUS FOR  
SHOWERS AND HEAVY RAINFALL SHOULD SLOWLY SHIFT EAST TO EASTERN  
NEW ENG DURING THE AFTERNOON WHILE THE SHOWERS BECOME MORE  
SCATTERED ACROSS THE WEST.  
 
LOW LEVEL JET ACROSS SNE WILL RESULT IN MORE GUSTY WINDS TODAY.  
HOWEVER, TEMPS WILL BE A BIT COOLER TODAY WITH BL MIXING NOT AS  
ROBUST SO GUSTS SHOULD NOT BE AS STRONG AS YESTERDAY. EXPECTING  
OCCASIONAL GUSTS 30-40 MPH. HIGHS WILL REACH UPPER 60S TO LOWER  
70S, EXCEPT 60-65 ALONG THE IMMEDIATE SOUTH COAST WHERE AREAS  
OF FOG MAY PERSIST.  
 
FLOOD WATCHES WILL CONTINUE FOR WESTERN HALF OF SNE WHERE  
HEAVIEST RAINFALL EXPECTED. TOTAL RAINFALL OF 1-2 INCHES  
EXPECTED IN THE FLOOD WATCH AREA WITH LOCALLY UP TO 3 INCHES  
POSSIBLE.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/
 
 
TONIGHT...  
 
LOW LEVEL JET AND MOISTURE AXIS IS FOCUSED ACROSS EASTERN NEW  
ENG WHERE NUMEROUS SHOWERS WILL CONTINUE THROUGH THE EVENING  
BEFORE BECOMING MORE SCATTERED OVERNIGHT. BUT RAINFALL  
INTENSITY WILL DIMINISH AS THE LOW LEVEL JET WEAKENS. IN  
WESTERN NEW ENG, THE THREAT OF SCATTERED SHOWERS WILL CONTINUE  
BUT SOME MID LEVEL DRYING MOVES IN FROM THE WEST WHICH WILL  
LEAD TO LESS COVERAGE OF SHOWERS.  
 
DIMINISHING WINDS EXPECTED DURING THE NIGHT WITH TEMPS FALLING  
INTO THE LOW/MID 50S BY DAYBREAK.  
 
SUNDAY...  
 
MID LEVEL LOW REMAINS WEST OF NEW ENG WITH DEEP SOUTHERLY FLOW  
CONTINUING. HOWEVER, SOMEWHAT DRIER AIR WRAPS AROUND THE LOW  
AND MOVES INTO NEW ENG WHILE MAIN PWAT AXIS MOVES OFFSHORE. THE  
RISK OF SHOWERS WILL CONTINUE, ESPECIALLY EASTERN NEW ENG  
ALTHOUGH THERE WILL BE DRY PERIODS AS WELL AND SOME BREAKS OF  
SUNSHINE WILL BE POSSIBLE IN THE INTERIOR. HIGHS WILL REACH  
MID/UPPER 60S, COOLER SOUTH COAST.  
 

 
   
LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
 
 
HIGHLIGHTS ...  
 
* SHOWERS AND COOLER CONDITIONS CONTINUE MONDAY INTO TUESDAY  
* BRIEF BREAK POSSIBLE TUESDAY BEFORE RAIN CHANCES RETURN OVERNIGHT  
INTO WEDNESDAY  
* COOLER WITH SHOWER CHANCES LATE WEEK  
 
MONDAY AND TUESDAY...  
 
ONCE AGAIN WE SEE THE SLOWING EXIT OF AN AMPLIFIED CUTOFF LOW OVER  
DELMARVA SUNDAY NIGHT. THE UPPER LOW LANGUISHES OVER OVER THE  
REGION, STRUGGLING TO RE-ENTER THE STEERING FLOW, AND APPROACHES  
SOUTHERN NEW ENGLAND MONDAY NIGHT. IT FINALLY EXITS TO THE EAST  
AROUND MORNING/MID DAY TUESDAY. DURING THE MONDAY MORNING TO EARLY-  
MID TUESDAY PERIOD WE'LL SEE THE RETURN OF WIDESPREAD RAIN CHANCES  
WITH SOME CONVECTION POSSIBLE ON MONDAY AFTERNOON/EVENING. WE SEE A  
SECONDARY SURFACE LOW FORM ALONG THE FRONTAL BOUNDARY TO OUR SOUTH  
MONDAY MORNING WHICH PROCEEDS TO MEANDER NORTHWARD OVER THE REGION  
DURING THE DAY. AT THE SAME TIME WE HAVE A GOOD SOURCE OF MOISUTRE AS  
THE PLUME OF HIGH PWATS WRAPS BACK AROUND THE UPPER LOW AND OVER  
SNE. WE COULD GET SOME GOOD RAIN OUT OF THIS SYSTEM WITH 0.5-1" OF  
RAIN POSSIBLE FROM MONDAY MORNING TO TUESDAY MORNING. UNDER THE  
500MB COLD POOL LAPSE RATES STEEPEN AS WELL AND COULD ALLOW FOR SOME  
CONVECTION AS WELL. TEMPERATURES ARE A BIT COOLER THAN WE SAW OVER  
THE WEEKEND UNDER SAID COLD POOL, REACHING INTO THE 60S. TUESDAY WE  
MAY BE ABLE TO GET INTO THE UPPER 60 OR 70S IN SPOTS IF WE CAN GET  
ENOUGH BREAKS OF SUN DURING PEAK HEATING HOURS.  
 
WEDNESDAY THROUGH FRIDAY...  
 
A VERY PROGRESSIVE PATTERN SETS UP MID-LATE WEEK WITH SEVERAL  
SHORTWAVES DIPPING THROUGH A BROAD EASTERN US TROUGH. THIS COMES  
WITH BELOW AVERAGE CONFIDENCE IN TIMING OF THE INDIVIDUAL WAVES AS  
MODELS HAVE STRUGGLED THE LAST SEVERAL RUNS TO COME TO ANY SORT OF  
CONSENSUS. AS THESE SHORTWAVES MOVE THROUGH, AT THE SURFACE WE SEE A  
COUPLE OF DISTINCT LOW CENTERS CROSSING SNE BRINGING RAIN CHANCES  
THROUGH THE ENTIRE FORECAST PERIOD. AS IS TO BE EXPECTED, HIGHEST  
CONFIDENCE COMES WITH THE EARLIEST OF THESE SYSTEMS WHICH MOVES  
THROUGH AROUND LATE TUESDAY NIGHT/WEDNESDAY. MOVING FROM THE GREAT  
LAKES REGION A LOW CROSSES NORTHERN NEW ENGLAND DRAGGING A WARM  
FRONT THROUGH LATE TUESDAY NIGHT FOLLOWED BY A COLD FRONT LATER  
WEDNESDAY. WITH THIS, RAIN RETURNS MUCH OF WEDNESDAY WITH SLIGHTLY  
COOLER TEMPERATURES. BEYOND WEDNESDAY TIMING IS UNCERTAIN BUT  
PERIODIC RAIN CHANCES CONTINUE WITH NOTICEABLY COOLER TEMPERATURES.  
 

 
   
AVIATION /14Z SATURDAY THROUGH WEDNESDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH SUNDAY/...MODERATE CONFIDENCE.  
 
THROUGH THIS AFTERNOON...  
WIDESPREAD IFR-MVFR CONDITIONS WITH NUMEROUS SHRA/+SHRA AND  
ISOLD THUNDER WILL PUSH INTO CENTRAL AND WESTERN NEW ENG BY  
AROUND 17Z, THEN GRADUALLY SHIFTS TO RI AND EASTERN MA THROUGH  
THE REMAINDER OF THE DAY. AREAS OF LIFR CIGS/FOG ALONG THE  
IMMEDIATE SOUTH COAST. CONTINUED LLWS SOUTH COAST. S-SW GUSTS  
TO 30-35 KT.  
 
TONIGHT...  
IFR/MVFR CONDITIONS WITH NUMEROUS SHOWERS, MAINLY ACROSS  
EASTERN NEW ENG. PATCHY FOG NEAR THE COAST. SLOW IMPROVEMENT  
IN THE WEST. DIMINISHING WINDS.  
 
SUNDAY...  
VFR/MVFR CIGS WITH SCT SHOWERS, ESPECIALLY EASTERN NEW ENG.  
 
KBOS TERMINAL...MODERATE CONFIDENCE IN TAF  
 
KBDL TERMINAL...MODERATE CONFIDENCE IN TAF.  
 
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...  
 
SUNDAY NIGHT: MAINLY VFR, WITH AREAS MVFR POSSIBLE. CHANCE  
SHRA.  
 
MONDAY: MAINLY VFR, WITH AREAS MVFR POSSIBLE. CHANCE SHRA,  
ISOLATED TSRA.  
 
MONDAY NIGHT: MAINLY VFR, WITH AREAS MVFR POSSIBLE. CHANCE  
SHRA.  
 
TUESDAY: MAINLY VFR, WITH AREAS MVFR POSSIBLE. SLIGHT CHANCE  
SHRA.  
 
TUESDAY NIGHT: MAINLY VFR, WITH AREAS MVFR POSSIBLE. CHANCE  
SHRA.  
 
WEDNESDAY: 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 SUNDAY/...HIGH CONFIDENCE.  
 
THIS AFTERNOON...  
GUSTY SOUTH WINDS AS LOW LEVEL JET REMAINS ACROSS THE WATERS.  
GUSTS UP TO 30-35 KT HAVE BEEN REPORTED FROM THE S COAST  
FERRIES AT MID MORNING, AND SHOULD CONTINUE THROUGH THE  
AFTERNOON. GALE WARNINGS CONTINUE FOR THE SOUTH COASTAL  
NEARSHORE WATERS. REDUCED VSBYS IN FOG OVER SOUTH COASTAL  
WATERS. NUMEROUS SHOWERS MOVING ACROSS THE WATERS REACHING  
EASTERN MA WATERS THROUGH THE REMAINDER OF THE DAY.  
 
TONIGHT...  
UP TO 30 KT GUSTS IN THE EVENING, THEN WINDS SLOWLY DIMINISH  
DURING THE NIGHT. SHOWERS CONTINUE ALONG WITH PATCHY FOG.  
 
SUNDAY...  
SOUTHERLY WINDS BELOW 15 KT BUT ROUGH SEAS PERSIST OVER SOUTHERN  
WATERS.  
 
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...  
 
SUNDAY NIGHT: WINDS LESS THAN 25 KT. ROUGH SEAS UP TO 10 FT.  
CHANCE OF RAIN SHOWERS.  
 
MONDAY: WINDS LESS THAN 25 KT. ROUGH SEAS UP TO 9 FT. CHANCE OF  
RAIN SHOWERS.  
 
MONDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF ROUGH SEAS.  
CHANCE OF RAIN SHOWERS.  
 
TUESDAY THROUGH TUESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP  
TO 5 FT. CHANCE OF RAIN SHOWERS.  
 
WEDNESDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. SLIGHT  
CHANCE OF RAIN SHOWERS.  
 

 
   
TIDES/COASTAL FLOODING
 
 
ONLY MINIMAL TIDAL DEPARTURES WERE NOTED DURING LAST EVENINGS  
HIGH TIDE ALONG THE SOUTH COAST. TIDAL DEPARTURES FOR SATURDAY  
NIGHTS HIGH TIDE SHOULD REMAIN LESS THAN 1 FT. GIVEN THAT  
ASTRONOMICAL TIDES ARE A BIT LESS THAN LAST EVENING, NOT  
EXPECTING MUCH IF ANY INUNDATION ISSUES.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR CTZ002>004.  
MA...FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR MAZ002>004-008>012.  
RI...NONE.  
MARINE...GALE WARNING UNTIL 6 PM EDT THIS EVENING FOR ANZ232>237.  
SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ230-  
251.  
SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ231-250-  
254>256.  
 

 
 

 
SYNOPSIS...KJC/BW  
NEAR TERM...EVT/BW  
SHORT TERM...KJC  
LONG TERM...BW  
AVIATION...KJC/EVT/BW  
MARINE...KJC/EVT/BW  
TIDES/COASTAL FLOODING...  
 
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