370  
FXUS61 KBOX 220825  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
425 AM EDT FRI JUN 22 2018  
   
SYNOPSIS
 
 
A COLD FRONT WILL PUSH OFF THE SOUTH COAST OF NEW ENGLAND THIS  
MORNING, BRINGING DRY AND SEASONABLE CONDITIONS AS HIGH PRESSURE  
BUILDS ACROSS. PATCHY FOG MAY REDEVELOP ALONG SOUTH COASTAL  
AREAS TONIGHT. UNSETTLED WEATHER IS EXPECTED AT TIMES THIS  
WEEKEND, ESPECIALLY ON SUNDAY, WHEN THE GREATEST RISK FOR WET  
WEATHER SHOULD BE. DRY WITH SEASONABLE SUMMER TEMPERATURES  
SHOULD RETURN BY MONDAY OR MONDAY NIGHT, DEPENDING ON TIMING OF  
A COLD FRONT. SEASONABLE WARMTH WITH DRY WEATHER EXPECTED BOTH  
TUESDAY AND WEDNESDAY.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
DEWPTS HAVE BEEN STEADILY LOWERING OVER THE LAST FEW HOURS  
ACROSS CENTRAL AND SOUTHERN AREAS AS THE COLD FRONT PUSHES S  
EARLY THIS MORNING. NOTING DEWPT READINGS DOWN TO THE 40S ACROSS  
THE CT VALLEY INTO N CENTRAL AND NE MASS AT 07Z, WHILE THEY  
REMAIN IN THE LOWER 60S ALONG S COASTAL AREAS WHERE FOG LINGERS.  
HOWEVER, LATEST TRENDS ON THE GOES-EAST NIGHT FOG PRODUCT  
SHOWING THE DRIER AIR WORKING IN AS LIGHT N-NE WINDS DEVELOP.  
GOES-EAST NIGHT FOG AND RGB NIGHTTIME MICROPHYSICS PRODUCTS AS  
WELL AS OBSERVATIONS SIGNALING CLEAR SKIES FROM ABOUT THE ROUTE  
44 AREA NORTHWARD. EXPECT TEMPS TO BOTTOM OUT FROM THE MID AND  
UPPER 40S ACROSS N CENTRAL AND NW MASS AS WELL AS THE NORMALLY  
COOLER VALLEY LOCATIONS TO NEAR 60 IN THE URBAN CENTERS.  
 
AS FOR TODAY, HIGH PRESSURE WILL BUILD SOUTH OUT OF SOUTHERN  
QUEBEC THROUGH NORTHERN NEW ENGLAND TODAY. THIS WILL ALLOW E-NE  
WINDS TO FRESHEN ACROSS SOUTH COASTAL AREAS AND THE NEARBY  
WATERS AS THE PRES GRADIENT GRADUALLY INCREASES BETWEEN THE HIGH  
AND LOW PRESSURE ACROSS THE MID ATLC STATES INTO THE OHIO  
VALLEY.  
 
CLOUDS MAY LINGER ALONG THE S COAST THROUGH MIDDAY BEFORE MOVING  
OFFSHORE. EXPECT MOSTLY SUNNY CONDITIONS WITH TEMPS RECOVERING  
TO THE MID 70S TO AROUND 80 AWAY FROM THE E COAST WHERE ONSHORE  
WINDS WILL KEEP TEMPS COOLER, MAINLY IN THE MID 60S ON THE OUTER  
CAPE TO AROUND 70 FROM MARSHFIELD TO BOSTON AND BEVERLY.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/
 
 
TONIGHT...  
THE HIGH ACROSS MAINE INTO THE MARITIMES WILL HOLD IN PLACE  
THROUGH MOST OF THE NIGHT. WINDS WILL SHIFT TO SE, WHICH WILL  
KEEP LOW LEVEL MOISTURE WORKING IN ACROSS COASTAL AREAS. MAY SEE  
PATCHY FOG REDEVELOP ACROSS S COASTAL AREAS OVERNIGHT.  
 
WITH THE RIDGE AXIS REMAINING ACROSS THE REGION, SOME QUESTION  
AS TO WHETHER ANY SHOWERS MAY MOVE IN AFTER MIDNIGHT. 00Z MODELS  
HAVE VARYING TIMING WITH THE ONSET OF THE PRECIP AS LOW  
PRESSURE SHIFTS E INTO OHIO/W PA OVERNIGHT. HAVE CARRIED CHC  
POPS OVERNIGHT TONIGHT, BUT LOWER THAN AVERAGE CONFIDENCE DUE TO  
WIDENED MODEL SOLUTION TIMING.  
 
SATURDAY...  
THE E-W ORIENTED RIDGE PUSHES EASTWARD EARLY SATURDAY. MOST  
MODELS SIGNALING RAIN THROUGH THE DAY. THE ECMWF AND CANADIAN  
GGEM TRYING TO BRING IN SOME BANDS OF HEAVIER RAINFALL ALONG  
WITH SOME INSTABILITY, WITH K INDICES IN THE LOWER-MID 30S AND  
SLIS LOWER TO BELOW ZERO MAINLY NEAR AND S OF THE MASS PIKE SAT  
AFTERNOON. HOWEVER, A CONTINUED E-SE WIND FLOW OFF THE COOLER  
OCEAN WATERS SHOULD BE A STABILIZING INFLUENCE SO DID NOT  
MENTION THUNDER AT THIS POINT. TEMPS WILL BE AROUND 10 DEGREES  
BELOW SEASONAL NORMALS, ONLY REACHING THE MID 60S TO LOWER 70S.  
 

 
   
LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/
 
 
HIGHLIGHTS...  
 
* WARMER WITH SCATTERED SHOWERS/THUNDERSTORMS ON SUNDAY  
* MAINLY DRY WITH SEASONABLE SUMMER WARMTH TUE AND WED  
* MORE SHOWERS POSSIBLE TOWARDS THE END OF NEXT WEEK  
 
DETAILS...  
 
SATURDAY NIGHT...  
LOW PRESSURE MOVING FROM THE GREAT LAKES ACROSS NORTHERN NEW  
ENGLAND SHOULD PUSH A COLD FRONT THROUGH SOUTHERN NEW ENGLAND  
LATE. SCATTERED SHOWERS, WITH A FEW THUNDERSTORMS, REMAIN  
POSSIBLE.  
 
SUNDAY...  
 
THE GREATEST RISK FOR SHOWERS AND THUNDERSTORMS REMAINS SUNDAY,  
AHEAD OF A SECONDARY COLD FRONT. AMOUNT OF FORECAST INSTABILITY  
DOES NOT APPEAR TO BE SUBSTANTIAL, BUT MID LEVEL LAPSE RATES  
COULD BE DECENT. WILL NEED TO MONITOR CHANGES TO THUNDERSTORM  
POTENTIAL SUNDAY.  
 
MONDAY...  
 
IMPRESSIVE COLD POOL ALOFT/SHORTWAVE PASSES BY OUR REGION. GFS  
IS THE MOST AGGRESSIVE LINGERING LIFT AND MOISTURE BEHIND A  
COLD FRONT. ECMWF AND CANADIAN QUITE A BIT DRIER, BUT CONSISTENT  
WITH PRIOR RUNS. IT'S STILL REALLY A QUESTION OF HOW QUICKLY  
THE DRIER AIR ARRIVES BEHIND A SECONDARY COLD FRONT. GIVEN THE  
PROXIMITY OF A COLD POOL ALOFT, WILL KEEP AT LEAST A MENTION OF  
LINGERING SHOWERS EARLY.  
 
TUESDAY THROUGH THURSDAY...  
 
HIGH PRESSURE PASSING TO OUR SOUTH WILL KEEP OUR WEATHER MAINLY DRY  
TUESDAY AND WEDNESDAY. AN APPROACHING WARM FRONT COULD BRING A  
FEW SHOWERS BY THURSDAY.  
 

 
   
AVIATION /08Z FRIDAY THROUGH TUESDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH SATURDAY/...HIGH CONFIDENCE.  
 
THROUGH 12Z...PATCHY FOG WITH MVFR-IFR CIGS/VSBYS ALONG S  
COASTAL TERMINALS. MAY SEE LOCAL LIFR VSBYS ACROSS THE OUTER  
CAPE AND ISLANDS. OTHERWISE, VFR CONDITIONS.  
 
TODAY...MVFR-IFR CONDITIONS MAY LINGER ACROSS THE OUTER CAPE AND  
IMMEDIATE S COAST UNTIL AROUND 13Z BEFORE IMPROVING, THOUGH LOW  
CLOUDS MAY LINGER NEAR KACK THROUGH MID MORNING OR SO.  
OTHERWISE, EXPECT VFR CONDITIONS.  
 
TONIGHT...PATCHY FOG MAY SKIRT NEAR KACK, KMVY AND KBID  
OVERNIGHT WITH LOCAL MVFR-IFR CONDITIONS AT TIMES. OTHERWISE,  
VFR. SCATTERED -SHRA MAY MOVE INTO THE S COAST AFTER 06Z, THEN  
MOVE STEADILY N-NE TO ABOUT THE MASS PIKE BY 12Z.  
 
SATURDAY...SCATTERED -SHRA CONTINUE ACROSS THE REGION WITH  
MAINLY VFR CONDITIONS. PATCHY FOG MAY BRING MVFR-IFR CIGS/VSBYS  
ALONG THE S COAST THROUGH MOST OF THE DAY, SLOWLY PUSHING N  
ACROSS RI/SE MASS AFTER 18Z.  
 
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.  
 
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.  
 
OUTLOOK /SATURDAY NIGHT THROUGH TUESDAY/...MODERATE CONFIDENCE.  
 
SATURDAY NIGHT: MAINLY IFR, WITH LOCAL MVFR POSSIBLE. CHANCE  
SHRA, ISOLATED TSRA, PATCHY FG.  
 
SUNDAY: MAINLY VFR, WITH LOCAL IFR POSSIBLE. CHANCE SHRA,  
ISOLATED TSRA, PATCHY FG.  
 
SUNDAY NIGHT: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. CHANCE  
SHRA, ISOLATED TSRA.  
 
MONDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. BREEZY.  
 
MONDAY NIGHT: VFR. BREEZY.  
 
TUESDAY: VFR.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH SATURDAY/...HIGH CONFIDENCE.  
 
TODAY...WINDS SHIFT TO FROM N-NE TO EASTERLY DURING THE DAY.  
MAY SEE GUSTS UP TO 20 KT ON THE SOUTHERN OUTER WATERS THIS  
AFTERNOON. SEAS REMAIN BELOW 5 FT. VISIBILITY RESTRICTIONS IN  
PATCHY FOG SHOULD IMPROVE BY AROUND MID MORNING OR SO.  
 
TONIGHT AND SATURDAY...E-SE WINDS IN PLACE. A FEW GUSTS UP TO  
25 KT ON THE SOUTHERN OUTER WATERS LATE TONIGHT INTO EARLY SAT.  
VISIBILITY RESTRICTION IN PATCHY FOG ALONG THE SOUTHERN WATERS  
LATE TONIGHT, THEN IN SHOWERS AND PATCHY FOG MOVING IN FROM S-N  
DURING SAT.  
 
OUTLOOK /SATURDAY NIGHT THROUGH TUESDAY/...MODERATE CONFIDENCE.  
 
SATURDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS  
APPROACHING 5 FT. CHANCE OF RAIN SHOWERS, WITH ISOLATED  
THUNDERSTORMS. PATCHY FOG. AREAS OF VISIBILITY 1 NM OR LESS.  
 
SUNDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING 5 FT.  
SLIGHT CHANCE OF RAIN SHOWERS, WITH ISOLATED THUNDERSTORMS.  
PATCHY FOG. AREAS OF VISIBILITY 1 NM OR LESS.  
 
SUNDAY NIGHT: WINDS LESS THAN 25 KT. LOCAL ROUGH SEAS. SLIGHT  
CHANCE OF RAIN SHOWERS, WITH ISOLATED THUNDERSTORMS.  
 
MONDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT.  
 
MONDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF ROUGH SEAS.  
 
TUESDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING 5 FT.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...NONE.  
RI...NONE.  
MARINE...NONE.  
 

 
 

 
SYNOPSIS...BELK/EVT  
NEAR TERM...EVT  
SHORT TERM...BELK/EVT  
LONG TERM...BELK  
AVIATION...BELK/EVT  
MARINE...BELK/EVT  
 
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