Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 301954 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 354 PM EDT TUE JUN 30 2015 .SYNOPSIS...
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A FRONTAL SYSTEM WILL BRING A CHANCE OF STRONG TO SEVERE SHOWERS AND THUNDERSTORMS TO THE REGION EARLY WEDNESDAY THROUGH THE AFTERNOON. THE FRONT STALLS NEAR THE SOUTH COAST INTO THURSDAY BEFORE MOVING OFFSHORE THURSDAY NIGHT. WEAK HIGH PRESSURE WILL BRING MAINLY DRY AND SEASONABLY WARM WEATHER FRIDAY INTO EARLY NEXT WEEK...BUT THERE IS A LOW RISK FOR A FEW SHOWERS ACROSS THE CAPE/ISLANDS THURSDAY NIGHT INTO FRIDAY NIGHT AS WEAK WAVES OF LOW PRESSURE TRACK TO THE SOUTH.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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AN AREA OF SHOWERS IS MOVING INTO NORTHWESTERN MASSACHUSETTS AT THIS TIME. WILL CONTINUE TO SEE A FEW SHOWERS TRACK THROUGH THIS AREA THIS AFTERNOON AS LARGER AREA OF SHOWERS MOVES NORTHEASTWARD THROUGH NEW YORK STATE AND INTO VERMONT. NOT EXPECTING ANY THUNDER WITH THIS AREA OF SHOWERS. ELSEWHERE ACROSS THE REGION...WE ARE STARTING TO SEE SOME DIURNAL CU POP UP. TEMPERATURES HAVE CLIMBED INTO THE UPPER 70S TO LOWER 80S MOST LOCATIONS...EXCEPT THE IMMEDIATE COASTLINES WHERE SEABREEZES HAVE KEPT TEMPERATURES IN THE LOW 70S. TONIGHT...DIURNAL CU WILL DIMINISH AS SURFACE HEATING IS LOST. DRY WEATHER IS EXPECTED THROUGH MUCH OF THE NIGHT. HOWEVER...PRECIP CHANCES INCREASE AGAIN TOWARDS DAWN. OVERNIGHT...INCREASED HUMIDITY /DEWPOINTS/ WILL KEEP TEMPERATURES IN THE LOWER TO MID 60S.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
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A POTENT MID LEVEL SHORTWAVE AND ITS ASSOCIATED COLD POOL ALOFT WILL APPROACH SOUTHERN NEW ENGLAND EARLY WEDNESDAY MORNING. THIS WILL LIKELY BE ENOUGH TO INITIATE SOME SHOWERS DURING THE EARLY MORNING HOURS. WHILE SURFACE INSTABILITY IS LACKING DURING THIS TIME... THERE IS SOME ELEVATED INSTABILITY WHICH WILL PROVIDE FOR SOME SCATTERED ELEVATED THUNDER WITHIN THE BROADER AREA OF SHOWERS. WHILE THERE IS STILL SOME QUESTION WITH THE EXACT TIMING OF THIS OCCURRING...MODELS DO SEEM TO BE CONVERGING ON THE 09-12Z TIME FRAME. PRECIPITABLE WATER VALUES NEAR 2.0 INCHES WEDNESDAY MORNING INTO EARLY AFTERNOON. COUPLED WITH THE STRONG LOW LEVEL JET...THIS IS A RECIPE FOR HEAVY RAINFALL WITHIN THE SHOWERS AND THUNDERSTORMS. A QUICK INCH OF RAIN IN LESS THAN AN HOUR IS NOT UNREASONABLE. THIS COULD RESULT IN POOR DRAINAGE AND URBAN FLOODING. THE BENEFIT OF THE STRONG LOW LEVEL JET IS STORMS SHOULD MOVE ALONG AT A FAIRLY GOOD SPEED. THIS WILL REDUCE THE LIKELIHOOD OF FLOODING SOMEWHAT. MAIN FLOODING THREAT WILL BE WITH ANY TRAINING THUNDERSTORMS. LATER INTO THE MORNING WEDNESDAY...THE THREAT TURNS MORE TO SEVERE WEATHER AND POTENTIAL HEAVY RAIN. AS THIS SHORTWAVE APPROACHES... THE UPPER LEVEL COLD POOL WILL INCITE STEEPER MID LEVEL LAPSE RATES. THIS INCREASES THE INSTABILITY TOWARDS THE SURFACE TO GO ALONG WITH THE ELEVATED INSTABILITY. THIS IS EVIDENT IN SBCAPES FORECAST OVER 1000 J/KG. A DECENT LOW LEVEL JET HAS PROVIDED PLENTY OF SHEAR...0- 6 KM VALUES ARE 30-50KTS AND 0-1 KM HELICITY VALUES ARE OVER 100 M2/S2. THE MAIN QUESTION SURROUNDING THIS FORECAST IS WHETHER THE INSTABILITY INCREASES BEFORE THE SHEAR DIMINISHES IN THE AFTERNOON. IF EVERYTHING LINES UP...STRONG TO SEVERE THUNDERSTORMS WITH DAMAGING WINDS AND LARGE HAIL ARE LIKELY. DEPENDING ON THE TIMING OF THE WARM FRONT MOVING NORTHWARD THROUGH THE REGION /EXPECTED TO BE EARLY WEDNESDAY AFTERNOON AT THIS TIME/ AND THE HELICITY VALUES...THERE IS ALSO POTENTIAL FOR AN ISOLATED TORNADO OR TWO.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
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HIGHLIGHTS... * MAINLY DRY AND SEASONABLY WARM THU THROUGH EARLY NEXT WEEK BUT LOW RISK OF A FEW SHOWERS CAPE/ISLANDS THU NIGHT INTO FRI NIGHT OVERVIEW... EXTENDED PERIOD STARTS WITH RATHER AMPLIFIED PATTERN FOR EARLY JULY WITH RIDGING ALONG THE WEST COAST AND ACROSS THE CENTRAL ATLC NORTHWARD TO GREENLAND WHICH RESULTS IN TROF FROM GT LAKES INTO NEW ENG LIFTING TO THE NORTH BY FRI. HOWEVER...SHORTWAVE ENERGY MOVING THROUGH W CANADA WILL SERVE TO DEAMPLIFY THE PATTERN THIS WEEKEND WITH WEAK POLAR JET SETTING UP ACROSS NORTHERN CONUS. WEAK SHORTWAVES MOVING THROUGH THE FLOW MAY BRING A WEAK MOISTURE STARVED COLD FRONT ON SAT. THEN SOME RIDGING ALOFT MAY DEVELOP ACROSS THE NE EARLY NEXT WEEK...BUT TIMING OF NEXT SHORTWAVE IS UNCERTAIN. OVERALL IT LOOKS MOSTLY DRY AND SEASONABLY WARM THIS WEEKEND INTO EARLY NEXT WEEK WITH HEAT AND HUMIDITY REMAINING WELL TO THE SOUTH. DETAILS... WED NIGHT INTO THU... A FEW LEFTOVER SHOWERS OR PERHAPS A TSTM POSSIBLE EARLY WED EVENING...OTHERWISE A DRY NIGHT EXPECTED. THE COLD WILL BE SLOWLY CROSSING THE REGION WED NIGHT...STALLING INVOF OF THE S COAST ON THU AS IT BECOMES PARALLEL TO THE UPPER LEVEL FLOW. HOWEVER...LATEST GUIDANCE INDICATES A RATHER DRY COLUMN THU WITH VERY LOW KI VALUES AND SFC INSTABILITY IS ABOUT NIL. SO EXPECTING A MAINLY DRY DAY WITH PT-MOSUNNY SKIES AND SEASONABLE TEMPS. THU NIGHT INTO FRI NIGHT... THERE IS STILL A LEVEL OF UNCERTAINTY FOR THIS PERIOD...MAINLY WITH RESPECT TO HOW FAR NORTH MOISTURE TO THE SOUTH GETS. COLD FRONT MOVES TO THE S THU NIGHT AND WEAK HIGH PRES SETTLES INTO THE REGION WHICH SHOULD BRING DRY WEATHER AND SEASONABLY WARM TEMPS FRI. HOWEVER...THERE WILL BE A SERIES OF WEAK WAVES RIDING ALONG THE BOUNDARY TO THE SOUTH WHICH WILL HAVE TO BE WATCHED. IT IS POSSIBLE A FEW SHOWERS COULD FLIRT WITH THE IMMEDIATE S COAST AND CAPE/ISLANDS THU NIGHT INTO FRI NIGHT. AT THE VERY LEAST...EXPECT MORE CLOUD COVER DURING THIS PERIOD. BUT ANY NORTH ADJUSTMENT COULD BRING A STEADIER RAIN TO CAPE/ISLANDS THU NIGHT INTO FRI. SAT THROUGH TUE... A WEAK FRONT MOVES INTO THE REGION SOMETIME SAT INTO SAT NIGHT ASSOCD WITH A NORTHERN STREAM SHORTWAVE TO THE NORTH...BUT EXPECT DRY CONDITIONS. OTHERWISE HIGH PRES BUILDS INTO THE REGION BEHIND THE FRONT SUN INTO EARLY NEXT WEEK. THERE IS UNCERTAINTY WITH TIMING OF NEXT IMPULSE WHICH WILL DETERMINE WHETHER ANY SHOWERS MOVE IN NEXT TUE. TEMPS MODERATE SUN/MON BASED ON WARMING MID LEVEL TEMPS. LOW CONFIDENCE ON TEMPS NEXT TUE.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. THROUGH 00Z...HIGH CONFIDENCE. VFR. VERY LOW CHANCE FOR A BRIEF SHOWER/T-STORM IN NW MA LATE TODAY. SEA BREEZES CONTINUE AT COASTLINES. TONIGHT...MODERATE CONFIDENCE. VFR THIS EVENING. MAY SEE SOME LOW CLOUDS DEVELOP LATE AT SOME LOCATIONS...WITH THE GREATEST RISK FOR THIS ALONG THE SOUTHEAST NEW ENGLAND COAST. MAY ALSO SEE AN AREA OF SHOWERS AND THUNDERSTORMS WORK INTO WESTERN NEW ENGLAND TOWARD DAYBREAK. CONFIDENCE IN THE TIMING AT A PARTICULAR LOCATION IS THE LOWEST CONFIDENCE PART. WEDNESDAY...HIGH PROBABILITY FOR WIDESPREAD TSRA. RISK FOR A FEW STRONG STORMS AND HEAVY RAINFALL. IFR AND MVFR CONDITIONS LIKELY IN SHRA/TSRA. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY... WED NIGHT...MODERATE CONFIDENCE. PATCHY MVFR/IFR STRATUS AND FOG DEVELOPING...OTHERWISE VFR. THU...HIGH CONFIDENCE. VFR. FRI THROUGH SUN...MODERATE CONFIDENCE. VFR. BUT STILL A BIT OF UNCERTAINTY REGARDING A SHOWER RISK ALONG THE S COAST AND CAPE/ISLANDS THU NIGHT INTO FRI NIGHT.
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&& .MARINE...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. MAINLY QUIET BOATING WEATHER THIS AFTERNOON AND TONIGHT. WINDS AND SEAS WILL INCREASE SOMEWHAT LATE TONIGHT INTO WEDNESDAY IN RESPONSE TO A FRONTAL SYSTEM APPROACHING THE WATERS. SMALL CRAFT ADVISORIES HAVE BEEN ISSUED FOR THE SOUTHERN OUTER WATERS AND RHODE ISLAND AND BLOCK ISLAND SOUNDS. THESE MAY NEED TO BE EXPANDED AS WE MOVE INTO THURSDAY. OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY... WED NIGHT...PREFRONTAL SW GUSTS TO 20 KT WITH SCA SEAS OVER THE SOUTHERN WATERS. THU...LIGHT SW WINDS...BUT LINGERING SOUTHERLY SWELL YIELDING SCA SEAS OVER THE SOUTHERN WATERS. FRI THROUGH SUN...HIGH PRES OVER THE WATERS LEADS TO A PERIOD OF MAINLY QUIET BOATING WEATHER WITH LIGHT WINDS AND SEAS BELOW SCA THRESHOLDS.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON WEDNESDAY TO 8 AM EDT THURSDAY FOR ANZ254>256. SMALL CRAFT ADVISORY FROM 8 PM WEDNESDAY TO 8 AM EDT THURSDAY FOR ANZ235-237.
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&& $$ SYNOPSIS...KJC/RLG NEAR TERM...RLG SHORT TERM...RLG LONG TERM...KJC AVIATION...KJC/RLG MARINE...KJC/RLG

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