Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 292313 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 713 PM EDT MON JUN 29 2015 .SYNOPSIS... WARMER TEMPERATURES MOVE IN TUESDAY AHEAD OF AN APPROACHING COLD FRONT. THIS FRONT WILL BRING SHOWERS/SCATTERED THUNDERSTORMS VERY LATE TUESDAY NIGHT AND WEDNESDAY WITH MORE SHOWERS AND STORMS POSSIBLE THURSDAY AS THE FRONT STALLS IN NEW ENGLAND. THE FRONT PUSHES SOUTH OF THE COAST FRIDAY WITH WEAK HIGH PRESSURE BRINGING MAINLY DRY AND SEASONABLE WEATHER THROUGH THE WEEKEND. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 710 PM UPDATE... STILL A FEW SHOWERS MOVING THROUGH W AND CENTRAL MA WHICH WILL DISSIPATE BY 8-9 PM. OTHERWISE...STRATO-CU ARE BEGINNING TO ERODE AND THIS WILL CONTINUE AS MODEL CROSS SECTIONS SHOW DRYING IN THE 3 TO 6 THOUSAND FOOT LAYER OF THE ATMOSPHERE. MOSTLY CLEAR TO PARTLY CLOUDY SKIES ARE EXPECTED TONIGHT. LOW TEMPS WILL DROP INTO THE 50S IN MOST LOCATIONS WITH SOME LOWER 60S POSSIBLE IN A FEW LOCATIONS. PATCHY GROUND FOG MAY DEVELOP LATE IN THE TYPICALLY PRONE LOCATIONS...BUT NOT EXPECTING ANYTHING WIDESPREAD. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... TUESDAY... A PARTLY SUNNY AND PLEASANT DAY IN STORE FOR THE REGION. HIGH TEMPS MAINLY IN THE LOWER 80S...BUT COOLER MIDDLE TO UPPER 70S ARE EXPECTED ON PORTIONS OF THE COAST WITH SEA BREEZES. UPPER TROUGH/SHORTWAVE WILL RESULT IN SHOWERS AND THUNDERSTORMS DEVELOPING ACROSS PORTIONS OF NEW YORK STATE AND PENNSYLVANIA DURING THE AFTERNOON. ACROSS OUR REGION...UPPER LEVEL RIDGING WILL GENERALLY RESULT IN DRY WEATHER. MAY SEE JUST ENOUGH INSTABILITY FOR AN ISOLATED BRIEF SHOWER/THUNDERSTORM OR TWO IN FAR NORTHERN ZONES AND ESPECIALLY NORTHWEST MA LATE TUE AFTERNOON/EARLY EVENING. TUESDAY NIGHT... OTHER THAN AN EVENING ISOLATED SPOT SHOWER/THUNDERSTORM IN NORTHERN OR NORTHWEST MA...DRY WEATHER WILL DOMINATE THROUGH MIDNIGHT. HOWEVER...POTENT SHORTWAVE AND ASSOCIATED COLD POOL ALOFT WILL APPROACH FROM THE WEST TOWARD DAYBREAK. TIMING UNCERTAIN...BUT SOME OF THE MODELS SHOW SHOWERS AND THUNDERSTORMS WORKING INTO PARTS OF THE REGION BETWEEN 9Z AND 12Z. TIMING IS UNCERTAIN AND THE BULK OF THE ACTION MAY HOLD OFF UNTIL AFTER 12Z. IF ACTIVITY DOES ARRIVE EARLY...MAY SEE QUITE A BIT OF ELEVATED CONVECTION IN OUR WESTERN ZONES GIVEN 500 MB TEMPS AROUND -12C AND MID LEVEL LAPSE RATES AROUND 6.5C/KM. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... HIGHLIGHTS... * SHOWERS AND THUNDERSTORMS LIKELY WEDNESDAY...SOME STORMS MAY BE STRONG WITH LOCALLY HEAVY RAINFALL * CONTINUED THREAT OF SHOWERS AND THUNDERSTORMS THU * LOOKING MAINLY DRY AND SEASONABLE FRI THROUGH THE 4TH OF JULY WEEKEND BUT CONFIDENCE IS NOT HIGH OVERVIEW... HIGH AMPLITUDE TROF FOR THIS TIME OF YEAR ACROSS THE GT LAKES WITH SERIES OF SHORTWAVES ROTATING INTO NEW ENG WILL BRING A PERIOD OF WET WEATHER WED AND THU. MODELS HAVE BEEN STRUGGLING WITH THE LOCATION OF A FRONTAL WAVE TOWARD THE END OF THE WEEK. PREVIOUS RUNS OF THE GFS AND ECMWF WERE QUITE WET HERE THU NIGHT INTO FRI BUT 12Z RUNS ARE NOW SUPPRESSED AND KEEP IT DRY HERE RIGHT THROUGH THE WEEKEND WITH WEAK HIGH PRESSURE OVER NEW ENG. HOWEVER...GIVEN PROXIMITY OF A SERIES OF WAVES JUST TO THE SOUTH...CONFIDENCE IN A DRY FORECAST IS NOT HIGH AS A SLIGHT NORTHWARD SHIFT WOULD MEAN A COOL RAIN. WEDNESDAY... INTERESTING SET UP AS SHOWERS AND SCT TSTMS WILL LIKELY BE MOVING INTO SNE FIRST THING IN THE MORNING AS MID LEVEL SHORTWAVE APPROACHES FROM THE WEST AND WARM FRONT MOVES UP FROM THE SW. ALL MODELS ARE GENERATING DECENT SFC INSTABILITY GREATER THAN 1000 J/KG BY 18Z DUE TO FAVORABLE MID LEVEL LAPSE RATES. THIS COMBINED WITH GOOD LARGE SCALE SYNOPTIC FORCING AND DEEP LAYER MOISTURE SUGGESTS NUMEROUS SHOWERS AND SCT TSTMS MOVING WEST TO EAST ACROSS SNE DURING THE MORNING AND INTO THE AFTERNOON. GOOD 500 MB JET PUNCHING INTO THE REGION RESULTS IN 0-6KM SHEAR OF 40-45 KT WHICH IS RATHER IMPRESSIVE. IF INSTABILITY CAN BE REALIZED WE CANT RULE OUT A FEW STRONG TO SEVERE STORMS WED MORNING INTO EARLY AFTERNOON BUT IT COULD ALSO JUST BE A BATCH OF SHOWERS AND WEAKER STORMS OF INSTABILITY IS WEAKER AS WARM FRONT NOT LIKELY TO LIFT TO THE NORTH UNTIL THE AFTERNOON. IT IS POSSIBLE HOWEVER THAT THE COOL AIR ALOFT ASSOCD WITH THE MID LEVEL SHORTWAVE AND RESULTING STEEP LAPSE RATES HELPS TO MAINTAIN DECENT SFC INSTABILITY. THIS IS SOMETHING THAT WILL NEED TO BE MONITORED BUT LOCALLY HEAVY RAINFALL WILL ALSO BE A THREAT. THE MAIN QUESTION FOR LATER IN THE AFTERNOON IS IF A SECOND ROUND OF SHOWERS/TSTMS CAN DEVELOP IN THE INTERIOR AHEAD OF A COLD FRONT. MODELS ARE DRYING THE COLUMN LATE IN THE DAY SO THERE IS LIMITED WINDOW FOR A SECOND ROUND OF CONVECTION. ALSO DEEP LAYER SHEAR IS WEAKENING AFT 18Z. TEMPS MOSTLY IN THE 70S BUT IT WILL BECOME HUMID WITH DEWPOINTS CLIMBING WELL INTO THE 60S. THURSDAY... COLD FRONT LIKELY GETS HUNG UP ACROSS SNE AS ANOTHER MID LEVEL SHORTWAVE APPROACHES FROM THE GT LAKES. MODELS SHOW DESTABILIZATION OCCURRING WITH UP TO 1000 J/KG OF SBCAPE AND A SURGE OF HIGHER KI VALUES MOVING BACK INTO THE REGION SO MORE SHOWERS AND TSTMS ARE POSSIBLE ESPECIALLY IN THE AFTERNOON WITH FOCUS MORE IN CENTRAL AND E NEW ENG. 0-6 KM SHEAR IS 35-40 KT SO IF INSTABILITY IS REALIZED CANT RULE OUT A FEW STRONG STORMS BUT MID LAPSE RATES WILL BE A LIMITING FACTOR. FRIDAY THROUGH MONDAY... NOT A HIGH CONFIDENCE FORECAST BUT LATEST GUIDANCE IS SUGGESTING MOSTLY DRY AND SEASONABLE CONDITIONS WITH A WARMING TREND BY SUNDAY AS A SERIES OF WAVES REMAIN TO THE SOUTH THROUGH SAT WITH WEAK HIGH PRES IN CONTROL. HOWEVER...ANY SLIGHT NORTHWARD ADJUSTMENT WOULD RESULT IN COOLER AND WET WEATHER FRI AND SAT. && .AVIATION /23Z MONDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... 20Z UPDATE... TONIGHT...HIGH CONFIDENCE. VFR CONDITIONS THEN CONTINUE FOR THE REST OF THE NIGHT...OTHER THAN PERHAPS A FEW HOURS OF PATCHY GROUND FOG LATE IN THE TYPICALLY PRONE LOCATIONS. TUESDAY...HIGH CONFIDENCE IN MAINLY VFR CONDITIONS. AN ISOLATED SPOT SHOWER/THUNDERSTORM OR TWO IS POSSIBLE IN THE AFTERNOON ACROSS PORTIONS OF OUR NORTHERN ZONES...WITH THE BEST SHOT IN FAR NORTHWEST MA. TUESDAY NIGHT...LOW CONFIDENCE. VFR IN THE EVENING. MAY SEE SOME LOW CLOUDS DEVELOP LATE IN SOME LOCATIONS WITH THE BEST SHOT FOR THIS ALONG THE SOUTHEAST NEW ENGLAND COAST. MAY ALSO SEE AN AREA OF SHOWERS AND THUNDERSTORMS WORK INTO WESTERN NEW ENGLAND TOWARD DAYBREAK...BUT CONFIDENCE ON THAT IS ALSO LOW. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...WEDNESDAY THROUGH SATURDAY... WED...HIGH PROBABILITY FOR WIDESPREAD SHOWERS WITH SCATTERED TSTMS. RISK OF A FEW STRONG STORMS AND HEAVY RAINFALL. IFR AND MVFR CONDITIONS LIKELY. THU...MODERATE CONFIDENCE. MOSTLY VFR...BUT SCT SHOWERS/TSTMS POSSIBLE IN THE AFTERNOON WITH MVFR CONDITIONS. FRI AND SAT...LOW CONFIDENCE. VFR WITH MOSTLY DRY CONDITIONS...BUT IT COULD STILL END UP WET IF WAVES OF LOW PRES TRACK FURTHER N. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TONIGHT INTO TUESDAY NIGHT/...HIGH CONFIDENCE. TONIGHT...SOUTHWEST WIND GUSTS NEAR 25 KNOTS ACROSS OUR SOUTHERN WATERS DIMINISH EARLY THIS EVENING. HOWEVER...LEFT OVER SWELL OF 3 TO 6 FEET WILL CONTINUE WELL INTO THE OVERNIGHT HOURS ACROSS OUR SOUTHERN WATERS. SMALL CRAFT HEADLINES HAVE BEEN TIMED ACCORDINGLY. TUESDAY AND TUESDAY NIGHT...WEAK PRESSURE GRADIENT WILL KEEP WINDS/SEAS BELOW SMALL CRAFT ADVISORY THRESHOLDS. SOME FOG MAY DEVELOP TOWARD DAYBREAK WEDNESDAY ACROSS OUR SOUTHERN WATERS. OUTLOOK...WEDNESDAY THROUGH SATURDAY... WED...HIGH CONFIDENCE. SW WIND GUSTS TO 20 KT WITH SCA SEAS OVER SOUTHERN WATERS. VSBYS LIMITED IN SHOWERS AND SCATTERED TSTMS AND AREAS OF FOG. THU...HIGH CONFIDENCE. LIGHT SW WINDS BUT LEFTOVER SOUTHERLY SWELL WILL RESULT IN SCA SEAS OVER SOUTHERN WATERS. SCT SHOWERS/TSTMS POSSIBLE IN THE AFTERNOON. FRI AND SAT...MODERATE CONFIDENCE. LIGHT EASTERLY WINDS. MARGINAL SCA SEAS POSSIBLE SOUTHERN WATERS ON FRI. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ232>234. SMALL CRAFT ADVISORY UNTIL 5 AM EDT TUESDAY FOR ANZ235-237- 254>256. && $$ SYNOPSIS...KJC/FRANK NEAR TERM...KJC/FRANK SHORT TERM...FRANK LONG TERM...KJC AVIATION...KJC/FRANK MARINE...KJC/FRANK

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