Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 242314 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 714 PM EDT THU JUL 24 2014 .SYNOPSIS... HIGH PRESSURE WILL BRING DRY AND BEAUTIFUL WEATHER INTO THE FIRST PART OF THE WEEKEND. SHOWERS AND THUNDERSTORMS POSSIBLE LATE THIS WEEKEND INTO EARLY NEXT WEEK WITH AN APPROACHING FRONTAL SYSTEM. THE COLD FRONT MOVES OFFSHORE TUESDAY WITH HIGH PRESSURE BUILDING IN BEHIND. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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715 PM UPDATE...A FEW VERY ISOLATED SHOWERS STILL GOING OVER SOUTHERN RHODE ISLAND AT THIS TIME. BUT EXPECT THESE TO DIMINISH AS THE SUN SETS. SHOWERS OFF THE CAPE AND ISLANDS CONTINUE TO MOVE OFFSHORE. MADE SOME MINOR UPDATES TO THE FORECAST TO ACCOUNT FOR THE LATEST TRENDS IN TEMPERATURES...SKY COVER...ETC. OTHERWISE... THE FORECAST IS ON TRACK. PREVIOUS DISCUSSION FOLLOWS. AN UPPER LEVEL SHORTWAVE CROSSING THE REGION MAY ALLOW FOR A FEW SHOWERS ALONG THE SOUTHEAST NEW ENGLAND COAST THROUGH EARLY THIS EVENING...WITH THE BEST CHANCE ACROSS THE VINEYARD AND NANTUCKET. OTHERWISE...DRIER AIR WILL WORK IN FROM THE NORTHWEST ALLOWING FOR SKIES TO BECOME MAINLY CLEAR TONIGHT. THIS WILL COMBINED WITH DIMINISHING WINDS RESULTING IN A GOOD NIGHT OF RADIATIONAL COOLING. LOW TEMPS WILL MAINLY BE IN THE 50S...TO THE LOWER 60S IN THE URBAN HEAT ISLAND OF BOSTON. WE MAY EVEN SEE A FEW UPPER 40S IN THE NORMALLY COOLEST OUTLYING LOCATIONS OF NORTHWEST MA/SOUTHWEST NH. QUITE A COMFORTABLE NIGHT FOR LATE JULY STANDARDS.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... ***BEAUTIFUL WEATHER FRIDAY WITH SUNNY SKIES/WARM AFTERNOON TEMPS AND LOW HUMIDITY*** FRIDAY... AFTER A DRY RELATIVELY COOL START...PLENTY OF JULY SUNSHINE SHOULD ALLOW MOST HIGHS SATURDAY AFTERNOON TO TOP OUT IN THE LOWER TO MIDDLE 80S IN MOST LOCALES. A WEAK PRESSURE GRADIENT WILL ALLOW FOR SEA BREEZES TO DEVELOP ON THE IMMEDIATE COAST...RESULTING IN HIGH TEMPS A FEW DEGREES COOLER IN THOSE LOCATIONS. THE BIG STORY WILL BE THE LOW HUMIDITY MAKING FOR AN EXCELLENT DAY FOR OUTDOOR ACTIVITIES. FRIDAY NIGHT... ANOTHER NICE/DRY NIGHT IN STORE FOR SOUTHERN NEW ENGLAND. MAY SEE A BIT OF HIGH CLOUDINESS MOVE INTO THE REGION LATE...BUT THAT IS ABOUT IT. LOW TEMPS SHOULD BOTTOM OUT MAINLY IN THE 50S...TO THE LOWER 60S. MAY SEE A TOUCH OF PATCHY GROUND FOG DEVELOP LATE IN THE TYPICALLY PRONE LOCATIONS...BUT NOTHING WIDESPREAD. && .LONG TERM /SATURDAY THROUGH THURSDAY/... * SHOWERS AND THUNDERSTORMS POSSIBLE OVER THE WEEKEND AND INTO EARLY NEXT WEEK * HIGH PRESSURE BUILDS IN BEHIND COLD FRONT WED AND THU ON A SYNOPTIC LEVEL...THE MODELS INCLUDING THE ECMWF ENSEMBLE AND GEFS ARE IN DECENT AGREEMENT. HOWEVER...THERE ARE OF COURSE MANY DISCREPANCIES WHEN IT COMES TO THE MESOSCALE DETAILS. THE OVERALL PATTERN HAS AN ANOMALOUSLY STRONG PERSISTENT UPPER TROUGH OVER THE GREAT LAKES WITH PERSISTENT RIDGING OVER THE WESTERN CONUS. THIS BRINGS SOME TIMING CONCERNS AS THE PERSISTENT TROUGH IS LIKELY TO SLOW THE TRAVEL OF A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION LATE SUNDAY THROUGH TUESDAY. THE MAIN CONCERN FOR THIS PERIOD OF THE FORECAST WILL BE THE SATURDAY TO MONDAY TIME FRAME WHEN SHOWERS AND THUNDERSTORMS ARE LIKELY. THERE IS A POTENTIAL FOR SEVERE THUNDERSTORMS SOMETIME DURING THIS TIME FRAME BUT THERE IS QUITE A BIT OF UNCERTAINTY WHEN IT COMES TO THE DETAILS AND TIMING OF THIS POTENTIAL. AFTER THE COLD FRONT MOVES OFFSHORE TUESDAY...EXPECT HIGH PRESSURE TO BUILD IN ACROSS SOUTHERN NEW ENGLAND. SATURDAY THROUGH MONDAY...LOW PRESSURE MOVES THROUGH SOUTHEASTERN CANADA EVENTUALLY...SLOWLY...PULLING A COLD FRONT THROUGH SOUTHERN NEW ENGLAND. CONCURRENTLY...A SERIES OF SHORTWAVES WILL ROTATE AROUND THE PERSISTENT UPPER TROUGH OVER THE GREAT LAKES. INCREASINGLY WARMER AND MORE HUMID AIR WILL MOVE INTO THE REGION ON SOUTHWESTERLY WINDS. ALL OF THIS WILL COME TOGETHER RESULTING IN A RATHER UNSTABLE ENVIRONMENT WITH MULTIPLE POTENTIAL TRIGGERS FOR SHOWERS AND THUNDERSTORMS. MUCH OF SATURDAY LOOKS TO BE DRY WITH SHOWERS AND THUNDERSTORMS LIKELY NOT DEVELOPING UNTIL SATURDAY NIGHT. THEN QUITE A BIT OF INSTABILITY ACROSS THE REGION SATURDAY NIGHT INTO SUNDAY WITH SB CAPES FORECAST TO BE OVER 1000 J/KG AND POSSIBLY OVER 2000 J/KG ON SUNDAY. IN ADDITION...EXPECTING 30 TO 40 KTS OF 0 TO 6 KM BULK SHEAR DURING THIS TIME. DEPENDING ON WHEN ALL OF THIS COMES TOGETHER AND WHICH MODEL HAS THE DETAILS RIGHT...WE COULD BE LOOKING AT SOME OF THESE THUNDERSTORMS BECOMING SEVERE. SUNDAY IS THE REAL QUESTION MARK AS WHETHER THERE ARE STORMS OR NOT WILL DEPEND ON HOW MUCH OCCURS SATURDAY NIGHT AND HOW WORKED OVER THE ATMOSPHERE BECOMES. EXPECT STORMS TO OCCUR AGAIN MONDAY AS THE COLD FRONT FINALLY STARTS TO MOVE INTO SOUTHERN NEW ENGLAND. TUESDAY THROUGH THURSDAY...THE COLD FRONT FINALLY MOVES OFFSHORE ON TUESDAY. THERE COULD BE A FEW LINGERING SHOWERS ON THE CAPE BEFORE IT PUSHES THE REST OF THE WAY OFFSHORE. HIGH PRESSURE THEN BUILDS IN OVER SOUTHERN NEW ENGLAND WEDNESDAY AND SLIDES OFFSHORE ON THURSDAY. OF COURSE...ALL OF THIS WILL BE DEPENDENT ON THE SPEED OF THE COLD FRONT. IF IT SLOWS DOWN ANYMORE...THEN SHOWERS AND STORMS COULD LINGER INTO TUESDAY FOR MORE OF THE AREA. && .AVIATION /23Z THURSDAY THROUGH TUESDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH FRIDAY NIGHT/...HIGH CONFIDENCE. TONIGHT THROUGH FRIDAY NIGHT... LINGERING IFR/MVFR CIGS ON THE CAPE/NANTUCKET SHOULD IMPROVE THIS EVENING. OTHERWISE...VFR CONDITIONS RIGHT THROUGH FRIDAY NIGHT OTHER THAN VERY LOCALIZED LATE NIGHT/EARLY MORNING FOG. KBOS TAF...HIGH CONFIDENCE. SEA BREEZE RETURNS BY FRIDAY AFTERNOON. KBDL TAF...HIGH CONFIDENCE. OUTLOOK...SATURDAY THROUGH TUESDAY... SATURDAY THROUGH MONDAY...MODERATE CONFIDENCE. MAINLY VFR. PERIODS OF MVFR/IFR LIKELY IN SHRA/TSRA. TUESDAY...MODERATE CONFIDENCE. VFR. LOW PROBABILITY OF MVFR CONDITIONS ON THE CAPE AND ISLANDS.
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&& .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...HIGH CONFIDENCE. EXCELLENT BOATING WEATHER THROUGH FRIDAY NIGHT WITH WEAK PRESSURE GRADIENT KEEPING WINDS/SEAS WELL BELOW SCA THRESHOLDS. VISIBILITIES SHOULD BE EXCELLENT MOST OF THE TIME. OUTLOOK...SATURDAY THROUGH TUESDAY... MODERATE CONFIDENCE. SOUTHWESTERLY WINDS AND SEAS INCREASE GRADUALLY AS A COLD FRONT SLOWLY APPROACHES THE WATERS. SHOWERS AND THUNDERSTORMS ARE POSSIBLE SATURDAY NIGHT THROUGH TUESDAY OVER THE WATERS. SMALL CRAFT ADVISORIES WILL BE NECESSARY SATURDAY NIGHT THROUGH TUESDAY FOR SEAS AND SUNDAY FOR WINDS GUSTING TO AROUND 25 KTS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...FRANK/RLG NEAR TERM...FRANK/RLG SHORT TERM...FRANK LONG TERM...RLG AVIATION...FRANK/RLG MARINE...FRANK/RLG

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