Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 211134 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 734 AM EDT THU AUG 21 2014 .SYNOPSIS... A FEW SHOWERS ARE EXPECTED ACROSS MAINLY THE WESTERN HALF OF NEW ENGLAND THROUGH EARLY FRIDAY. DRIER AND COOLER WEATHER FOLLOWS THIS WEEKEND. A WARM-UP IS POSSIBLE NEXT WEEK PRIOR TO AN UNSETTLED PATTERN AHEAD OF A FRONTAL BOUNDARY SWEEPING SOUTH OUT OF CANADA. && .NEAR TERM /THROUGH TONIGHT/... 730 AM UPDATE... ONLY MINOR TWEAKS NEEDED TO THE ONGOING FORECAST THIS MORNING. PATCHY LATE NIGHT FOG ALREADY DISSIPATING. ONSHORE FLOW WILL DEVELOP QUICKLY ONCE MORE THIS MORNING. PREVIOUS DISCUSSION... A TALE OF TWO LOW PRES SYSTEMS WILL DEFINE THE WEATHER THROUGH THE DAY TODAY. ONE...AN UPPER LVL DISTURBANCE IS CURRENTLY WEAKENING AND IS ASSOCIATED WITH A WARM FRONT EXPECTED TO REMAIN STALLED TO THE W. THE OTHER IS A SLOWLY DEEPENING WEAK WAVE OF LOW PRES EXPECTED TO SLOWLY MOVE E OF THE 40/70 BENCHMARK INTO THE WEEKEND. THIS LATTER FEATURE REMAINS WEAK...AND EXCEPT FOR AN INVERTED TROF EVIDENT IN THE FLOW PATTERN HANGING BACK TOWARD THE ISLANDS...IS EXPECTED TO HAVE LITTLE EFFECT ON THE REGION. ONLY EXPECT A FEW SHOWERS FOR MAINLY ACK THROUGH ABOUT THE AFTERNOON TIMEFRAME. THE FORMER...THE UPPER LVL DISTURBANCE CONTINUES TO WEAKEN TOO AS IT INTERACTS WITH A BLOCKED FLOW PATTERN AND CUTOFF HIGH PRES TO THE N. IN FACT...IT WILL CONTINUE TO TRANSITION FROM A WEAK CUTOFF TO AN OPEN WAVE THROUGH THE DAY. FLOW THROUGH THE COLUMN ABOVE SRN NEW ENGLAND REMAINS WEAK...WITH BOTH UPPER AND LOW LVL JET/S REMAINING WELL TO THE W THROUGH THE DAY. THE APPROACHING WARM FRONT AND MODEST LIFT PROVIDED BY WEAK DIFFERENTIAL VORT ADVECTION FROM THE WAVE WILL PROVIDE SOME FOCUS FOR SHOWERY ACTIVITY TO WORK ON A MOISTENING COLUMN MAINLY ACROSS CT AND WRN MA/NH. THE INVERTED RIDGE ALREADY IN PLACE ACROSS THE REGION HAS ALSO LED TO E FLOW WHICH WILL SUPPRESS ANY ATTEMPT AT DESTABILIZATION ACROSS THE AREA. THEREFORE...WITH THE BULK OF THE ENERGY AND POTENTIAL INSTABILITY REMAINING TO THE W...WILL KEEP POPS FOCUSED MAINLY ACROSS THE EXTREME W PORTIONS OF THE AREA AS WELL AT LEAST THROUGH MUCH OF THE DAYLIGHT HOURS. REGARDING TEMPS...WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED THROUGH THE DAY BETWEEN THESE TWO SYSTEMS...HIGHS ARE LIKELY TO REMAIN BELOW NORMAL AND IN THE LOW-MID 70S. && .SHORT TERM /FRIDAY/... TONIGHT... SLIGHTLY INCREASED THREAT FOR OVERNIGHT SHOWERS...BUT STILL MAINLY ACROSS THE W THANKS TO SOME LEFTOVER SUBSIDENCE CLOSER TO THE GRADUALLY REBOUNDING INVERTED RIDGE. THE REMNANT VORT MAX FROM AN UPPER LVL DISTURBANCE WILL BE MOVING ACROSS THE AREA THROUGH THE OVERNIGHT HOURS. JET ENERGY THROUGHOUT THE COLUMN IS WEAK AND WHAT IS LEFT OF A SFC WARM FRONT WILL LIKELY HAVE WASHED OUT FOR MOST PART. THEREFORE...IT IS ONLY THE VORT MAX WHICH WILL BE PROVIDING LIFT TO WORK ON THE 1.5 OR LESS PWAT AIRMASS IN PLACE ACROSS THE REGION. DRIER AIR STILL REMAINS MAINLY ACROSS THE E...SO WILL ONCE AGAIN FOCUS MAINLY FROM THE WORCESTER HILLS AND POINTS W FOR THE SHOWERS. NO THUNDER WITH THIS UPDATE...AS THE AIRMASS REMAINS QUITE STABLE THROUGHOUT. GUIDANCE HAS BACKED OFF ON THE QPF BULLSEYES THAT IT WAS SHOWING IN PREVIOUS RUNS FOR THE MOST PART...BUT THESE ARE LIKELY JUST A CONVECTIVE FEEDBACK ISSUE. OTHERWISE...MILD OVERNIGHT MINS WITH A FAIR AMOUNT OF CLOUD COVER. MAY NEED TO ALSO MONITOR ESPECIALLY THE E AND SE COASTLINES FOR FOG AND STRATUS THANKS TO CONTINUED E FLOW AND SLIGHTLY HIGHER DWPTS WITHIN THE MOISTENED COLUMN IN COMPARISON TO PREVIOUS DAYS. FRI... UPPER LVL VORT MAX SLIDES TO THE SE DURING THE MORNING...COMBINING WITH LEFTOVER CUTOFF ENERGY ACROSS ATLANTIC CANADA. WHILE THIS WILL FORM A HANGING TROF WITH AXIS FROM THE MID ATLANTIC THROUGH THE 40/70 BENCHMARK...MID LVL RIDGING WILL THEN BE ABLE TO REGAIN CONTROL INTO WRN NEW ENGLAND. THIS WILL ALSO ALLOW THE INVERTED RIDGE TO BUILD BACK IN ACROSS THE REGION. THIS SHOULD ALLOW SHOWERS ACROSS THE AREA TO GRADUALLY DISSIPATE THROUGH THE DAY AS THE COLUMN DRIES FROM INCREASING SUBSIDENCE. HAVE POPS DIMINISHING THROUGH THE DAY ACROSS THE AREA. IT WILL LIKELY TAKE A BIT MORE TIME FOR THE CLOUDS TO DISSIPATE GIVEN MOISTURE IS LIKELY TO BE TRAPPED BENEATH THE SUBSIDENCE INVERSION AND E FLOW CONTINUES. IN FACT...LOOKS LIKE AN UPPER LVL BACKDOOR COLD FRONT WILL LEAD TO DECREASING H85 TEMPS. HAVE HELD HIGHS BACK...MAINLY IN THE 60S TO AROUND 70. E COASTAL REGIONS ARE LIKELY TO TAKE THE LONGEST TO SEE ANY CLEARING. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... HIGHLIGHTS... * QUIET WEATHER EXPECTED THROUGH MUCH OF THIS PERIOD * UNCERTAINTY INCREASES MIDDLE OF NEXT WEEK WITH AN APPROACHING FRONT 21/00Z MODELS ARE IN GOOD AGREEMENT THROUGH ABOUT TUESDAY. THEN SIGNIFICANT DIFFERENCES ARISE FOR THE LATTER HALF OF NEXT WEEK... MAKING FOR A LOWER CONFIDENCE FORECAST FROM THE MIDDLE OF NEXT WEEK ONWARD. A PERSISTENT UPPER LEVEL TROUGH OVER THE NORTHEAST WILL SLOWLY MAKE ITS WAY EAST...MOVING JUST OFFSHORE THIS WEEKEND AS AN UPPER LEVEL RIDGE TRIES TO PUSH NORTHEASTWARD FROM THE SOUTHERN USA. THIS UPPER TROUGH IS RATHER PERSISTENT THOUGH...WITH EACH SUCCESSIVE MODEL RUN LINGERING THIS TROUGH OVER THE NORTH ATLANTIC LONGER AND LONGER. COOLER...LESS SEASONABLE WEATHER IS EXPECTED WHILE HIGH PRESSURE IN QUEBEC WILL KEEP THINGS RELATIVELY DRY. STILL AGREE WITH THE PREVIOUS FORECASTER...THINKING 21/00Z GUIDANCE CONTINUES TO STRUGGLE WITH CONVECTIVE FEEDBACK INTO EARLY NEXT WEEK. AS SUCH...KEPT A DRY FORECAST ACROSS MOST OF SOUTHERN NEW ENGLAND. A HIGH PRESSURE WILL SINK SOUTH INTO EARLY NEXT WEEK...EVENTUALLY MOVING SOUTH AND EAST OF SOUTHERN NEW ENGLAND AND RETURNING US TO A MORE WESTERLY FLOW. A LOW PRESSURE IN ONTARIO MAY EVENTUALLY MOVE EAST INTO QUEBEC...SWINGING A COLD FRONT THROUGH SOUTHERN NEW ENGLAND WEDNESDAY OR THURSDAY. THIS IS WHERE MODELS START TO DIVERGE MORE SIGNIFICANTLY. THE ECMWF LOOKS A BIT QUICKER THAN THE GFS WITH THE APPROACH OF THIS FRONT...BUT NEITHER IS AS PROGRESSIVE AS THE CANADIAN. WILL TAKE A BLENDED APPROACH WITH THE TIMING FOR NOW. GIVEN THE STRENGTH OF THE SURFACE RIDGE EXPECTED TO BE NEAR THE COAST...WOULD NOT BE OVERLY SURPRISED IF THE ULTIMATE TIMING TURNS OUT TO BE SLOWER THAN THE GFS. DEPENDING ON AVAILABLE MOISTURE...WE COULD SEE SOME SHOWERS AND THUNDERSTORMS AHEAD OF THIS FRONT. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...THROUGH FRIDAY...MODERATE CONFIDENCE. TODAY AND TONIGHT... MAINLY VFR. EXCEPT POSSIBLY FOR KACK...MOST OF THE RAIN REMAINS TO THE W THROUGH THE DAY. THEN...BETTER CHANCE FOR SHOWERS ACROSS WRN MA/CT/NH OVERNIGHT ESPECIALLY...WITH OCCASIONAL MVFR CONDITIONS POSSIBLE. SOME LOW MVFR/IFR POSSIBLE MAINLY ACROSS THE E COAST. FRI... CONDITIONS IMPROVE THROUGH THE DAY. SOME MVFR/IFR POSSIBLE IN THE MORNING GIVES WAY TO VFR THROUGH THE DAY...BUT MAY TAKE MOST OF THE DAY ALONG THE E COAST. KBOS TERMINAL...MODERATE CONFIDENCE. MAIN CONCERN IS WHETHER A BRIEF PERIOD OF IFR CONDITIONS MOVE IN EARLY THIS MORNING BRIEFLY...AND THEN RETURNS LATE THU NIGHT. OTHERWISE VFR WITH E FLOW ASSISTED BY SEABREEZES EXPECTED. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. -RA CHANCES BEGIN TOWARDS THURSDAY MORNING ALONG WITH LOW-END VFR CIGS. MVFR CIGS POSSIBLE THOUGH MAINLY TONIGHT...BUT REMAINS LOW-CONFIDENCE AT THIS TIME. OUTLOOK...FRIDAY THROUGH MONDAY... HIGH CONFIDENCE VFR. LOW PROBABILITY OF PATCHY MVFR/IFR FOG EACH NIGHT. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM...THROUGH FRIDAY...MODERATE CONFIDENCE. LOW PRES WILL GRADUALLY STRENGTHEN OFFSHORE THROUGH THE DAY...BUT THEN MOVE E INTO FRI. A FEW SHOWERS ARE LIKELY TO IMPACT MAINLY THE WATERS S OF THE VINEYARD AND ACK INTO MID DAY UNTIL THE LOW MOVES FURTHER E. THE WEAK LOW PRES WILL ALSO GENERATE A MODEST SWELL...BUT IT SHOULD GENERALLY REMAIN BELOW 4 FT INTO THE DAY ON FRI. WINDS TOO MAY GUST TO ABOUT 15-20 KT AT TIMES OUT OF THE E...BUT SHOULD REMAIN BELOW SMALL CRAFT ADVISORY LEVELS THROUGH THE PERIOD. OUTLOOK...FRIDAY NIGHT THROUGH MONDAY... HIGH CONFIDENCE. QUIET BOATING WEATHER IS EXPECTED FOR MUCH OF THIS PERIOD WITH HIGH PRESSURE ACROSS THE REGION. SEAS COULD APPROACH 5 FT ACROSS THE OUTERMOST SOUTHERN COASTAL WATERS THIS WEEKEND. NOT ENOUGH CONFIDENCE TO ISSUE A SMALL CRAFT ADVISORY THOUGH. LOW PROBABILITY OF PATCHY OVERNIGHT FOG LIMITING VISIBILITIES. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...BELK/DOODY NEAR TERM...BELK/DOODY SHORT TERM...DOODY LONG TERM...BELK AVIATION...BELK/DOODY MARINE...BELK/DOODY

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