Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 211800 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 200 PM EDT THU AUG 21 2014 .SYNOPSIS... SHOWERS ACROSS 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/...
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2 PM UPDATE... NOT AN EASY MORNING FORECAST AND ONE IN WHICH THE MODELS DID NOT HAVE A GOOD HANDLE ON...AND NEITHER DID I. BAND OF RAIN PRESENTLY SWEEPING ACROSS THE REGION APPEARS FOCUSED ALONG A LEADING EDGE OF LOW-LEVEL CONVERGENCE AND F-GEN FORCING AHEAD OF A MID-LEVEL IMPULSE AND SUBSEQUENT ASCENT PINWHEELING ROUND THE BROADER LOW OVER THE E GREAT LAKES. ANYTHING GOES WITH MODEST LIFT OF MOISTURE ADVECTED THROUGH A DECENT LOW-LEVEL THETA-E PLUME AHEAD OF THE LOW. WILL CONTINUE WITH LIKELY POPS TOWARDS THE NE DIMINISHING AGAINST THE RIDGE AND DRIER AIR ASSOCIATED WITH THE CUTOFF HIGH. ACTIVITY BEGINNING TO DEVELOP ACROSS PA/NY. AS THE WEAKENING LOW SHIFTS SE AS AN OPEN WAVE...WILL FOCUS GREATER CHANCES FOR PRECIP TOWARDS THE S/W AS ACTIVITY SHIFTS TOWARDS BETTER THERMAL AND INSTABILITY AXES. IT IS HERE THE COMBINATION OF ADDITIONAL MID-LEVEL IMPULSES AND THE MOIST TONGUE OF CONVERGENT THETA-E AIR SHOULD COLLOCATE TO YIELD SHOWER ACTIVITY...EVEN THOUGH THE BETTER ACTIVITY WILL BE SW ACROSS THE NYC TRI-STATE REGION AND CLOSER TO THE SURFACE WARM- FRONT. STILL HOLDING WITH HIGHS AROUND THE LOW- TO MID-70S. THE WARMEST OF CONDITIONS TOWARDS THE S/E WITH THE GREATER ABUNDANCE OF
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&& .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. FRIDAY... 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 /18Z 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...MODERATE CONFIDENCE. VFR INTO THIS EVENING. BUT AS E-ONSHORE FLOW INCREASES AND SHOWERS BUILD OVER THE S/W NEW ENGLAND TERMINALS...GREATER PROPENSITY FOR A MIX OF MVFR-IFR CONDITIONS DURING THE EVENING HOURS. UNSURE AS TO OUTCOMES E/SE. ITS POSSIBLE THE REGION REMAINS VFR ALBEIT SOME PATCHY DENSE FOG AND LOW CLOUDS ACROSS THE INTERIOR WITH EVENING COOLING. INTO THE FRIDAY INTO FRIDAY NIGHT PERIOD...ANTICIPATING LOW-END VFR CLOUDS MIXED IN WITH MVFR AND SHOWERS TO THE S/W. E-WINDS CONTINUING WITH A LONG FETCH OFF THE WATERS. TRANSITIONING INTO EVENING...WHILE SHOWERS CONCLUDE...A MAJORITY OF THE TERMINALS MAY BECOME SOCKED IN WITH LOW-CLOUDS AND DENSE FOG. LIKELY TO SEE -DZ WITH FOG. KBOS TERMINAL...MODERATE CONFIDENCE. WILL HOLD LOW-END VFR FOR A MAJORITY OF THE FORECAST. COULD SEE CONDITIONS GRADUALLY LOWER FRIDAY INTO FRIDAY NIGHT. E-FLOW PERSISTING THROUGHOUT AND INCREASING TOWARDS THE END OF THE PERIOD...THUS LENDING TO CONFIDENCE MORE SO OF MVFR-IFR LOW-CLOUDS OVER DENSE FOG. KBDL TERMINAL...MODERATE CONFIDENCE. CONDITIONS ANTICIPATED TO LOWER INTO EVENING WITH INCREASING -SHRA CHANCES. MAY REMAIN SOCKED IN AROUND MVFR THROUGH A MAJORITY OF THE FORECAST PERIOD ALL THE WAY INTO SATURDAY MORNING. OUTLOOK...FRIDAY THROUGH MONDAY... HIGH CONFIDENCE VFR. LOW PROBABILITY OF PATCHY MVFR/IFR FOG EACH NIGHT.
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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...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...SIPPRELL SHORT TERM...DOODY LONG TERM...BELK AVIATION...BELK/DOODY MARINE...BELK/DOODY

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