Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 282259 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 659 PM EDT TUE OCT 28 2014 .SYNOPSIS... A COLD FRONT WILL APPROACH FROM THE WEST TONIGHT BRINGING SCATTERED SHOWERS AND A POSSIBLE THUNDERSTORM ON WEDNESDAY. WEAK HIGH PRESSURE NORTH OF THE REGION WILL BRING DRY COOL WEATHER THURSDAY AND FRIDAY. A DEVELOPING COASTAL STORM OFF THE CAROLINAS WILL PASS OFFSHORE SATURDAY NIGHT. HIGH PRESSURE BUILDS OVER THE EASTERN USA EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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7 PM UPDATE... NO MAJOR CHANGES TO THE FORECAST. NUMEROUS PATCHES OF ALTOCU MOVING ACROSS SOUTHERN NEW ENGLAND. THERE IS A BACK EDGE TO THIS PATCH OF CLOUDS...OVER SOUTHEAST NEW YORK. MORE CLOUDS IN WESTERN NEW YORK THAT SHOULD REACH OUR AREA AFTER MIDNIGHT. SHOWERS IN WESTERN NEW YORK ARE MOVING NORTHEAST. MUCH OF THAT AREA OF SHOWERS SHOULD PASS TO OUR NORTH. SHOWERS MORE DIRECTLY UPSTREAM ARE IN SOUTHERN OHIO ENTERING SOUTHWEST PA. THESE SHOULD TAKE UNTIL MORNING TO REACH US. PREVIOUS DISCUSSION... UPPER LEVEL RIDGE AXIS WILL MOVE OFFSHORE AS A COLD FRONT APPROACHES THE REGION FROM THE WEST. THE PRESSURE GRADIENT WILL TIGHTEN AND ALLOW GUSTS TO STAY UP OVERNIGHT. CROSS SECTIONS ACROSS THE REGION SHOW AN INCREASE IN LOW LEVEL MOISTURE SO BELIEVE LOW STRATUS MAY DEVELOP ACROSS THE REGION...ESP SOUTH AND EAST OF 1-95. THERE IS A LOW POTENTIAL FOR FOG TO DEVELOP...ESP NORTH AND EAST IN ESSEX AND SOUTHERN NH WHICH HAS REMAINED AS THE COOL SPOT ALL DAY. THIS LOCATION MAY HAVE TO BE WATCHED CLOSELY. OVERNIGHT LOW TEMPS WILL DROP INTO THE LOW TO UPPER 50S FOR MUCH OF THE AREA. IN FACT THE FORECAST MAY BE TO OPTIMISTIC ON HOW COOL IT MAY GET AND SOME LOCATIONS MAY STAY ABOVE 60F. THIS IS DUE IN PART WITH WEAK WAA THAT WILL OCCUR OVERNIGHT AS 925 MB TEMPS STAY AROUND +18 TO +20C. COLD FRONT WILL BE APPROACHING FROM THE WEST DURING THE OVERNIGHT HOURS. RIGHT NOW EXPECT MOST OF THE REGION TO STAY DRY UNTIL WED MORNING...YET CANNOT RULE OUT A SPOT SHOWER OUT WEST AHEAD OF THE FRONT NEAR DAYBREAK.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... TOMORROW... COLD FRONT WILL SWEEP ACROSS THE REGION TOMORROW. SHOULD ENTER WESTERN REGIONS ABOUT 12Z AND MOVE OFFSHORE BY 03-06Z. THIS IS A SLOW MOVING SYSTEM BUT THERE IS A LACK OF DEEP LAYER MOISTURE SO THE POTENTIAL FOR FLOODING IS LOW. BELIEVE THAT THE SHOWERS WILL BE MORE SCATTERED IN NATURE AS IT PASSES THROUGH TOMORROW. HOWEVER GUIDANCE DOES HINT AT STEEP LAPSE RATES AND LI VALUES BELOW -2...ACROSS THE SOUTHEAST COASTAL PLAIN. THIS COMBINED WITH A 30-40 KT JUST OVERHEAD...CANNOT RULE OUT THE POTENTIAL FOR AN ISOLATED THUNDERSTORM AT THIS TIME. IF A THUNDERSTORM OR STRONG SHOWER DOES DEVELOP...THERE IS A POTENTIAL THAT IT CAN PULL DOWN SOME OF THE STRONGER AIR ALOFT. TEMPERATURES TOMORROW WILL BE SIMILAR TO TODAY...HOWEVER LOCATIONS OUT WEST MAY BE COOLER AS COLD FRONT PASSES THEM. EASTERN MASS AND RHODE ISLAND MAY SNEAK UP TO 70F BUT NOT MUCH HIGHER AS CLOUDS DURING THE DAY WILL LIMIT DIURNAL HEATING POTENTIAL. TOMORROW NIGHT... UPPER LEVEL TROUGH WILL STILL BE MOVING OVERHEAD. THE COLD FRONT WILL EVENTUALLY PUSH OFFSHORE AROUND 06Z. THERE IS THE POTENTIAL THAT IT MAY LINGER A TAD LONGER SO HAVE KEPT A SLIGHT CHANCE OF PRECIP FOR THE CAPE AND ISLANDS. COLD AIR WILL BE USHERING IN BEHIND THE FRONT DUE TO CAA. SO ANTICIPATE A COOLER NIGHT WITH LOWS DROPPING INTO THE LOW TO MID 40S. && .LONG TERM /THURSDAY THROUGH TUESDAY/... BIG PICTURE... UPPER TROUGH DIGS OVER THE EASTERN USA WHILE UPPER RIDGE MIGRATES FROM THE PACIFIC COAST TO THE PLAINS. THE TROUGH LINGERS OVER NEW ENGLAND THROUGH THE WEEKEND WITH BELOW NORMAL HEIGHTS IN PLACE. THE TROUGH THEN MOVES OFF THROUGH THE MARITIMES EARLY NEXT WEEK AS THE OVERALL FLOW BECOMES MORE ZONAL. THE ECMWF SEEMS A LITTLE MORE PROGRESSIVE THAN LAST RUN...BUT NO GUARANTEE THIS TREND WILL PERSIST. THE GFS AND ECMWF BRIEFLY FORM A CLOSED LOW OVER THE MIDWEST...THEN OPEN IT ALONG THE COAST. THE ECMWF BRINGS THE SURFACE LOW TO JUST OUTSIDE THE BENCHMARK WHILE THE GFS HOLDS IT FARTHER OFFSHORE. THE ECMWF IS A WETTER SOLUTION...THE GFS IS A COLDER SOLUTION. BOTH MODELS SHOW SIMILAR PROGRESS ON THE SHORTWAVE AXIS MOVING THROUGH THE OVERALL TROUGH. WE FAVORED AN EXPANDED BLEND OF GRID DATA...BLENDING THE 12Z ECMWF WITH OUR MODEL BLENDED FIELDS. EXPECT COOLER THAN NORMAL TEMPS FOR LATE WEEK AND THE WEEKEND...THEN A WARMING TREND FOR EARLY NEXT WEEK. THE DAILIES... THURSDAY-FRIDAY... COOLING ALOFT WITH WEAK RIDGING NEAR THE SURFACE. THIS SHOULD KEEP THE WEATHER DRY THURSDAY AND AT LEAST THE FIRST PART OF FRIDAY. AS THE SHORTWAVE DIVES INTO THE GREAT LAKES TROUGH AND TURNS THE UPPER FLOW OVER US MORE SOUTH-SOUTHWEST. MEANWHILE THE WEAK RIDGING BUILDS TO OUR NORTH AND TURNS OUR WIND EAST OR NORTHEAST. THIS WOULD MEAN INCREASED SKY COVER AND POSSIBLY A FEW SHOWERS LATE IN THE DAY AND AT NIGHT. MIXING ON THURSDAY SHOULD REACH TO AT LEAST 850 MB...WHERE TEMPS BETWEEN -1C AND +2C WOULD SUPPORT MAX TEMPS 55 TO 65. MIN TEMPS UPSTREAM SUPPORT THURSDAY NIGHT MIN TEMPS 35 TO 40...LOWER 40S ALONG THE COAST. CLOUDS AND A LIGHT NORTHEAST FLOW FRIDAY SHOULD KEEP TEMPS COOL...45 TO 55. SATURDAY-SUNDAY... AS NOTED ABOVE...UPPER TROUGH MOVES EAST FROM THE GREAT LAKES TO THE ATLANTIC COAST. UPPER JET FROM CENTRAL CANADA FEEDS AROUND THE UPPER TROUGH WITH LEFT EXIT REGION MOVING OVER THE CAROLINAS FRIDAY NIGHT/EARLY SATURDAY. THIS SUPPORTS THE IDEA OF A COASTAL LOW DEVELOPING. THE DEEP DIGGING UPPER TROUGH AND NEAR-SOUTH FLOW ALOFT WOULD SUGGEST A CLOSE-TO-THE-COAST TRACK A LA THE ECMWF. BUT WITH THE ECMWF TRENDING A LITTLE MORE PROGRESSIVE THAN LAST NIGHT THE TRACK FARTHER OFFSHORE IS STILL A POSSIBLE. CONFIDENT THAT THERE WILL BE UNSETTLED WEATHER THIS WEEKEND...WITH BEST CHANCE ALONG THE COASTAL PLAIN AND DIMINISHING POPS FARTHER NORTHWEST. WILL REFLECT THIS WITH LIKELY POPS SOUTHEAST GRADING TO CHANCE POPS NORTHWEST. GFS TRACK IS FARTHER OFFSHORE AND THEREFORE CLEARS SKIES FASTER. THE BLEND SHOULD SHOW MORE CLOUDS...AND MAY BE A LITTLE LESS COLD THAN A PURE GFS VALUE. LOW CONFIDENCE ON PTYPE. MUCH OF THE TIME SHOULD BE RAIN...BUT FIGURE WITH TEMPS FORECAST FALLING TO FREEZING OR BELOW WITH COLD AIR ALOFT THE RESULT WILL BE SOME SNOW ESPECIALLY IN THE NORTHWEST. ONE CHANGE FROM MODEL BLENDS...WE BUMPED WINDS UP 5-10 KNOTS REFLECTING 25 TO 35 KNOT WINDS ABOVE THE SURFACE SATURDAY AND 25 TO 40 KNOTS ON SUNDAY. HIGHEST WIND POTENTIAL WILL BE ALONG THE COAST. MONDAY-TUESDAY... HIGH PRESSURE BUILDS OVER THE REGION. LINGERING CLOUDS/COLD POOL ALOFT FROM THE DEPARTING UPPER LOW MAY KEEP SOME CLOUDS AROUND ESPECIALLY ON MONDAY. OTHERWISE FAIR AND DRY WITH TEMPS CLOSER TO NORMAL BY TUESDAY. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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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 WEDNESDAY NIGHT...MODERATE CONFIDENCE. TONIGHT... MAINLY VFR. CAN/T RULE OUT PATCHES OF LOW STRATUS OVERNIGHT...ESP ACROSS CT/RI AND SOUTHEAST MASS...BUT LOW CONFIDENCE ON THIS HAPPENING. S-SW WIND WILL INCREASE AND GUST AROUND 20 KTS ESP ACROSS SOUTHEAST TERMINALS. RAIN SHOWERS WILL BEGIN TO IMPACT NORTHWEST MASS/SOUTHWEST NH CLOSER TO DAYBREAK. WEDNESDAY AND WEDNESDAY NIGHT...MAINLY VFR. PATCHY MVFR CIGS/VSBYS IN SCT SHOWERS AS A COLD FRONT MOVES ACROSS THE AREA. THERE IS A LOW PROB FOR THUNDER ACROSS THE SOUTHEAST TERMINALS IN THE AFTERNOON AND EVENING HOURS. S-SW WIND WILL GUST UP TO 20-25 KT ESP ALONG THE S COAST...CAPE COD AND THE ISLANDS. THERE IS A LOW PROB FOR WIND GUSTS TO REACH 30 KTS. CONDITIONS IMPROVE FROM WEST TO EAST OVERNIGHT. KBOS...HIGH CONFIDENCE IN TAF. KBDL...HIGH CONFIDENCE IN TAF. LOW CONFIDENCE ON MVFR/IFR CONDITIONS IN LOW CLOUDS. OUTLOOK...THURSDAY THROUGH SUNDAY... THURSDAY-FRIDAY...HIGH CONFIDENCE. VFR. FRIDAY NIGHT THROUGH SUNDAY...LOW CONFIDENCE IN TIMING AND PRECIPITATION TYPE. MODERATE CONFIDENCE IN PRECIPITATION OCCURRENCE. CIGS/VSBYS LOWERING TO IFR COASTAL PLAIN AND MVFR NORTHWEST. COASTAL STORM PASSES LATER SATURDAY/SATURDAY NIGHT WITH A MIX OF RAIN AND SNOW ESPECIALLY MHT-ORH-BAF-BDL. PRECIPITATION TAPERS OFF ON SUNDAY. NORTH-NORTHEAST WINDS WITH GUSTS ALONG THE COAST 25-35 KNOTS SATURDAY. NORTHWEST WINDS SUNDAY WITH GUSTS 25 TO 30 KNOTS INLAND AND 30 TO 40 KNOTS ALONG THE COAST.
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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. SHORT TERM /THROUGH WEDNESDAY NIGHT/...HIGH CONFIDENCE. TONIGHT...S-SW WINDS INCREASING AHEAD OF A COLD FRONT. ANTICIPATE GUSTS UP TO 25 KT ON THE SOUTHERN WATERS AND SEAS BUILDING. SMALL CRAFTS HAVE BEEN ISSUED. WEDNESDAY AND WEDNESDAY NIGHT...EXPECT SW WINDS GUSTS BETWEEN 25 TO POSSIBLE 30KTS AND BUILDING SOUTHERN SEAS TO 6FT AHEAD OF AN APPROACHING COLD FRONT. THIS FRONT WILL CROSS THE WATERS DURING THE EVENING HOURS. BEHIND THE FRONT THE WIND WILL SWITCH TO THE WNW AND GUST UP TO 15 KTS...ALLOWING FOR SEAS TO RELAX. AS THE FRONT PASSES A FEW SHOWERS ARE POSSIBLE WHICH MAY REDUCE VSBYS. AN ISOLATED THUNDERSTORM CANNOT BE RULED OUT...WHICH COULD BRING GUSTS UP TO 30 KTS. OUTLOOK...THURSDAY THROUGH SUNDAY...MODERATE CONFIDENCE. THURSDAY AND FRIDAY...WEAK HIGH PRESSURE BUILDS NORTH OF THE WATERS. NORTHWEST WINDS THURSDAY BECOME NORTHEAST FRIDAY BUT REMAIN BELOW 20 KNOTS. SEAS LESS THAN 5 FEET. FRIDAY NIGHT THROUGH SUNDAY...COASTAL LOW PRESSURE DEVELOPS OFF THE CAROLINAS AND MOVES UP THE COAST. GREAT UNCERTAINTY IN THE EXACT TRACK. THE NEAREST FORECAST TRACK PASSES JUST OUTSIDE THE BENCHMARK...THE FARTHEST ONE PASSES PASSES ABOUT 400-500 MILES OUTSIDE THE BENCHMARK. AT LEAST MODERATE CONFIDENCE IN STRONG NORTH TO NORTHEAST WINDS WITH FREQUENT GUSTS SATURDAY 25 TO 35 KNOTS SHIFTING TO NORTHWEST 30 TO 40 KNOTS SUNDAY. A GALE WATCH/GALE WARNING MAY EVENTUALLY BE NEEDED DURING THE WEEKEND.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 5 AM TO 8 PM EDT WEDNESDAY FOR ANZ231>234. SMALL CRAFT ADVISORY FROM 5 AM WEDNESDAY TO 2 AM EDT THURSDAY FOR ANZ235-237. SMALL CRAFT ADVISORY FROM 2 AM TO 8 PM EDT WEDNESDAY FOR ANZ250. SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EDT THURSDAY FOR ANZ254. SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 AM EDT THURSDAY FOR ANZ255-256. && $$ SYNOPSIS...WTB/DUNTEN NEAR TERM...WTB/DUNTEN SHORT TERM...DUNTEN LONG TERM...WTB AVIATION...WTB/DUNTEN MARINE...WTB/DUNTEN

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