Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 290556 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1256 AM EST THU JAN 29 2015 .SYNOPSIS... HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL BUILD OVER NEW ENGLAND TONIGHT AND THURSDAY...THEN MOVE EAST THURSDAY EVENING. THIS WILL BRING VERY COLD AIR FOR TONIGHT AND THEN MODERATION ON THURSDAY. AN ALBERTA CLIPPER WILL MOVE EAST FROM THE PLAINS AND BRING A CHANCE OF SNOW THURSDAY NIGHT THROUGH FRIDAY NIGHT. VERY COLD CONDITIONS LINGER THROUGH THE WEEKEND. ANOTHER STORM MAY BRING SNOW TO THE REGION SUNDAY NIGHT AND MONDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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1250 AM UPDATE... OCEAN EFFECT CLOUDS STILL LOCKED IN ACROSS THE CAPE AND ISLANDS BUT CLOUDS ARE BEGINNING TO SOUTH AND EXPECT GRADUAL CLEARING TROUGH DAYBREAK. OTHERWISE...SKIES ARE CLEAR. GOOD RADIATIONAL COOLING WILL RESULT IN VERY COLD TEMPS WITH LOWS DROPPING BELOW ZERO IN THE COLDER SPOTS IN W MA AND E MA. WILL MAKE A FEW MODIFICATIONS TO LOW TEMPS.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... THURSDAY...HIGH PRESSURE OVERHEAD AND LOW DEWPOINTS SHOULD RESULT IN A DRY WEATHER DAY. AS THE HIGH MOVES OFFSHORE...MOISTURE FROM THE NEXT SYSTEM WILL START STREAMING IN AT HIGH LEVELS. THE AFTERNOON SHOULD FEATURE INCREASING/THICKENING HIGH CLOUDS WHICH MAY DIM THE SUN. TEMPERATURES AT 950 MB WILL BE AROUND -5C AND WOULD SUPPORT SURFACE MAX TEMPS EITHER SIDE OF 30F. CAPE COD AND ISLANDS MAY INCH A TAD HIGHER TO THE MID 30S. THURSDAY NIGHT AND FRIDAY... WE CONTINUE TO WATCH DISTURBANCES IN BOTH THE NORTHERN AND SOUTHERN STREAMS WHICH ARE EXPECTED TO PHASE BY THURSDAY AND EVOLVE INTO AN ELONGATED TROUGH OVER THE EASTERN USA BY FRIDAY. THE PRIMARY LOW ACTUALLY RACES TOWARD THE GREAT LAKES THURSDAY NIGHT. BUT THE SOUTHERN UPPER JET CURLS AROUND THE ELONGATED TROUGH AND EXTENDS ITS LEFT EXIT REGION EITHER OVER OR JUST SOUTH OF SOUTHERN NEW ENGLAND. THIS SHOULD SUPPORT A COASTAL DEVELOPMENT OFF OUR COAST ON FRIDAY. A MORE NORTHERLY DEVELOPMENT WOULD FOCUS LOW LEVEL LIFT AND PRECIPITATION FARTHER NORTH...A MORE SOUTHERLY DEVELOPMENT WOULD BRING THINGS FARTHER SOUTH. THE GFS SUGGESTS THE NORTHERN SOLUTION...THE ECMWF AND GGEM DEVELOP THE SECONDARY SOUTHEAST OF NANTUCKET. WE HAVE OPTED MORE TOWARD THE SOUTHERN DEVELOPMENT. THIS WOULD SUPPORT ROUGHLY 0.20 TO 0.30 INCHES OF PCPN DURING THURSDAY NIGHT AND FRIDAY. THERMAL PROFILES MOSTLY FAVOR SNOW...BUT WITH SOME POTENTIAL FOR RAIN MIXING IN MIDDAY BEFORE THE SECONDARY DEVELOPS AND PULLS COLDER AIR IN. THIS SUGGESTS SNOW ACCUMULATIONS OF 2-5 INCHES WITH THE THE EVENTUAL NEED FOR A WINTER WEATHER ADVISORY WHEN THE STORM GETS CLOSER. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... * SNOW EASTERN AREAS FRI NIGHT DIMINISHES AS LOW EXITS THE AREA * ARCTIC AIR INVADES NEW ENGLAND THIS WEEKEND ON BRISK NW WINDS * COASTAL STORM POSSIBLE SUN NIGHT-MON, BUT LOW CONFIDENCE OVERVIEW...LOW PRESSURE CENTER IS EXPECTED TO BE OFF THE MAINE COAST FRI NIGHT. SNOW IS MOST LIKELY EASTERN AREAS...ESPECIALLY COASTAL AREAS CLOSER TO THIS LOW SUCH AS BOSTON AND POINTS NORTH. THE SNOW IS FORECAST TO GRADUALLY WIND DOWN DURING THE NIGHT FRI NIGHT AS THE LOW PULLS AWAY. ARCTIC AIR WILL USHER INTO NEW ENGLAND BEHIND THIS DEPARTING LOW FOR THE WEEKEND WITH BLUSTERY NW WINDS AND FRIGID WIND CHILLS. WINDS CHILL ADVISORIES MAY BE NEEDED FRI NIGHT. A MORE VIGOROUS SHORTWAVE DIVES INTO THE EASTERN STATES SUN NIGHT AND MONDAY. MODELS CONTINUE TO STRUGGLE WITH REGARDS TO THE AMPLITUDE OF THE TROUGH AND THE CORRESPONDING SURFACE LOW AND TRACK. THE LATEST 28.12Z OPERATIONAL RUNS OF THE GFS AND ECMWF NOW ARE MORE PROGRESSIVE AND SHOW A WEAKER SURFACE LOW AND WELL EAST OF THE BENCHMARK. HOWEVER BOTH MODELS DID JUST THE SAME SEVERAL DAYS BEFORE OUR RECENT BLIZZARD...SO WE CANNOT HAVE ANY DEGREE OF CONFIDENCE WITH EITHER A HIT OR A MISS THIS FAR OUT IN TIME. WE WILL CONTINUE TO USE A MODEL BLEND INCLUDING THEIR ENSEMBLES AS THERE IS A HIGH DEGREE OF SPREAD AMONGST THEM. HIGH PRESSURE WILL BUILD INTO THE REGION TUE-WED AS THE SHORTWAVE/LOW MOVES EAST WITH HIGH PRESSURE TAKING OVER...BRINGING QUIET WEATHER MID WEEK. YET ANOTHER CHANCE OF SNOW OR A WINTRY MIX ENTERS THE PICTURE BY THU. AN ACTIVE WINTERTIME PATTERN INDEED! && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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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 TONIGHT...HIGH CONFIDENCE. TODAY...VFR. INCREASING CLOUDS ABOVE 10 K FT IN THE AFTERNOON. LIGHT WIND TONIGHT AND FRIDAY...CIGS LOWER OVERNIGHT TO MVFR/IFR IN OCCASIONAL SNOW. SOME RAIN MAY MIX IN ALONG THE IMMEDIATE S COAST AND ESPECIALLY THE CAPE/ISLANDS LATE TONIGHT AND FRI MORNING. SNOW DIMINISHES FRI AFTERNOON BUT LINGERING ACROSS PORTIONS OF E MA. WINDS SHIFT TO NORTHWEST DURING THE AFTERNOON. GUSTS TO 25-30 KT AND VFR CIGS DEVELOPING IN THE CT VALLEY BY MID/LATE AFTERNOON. KBOS TAF...HIGH CONFIDENCE...BUT LOWER CONFIDENCE ON EXACT TIMING OF SNOW AND LOWER CIGS/VSBYS. KBDL TAF...HIGH CONFIDENCE...BUT LOWER CONFIDENCE ON EXACT TIMING OF SNOW AND LOWER CIGS/VSBYS. OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/... FRIDAY NIGHT...LOW CONFIDENCE. VFR WEST. POSSIBLE IFR TO START FOR EASTERN LOCALES...BUT WITH IMPROVEMENT EXPECTED OVERNIGHT. SATURDAY-SUNDAY...HIGH CONFIDENCE. VFR. GUSTY NORTHWEST WINDS 25-35 KNOTS SATURDAY...LIGHTER WINDS SUNDAY. SUNDAY NIGHT-MONDAY...LOW CONFIDENCE. COASTAL LOW TRACK HIGHLY UNCERTAIN. JUST WAY TOO EARLY TO HAVE ANY CONFIDENCE ON VFR OR IFR THIS PERIOD.
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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/...HIGH CONFIDENCE TONIGHT AND THURSDAY...MODERATE CONFIDENCE THURSDAY NIGHT AND FRIDAY. 10 PM UPDATE...DROPPED SCA FOR ANZ256 AS SEAS HAVE DROPPED BELOW 5 FT. TONIGHT...DIMINISHING NORTHWEST WIND. DIMINISHING FREEZING SPRAY POTENTIAL. STILL ROUGH SEAS WITH 5-7 FEET ON THE OUTER WATERS AS WELL AS PARTS OF CAPE COD BAY AND MASSACHUSETTS BAY. WE WILL KEEP THE SMALL CRAFT ADVISORY IN EFFECT FOR THESE WATERS THROUGH THE PART OR ALL OF THE NIGHT. THURSDAY...HIGH PRESSURE BUILDS OVER THE WATERS. THIS SHOULD BRING LIGHT WIND WHICH WILL ALLOW SEAS TO SUBSIDE. A SMALL CRAFT ADVISORY WILL LINGER INTO THE MORNING ON THE OUTER WATERS EAST OF MASSACHUSETTS. THURSDAY NIGHT-FRIDAY...LOW PRESSURE FROM THE MIDWEST WILL REDEVELOP OVER THE COASTAL WATERS FRIDAY. SNOW WILL MOVE IN AFTER MIDNIGHT AND THROUGH THE MORNING FRIDAY WITH REDUCED VISIBILITY. SOUTH WINDS WILL SLOWLY INCREASE WITH GUSTS TO 20 KNOTS BY FRIDAY MORNING. WINDS WILL THEN SHIFT TO NORTHWEST FRIDAY AFTERNOON WITH POTENTIAL FOR 30 KNOT GUSTS BY EVENING. OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/...MODERATE CONFIDENCE FRI- SAT...LOW CONFIDENCE SUN-MON. FRIDAY...LOW PRES WILL CROSS THE WATERS. EXPECT REDUCED VSBYS IN SNOW. EXPECT WINDS TO SHIFT TO NW AND INCREASE FRI NIGHT...WITH GALES POSSIBLE OVER THE WATERS. FREEZING SPRAY WILL LIKELY DEVELOP FRI NIGHT. SATURDAY...NW GALES EXPECTED WITH POTENTIAL FOR FREEZING SPRAY. HIGH SEAS FORECAST...10-12 FT OFFSHORE WATERS. WINDS WILL BEGIN TO DIMINISH SAT NIGHT WITH A CORRESPONDING LOWERING OF SEAS. SUNDAY...WINDS AND SEAS AT SMALL CRAFT ADVISORY LEVELS EARLY SUNDAY...BUT WILL DIMINISH THROUGH THE DAY. SUNDAY NIGHT-MONDAY...MUCH WILL DEPEND ON STRENGTH AND TRACK OF A POSSIBLE COASTAL LOW SO TAKE THE OFFICIAL FORECAST OF WINDS/SEAS DURING THIS PERIOD WITH A GRAIN OF SALT. A LOW CLOSER TO THE COAST WOULD SPELL A SIGNIFICANT IMPACT TO MARINERS...WHILE AN OFFSHORE/WEAKER TRACK WOULD HAVE MUCH LESS IMPACT. TOO EARLY TO SAY EITHER WAY...SO WENT WITH A MODEL BLEND. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL NOON EST TODAY FOR ANZ250-254. SMALL CRAFT ADVISORY UNTIL 4 AM EST EARLY THIS MORNING FOR ANZ231-251. SMALL CRAFT ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR ANZ255.
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&& $$ SYNOPSIS...WTB/SIPPRELL/GREGORIA NEAR TERM...KJC SHORT TERM...WTB LONG TERM...GREGORIA AVIATION...KJC/SIPPRELL/GREGORIA MARINE...WTB/KJC/GREGORIA

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