Area Forecast Discussion
Issued by NWS Boston, MA

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122 FXUS61 KBOX 060916 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 416 AM EST SAT FEB 6 2016 .SYNOPSIS...
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HIGH PRESSURE BRINGS DRY WEATHER THIS WEEKEND WITH ABOVE NORMAL TEMPERATURES BY SUNDAY. TWO DEVELOPING COASTAL STORMS MAY BRING ACCUMULATING SNOW ON MONDAY AND TUESDAY ESPECIALLY ACROSS EASTERN MA. AN ARCTIC COLD FRONT BRINGS MUCH CHILLIER AIR FOR THE END OF THE WEEK.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... 4AM UPDATE... A SPECIAL WEATHER STATEMENT CONTINUES THIS MORNING...AS CHILLY TEMPERATURES WILL ALLOW ANY STANDING WATER/SLUSH TO FREEZE SOLID. MOTORISTS SHOULD BE PREPARED FOR BLACK ICE. TODAY.... WEAK UPPER LEVEL TROUGH BEGINS TO SET UP OVER THE REGION TODAY. A PASSING HIGH TO OUR SOUTH WILL TIGHTEN THE PRESSURE GRADIENT ACROSS THE REGION FOR THIS AFTERNOON. ANTICIPATE GUSTS BETWEEN 15-20 MPH. WEAK SHORTWAVE WILL WILL ALSO BRING SOME MID-LEVEL MOISTURE INTO THE AREA RESULTING IN A FILTERED SUNSHINE. GUIDANCE DOES INDICATE TEMPERATURES IN THE UPPER 30S TO LOW 40S BUT WITH THE FRESH SNOW PACK THAT MAY BE A BIT TO OPTIMISTIC. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... TONIGHT... HIGH PRESSURE WILL MAINLY DOMINATE RESULTING IN QUIET WEATHER. HOWEVER PRESSURE GRADIENT WILL BE SLOW TO RELAX WHICH WILL LIMIT RADIATIONAL COOLING OVERNIGHT. TEMPS WILL DROP INTO THE 20S WITH PERHAPS LOW READINGS IN AREAS WHERE THE WIND WILL BE CALM. TOMORROW... LOW PRESSURE SYSTEM TO THE NORTH WILL DRAG A WEAK COLD FRONT THROUGH THE REGION ON SUNDAY. THIS FRONT WILL BE DRY BUT MAY BRING IN SOME CLOUDS. WESTERLY FLOW WILL DOMINATE IN THE AFTERNOON WHICH WILL ALLOW FOR TEMPERATURES TO WARM IN TO THE 40S. HELP AID IN MELTING SOME OF THE SNOW. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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BIG PICTURE... LONGWAVE PATTERN SHOWS RIDGE WEST/TROUGH EAST AS BEFORE...WITH INCREASING AMPLITUDE EARLY WEEK AND DECREASING AMPLITUDE LATE WEEK. OVERALL A COLD AND UNSETTLED PATTERN FOR SOUTHERN NEW ENGLAND. AT SHORTER WAVE SCALES WE SEE THREE SHORTWAVES AFFECTING THE PATTERN. THE FIRST IS IN THE LOWER MISS RIVER VALLEY AND GENERATES COASTAL LOW PRESSURE OFF THE CAROLINAS SUNDAY. THIS SWINGS WIDE OF OUR AREA...CROSSING ABOUT 4 DEGREES SOUTH OF THE 40N/70W BENCHMARK...AND THEN SWEEPS NORTHEAST JUST SOUTH OF NOVA SCOTIA. THE SECOND SHORTWAVE IS MOVING ASHORE IN THE PACIFIC NORTHWEST AND WILL CARVE A DEEP COLD TROUGH OVER THE EASTERN USA DURING THE EARLY WEEK. THE THIRD SHORTWAVE IS ALONG THE ARCTIC OCEAN COASTLINE AND WILL DROP SOUTH INTO THE USA MIDWEEK. OPERATIONAL GUIDANCE MASS FIELDS ARE SIMILAR ON THE BROAD SCALE MOST OF THE PERIOD. BUT THERE ARE DIFFERENCES IN THE DETAILS...ESPECIALLY REGARDING THE SECOND SHORTWAVE AND ITS DEVELOPING COASTAL SYSTEM TUESDAY. THIS SECOND SHORTWAVE WAS JUST COMING ASHORE AT MEASUREMENT TIME LAST NIGHT. THE 12Z SATURDAY MODELS SHOULD HAVE A BETTER READ ON THE SHORTWAVE AND ITS EFFECTS. WE CONTINUE TO FAVOR A MODEL BLEND ESPECIALLY USING THE GFS AND ECMWF. THE DAILIES... SUNDAY NIGHT-MONDAY... COASTAL STORM PASSES WELL OFFSHORE...SOME 4 DEGREES SOUTH OF THE BENCHMARK. NORMALLY THAT WOULD MEAN A SWING AND A MISS FOR STRIKE THREE. BUT HIGH PRESSURE BUILDS SOUTH FROM QUEBEC AND ESTABLISHES A PRESSURE GRADIENT THAT SHOULD BRING A NORTHEAST MARINE FLOW WITH DELTA OF 13-15C. THIS SHOULD AT LEAST BRING INCREASING CLOUDS OVERNIGHT AND MONDAY. LESS CONFIDENCE ON PCPN GIVEN MEDIOCRE FORCING AND CHANGING RUN-TO-RUN AMOUNTS. MODELS HAVE BACKED OFF ON QPF DURING MONDAY WITH MAIN FOCUS ON CAPE AND ISLANDS...POSSIBLY EASTERN MASS. WE HAVE BACKED OFF ONSET OF POPS UNTIL 06-12Z MONDAY AND VALUE OF POPS BY ABOUT 20 PERCENT. THIS STILL BRINGS POTENTIAL FOR SEVERAL INCHES IN EASTERN MASS WITH HIGHEST AMOUNTS CAPE COD/PLYMOUTH CO AREA. MONDAY NIGHT-TUESDAY... SECOND SHORTWAVE DIGS OVER THE MIDWEST WITH SURFACE LOW REDEVELOPMENT ALONG THE MID ATLANTIC COAST. THIS NEW COASTAL LOW THEN MOVES PAST NEW ENGLAND. BETTER DYNAMICS AND RESULTING LIFT SHOULD BE IN PLACE AND WITH DEEPER MOISTURE WOULD EXPECT THIS TO BE A BETTER CHANCE OF PCPN THAN THE MONDAY OFFSHORE SYSTEM. BUT THE RESPONSIBLE SHORTWAVE IS JUST NOW MOVING ASHORE AS NOTED ABOVE. SO STILL SOME UNCERTAINTY WITH THIS SYSTEM AND ITS POTENTIAL. WE WILL BRING A PERIOD OF LIKELY POPS AS THE SYSTEM MOVES THROUGH. WEDNESDAY THROUGH FRIDAY... UPPER TROUGH WITH ITS COLD POOL ALOFT AND CLOUD SHIELD LINGER WEDNESDAY. THE ARCTIC SHORTWAVE THEN SWINGS THROUGH ON THURSDAY. EXPECT QUITE A FEW CLOUDS DURING THIS PERIOD WITH A CHANCE OF SNOW SHOWERS. CLIPPER LOW THEN DROPS SOUTHEAST FROM NORTHERN ONTARIO FRIDAY AND BRINGING MORE CLOUDS AND SCATTERED SNOW SHOWERS. MIXED LAYER REACHES EITHER SIDE OF 925 MB EACH DAY...A LITTLE HIGHER THURSDAY BEHIND THE ARCTIC SHORTWAVE AND SURFACE FRONT. TEMPS ALOFT AT THE TOP OF THE LAYER SUPPORT 30S WEDNESDAY...20S WEST/32 EAST THURSDAY...AND 20S TO NEAR 30 FRIDAY. AS NOTED EARLIER...COLD AND UNSETTLED.
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&& .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
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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 SUNDAY/... TODAY...HIGH CONFIDENCE. MAINLY VFR. WINDS SHIFT TO THE SW. A FEW GUSTS BETWEEN 15-20 MPH ARE POSSIBLE IN THE AFTERNOON. TONIGHT INTO SUNDAY...HIGH CONFIDENCE. VFR. KBOS TERMINAL...HIGH CONFIDENCE IN TRENDS. KBDL TERMINAL...HIGH CONFIDENCE IN TRENDS. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... TWO POTENTIAL STORMS DURING THIS PERIOD...EITHER COULD BRING IFR/LIFR CIGS AND VSBYS IN SNOW. THE FIRST CHANCE FOR THIS WILL BE MONDAY...WITH BEST CHANCE ON CAPE COD AND ISLANDS. NORTH-NORTHEAST WINDS WILL GUST TO 35 KNOTS ALONG THE EASTERN MASS COAST. THE SECOND CHANCE WILL BE MONDAY NIGHT AND TUESDAY WITH ALL OF SOUTHERN NEW ENGLAND UNDER THE GUN. CONDITIONS IMPROVE WEDNESDAY TO MVFR CIGS WITH SCATTERED SNOW SHOWERS.
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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 SUNDAY/...HIGH CONFIDENCE. LINGERING SWELLS AND SEAS WILL BEGIN TO SUBSIDE TODAY. SCA LINGERS FOR A PORTION OF THE DAY...BUT MAY BE ABLE TO BE DROPPED SOONER. HIGH PRESSURE WILL BUILD OVER THE WATERS THROUGH THE WEEKEND. AN INCREASE IN THE GRADIENT WILL ALLOW FOR SOME GUSTY WINDS ACROSS THE NORTHERN WATERS LATE THIS AFTERNOON INTO TONIGHT. SEAS WILL BUILD IN RESPONSE. SCA MAY BE NEEDED TONIGHT AND INTO TOMORROW FOR BUILDING SEAS IN RESPONSE TO GUSTY WINDS. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...MODERATE CONFIDENCE... SUNDAY NIGHT-MONDAY...A DEVELOPING GALE CENTER WILL PASS WELL OFFSHORE SOUTHEAST OF NANTUCKET...BUT STRONG WINDS WILL EXTEND AN UNUSUAL DISTANCE OUT FROM THE WEATHER SYSTEM. NORTHEAST WINDS OVER THE WATERS WILL INCREASE TO GALE FORCE. THIS WILL BUILD SEAS OF 7 TO 11 FEET ON THE EXPOSED WATERS. A GALE WARNING WILL EVENTUALLY BE NEEDED FOR LATE SUNDAY NIGHT AND MONDAY. ALSO EXPECT REDUCED VSBYS IN RAIN AND SNOW. MONDAY NIGHT-TUESDAY...A SECOND WEATHER SYSTEM WILL DEVELOP ALONG THE MID ATLANTIC COAST AND MOVE OUTSIDE NANTUCKET. THIS WILL BRING ANOTHER PERIOD OF NORTHEAST WINDS WITH GUSTS OVER 25 KNOTS. THERE REMAIN MANY QUESTIONS ABOUT THIS NEXT SYSTEM...AS WELL AS LOW POTENTIAL FOR WINDS REACHING 35 KNOTS. SEAS WILL REMAIN AT 7 TO 11 FEET. WEDNESDAY... WINDS DIMINISH AS THE SECOND COASTAL STORM MOVES OFF. WIND SPEEDS SHOULD GO BELOW 25 KNOTS. ROUGH SEAS WILL LINGER MUCH OF THE DAY ESPECIALLY ON THE SOUTHERN EXPOSED WATERS.
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&& .TIDES/COASTAL FLOODING... MONDAY... THERE IS A FAIRLY HIGH ASTRO TIDE OF 11.2 IN BOSTON LATE MONDAY MORNING. NORTHEAST WIND GUSTS OF 30 TO 40 KNOTS FROM LARGE CIRCULATION OF THE INTENSIFYING OCEAN STORM WILL LIKELY RESULT IN A 1 TO 1.5 SURGE. SEAS SHOULD BE BUILT UP TO BETWEEN 10 AND 15 FEET BY THEN...SO FEEL THERE IS A DECENT SHOT FOR POCKETS OF MINOR COASTAL FLOODING ALONG EASTERN MA COAST. THERE IS A LOW RISK FOR POCKETS OF MODERATE COASTAL FLOODING...IF THE STORMS ENDS UP A BIT FASTER AND TRACKING FURTHER WEST THAN CURRENT GUIDANCE INDICATES. MONDAY NIGHT AND TUESDAY... MAIN CONCERN IS IF WE END UP WITH A SECOND AREA OF STRONG LOW PRESSURE TRACKING UP THE COAST...WHICH COULD IMPACT ADDITIONAL HIGH TIDE CYCLES. LARGE SPREAD IN THE GUIDANCE ON WHETHER OR NOT THIS HAPPENS. IF SO...WILL HAVE TO WATCH THE TUESDAY NOON HIGH TIDE CYCLE ACROSS EASTERN MA AS BOSTON HAS AN 11.5 ASTRO TIDE. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR ANZ250. SMALL CRAFT ADVISORY UNTIL 7 AM EST THIS MORNING FOR ANZ251. SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ254- 255. SMALL CRAFT ADVISORY UNTIL 10 AM EST THIS MORNING FOR ANZ256. && $$ SYNOPSIS...WTB/DUNTEN NEAR TERM...DUNTEN SHORT TERM...DUNTEN LONG TERM...WTB AVIATION...WTB/DUNTEN MARINE...WTB/DUNTEN TIDES/COASTAL FLOODING...

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