Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 032117 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 417 PM EST TUE MAR 3 2015 .SYNOPSIS...
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A STORM SYSTEM MOVING FROM THE GREAT LAKES INTO CANADA WILL BRING A MIXTURE OF PRECIPITATION TONIGHT AND EARLY WEDNESDAY. WEAK LOW PRESSURE PASSING SOUTH OF NEW ENGLNAD WILL BRING ANOTHER ROUND OF SNOW WEDNESDAY NIGHT AND THURSDAY. HIGH PRESSURE THEN BRINGS DRY COLD CONDITIONS OVER THE WEEKEND. HIGH PRESSURE MOVES IN FOR FRIDAY THROUGH THIS WEEKEND...BRINGING DRY BUT COLD CONDITIONS. A WEAKENING FRONT MAY BRING SOME LIGHT SNOW SHOWERS ON MONDAY.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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THROUGH 7 PM... OBSERVATIONS AT 3 PM SHOWED LIGHT SNOW MOVING ACROSS THE CATSKILLS AND CENTRAL NEW YORK. THE TREND ON THIS LEADING EDGE WOULD BRING IT THROUGH THE CT VALLEY BY 5 PM AND THE COASTAL PLAIN AROUND 7 PM. DRY AIR OVER SOUTHERN NEW ENGLAND MAY ERODE THE LEADING EDGE AND SLOW THE ONSET A LITTLE. BUT THE TREND CONTINUES TO SHOW LIGHT SNOW DEVELOPING DURING THE EVENING RUSH HOUR. TONIGHT... HEAVIER PCPN LAGS THE LEADING EDGE BY 2-3 HOURS. EXPECT A HEAVIER BURST OF SNOW TO LEAVE SOME ACCUMULATION DURING THE FIRST PART OF THE NIGHT. QPF BASED ON HPC PROJECTIONS COMBINES WITH EXPECTED TEMPERATURES TO SUGGEST 1-3 INCHES ACCUMULATION...HEAVIEST IN THE WEST. OBSERVATIONS OF SLEET AND FREEZING RAIN IN CENTRAL PA POINT TO ADVANCING WARMER AIR ALOFT OF THE SURFACE LAYER. MODEL DATA SHOWS A 40 KNOT JET FROM THE OHIO VALLEY AND A 50 KNOT COASTAL JET AT 925 MB MOVING OVER THE REGION AND SUPPORTING THE WARM ADVECTION ALOFT. WITH NO COLD AIR DAMMING IN PLACE WE SHOULD EXPECT SLOWLY RISING TEMPS AT THE SURFACE OVERNIGHT...ALL OF WHICH SUPPORTS THE IDEA OF CHANGING PTYPE OVERNIGHT. WE USED A NON-DIURNAL TEMPERATURE TREND. BUFKIT SHOWS TEMPS IN THE 30S OVERNIGHT AROUND 925 MB AND A NEAR ISOTHERMAL LAYER TO THE SURFACE. SO OVERNIGHT TEMPERATURES SHOULD GO NO HIGHER THAN THE 30S.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
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COLD FRONT MOVES THROUGH SOUTHERN NEW ENGLAND DURING THE MORNING. THAT SHOULD END MOST OF THE PCPN. THE BEST CHANCE OF PCPN WOULD BE ALONG THE SOUTH COAST...WITH TEMPS WARM ENOUGH FOR RAIN. UPPER FLOW WILL BE WEST-TO-EAST AHEAD OF ANOTHER UPPER TROUGH SWINGING ACROSS THE GREAT LAKES. THE WEDNESDAY COLD FRONT WILL LINE UP WITH THAT UPPER FLOW...STALLING THE FRONT SOUTH OF NEW ENGLAND. MEANWHILE THE UPPER JET IN THE FLOW MOVES ACROSS NEW ENGLAND AND PLACES US IN ITS RIGHT ENTRANCE REGION. THIS WILL GENERATE SUPPORT FOR A WAVE ON THE FRONT PUSHING PCPN NORTH AGAIN WEDNESDAY NIGHT. AT THE SAME TIME...WINDS SHIFTING TO NORTH WILL DRAW COLDER AIR SOUTH ACROSS THE REGION AGAIN. SO ANY DEVELOPING PCPN WOULD CHANGE TO FREEZING RAIN AND THEN SNOW. QUESTION REMAINS AS TO WHETHER THE COLD AIR WILL BE DRY ENOUGH TO SUPPRESS THE PCPN SHIELD FARTHER SOUTH. THIS MAY LIMIT ANY SIGNIFICANT PCPN TO THE SOUTH COAST OR EVEN JUST OFFSHORE. WE WILL GO WITH CATEGORICAL POPS ALONG THE SOUTH COAST...LIKELY POPS ACROSS CT-RI-SE MASS...AND CHANCE POPS FARTHER NORTH. BASED QPF ON HPC VALUES. DUE TO THE COMBINATION OF EXPECTED PCPN AND EXPECTED TEMPS...WE HAVE ISSUED A WINTER STORM WATCH ALONG THE SOUTH COAST INCLUDING CAPE COD AND ALL THE ISLANDS. THIS WILL ALSO INCLUDE KENT COUNTY RI.
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/...
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OVERVIEW... UPPER LEVEL PATTERN BEGINNING TO SHOW A FEW SIGNS OF CHANGE WITH THE CHANGING SEASON...THOUGH DOES LOOK LIKE SIMILAR COLD PATTERN REMAINS FOR MUCH OF THE NORTHEAST U.S. THROUGH A GOOD PORTION OF THIS LONG TERM TIMEFRAME. ONE NOTICEABLE CHANGE IS THE DRYING OF THE SAME PATTERN. NE-SW ELONGATED LONG WAVE TROUGH WORKS E WED NIGHT...BUT WILL STAY IN SW FLOW ALOFT. BY THU...THOUGH...SHORT WAVE DIGS IN THIS GENERAL LONG WAVE PATTERN AND PUSHES E DURING THU. LONG WAVE TROUGH SHIFTS OFFSHORE LATE THU/THU NIGHT...SO EXPECT PRECIP TO END. FOR FRIDAY INTO THIS WEEKEND...UPPER PATTERN FLATTENS OUT ACROSS THE NORTHERN STREAM...SO EXPECT GENERALLY DRY CONDITIONS EXCEPT FOR A FEW QUICK MOVING CLIPPER TYPE SYSTEMS WHICH APPEAR TO KEEP MOST OF THEIR PRECIP N OF THE REGION. WILL STILL SEE COLDER THAN NORMAL TEMPS HOWEVER. USED A BLEND OF AVAILABLE GUIDANCE FOR THIS FORECAST...WHICH HAD GOOD CONTINUITY TO THE PREVIOUS PACKAGE. DETAILS... THURSDAY... STALLED FRONTAL SYSTEM JUST OFF THE SOUTHERN NEW ENGLAND COAST WILL KEEP PRECIP LINGERING ACROSS MOST OF THE REGION AS COLDER AIR RETURNS. MIXED PRECIP CHANGES BACK TO SNOW OVERNIGHT...THOUGH COULD SEE A PERIOD OF FREEZING RAIN/SLEET THROUGH ABOUT MIDNIGHT OR SO. GOOD BAROCLINIC ZONE REMAINS ESPECIALLY FROM THE MASS PIKE SOUTH DURING THIS TIMEFRAME ALONG WITH PRETTY GOOD MOISTURE CONVERGENCE AND OVERRUNNING RETURNS. SLIGHTLY HIGHER QPF FROM THE PREVIOUS FORECAST...RANGING FROM 0.2 TO 0.3 INCHES ACROSS N MA TO 0.5 TO 0.8 INCHES FROM N CT/RI/SE MA. SURFACE REFLECTION/WEAK WAVE WILL RIDE ALONG THE STALLED FRONT LATE WED NIGHT/THU. THIS...ALONG WITH COLDER AIR WORKING IN...WILL SEE SNOW PICK UP IN INTENSITY AFTER MIDNIGHT THROUGH THU MORNING WHERE THE BEST LIFT AND MOISTURE ARE LOCATED...GENERALLY S OF THE MASS PIKE. WILL LIKELY NEED HEADLINES FOR THIS EVENT...THOUGH HOLDING OFF CONSIDERING TODAY/S HEADLINES ALREADY IN PLACE. CONTINUE TO HIGHLIGHT IN THE HAZARDOUS WEATHER OUTLOOK. THURSDAY NIGHT... UPPER TROUGH SHIFTS E...PUSHING THE FRONT OFFSHORE OVERNIGHT. SOME MODEL TIMING DIFFERENCES THOUGH ALL DO TEND TO PUSH PRECIP OFFSHORE RATHER QUICKLY OVERNIGHT. ANOTHER SHOT OF ARCTIC AIR WORKS IN WITH OVERNIGHT LOWS IN THE SINGLE DIGITS FOR MOST AREAS EXCEPT THE TEENS ALONG THE S COAST. FRIDAY THROUGH MONDAY... A BROAD UPPER TROUGH CONTINUES ACROSS CENTRAL AND EASTERN CANADA... KEEPING THE REGION IN BELOW NORMAL TEMPS THROUGH THIS TIMEFRAME. FAST FLOW ALOFT ALSO BRINGS WEAK SYSTEMS TOWARD THE REGION...THOUGH LOOKS LIKE ONLY LIGHT PRECIP WITH W-NW FLOW IN PLACE WITH THESE CLIPPER TYPE SYSTEMS. LARGE HIGH PRES BUILDS TO THE SW OF THE REGION FRI WITH TEMPS RUNNING 15 TO 20 DEGS BELOW THOUGH NOT CLOSE TO LOW MAX TEMP RECORDS EXCEPT FOR PROVIDENCE /VERY LOW MAX TEMP RECORDS FOR MARCH 6/. AS THE HIGH SHIFTS S OF THE REGION THIS WEEKEND...TEMPS REBOUND A BIT. THEY LOOK REMAIN BELOW NORMAL BUT WILL PROBABLY SEE HIGHS IN THE 30S AS WINDS BACK TO SW. A COLD FRONT APPROACHES LATE SAT/SAT NIGHT BUT MOST OF THE ENERGY AND PRECIP LOOKS TO REMAIN ACROSS NORTHERN NEW ENGLAND. WILL SEE SOME CLOUDS AND A WIND SHIFT TO W MOVES ACROSS BY SUNDAY MORNING AS THE FRONT WEAKENS. ANOTHER CLIPPER SYSTEM QUICKLY MOVES N OF THE GREAT LAKES BY MONDAY MORNING...WITH ANOTHER FRONT CROSSING LATE MON/MON NIGHT. CARRIED SLIGHT CHANCE POPS FOR MAINLY SNOW SHOWERS...BUT MAY SEE PRECIP MAY WASH OUT AS IT APPROACHES IN THE DRY W-NW FLOW.
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&& .AVIATION /21Z TUESDAY 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/... 18Z TAF UPDATE... NO MAJOR ADJUSTMENTS. THIS EVENING INTO EARLY WEDNESDAY...MODERATE CONFIDENCE. ALTHOUGH THERE IS HIGH CONFIDENCE IN OVERALL TRENDS...THERE IS LOWER CONFIDENCE IN EXACT TIMING. CIGS WILL LOWER TO MVFR THIS EVENING AND AREAS OF SNOW WILL DEVELOP FROM W-E FROM THROUGH 8 PM. ACCUMS RANGE FROM 1-3 INCHES WIDESPREAD ALTHOUGH SOME 4+ IS POSSIBLY IN THE HIGHER TERRAIN OF THE EAST SLOPES OF THE BERKSHIRES AND THE WORCESTER HILLS. IFR CONDITIONS AT TIMES LIKELY ESPECIALLY IN LOWER VSBYS. THE SNOW TRANSITIONS TO A PERIOD OF SLEET...TO FREEZING RAIN...TO STRAIGHT RAIN THROUGH THE OVERNIGHT HOURS FROM S-N. SOME ICE ACCUMS POSSIBLE...MAINLY IFR/MVFR CONDITIONS. WEDNESDAY...MODERATE CONFIDENCE. SOME GRADUAL IMPROVEMENT IS EXPECTED DURING THE MORNING HOURS FROM N-S ALTHOUGH IT/S LIKELY MVFR/IFR CONDITIONS LINGER CLOSER TO THE S COAST EVEN AS RAIN SLOWS AND FOG/DRIZZLE DEVELOPS. SOME VFR IS NOT OUT OF THE QUESTION DURING THE DAY FOR TAF SITES N OF THE MASS PIKE. WEDNESDAY NIGHT... EXPECT CONDITIONS TO DETERIORATE TO MVFR BY 05Z IN MIXED PRECIP CHANGING OVER TO SNOW FROM N-S. WILL VSBYS LOWER TO IFR-VLIFR ACROSS N CT/RI/SE MA IN PERIODS OF SN/+SN AFTER 06Z-08Z AND CONTINUE THROUGH THU MORNING. KBOS TAF...HIGH CONFIDENCE IN OVERALL TRENDS...LOWER CONFIDENCE IN EXACT TIMING. KBDL TAF...HIGH CONFIDENCE IN OVERALL TRENDS...LOWER CONFIDENCE IN EXACT TIMING. OUTLOOK...THURSDAY THROUGH SATURDAY... THURSDAY...MODERATE CONFIDENCE. CONDITIONS SHOULD SLOWLY IMPROVE FROM N-S DURING THU AFTERNOON...BUT LOWER CIGS/VSBYS CONTINUE ALONG S COAST INTO THU EVENING. NW WINDS GUSTING TO 20-25 KT ALONG THE COAST. THURSDAY NIGHT...MODERATE CONFIDENCE. MAINLY VFR ACROSS MOST AREAS. RI/SE MA...IFR CONDITIONS EARLY IN LEFTOVER -SN...THEN IMPROVING TO VFR. N-NW GUSTING TO 25-30 KT FOR ALONG THE COAST...DIMINISHING AFTER MIDNIGHT. FRIDAY THROUGH SATURDAY...MODERATE CONFIDENCE. EXPECT VFR CONDITIONS.
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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/... TONIGHT... SOUTH-SOUTHWEST WINDS INCREASE AS A GREAT LAKES COLD FRONT APPROACHES. THE TIGHTENING PRESSURE GRADIENT SHOULD SUPPORT WINDS APPROACHING 25 KNOTS AT TIMES. THE WINDS WILL DRIVE HIGHER SEAS WITH 5 TO 8 FOOT VALUES ON THE EXPOSED WATERS BY LATE NIGHT. SMALL CRAFT ADVISORY IN EFFECT FOR ALL WATERS. WEDNESDAY... COLD FRONT CROSSES THE WATERS. THIS WILL SHIFT THE WIND OUT OF THE WEST. WINDS WILL CONTINUE TO GUST AT TIMES TO 25 KNOTS...AND SEAS WILL CONTINUE AT 5 TO 8 FEET ON THE EXPOSED WATERS. SMALL CRAFT ADVISORY CONTINUES BUT MAY BE DROPPED ON SOME NEAR SHORE WATERS. WEDNESDAY NIGHT...WINDS BECOME NORTHWEST AND PULL COLDER AIR ACROSS THE WATERS...GUSTING 20-25 KNOTS LATER AT NIGHT. SEAS WILL LINGER AROUND 5-6 FEET OVERNIGHT. OUTLOOK...THURSDAY THROUGH SATURDAY... THURSDAY... NW WINDS INCREASE DURING THU...GUSTING UP TO 25-30 KT BY LATE IN THE DAY. SEAS REMAIN AT 5-6 FT ON THE OUTER WATERS. VSBYS REDUCED IN AREAS OF FOG AND PATCHY FOG. THURSDAY NIGHT... EXPECT N-NW WINDS GUSTING TO 25-30 KT THROUGH AROUND MIDNIGHT... HIGHEST ACROSS THE EASTERN WATERS...THEN WILL DIMINISH. SEAS WILL REMAIN AOA 5 FT OVER THE OPEN WATERS. REDUCED VSBYS EARLY THU NIGHT MAINLY FROM E OF CAPE COD SOUTHWARD THROUGH AROUND MIDNIGHT THEN SHOULD IMPROVE. FRIDAY AND SATURDAY... NW GUSTS TO AROUND 25 KT CONTINUE ON THE OPEN WATERS THROUGH FRI NIGHT...THEN BACK TO SW BUT WILL STILL GUST UP TO 25-30 KT DURING SAT. SEAS REMAIN AOA 5 FT THROUGH LATE FRI...THEN BRIEFLY SUBSIDE BEFORE BUILDING AGAIN ON THE SW WINDS DURING SAT.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...WINTER WEATHER ADVISORY UNTIL 10 AM EST WEDNESDAY FOR CTZ002>004. MA...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING FOR MAZ020>024. WINTER WEATHER ADVISORY UNTIL 10 AM EST WEDNESDAY FOR MAZ002>022-026. RI...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING FOR RIZ003>008. WINTER WEATHER ADVISORY UNTIL 10 AM EST WEDNESDAY FOR RIZ001>007. MARINE...SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 4 AM EST WEDNESDAY FOR ANZ230>234-236. SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 7 PM EST WEDNESDAY FOR ANZ235-237-250-254>256. SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 1 PM EST WEDNESDAY FOR ANZ251.
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&& $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB/RLG SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/RLG/EVT MARINE...WTB/EVT

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