Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 181956 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 356 PM EDT FRI APR 18 2014 .SYNOPSIS...
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A WEAKENING COLD FRONT WILL MOVE ACROSS SOUTHERN NEW ENGLAND LATER TONIGHT. HIGH PRESSURE WILL THEN BUILD OVER THE REGION BRINGING DRY WEATHER SATURDAY THROUGH MONDAY. LOW PRESSURE WILL LIKELY BRING A PERIOD OF WET WEATHER TO THE REGION SOMETIME LATE TUESDAY INTO WEDNESDAY.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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THROUGH 00Z/8 PM... MARINE CLOUDS LINGERING ACROSS EASTERN MASS AS EAST WINDS CONTINUE TO MOVE ASHORE FROM MASS BAY AND THE GULF OF MAINE. THE CLOUDS HAVE BROKEN UP FARTHER WEST WHERE WINDS HAVE BECOME VARIABLE OR SOUTH...CUTING OFF THE INFLOW OF MOISTURE FOR THE CLOUDS. EXPECT THE CLOUDS TO SLOWLY DIMINISH THROUGH THE EVENING. TONIGHT... SURFACE COLD FRONT OVER THE GREAT LAKES WILL CROSS NEW ENGLAND OVERNIGHT. EXTRAPOLATION BRINGS THE FRONT TO THE CT VALLEY AROUND 09Z-11Z. JET DYNAMICS ARE FOCUSSED TOWARD THE CANADIAN BORDER/NRN VT/NRN NH. TIME CROSS SECTIONS OVER SRN NEW ENGLAND SHOW MOST OF THE FAVORABLE RH AT OR ABOVE 500 MB...BEST RH VALUES OF 60-70 PCT FOR A BRIEF PERIOD AROUND 06Z-09Z. IF THERE ARE ANY SHOWERS IN OUR AREA...WOULD EXPECT THEM TO BE IN SRN NH OR IN EXTREME NRN MASS. WE HAVE ADDED SLIGHT CHANCE POPS TO SRN NH AND EXTREME NORTHERN ESSEX CO BUT VALUES ARE LOW...ROUGHLY 15-18 PCT. TEMPS WILL COOL SOMEWHAT TONIGHT FROM A STARTING POINT IN THE 40S...BUT CLOUDS WILL SLOW ANY COOLING TREND. WE STAYED CLOSE TO A MODEL CONSENSUS WHICH HAS MINS MAINLY IN THE 30S. A FEW OF THE COLDER SPOTS IN FRANKLIN AND CHESHIRE COUNTIES COULD REACH THE UPPER 20S.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
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SATURDAY... THE COLD FRONT MOVES OFFSHORE SATURDAY MORNING. THE TRAILING UPPER TROUGH CROSSES NEW ENGLAND BETWEEN 12Z AND 18Z. THERE IS SOME CONCERN FOR ADDITIONAL CLOUDS POPPING AS THE COLDEST AIR MOVES OVERHEAD. BUT THE FORECAST MOISTURE CONTENT OF THE AIRMASS DIMINISHES...SO WE WILL FOLLOW MODEL TRENDS AND GO WITH CLEARING SKIES. THE SOLAR HEATING AND COOLING TEMPS ALOFT WILL ALLOW FOR DEEP MIXING OF THE AIRMASS WITH THE MIXED LAYER REACHING TO AT LEAST 900 MB AND PROBABLY TO 850 MB. WINDS IN THIS LAYER TOMORROW WILL REACH AT LEAST 25 KNOTS...AND THERE ARE SOME MODEL INDICATIONS OF 30 KNOTS. THIS WOULD MEAN GUSTS OF 30-35 MPH MIXING TO THE SURFACE TOWARD MIDDAY AND THE AFTERNOON. TEMPS AT 850 MB WILL BE 0C TO -2C...THE NAM SUGGESTS -4C. WITH FULL MIXING THIS WOULD SUPPORT MAX TEMPS IN THE MID 50S TO AROUND 60. THE BUILDING SURFACE PRESSURES SHOULD BE HIGH ENOUGH TO ADD ANOTHER 1-2F TO THESE EXPECTATIONS. WE WILL FORECAST MID 50S TO LOWER 60S. SATURDAY NIGHT... HIGH PRESSURE IN QUEBEC BUILDS OVER NEW ENGLAND. EXPECT CLEAR SKIES AND LIGHT WINDS WITH DEWPOINTS IN THE 20S AND LOWER 30S. RADIATIONAL COOLING SHOULD ALLOW MIN TEMPS IN THE UPPER 20S AND 30S.
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&& .LONG TERM /SUNDAY THROUGH THURSDAY/...
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HIGHLIGHTS... * DRY SUNDAY AND MONDAY WITH CHILLY NIGHTS/MILD DAYS * WET WEATHER LIKELY SOMETIME LATE TUESDAY INTO WEDNESDAY DETAILS... SUNDAY... HIGH PRESSURE OVERHEAD WILL RESULT IN DRY WEATHER WITH A MILD SUNDAY AFTERNOON. PLENTY OF SUNSHINE WILL ALLOW FOR HIGHS TO REACH INTO THE UPPER 50S AND LOWER 60S JUST INLAND FROM THE COAST. HOWEVER...WEAK PRESSURE GRADIENT WILL ALLOW FOR SEA BREEZES ON THE IMMEDIATE COAST PROBABLY HOLDING HIGHS IN THE UPPER 40S TO LOWER 50S. SUNDAY NIGHT... HIGH PRESSURE WILL REMAIN ANCHORED OVER THE REGION ALLOWING FOR ANOTHER GOOD NIGHT OF RADIATIONAL COOLING. LOW TEMPS WILL BE MAINLY IN THE 30S. MONDAY... HIGH PRESSURE WILL STILL BE IN CONTROL OF OUR WEATHER WITH A MIXTURE OF SUN AND CLOUDS. 850 MB TEMPS MODERATE CONSIDERABLY FROM SUNDAY/S VALUES REACHING BETWEEN +6C TO +8C. THIS SHOULD ALLOW HIGH TEMPS TO REACH WELL INTO THE 60S ACROSS MUCH OF THE REGION...TO PERHAPS EVEN NEAR 70 IN A FEW LOCALES. ALONG THE IMMEDIATE COAST INCLUDING BOSTON...ITS UNCERTAIN IF SEA BREEZES WILL DEVELOP IN THIS TIME RANGE. IF SEA BREEZES ARE ABLE TO DEVELOP...IT WOULD PROBABLY KEEP HIGH TEMPS IN THE 50S...BUT THEY MAY END UP VERY LOCALIZED JUST AFFECTING AREAS WITHIN A FEW MILES OF THE COAST. TUESDAY AND WEDNESDAY... A POTENTIALLY STRONG UPPER LEVEL SHORTWAVE WILL DIVE SOUTHEASTWARD FROM CANADA. THIS WILL SPAWN A SURFACE LOW PRESSURE SYSTEM APPROACHING OUR REGION FROM THE WEST. AT THIS TIME RANGE...THERE IS LOW CONFIDENCE ON STRENGTH/TIMING OF SHORTWAVE AND TRACK/INTENSITY OF SURFACE LOW PRESSURE. IT DOES LOOK LIKE A DECENT SHOT FOR AT LEAST PERIOD OF WET WEATHER SOMETIME LATE TUESDAY INTO WEDNESDAY. THURSDAY... DRY WEATHER SHOULD FOLLOW BEHIND THE DEPARTING LOW PRESSURE SYSTEM. SOME INDICATIONS ARE THAT IT MAY BE WINDY BEHIND THE SYSTEM WITH NEAR OR BELOW NORMAL TEMPERATURES.
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&& .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
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LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. MODERATE CONFIDENCE TONIGHT...HIGHER CONFIDENCE SATURDAY AND SATURDAY NIGHT... THROUGH 00Z...BROAD AREA OF 2500 FOOT CIGS SPREAD ACROSS MOST OF SOUTHERN NEW ENGLAND DURING THE MORNING. BUT BY AFTERNOON IT HAD BROKEN INTO TWO SMALLER AREAS...ONE ALONG THE COASTAL PLAIN AND THE OTHER OVER THE CENTRAL HILLS /CENTRAL MASS AND S CENTRAL NH/. LARGE AREA OF CIRRUS OVERLAYS THESE LOWER CLOUDS. EXPECT THE COASTAL PLAIN LOWER CLOUDS TO LINGER THROUGH THE EVENING...FED BY MOIST AIR OFF MASS BAY. TONIGHT...HIGH CONFIDENCE IN TREND...MODERATE CONFIDENCE IN TIMING. EXPECT WINDS TO SHIFT AS A COLD FRONT FROM THE GREAT LAKES APPROACHES. THIS WILL START MOVING THE LOWER CLOUDS OUT OF THE AREA WHILE VFR CLOUDS ASSOCIATED WITH THE FRONT MOVE IN. MOVEMENT OF THE FRONT WOULD BRING IT THROUGH OUR AREA BETWEEN 06Z AND 12Z. CONDITIONS SHOULD REMAIN VFR THROUGH THE NIGHT WITH WINDS SHIFTING TO NORTHWEST LATE. SATURDAY AND SATURDAY NIGHT... DRIER AIR MOVES IN. EXPECT CLEARING SKIES AND VFR. DAYTIME HEATING BY THE SUN WILL DRAW STRONGER WINDS GUSTS TO THE SURFACE WITH GUSTS TO AT LEAST 25 KNOTS...POSSIBLY 30 KNOTS. THESE WINDS WILL DIMINISH AROUND SUNSET. CONTINUED VFR WITH DIMINISHING NORTH WIND SATURDAY NIGHT. KBOS TERMINAL...MODERATE CONFIDENCE. MAIN ISSUE IS EXTENT AND DURATION OF MVFR CIGS THROUGH EARLY TONIGHT. KBDL TERMINAL...HIGH CONFIDENCE. SUNDAY THROUGH TUESDAY...HIGH CONFIDENCE IN VFR CONDITIONS. TUESDAY...LOW TO MODERATE CONFIDENCE. VFR CONDITIONS MAY DETERIORATE TO MVFR-IFR THRESHOLDS LATE TUE OR TUE NIGHT IN RAIN 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 SATURDAY NIGHT/...HIGH CONFIDENCE. WINDS MOST OF THE TIME WILL REMAIN BELOW 25 KNOTS. IT IS POSSIBLE ON SATURDAY THAT GUSTS CLOSE TO SHORE MAY BE NEAR 25 KNOTS. WINDS WILL SHIFT TO NORTHWEST ON SATURDAY AND NORTH SATURDAY NIGHT. A LINGERING SWELL WILL KEEP SEAS 5 TO 7 FEET THROUGH SATURDAY...AND 5 FOOT SEAS MAY LINGER ON THE OUTER WATERS SATURDAY NIGHT. WILL CONTINUE SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS ON THE OUTER WATERS AND ON MASSACHUSETTS BAY/IPSWICH BAY. OUTLOOK...SUNDAY THROUGH TUESDAY... SATURDAY NIGHT AND SUNDAY...MODERATE TO HIGH CONFIDENCE. HIGH PRESSURE OVER NORTHERN NEW ENGLAND AND LOW PRESSURE WELL TO THE SOUTH OF THE WATERS WILL RESULT IN NORTH TO NORTHEAST WINDS. WIND GUSTS OF 20 TO 25 KNOTS ALONG WITH 3 TO 5 FOOT SEAS ARE POSSIBLE ACROSS THE OUTER-WATERS. THIS MAY RESULT IN MARGINAL SCA CONDITIONS. MONDAY AND TUESDAY...MODERATE TO HIGH CONFIDENCE. WEAK PRESSURE GRADIENT SHOULD KEEP WINDS/SEAS GENERALLY BELOW SCA THRESHOLDS. WE MAY SEE MARGINAL SCA SEAS DEVELOP LATE TUE/TUE NIGHT AS A RESULT OF SOUTHEAST SWELL FROM LOW PRESSURE WELL EAST OF THE WATERS.
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&& .FIRE WEATHER...
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WEATHER CONDITIONS DRY OUT DURING THE DAY SATURDAY WITH DEWPOINTS IN THE 20S AND MINIMUM RH VALUES REACHING 28-35 PERCENT. NORTHWEST WINDS ARE ALSO EXPECTED TO PICK UP WITH GUSTS OF AT LEAST 25 KNOTS AND POSSIBLY 30 KNOTS. WEATHER CONDITIONS ARE SUFFICIENT TO CREATE AN ELEVATED FIRE WEATHER CONCERN...BUT REPORTS RECEIVED SO FAR INDICATE GROUND CONDITIONS ARE STILL TOO MOIST. NO FIRE WEATHER HEADLINES WILL BE ISSUED AT THIS TIME...BUT THE SITUATION WILL BE MONITORED.
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&& .HYDROLOGY... MINOR FLOODING CONTINUES ALONG PORTIONS OF THE MAIN STEM CT RIVER. MOST POINTS HAVE CRESTED AND ARE NOW RECEDING...MIDDLE HADDAM WILL CREST TONIGHT. SEE THE LATEST FLOOD STATEMENT FOR DETAILS. FLOOD WARNINGS REMAIN POSTED ALONG CT RIVER AT... NORTHAMPTON THOMPSONVILLE HARTFORD MIDDLE HADDAM && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 PM EDT THIS AFTERNOON FOR ANZ235-237. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 AM EDT SATURDAY FOR ANZ250-251-254>256.
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&& $$ SYNOPSIS...WTB/FRANK NEAR TERM...WTB SHORT TERM...WTB LONG TERM...FRANK AVIATION...WTB/FRANK MARINE...WTB/FRANK FIRE WEATHER... HYDROLOGY...

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