Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 221051 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 651 AM EDT TUE APR 22 2014 .SYNOPSIS... A PERIOD OF SHOWERS AND POSSIBLY A THUNDERSTORM ARRIVES LATER TODAY AND TONIGHT AS LOW PRESSURE TRACKS FROM THE GREAT LAKES TO NORTHERN NEW ENGLAND AND SWINGS A COLD FRONT THROUGH THE REGION. WINDY AND COOLER WEATHER WILL FOLLOW WEDNESDAY AND THURSDAY. UNSETTLED WEATHER IS LIKELY FOR THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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7 AM UPDATE...MADE SOME MINOR UPDATES TO THE TEMPERATURE AND DEWPOINT GRIDS TO ACCOUNT FOR THE LATEST TRENDS. OTHERWISE... FORECAST IS ON TRACK. 340 AM UPDATE... PLENTY OF MID AND HIGH CLOUDINESS OVER REGION EARLY THIS MORNING. THIS HAS PREVENTED MUCH IN WAY OF FOG/LOW CLOUD FORMATION WHICH SHOULD BE RULE THROUGH DAYBREAK. COLD FRONT APPROACHES NEW ENGLAND TODAY WITH S/SW FLOW IN PLACE AHEAD OF IT. MODELS SIMILAR ON TIMING...BRINGING A FEW SHOWERS INTO WESTERN NEW ENGLAND LATE THIS AFTERNOON. LEANED ON 21Z/21 SREF FOR TIMING WHICH MATCHES WELL WITH 00Z NAM/GFS COMPROMISE. WARM ADVECTION AHEAD OF FRONT WILL LEAD TO ANOTHER MILD DAY WITH HIGHS IN 60S/LOWER 70S...WARMEST IN MERRIMACK AND CT VALLEYS. ONSHORE FLOW WILL KEEP HIGHS IN 50S/LOWER 60S ALONG S COAST. USED BLEND OF GFS/NAM MOS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
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SOUTHERLY FLOW AHEAD OF FRONT SHOULD LEAD TO AREAS OF LOW CLOUDS AND FOG THIS EVENING ALONG S COAST...CAPE COD AND ISLANDS. MOST OF SHOWERS OCCUR TONIGHT AS COLD FRONT MOVES THROUGH. FAIRLY IMPRESSIVE INSTABILITY ALOFT WITH TOTAL TOTALS RISING INTO LOWER 50S AND DECENT MID LEVEL LAPSE RATES...ENOUGH TO INCLUDE MENTION OF THUNDER ACROSS MUCH OF REGION. RAINFALL TOTALS SHOULD AVERAGE 0.25 TO PERHAPS 0.50 INCHES...HIGHEST ACROSS INTERIOR. STAYED CLOSE TO GFS/NAM MOS BLEND WITH LOWS HOLDING IN 40S. FAIRLY IMPRESSIVE SYSTEM FOR LATE APRIL AS UPPER LOW CLOSES OFF OVER SOUTHERN NEW ENGLAND WEDNESDAY MORNING...RESULTING IN WINTRY-LOOKING WRAP AROUND PATTERN ON NW SIDE OF DEPARTING SURFACE LOW. 00Z NAM TAKES SYSTEM MUCH FARTHER S THAN 00Z GFS/ECMWF AND APPEARS TO BE AN OUTLIER. PREFER MORE NORTHERN TRACK WHICH FOCUSES RAINFALL ON E MA/S NH WED MORNING AS OPPOSED TO S COASTAL AREAS BEFORE CLEARING SETS IN DURING AFTERNOON WITH DEPARTURE OF UPPER TROUGH. SHOULD BECOME WINDY WED AFTERNOON AS SOUNDINGS INDICATE DEEPENING MIXED LAYER AND TIGHTENING GRADIENT...ESPECIALLY LATER IN DAY. LEANED MORE TOWARD GFS MOS GIVEN ITS BETTER HANDLING OF SYSTEM. HIGHS SHOULD TOP OUT IN 50S TO NEAR 60.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... * WINDY...COOLER CONDITIONS EXPECTED WED NIGHT AND THU * UNSETTLED BUT SEASONABLE WEATHER THIS WEEKEND 22/00Z MODELS ARE IN BETTER THAN NORMAL AGREEMENT THROUGH THE LONG TERM PERIOD OF THE FORECAST. WINDY CONDITIONS WILL LEAD OFF THE PERIOD AS THE PRESSURE GRADIENT INCREASES WITH LOW PRESSURE PULLING AWAY FROM SOUTHERN NEW ENGLAND AND HIGH PRESSURE APPROACHING. WEAK HIGH PRESSURE MOVES OVER SOUTHERN NEW ENGLAND THURSDAY AND OFFSHORE FRIDAY. THIS WEEKEND...MODELS HINT AT A MORE BLOCKED PATTERN DEVELOPING WITH RIDGING OVER THE CENTRAL CONUS AND TROUGHING LINGERING OVER THE NE. THIS LEADS TO A LOT OF UNCERTAINTY FOR OUR WEATHER THIS WEEKEND INTO EARLY NEXT WEEK. AT THIS POINT...LOOKS LIKE WHILE TEMPERATURES WILL BE SEASONABLE...THERE COULD BE SOME RAIN SHOWERS WITH A COLD FRONT ON SATURDAY. THEN POTENTIALLY DRIER WEATHER LEADING INTO NEXT WEEK. HOWEVER...IF THIS BLOCKING PATTERN DEVELOPS...THIS COULD CHANGE. WEDNESDAY NIGHT AND THURSDAY...LOW PRESSURE EAST OF NANTUCKET WILL CONTINUE TO MOVE EAST INTO THE MARITIMES WHILE A WEAK AREA OF HIGH PRESSURE BUILDS INTO SOUTHERN NEW ENGLAND AND LOW PRESSURE MOVES INTO THE GREAT LAKES. THIS WILL RESULT IN A FAIRLY TIGHT PRESSURE GRADIENT OVER THE REGION PARTICULARLY WEDNESDAY NIGHT. IN ADDITION...A STRONG LOW LEVEL JET DEVELOPS AND COUPLED WITH STEEP LAPSE RATES...WILL RESULT IN GUSTY WINDS THROUGHOUT WEDNESDAY NIGHT AND THURSDAY. AT THIS POINT...BELIEVE WINDS WILL REMAIN BELOW WIND ADVISORY CRITERIA. HOWEVER...THEY ARE CLOSE SO WILL KEEP AN EYE ON IT IN THE NEXT DAY OR SO. FRIDAY AND SATURDAY...FRIDAY WILL BE SOMEWHAT OF A TRANSITION DAY BETWEEN THE WIND ON THURSDAY AND A COLD FRONT SATURDAY. TEMPERATURES RETURN TO SEASONABLE NORMS. LOW PRESSURE MOVES THROUGH QUEBEC INTO THE MARITIMES ON SATURDAY BRINGING A COLD FRONT THROUGH SOUTHERN NEW ENGLAND LATE SATURDAY. SCATTERED SHOWERS ARE POSSIBLE AHEAD OF THE FRONT. SUNDAY INTO EARLY NEXT WEEK...AS STATED ABOVE A MORE BLOCKED PATTERN LOOKS TO DEVELOP WITH MID LEVEL TROUGHING OVER THE NE BRINGING UNSETTLED WEATHER TO THE REGION. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH WEDNESDAY/...HIGH CONFIDENCE. VFR CIGS AOA 120 TODAY WITH S/SW WINDS AND NO EAST COAST SEA BREEZE. SHOWERS AHEAD OF COLD FRONT REACH WESTERN NEW ENGLAND LATE THIS AFTERNOON/EVENING WITH MVFR/IFR CIGS/VSBYS BUT PROBABLY NOT UNTIL AFTER 00Z WED ALONG E MA COAST. LIFR EXPECTED AROUND CAPE COD AND ISLANDS...PRIMARILY DUE TO FOG. ISOLATED THUNDER POSSIBLE TONIGHT BUT PROBABILITY TOO LOW FOR INCLUDING IN TAFS. MVFR/IFR CIGS WED MORNING WITH SCT SHOWERS...MAINLY IN EASTERN MA WITH VFR CIGS ELSEWHERE. INCREASING N/NW WINDS WED AFTERNOON WITH GUSTS AS HIGH AS 25-30KT. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. NO SEA BREEZE EXPECTED TODAY. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY... WEDNESDAY NIGHT THROUGH THURSDAY...MODERATE CONFIDENCE. VFR. STRONG AND GUSTY NW WINDS. GUSTS LIKELY REMAIN BELOW 30 KTS MOST AREAS. LOW PROBABILITY OF GUSTS TO 35 KTS ALONG THE COASTS. FRIDAY...HIGH CONFIDENCE. VFR. SATURDAY...MODERATE CONFIDENCE. MAINLY VFR. BRIEF PERIODS OF MVFR IN SCT -SHRA.
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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 /THROUGH WEDNESDAY/...HIGH CONFIDENCE. INCREASING S/SW WINDS TODAY AHEAD OF COLD FRONT BUT GUSTS SHOULD STAY BELOW 25KT. SEAS GRADUALLY BUILD HOWEVER AND SHOULD REACH 5 FT ON WATERS NEAR MERRIMACK RIVER...WHERE WE WILL HAVE SMALL CRAFT ADVISORIES POSTED BEGINNING THIS AFTERNOON. S FLOW SHOULD RESULT IN AREAS OF DENSE FOG/LOW CLOUDS ON S COASTAL WATERS THIS EVENING. COLD FRONT CROSSES WATERS TONIGHT SHIFTING WINDS TO N/NW LATE...AND ACCOMPANIED BY SHOWERS AND POSSIBLY A THUNDERSTORM. FRONT HEADS OFFSHORE WED WITH INCREASING N/NW WINDS WED AFTERNOON. FAIRLY CONFIDENT IN GALE FORCE GUSTS LATE IN DAY NEAR SHORE... INCLUDING BOSTON HARBOR AND NARRAGANSETT BAY BEFORE WINDS POSSIBLY SUBSIDE WED EVENING FOR A TIME. OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY... WEDNESDAY NIGHT AND THURSDAY...MODERATE TO HIGH CONFIDENCE. SEAS RANGE BETWEEN 5 AND 10 FEET ON THE OUTER WATERS WITH SEAS PEAKING DURING THE DAY THURSDAY. NORTHWESTERLY GALES ARE LIKELY AS OCEAN STORM PULLS EAST INTO THE MARITIMES. A GALE WATCH HAS BEEN ISSUED FOR THIS PERIOD. WINDS AND SEAS DIMINISH THURSDAY NIGHT. FRIDAY...MODERATE CONFIDENCE. QUIET BOATING WEATHER. SATURDAY...LOW TO MODERATE CONFIDENCE. SW WINDS AND SEAS INCREASE AS A COLD FRONT APPROACHES THE WATERS. VISIBILITIES MAY BE REDUCED AT TIMES IN RAIN SHOWERS. && .HYDROLOGY... MINOR FLOODING HAS ENDED ALONG LOWEST REACHES OF CT RIVER NEAR MIDDLE HADDAM. FLOOD WARNING HAS BEEN DISCONTINUED. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...GALE WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY EVENING FOR ANZ230>237-250-251-254>256. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM NOON TODAY TO MIDNIGHT EDT TONIGHT FOR ANZ250-254. && $$ SYNOPSIS...RLG/JWD NEAR TERM...RLG/JWD SHORT TERM...JWD LONG TERM...NMB AVIATION...RLG/JWD MARINE...WTB/RLG/JWD HYDROLOGY...

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