Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 212025 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 425 PM EDT MON APR 21 2014 .SYNOPSIS...
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HIGH PRESSURE REMAINS ALONG THE COAST FROM NOVA SCOTIA THROUGH THE MID ATLANTIC STATES. THE HIGH WILL MOVE OFFSHORE TONIGHT. LOW PRESSURE OVER THE GREAT LAKES WILL MOVE EAST TO NORTHERN NEW ENGLAND TUESDAY...AND SWING A COLD FRONT THROUGH THE REGION TUESDAY NIGHT. EXPECT BRISK AND COOLER CONDITIONS MOVING IN BEHIND THE FRONT LATE WEDNESDAY INTO THURSDAY. WINDS MAY BE ESPECIALLY GUSTY WEDNESDAY AFTERNOON INTO THE EVENING. THERE WILL BE THE CHANCE FOR ON AND OFF SCATTERED SHOWERS LATE FRIDAY INTO THE WEEKEND.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... THROUGH THIS EVENING... SUNSHINE THROUGH THIN CIRRUS. COULD ALSO BE SCATTERED MID CLOUDS IN NORTHERN MASS/SRN NH...SATELLITE AND OBS SHOW THESE OVER VT AND EASTERN NY MOVING THIS WAY. IT TOOK ITS TIME...BUT THE SEABREEZE DEVELOPED ALONG THE EASTERN COAST. MIXING EVENED OUT THE STRONG 1000-2000 FOOT WINDS AND WEAK WINDS ABOVE 3000 FEET. THIS ALLOWED WINDS TO QUICKLY SHIFT TO EAST/SOUTHEAST ALL AROUND BOSTON HARBOR AND THE SHORELINE NORTH AND SOUTH. ENOUGH OF A SOUTHWEST FLOW INLAND AND ALOFT TO LIMIT THE SEABREEZE TO THE IMMEDIATE EAST COAST...GENERALLY WITHIN A MILE OF THE SHORE. SIMILAR SITUATION AROUND NARRAGANSETT BAY WITH SOUTHEAST WINDS ACROSS WICKFORD WARWICK AND CRANSTON...AND SOUTH WINDS COMING OFF THE REST OF THE BAY. THE PREVAILING FLOW IS BRINGING ONSHORE FLOW TO MUCH OF THE SOUTH COAST. EXPECT THE SEABREEZE TO LINGER THRU 6 PM ALONG THE SHORELINE THEN DIMINISH. INLAND TEMPS ARE IN THE 60S AND SOME INLAND AREAS MAY TOP OUT NEAR 70. SEABREEZE AREAS WILL LINGER IN THE MID 50S TO NEAR 60. TONIGHT... HIGH PRESSURE MOVES OFFSHORE WITH THE GENERAL FLOW TURNING SOUTHWEST BUT REMAINING LIGHT. MID AND HIGH CLOUDS WILL MOVE EAST FROM THE GREAT LAKES...MOST WILL REACH OUR AREA AFTER 2 AM. LIGHT WINDS WILL ALLOW TEMPS TO COOL AGAIN...BUT THE SOUTHWEST FLOW SHOULD BRING AN INCREASE IN DEWPOINTS TO THE 30S AND LOWER 40S. LOW TEMPS WILL BE NEAR THIS...IN THE UPPER 30S AND 40S. TEMPS WILL BE NEAR DEWPOINT IN MANY AREAS...WHICH SHOULD ALLOW ANOTHER NIGHT OF FOG. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... GREAT LAKES LOW PRESSURE MOVES EAST TO NORTHERN NEW ENGLAND. INCREASING SOUTHWEST FLOW LEADING THE FRONT BRINGS INCREASING MOISTURE ALOFT...SO WE EXPECT MID AND HIGH CLOUDS TO INCREASE THROUGH THE DAY. BUT LOWER LEVELS REMAIN SUFFICIENTLY DRY TO KEEP SHOWER CHANCES LOW MOST OF THE DAY. MODEL QPF REMAINS TO OUR WEST THROUGH 18Z AND THEN MOVES INTO NORTHERN AND WESTERN AREAS MID TO LATE AFTERNOON. ALL MODELS SHOW PCPN FOR TUESDAY NIGHT. JET PLACEMENT IS FAVORABLE FOR UPPER VENTING LATE TUESDAY/TUESDAY NIGHT. UPPER TROUGH PLACEMENT OVER NY/PA ALSO LOOKS FAVORABLE. WE WILL FEATURE LIKELY POPS TUESDAY EVENING THROUGH MIDNIGHT WITH LINGERING CHANCE POPS OVERNIGHT. NAM/GFS/GGEM/ECMWF ADVERTISE TOTALS NEAR 50 TUESDAY NIGHT. GGEM AND ECMWF SHOW 850-500MB LAPSE RATES AROUND 6.5C/KM...THE GFS JUST BELOW. THIS WOULD SUGGEST FAVORABLE ELEVATED INSTABILITY FOR EMBEDDED TSTMS. WE WILL MENTION SLIGHT CHANCE FOR THIS WITH THE SHOWERS. MIXING PROFILES FAVOR MIXING TO 950 MB BUT THESE ARE FREQUENTLY AN UNDERESTIMATE. USING 925 MB TEMPS...MAX SFC TEMPS SHOULD REACH 65-70...COOLER NEAR THE SOUTH COAST. CLOUDS AND PCPN WILL KEEP A BLANKET OVER THE AIRMASS UNTIL LATE TUESDAY NIGHT WHEN COLDER VALUES ADVECT IN. WE FAVORED MINS IN THE 40S WITH COLDEST VALUES NORTHWEST. && .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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HIGHLIGHTS... * CHANCE FOR SHOWERS LINGERS INTO WEDNESDAY * BREEZY AND COOLER FOR WEDNESDAY AND THURSDAY * RISK FOR MORE SHOWERS LATE FRIDAY INTO SATURDAY NIGHT DETAILS... WED...SOME SHOWERS MAY LINGER THROUGH THE MORNING MAINLY IN EASTERN ZONES AS LOW PRESSURE IS SLOW TO MOVE EAST OF THE AREA AND UPPER TROF CLOSES OFF. CONTINUED LOW CHANCE POPS IN EASTERN ZONES...WITH SLIGHT CHANCE TO THE WEST. DRY CONDITIONS EXPECTED FOR THE AFTERNOON...BUT WITH H850 WINDS INCREASING TO 40-50 KTS AND COLD AIR ADVECTION ONGOING...SURFACE WINDS ARE EXPECTED TO BECOME STRONG AND GUSTY AS THE DAY PROGRESSES. NOT SURE IF WINDS WILL BE STRONG ENOUGH FOR WIND ADVISORY CRITERIA BUT SURFACE WIND GUSTS TO 30-40 MPH LOOK LIKELY AT THIS POINT WED AFTERNOON/EVENING. SOME DECOUPLING MAY OCCUR LATE WED NIGHT BUT THINK EXPOSED HIGHER TERRAIN AND COASTAL PLAIN MAY REMAIN GUSTY THROUGHOUT THE NIGHT. THU...WIND GUSTS 25 TO 30 MPH POSSIBLE IN THE MORNING...OTHERWISE MOSTLY CLEAR SKIES AND DIMINISHING WINDS EXPECTED AS HIGH PRESSURE WORKS ITS WAY EASTWARD TOWARD SOUTHERN NEW ENGLAND. HIGHS IN THE 50S MOST LOCATIONS. FRI...SHOULD BE MAINLY DRY AND WARMER WITH TEMPS REACHING 60 TO 65 ...EXCEPT WITH THE POTENTIAL FOR SEA BREEZES THAT MAY KEEP TEMPS IN THE 50S ALONG COASTAL AREAS. A CHANCE FOR SHOWERS EVOLVES IN THE AFTERNOON ACROSS THE WESTERN ZONES /MAINLY SLIGHT CHANCE/ AS A WARM FRONT APPROACHES THE AREA FROM THE WEST. RAIN CHANCES INCREASE DURING THE NIGHT. SAT...UPPER SHORT WAVE TROF AND SURFACE OCCLUDED OR COLD FRONT MAY CROSS THE AREA DURING THIS TIMEFRAME. MODELS DIFFER ON PLACEMENT AND INTENSITY OF THESE FEATURES. AT THIS TIME MORE CLOUDS THAN SUN IS EXPECTED...WITH THE CHANCE FOR SHOWERS. THIS IS A CONSENSUS OF THE MODEL GUIDANCE FOR SATURDAY. SUN AND MON...THERE IS CONSIDERABLE UNCERTAINTY FOR THIS TIMEFRAME AT THE END OF THE EXTENDED. GFS INDICATES A CUT OFF UPPER LOW DRIFTING TO THE VICINITY OF NOVA SCOTIA SUNDAY INTO MONDAY. THIS WOULD PROMPT PERIODS OF CLOUDINESS AND THE CHANCE FOR SHOWERS IN SOUTHERN NEW ENGLAND SUNDAY. HOWEVER ECMWF IS MORE PROGRESSIVE... PUSHING THE UPPER LOW FURTHER NORTH AND EAST DURING SUN/MON...AND BRINGING DRY CONDITIONS TO OUR AREA FOR THE SAME TIMEFRAME. AT THIS TIME HAVE CONTINUED A CHANCE/SLIGHT CHANCE POP FOR RAIN SHOWERS ON SUNDAY. AT THIS TIME THE OVERALL GUIDANCE CONSENSUS FOR MONDAY IS FOR MAINLY DRY CONDITIONS.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/...
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LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY NIGHT/...HIGH CONFIDENCE. THROUGH 00Z...VFR WITH SOME THIN HIGH-LEVEL CIRRUS. ESTABLISHED SEA BREEZES ALONG THE COASTLINES WILL LINGER THROUGH 22Z BUT THEN BREAK DOWN DURING THE EVENING. TONIGHT...VFR. LIGHT S-SW WINDS. SOME HIGH CLOUDS MOVE IN AFTER MIDNIGHT. AREAS OF FOG WILL DEVELOP WITH THE BEST CHANCE IN RI AND SOUTHEAST MASS. VSBYS IN ANY FOG WILL BE 3-5 MILES EXCEPT 1 MILE OR LESS ON PARTS OF THE SOUTH COAST. TUESDAY...VFR. CLOUDS WILL INCREASE AND THICKEN...ESPECIALLY DURING THE AFTERNOON. TUESDAY NIGHT...MVFR CIGS/VSBYS IN SHOWERS. SCATTERED IFR POSSIBLE. WIDELY SCATTERED THUNDER EMBEDDED IN THE SHOWERS. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. SEA BREEZE DIMINISHING AROUND 22-24Z. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...WEDNESDAY INTO SATURDAY... WED MORNING...MODERATE CONFIDENCE. MVFR CIGS AND VSBYS IN SHOWERS WITH SCATTERED AREAS OF IFR CIGS/VSBYS POSSIBLE. WED AFTERNOON...MODERATE TO HIGH CONFIDENCE. VFR WEST AND BECOMING VFR EAST. GUSTY SFC WINDS...POSSIBLY TO 30 KT. THU...HIGH CONFIDENCE OF VFR. MODERATE CHANCE OF GUSTS 25 TO 30 KT DURING THURSDAY MORNING...DIMINISHING THU AFTERNOON. FRI...HIGH CONFIDENCE VFR FOR MOST OF THE DAY. LOW CHANCE OF MVFR CIGS/VSBYS IN SCATTERED SHOWERS IN THE AFTERNOON. SAT...MODERATE CONFIDENCE. POTENTIAL FOR MVFR CIGS/VSBYS IN SCATTERED 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 TUESDAY NIGHT/...HIGH CONFIDENCE. TONIGHT...DIMINISHING WINDS AND SEAS WITH VALUES REMAINING BELOW SMALL CRAFT THRESHOLDS. TUESDAY...SOUTH-SOUTHWEST WINDS BUILD TO AROUND 15 KNOTS...POSSIBLY A LITTLE HIGHER. SEAS ALSO BUILD DURING THE AFTERNOON AND MAY REACH 5 FEET ON PARTS OF THE OUTER WATERS TOWARD LATE AFTERNOON/EVENING. TUESDAY NIGHT...COLD FRONT CROSSES THE WATERS. VSBYS WILL LOWER IN SHOWERS...REACHING 1-3 MILES AT TIMES. WIDELY SCATTERED THUNDER ALSO POSSIBLE. WINDS REMAIN BELOW 20 KNOTS. PARTS OF THE SOUTHERN AND EASTERN OUTER WATERS MAY REACH 5 FEET BUT MOST AREAS WILL REMAIN BELOW. OUTLOOK...WEDNESDAY INTO SATURDAY... MODERATE CONFIDENCE. WED INTO THU...CONTINUE THINKING THAT NW WINDS LIKELY INCREASE WELL INTO SCA CRITERIA ALL COASTAL WATERS DURING WED. WIND GUSTS MAY APPROACH GALE FORCE LATE WED AFTERNOON. THERE IS A RISK OF GALE FORCE GUSTS ESPECIALLY ON THE OUTER COASTAL WATERS WEDNESDAY NIGHT INTO THURSDAY...WITH FREQUENT GUSTS TO 35 KT POSSIBLE...AND SEAS BUILDING TO 7 TO 10 FEET ON THE OUTER COASTAL WATERS. WINDS BEGIN TO DIMINISH THURSDAY AFTERNOON...AND FOR THU NIGHT SCA CRITERIA WINDS/SEAS SHOULD LINGER ON THE OUTER COASTAL WATERS. FRI...WINDS AND SEAS EXPECTED TO BE BELOW SCA CRITERIA. SAT...THERE IS A CHANCE FOR SEAS AND SW WINDS TO INCREASE TO SCA CONDITIONS.
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&& .HYDROLOGY... MINOR FLOODING CONTINUES ALONG PORTIONS OF THE MAINSTEM CT RIVER. SEE THE LATEST FLOOD STATEMENT FOR DETAILS. FLOOD WARNINGS REMAIN POSTED ALONG CT RIVER AT MIDDLE HADDAM. CT RIVER AT HARTFORD HAS RECEDED BELOW FLOOD STAGE AND IS EXPECTED TO REMAIN BELOW FLOOD. THE WARNING AT HARTFORD HAS BEEN CANCELLED. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/NMB NEAR TERM...WTB SHORT TERM...WTB LONG TERM...NMB AVIATION...WTB/NMB MARINE...WTB/NMB HYDROLOGY...STAFF

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