Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 211911 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 311 PM EDT MON APR 21 2014 .SYNOPSIS... 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 ANOTHER CHANCE FOR SHOWERS ON SATURDAY. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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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.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
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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.
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/... HIGHLIGHTS... * SHOWERS LIKELY TUESDAY NIGHT...POSSIBLY LINGERING INTO WEDNESDAY MORNING * BREEZY AND COOLER FOR WEDNESDAY AND THURSDAY * RISK FOR MORE SHOWERS FRIDAY NIGHT INTO SATURDAY OVERVIEW... PROPENSITY FOR CLOSED 500 MB LOWS TO FORM...WHICH FITS THE CLIMATOLOGICAL PATTERN FOR SPRING. FOR THE MOST PART MEDIUM RANGE MODELS KEEP SYSTEMS FAIRLY PROGRESSIVE FOR NOW. NAO INDEX IS PROJECTED TO GO NEGATIVE...HOWEVER...AND SO WILL NEED TO WATCH THE POTENTIAL FOR SLOWER AND HIGHER AMPLITUDE SYSTEMS WITH TIME. LOOKS LIKE THREE PRIMARY TROUGHS TO MONITOR OVER THE NEXT 7 TO 10 DAYS WITH THE THIRD ONE LIKELY NOT AN ISSUE UNTIL BEYOND THIS CURRENT 7 DAY PERIOD. MEDIUM RANGE MODELS HAVE ROUGHLY SIMILAR THEME BUT BEGIN TO DIVERGE MORE SIGNIFICANTLY IN THE DETAILS OF THE SECOND TROUGH DURING THE COURSE OF THE COMING WEEKEND INTO NEXT WEEK. AS ONE MIGHT EXPECT...BOTH THE ECMWF AND GFS SHOW SIGNIFICANTLY GREATER SPREAD IN INDIVIDUAL MEMBERS STARTING WITH THIS COMING WEEKEND. HENCE...A MODEL CONSENSUS APPROACH WOULD APPEAR TO MAKE SENSE AT THIS TIME RANGE. DETAILS... WED...SOME RAIN MAY LINGER THROUGH THE MORNING IN THE EAST GIVEN PROPENSITY FOR UPPER TROF CLOSING OFF AND SURFACE LOW FORMING JUST EAST OR NORTHAST OF FORECAST AREA. THE 00Z ECMWF SEEMS A BIT BULLISH ON THIS IDEA AND HENCE HELD BACK LOW CHANCE POPS IN EAST FOR A WHILE ON WED. AFTERNOON DRIES OUT BUT THEN THE ISSUE BECOMES GUSTY WINDS. FAIRLY STRONG NORTHWEST FLOW WED AFTERNOON INTO WED NIGHT WITH COLD ADVECTION AND 925 MB WIND SPEEDS PROGGED AROUND 40 KT. NOT SURE IF WINDS WILL BE STRONG ENOUGH FOR WIND ADVISORY CRITERIA BUT GUSTS TO AT LEAST NEAR 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...LOOKS DRY. A LITTLE GUSTY THROUGH EARLY AFTERNOON...THEN WINDS SHOULD GRADUALLY DIMINISH. TEMPERATURES LOOK TO BE FAIRLY SEASONABLE TO PERHAPS A LITTLE BELOW THE SEASONAL NORM HIGHER ELEVATION AREAS. FAIRLY CHILLY AIR MASS THU...BUT APRIL SUNSHINE AND DOWNSLOPING WIND WILL HELP COMPENSATE. FRI...SHOULD BE DRY WITH SEA BREEZES POSSIBLE ALONG COASTAL AREAS. SAT...UPPER SHORT WAVE TROF AND SURFACE OCCLUDED OR COLD FRONT MAY CROSS AREA. THE LATEST ECMWF RUN KEEPS THE ENERGY FURTHER NORTH WHEREAS THE 00Z GFS RUN IS MORE ROBUST WITH SIGNS OF A TRIPLE POINT LOW PASSING ACROSS SOUTHERN NEW ENGLAND AND FAIRLY HIGH AMPLITUDE TROF CROSSING NEW ENGLAND. CONFIDENCE ON JUST HOW THIS WILL PLAY OUT IS RELATIVELY LOW THIS FAR OUT GIVEN ONLY FAIR RUN TO RUN CONSISTENCY AND DIFFERENCES IN THE VARIOUS ENSEMBLE MEMBERS. HENCE HAVE GONE WITH A CONSENSUS APPROACH TO THE GUIDANCE WHICH YIELDS A CHANCE OF SHOWERS FOR SAT. SUN...DRY OUT THE FORECAST AREA FOR NOW GIVEN MODEL CONSENSUS OF MOVING SYSTEM OUT. HOWEVER...CONFIDENCE IS NOT ALL THAT HIGH. IF UPPER LOW CLOSES OFF JUST A LITTLE FURTHER WEST AND SOUTH...THEN MIGHT SEE SOME RAIN HOLDING BACK INTO THE FORECAST AREA FOR AT LEAST SOME OF THE DAY. && .AVIATION /19Z MONDAY THROUGH SATURDAY/... 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 FRIDAY... WED MORNING...MODERATE CONFIDENCE. LINGERING MVFR CIGS/VSBYS AS SHOWERS MOVE OFF TO THE EAST. WED AFTERNOON...MODERATE TO HIGH CONFIDENCE. VFR WEST AND BECOMING VFR EAST. GUSTY SFC WINDS...POSSIBLY TO 30 KT. THU THRU FRI...HIGH CONFIDENCE OF VFR. && .MARINE... 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 FRIDAY... MODERATE CONFIDENCE. WED...INCREASING NW WIND TO AT LEAST SCA CRITERIA LIKELY ALL WATERS DURING WED AFTERNOON...AND WIND MAY APPROACH GALE FORCE LATE WED AFTERNOON AND WED NIGHT WITH FREQUENT GUSTS TO 35 KT POSSIBLE. THU...LINGERING GUSTY NW WINDS MAY REQUIRE CONTINUATION OF SCA FOR AT LEAST SOME OF DAY. SEAS SUBSIDING LATE. FRI...FOR NOW LOOKS LIKE FAIRLY LIGHT WINDS AND SEAS BELOW 5 FT. && .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/THOMPSON NEAR TERM...WTB SHORT TERM...WTB LONG TERM...THOMPSON AVIATION...WTB/THOMPSON MARINE...WTB/THOMPSON HYDROLOGY...

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