Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 191121 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 721 AM EDT SAT APR 19 2014 .SYNOPSIS... HIGH PRESSURE IN CONTROL WILL RESULT IN A DRY WEEKEND...WITH MILD AFTERNOON/S EXCEPT FOR CHILLY SEA BREEZES ON THE COAST ON SUNDAY. THE DRY WEATHER CONTINUES INTO TUESDAY. LOW PRESSURE AND AN ASSOCIATED COLD FRONT WILL LIKELY BRING A PERIOD OF WET WEATHER TO THE REGION TUESDAY NIGHT INTO A GOOD PORTION OF WEDNESDAY. ANOTHER HIGH BUILDS IN WITH DRY... PLEASANT CONDITIONS INTO LATE NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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7 AM UPDATE... ONLY MINIMAL CHANGE TO THE FORECAST THIS MORNING. ADJUSTED SKIES AS COLD FRONT CONTINUES TO SWEEP ACROSS...SCOURING OUT THE MID/HIGH CLOUD DECKS IN PLACE AND RELEIVING THE CAPE/ISLANDS FROM THE LOW MARINE CLOUDS. AS MENTIONED BY PREVIOUS FORECASTER...DESPITE THE MID LVL COLD ADVECTION WITH THIS FRONT THE W FLOW WILL ALLOW FOR BETTER DOWNSLOPING AND WARMER TEMPERATURES TODAY. CURRENT FORECAST FOR TEMPS/DWPTS ON TRACK SO SAW NO REASON TO FIX. PREVIOUS DISCUSSION... A COLD FRONT WILL CROSS SOUTHERN NEW ENGLAND THIS MORNING. EVEN THOUGH WE ACTUALLY WILL BE COLDER AT 850 MB THAN YESTERDAY...WINDS WILL BE NORTHWEST AS OPPOSED TO EAST. THAT MAKES ALL THE DIFFERENCE THIS TIME OF YEAR...SO IT WILL BE MUCH MILDER TODAY THAN THE LAST FEW DAYS. SKIES WILL BE PARTLY TO MOSTLY SUNNY WITH JUST SOME FAIR WEATHER DIURNAL CUMULUS CLOUDS EXPECTED. A VERY WELL MIXED ATMOSPHERE SHOULD RESULT IN AFTERNOON HIGHS MAINLY IN THE UPPER 50S TO THE LOWER 60S. NORTHWEST WIND GUSTS OF 20 TO 30 MPH ARE ALSO EXPECTED TO DEVELOP BY AFTERNOON...BUT STILL MUCH MORE PLEASANT THAN THE LAST TWO DAYS.
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&& .SHORT TERM /SUNDAY/... TONIGHT... STRONG HIGH PRESSURE WILL BUILD SOUTH FROM EASTERN CANADA. THIS WILL RESULT IN MAINLY CLEAR SKIES/LIGHT WINDS AND IDEAL RADIATIONAL COOLING CONDITIONS. LOW TEMPS WILL BOTTOM OUT IN THE LOWER TO MIDDLE 20S ACROSS PORTIONS OF SOUTHWEST NH/NORTHWEST MA...TO MAINLY THE UPPER 20S TO MIDDLE 30S ELSEWHERE. THESE READINGS ARE QUITE COLD FOR THE LATTER HALF OF APRIL...BUT WILL BE SHY OF ANY RECORDS. SUNDAY... HIGH PRESSURE CENTERED OVER NORTHERN NEW ENGLAND WILL RESULT IN MOSTLY SUNNY SKIES. HOWEVER...IT WILL ALSO GENERATE A NORTHEAST TO EASTERLY FLOW OF AIR OFF THE COLD OCEAN. THIS SHOULD HOLD HIGHS BETWEEN 45 AND 50 ALONG THE COAST. INLAND LOCATIONS SEE HIGHS WELL UP IN THE 50S TO POSSIBLY EVEN A FEW LOWER 60S IN THE LOWER CT RIVER VALLEY. WINDS WILL BE MUCH LIGHTER THAN TODAY...SO IT WILL BE A PLEASANT AFTERNOON INLAND FROM THE COAST. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... OVERVIEW AND MODEL PREFERENCES... 19.00Z MODEL GUIDANCE SUITE SHOWING REASONABLY GOOD AGREEMENT IN THE SYNOPTIC SCALE THROUGH THE LONG TERM. THIS IS EVEN WITHIN A SPLIT FLOW REGIME WHICH IS EXPECTED TO TRANSITION FROM ZONAL TO MORE AMPLIFIED BY LATE IN THE WEEK. THERE ARE SOME TYPICAL BIASES APPARENT BY THE LATTER HALF OF THE WEEK REGARDING A POTENTIAL WAVE OF LOW PRES FOR THIS COMING WEEKEND. WITH THE AGREEMENT THROUGH MOST OF THE PERIOD A CONSENSUS BLEND OF OPERATIONAL AND ENSEMBLE GUIDANCE WILL BE USED...BUT WITH MORE WEIGHT ON ENSEMBLE MEANS WHICH AGREES WITH LATEST WPC LONG RANGE THINKING. AS MENTIONED ABOVE...A ZONAL SPLIT FLOW WILL GIVE WAY TO MORE AMPLIFIED FLOW AS SRN AND NRN STREAM WAVES PHASE TO CREATE A LONGWAVE TROF INVOF THE GREAT LAKES BY MID WEEK. THIS WILL YIELD A DRY-WET TRANSITION FROM MON INTO TUE NIGHT-WED. HOWEVER...THIS MORE AMPLIFIED PATTERN DOES FEATURE A STRONGER RIDGE TO FOLLOW FOR THE LATTER HALF OF THE WEEK. HOWEVER...BECAUSE OF THE DIFFICULTY GUIDANCE HAS WITH THESE MORE AMPLIFIED FLOW PATTERNS TOWARD THE ENDS OF THEIR CYCLES...THERE IS A LOT OF VARIANCE WITH YET ANOTHER LOW PRES WAVE FOR THE WEEKEND. HOWEVER...THE PROPOSED BLEND SHOULD AT LEAST HIT THE MAIN POINTS. DETAILS... SUN NIGHT INTO MON... HIGH PRES CENTER CONTINUES TO SLIDE INTO THE CANADIAN MARITIMES. WITH BUILDING H5 RIDGE...THE SFC RIDGE INVERSION REMAINS IN CONTROL INTO THE THE DAY TUE SUPPORTING A DRY FORECAST EVEN AS A WARM FRONT SLIDES INTO NRN NEW ENGLAND. AFTER A COOL START MON MORNING WITH H85 TEMPS AVERAGING +7C AND FULL MIXING UNDER PARTLY CLOUDY SKIES...SFC TEMPS ARE EXPECTED TO REBOUND TO THE MID 60S. S-SW WINDS MAINLY AROUND 10 MPH ON MON MAY ALLOW FOR A WEAK SEA BREEZE EVEN ON THE E COAST...BUT THIS WOULD BE SHALLOW AND ONLY WITHIN A FEW MILES OF THE SHORE. MON NIGHT INTO TUE WEAK WARM ADVECTION SHOULD KEEP LOWS IN THE 40S...WITH MID-HIGH CLOUDS BUILDING OVER DURING THE DAY TUE. THESE CLOUDS SHOULD STILL ALLOW FULL MIXING TO H85 THOUGH...WHERE TEMPS ARE CLOSER TO +10C. THEREFORE...WARMER TEMPS ON TUE...WITH SOME LOCATIONS BREAKING INTO THE 70S IN SPITE OF THE INCREASING CLOUDS. TUE NIGHT INTO WED... SFC COLD FRONT WILL BE APPROACHING THEN CROSSING THE REGION INTO THE EARLY HALF OF THE DAY ON WED. AM NOTING THE GUIDANCE DOES SUPPORT A SECONDARY FRONTAL WAVE SLIDING ALONG THIS FRONT ALONG WITH A MODEST 30-40 KT LLJ. THIS SUGGESTS IT MAY BE A LITTLE SLOWER MOVING THAN SOME ENSEMBLE MEMBERS SUGGEST...AND THE OPERATIONAL ECMWF IS A BIT SLOWER. THEREFORE...WILL SLOW THE OVERALL RAIN THREAT...ALLOWING IT TO CONTINUE INTO MID DAY WED. MODEST LIFT AND PWATS AROUND 1.0 SUGGESTS WIDESPREAD RAIN EVENT...BUT NOT AS STRONG AS SOME EARLIER THIS SPRING. MOST QPF AMOUNTS SHOULD LIE SOMEWHERE BETWEEN 0.25 AND 0.5 INCHES GIVEN ITS SLIGHTLY FASTER MOVEMENT AND WEAKER LLJ ENERGY. THU INTO FRI... AMPLIFIED RIDGE GAINS CONTROL AS LONGWAVE TROF SLIDES OFFSHORE. MAINLY DRY FORECAST EXPECTED. DESPITE THE INITIAL COLD ADVECTION ON THU THE BUILDING RIDGE SHOULD HEIGHTS/MID LVL TEMPS RISING. THEREFORE...LOOKING AT TEMPS NEAR TO SLIGHTLY ABOVE AVERAGE...ESPECIALLY FOR HIGHS GIVEN DECENT LATE APRIL SUN. NEXT WEEKEND... ANOTHER TRANSITIONAL PERIOD AS LONGWAVE TROF APPROACHES FROM THE W. THIS SUGGESTS UNSETTLED AND POTENTIALLY WET CONDITIONS FOR AT LEAST SOME OF THE WEEKEND...BUT WITH A LOT OF VARIABILITY AND MODEL DIFFICULTY RESOLVING AMPLIFIED FLOW BY DAY 7...CONFIDENCE IS LOW IN EXACT TIMING OR HOW WET IT MAY BE. WHILE THERE IS SOME AGREEMENT THAT THE ACTUAL ATTENDANT LOW WOULD BE AN INSIDE RUNNER...HOW FAR NORTH THE CORRIDOR OF STRONGEST DYNAMICS GOES IS DIFFICULT TO RESOLVE. LOOK FOR MORE UPDATES AS WE APPROACH. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...TODAY THROUGH SUNDAY...HIGH CONFIDENCE. TODAY... MAINLY VFR FROM NOW ON. W-SW WINDS WILL VEER TO THE NW THROUGH THE MORNING...INCREASING IN SPEED. GUSTS 20-25 LIKELY THROUGH THE DAY. TONIGHT AND SUNDAY... VFR CONDITIONS. GUSTY NORTHWEST WINDS DIMINISH THIS EVENING. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... SUN NIGHT INTO TUE...HIGH CONFIDENCE. MAINLY VFR. WINDS SHIFT FROM THE W ON MON TO THE S ON TUE. TUE NIGHT INTO WED...MODERATE CONFIDENCE. VFR GIVES WAY TO MIX OF MVFR/IFR IN PERIODS OF RAIN AND LOW CIGS. CONDITIONS GRADUALLY IMPROVE DURING THE DAY ON WED...ALTHOUGH AS THINGS IMPROVE THERE IS THE CHANCE FOR 25-30 KT W-NW WIND GUSTS ON WED.
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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 /TODAY THROUGH SUNDAY/...HIGH CONFIDENCE. TODAY... SCA SEAS WILL CONTINUE ACROSS THE EASTERN ATLANTIC WATERS TODAY AS A RESULT OF EASTERLY SWELL FROM A DISTANT LOW PRESSURE SYSTEM. IN ADDITION...HAVE HOISTED SCA HEADLINES FOR NORTHWEST WIND GUSTS ALONG THE NEAR SHORE WATERS OF THE EASTERN MA COAST THIS AFTERNOON. ENOUGH MIXING OVER THE LAND SHOULD RESULT IN A FEW HOURS OF GUSTS UP TO 25 KNOTS...INCLUDING BOSTON HARBOR. TONIGHT... LOOKS LIKE WE MAY SEE A PERIOD OF NORTHERLY 25 KNOT WIND GUSTS OVER THE EASTERN WATERS IN A SURGE OF COLD ADVECTION. KEPT THE EASTERN ATLANTIC WATERS IN SCA HEADLINES...BUT ITS POSSIBLE WE MAY NEED TO EXTEND THEM INTO CAPE COD BAY AND NANTUCKET SOUND FOR A TIME. ITS MARGINAL AND SINCE ITS 2ND PERIOD DECIDED TO DEFER TO THE NEXT SHIFT. SUNDAY... WINDS SHOULD REMAIN BELOW SCA THRESHOLDS. HOWEVER...MARGINAL SCA SEAS THOUGH MAY LINGER INTO THE LATE MORNING/EARLY AFTERNOON ACROSS PORTIONS OF THE EASTERN ATLANTIC WATERS BEFORE DIMINISHING. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... SUN NIGHT INTO TUE...HIGH CONFIDENCE. HIGH PRES REMAINS IN CONTROL ACROSS THE WATERS. THEREFORE...ASIDE FROM WHAT MAY BE A FEW NEAR SHORE GUSTS APPROACHING 25 KT ON TUE FROM THE S-SW...MAINLY QUIET BOATING WEATHER IS EXPECTED. TUE NIGHT INTO WED...MODERATE CONFIDENCE. COLD FRONT APPROACHES THEN CROSSES THE WATERS EARLY WED WITH PERIODS OF RAIN. TUE NIGHT INTO WED...S WINDS SHOULD REMAIN BELOW SCA THRESHOLDS BUT A BUILDING S SWELL ON THE SRN AND ERN OCEAN WATERS MAY BREAK 5 FT...LEADING TO THE NEED FOR SMALL CRAFT ADVISORIES. ON TUE...ONCE WINDS SHIFT TO THE W-NW WIND GUSTS 25-30 KT AND CONTINUED 5-7 FT SEAS WILL LEAD TO THE NEED FOR SMALL CRAFT ADVISORIES ON ALL WATERS. && .FIRE WEATHER... TODAY... NORTHWEST WIND GUSTS OF 20 TO 30 MPH ARE EXPECTED TO DEVELOP BY AFTERNOON. IN ADDITION...MINIMUM AFTERNOON RELATIVE HUMIDITIES ARE EXPECTED TO DROP TO BETWEEN 20 AND 30 PERCENT. AFTER COORDINATION WITH FIRE WEATHER CONTACTS WILL NOT ISSUE ANY FIRE WEATHER HEADLINES...GIVEN CURRENT FUEL MOISTURES. TOMORROW... ALTHOUGH THE DRY WEATHER CONTINUES...WINDS WILL BE MUCH LIGHTER AND HIGH TEMPS A BIT COOLER. && .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 UNTIL NOON EDT SUNDAY FOR ANZ250-254. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ251. SMALL CRAFT ADVISORY FROM NOON TODAY TO 8 PM EDT THIS EVENING FOR ANZ230.
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&& $$ SYNOPSIS...FRANK/DOODY NEAR TERM...DOODY SHORT TERM...FRANK LONG TERM...DOODY AVIATION...FRANK/DOODY MARINE...FRANK/DOODY FIRE WEATHER... HYDROLOGY...

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