Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 200547 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 147 AM EDT WED MAY 20 2015 .SYNOPSIS...
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A COLD FRONT MOVED ACROSS SOUTHERN NEW ENGLAND OVERNIGHT AND WILL USHER IN A DRY AND SEASONABLY COOL CANADIAN AIRMASS ACROSS THE REGION TODAY AND THU. A TROUGH OF LOW PRESSURE MAY BRING A PERIOD OF LIGHT RAIN TO RI AND SOUTHEAST MA THU NIGHT. THEN A FEW BRIEF SHOWERS ARE POSSIBLE FRIDAY AHEAD OF A COLD FRONT...HOWEVER MUCH OF THE REGION REMAINS DRY. MUCH COOLER BUT DRY WEATHER RETURNS FRI NIGHT AND SAT FOLLOWED BY A GRADUAL WARMING TREND SUNDAY AND MONDAY.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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2 AM UPDATE... COLD FRONT MOVING ACROSS CAPE COD AND THE ISLANDS AT 130 AM. POST FRONTAL AIRMASS WILL SCOUR OUT LOW CLOUDS AND FOG NEXT FEW HOURS ACROSS THIS REGION. UPSTREAM MUCH DRIER AIR WITH DEW PTS IN THE L60S IN EASTERN MA THEN DROPPING OFF INTO THE 40S ACROSS WESTERN MA AND CT. A MODEST WNW WIND WITH GUSTS UP TO 25 MPH WILL ACCOMPANY THE CHANGE IN AIRMASS.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/... WEDNESDAY... MUCH DRIER AIR CONTINUES WILL WORK INTO SOUTHERN NEW ENGLAND BEHIND THE COLD FRONT. PARTLY SUNNY SKIES ARE EXPECTED BUT THERE WILL BE SOME SCATTERED DIURNAL CUMULUS CLOUDS ESPECIALLY ACROSS OUR NORTHERN ZONES. 850 MB TEMPS DROP TO BETWEEN 0C AND +4C BY 18Z...BUT THERE WILL BE DEEP MIXING. THEREFORE...EXPECT HIGHS TO REACH WELL INTO THE 60S...WITH PERHAPS A FEW LOCATIONS TOUCHING 70 ACROSS RHODE ISLAND/SOUTHEAST MA. IT WILL BE BLUSTERY AS GOOD MIXING WILL RESULT IN A FEW HOURS OF NORTHWEST WIND GUSTS OF 25 TO 30 MPH DURING THE AFTERNOON. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... */ HIGHLIGHTS... - SEASONABLE AND DRY UNDER HIGH PRESSURE THURSDAY - SWEEPING COLD FRONT FRIDAY - RETURN OF DRY AND COOLER CONDITIONS FOR THE WEEKEND - PERHAPS A RETURN OF WET-WEATHER EARLY NEXT WEEK OVERVIEW AND MODEL PREFERENCES... WITH 19.12Z MODEL GUIDANCE CONTINUING TO SHOW REASONABLY GOOD AGREEMENT THROUGH THE LONG TERM...A BLEND OF OPERATIONAL GUIDANCE AND PERSISTENCE WILL BE USED AS A BASELINE. THERE ARE A FEW TWEAKS TO MAKE. THE LONGWAVE TROF THAT SETTLES ACROSS ERN CANADA AND THE NE CONUS WILL ALLOW FOR A FAIRLY COLD AIRMASS TO ADVECT ACROSS THE REGION WITH A STRONG VORTEX MOVING THROUGH ON FRI...MANIFESTING AS A COLD FRONT. MODEL DWPTS ARE LIKELY TOO HIGH HERE. WHICH MEANS THAT SHOULD THE PRES GRADIENT SLACKEN ENOUGH BOTH FRI AND SAT NIGHTS...MAY NEED TO MONITOR FOR A PERIOD WHERE FROST IS POSSIBLE. ALSO...AS NOTED BY PREVIOUS FORECASTER...THIS DRY AIR WOULD ALSO SUGGEST HIGHER FIRE WEATHER POTENTIAL DEPENDENT ON RAINFALL TODAY/THIS EVENING. DETAILS... WED NIGHT INTO THU NIGHT... MAINLY DRY WX EXPECTED AS HIGH PRES MOVES ACROSS THE REGION. WILL LIKELY SEE SOME PERSISTENT CLOUD COVER AT TIMES THOUGH...GIVEN UPPER LVL CYCLONIC CURVATURE AND MODEST MID LVL MOISTURE. +3C TO +5C H85 TEMPS SHOULD STILL BE REACHED...IF NOT EVEN SLIGHTLY HIGHER. THEREFORE...SUSPECT MAX/MIN VALUES NEAR SEASONAL NORMALS. FRI... FAIRLY ROBUST ARCTIC INFLUENCED VORTEX WILL BE MOVING THROUGH THE BASE OF THE LONGWAVE TROF ACROSS THE NE CONUS AND ERN CANADA. THE SFC REFLECTION IS ITSELF A STRONG COLD FRONT WITH DECENT BAROCLINIC PACKING EVIDENT. THEREFORE...PLENTY OF POTENTIAL FOR LIFT WITH THIS FEATURE AS IT MOVES ACROSS THE REGION FRI. THE LIMITING FACTOR IS MOISTURE AS PREVIOUS LONG TERM FORECASTER NOTED. PWATS REALLY ONLY TOP OUT AROUND 0.60 INCHES. BY THE AFTERNOON. STILL FEEL THE SLIGHT CHANCE POPS ADVERTISED ARE WARRANTED...ESPECIALLY JUST GIVEN HOW HIGH THE LIFT POTENTIAL IS WITH THE FRONT ITSELF. THERE IS A LITTLE BIT OF LOW LVL INSTABILITY INVOF THE BL TO WORK WITH AS WELL. THEREFORE...WILL MAINTAIN PRECIP CHANCES AS THEY STAND FOR THE TIME BEING. FRI NIGHT INTO SAT... AS MENTIONED ABOVE THE KEY FOR THIS TIME PERIOD IS THE POTENTIALLY DRY AND COOL AIRMASS WHICH IS PROGGED TO SETTLE ACROSS THE REGION. IN FACT 1000-500 THICKNESS VALUES ARE SUB 540DAM FOR MUCH OF THE REGION. WITH H85 TEMPS DIPPING BELOW 0C FOR SAT. THEREFORE...WILL NEED TO MONITOR FOR LOW DWPTS AND RH VALUES BY DAY...AND POTENTIALLY NEAR FREEZING TEMPERATURES FOR COLDER VALLEYS AT NIGHT. CONFIDENCE IS NOT HIGH ENOUGH TO ALARM ON FROST POTENTIAL AT THIS POINT GIVEN THERE IS SOME QUESTION IN THE PRES GRADIENT AND WINDS REMAINING ELEVATED...BUT FEEL IT IS AT LEAST WORTH MENTIONING/MONITORING. EARLY NEXT WEEK... SUBTROPICAL RIDGING WILL ONCE AGAIN BE GAINING STRENGTH THROUGH THE PERIOD...ALLOWING FOR A WARMING OF THE COLUMN ACROSS THE NE THROUGH THE PERIOD. ASIDE FROM THE WARMING...INDICATIONS OF A WARM FRONTAL PASSAGE WITH POTENTIAL FOR PRECIP/CONVECTION INDICATED FOR TUES. SOMETHING TO KEEP AN EYE ON. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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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 THURSDAY/...HIGH CONFIDENCE. 2 AM UPDATE... IFR CONDITIONS OVER SOUTHEAST MA WILL IMPROVE TO VFR BY 09Z. ELSEWHERE VFR AND DRY WEATHER PREVAILS TODAY/TONIGHT AND THU. WNW WINDS WILL INCREASE TO G25 KT BY MIDDAY AND THEN DIMINISH WITH SUNSET. LESS WIND TONIGHT AND THU. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. GUSTY WNW WINDS G25 KT 14Z- 00Z TODAY. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. GUSTY WNW WINDS G25 KT FROM 14Z-00Z TODAY. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY... THU NIGHT THROUGH FRI...HIGH CONFIDENCE. MAINLY VFR. WINDS SHIFT FROM NW ON THU...TO S-SW ON FRI BEFORE A COLD FRONT MOVES THROUGH. A FEW SHOWERS POSSIBLE FRI...BUT IT/S LIKELY MOST AREAS REMAIN DRY. SEA BREEZES LIKELY THU. SAT AND SUN...HIGH CONFIDENCE. VFR. W WINDS ON SAT...MAY GUST TO ABOUT 25 KT NEAR SHORELINES. WEAKER WINDS ON SUN...WITH SEA BREEZES POSSIBLE.
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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 /TONIGHT THROUGH TUESDAY NIGHT/... TONIGHT...MODERATE TO HIGH CONFIDENCE. MAIN CONCERN WILL BE FOR AREAS OF FOG ACROSS OUR SOUTHERN WATERS FOR THE FIRST PART OF THE NIGHT...SOME OF WHICH MAY BE LOCALLY DENSE. OTHERWISE...SOUTHWEST WINDS AT 10 TO 15 KNOTS WILL SHIFT TO THE NORTHWEST AFTER MIDNIGHT BEHIND A STRONG COLD FRONT. SOME GUSTS INTO THE LOWER 20 KNOTS ARE EXPECTED WITH PRESSURE RISES BEHIND THE FRONT. WEDNESDAY...HIGH CONFIDENCE. A FEW HOURS OF NORTHWEST WIND GUSTS OF 25 KNOTS EXPECTED NEAR SHORE WITH DEEP MIXING OVER THE LAND. HAVE HOISTED SCA HEADLINES MAINLY FOR OUR NEAR SHORE WATERS. STRONGEST WINDS LOOK TO BE ACROSS OUR EASTERN ZONES...SO DID LEAVE OUT BLOCK ISLAND SOUND OUT FOR NOW. OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY...HIGH CONFIDENCE. WED NIGHT INTO FRI... WINDS AND SEAS GENERALLY REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH THIS PERIOD. WINDS WILL BE SHIFTING FROM NW...TO S-SW BY FRI. SEA BREEZES LIKELY ALONG THE COAST. SAT... WINDS WILL INCREASE OUT OF THE W ON SATURDAY SUCH THAT GUSTS MAY APPROACH 25 KT IN THE AFTERNOON. SMALL CRAFT ADVISORIES MAY BE NEEDED. SUN... ANOTHER ROUND OF QUIET BOATING WEATHER WITH HIGH PRES. && .FIRE WEATHER... WEDNESDAY... NORTHWEST WIND ARE EXPECTED TO GUST BETWEEN 25 AND 30 MPH FOR A FEW HOURS WEDNESDAY AFTERNOON. IN ADDITION...MINIMUM AFTERNOON RELATIVE HUMIDITY VALUES ARE EXPECTED TO DROP TO BETWEEN 25 AND 30 PERCENT IN A WELL MIXED ATMOSPHERE. RAINFALL AMOUNTS VARIED CONSIDERABLY TODAY IN SHOWERS. MANY LOCATIONS IN CT/RI AND SOUTHEAST MA RECEIVED NEAR OR MORE THAN 0.25 INCHES OF RAIN WITH LOWER AMOUNTS TO THE NORTH. AFTER COLLABORATING WITH OUR FIRE WEATHER PARTNERS...WILL GO AHEAD AND ISSUE A SPECIAL WEATHER STATEMENT FOR JUST MASSACHUSETTS. THIS IS WHERE THE LEAST AMOUNT OF RAIN FELL TODAY. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 6 PM EDT THIS EVENING FOR ANZ230>236-250-251.
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&& $$ SYNOPSIS...FRANK/DOODY NEAR TERM...NOCERA SHORT TERM...FRANK LONG TERM...DOODY AVIATION...NOCERA/DOODY MARINE...FRANK/DOODY FIRE WEATHER...

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