Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 201508 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1107 AM EDT SAT SEP 20 2014 .SYNOPSIS... MILDER TEMPERATURES RETURN TODAY AND TOMORROW. HOWEVER A FEW SHOWERS ARE POSSIBLE LATE TONIGHT AND EARLY SUNDAY AS WELL. A COLD FRONT CROSSES NEW ENGLAND SUNDAY NIGHT...WHILE LOW PRESSURE RAPIDLY PASSES SOUTHEAST OF NANTUCKET ON ITS WAY TO NOVA SCOTIA. AFTER THIS COLD FRONT PASSES OFFSHORE MONDAY MORNING...HIGH PRESSURE DOMINATES THROUGH ALL OF NEXT WEEK. MILD TEMPS LINGER MONDAY BUT THEN BECOME COOLER THAN NORMAL THEREAFTER BEFORE MODERATING LATE NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1105 AM UPDATE... A DECK OF BROKEN LOW-MID CLOUDINESS COVERED SOUTHERN NH/WESTERN MA AND NORTHERN CT AS OF LATE THIS MORNING. THERE WAS ALSO SOME SCATTERED CUMULUS CLOUDS BEGINNING TO DEVELOP ACROSS THE SOUTH COAST...WHILE THE REST OF THE REGION WAS MOSTLY SUNNY. OVERALL...SHOULD SEE THE BROKEN DECK OF CLOUDS ACROSS THE INTERIOR SCATTER OUT TO SOME DEGREE THIS AFTERNOON. MOST AREAS WILL SEE AT LEAST PARTLY SUNNY DEVELOP ACROSS THE REGION. 850 MB TEMPS WARMING TO BETWEEN +8C TO +10C AND INCREASED MIXING WAS ALLOWING FOR A RAPID RECOVERY FROM THE VERY COLD START EARLY THIS MORNING. HIGHS SHOULD ACTUALLY TOP OUT IN THE UPPER 60S TO THE LOWER 70S IN MANY LOCATIONS BY MID TO LATE AFTERNOON.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... TONIGHT... TRICKY FORECAST FOR TONIGHT. GUIDANCE CONTINUES TO REALLY STRUGGLE WITH A WEAK AREA OF CONVECTION ASSOCIATED WITH TROPICAL MOISTURE CURRENTLY SITTING OFF OF THE SE COAST. WHILE THE INCOMING AND DEEPENING TROF TO THE W IS LIKELY TO KICK THIS WAVE TO THE N...THE SPEED AND EXACT TRAJECTORY REMAIN IN QUESTION DUE TO AN OVERALL LACK OF BAROCLINICITY TO WORK WITH. 12Z GUIDANCE KEPT THE FINAL UPPER LVL JET STREAK AND SFC WAVE MAINLY E OF THE 40/70 BENCHMARK WHILE 00Z RUNS HAVE NOW BROUGHT IT INSIDE BY 12Z. IN ANY CASE...EXPECT INCREASING MOISTURE TONIGHT AS PWATS APPROACH 1.5 INCHES BY THE EARLY MORNING HOURS /ABOUT 1-2 STD DEVIATIONS ABOVE NORMAL/. WHILE THE BULK OF THE DYNAMIC FORCING AND INSTABILITY REMAIN TO THE...DO NOTICE AS AN INVERTED TROF EXTENDS INTO SRN NEW ENGLAND AFTER 06Z...THAT A POCKET OF MODEST INSTABILITY FOLLOWS. MU CAPE VALUES OF ABOUT 500-1000J/KG ABOVE THE NEAR SFC WARM LAYER. THIS IS COLOCATED WITH THE HIGHER PWATS AND K-VALUES NEAR 30...SO IT IS POSSIBLE THAT MODEST CONVECTION /SHOWERS AND A POSSIBLE T-STORM/ SPILLS ACROSS MAINLY THE SRN TIER OF SRN NEW ENGLAND THROUGH THE MORNING HOURS /PARTICULARLY ABOUT 09Z-15Z/. THE HIGHER PWATS SUGGEST A POCKET OF HEAVY RAIN CAN/T BE RULED OUT. WILL CONTINUE TO HIGHLIGHT CHANCE POPS FROM SRN CT-RI-SE MA WITH SLIGHT CHANCE POPS FURTHER N UNTIL THIS CAN BE BETTER RESOLVED. THANKFULLY SHEAR IS MODEST AND STRONGER ASSOCIATED WITH A COLD FRONT WELL TO THE NW OF NEW ENGLAND...BUT THIS WILL NEED TO BE WATCHED. THERE ARE A COUPLE OF MITIGATING FACTORS TO NOTE...HENCE THE CHANCE AND SLIGHT CHANCE POPS...ONGOING CONVECTION OFFSHORE WHERE UPPER LVL AND LOW LVL JET IS STRONGER COULD USURP INSTABILITY AND MOISTURE AWAY FROM SRN NEW ENGLAND. ALSO...SUSPECT AN AREA OF SUBSIDENCE WILL RESIDE ACROSS THE REGION IN BETWEEN THE NRN SYSTEM AND THIS WEAKER OFFSHORE WAVE. MODELS DO REFLECT THIS AS A DRY LAYER FROM ABOUT H6 AND UP. SUN... THREAT FOR MODEST CONVECTION LINGERS INTO TO ABOUT MID DAY AS THE OFFSHORE WAVE MAKES ITS CLOSEST PASS. HOWEVER...SUSPECT THAT A PERIOD OF MAINLY DRY CONDITIONS MAY PREVAIL AS THE SYSTEM MOVES OFFSHORE AND A DRY SLOT WITH SUBSIDENCE DEVELOPS ACROSS THE AREA DURING THE AFTERNOON AND EARLY EVENING. THIS AREA OF SUBSIDENCE IS THE RESULT OF THE OFFSHORE STORM SYSTEM AND A SLOW APPROACHING COLD FRONT TO THE W...ALONG WHICH IS LIKELY TO BE SOME AFTERNOON AND EVENING CONVECTION. AT THIS TIME...INSTABILITY LOOKS MODEST AT BEST DESPITE THE INCREASE IN SFC DWPTS. BREAKS OF SUN ARE POSSIBLE...WHICH MAY HAVE TO BE WATCHED...BUT AT THIS TIME...AT LEAST THROUGH 00Z MON...SUSPECT THE SHOWERS AND THUNDERSTORMS REMAIN MOSTLY TO THE W. HIGH TEMPS IN THE MID-UPPER 70S ARE EXPECTED...ALTHOUGH A FEW SPOTS MAY REACH AROUND THE 80F MARK ESPECIALLY IF SOME BREAKS OF SUN ARE OBSERVED. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... HIGHLIGHTS... * LOW RISK OF SHOWERS SUN NIGHT THEN DRY MUCH OF NEXT WEEK * MILD SUN NIGHT/MON THEN COOLER THAN NORMAL MIDWEEK BEFORE MODERATING LATE NEXT WEEK SYNOPTIC OVERVIEW AND GUIDANCE EVALUATION... 00Z DETERMINISTIC AND ENSEMBLE GUIDANCE ARE IN GOOD AGREEMENT ON THE LARGE SCALE FLOW WHICH FEATURES A HIGH AMPLITUDE TROUGH MOVING ACROSS THE NORTHEAST SUN NIGHT AND MON...THEN SLOWLY LIFTING OUT INTO THE MARITIMES THE MIDDLE OF NEXT WEEK. THIS WILL YIELD A LOW RISK OF SHOWERS SUN NIGHT FOLLOWED BY COOLER WEATHER MON NIGHT INTO THE MIDDLE OF NEXT WEEK. HEIGHT RISES LOOK TO BE A GOOD BET AS SUBTROPICAL RIDGE BUILDS INTO THE REGION LATE NEXT WEEK. PRECISE TEMPS WILL BE DIFFICULT AT THIS TIME RANGE AS ALL MODEL GUIDANCE INDICATES SOME WEAKNESSES WITHIN THE NORTHEASTERN PERIPHERY OF THE SUBTROPICAL RIDGE WITHIN THE NORTHEAST STATES. SUN NIGHT...TRAILING NORTHERN STREAM SHORT WAVE AND ATTENDING SURFACE COLD FRONT SWEEP ACROSS THE REGION. MODEST QG FORCING AND DEEP LAYER MOISTURE ACCOMPANY THE TROUGH AND SURFACE FRONT. THUS EXPECT SCT SHOWERS WITH HIGHEST PROBS NORTHWEST MA INTO SOUTHWEST NH. IT WILL REMAIN MILD GIVEN FROPA NOT UNTIL AFTER DAYBREAK MONDAY. MONDAY...ANY LINGERING SHOWERS ASSOCIATED WITH THE FRONT WILL CLEAR CAPE COD EARLY IN THE MORNING. THEREAFTER EXPECTING A MIX OF SUN AND CLOUDS ALONG WITH A WELL MIXED BLYR AS WEST WINDS GUST UP TO 25 MPH. HIGHS SHOULD CLIMB WELL INTO 70S INCLUDING CAPE COD AND THE ISLANDS AS WIND DIRECTION WILL BE WESTERLY. TUESDAY THROUGH THURSDAY...1035 MB HIGH CREST OVER NEW ENGLAND THIS PERIOD BRINGING MILD DAYS BUT COOL NIGHTS. LEANED TOWARD THE COOLER MAVMOS DURING THE NIGHTS. DRY WEATHER PREVAILS ALONG WITH LIGHT WINDS. FRIDAY...SUBTROPICAL RIDGE BUILDS NORTHWARD ALONG WITH MODERATING TEMPS. DIFFICULT TO SAY HOW WARM GIVEN SOME GUIDANCE SUGGEST A WEAKNESS WITHIN THE RIDGE. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SUNDAY/... 7 AM UPDATE... NO MAJOR CHANGES TO 06Z TAFS. EARLIER DISCUSSION BELOW. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THROUGH TODAY...HIGH CONFIDENCE. MAINLY VFR OUTSIDE OF SOME LOCALIZED FOR AT TYPICALLY PRONE TERMINALS THIS MORNING. WINDS S-SW WITH A FEW GUSTS TO AROUND 20 KT TODAY. TONIGHT...MODERATE CONFIDENCE. VFR TO START...BUT SOME TERMINALS SEE MVFR CIGS AND POSSIBLY IFR VSBYS IN SOME LOW CLOUDS AND FOG ESPECIALLY AFTER 04Z. BEST CHANCE LOOKS TO BE CT AND W MA TERMINALS...BUT SOME LOWER CATEGORIES FURTHER E NOT OUT OF THE QUESTION. LATE NIGHT SHOWER OR POSSIBLY EVEN AN ISOLATED T-STORM POSSIBLE MAINLY SRN CT/RI AND SE MA. SUN... MVFR/VFR START GIVES WAY TO MAINLY VFR DURING THE AFTERNOON AND EARLY EVENING. ISOLATED -SHRA POSSIBLE. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF THROUGH TODAY...LOWER CONFIDENCE IN TIMING OF MVFR POSSIBLE LATE TONIGHT/EARLY SUN MORNING. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... HIGH CONFIDENCE THROUGH THE PERIOD...EXCEPT MODERATE CONFIDENCE SUNDAY NIGHT. VFR THRU THE PERIOD. THE ONLY EXCEPTION WILL BE SUNDAY NIGHT WHEN POSSIBLE MVFR MAY ACCOMPANY SCT SHOWERS. MODEST W WIND MON 15-20 KT. OTHERWISE FAIRLY LIGHT WINDS AND DRY WEATHER PREVAILS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SATURDAY NIGHT/... TODAY...HIGH CONFIDENCE. S-SW WINDS DEVELOP THROUGH THE DAY TODAY. WIND GUSTS MAY APPROACH 25 KT AT TIMES ALONG THE NRN TIER OF WATERS AGAINST THE GULF OF MAINE...BUT MOST GUSTS SHOULD REMAIN BELOW. SEAS MAINLY 4 FT OR LESS. TONIGHT...MODERATE CONFIDENCE. S WIND CONTINUE...BUT DIMINISH SOMEWHAT OVERNIGHT TONIGHT. CONDITIONS REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS ALONG WITH SEAS. SOME SHOWERS AND EVEN A POSSIBLE T-STORM OVER THE SE WATERS AFTER 04Z ALONG WITH THE POTENTIAL FOR FOG AND REDUCED VSBYS. SUN...MODERATE CONFIDENCE. WINDS REMAIN S AND EVEN SHIFT TO THE SE THROUGH THE DAY. WHILE WIND GUSTS GENERALLY REMAIN BELOW SMALL CRAFT THRESHOLDS...NOT OUT OF THE QUESTION SEAS REACH THE 5 FT MARK ON THE SRN OCEAN WATERS BY LATE IN THE DAY. OTHERWISE...BULK OF THE SHOWERS AND THUNDERSTORMS SHOULD SHIFT OFFSHORE THROUGH THE MORNING HOURS. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... MODEST W WIND MON INTO TUE THEN LIGHT WINDS AS HIGH PRES CREST OVER THE AREA TUE NIGHT AND BEYOND. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/DOODY NEAR TERM...FRANK SHORT TERM...DOODY LONG TERM...NOCERA AVIATION...NOCERA/DOODY MARINE...NOCERA/DOODY

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