Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 021331 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 931 AM EDT TUE JUN 2 2015 .SYNOPSIS... STALLED FRONT SOUTH OF NEW ENGLAND WILL KEEP UNSEASONABLY COOL AND WET CONDITIONS IN PLACE THROUGH TODAY. HIGH PRESSURE RETURNS WITH DRIER WEATHER WEDNESDAY AND THURSDAY. SHOWERS ARE POSSIBLE FRIDAY INTO SATURDAY...AS ANOTHER COLD FRONT MOVES THROUGH THEN HIGH PRESSURE FOLLOWS FOR SUNDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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915 AM UPDATE... DECIDED TO CANCEL THE FLASH FLOOD WATCH AS RAINFALL RATES CONTINUE TO EASE AT LESS THAN TWO TENTHS OF AN INCH PER HOUR. THUS THREAT OF FLOODING HAS DIMINISHED. NEVERTHELESS PERIODS OF LIGHT TO MODERATE RAIN WILL CONTINUE THRU THE MORNING. BACK EDGE OF THE RAIN SHIELD IS NOW ENTERING NORTHWEST BERKSHIRE COUNTY. MID LEVEL TROUGH IS SOMEWHAT PROGRESSIVE SO EXPECTING THIS BACK EDGE OF RAIN SHIELD TO MAKE STEADY PROGRESS NW TO SE RESULTING IN RAIN ENDING AROUND MIDDAY NORTHWEST MA TO ABOUT SUNSET OVER SOUTHEAST MA. ANOTHER UNSEASONABLY COOL DAY AHEAD WITH OVERCAST CONDITIONS ALONG WITH PERIODS OF RAIN AND COOL NORTHEAST FLOW OFF THE CHILLY OCEAN WATERS. LATE DAY HIGHS OF ONLY LOW TO MID 50S WITH COOLEST READINGS ALONG EASTERN MA COAST GIVEN PROXIMITY TO MARITIME FLOW AND LONGER DURATION OF RAINFALL. WHILE THESE TEMPS WILL LIKELY JUST MISS SETTING A NEW RECORDS...THESE VALUES ARE 20-25 DEGS BELOW NORMAL. PREVIOUS FORECAST ON TRACK SO FAR...THEREFORE NO MAJOR CHANGES WITH THIS UPDATE OTHER THAN CANCELLING THE FLASH FLOOD WATCH. EARLIER DISCUSSION BELOW. ================================================================ PREVIOUS DISCUSSION... COLD FRONT STALLED OFFSHORE IS PROVIDING ONE FOCUS FOR LIFT AS A LOW LEVEL 20-25 KNOT SOUTH JET RIDES UP OVER THE TOP. BUT THE BEST LIFT HAS BEEN WITH FGEN FORCING ALONG THE TEMPERATURE GRADIENT AT 925 MB AND 900 MB...ACROSS WESTERN/CENTRAL MASS AND NORTHERN CT. RADAR OBSERVATIONS FROM UPSTREAM SHOW ADDITIONAL WET WEATHER MOVING UP FROM NEW JERSEY AND DELMARVA. WET WEATHER CONTINUES TO MOVE ACROSS SOUTHERN NEW ENGLAND TODAY. PRECIPITABLE WATER VALUES ARE 1.50 TO 1.75 INCHES ALONG THE COAST AND 1.25 INCHES OVER WESTERN/CENTRAL MASS. BASED ON THIS WE EXPECT WET WEATHER TO CONTINUE TO MOVE ACROSS SOUTHERN NEW ENGLAND TODAY. NORTHERN STREAM SHORTWAVE MOVES OVER THE REGION BY THIS EVENING. AS IT APPROACHES IT WILL PUSH THE FORCING FARTHER EAST THIS AFTERNOON. THIS SHOULD MOVE THE HEAVIER SHOWERS OVER THE COASTAL PLAIN AT THAT TIME. EXTRAPOLATING THE BACK EDGE OF THE RAIN SUGGESTS IT WILL END IN THE WEST IN THE EARLY AFTERNOON...AND IN MUCH OF THE EAST TOWARD EVENING. THE RAIN MAY LINGER ALONG THE SOUTH COAST PAST THIS EVENING. WE WILL CONTINUE TO FORECAST CATEGORICAL POPS FOR SHOWERS WITH A COOL NORTHEAST LOW LEVEL FLOW OVER THE REGION. WITH THAT IN MIND WE WILL FORECAST TEMPERATURES TO SLOWLY CLIMB INTO THE 50S THIS AFTERNOON. THAT MAY BE OPTIMISTIC RIGHT ALONG THE EAST MASS COASTLINE. WITH ADDITIONAL RAIN OF 1/2 INCH TO 1 INCH EXPECTED TODAY...WE WILL MAINTAIN A FLASH FLOOD WATCH THROUGH THE DAY. THE PRE-EVENT DRYNESS OF THE SOIL IS PROBABLY HELPING US ABSORB THE VOLUME OF WATER. BUT POOR DRAINAGE AREAS AND SMALL STREAMS CONTINUE TO BE OF CONCERN.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... TONIGHT... THE UPPER SHORTWAVE MOVES THROUGH AND OFF TO THE EAST. THIS WILL TURN THE UPPER FLOW NORTHWEST AND PUSH THE LAST OF THE PCPN OFFSHORE. WE EXPECT AT LEAST PARTIAL CLEARING FROM NORTHWEST TO SOUTHEAST DURING THE NIGHT. WITH DEW POINTS IN THE 40S...MIN TEMPS SHOULD ALSO BE IN THE 40S. WEDNESDAY... HIGH TEMPERATURES TODAY RUNNING ABOUT 20-25 DEGS BELOW NORMAL! NORMAL HIGH TODAY IS 70-75. HIGH PRESSURE OVER EASTERN CANADA BUILDS OVER NEW ENGLAND WITH DRY AIR/SUNSHINE. BUT THE SURFACE FLOW AROUND THE HIGH WILL DRAW WINDS BACK AROUND OUT OF THE NORTHEAST OFF THE WATER. WITH THE WIND COMING OFF WATER TEMPS IN THE LOWER 50S...THIS NATURAL AIR CONDITIONING SHOULD KEEP COASTAL TEMPERATURES IN EASTERN MASS AROUND 60...POSSIBLY JUST IN THE UPPER 50S. MEANWHILE THE CT VALLEY WILL BE LESS INHIBITED BY THE MARINE AIR AND SHOULD MIX TO AT LEAST 900 MB. TEMPS AT THE TOP OF THAT LAYER WOULD SUPPORT MAX TEMPS NEAR 70. HIGH TEMPERATURES TODAY RUNNING ABOUT 20-25 DEGS BELOW NORMAL! NORMAL HIGH TODAY IS 70-75. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... HIGHLIGHTS... * MAINLY DRY WITH BELOW NORMAL TEMPS THU * A FEW SHOWERS POSSIBLE FRI INTO SAT AS A COLD FRONT APPROACHES * DRY AND SEASONABLE SUN THEN THREAT OF SHOWERS RETURNS MON OVERVIEW AND MODEL PREFERENCES... ALTHOUGH THE 02/00Z MODEL GUIDANCE SUITE IS IN RELATIVELY GOOD AGREEMENT THROUGH THE WEEKEND...AT LEAST REGARDING THE UPPER LVL FLOW PATTERN...THERE SOME SPATIAL/TEMPORAL DIFFERENCES IN THE SFC/LOW LVL FEATURES WHICH WILL ULTIMATELY DRIVE SENSIBLE WX FRI- SUN. SPLIT FLOW REGIME ACROSS NA WITH THE WEAKER SRN STREAM DOMINATING INITIALLY. SLOW MOVING APPALACHIAN TROF LIES ON THE ERN EDGE OF MODERATE BLOCK THROUGH THE S CENTRAL CONUS. THIS BLOCK WILL FAVOR RIDGING ACROSS NEW ENGLAND THROUGH THE LATTER HALF OF THE WEEK. BY THE WEEKEND HOWEVER...THERE IS SOME SUGGESTION THAT A NRN STREAM WAVE MAY PHASE SOMEWHAT WITH THE WEAKER SRN STREAM TROF IN THE MID ATLANTIC. THIS IS WHERE CERTAINTY IN THE FORECAST DECREASES SOMEWHAT. MODELS ARE CONTINUING TO INDICATE A WEAK LOW LVL BAROCLINIC WAVE MOVING OFF THE MID ATLANTIC ON FRI...WHICH MAY ALLOW FOR THE FORCING OF SOME SHOWERS ACROSS THE REGION AS MOISTURE INCREASES. MODELS NOW INDICATING A LITTLE MORE QPF FRI THAN PREVIOUS RUNS SO WILL NEED TO CONTINUE TO MONITOR THIS TREND. THIS ALSO LEADS TO TIMING DIFFERENCES OF A COLD FROPA FOR SAT...BUT IN EITHER CASE...RISK FOR SHOWERS REMAINS UNTIL REMNANTS OF THE CENTRAL CONUS BLOCK ENHANCE RIDGING ONCE AGAIN ACROSS THE NE. DETAILS... WED NIGHT INTO THU... HIGH PRES REMAINS IN CONTROL BUT WILL BEGIN TO SLIP BACK TO THE E THROUGH THE PERIOD. EXPECTING MAINLY DRY WX...AND EVEN THOUGH SOME MODELS SUGGEST QPF LATE THU AND THU NIGHT...FEEL THE FORECAST IS MORE DRY THAN WET GIVEN BUFKIT DATA FROM THE SAME MODEL SHOWS DRY SUBSIDENCE INVERSION REMAINS IN PLACE. MODEL QPF MAY BE AN INDICATION OF THE STRUGGLE WITH THE WEAK BAROCLINIC WAVE DEVELOPMENT OFFSHORE LATE IN THE PERIOD. TEMPS ARE LIKELY TO REMAIN NEAR OR EVEN POSSIBLY SLIGHTLY BELOW SEASONAL NORMALS AS H85 TEMPS ARE GENERALLY BELOW +10C. FRI AND SAT... GRADUALLY DEEPENING NRN STREAM SHORTWAVE COMBINES WITH LEFTOVER ENERGY FROM AN APPALACHIAN WAVE TO INCREASE PRECIPITATION CHANCES THROUGH THIS PERIOD THANKS TO TWO PRIMARY MECHANISMS. 1. A WEAK OFFSHORE LOW PRES SYSTEM MOVING WELL S OF THE REGION...BUT FORCING AN INVERTED TROF ACROSS SRN NEW ENGLAND AND 2. A COLD FRONTAL PASSAGE. PWATS PEAK LATE FRI AND FRI NIGHT...JUST ABOVE 1.50 INCHES /ABOUT 1.5 STD DEVIATIONS ABOVE NORMAL. THEREFORE...EXPECT A PERIOD WITH PRECIPITATION CHANCES. NOT A WASHOUT HERE AS FORCING IS RELATIVELY WEAK...AND THE COLUMN SOMEWHAT STABLE. SLIGHT-CHANCE POPS STILL LOOK REASONABLE. TEMPERATURES REMAIN NEAR SEASONAL NORMALS IN SPITE OF RETURN FLOW. MAINLY DUE TO THE EXPECTATION OF MORE CLOUD COVER THAN THU. SUN... RETURN TO BRIEF RIDING AS REMNANTS OF THE CENTRAL CONUS BLOCK MOVES ACROSS THE AREA BEHIND THE COLD FRONT WHICH IS LIKELY TO STALL OFFSHORE. TEMPS MAINLY JUST BELOW NORMAL DUE TO H85 TEMPS PROGGED BELOW +10C. EARLY NEXT WEEK... ANOTHER POSSIBLE THREAT FOR RAINFALL AS A MORE ROBUST NRN STREAM SHORTWAVE IS PROGGED TO DIVE S FROM QUEBEC/ONTARIO. FINAL OUTCOMES ARE LIKELY TO BE DEPENDENT ON TIMING/INSTABILITY BUT GIVEN THERE IS A CONNECTION TO GULF MOISTURE WITH THIS DEEPER WAVE...ENSEMBLES SUPPORT PWATS APPROACHING 2 STD DEVIATIONS ABOVE NORMAL. && .AVIATION /13Z TUESDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. TODAY...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN EXACT TIMING. IFR/MVFR CONDITIONS DOMINATE IN MIX OF RAIN/FOG/LOW CIGS THROUGH MOST OF THE MORNING. HOWEVER...EXPECT SOME IMPROVEMENT TO MAINLY MVFR/LOW VFR BEGINNING AROUND 16Z. SOME MVFR LINGERS ESPECIALLY SE OF A BDL-ORH-BVY LINE INTO THE EVENING. NW OF THIS LINE IMPROVEMENT TO VFR EXPECTED LATE IN THE DAY. WINDS TAKE ON A MORE NORTHERLY DIRECTION. TONIGHT...MODERATE CONFIDENCE. GRADUAL IMPROVEMENT EXPECTED WITH RAIN ENDING EVERYWHERE. HOWEVER...SOME MVFR CONDITIONS POSSIBLE IN LINGERING LOW CIGS AND FOG. LOW CONFIDENCE ON EXACTLY HOW WIDESPREAD THIS IS. WEDNESDAY...VFR. NORTH WINDS TREND NORTHEAST BY AFTERNOON ESPECIALLY ALONG THE COAST. KBOS TERMINAL...HIGH CONFIDENCE IN OVERALL TAF TRENDS...LOWER CONFIDENCE IN EXACT TIMING. ALSO LOW CONFIDENCE IN LOW CIGS/FOG OVERNIGHT TONIGHT. KBDL TERMINAL...HIGH CONFIDENCE IN CIGS. MODERATE CONFIDENCE IN VSBYS. OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY... THU INTO FRI...HIGH CONFIDENCE. MAINLY VFR. ALTHOUGH OCCASIONAL MVFR/IFR POSSIBLE IN FOG/SHRA FRI NIGHT. THIS WILL BE HIT-OR-MISS. WINDS MAINLY SOUTHERLY. SAT...HIGH CONFIDENCE. MAINLY VFR WITH SOME SHOWERS. WINDS SHIFT FROM S TO NNW. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY NIGHT/...MODERATE TO HIGH CONFIDENCE. TODAY...NORTHEAST WINDS AROUND 15 KNOTS SUSTAINED AND WITH GUSTS UP TO 25 KNOTS. THIS SHOULD MAINTAIN 5-6 FOOT SEAS ON MASS BAY AND THE ADJACENT OUTER WATERS...WITH SLIGHTLY LOWER SEAS WEST AND SOUTH. SHOWERS WILL CONTINUE TO MOVE NORTHEAST UP THE COAST ACROSS THE WATERS...WITH SOME LOCALLY HEAVY DOWNPOURS POSSIBLE. LOW RISK OF ISOLATED THUNDER. TONIGHT...HIGH PRESSURE BUILDS FROM THE NORTH. WINDS SHOULD DIMINISH AND BECOME NORTHERLY. SEAS MAY LINGER AROUND 5 FEET ON THE OUTER WATERS. WEDNESDAY...WINDS SHIFT TO EAST-NORTHEAST BUT WITH SPEEDS UNDER 15 KNOTS. SEAS WILL ALSO DIMINISH TO 4 FEET OR LOWER. OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY... THU INTO EARLY FRI...HIGH CONFIDENCE. WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT THRESHOLDS AS HIGH PRES MOVES OVER THE WATERS. LATE FRI INTO SAT...MODERATE CONFIDENCE. LOW PRES PASSING WELL TO THE S AND AN APPROACHING COLD FRONT WILL LEAD TO INCREASED CHANCES FOR PRECIP/FOG OVER THE WATERS AT TIMES. S WINDS WILL GIVE WAY TO NW WINDS LATE SAT. SOME WIND GUSTS MAY APPROACH 20-25 KT MAINLY SAT. SEAS HOWEVER...SHOULD GENERALLY REMAIN BELOW THE 5 FT MARK. && .CLIMATE...
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RECORD LOW MAX TEMPS FOR TODAY... BOS...50...1946 BDL...50...1907 (RECORD FOR THE MONTH) PVD...47...1907 (RECORD FOR THE MONTH) ORH...47...1946 (RECORD FOR THE MONTH)
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ230>235-237-250-251-255-256. SMALL CRAFT ADVISORY UNTIL 10 AM EDT WEDNESDAY FOR ANZ254.
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&& $$ SYNOPSIS...WTB/DOODY NEAR TERM...WTB/NOCERA/DOODY SHORT TERM...WTB LONG TERM...DOODY AVIATION...WTB/DOODY MARINE...WTB/DOODY CLIMATE...KB

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