Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 250715 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 315 AM EDT WED MAR 25 2015 .SYNOPSIS... HIGH PRESSURE MOVES OFFSHORE TODAY ALLOWING MORE SEASONABLE AIR TO RETURN TO NEW ENGLAND. A WARM FRONT MOVES ACROSS NEW ENGLAND TONIGHT BRINGING A PERIOD OF RAIN...FOLLOWED BY CLOUDS/DRIZZLE/FOG. ANOTHER AREA OF RAIN MOVES THROUGH ON THURSDAY. A COLD FRONT SWEEPS ACROSS THE REGION THURSDAY NIGHT WITH SHOWERS. A SECOND COLD FRONT WILL BRING COLDER TEMPERATURES LATER FRIDAY INTO THIS WEEKEND. ANOTHER FAST MOVING FRONT WILL PUSH ACROSS THE REGION SUNDAY NIGHT INTO MONDAY. && .NEAR TERM /THROUGH TODAY/... THROUGH 8 AM... HIGH PRESSURE CENTERED OVER NEW ENGLAND WITH CLEAR SKIES ACROSS THE REGION. PER SATELLITE THE NEAREST CIRRUS WAS LOCATED IN WESTERN NY/WESTERN PA AT 2 AM. THIS WILL MOVE EAST AT A PACE THAT WILL BRING IT INTO SOUTHERN NEW ENGLAND AROUND SUNRISE. FAIR SKIES AND LIGHT WINDS WILL ALLOW COOLING TEMPERATURES THROUGH SUNRISE WITH DEW POINTS IN THE TEENS AND LOWER 20S ALLOWING AN EXPECTED RANGE OF MORNING LOWS IN THE MID TEENS TO MID 20S. TODAY... INCREASING HIGH CLOUDS MORNING AND MIDDAY BUT PLENTY OF SUN THROUGH THAT SKY COVER. SO EXPECT TEMPERATURES TO RECOVER FROM THE CHILLY START. TEMPS ALOFT THROUGH 18Z WOULD SUPPORT MAX SFC TEMPS IN THE 40S. SOUTHERLY LOW LEVEL JET REMAINS TO OUR WEST AT 18Z BUT SHIFTS INTO SOUTHERN NEW ENGLAND BY 00Z. SO EVEN WITH INCREASING CLOUDS THE WEATHER SHOULD REMAIN DRY THROUGH ALMOST ALL OF THE DAY. COULD BE A CHANCE OF INITIAL LIGHT SHOWERS IN WESTERN MASS/CT AROUND 5 PM. && .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/... TONIGHT... PRIME ZONE OF WARM ADVECTION LIFT MOVES THROUGH DURING THE FIRST HALF OF THE NIGHT AND THEN MOVE EAST OF US AFTER MIDNIGHT. THE WARM ADVECTION THEN REACHES THE SURFACE AND SHOULD PROVIDE FOR WARMING TEMPS OVERNIGHT...A DECIDED NON-DIURNAL TREND. WE HAVE ADJUSTED HOURLY TEMPS TO REFLECT THIS. THE WARM ADVECTION...WITH DEW POINTS RISING ABOVE FREEZING TO AROUND 40...SHOULD BRING AREAS OF FOG AS IT RIDES OVER THE SNOWPACK. WITH NEARSHORE WATER TEMPS IN THE 30S...THE HIGHER DEW POINT AIR MOVING ASHORE ALONG THE SOUTH COAST MAY ALSO BE SUFFICIENTLY CHILLED TO CREATE AREAS OF FOG. THURSDAY... COLD FRONT STARTS THE DAY EXTENDING FROM NORTHERN VERMONT TO THE OHIO VALLEY. THIS AXIS HAS A NORMAL COMPONENT TO THE UPPER FLOW BUT IS NOT FAR FROM BEING PARALLEL. THE FRONT WILL BE SUPPORTED BY A 155 KNOT UPPER JET OVER THE GREAT LAKES WITH RIGHT ENTRANCE REGION OVER ILLINOIS/INDIANA. SURPRISE...A WAVE OF LOW PRESSURE DEEPENS IN THIS LOCATION AS IT MOVES UP THE FRONT. THIS WILL BRING A STRONG LOW LEVEL SOUTHWEST JET UP TOWARD NEW ENGLAND WHICH SHOULD GENERATE ANOTHER PERIOD OF RAIN OVER OUR AREA BY AFTERNOON. ACTUALLY IT/S A TOUGH CALL FOR RAIN VS SHOWERS...THE PATTERN LOOKS STRATIFORM BUT TAKES PLACE AHEAD OF AN ADVANCING COLD FRONT. BASED ON THE LOW LEVEL JET AND RESULTING LIFT WE WILL GO STRATIFORM AT THIS TIME...BUT COULD BE MORE LIKE PERIOD OF RAIN RATHER THAN A LONG SOAKING RAIN. STABILITY PARAMETERS LOOK FAVORABLE FOR CONVECTION WITH TOTALS IN THE LOWER 50S AND TQ 17 TO 18. THE COOLING BY THE SNOWPACK MAY MAINTAIN A STABLE LAYER AT THE SURFACE...BUT ELEVATED INSTABILITY MAY BE ENOUGH TO SET OF ISOLATED OR WIDELY SCATTERED THUNDER DURING THE AFTERNOON AND EVENING. THE STRONG WARM ADVECTION WILL CONTINUE TO BRING RELATIVELY HIGH DEW POINT AIR...IN THE 40S...ACROSS THE REGION. THIS WILL AID BOTH FOG FORMATION AND SNOWMELT. PRECIPITABLE WATER VALUES CLIMB TO AROUND 1 INCH TO 1.5 INCHES...WHICH IS ABOUT 2 SD ABOVE NORMAL. THIS SUGGESTS POTENTIAL FOR OCCASIONAL HEAVY DOWNPOURS. 950 MB TEMPS 8-10C BROUGHT TO THE SURFACE ISOTHEMALLY WOULD START TEMPERATURES AT 45-50. ALLOW SOME MINIMAL WARMING DURING THE MORNING AND POTENTIAL IS THERE FOR MAX TEMPS 50-55. THURSDAY NIGHT... THE SURFACE LOW PASSES TO OUR NORTH AND THEN SWINGS THE COLD FRONT THROUGH SOUTHERN NEW ENGLAND DURING THE NIGHT. LOW CONFIDENCE ON EXACT TIMING...BUT THE WIND SHIFT SHOULD COINCIDE WITH DIMINISHING SHOWERS. WE STAYED CLOSE TO BLENDED MODEL GUIDENCE FOR MIN TEMPS LATE THURSDAY NIGHT. && .LONG TERM /FRIDAY THROUGH TUESDAY/... HIGHLIGHTS... * PERIODS OF HEAVY RAINFALL LATE THURSDAY INTO EARLY FRI AS LOW PRESSURE MOVES NORTH OF THE REGION * BELOW AVERAGE TEMPS FOR THE WEEKEND * WEAK DISTURBANCE POSSIBLE ON MONDAY OVERVIEW AND MODEL PREFERENCES... 12Z MODEL GUIDANCE KEEPS THE OVERALL UPPER LEVEL PATTERN THAT HAS BEEN IN PLACE FOR THE LAST COUPLE OF MONTHS /AT LEAST/ WITH LONG WAVE RIDGING CONTINUING ACROSS THE WESTERN U.S. AND DEEP LONG WAVE TROUGH ACROSS THE EAST DURING A GOOD PORTION OF THE LONG TERM PERIOD. STILL TIMING AND TRACK QUESTIONS WITH INDIVIDUAL SHORT WAVES MOVING ALONG IN THIS OVERALL UPPER FLOW...THOUGH MODELS AND ENSEMBLES STARTING TO SHOW POSSIBLE BREAKDOWN OF THE UPPER STEERING FLOW TOWARD THE END OF THE PERIOD. EXPECT ANOTHER SHOT OF SOMEWHAT MODIFIED ARCTIC AIR MOVING IN LATER FRIDAY INTO THIS WEEKEND. SOME QUESTION AS TO ANOTHER PERIOD OF LIGHT PRECIP FOR S COASTAL AREAS AS SHORT WAVE MOVES S OF NEW ENGLAND SATURDAY. NW FLOW ALOFT TAKES OVER LATE THIS WEEKEND AS LONG WAVE TROUGH MOVES OFFSHORE. FAST MOVING H5 SHORT WAVE AND ASSOCIATED COLD FRONT CROSSES THE REGION AROUND SUN NIGHT/MON TIMEFRAME. DETAILS... FRIDAY...A SECOND COLD FRONT HOLDS ACROSS UPSTATE NEW YORK UNTIL LATER IN THE DAY AS ANOTHER SHORT WAVE ROTATES AROUND BASE OF LONG WAVE TROUGH. SO... TEMPS LOOK TO REBOUND TO THE MID 40S TO AROUND 50...RUNNING CLOSE TO OR A FEW DEGREES BELOW SEASONAL NORMS. LEFTOVER PRECIP WILL PUSH OFFSHORE BY MIDDAY THOUGH CLOUDS WILL LINGER INTO THE AFTERNOON. THE SECOND FRONT PUSHES ACROSS AROUND THAT TIME...SO WILL SEE TEMPS DROP WITH NW WINDS AROUND 10 KT OR SO. LATE FRIDAY THROUGH SUNDAY...MODERATE CONFIDENCE. DEEP LONG WAVE TROUGH IN PLACE JUST W OF THE REGION. MOST OF THE 12Z SHORT RANGE MODELS DID DEPICT ANOTHER SHORT WAVE ROTATING OUT OF THE EASTERN GREAT LAKES FRI NIGHT INTO SATURDAY...PASSING JUST S OF NEW ENGLAND. GOOD FORCING AND DECENT MOISTURE ASSOCIATED WITH THIS FEATURE...WITH THE GFS BEING MOST BULLISH AND THE NAM NOT TOO FAR BEHIND. STILL SOME UNCERTAINTY AS TO HOW CLOSE THIS SHORT WAVE WILL BE AS IT PASSES SAT MORNING. PUT MENTION IN FOR SLIGHT CHANCE POPS ACROSS NE CT/RI/SE MA...WHICH COULD START AS A PERIOD OF SNOW SHOWERS BEFORE TEMPS RISE ENOUGH TO CHANGE TO RAIN. WILL NEED TO MONITOR THIS FEATURE FOR POSSIBLE DEVELOPMENT. AT THIS POINT...EXPECT THIS WAVE TO PUSH OFFSHORE SAT AFTERNOON... SO SHOULD SEE DRY BUT CHILLY CONDITIONS. LOWS SAT NIGHT WILL BE IN THE 20S WELL INLAND TO THE LOWER 30S AT THE COAST. WILL BE A DRY BUT CHILLY DAY ON SUNDAY SUNDAY NIGHT AND MONDAY...LOW TO MODERATE CONFIDENCE. H5 SHORT WAVE IN THE UPPER LEVEL NW FLOW WILL WORK SE OUT OF THE GREAT LAKES. ONCE AGAIN...GFS IS RATHER BULLISH IN BRINGING DECENT QPF TO THE REGION AS SURFACE REFLECTION WORKS OFFSHORE. THIS MODEL EVEN TRIES TO REDEVELOP THE LOW OFFSHORE...THOUGH GGEM AND ECMWF HOLD OFF ON THIS AND KEEP THE LOW FURTHER N. EXPECT LIGHT PRECIP AT THIS POINT AS THE LOW AND COLD FRONT PASS DURING MONDAY. CARRIED CHANCE POPS LATE SUN NIGHT THROUGH MOST OF MONDAY...THEN SHOULD CLEAR OFFSHORE. TUESDAY...LOW TO MODERATE CONFIDENCE. DEPENDING UPON THE SUN NIGHT/MON SYSTEM...AT THIS POINT LOOKS LIKE CONDITIONS SHOULD BE MAINLY DRY AS HIGH PRES PASSES S OF THE REGION. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. HIGH CONFIDENCE THROUGH WEDNESDAY...THEN SOME UNCERTAINTY ON EXACT TIMING OF LOWER CIGS/VSBYS WITH RAIN LATE WED INTO WED EVENING. THROUGH 12Z/8 AM...HIGH CONFIDENCE. VFR CLR. LIGHT/VRBL OR CALM WINDS. TODAY...VFR. CLOUDS LOWER AND THICKEN DURING THE AFTERNOON/EVENING. MVFR CIGS/VSBYS DUE TO RAIN MAY ENTER THE CT RIVER VALLEY BETWEEN 21Z AND 00Z THIS EVENING. TONIGHT...CONDITIONS LOWERING TO MVFR WITH AREAS OF IFR DUE TO LOW CIGS/RAIN/FOG. RAIN TAPERS OFF AFTER MIDNIGHT BUT IFR/LIFR DUE TO LOW CIGS/FOG/DRIZZLE THROUGH SUNRISE. THURSDAY...ANOTHER AREA OF RAIN MOVES IN FROM THE SOUTHWEST. MIXED MVFR/IFR CIGS/VSBYS IN RAIN AND FOG. LOCALLY HEAVY DOWNPOURS POSSIBLE THURSDAY NIGHT AS A COLD FRONT SWINGS THROUGH. LOW CONFIDENCE FOR ISOLATED THUNDERSTORMS LEADING THE FRONT THURSDAY EVENING/NIGHT. BEST CHANCE FOR THUNDER WOULD BE ACROSS RI AND SOUTHEAST MASS. KBOS TAF...HIGH CONFIDENCE THRU 00Z TODAY THEN SOME UNCERTAINTY ON EXACT TIMING OF LOWERING CONDITIONS. KBDL TAF...HIGH CONFIDENCE THRU 21Z TODAY THEN SOME UNCERTAINTY ON EXACT TIMING OF LOWERING CONDITIONS. OUTLOOK...THURSDAY THROUGH SUNDAY...MODERATE TO HIGH CONFIDENCE. FRIDAY...MVFR-IFR CIGS/VSBYS IN SHOWERS AND PATCHY FOG. MAY SEE LOCAL -SHSN ACROSS N AND W MA 12Z-14Z. PRECIP TAPERS OFF FROM NW- SE DURING FRIDAY. FRIDAY NIGHT AND SATURDAY...MAINLY VFR CONDITIONS. MAY SEE LOCAL MVFR CIGS/VSBYS ACROSS NE CT/RI/SE MA LATE FRI NIGHT AND SAT IN RAIN AND/OR SNOW SHOWERS. SATURDAY NIGHT AND SUNDAY...VFR CONDITIONS LIKELY. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. HIGH CONFIDENCE TODAY THEN MODERATE CONFIDENCE TONIGHT AND THURSDAY. TODAY...LIGHT WINDS BECOME SOUTH THIS AFTERNOON. WINDS AND SEAS REMAIN BELOW SMALL CRAFT THRESHOLDS. CHANCE OF LIGHT RAIN TOWARD EVENING. TONIGHT...SOUTH TO SOUTHWEST WINDS WILL INCREASE TO 20-25 KNOTS. THIS WILL BUILD SEAS TO 5 FEET ON THE OUTER WATERS AND 3-4 FEET CLOSER TO SHORE. THE SOUTH WIND WILL TRANSPORT INCREASING HUMIDITY WITH DEW POINTS AT LEAST IN THE 40S. AS THIS MOVES OVER 38 DEGREE WATER IT MAY GENERATE LOW VSBYS IN FOG ACROSS THE WATERS...ESPECIALLY SOUTH OF NEW ENGLAND. THURSDAY AND THURSDAY NIGHT...INCREASING SOUTHWEST WINDS WITH FREQUENT GUSTS 25-30 KNOTS. THIS WILL BUILD SEAS WITH 5-10 FOOT HEIGHTS EXPECTED ON THE EXPOSED WATERS INCLUDING RI SOUND. HEIGHTS ON THE OUTER WATERS COULD REACH 11 TO 13 FEET AT TIMES. VSBYS WILL REMAIN LOW IN RAIN AND FOG. A COLD FRONT APPROACHES THE WATERS OVERNIGHT THURSDAY NIGHT. OUTLOOK...FRIDAY THROUGH SUNDAY... MODERATE TO HIGH CONFIDENCE FRIDAY. MODERATE CONFIDENCE FRIDAY NIGHT INTO SUNDAY. FRIDAY...WINDS SHIFT TO NW DURING FRI. SEAS UP TO 5-7 FT THU WILL BUILD UP TO 11 TO 13 FT WELL OFFSHORE ON FRI. FRI NIGHT-SUNDAY...N-NW WINDS MAY GUST CLOSE TO 25 KT...MAINLY LATE SAT INTO SUNDAY. SEA REMAIN AOA 5 FT MAINLY OVER THE OUTER WATERS. && .HYDROLOGY... CONTINUE TO NOTE GOOD AMOUNT OF RAINFALL WILL MOVE ACROSS THE REGION...AS WELL AS TEMPERATURES RISING TO THE UPPER 40S TO MID 50S ALONG WITH INCREASING DEWPTS /AT LEAST TO THE 40S/ THURSDAY INTO FRIDAY. THIS WILL COMBINE TO CAUSE SIGNIFICANT SNOW MELT ACROSS THE REGION. EXPECT RAINFALL AMOUNTS TO RANGE FROM 0.5 TO 1 INCH ACROSS THE REGION...POSSIBLY 1.25 IN SPOTS. HIGHEST VALUES WILL BE ACROSS NORTHERN AND WESTERN MASS AND CT. HOWEVER...WITH MILDER TEMPS...WILL SEE A BIG WATER RELEASE WITH THE SNOW TO WATER EQUIVALENT /SWE/ ON ORDER OF 2-5 INCHES. MAY ALSO SEE SOME HEAVIER DOWNPOURS OVERNIGHT THU INTO FRI MORNING ESPECIALLY IF ANY CONVECTION DEVELOPS. COMBINING THE RAPID SNOW MELT WITH THE UPCOMING QPF...MAY SEE 1.5 TO 3 INCHES OF WATER FLOWING INTO AREA RIVERS AND STREAMS. SEVERAL OF THE MAIN STEM RIVER LEVELS MAY APPROACH ACTION STAGE DURING FRIDAY...WITH A COUPLE POSSIBLY APPROACHING MINOR FLOOD STAGE. CURRENT FORECASTS ISSUED BY THE NORTHEAST RIVER FORECAST CENTER HAVE THE DETAILS. CONTINUE TO MONITOR FORECAST UPDATES FOR MORE DETAILS ON THIS EVENT. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB/EVT SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/EVT MARINE...WTB/EVT HYDROLOGY...

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